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1

Liquid-phase hydrogenation of citral over Pt\\/SiOâ catalysts. 1. Temperature effects on activity and selectivity  

Microsoft Academic Search

Liquid-phase hydrogenation of citral (3,7-dimethyl-2,6-octadienal) over Pt\\/SiOâ catalysts was studied in the temperature and pressure ranges 298--423 K and 7--21 atm, respectively. The reaction kinetics were shown to be free of artifacts arising from transport limitations and poisoning effects. The reaction rate in hexane at the solvent exhibited an activity minimum at 373 K. The initial turnover frequency for citral

U. K. Singh; M. A. Vannice

2000-01-01

2

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

3

Laser-activated gold catalysts for liquid-phase growth of cadmium selenide nanowires.  

PubMed

A laser-activated-catalyst (LAC) technique was developed to grow CdSe nanowires in liquid medium at room temperature. The gold catalysts dispersed in the precursor solution were activated by a pulsed laser so as to decompose the precursor and catalyse the nanowire growth simultaneously. The LAC technique can achieve accurate positioning of nanowires, which is beneficial for device fabrication. PMID:25554220

Huang, C; Mao, J; Chen, X M; Yang, J; Du, X W

2015-02-01

4

Kinetic studies of the liquid-phase adsorption of a reactive dye onto activated lignite  

SciTech Connect

The kinetics of batch adsorption of a commercial reactive dye onto activated lignite has been investigated at temperatures of 26, 40, and 55{sup o}C, using aqueous solutions with initial dye concentrations in the range of 15-60 mg/L. An empirical single parameter relationship of the adsorbent loading versus the square root of contact time was proposed, which was determined to provide a very good description of the batch adsorption transients up to equilibrium. The data were also examined by means of the Elovich equation. The effect of the temperature and the initial dye concentration on the adsorption kinetics was analyzed, and the results were discussed by considering that intraparticle diffusion is the dominant mechanism.

Petrolekas, P.D.; Maggenakis, G. [Democritus University of Thrace, Xanthi (Greece)

2007-02-14

5

Relationship between surface hydroxyl groups and liquid-phase photocatalytic activity of titanium dioxide.  

PubMed

Both theories and experiments show that surface hydroxyl radicals (OH) are the most important intermediate species in the photocatalytic process. As a source of OH, surface hydroxyl (OH) groups play an important role in its generation. In this paper, the OH groups were divided into surface acidic hydroxyl (OH(a)) and surface basic hydroxyl (OH(b)) groups. From the detection by a method of surface acid-base, ion-exchange reactions, the total surface density of OH groups was about 9.58×10(-5)molm(-2). The results measured by Fourier transform infrared spectroscopy, (1)H magnetic-angle spinning NMR and electron spin resonance techniques demonstrated that the role of OH(a) groups was greater than that of OH(b) groups on the generation of OH radicals. By degradation of methyl orange, rhodamine B and p-chlorophenol, the photocatalytic activities of the catalysts were directly influenced by the amount of OH groups. PMID:25585286

Li, Wenjuan; Du, Dandan; Yan, Tingjiang; Kong, Desheng; You, Jinmao; Li, Danzhen

2015-04-15

6

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

7

Palladium supported on filamentous active carbon as effective catalyst for liquid-phase hydrogenation of 2-butyne-1,4-diol to 2-butene-1,4-diol  

Microsoft Academic Search

Structured palladium catalysts suitable for three-phase reactions have been developed based on woven fabrics of active carbon fibres (ACF) as the catalytic supports. The Pd\\/ACF were tested in liquid-phase hydrogenation of 2-butyne-1,4-diol showing a selectivity towards 2-butene-1,4-diol up to 97% at conversions up to 80%. The catalyst multiple reuse with stable activity\\/selectivity in a batch reactor was also demonstrated. The

E Joannet; C Horny; L Kiwi-Minsker; A Renken

2002-01-01

8

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

Microsoft Academic Search

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

M. Mazar Atabaki

2010-01-01

9

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

SciTech Connect

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

Xiang-Dong Peng

2002-05-01

10

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

NASA Astrophysics Data System (ADS)

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

Atabaki, M. Mazar

2010-11-01

11

Influence of the reaction conditions and catalytic properties on the liquid-phase hydrodechlorination of chlorobenzene over palladium-supported catalysts: Activity and deactivation  

SciTech Connect

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, a better resistance to chlorine is observed when the size of the metallic particle increases. The supports tested, viz. SiO{sub 2}/AlPO{sub 4}, ZrO{sub 2}, and MgO, significantly affected catalyst deactivation. Thus, supports that can capture chloride species (e.g., ZrO{sub 2}) allow the reaction to finalize within relatively short times. The reaction appeared to be structure-sensitive in regard to the initial activity. Changing dispersion from 54 to 7% was accompanied by an increase in catalytic activity by a factor of 20.

Aramendia, M.A.; Borau, V.; Garcia, I.M.; Jimenez, C.; Lafont, F.; Marinas, A.; Marinas, J.M.; Urbano, F.J.

1999-10-25

12

Liquid Phase Sintering  

NASA Technical Reports Server (NTRS)

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

2004-01-01

13

Liquid-phase electroepitaxy - Dopant segregation  

NASA Technical Reports Server (NTRS)

A theoretical model is presented which accounts for the dopant segregation in liquid-phase electroepitaxy in terms of dopant transport in the liquid phase (by electromigration and diffusion), the growth velocity, and the Peltier effect at the substrate-solution interface. The contribution of dopant electromigration to the magnitude of the effective segregation coefficient is dominant in the absence of convection; the contribution of the Peltier effect becomes significant only in the presence of pronounced convection. Quantitative expressions which relate the segregation coefficient to the growth parameters also permit the determination of the diffusion constant and electromigration mobility of the dopant in the liquid phase. The model was found to be in good agreement with the measured segregation characteristics of Sn in the electroepitaxial growth of GaAs from Ga-As solutions. For Sn in Ga-As solution at 900 C the diffusion constant was found to be 4 x 10 to the -5 sq cm/s and the electromigration velocity (toward the substrate with a positive polarity 2 x 10 to the -5 cm/s current density of 10 A/sq cm.

Lagowski, J.; Jastrzebski, L.; Gatos, H. C.

1980-01-01

14

Liquid-phase growth of platinum nanoparticles on molybdenum trioxide nanosheets: an enhanced catalyst with intrinsic peroxidase-like catalytic activity  

NASA Astrophysics Data System (ADS)

A facile method for the synthesis of metal nanostructure-decorated two-dimensional (2D) semiconductor nanosheets was developed. The solution-processable molybdenum trioxide (MoO3) nanosheet was used as a template for direct liquid-phase growth of platinum nanoparticles (Pt NPs) under ambient conditions. Results show that the Pt NPs with sizes of 1-3 nm were uniformly grown on the MoO3 surface. Importantly, the Pt-MoO3 hybrid nanomaterial exhibits an enhanced peroxidase-like catalytic activity compared to the MoO3 nanosheet, Pt NPs, and their physical mixture under the same conditions. As a proof-of-concept application, the Pt-MoO3 hybrid nanomaterial was used as a high-efficiency peroxidase-mimic for ultrasensitive colorimetric detection of glucose in serum samples. This work provides a promising strategy for design and development of biomimetic catalysts by smart assembly of different dimensional nanomaterials.A facile method for the synthesis of metal nanostructure-decorated two-dimensional (2D) semiconductor nanosheets was developed. The solution-processable molybdenum trioxide (MoO3) nanosheet was used as a template for direct liquid-phase growth of platinum nanoparticles (Pt NPs) under ambient conditions. Results show that the Pt NPs with sizes of 1-3 nm were uniformly grown on the MoO3 surface. Importantly, the Pt-MoO3 hybrid nanomaterial exhibits an enhanced peroxidase-like catalytic activity compared to the MoO3 nanosheet, Pt NPs, and their physical mixture under the same conditions. As a proof-of-concept application, the Pt-MoO3 hybrid nanomaterial was used as a high-efficiency peroxidase-mimic for ultrasensitive colorimetric detection of glucose in serum samples. This work provides a promising strategy for design and development of biomimetic catalysts by smart assembly of different dimensional nanomaterials. Electronic supplementary information (ESI) available: Experimental details, Fig. S1-S9, and Tables S1 and S2 as mentioned in the text. See DOI: 10.1039/c4nr04115a

Wang, Yixian; Zhang, Xiao; Luo, Zhimin; Huang, Xiao; Tan, Chaoliang; Li, Hai; Zheng, Bing; Li, Bing; Huang, Ying; Yang, Jian; Zong, Yun; Ying, Yibin; Zhang, Hua

2014-10-01

15

Effects of phosphorus deficiency on rumen microbial activity associated with the solid and liquid phases of a fermentor  

E-print Network

Effects of phosphorus deficiency on rumen microbial activity associated with the solid and liquid in microbial protein synthesis in both phases. Microbial yield declined by about 5 points (g of N/kg OMF) in P countries (Smith, 1984) or when diets high in low P-containing by-products (pulp, molasses, treated straw

Paris-Sud XI, Université de

16

Liquid-phase hydrogenation of citral over Pt/SiO{sub 2} catalysts. 1. Temperature effects on activity and selectivity  

SciTech Connect

Liquid-phase hydrogenation of citral (3,7-dimethyl-2,6-octadienal) over Pt/SiO{sub 2} catalysts was studied in the temperature and pressure ranges 298--423 K and 7--21 atm, respectively. The reaction kinetics were shown to be free of artifacts arising from transport limitations and poisoning effects. The reaction rate in hexane at the solvent exhibited an activity minimum at 373 K. The initial turnover frequency for citral disappearance over 1.44% Pt/SiO{sub 2} catalyst at 20 atm H{sub 2} pressure decreased from 0.19 s{sup {minus}1} at 298 K to 0.02 s{sup {minus}1} at 373 K, but exhibited normal Arrhenius behavior between 373 and 423 K with an activation energy of 7 kcal/mol. Reaction at 298 K produced substantial deactivation, with the rate decreasing by more than an order of magnitude during the first 4 h of reaction; however, reaction at temperatures greater than 373 K exhibited negligible deactivation and a constant rate up to citral conversions greater than 70%. These unusual temperature effects were modeled using Langmuir-Hinshelwood kinetics invoking dissociative adsorption of hydrogen, competitive adsorption between hydrogen and the organic compounds, and addition of the second hydrogen atom to each reactant as the rate-determining step. Decomposition of the unsaturated alcohol (either geraniol or nerol) was proposed to occur concurrently with the hydrogenation steps to yield adsorbed CO and carbonaceous species which cause the deactivation, but at higher temperatures these species could be removed from the Pt surface by desorption or rapid hydrogenation, respectively. The activity minimum observed in the present study is attributed to the relative rates of the alcohol decomposition reaction and CO desorption, with the decomposition reaction having an activation barrier lower than that for CO desorption.

Singh, U.K.; Vannice, M.A.

2000-04-01

17

Depositing spacing layers on magnetic film with liquid phase epitaxy  

NASA Technical Reports Server (NTRS)

Liquid phase epitaxy spacing layer is compatible with systems which are hard-bubble proofed by use of second magnetic garnet film as capping layer. Composite is superior in that: circuit fabrication time is reduced; adherence is superior; visibility is better; and, good match of thermal expansion coefficients is provided.

Moody, J. W.; Shaw, R. W.; Sanfort, R. M.

1975-01-01

18

Liquid-Phase Combinatorial Synthesis  

Microsoft Academic Search

A concept termed liquid-phase combinatorial synthesis (LPCS) is described. The central feature of this methodology is that it combines the advantages that classic organic synthesis in solution offers with those that solid-phase synthesis can provide, through the application of a linear homogeneous polymer. To validate this concept two libraries were prepared, one of peptide and the second of non-peptide origin.

Hyunsoo Han; Mary M. Wolfe; Sydney Brenner; Kim D. Janda

1995-01-01

19

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

20

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

NASA Astrophysics Data System (ADS)

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

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

2008-08-01

21

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

Microsoft Academic Search

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

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

2005-01-01

22

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

23

Transient liquid phase ceramic bonding  

DOEpatents

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

Glaeser, Andreas M. (Berkeley, CA)

1994-01-01

24

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

25

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

26

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...

27

Activity coefficients in the surface phase of liquid mixtures.  

PubMed

A novel equation for evaluating surface activity coefficients is obtained from a recent thermodynamic formalism describing the surface phase of liquid mixtures. The input quantities are the surface tension, bulk activity coefficients and pure constituent thermophysical properties. It is demonstrated thermodynamically that the order of magnitude of each component surface and bulk activity coefficients must be the same. This order is intrinsically associated with the sign of excess surface tension. Reliable activity coefficients of ethanol and water in the surface phase of their mixtures are computed and reported for the first time, by using literature data for the required input quantities. It is shown that the so-called transferring method for estimating surface activity coefficients is severely flawed, because it leads to contradictory values of predicted excess surface tensions depending on which component this prediction is based. PMID:25404471

Santos, M Soledade C S; Reis, João Carlos R

2015-02-01

28

Liquid phase sintering of silicon carbide  

DOEpatents

Liquid phase sintering is used to densify silicon carbide based ceramics using a compound comprising a rare earth oxide and aluminum oxide to form liquids at temperatures in excess of 1600.degree. C. The resulting sintered ceramic body has a density greater than 95% of its theoretical density and hardness in excess of 23 GPa. Boron and carbon are not needed to promote densification and silicon carbide powder with an average particle size of greater than one micron can be densified via the liquid phase process. The sintered ceramic bodies made by the present invention are fine grained and have secondary phases resulting from the liquid phase.

Cutler, Raymond A. (Bountiful, UT); Virkar, Anil V. (Salt Lake City, UT); Hurford, Andrew C. (Salt Lake City, UT)

1989-01-01

29

Liquid phase sintering of silicon carbide  

DOEpatents

Liquid phase sintering is used to densify silicon carbide based ceramics using a compound comprising a rare earth oxide and aluminum oxide to form liquids at temperatures in excess of 1,600 C. The resulting sintered ceramic body has a density greater than 95% of its theoretical density and hardness in excess of 23 GPa. Boron and carbon are not needed to promote densification and silicon carbide powder with an average particle size of greater than one micron can be densified via the liquid phase process. The sintered ceramic bodies made by the present invention are fine grained and have secondary phases resulting from the liquid phase. 4 figs.

Cutler, R.A.; Virkar, A.V.; Hurford, A.C.

1989-05-09

30

Effect of Liquid-phase Siliconizing Process on Silicon Diffusion Behavior in Mo Matrix  

NASA Astrophysics Data System (ADS)

MoSi2 functionally graded coating on Mo substrate is prepared by liquid-phase siliconizing technology. The SEM, GDS and XRD analysis shows that the silicon content in gradient layer appears in three changing regularities. Along the Mo substrate to the surface of the coating, the phase composition of gradient coating changes as follows: Mo ? transition layer Mo (main phase) + Mo3Si + Mo5Si3 ? intermediate layer MoSi2 ? surface layer MoSi2 (main phase) + Si. According to the Si-Mo diffusion couple and Arrhenius equation, the activation energy (Q) was obtained as 430 kJ·mol-1, and the Arrhenius dependence of D on temperature can be described as D = 4.9 × 10-3 exp(-430000/RT) m2/s. The diffusion temperature has an important influence on silicon diffusion coefficient. As the diffusion temperature increases, silicon diffusion coefficient is also gradually increasing.

Zhang, Ying-Yi; Li, Yun-Gang; Shi, Xue-Feng; Qi, Yuan-Hong

2014-09-01

31

Ni Interdiffusion Coefficient and Activation Energy in Cu6Sn5  

NASA Astrophysics Data System (ADS)

Ni diffusion in Cu6Sn5 intermetallic compound was investigated. First, we successfully fabricated preferred-orientation Cu6Sn5 crystal by liquid-phase electroepitaxy (LPEE). Then, Ni/Cu6Sn5 diffusion couples were produced by sputtering from a Ni thin film onto the Cu6Sn5 crystal. Ni/Cu6Sn5 diffusion couples were annealed at different temperatures of 120°C, 160°C, 200°C, 255°C, 290°C, and 320°C for 2 h in a vacuum. The Ni atomic profile across the Ni/Cu6Sn5 interface was obtained by electron spectroscopy for chemical analysis (ESCA). From the Ni atomic profiles, the Matano method was used to evaluate the Ni interdiffusion coefficients ( tilde{D}_{{Ni}} ) in the Cu6Sn5 crystal obtained with different annealing temperatures, which then yields the activation energy for Ni diffusion in the Cu6Sn5 crystal at a particular Ni content. We found that, as Ni diffuses in the ternary Cu6- x Ni x Sn5 compound phase, the activation energy of Ni interdiffusion decreases with the Ni content.

Huang, Kuan-Chih; Shieu, Fuh-Sheng; Hsiao, Y. H.; Liu, C. Y.

2012-01-01

32

Electrolyte Solutions: Activity Coefficients and Debye-Huckel Chemistry 243  

E-print Network

Electrolyte Solutions: Activity Coefficients and Debye-Huckel Theory Chemistry 243 David Ronis McGill University To understand the thermodynamics of electrolyte solutions, we have to understand how nature tries for the chemical potentials and activities. Consider the electrolyte dissociation Az+ + Bz- - + Az+ + - Bz- , (1

Ronis, David M.

33

Vapor-liquid phase separator permeability results  

NASA Technical Reports Server (NTRS)

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

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

1981-01-01

34

Liquid phase sintered compacts in space  

NASA Technical Reports Server (NTRS)

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

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

1974-01-01

35

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

36

Gravitational Role in Liquid Phase Sintering  

NASA Technical Reports Server (NTRS)

To comprehensively understand the gravitational effects on the evolution of both the microstructure and the macrostructure during liquid phase sintering, W-Ni-Fe alloys with W content varying from 35 to 98 wt.% were sintered in microgravity. Compositions that slump during ground-based sintering also distort when sintered under microgravity. In ground-based sintering, low solid content alloys distort with a typical elephant-foot profile, while in microgravity, the compacts tend to spheroidize. This study shows that microstructural segregation occurs in both ground-based as well as microgravity sintering. In ground-based experiments, because of the density difference between the solid and the liquid phase, the solid content increases from top to the bottom of the sample. In microgravity, the solid content increases from periphery to the center of the samples. This study also shows that the pores during microgravity sintering act as a stable phase and attain anomalous shapes.

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

1998-01-01

37

Vapor-liquid phase separator studies  

NASA Technical Reports Server (NTRS)

A study of porous plug use for vapor-liquid phase seperation in spaceborne cryogenic systems was conducted. The three main topics addressed were: (1) the usefulness of porous media in designs that call for variable areas and flow rates; (2) the possibility of prediction of main parameters of porous plugs for a given material; and (3) prediction of all parameters of the plug, including secondary parameters.

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

1985-01-01

38

Transient liquid phase bonding of intermetallics  

Microsoft Academic Search

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

Yimin Guan

1998-01-01

39

TheLiquidPhase: Countercurrent Chromatography  

NSDL National Science Digital Library

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

40

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

41

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

PubMed

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

Kunz, R G; Baade, W F

2001-11-16

42

Prediction of Activity Coefficients of Electrolytes in Aqueous Solutions at High Temperatures  

E-print Network

Prediction of Activity Coefficients of Electrolytes in Aqueous Solutions at High Temperatures solutions containing mixed electrolytes (Lu and Maurer, 1993) is extended from 298 K to temperatures up of mixed electrolytes. The model accurately predicts activity coefficients at high temperatures

Zhang, Luzheng

43

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

Microsoft Academic Search

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

M. Mazar Atabaki; A. Talebi Hanzaei

2010-01-01

44

Liquid phase selective hydrogenation of furfural on Raney nickel modified by impregnation of salts of heteropolyacids  

Microsoft Academic Search

In this paper, liquid phase selective hydrogenation of furfural on Raney nickel which has been modified by impregnation of salts (including alkali metals, alkaline earth metals, and transition metals) of heteropolyacids (HPAs) having Keggin type structure was studied. Effects of reaction conditions on catalytic activity and selectivity were examined. It has been found that all Raney nickel catalysts modified with

Liu Baijun; Lu Lianhai; Wang Bingchun; Cai Tianxi; Katsuyoshi Iwatani

1998-01-01

45

Liquid-phase hydrogenation of cyclohexanone catalyzed by Ni?MgO prepared using citric acid  

Microsoft Academic Search

Ni?MgO catalysts prepared using a melt of the corresponding nitrates and citric acid, with high Ni contents ranging from 60 to 80 wt.%, were found to exhibit excellent catalytic activities for the liquid-phase hydrogenation of cyclohexanone to cyclohexanol under a pressure of 1.1 MPa at 0°C.

Tomohiro Nakayama; Keika Yamashiro; Satoshi Sato; Fumio Nozaki

1997-01-01

46

Mathematical Modeling and Experimental Investigations of Isothermal Solidification during Transient Liquid Phase Bonding of Nickel  

E-print Network

of diffusion, was used to predict the time required to complete isothermal solidification and to determine with the experimentally determined values. The obtained activation energies for diffusion of boron were very close welding [1], transient liquid phase bonding evolved as an effective way to join these superalloys. TLP

Medraj, Mamoun

47

A model for the thermal properties of liquid-phase sintered composites  

SciTech Connect

Thermal properties are important to several applications for powder metallurgy products. For example, liquid-phase sintered tungsten-copper composites are used in microelectronic packaging to obtain a high thermal conductivity in a low thermal expansion material. This article addresses modeling the thermal properties for composites fabricated by liquid-phase sintering. A computational cell is constructed with interlinked phases, consisting of a core of low thermal expansion material (tungsten) and a edge network of high thermal conductivity phase (copper). This structure is used to calculate the composition effects on the coefficients of thermal expansion and thermal conductivity. The results are applied to prior reports on W-Cu and used as a basis to identify several candidate high thermal conductivity systems for future development.

German, R.M. (Pennsylvania State Univ., University Park, PA (United States))

1993-08-01

48

Mixed Stationary Liquid Phases for Gas-Liquid Chromatography.  

ERIC Educational Resources Information Center

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

Koury, Albert M.; Parcher, Jon F.

1979-01-01

49

Numerical simulation of transient liquid phase bonding under temperature gradient.  

E-print Network

??Transient Liquid Phase bonding under Temperature Gradient (TG-TLP bonding) is a relatively new process of TLP diffusion bonding family for joining difficult-to-weld aerospace materials. Earlier… (more)

Ghobadi Bigvand, Arian

2013-01-01

50

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

51

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

52

Liquid-phase mixing of bipropellant doublets  

NASA Technical Reports Server (NTRS)

Experimental results of unlike doublet mixing are correlated with an analytically derived equation predicting fluid cavitation. The correlation relates the minimum orifice pressure drop required to initiate cavitation, with the system back pressure, cold flow simulant vapor pressure, and the orifice flow discharge and contraction coefficients. Stream flow instabilities are also visually correlated with the onset of cavitation and orifice discharge coefficient measurements. The influence of cavitation on the characteristic phenomenon of hydraulic flip is observed for both circular and noncircular shaped orifices. For certain intermediate orifice lengths, some noncircular shapes are shown to produce more fully developed flows (shorter recovery lengths) and therefore a more cohesive jet, which in turn yields slightly higher cold flow mixing uniformities than circular shaped orifices of equal absolute length. The particular noncircular shaped elements evaluated are shown to be more sensitive to liquid stream misimpingement than the corresponding circular orifices.

Hoehn, F. W.; Rupe, J. H.; Sotter, J. G.

1972-01-01

53

Graphene via sonication assisted liquid-phase exfoliation.  

PubMed

Graphene, the 2D form of carbon based material existing as a single layer of atoms arranged in a honeycomb lattice, has set the science and technology sectors alight with interest in the last decade in view of its astounding electrical and thermal properties, combined with its mechanical stiffness, strength and elasticity. Two distinct strategies have been undertaken for graphene production, i.e. the bottom-up and the top-down. The former relies on the generation of graphene from suitably designed molecular building blocks undergoing chemical reaction to form covalently linked 2D networks. The latter occurs via exfoliation of graphite into graphene. Bottom-up techniques, based on the organic syntheses starting from small molecular modules, when performed in liquid media, are both size limited, because macromolecules become more and more insoluble with increasing size, and suffer from the occurrence of side reactions with increasing molecular weight. Because of these reasons such a synthesis has been performed more and more on a solid (ideally catalytically active) surface. Substrate-based growth of single layers can be done also by chemical vapor deposition (CVD) or via reduction of silicon carbide, which unfortunately relies on the ability to follow a narrow thermodynamic path. Top-down approaches can be accomplished under different environmental conditions. Alongside the mechanical cleavage based on the scotch tape approach, liquid-phase exfoliation (LPE) methods are becoming more and more interesting because they are extremely versatile, potentially up-scalable, and can be used to deposit graphene in a variety of environments and on different substrates not available using mechanical cleavage or growth methods. Interestingly, LPE can be applied to produce different layered systems exhibiting different compositions such as BN, MoS2, WS2, NbSe2, and TaS2, thereby enabling the tuning of numerous physico-chemical properties of the material. Furthermore, LPE can be employed to produce graphene-based composites or films, which are key components for many applications, such as thin-film transistors, conductive transparent electrodes for indium tin oxide replacement, e.g. in light-emitting diodes, or photovoltaics. In this review, we highlight the recent progress that has led to successful production of high quality graphene by means of LPE of graphite. In particular, we discuss the mechanisms of exfoliation and methods that are employed for graphene characterization. We then describe a variety of successful liquid-phase exfoliation methods by categorizing them into two major classes, i.e. surfactant-free and surfactant-assisted LPE. Furthermore, exfoliation in aqueous and organic solutions is presented and discussed separately. PMID:24002478

Ciesielski, Artur; Samorì, Paolo

2014-01-01

54

Liquid-Phase Citral Hydrogenation over SiO 2-Supported Group VIII Metals  

Microsoft Academic Search

Liquid-phase citral hydrogenation over SiO2-supported Group VIII metals at 300 K and 1 atm was studied in the absence of all transport limitations as verified by the Madon–Boudart test and the Weisz–Prater criterion. The initial TOF (turnover frequency) for citral hydrogenation varied by three orders of magnitude and exhibited the following trend: Pd>Pt>Ir>Os>Ru>Rh>Ni>Co?Fe (no activity was detected over Fe\\/SiO2). When

Utpal K Singh; M. Albert Vannice

2001-01-01

55

Porous membrane catalysts with Pd-M-clusters for liquid phase hydrogenation of dehydrolinalool  

Microsoft Academic Search

New membrane catalysts with less than 1.5% of Pd in porous stainless steel have been prepared for liquid phase hydrogenation of unsaturated organic compounds. Ultradispersed Pd modified with catalytically active Pb, Mn, or Bi was prepared using Metal Vapour Synthesis techniques. Rates of over 12 mol\\/m2h with selectivities of up to 96% in hydrogenation of dehydrolinalool into linalool under atmospheric

A. N. Karavanov; V. M. Gryaznov; V. I. Lebedeva; I. A. Litvinov; A. Yu. Vasil'kov; A. Yu. Olenin

1995-01-01

56

Application of ionic liquid in liquid phase microextraction technology.  

PubMed

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

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

2012-11-01

57

Solid - liquid phase diagram for ethylene glycol + water  

Microsoft Academic Search

Freezing point data for the system (ethylene glycol + water) were measured independently by two different laboratories. Measurements were made over the entire composition range with particular emphasis on mixtures containing from 55 to 85 weight percent ethylene glycol. Using time vs. temperature cooling and warming curves, the solid-liquid phase diagram of ethylene glycol and water mixtures was determined. The

Dennis R. Cordray; Lisa R. Kaplan; Peter M. Woyciesjes; Theodore F. Kozak

1996-01-01

58

CELLULOSE EXTRACTION FROM PALM KERNEL CAKE USING LIQUID PHASE OXIDATION  

Microsoft Academic Search

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

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

59

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

60

THERMODYNAMICS OF ELECTROLYTES. X. ENTHALPY AND THE EFFECT OF TEMPERATURE ON THE ACTIVITY COEFFICIENTS.  

SciTech Connect

Heat of dilution and of solution data are fitted to the form of equation corresponding to that used successfully for activity and osmotic coefficients over a wide range of concentration. The resulting parameters give the change with temperature of the activity and osmotic coefficients. Results are reported for 84 electrolytes of 1-1, 2-1, 3-1, and 2-2 valence types.

Silvester, Leonard F.; Pitzer, Kenneth S.

1977-11-01

61

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

62

Catalytic and kinetic study of the liquid-phase hydrogenation of various organic substrates over a polymer-anchored Pd(II) catalyst  

Microsoft Academic Search

A polymer-anchored Pd(II) complex has been prepared and characterized using scanning electron microscopy, elemental analysis,\\u000a atomic absorption spectroscopy and FTIR. The catalyst shows excellent catalytic activity in the liquid-phase hydrogenation\\u000a of substituted nitrobenzenes at normal pressure of hydrogen gas at 25 °C in DMF medium. We have also studied the liquid-phase\\u000a hydrogenation of other organic substrates such as alkenes, alkynes, aromatic

Sk. Manirul Islam; Sanchita Mondal; Paromita Mondal; Anupam Singha Roy; Noor Salam; Sumantra Paul; Manir Mobarak

63

Side force coefficient estimation for the design of active brake control  

Microsoft Academic Search

In this paper an active brake control to reduce the rollover risk of heavy vehicles is proposed. The brake system is activated when the vehicle comes close to rolling over. In order to enhance the performance of the active brake, the braking algorithm is extended with an estimation procedure of the side force coefficient in order to use it in

Péter Gáspár; Zoltán Szabó; József Bokor

2006-01-01

64

Mean ionic activity coefficients in aqueous NaCl solutions from molecular dynamics simulations  

NASA Astrophysics Data System (ADS)

The mean ionic activity coefficients of aqueous NaCl solutions of varying concentrations at 298.15 K and 1 bar have been obtained from molecular dynamics simulations by gradually turning on the interactions of an ion pair inserted into the solution. Several common non-polarizable water and ion models have been used in the simulations. Gibbs-Duhem equation calculations of the thermodynamic activity of water are used to confirm the thermodynamic consistency of the mean ionic activity coefficients. While the majority of model combinations predict the correct trends in mean ionic activity coefficients, they overestimate their values at high salt concentrations. The solubility predictions also suffer from inaccuracies, with all models underpredicting the experimental values, some by large factors. These results point to the need for further ion and water model development.

Mester, Zoltan; Panagiotopoulos, Athanassios Z.

2015-01-01

65

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

66

Liquid phase hydrogenation in a structured multichannel reactor  

Microsoft Academic Search

A compact, structured, multichannel reactor was tested for two exemplary reactions: the selective hydrogenation of aromatic aldehyde and the tandem C–C coupling–hydrogenation. In the case of hydrogenation reaction up to 50% yield with ca. 96% selectivity was attained in a single pass (single channel of 10cm length of catalytic bed) at a liquid phase residence time of ca. 10s, proving

Xiaolei Fan; Alexei A. Lapkin; Pawel K. Plucinski

2009-01-01

67

Molecular libraries in liquid phase via UGI-MCR  

Microsoft Academic Search

Standard chemistry prescribes the conversion of one or two compounds into their products. In contrast, Eintopf (one-pot) multicomponent\\u000a reactions (MCRs) involve at least three different compounds. One-pot MCRs are a useful tool in combinatorial chemistry: From\\u000a a mixture of educts a large number of products can be simultaneously formed in liquid phase, called a soluble molecular library.\\u000a The member compounds

Ivar Ugi; Matthias Goebel; Bernhard Gruber; Martin Heilingbrunner; Carola Heiß; Werner Hörl; Oliver Kern; Manfred Starnecker; Alexander Dömling

1996-01-01

68

Selective Liquid-Phase Hydrogenation of Citral over Supported Palladium  

Microsoft Academic Search

Citral in the liquid phase was reduced in a low-pressure hydrogenator by using catalysts consisting of palladium supported on (a) a mixed 80:20 SiO2\\/AlPO4system and (b) sepiolite from Vallecas (Madrid, Spain). A kinetic study provided the reaction orders in the substrate concentration and hydrogen pressure. Experimental variables such as temperature, hydrogen pressure and the type of solvent were adjusted in

M. A. Aramend??a; V. Borau; C. Jiménez; J. M. Marinas; A. Porras; F. J. Urbano

1997-01-01

69

Bimodal porous Pd–silica for liquid-phase hydrogenation  

Microsoft Academic Search

Palladium catalysts loaded on bimodal porous silica were examined in the liquid-phase hydrogenation of 2-butenal at 0°C and a hydrogen pressure of 1.1MPa. The sizes of mesopores and macropores of the silica support are controllable in the range of 4–23nm and 0.5–25?m, respectively. The macropores provide effective paths of mass transfer, and the mesopores present effective surfaces for dispersion of

Satoshi Sato; Ryoji Takahashi; Toshiaki Sodesawa; Masashi Koubata

2005-01-01

70

Gas-liquid phase coexistence and crossover behavior of binary ionic fluids with screened Coulomb interactions.  

PubMed

We study the effects of an interaction range on the gas-liquid phase diagram and the crossover behavior of a simple model of ionic fluids: an equimolar binary mixture of equisized hard spheres interacting through screened Coulomb potentials which are repulsive between particles of the same species and attractive between particles of different species. Using the collective variables theory, we find explicit expressions for the relevant coefficients of the effective ?{4} Ginzburg-Landau Hamiltonian in a one-loop approximation. Within the framework of this approximation, we calculate the critical parameters and gas-liquid phase diagrams for varying inverse screening length z. Both the critical temperature scaled by the Yukawa potential contact value and the critical density rapidly decrease with an increase of the interaction range (a decrease of z) and then for z<0.05 they slowly approach the values found for a restricted primitive model (RPM). We find that gas-liquid coexistence region reduces with an increase of z and completely vanishes at z?2.78. Our results clearly show that an increase in the interaction range leads to a decrease of the crossover temperature. For z?0.01, the crossover temperature is the same as for the RPM. PMID:25019760

Patsahan, O

2014-06-01

71

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

72

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

E-print Network

Ultrafast dynamics of the laser-induced solid-to-liquid phase transition in aluminum A thesis dynamics of the laser-induced solid-to-liquid phase transition in aluminum Eric Mazur Maria Kandyla Abstract This dissertation reports the ultrafast dynamics of aluminum during the solid-to- liquid phase

Mazur, Eric

73

Modeling the solid-liquid phase transition in saturated triglycerides  

NASA Astrophysics Data System (ADS)

We investigated theoretically two competing published scenarios for the melting transition of the triglyceride trilaurin (TL): those of (1) Corkery et al. [Langmuir 23, 7241 (2007)], in which the average state of each TL molecule in the liquid phase is a discotic "Y" conformer whose three chains are dynamically twisted, with an average angle of ˜120° between them, and those of (2) Cebula et al. [J. Am. Oil Chem. Soc. 69, 130 (1992)], in which the liquid-state conformation of the TL molecule in the liquid phase is a nematic h?-conformer whose three chains are in a modified "chair" conformation. We developed two competing models for the two scenarios, in which TL molecules are in a nematic compact-chair (or "h") conformation, with extended, possibly all-trans, chains at low-temperatures, and in either a Y conformation or an h? conformation in the liquid state at temperatures higher than the phase-transition temperature, T?=319 K. We defined an h-Y model as a realization of the proposal of Corkery et al. [Langmuir 23, 7241 (2007)], and explored its predictions by mapping it onto an Ising model in a temperature-dependent field, performing a mean-field approximation, and calculating the transition enthalpy ?H. We found that the most plausible realization of the h-Y model, as applied to the solid-liquid phase transition in TL, and likely to all saturated triglycerides, gave a value of ?H in reasonable agreement with the experiment. We then defined an alternative h-h? model as a realization of the proposal of Cebula et al. [J. Am. Oil Chem. Soc. 69, 130 (1992)], in which the liquid phase exhibits an average symmetry breaking similar to an h conformation, but with twisted chains, to see whether it could describe the TL phase transition. The h-h? model gave a value of ?H that was too small by a factor of ˜3-4. We also predicted the temperature dependence of the 1132 cm-1 Raman band for both models, and performed measurements of the ratios of three TL Raman bands in the temperature range of -20 °C?T ?90 °C. The experimental results were in accord with the predictions of the h-Y model and support the proposal of Corkery et al. [Langmuir 23, 7241 (2007)] that the liquid state is made up of molecules that are each, on average, in a Y conformation. Finally, we carried out computer simulations of minimal-model TLs in the liquid phase, and concluded that although the individual TL molecules are, on average, Y conformers, long-range discotic order is unlikely to exist.

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

2010-02-01

74

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

SciTech Connect

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

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

1995-04-01

75

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...

76

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

USGS Publications Warehouse

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

Truesdell, A.H.

1968-01-01

77

Explaining Activity Coefficients and Standard States in the Undergraduate Physical Chemistry Course.  

ERIC Educational Resources Information Center

Since activity coefficients are difficult even for good students to understand from the normal presentations in undergraduate physical chemistry, the author has reanalyzed this concept and presents a new way for introducing it. A practice problem (with solution) is included. (JN)

Fanelli, A.

1986-01-01

78

Infinite Dilution Activity Coefficients of Acetone in Water A New Experimental Method and Verification  

E-print Network

Infinite Dilution Activity Coefficients of Acetone in Water A New Experimental Method region. However, this is solution model dependent, i.e. different models describing the same acetone of the resultant values. Results for acetone are reported and compared to literature values. The comparison

Howat, Colin S. "Chip"

79

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

80

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

81

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

82

Vapors-liquid phase separator. [infrared telescope heat sink  

NASA Technical Reports Server (NTRS)

The use of porous plugs, mostly with in the form of passive devices with constant area were considered as vapor-liquid phase separators for helium 2 storage vessels under reduced gravity. The incorporation of components with variable cross sectional area as a method of flow rate modification was also investigated. A particular device which uses a shutter-type system for area variation was designed and constructed. This system successfully permitted flor rate changes of up to plus or minus 60% from its mean value.

Frederking, T. H. K.; Brown, G. S.; Chuang, C.; Kamioka, Y.; Kim, Y. I.; Lee, J. M.; Yuan, S. W. K.

1980-01-01

83

Liquid phase synthesis of copper indium diselenide nanoparticles  

SciTech Connect

Nanoparticles of Copper Indium diselenide (CuInSe{sub 2}), belongs to I-III-VI{sub 2} family has been synthesized via liquid phase route using ethylenediamine as a solvent. Characterization of as-grown particles is done by XRD, HRTEM, DLS, optical microscopy and UV-Vis spectroscopy. X-ray diffraction pattern confirmed that the CuInSe2 nanoparticles obtained reveals chalcopyrite structure. Particle size evaluated from dynamic light scattering of as grown particle possessing radius of 90 nm. The bandgap of 1.05eV is obtained from UV-Vis spectrum which will applicable to the solar cell devices.

Jakhmola, Priyanka; Agarwal, Garima; Jha, Prafulla K.; Bhatnagar, S. P. [Department of Physics, MaharajaKrishnakumar Sinhji, Bhavnagar University, Bhavnagar-364001 (India)

2014-04-24

84

Coefficients for active transport and thermogenesis of Ca2+-ATPase isoforms.  

PubMed

Coefficients for active transport of ions and heat in vesicles with Ca(2+)-ATPase from sarcoplasmic reticulum are defined in terms of a newly proposed thermodynamic theory and calculated using experiments reported in the literature. The coefficients characterize in a quantitative manner different performances of the enzyme isoforms. Four enzyme isoforms are examined, namely from white and red muscle tissue, from blood platelets, and from brown adipose mitochondria. The results indicate that the isoforms have a somewhat specialized function. White muscle tissue and brown adipose tissue have the same active transport coefficient ratio, but the activity level of the enzyme in white muscle is higher than in brown adipose tissue. The thermogenesis ratio is high in both white muscle and brown adipose tissue, in agreement with a specific role in nonshivering thermogenesis. Other isoforms do not have this ability to generate heat. A calcium-dependence of the coefficients is found, which can be understood as being in accordance with the role of this ion as a messenger in muscle contraction as well as in thermogenesis. The investigation points to new experiments related to structure as well as to function of the isoforms. PMID:19486662

Kjelstrup, Signe; Barragán, Daniel; Bedeaux, Dick

2009-06-01

85

Partial Liquid-Phase Hydrogenation of Benzene to Cylohexene on SiO 2 Immobilized Lanthanide (Eu and Yb) Catalysts  

Microsoft Academic Search

SiO2-immobilized Eu and Yb catalysts (=Si–O–Ln–NH2) obtained by the reaction of surface hydroxyl groups on SiO2 with lanthanide metals dissolved in liquid ammonia are active for the partial liquid-phase hydrogenation of benzene to cyclohexene when the reaction was carried out at 423–483 K with hydrogen pressures of 1–5 MPa. Interestingly, only divalent amides are catalytically effective for the partial hydrogenation

Hayao Imamura; Toshiko Kumai; Koji Nishimura; Takayuki Nuruyu; Yoshihisa Sakata

2002-01-01

86

Palladiumcopper and palladium-tin catalysts in the liquid phase nitrate hydrogenation in a batch-recycle reactor  

Microsoft Academic Search

Catalytic liquid phase nitrate reduction was investigated at T=298K and atmospheric pressure in an isothermal batch-recycle reactor in the presence of various Pd-Cu and Pd-Sn bimetallic catalysts supported on alumina spheres with particle diameter of 1.7mm. It was discovered that Pd-Sn solids synthesized accordingly to various catalyst preparation methods, exhibit considerably lower activity for nitrate removal in comparison to Pd-Cu

Albin Pintar; Jurka Batista; Igor Muševi?

2004-01-01

87

Electrochemical characterization of liquid phase exfoliated two-dimensional layers of molybdenum disulfide.  

PubMed

We report on the electrochemical charge storage behavior of few-layered flakes of molybdenum disulfide (MoS2) obtained by liquid phase exfoliation of bulk MoS2 powder in 1-dodecyl-2-pyrrolidinone. The specific capacitances of the exfoliated flakes obtained using a 6 M KOH aqueous solution as an electrolyte were found to be an order of magnitude higher than those of bulk MoS2 (?0.5 and ?2 mF cm(-2) for bulk and exfoliated MoS2 electrodes, respectively). The exfoliated MoS2 flakes also showed significant charge storage in different electrolytes, such as organic solvents [1 M tetraethylammonium tetrafluoroborate in propylene carbonate (Et4NBF4 in PC)] and ionic liquids [1-butyl-3-methylimidazolium hexafluorophosphate (BMIM-PF6)]. The values of specific capacitances obtained using Et4NBF4 in PC and BMIM-PF6 were ?2.25 and ?2.4 mF cm(-2), respectively. An analysis of electrochemical impedance spectroscopy using an equivalent circuit modeling was performed to understand the charge storage mechanism of these exfoliated MoS2 flakes using different electrolytes. Our findings indicate that liquid phase exfoliation methods can be used to produce large quantities of electrochemically active, two-dimensional layers of MoS2 and can act as an ideal material in several applications related to electrochemistry. PMID:24444714

Winchester, Andrew; Ghosh, Sujoy; Feng, Simin; Elias, Ana Laura; Mallouk, Tom; Terrones, Mauricio; Talapatra, Saikat

2014-02-12

88

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

PubMed Central

The activity coefficient is largely considered an empirical parameter that was traditionally introduced to correct the non-ideality observed in thermodynamic systems such as osmotic pressure. Here, the activity coefficient of free-solvent is related to physically realistic parameters and a mathematical expression is developed to directly predict the activity coefficients of free-solvent, for aqueous protein solutions up to near-saturation concentrations. The model is based on the free-solvent model, which has previously been shown to provide excellent prediction of the osmotic pressure of concentrated and crowded globular proteins in aqueous solutions up to near-saturation concentrations. Thus, this model uses only the independently determined, physically realizable quantities: mole fraction, solvent accessible surface area, and ion binding, in its prediction. Predictions are presented for the activity coefficients of free-solvent for near-saturated protein solutions containing either bovine serum albumin or hemoglobin. As a verification step, the predictability of the model for the activity coefficient of sucrose solutions was evaluated. The predicted activity coefficients of free-solvent are compared to the calculated activity coefficients of free-solvent based on osmotic pressure data. It is observed that the predicted activity coefficients are increasingly dependent on the solute-solvent parameters as the protein concentration increases to near-saturation concentrations. PMID:24324733

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

2013-01-01

89

Existence of a liquid-liquid phase transition in methanol  

NASA Astrophysics Data System (ADS)

A simple model is constructed to study the phase diagram and thermodynamic properties of methanol, which is described as a dimer of an apolar sphere mimicking the methyl group and a sphere with core-softened potential as the hydroxyl group. Performing classical Monte Carlo simulations, we obtained the phase diagram, showing a second critical point between two different liquid phases. Evaluating systems with a different number of particles, we extrapolate to infinite size in accordance with Ising universality class to obtain bulk values for critical temperature, pressure, and density. Strong evidence that the structure of the liquid changes upon transition from high- to low-density phase was provided. From the experimentally determined hydrogen bond strength and length in methanol and water, we propose where the second critical point of methanol should be.

Huš, Matej; Urbic, Tomaz

2014-12-01

90

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

91

Numerical Simulation of Transient Liquid Phase Bonding under Temperature Gradient  

NASA Astrophysics Data System (ADS)

Transient Liquid Phase bonding under Temperature Gradient (TG-TLP bonding) is a relatively new process of TLP diffusion bonding family for joining difficult-to-weld aerospace materials. Earlier studies have suggested that in contrast to the conventional TLP bonding process, liquid state diffusion drives joint solidification in TG-TLP bonding process. In the present work, a mass conservative numerical model that considers asymmetry in joint solidification is developed using finite element method to properly study the TG-TLP bonding process. The numerical results, which are experimentally verified, show that unlike what has been previously reported, solid state diffusion plays a major role in controlling the solidification behavior during TG-TLP bonding process. The newly developed model provides a vital tool for further elucidation of the TG-TLP bonding process.

Ghobadi Bigvand, Arian

92

Growth of hexagonal ferrite films by liquid phase epitaxy  

Microsoft Academic Search

Single crystal hexagonal ferrite layers were grown by the isothermal dipping method of LPE (liquid phase epitaxy) using a BaO-B2O3flux. Substrate crystals were of two different types: hexagonal ferrite and Mg(In,Ga)2O4spinel. By adding ZnO to the LPE melt, three different hexagonal ferrites were deposited: M-type (BaO.6Fe2O3), Zn2Y-type (2BaO.2ZnO.6Fe2O3) and Zn2W-type (BaO.2ZnO.8Fe2O3). On hexagonal ferrite substrates the deposits formed continuous layers;

H. Glass; F. Stearns

1977-01-01

93

Relationships between octan?1?ol\\/water partition coefficients, aqueous activity coefficients and reversed phase HPLC capacity factors of alkylbenzenes, chlorobenzenes, chloronaphthalenes and chlorobiphenyls  

Microsoft Academic Search

Linear relationships between logarithms of octan?1?ol\\/water partition coefficients (Kd,oct), aqueous activity coefficients (yaq) and extrapolated RP HPLC capacity factors (k‘w) are found for four types of aromatic hydrocarbons (alkylbenzenes and poly?chlorinated benzenes, ?naphthalenes and ?biphenyls).Both log K,d,oct and logk‘w increase with the increasing number of chlorine or methyl?ene substituents. These increases of log K,d,oct and log k‘w are proportional and

Antoon Opperhuizen

1987-01-01

94

Flash flow pyrolysis: mimicking flash vacuum pyrolysis in a high-temperature/high-pressure liquid-phase microreactor environment.  

PubMed

Flash vacuum pyrolysis (FVP) is a gas-phase continuous-flow technique where a substrate is sublimed through a hot quartz tube under high vacuum at temperatures of 400-1100 °C. Thermal activation occurs mainly by molecule-wall collisions with contact times in the region of milliseconds. As a preparative method, FVP is used mainly to induce intramolecular high-temperature transformations leading to products that cannot easily be obtained by other methods. It is demonstrated herein that liquid-phase high-temperature/high-pressure (high-T/p) microreactor conditions (160-350 °C, 90-180 bar) employing near- or supercritical fluids as reaction media can mimic the results obtained using preparative gas-phase FVP protocols. The high-T/p liquid-phase "flash flow pyrolysis" (FFP) technique was applied to the thermolysis of Meldrum's acid derivatives, pyrrole-2,3-diones, and pyrrole-2-carboxylic esters, producing the expected target heterocycles in high yields with residence times between 10 s and 10 min. The exact control over flow rate (and thus residence time) using the liquid-phase FFP method allows a tuning of reaction selectivities not easily achievable using FVP. Since the solution-phase FFP method does not require the substrate to be volatile any more--a major limitation in classical FVP--the transformations become readily scalable, allowing higher productivities and space-time yields compared with gas-phase protocols. Differential scanning calorimetry measurements and extensive DFT calculations provided essential information on pyrolysis energy barriers and the involved reaction mechanisms. A correlation between computed activation energies and experimental gas-phase FVP (molecule-wall collisions) and liquid-phase FFP (molecule-molecule collisions) pyrolysis temperatures was derived. PMID:22321044

Cantillo, David; Sheibani, Hassan; Kappe, C Oliver

2012-03-01

95

Improved AIOMFAC model parameterisation of the temperature dependence of activity coefficients for aqueous organic mixtures  

NASA Astrophysics Data System (ADS)

This study presents a new, improved parameterisation of the temperature dependence of activity coefficients in the AIOMFAC (Aerosol Inorganic-Organic Mixtures Functional groups Activity Coefficients) model applicable for aqueous as well as water-free organic solutions. For electrolyte-free organic and organic-water mixtures the AIOMFAC model uses a group-contribution approach based on UNIFAC (UNIversal quasi-chemical Functional-group Activity Coefficients). This group-contribution approach explicitly accounts for interactions among organic functional groups and between organic functional groups and water. The previous AIOMFAC version uses a simple parameterisation of the temperature dependence of activity coefficients, aimed to be applicable in the temperature range from ~ 275 to ~ 400 K. With the goal to improve the description of a wide variety of organic compounds found in atmospheric aerosols, we extend the AIOMFAC parameterisation for the functional groups carboxyl, hydroxyl, ketone, aldehyde, ether, ester, alkyl, aromatic carbon-alcohol, and aromatic hydrocarbon to atmospherically relevant low temperatures. To this end we introduce a new parameterisation for the temperature dependence. The improved temperature dependence parameterisation is derived from classical thermodynamic theory by describing effects from changes in molar enthalpy and heat capacity of a multi-component system. Thermodynamic equilibrium data of aqueous organic and water-free organic mixtures from the literature are carefully assessed and complemented with new measurements to establish a comprehensive database, covering a wide temperature range (~ 190 to ~ 440 K) for many of the functional group combinations considered. Different experimental data types and their processing for the estimation of AIOMFAC model parameters are discussed. The new AIOMFAC parameterisation for the temperature dependence of activity coefficients from low to high temperatures shows an overall improvement of 28% in comparison to the previous model version, when both versions are compared to our database of experimentally determined activity coefficients and related thermodynamic data. When comparing the previous and new AIOMFAC model parameterisations to the subsets of experimental data with all temperatures below 274 K or all temperatures above 322 K (i.e. outside a 25 K margin of the reference temperature of 298 K), applying the new parameterisation leads to 37% improvement in each of the two temperature ranges considered. The new parameterisation of AIOMFAC agrees well with a large number of experimental data sets. Larger model-measurement discrepancies were found particularly for some of the systems containing multi-functional organic compounds. The affected systems were typically also poorly represented at room temperature and further improvements will be necessary to achieve better performance of AIOMFAC in these cases (assuming the experimental data are reliable). The performance of the AIOMFAC parameterisation is typically better for systems containing relatively small organic compounds and larger deviations may occur in mixtures where molecules of high structural complexity such as highly oxygenated compounds or molecules of high molecular mass (e.g. oligomers) prevail. Nevertheless, the new parameterisation enables the calculation of activity coefficients for a wide variety of different aqueous/water-free organic solutions down to the low temperatures present in the upper troposphere.

Ganbavale, G.; Zuend, A.; Marcolli, C.; Peter, T.

2015-01-01

96

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

97

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

NASA Technical Reports Server (NTRS)

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

Yang, Sung-Chul; German, Randall M.

1991-01-01

98

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

99

Low Temperature Transient Liquid Phase (LTTLP) Bonding for Au/Cu  

E-print Network

) ) M. M. Hou Low Temperature Transient Liquid Phase (LTTLP) Bonding for Au/Cu and Cu of Technology, Cambridge, MA 02139 TheLow Temperature TransientLiquidPhase Diffusion Bonding (LTTLP) process has been bonded to copper heatsink.s at temperatures less than 160"C, using /n-Sn eutectic solders. After

Eagar, Thomas W.

100

Liquid-Liquid Phase Transition of Protein Aqueous Solutions Isothermally Induced by Protein Cross-Linking  

E-print Network

of protein-rich liquid droplets for bovine serum albumin and chicken egg lysozyme at 25 °C. These dropletsLiquid-Liquid Phase Transition of Protein Aqueous Solutions Isothermally Induced by Protein Cross that liquid-liquid phase separation (LLPS) of protein aqueous solutions can be induced by isothermal protein

Annunziata, Onofrio

101

Spin Liquid Phases for Spin-1 Systems on the Triangular Lattice  

E-print Network

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 ...

Xu, Cenke

102

Computer simulation of grain growth by grain boundary migration during liquid phase sintering  

Microsoft Academic Search

From many experiments with mixtures of small and large particles, it can be concluded that during liquid phase sintering, smaller particles partially dissolve and a solid phase precipitates on the larger particles. Therefore, the number of smaller particles decreases due to coarsening. The growth rate can be controlled either by the solid-liquid phase boundary reaction or by diffusion through the

Z. S. Nikolic

1999-01-01

103

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

PubMed

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

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

2014-07-01

104

Solubility parameter and activity coefficient of HDEHP dimer in select organic diluents by vapor pressure osmometry  

SciTech Connect

A thorough understanding of the non-ideal behavior of the chemical components utilized in solvent extraction contributes to the success of any large-scale spent nuclear fuel treatment. To address this, our current work uses vapor pressure osmometry to characterize the non-ideal behavior of the solvent extraction agent di-(2-ethylhexyl) phosphoric acid (HDEHP), a common extractant in proposed separation schemes. Solubility parameters were fit to data on HDEHP at four temperatures using models based on Scatchard Hildebrand regular solution theory with Flory Huggins entropic corrections. The results are comparable but not identical to the activity coefficients from prior slope analysis in the literature. (authors)

Gray, M.; Nilsson, M. [University of California Irvine, 916 Engineering Tower, UC Irvine, Irvine, CA 92697-2575 (United States); Zalupski, P. [Idaho National Laboratory, 2525 Fremont Avenue, Idaho Falls, ID 83415 (United States)

2013-07-01

105

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

106

Hyperdoping silicon with selenium: solid vs. liquid phase epitaxy  

PubMed Central

Chalcogen-hyperdoped silicon shows potential applications in silicon-based infrared photodetectors and intermediate band solar cells. Due to the low solid solubility limits of chalcogen elements in silicon, these materials were previously realized by femtosecond or nanosecond laser annealing of implanted silicon or bare silicon in certain background gases. The high energy density deposited on the silicon surface leads to a liquid phase and the fast recrystallization velocity allows trapping of chalcogen into the silicon matrix. However, this method encounters the problem of surface segregation. In this paper, we propose a solid phase processing by flash-lamp annealing in the millisecond range, which is in between the conventional rapid thermal annealing and pulsed laser annealing. Flash lamp annealed selenium-implanted silicon shows a substitutional fraction of ~ 70% with an implanted concentration up to 2.3%. The resistivity is lower and the carrier mobility is higher than those of nanosecond pulsed laser annealed samples. Our results show that flash-lamp annealing is superior to laser annealing in preventing surface segregation and in allowing scalability. PMID:25660096

Zhou, Shengqiang; Liu, Fang; Prucnal, S.; Gao, Kun; Khalid, M.; Baehtz, C.; Posselt, M.; Skorupa, W.; Helm, M.

2015-01-01

107

Effect of dimensionality on vapor-liquid phase transition  

SciTech Connect

Dimensionality play significant role on ‘phase transitions’. Fluids in macroscopic confinement (bulk or 3-Dimensional, 3D) do not show significant changes in their phase transition properties with extent of confinement, since the number of molecules away from the surrounding surfaces is astronomically higher than the number of molecules in close proximity of the confining surfaces. In microscopic confinement (quasi 3D to quasi-2D), however, the number of molecules away from the close proximity of the surface is not as high as is the case with macroscopic (3D) confinement. Hence, under the same thermodynamic conditions ‘phase transition’ properties at microscopic confinement may not remain the same as the macroscopic or 3D values. Phase transitions at extremely small scale become very sensitive to the dimensions as well as the surface characteristics of the system. In this work our investigations reveal the effect of dimensionality on the phase transition from 3D to quasi-2D to 2D behavior. We have used grand canonical transition matrix Monte Carlo simulation to understand the vapor–liquid phase transitions from 3D to quasi-2D behavior. Such studies can be helpful in understanding and controlling the fluid film behaviour confined between solid surfaces of few molecular diameters, for example, in lubrication applications.

Singh, Sudhir Kumar, E-mail: sksingh@thapar.edu [Department Chemical Engineering, Thapar University, Patiala-147004 Punjab (India)

2014-04-24

108

Hyperdoping silicon with selenium: solid vs. liquid phase epitaxy.  

PubMed

Chalcogen-hyperdoped silicon shows potential applications in silicon-based infrared photodetectors and intermediate band solar cells. Due to the low solid solubility limits of chalcogen elements in silicon, these materials were previously realized by femtosecond or nanosecond laser annealing of implanted silicon or bare silicon in certain background gases. The high energy density deposited on the silicon surface leads to a liquid phase and the fast recrystallization velocity allows trapping of chalcogen into the silicon matrix. However, this method encounters the problem of surface segregation. In this paper, we propose a solid phase processing by flash-lamp annealing in the millisecond range, which is in between the conventional rapid thermal annealing and pulsed laser annealing. Flash lamp annealed selenium-implanted silicon shows a substitutional fraction of ~ 70% with an implanted concentration up to 2.3%. The resistivity is lower and the carrier mobility is higher than those of nanosecond pulsed laser annealed samples. Our results show that flash-lamp annealing is superior to laser annealing in preventing surface segregation and in allowing scalability. PMID:25660096

Zhou, Shengqiang; Liu, Fang; Prucnal, S; Gao, Kun; Khalid, M; Baehtz, C; Posselt, M; Skorupa, W; Helm, M

2015-01-01

109

Dynamic headspace liquid-phase microextraction of alcohols.  

PubMed

A method was developed using dynamic headspace liquid-phase microextraction and gas chromatography-mass spectrometry for extraction and determination of 9 alcohols from water samples. Four different solvents, hexyl acetate, n-octanol, o-xylene and n-decane were studied as extractants. The analytes were extracted using 0.8 microl of n-octanol from the headspace of a 2 ml sample solution. The effect of sampling volume, solvent volume, sample temperature, syringe plunger withdrawal rate and ionic strength of the solution on the extraction performance were studied. A semiautomated system including a variable speed stirring motor was used to ensure a uniform movement of syringe plunger through the barrel. The method provided a fairly good precision for all compounds (5.5-9.3%), except methanol (16.4%). Detection limits were found to be between 1 and 97 microg/l within an extraction time of approximately 9.5 min under GC-MS in full scan mode. PMID:15679138

Saraji, Mohammad

2005-01-01

110

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

111

Effect of dimensionality on vapor-liquid phase transition  

NASA Astrophysics Data System (ADS)

Dimensionality play significant role on `phase transitions'. Fluids in macroscopic confinement (bulk or 3-Dimensional, 3D) do not show significant changes in their phase transition properties with extent of confinement, since the number of molecules away from the surrounding surfaces is astronomically higher than the number of molecules in close proximity of the confining surfaces. In microscopic confinement (quasi 3D to quasi-2D), however, the number of molecules away from the close proximity of the surface is not as high as is the case with macroscopic (3D) confinement. Hence, under the same thermodynamic conditions `phase transition' properties at microscopic confinement may not remain the same as the macroscopic or 3D values. Phase transitions at extremely small scale become very sensitive to the dimensions as well as the surface characteristics of the system. In this work our investigations reveal the effect of dimensionality on the phase transition from 3D to quasi-2D to 2D behavior. We have used grand canonical transition matrix Monte Carlo simulation to understand the vapor-liquid phase transitions from 3D to quasi-2D behavior. Such studies can be helpful in understanding and controlling the fluid film behaviour confined between solid surfaces of few molecular diameters, for example, in lubrication applications.

Singh, Sudhir Kumar

2014-04-01

112

Molecular weight distributions of polydisperse polymers in coexisting liquid phases  

NASA Astrophysics Data System (ADS)

We present new experimental measurements of the molecular weight (MW) distributions in coexisting liquid phases for three polymer/solvent systems. We studied samples at the critical compositions and at four temperatures in the two-phase regions. For polystyrene in methylcyclohexane (with an upper critical solution point), we observed the expected fractionation between phases, with a higher average MW in the lower, polymer-rich phase. For poly(ethylene oxide) in 2, 6-lutidine+water (with a lower critical solution point), the total polymer mass is nearly equal in the two phases, but the polymers of higher average MW equilibrate into the upper, 2,6-lutidine-rich phase. For poly(ethylene oxide) in isobutyric acid+water (with an upper critical solution point), most of the total polymer mass is in the upper, isobutyric acid-rich phase, but the polymers of higher average MW equilibrate into the lower, water-rich phase; moreover, the fractionation in this case is quite dramatic, with almost a factor of 2 difference in average MW between the phases and a significant decrease in polydispersity for the lower phase. Our results support prior experimental results on this phenomenon that find that a basic Flory-Huggins (FH) theory is inadequate. More recent theoretical considerations suggest that the difference between FH theory and experiments is due to non-mean field effects, but this theory awaits direct comparison to experiments.

Shresth, R. Saurabh; McDonald, R. Christopher; Greer, Sandra C.

2002-11-01

113

Thermal conductivity of alternative refrigerants in the liquid phase  

SciTech Connect

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

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

1996-05-01

114

Calculation of activity coefficients and degrees of formation of neutral ion pairs in supercritical electrolyte solutions  

NASA Astrophysics Data System (ADS)

Although hydrothermal solutions at high temperatures and low pressures where the solution density is low are widely regarded as highly associated alkali chloride solutions in which neutral ion pairs are the predominant solute species, reconsideration in the present study of experimental conductance data reported by QUIST and MARSHALL ( 1968a,b,c), DUNN and MARSHALL (1969) and FRANTZ and MARSHALL (1984) for 1:1 electrolytes suggests that this may not be the case. Quist, Marshall, and their coworkers interpreted their high temperature/pressure conductance data in part by considering the activity coefficients of the neutral species to be negligibly different from unity in dilute solutions. However, these data can also be interpreted by regarding the logarithm of the activity coefficients of neutral complexes ( ¯ggn ) to be a linear function of the effective ionic strength ( ?), which is consistent with both the SETCHÉNOW (1892) and HÜCKEL (1925) equations ( HELGESON et al., 1981). Accordingly, supercritical conductance data for five electrolytes were regressed in the present study using the HÜCKEL (1925), SETCHÉNOW (1892), and SHEDLOVSKY (1938) equations, together with the law of mass action and values of the limiting equivalent conductances of the electrolytes taken from OELKERS and HELGESON (1989) for the temperatures and pressures of the experiments to generate simultaneously the logarithms of dissociation constants ( log K 1) and Setchénow coefficients ( b ?,n) for neutral 1:1 complexes. The resulting values of log K 1 are in close agreement with corresponding values originally reported by Marshall and coworkers. However, the regression calculations indicate that b ?,n and thus the activity coefficients of neutral species in concentrated electrolyte solutions increase dramatically with increasing temperature and decreasing pressure, which opposes the effect on ion pair formation of the accompanying decrease in log K 1. Distribution of species calculations using these values of log K 1 and b ?,n with and without provision for the formation of triple ions ( OELKERS and HELGESON, 1990) indicate that the degrees of formation of neutral 1:1 ion pairs maximize at stoichiometric ionic strengths of 0.2 molal and become negligible at stoichiometric ionic strengths greater than 0.8 molal in the temperature range 400 to 800°C at pressures to 4 kb. Consequently, it appears that these neutral species may account for only a minor part of the solute in concentrated hydrothermal solutions at supercritical temperatures and pressures. This observation is supported also by electrostatic considerations, which indicate that higher order complexes may predominate in concentrated electrolyte solutions at supercritical temperatures and pressures ( PITZER and SCHREIBER, 1987; OELKERS and HELGESON, 1990).

Oelkers, Eric H.; Helgeson, Harold C.

1991-05-01

115

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

116

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

117

Asymmetric Diffusional Solidification during Transient Liquid Phase Bonding of Dissimilar Materials  

NASA Astrophysics Data System (ADS)

A theoretical analysis of diffusional solidification during transient liquid phase (TLP) bonding of dissimilar materials was performed in conjunction with experimental verification. A fully implicit, two-dimensional, finite element numerical simulation model, without the inherent symmetry assumption, was developed and used for the theoretical calculations, and good correlations between the model predictions and experimental results were observed. The study showed that an asymmetric distribution of residual interlayer liquid during a dissimilar joining of polycrystal and single crystal alloys is attributable to a mismatch between their lattice diffusion coefficients or solute solubility, irrespective of enhanced intergranular diffusion as was assumed previously. Also, notwithstanding increased solute diffusivity with temperature, it was found that an increase in bonding temperature can result in the prolongation of processing time t f that is required to prevent the formation of deleterious eutectic during bonding of dissimilar materials. The occurrence of this seemingly anomalous behavior, however, reduces when a material is coupled with another type that exhibits a higher solute solubility or better capability of accommodating diffusing melting point depressant solute from the liquid interlayer.

Ghoneim, A.; Ojo, O. A.

2012-03-01

118

Laser-induced separation of hydrogen isotopes in the liquid phase  

DOEpatents

Hydrogen isotope separation is achieved by either (a) dissolving a hydrogen-bearing feedstock compound in a liquid solvent, or (b) liquefying a hydrogen-bearing feedstock compound, the liquid phase thus resulting being kept at a temperature at which spectral features of the feedstock relating to a particular hydrogen isotope are resolved, i.e., a clear-cut isotope shift is delineated, irradiating the liquid phase with monochromatic radiation of a wavelength which at least preferentially excites those molecules of the feedstock containing a first hydrogen isotope, inducing photochemical reaction in the excited molecules, and separating the reaction product containing the first isotope from the liquid phase.

Freund, Samuel M. (Los Alamos, NM); Maier, II, William B. (Los Alamos, NM); Beattie, Willard H. (Los Alamos, NM); Holland, Redus F. (Los Alamos, NM)

1980-01-01

119

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

2011-05-19

120

Transient liquid-phase infiltration of a powder-metal skeleton  

E-print Network

Transient Liquid-Phase Infiltration (TLI) is a new method for densifying a powder-metal skeleton that produces a final part of homogeneous composition without significant dimensional change, unlike traditional infiltration ...

Lorenz, Adam Michael, 1974-

2002-01-01

121

Mathematical Modeling and Numerical Simulation of Liquid-Solid and Solid-Liquid Phase Change  

E-print Network

region) between the solid and liquid phases in which the specific heat, density, thermal conductivity, and latent heat of fusion are continuous and differentiable functions of temperature. In the derivations of the mathematical models we assume the matter...

Joy, Aaron

2013-08-31

122

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

2006-04-01

123

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

Microsoft Academic Search

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

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

2012-01-01

124

Ultrasound promoted catalytic liquid-phase dehydrogenation of isopropanol for Isopropanol-Acetone-Hydrogen chemical heat pump.  

PubMed

The apparent kinetic of the ultrasound assisted liquid-phase dehydrogenation of isopropanol over Raney nickel catalyst was determined in the temperature range of 346-353K. Comparison of the effects of ultrasound and mechanical agitation on the isopropanol dehydrogenation was investigated. The ultrasound assisted dehydrogenation rate was significantly improved when relatively high power density was used. Moreover, the Isopropanol-Acetone-Hydrogen chemical heat pump (IAH-CHP) with ultrasound irradiation, in which the endothermic reaction is exposure to ultrasound, was proposed. A mathematical model was established to evaluate its energy performance in term of the coefficient of performance (COP) and the exergy efficiency, into which the apparent kinetic obtained in this work was incorporated. The operating performances between IAH-CHP with ultrasound and mechanical agitation were compared. The results indicated that the superiority of the IAH-CHP system with ultrasound was present even if more than 50% of the power of the ultrasound equipment was lost. PMID:25246094

Xu, Min; Xin, Fang; Li, Xunfeng; Huai, Xiulan; Liu, Hui

2015-03-01

125

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

SciTech Connect

The thermal conductivity, lambda, is one of the few transport coefficients which shows a relatively small change at the solid-liquid phase transition, and hence it is a property that can be used in comparing dynamic properties of both ordered and disordered systems. Although the discontinuity in lambda can be accounted for largely by the difference in density, /rho/, of solid and liquid at the phase transition, its volume dependence is examined more closely. The thermal diffusivity, which is known to dominate the dynamic structure factor of liquid argon, has been determined around the phase transition also; the sound velocity has been considered in addition. The results are discussed and a comparison is made with these properties in solid and liquid benzene and cyclohexane.

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

1986-01-01

126

Absorbance characteristics of a liquid-phase gas sensor based on gas-permeable liquid core waveguides.  

PubMed

The absorbance characteristics and influential factors on these characteristics for a liquid-phase gas sensor, which is based on gas-permeable liquid core waveguides (LCWs), are studied from theoretical and experimental viewpoints in this paper. According to theory, it is predicted that absorbance is proportional to the analyte concentration, sampling time, analyte diffusion coefficient, and geometric factor of this device when the depletion layer of the analyte is ignored. The experimental results are in agreement with the theoretical hypothesis. According to the experimental results, absorbance is time-dependent and increasing linearly over time after the requisite response time with a linear correlation coefficient r(2)>0.999. In the linear region, the rate of absorbance change (RAC) indicates improved linearity with sample concentration and a relative higher sensitivity than instantaneous absorbance does. By using a core liquid that is more affinitive to the analyte, reducing wall thickness and the inner diameter of the tubing, or increasing sample flow rate limitedly, the response time can be decreased and the sensitivity can be increased. However, increasing the LCW length can only enhance sensitivity and has no effect on response time. For liquid phase detection, there is a maximum flow rate, and the absorbance will decrease beyond the stated limit. Under experimental conditions, hexane as the LCW core solvent, a tubing wall thickness of 0.1 mm, a length of 10 cm, and a flow rate of 12 mL min(-1), the detection results for the aqueous benzene sample demonstrate a response time of 4 min. Additionally, the standard curve for the RAC versus concentration is RAC=0.0267c+0.0351 (AU min(-1)), with r(2)=0.9922 within concentrations of 0.5-3.0 mg L(-1). The relative error for 0.5 mg L(-1) benzene (n=6) is 7.4±3.7%, and the LOD is 0.04 mg L(-1). This research can provide theoretical and practical guides for liquid-phase gas sensor design and development based on a gas-permeable Teflon AF 2400 LCW. PMID:24267083

Peng, Pei; Wang, Wei; Zhang, Li; Su, Shiguang; Wang, Jiahui

2013-12-01

127

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

SciTech Connect

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

Not Available

1990-10-23

128

Statistical analysis of a liquid phase radioimmunoassay for immune complex determination.  

PubMed

A computer program is presented which enables iterative determination of the weighted standard curve and the quality control parameters calculation for the liquid phase radioimmunoassay which employs binding of labelled C1q as a measure of the presence of immunological complexes in serum samples. 22 independently performed laboratory tests were evaluated with respect to the presence of relationship between the dose (standardized human IgG aggregates) and response (fraction of radiolabelled C1q bound). On 14 occasions the plotted curve was sigmoidal in shape, the rest of the curves did not reach lower or upper asymptote. When the logistic transformation of this data was used the dose-response curve was linear and could be plotted with the use of the least square method. This allows calculation of the two other parameters of the sigmoidal curve (slope and midpoint). The slope of the weighted regression line, intercept point with the axis of ordinates and correlation coefficient were determined by means of the least square method for weighted linear regression with repetitions. When the iterative procedure was completed, content of immunological complexes in sera was calculated. The program is written in Fortran for the ODRA 1300 computer series. The printout consist of three parts. First part contains the original data, parameters and information about the form of input data. The second part of the printout consist of the results, obtained from non-weighted and weighted regression lines and the plotted regression line. The third part of the printout contains the final results of immune complexes determination. PMID:3490839

Laba, C; Haas, H; Jodkowski, J; Lange, A

1986-01-01

129

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

NASA Astrophysics Data System (ADS)

The oxidation of volatile organic compounds emitted in the atmosphere involves complex reaction mechanisms which leads to the formation of oxygenated organic intermediates, usually denoted as secondary organics. The fate of these secondary organics remains poorly quantified due to a lack of information about their speciation, distribution and evolution in the gas and condensed phases. A significant fraction of secondary organics may dissolve into the tropospheric aqueous phase owing to the presence of polar moieties generated during the oxidation processes. The partitioning of organics between the gas and the aqueous atmospheric phases is usually described in the basis of Henry's law. Atmospheric models require a knowledge of the Henry's law coefficient (H) for every water soluble organic species described in the chemical mechanism. Methods that can predict reliable H values for the vast number of organic compounds are therefore required. We have compiled a data set of experimental Henry's law constants for compounds bearing functional groups of atmospheric relevance. This data set was then used to develop GROMHE, a structure activity relationship to predict H values based on a group contribution approach. We assessed its performance with two other available estimation methods. The results show that for all these methods the reliability of the estimates decreases with increasing solubility. We discuss differences between methods and found that GROMHE had greater prediction ability.

Raventos-Duran, Teresa; Valorso, Richard; Aumont, Bernard; Camredon, Marie

2010-05-01

130

Lab-scale experimental strategy for determining micropollutant partition coefficient and biodegradation constants in activated sludge.  

PubMed

The nitrifying/denitrifying activated sludge process removes several micropollutants from wastewater by sorption onto sludge and/or biodegradation. The objective of this paper is to propose and evaluate a lab-scale experimental strategy for the determination of partition coefficient and biodegradation constant for micropollutant with an objective of modelling their removal. Four pharmaceutical compounds (ibuprofen, atenolol, diclofenac and fluoxetine) covering a wide hydrophobicity range (log Kow from 0.16 to 4.51) were chosen. Dissolved and particulate concentrations were monitored for 4 days, inside two reactors working under aerobic and anoxic conditions, and under different substrate feed conditions (biodegradable carbon and nitrogen). We determined the mechanisms responsible for the removal of the target compounds: (i) ibuprofen was biodegraded, mainly under aerobic conditions by cometabolism with biodegradable carbon, whereas anoxic conditions suppressed biodegradation; (ii) atenolol was biodegraded under both aerobic and anoxic conditions (with a higher biodegradation rate under aerobic conditions), and cometabolism with biodegradable carbon was the main mechanism; (iii) diclofenac and fluoxetine were removed by sorption only. Finally, the abilities of our strategy were evaluated by testing the suitability of the parameters for simulating effluent concentrations and removal efficiency at a full-scale plant. PMID:25300180

Pomiès, M; Choubert, J M; Wisniewski, C; Miège, C; Budzinski, H; Coquery, M

2014-10-11

131

Biodegradation of 4-chlorophenol by acclimated and unacclimated activated sludge-Evaluation of biokinetic coefficients  

SciTech Connect

Unacclimated and acclimated activated sludges were examined for their ability to degrade 4-CP (4-chlorophenol) in the presence and absence of a readily growing substrate using aerobic batch reactors. The effects of 4-CP on the {mu} (specific growth rate), COD removal efficiency, Y (yield coefficient), and q (specific substrate utilization rate) were investigated. It was observed that the toxicity of 4-CP on the culture decreased remarkably after acclimation. For example, the IC{sub 50} value on the basis of {mu} was found to increase from 130 to 218mg/L with the acclimation of the culture. Although an increase in 4-CP concentration up to 300mg/L has no adverse effect on the COD removal efficiency of the acclimated culture, a considerable decrease was observed in the case of an unacclimated culture. Although 4-CP removal was not observed with an unacclimated culture, almost complete removal was achieved with the acclimated culture, up to 300mg/L. The Haldane kinetic model adequately predicted the biodegradation of 4-CP and the kinetic constants obtained were q{sub m}=41.17mg/(gMLVSSh), K{sub s}=1.104mg/L, and K{sub i}=194.4mg/L. The degradation of 4-CP led to formation of 5-chloro-2-hydroxymuconic semialdehyde, which was further metabolized, indicating complete degradation of 4-CP via a meta-cleavage pathway.

Sahinkaya, Erkan [Department of Environmental Engineering, Middle East Technical University, Inonu Bulvari, 06531 Ankara (Turkey); Dilek, Filiz B. [Department of Environmental Engineering, Middle East Technical University, Inonu Bulvari, 06531 Ankara (Turkey)]. E-mail: fdilek@metu.edu.tr

2005-10-01

132

[Analysis of emodin and its metabolites based on hollow fiber liquid phase microextraction].  

PubMed

Hollow fiber liquid phase microextraction (HFLPME) coupled with high performance liquid chromatography (HPLC) has been developed to analyze the emodin and its metabolites in plasma and urine samples. The abilities of the absorption and metabolism for the active components in traditional Chinese medicines between the male and female rats were compared, and the biological metabolism and transmutation of the analyte were detailed discussed. Emodin and its metabolites in plasma and urine samples were extracted into n-octanol (acceptor) in hollow fiber. The acceptor phase was dried and dissolved by 50 microL methanol and then analyzed by HPLC. Under the optimal conditions, the linearities of the analytes were all very good in biological samples (r > 0.9960), the detection limits of the analytes were within the ranges of 0.1-3.0 microg/L. The enrichment factors were 12.2 to 26.3. The relative standard deviations for intra-day and inter-day precision were lower than 11.0%. The average recoveries of the analytes in plasma and urine samples were all in the range of 97.9% to 103%. HFLPME-HPLC can eliminate interference from complex biological samples, improve the sensitivity and reduce the detection limit, thus this method is suitable for the determination of trace compounds in complex sample. PMID:22934415

Tian, Jie; Chen, Xuan; Bai, Xiaohong

2012-05-01

133

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

134

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

SciTech Connect

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

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

2010-10-15

135

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

PubMed Central

A novel class of metal organic frameworks (MOFs) has been synthesized from Cu-acetate and dicarboxylic acids using liquid phase epitaxy. The SURMOF-2 isoreticular series exhibits P4 symmetry, for the longest linker a channel-size of 3 × 3?nm2 is obtained, one of the largest values reported for any MOF so far. High quality, ab-initio electronic structure calculations confirm the stability of a regular packing of (Cu++)2- carboxylate paddle-wheel planes with P4 symmetry and reveal, that the SURMOF-2 structures are in fact metastable, with a fairly large activation barrier for the transition to the bulk MOF-2 structures exhibiting a lower, twofold (P2 or C2) symmetry. The theoretical calculations also allow identifying the mechanism for the low-temperature epitaxial growth process and to explain, why a synthesis of this highly interesting, new class of high-symmetry, metastable MOFs is not possible using the conventional solvothermal process. PMID:23213357

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

2012-01-01

136

Liquid phase epitaxy centrifuge for growth of ultrapure gallium arsenide for far-infrared photoconductors  

NASA Astrophysics Data System (ADS)

Gallium arsenide extrinsic photoconductive detectors offer an extended spectral response in the far infrared (FIR) compared to presently available photodetectors, with the possibility of wavelength coverage from 60 to 300 mm. They can also be made in large planar structures, making them attractive for various far-infrared astronomical applications. In the past, continuous progress in material research has led to the production of pure, lightly and heavily doped n-type GaAs layers using liquid phase epitaxy (LPE). Sample detectors demonstrated the expected infrared characteristics of bulk type devices. Considerable improvement of detector performance could be expected from development of blocked impurity band (BIB) devices. These multi-structured detector types provide enhanced IR absorption and sensitivity due to the attainable higher doping of the infrared sensitive layer. However, the dark current in BIB detectors is determined by the level of unintentional majority doping for the relatively thin blocking layer, thus requiring ultra-high purity GaAs. With a new technique, using centrifugal forces for the LPE material growth, we intend to achieve this goal. Recently, such a growth facility has become operational at UC Berkeley. Outside contamination during the LPE growth process is largely reduced by a suspension of the crucible on active magnetic bearings in a completely closed environment. A sequential combination of centrifugal and gravitational forces provides the proper transport of the Ga solution in the growth crucible. Technical details of this unique equipment and first results of the initial growth runs will be reported.

Katterloher, Reinhard O.; Jakob, Gerd; Konuma, Mitsuharu; Krabbe, Alfred; Haegel, Nancy M.; Samperi, S. A.; Beeman, Jeffrey W.; Haller, Eugene E.

2002-02-01

137

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

SciTech Connect

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

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

2005-07-15

138

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

139

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. PMID:22847443

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

140

Measurements of liquid phase residence time distributions in a pilot-scale continuous leaching reactor using radiotracer technique.  

PubMed

An alkaline based continuous leaching process is commonly used for extraction of uranium from uranium ore. The reactor in which the leaching process is carried out is called a continuous leaching reactor (CLR) and is expected to behave as a continuously stirred tank reactor (CSTR) for the liquid phase. A pilot-scale CLR used in a Technology Demonstration Pilot Plant (TDPP) was designed, installed and operated; and thus needed to be tested for its hydrodynamic behavior. A radiotracer investigation was carried out in the CLR for measurement of residence time distribution (RTD) of liquid phase with specific objectives to characterize the flow behavior of the reactor and validate its design. Bromine-82 as ammonium bromide was used as a radiotracer and about 40-60MBq activity was used in each run. The measured RTD curves were treated and mean residence times were determined and simulated using a tanks-in-series model. The result of simulation indicated no flow abnormality and the reactor behaved as an ideal CSTR for the range of the operating conditions used in the investigation. PMID:25528019

Pant, H J; Sharma, V K; Shenoy, K T; Sreenivas, T

2015-03-01

141

Liquid phase esterification of acetic acid over WO3 promoted ?-SiC in a solvent free system.  

PubMed

A series of tungstate promoted ?-SiC catalysts was synthesized by a wetness impregnation method. The as synthesized catalysts were unambiguously characterized by XRD, Raman, FTIR, XPS, UV-Vis DRS, TEM, BET surface areas and FE-SEM, and simultaneously the total amount of the acidity of the catalysts was estimated by NH(3)-TPD. The catalytic activities of the synthesized materials were tested in the liquid phase esterification of acetic acid with n-butanol in a solvent free medium. The reaction parameters were optimized to a temperature of 120 °C, molar ratio of butanol and acetic acid of 1:2 and a reaction time of 6 h after performing a number of experiments. Under the optimum conditions, the catalytic esterification revealed a significant effect of 88% conversion with 100% selectivity to butyl acetate in 20 wt% WO(3)/?-SiC. This is the first report on the effective utilization of ?-SiC as a catalyst support for liquid phase esterification of acetic acid. PMID:23042240

Mishra, Gopa; Behera, Gobinda C; Singh, S K; Parida, K M

2012-12-21

142

Active and Passive Elec. Comp., September 2003, Vol. 26, pp. 151166 ULTRA-LOW TEMPERATURE COEFFICIENT OF  

E-print Network

Active and Passive Elec. Comp., September 2003, Vol. 26, pp. 151­166 ULTRA-LOW TEMPERATURE that this material system possessed low dielectric constant and ultra-low temperature coefficient of capacitance (TCC metastannate; Capacitor component; Electroceramics; Dielectrics; Complex plane analysis; Temperature

Azad, Abdul-Majeed

143

Gamma-ray spectra of hexane in gas phase and liquid phase  

E-print Network

Theoretical gamma-ray spectra of molecule hexane have been calculated and compared with the experimental results in both gas (Surko et al, 1997) and liquid (Kerr et al, 1965) phases. The present study reveals that in gas phase not all valence electrons of hexane exhibit the same probability to annihilate a positron. Only the positrophilic electrons in the valence space dominate the gamma-ray spectra, which are in good agreement with the gas phase measurement. When hexane is confined in liquid phase, however, the intermolecular interactions ultimately eliminate the free molecular orientation and selectivity for the positrophilic electrons in the gas phase. As a result, the gamma-ray spectra of hexane become an averaged contribution from all valence electrons, which is again in agreement with liquid phase measurement. The roles of the positrophilic electrons in annihilation process for gas and liquid phases of hexane have been recognized for the first time in the present study.

Ma, Xiaoguang

2012-01-01

144

Gamma-ray spectra of hexane in gas phase and liquid phase  

E-print Network

Theoretical gamma-ray spectra of molecule hexane have been calculated and compared with the experimental results in both gas (Surko et al, 1997) and liquid (Kerr et al, 1965) phases. The present study reveals that in gas phase not all valence electrons of hexane exhibit the same probability to annihilate a positron. Only the positrophilic electrons in the valence space dominate the gamma-ray spectra, which are in good agreement with the gas phase measurement. When hexane is confined in liquid phase, however, the intermolecular interactions ultimately eliminate the free molecular orientation and selectivity for the positrophilic electrons in the gas phase. As a result, the gamma-ray spectra of hexane become an averaged contribution from all valence electrons, which is again in agreement with liquid phase measurement. The roles of the positrophilic electrons in annihilation process for gas and liquid phases of hexane have been recognized for the first time in the present study.

Xiaoguang Ma; Feng Wang

2012-11-01

145

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

PubMed

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

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

2014-04-01

146

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

SciTech Connect

he 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 LPMEOEP Process Demonstration Unit was built at a site located at the Eastman coal-to-chemicals complex in Kingsport. The LPMEOHW Demonstration Facility completed its first year of operation on 02 April 1998. The LPMEOW Demonstration Facility also completed the longest continuous operating run (65 days) on 21 April 1998. 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 laboratory autoclave), was monitored throughout the reporting period. During a six-week test at a reactor temperature of 225oC and Balanced Gas flowrate of 700 KSCFH, the rate of decline in catalyst activity was steady at 0.29-0.36% per day. During a second one-month test at a reactor temperature of 220oC and a Balanced Gas flowrate of 550-600 KSCFH, the rate of decline in catalyst activity was 0.4% per day, which matched the pefiorrnance at 225"C, as well as the 4-month proof-of-concept run at the LaPorte AFDU in 1988/89. Beginning on 08 May 1998, the LPMEOW Reactor temperature was increased to 235oC, which was the operating temperature tier the December 1997 restart with the fresh charge of catalyst (50'Yo of design loading). The flowrate of the primary syngas feed stream (Balanced Gas) was also increased to 700-750 KSCFH. During two stable operating periods between 08 May and 09 June 1998, the average catalyst deactivation rate was 0.8% per day. Due to the scatter of the statistical analysis of the results, this test was extended to better quanti& the catalyst aging behavior. During the reporting perio~ two batches of fresh catalyst were activated and transferred to the reactor (on 02 April and 20 June 1998). The weight of catalyst in the LPMEOW Reactor has reached 80% of the design value. At the end of the reporting period, a step-change in the pressure-drop profile within the LPMEOW Reactor and an increase in the pressure of the steam system which provides cooling to the LPMEOW Reactor were observed. No change in the calculated activity of the catalyst was detected during either of these transients. These parameters will be monitored closely for any additional changes.

None

1998-12-21

147

Primitive model electrolytes. A comparison of the HNC approximation for the activity coefficient with Monte Carlo data  

E-print Network

Accuracy of the mean activity coefficient expression (Hansen-Vieillefosse-Belloni equation), valid within the hypernetted chain (HNC) approximation, was tested in a wide concentration range against new Monte Carlo (MC) data for +1:-1 and +2:-2 primitive model electrolytes. The expression has an advantage that the excess chemical potential can be obtained directly, without invoking the time consuming Gibbs-Duhem calculation. We found the HNC results for the mean activity coefficient to be in good agreement with the machine calculations performed for the same model. In addition, the thermodynamic consistency of the HNC approximation was tested. The mean activity coefficients, calculated via the Gibbs-Duhem equation, seem to follow the MC data slightly better than the Hansen-Vieillefosse-Belloni expression. For completeness of the calculation, the HNC excess internal energies and osmotic coefficients are also presented. These results are compared with the calculations based on other theories commonly used to describe electrolyte solutions, such as the mean spherical approximation, Pitzer's extension of the Debye-H\\"uckel theory, and the Debye-H\\"uckel limiting law.

E. Gutiérrez-Valladares; M. Luksic; B. Millán-Malo; B. Hribar-Lee; V. Vlachy

2012-02-20

148

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

149

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

150

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

151

Cu-Bi as a Model System For Liquid Phase Sintered Thermal Interface Management Materials  

E-print Network

Cu-Bi as a Model System For Liquid Phase Sintered Thermal Interface Management Materials P and respective thermal conductivity Heat Sink Si Device TIMHEAT HEAT Heat Sink Si Device TIM Heat Sink Si Device TIM 1) High thermal conductivity to conduct heat from silicon device to heat sink 2) High compliance

Collins, Gary S.

152

Critical fluctuations in electrolytes with a liquid-liquid phase transition  

Microsoft Academic Search

Near-critical fluctuations of ionic solutions with a liquid-liquid phase transition are investigated by measurements of turbidity and static and dynamic light scattering. Phase diagrams are also presented. The systems are substituted ammonium salts (picrate, nitrate, iodide) dissolved in higher alcohols and water. The correlation lengths, determined from the time correlation functions using the Kawasaki mode coupling theory, also describe the

W. Schroer; S. Wiegand; M. Kleemeier; H. Weingartner

1994-01-01

153

Critical behaviour of ionic solutions in non-polar solvents with a liquid - liquid phase transition  

Microsoft Academic Search

Turbidity measurements showing crossover from mean-field to Ising criticality have been reported by Narayanan and Pitzer for the liquid - liquid phase transition in ionic solutions of alkyl-ammonium picrates in higher alcohols. The Ising region was found to increase with the dielectric permittivity D for solvents with 4 < D < 8. It was conjectured that the Ising region becomes

W. Schröer; M. Kleemeier; M. Plikat; V. Weiss; S. Wiegand

1996-01-01

154

Liquid phase epitaxy of GaP by a temperature difference method under controlled vapor pressure  

Microsoft Academic Search

A series of experiments have been done in which the properties of GaP grown by liquid phase epitaxy (LPE) have been varied by providing an additional source of phosphorus via the vapor phase. The quality of the crystals, as judged from gross defect features observed in etched cross sections, is a function of the amount of phosphorus added to the

J. Nishizawa; Y. Okuno

1975-01-01

155

Finite difference computation of solid\\/liquid phase change energy transport - Comparison with experimental data  

Microsoft Academic Search

A computational model is presented for the prediction of solid\\/liquid phase change energy transport including the influence of free convection and comparisons made with experimental data for which the phase change material is heated from the side and from below. The computational model considers the velocity components of all nonliquid PCM control volumes to be zero but fully solves the

G. E. Schneider

1986-01-01

156

Ultrahigh-vacuum chamber equipped with a reaction cell for studying liquid-phase catalytic reactions  

NASA Astrophysics Data System (ADS)

We describe the construction and operation of a liquid-phase reaction cell designed in our laboratory that is attached to an ultrahigh-vacuum (UHV) chamber equipped with the traditional surface science techniques for structure and composition analysis. The sample surface can be prepared and characterized in the UHV chamber prior to transfer in the liquid-phase reaction cell. The transfer has been designed so that there is no loss of the UHV chamber vacuum integrity, as few parts as possible come into contact with the liquid, the surface stays clean during the transfer. The liquid-phase reaction cell itself is designed to study liquid-phase hydrogenation reactions at pressures up to 2 atm and temperatures up to 70 °C. A 1-mm-diam liquid jet with a velocity up to 6 m/s is produced by a gear pump that is incident on the sample surface to allow good mass transfer at the liquid-solid interface. The progress of the reaction is followed by gas chromatography. We report the reaction rate data for the hydrogenation of cyclohexene on a platinum foil.

Gardin, Denis E.; Somorjai, Gabor A.

1993-05-01

157

Ultrahigh-vacuum chamber equipped with a reaction cell for studying liquid-phase catalytic reactions  

SciTech Connect

We describe the construction and operation of a liquid-phase reaction cell designed in our laboratory that is attached to an ultrahigh-vacuum (UHV) chamber equipped with the traditional surface science techniques for structure and composition analysis. The sample surface can be prepared and characterized in the UHV chamber prior to transfer in the liquid-phase reaction cell. The transfer has been designed so that there is no loss of the UHV chamber vacuum integrity, as few parts as possible come into contact with the liquid, the surface stays clean during the transfer. The liquid-phase reaction cell itself is designed to study liquid-phase hydrogenation reactions at pressures up to 2 atm and temperatures up to 70 [degree]C. A 1-mm-diam liquid jet with a velocity up to 6 m/s is produced by a gear pump that is incident on the sample surface to allow good mass transfer at the liquid-solid interface. The progress of the reaction is followed by gas chromatography. We report the reaction rate data for the hydrogenation of cyclohexene on a platinum foil.

Gardin, D.E.; Somorjai, G.A. (Materials Sciences Division, Lawrence Berkeley Laboratory, and Department of Chemistry, University of California, Berkeley, California 94720 (United States))

1993-05-01

158

Non-equilibrium effects in the liquid-phase catalytic hydrogenation  

Microsoft Academic Search

Catalytic hydrogenation in the liquid-phase over supported metal catalysts at high hydrogen pressures can be described by the zero order in respect to all components. The reaction mechanism which involves formation of intermediate complexes including hydrogen and organic compound is discussed. The reaction rate in the region of zero orders is determined by the isomerisation rate of these complexes. Experimental

D. Yu. Murzin; N. V. Kul'kova

1995-01-01

159

Simplified thermodynamic functions for vapor-liquid phase separation and fountain effect pumps  

NASA Technical Reports Server (NTRS)

He-4 fluid handling devices near 2 K require novel components for non-Newtonian fluid transport in He II. Related sizing of devices has to be based on appropriate thermophysical property functions. The present paper presents simplified equilibrium state functions for porous media components which serve as vapor-liquid phase separators and fountain effect pumps.

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

1984-01-01

160

Sulfonation of Methane Direct Liquid-Phase Sulfonation of Methane to  

E-print Network

- radical initiator to sulfonate methane with SO3 in fuming sulfuric acid.[6] However, even with a methane that methane will undergo liquid-phase sulfonation with 30 wt% SO3 in sulfuric acid to form MSA, using metal methane. In a typical reaction CH4 and SO3 were allowed to react in fuming sulfuric acid in a high

Bell, Alexis T.

161

INFLUENCE OF NON-WETTING CONDITIONS ON AGGREGATION OF DIVIDED SOLIDS IN LIQUID PHASE  

E-print Network

INFLUENCE OF NON-WETTING CONDITIONS ON AGGREGATION OF DIVIDED SOLIDS IN LIQUID PHASE Michel Cournil of hydrophilic particles are small and fragile whereas aggregates of hydrophobic particles are large in aggregates. INTRODUCTION Aggregation of hydrophilic particles in stirred liquid media can be considered

Paris-Sud XI, Université de

162

CONTINENTAL LIQUID-PHASE STRATUS CLOUDS AT SGP: METEOROLOGICAL INFLUENCES AND RELATIONSHIP TO ADIABACITY  

E-print Network

CONTINENTAL LIQUID-PHASE STRATUS CLOUDS AT SGP: METEOROLOGICAL INFLUENCES AND RELATIONSHIP Laboratory P.O. Box, Upton, NY www.bnl.gov ABSTRACT The microphysical properties of continental stratus continental boundary layer stratus clouds are subadiabatic, as for the most part they are influenced

163

Solid-liquid phase coexistence and structural transitions in palladium clusters  

Microsoft Academic Search

We use molecular dynamics with an embedded atom potential to study the behavior of palladium nanoclusters near the melting point in the microcanonical ensemble. We see transitions from both fcc and decahedral ground-state structures to icosahedral structures prior to melting over a range of cluster sizes. In all cases this transition occurs during solid-liquid phase coexistence and the mechanism for

D. Schebarchov; S. C. Hendy

2006-01-01

164

Heat exchange and preheater for the 700-atm liquid-phase chamber, Hydrierwerk Blechhammer  

Microsoft Academic Search

Advantages and disadvantages of several possible patterns for heat exchange to be used at Blechhammer and their effects on preheating of coal paste are discussed. The report was apparently based on experimental work done at Ludwigshafen. The various possibilities were appropriate for a 700-atm liquid-phase chamber operating on coal paste. If only gasoline were to be produced, the alternatives considered

Schappert

1940-01-01

165

Analytical study of the liquid phase transient behavior of a high temperature heat pipe  

Microsoft Academic Search

The transient operation of the liquid phase of a high temperature heat pipe is studied. The study was conducted in support of advanced heat pipe applications that require reliable transport of high temperature drops and significant distances under a broad spectrum of operating conditions. The heat pipe configuration studied consists of a sealed cylindrical enclosure containing a capillary wick structure

Gregory Lawrence Roche

1988-01-01

166

Microstructure and mechanical response of transient liquid phase joint in Haynes 282 superalloy  

Microsoft Academic Search

Microstructure and mechanical response of transient liquid phase joint in a newly developed nickel-based superalloy, Haynes 282, was studied. Insufficient holding time for complete isothermal solidification of liquated insert resulted in the formation of eutectic solidification product along the joint centreline region. Micro-hardness test showed that the eutectic is extremely hard, and it provides an easy preferential path for crack

A. Ghoneim; O. A. Ojo

2011-01-01

167

Numerical modelling of transient liquid phase bonding and other diffusion controlled phase changes  

Microsoft Academic Search

Diffusion in material of inhomogeneous composition can induce phase changes, even at a constant temperature. A transient liquid phase (TLP), in which a liquid layer is formed and subsequently solidifies, is one example of such an isothermal phase change. This phenomenon is exploited industrially in TLP bonding and sintering processes. Successful processing requires an understanding of the behaviour of the

T. C. I LLINGWORTH; I. O. GOLOSNOY; T. W. C LYNE

2005-01-01

168

Liquid phase hydrogenation of citral: suppression of side reactions  

Microsoft Academic Search

Selective hydrogenation of citral was investigated at 70°C in four different alcohols over Ru, Rh and Ni supported catalysts. The main aim was to suppress the side reaction, like acetalization and cyclization of citronellal. Acetalization could be suppressed either by using chloride-free catalyst precursors and other supports than active carbon or by using longer chained alcohols, like 2-pentanol and 2-methyl-2-propanol

Päivi Mäki-Arvela; Lasse-Pekka Tiainen; Ahmad Kalantar Neyestanaki; Rainer Sjöholm; Tiina-Kaisa Rantakylä; Ensio Laine; Tapio Salmi; Dmitry Yu Murzin

2002-01-01

169

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

NASA Astrophysics Data System (ADS)

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

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

2013-06-01

170

High quality indium gallium arsenide phosphide double heterostructure material grown by the near equilibrium liquid-phase-epitaxy technique  

NASA Astrophysics Data System (ADS)

A comparative study of the source seed and near equilibrium liquid-phase epitaxy (LPE) growth techniques is described. The results of such important characteristics as broad area laser thresholds, quaternary active layer mismatch, and photoluminescence peak wavelength for 1.3-?m InGaAsP double heterostructure material were compared. Double heterostructure material grown by the near equilibrium LPE growth technique exhibited a better overall quality. Moreover, run to run reproducibility of these same parameters, as well as their eventual intrawafer variability, were monitored over an extended period of time. Again, the near equilibrium LPE growth technique readily led to excellent quality double heterostructure material. Finally, these wafers were processed into oxide stripe gain guided lasers, having a high percentage of devices with acceptable electro-optical characteristics.

Besomi, P.; Degani, J.; Dutta, N. K.; Wagner, W. R.; Nelson, R. J.

1984-11-01

171

Pore mouth versus intracrystalline adsorption of isoalkanes on ZSM-22 and ZSM-23 zeolites under vapour and liquid phase conditions.  

PubMed

Methylbranched C5-C9 alkanes do not adsorb in the intracrystalline void space of ZSM-23, neither from the vapour nor the liquid phase, but are adsorbed in ZSM-22, if only from the liquid phase, and this despite the small difference in pore size. PMID:12932013

Denayer, J F; Ocakoglu, A R; Huybrechts, W; Martens, J A; Thybaut, J W; Marin, G B; Baron, G V

2003-08-01

172

Highly reliable nickel-tin transient liquid phase bonding technology for high temperature operational power electronics in electrified vehicles  

Microsoft Academic Search

This paper presents an approach to nickel-tin transient liquid phase (TLP) bonding that provides high reliability for high temperature operational power electronics in electrified vehicles. The need for automotive power electronics to operate at high temperature presents significant challenges in terms of the packaging and bonding technology used. Transient liquid phase (TLP) bonding is one attachment approach that addresses these

Sang Won Yoon; Koji Shiozaki; Satoshi Yasuda; Michael D. Glover

2012-01-01

173

Effervescence assisted on-site liquid phase microextraction for the determination of five triazine herbicides in water.  

PubMed

A novel effervescence assisted on-site liquid phase microextraction has been developed for the determination of five triazine herbicides in water. The use of an effervescent tablet composed of citric acid, sodium bicarbonate and 1-undecanol (extraction solvent) was the core of the method. The triazine herbicides in water were extracted by 1-undecanol released from tablet under effervescence and determined by ultra-high pressure liquid chromatography tandem mass spectrometer. The experimental variables, including NaCl concentration, temperature, weight of effervescent tablet, volume of extraction solvent and pH value, were screened by a Plackett-Burman design and optimized by a Box-Behnken design. Under the optimized conditions, good linearity was obtained in the range of 0.05-10 ?g L(-1) with correlation coefficients ranging from 0.9936 to 0.9988. The limits of quantification were between 7.6 and 26.4 ng L(-1), and the recoveries were in 71.4-93.2% with relative standard deviations of 2.5-10.9%. This method, which does not require centrifugation and any special apparatus, was successfully applied to determine triazine herbicides in real waters, promising to be a way to speed field sampling procedures for the organic pollutants monitoring in water. PMID:25456587

Liu, Xueke; Shen, Zhigang; Wang, Peng; Liu, Chang; Zhou, Zhiqiang; Liu, Donghui

2014-12-01

174

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

SciTech Connect

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

Bandaru, Jordana

2001-05-12

175

Formation of Fermi surfaces and the appearance of liquid phases in holographic theories with hyperscaling violation  

NASA Astrophysics Data System (ADS)

We consider a holographic fermionic system in which the fermions are interacting with a U(1) gauge field in the presence of a dilaton field in a gravity bulk of a charged black hole with hyperscaling violation. Using both analytical and numerical methods, we investigate the properties of the infrared and ultaviolet Green's functions of the holographic fermionic system. Studying the spectral functions of the system, we find that as the hyperscaling violation exponent is varied, the fermionic system possesses Fermi, non-Fermi, marginal-Fermi and log-oscillating liquid phases. Various liquid phases of the fermionic system with hyperscaling violation are also generated with the variation of the fermionic mass. We also explore the properties of the flat band and the Fermi surface of the non-relativistic fermionic fixed point dual to the hyperscaling violation gravity.

Kuang, Xiao-Mei; Papantonopoulos, Eleftherios; Wang, Bin; Wu, Jian-Pin

2014-11-01

176

Solid-liquid phase equilibria of the Gaussian core model fluid  

NASA Astrophysics Data System (ADS)

The solid-liquid phase equilibria of the Gaussian core model are determined using the GWTS [J. Ge, G.-W. Wu, B. D. Todd, and R. J. Sadus, J. Chem. Phys. 119, 11017 (2003)] algorithm, which combines equilibrium and nonequilibrium molecular dynamics simulations. This is the first reported use of the GWTS algorithm for a fluid system displaying a reentrant melting scenario. Using the GWTS algorithm, the phase envelope of the Gaussian core model can be calculated more precisely than previously possible. The results for the low-density and the high-density (reentrant melting) sides of the solid state are in good agreement with those obtained by Monte Carlo simulations in conjunction with calculations of the solid free energies. The common point on the Gaussian core envelope, where equal-density solid and liquid phases are in coexistence, could be determined with high precision.

Mausbach, Peter; Ahmed, Alauddin; Sadus, Richard J.

2009-11-01

177

Solid-liquid phase equilibria of the Gaussian core model fluid.  

PubMed

The solid-liquid phase equilibria of the Gaussian core model are determined using the GWTS [J. Ge, G.-W. Wu, B. D. Todd, and R. J. Sadus, J. Chem. Phys. 119, 11017 (2003)] algorithm, which combines equilibrium and nonequilibrium molecular dynamics simulations. This is the first reported use of the GWTS algorithm for a fluid system displaying a reentrant melting scenario. Using the GWTS algorithm, the phase envelope of the Gaussian core model can be calculated more precisely than previously possible. The results for the low-density and the high-density (reentrant melting) sides of the solid state are in good agreement with those obtained by Monte Carlo simulations in conjunction with calculations of the solid free energies. The common point on the Gaussian core envelope, where equal-density solid and liquid phases are in coexistence, could be determined with high precision. PMID:19916612

Mausbach, Peter; Ahmed, Alauddin; Sadus, Richard J

2009-11-14

178

Selective growth of GaN by liquid phase electroepitaxy using aluminum oxide mask  

NASA Astrophysics Data System (ADS)

Aluminum oxide was investigated as a mask material for the selective growth of GaN by liquid phase electroepitaxy in comparison with SiO2, SiN, and W. SiO2 and W masks were dissolved in a solution and many polycrystals were generated on the SiN mask. Therefore, these masks are not suitable for selective growth. On the other hand, aluminum oxide was found durable in the solution, and growth selectivity was also achieved. Then, microchannel epitaxy was conducted using the aluminum mask by liquid phase electroepitaxy. Not only the selective growth but also the lateral growth of c-plane GaN with a width of about 8 µm was successfully achieved using the aluminum oxide mask.

Kambayashi, Daisuke; Takakura, Hiroyuki; Tomita, Masafumi; Iwakawa, Muneki; Mizuno, Yosuke; Yamada, Jumpei; Maruyama, Takahiro; Naritsuka, Shigeya

2014-11-01

179

Speed of Sound in the Liquid Phase of the R134a/152a Refrigerant Blend  

NASA Astrophysics Data System (ADS)

The speed of sound in the liquid phase of the binary blend of R134a and R152a and its components has been studied. The speed of sound was measured by means of the impulse method at a frequency of 2.1 MHz. The temperature range was 230 to 350 K at pressures up to 16 MPa. The values of speed of sound were measured with a standard error of not more than 0.25%. The results obtained for both components of the blend are represented with expressions based on a physical model. The standard deviation (versus the model) of the measured data is 0.09%, On the basis of the results obtained, the Redlich-Kister correlation has been used over the entire ranges of composition, temperature, and pressure to determine the speed of sound in the liquid phase and at the bubble point of the blend investigated.

Beliajeva, O. V.; Grebenkov, A. J.; Zajatz, T. A.; Timofejev, B. D.

1999-11-01

180

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

PubMed

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

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

2006-09-01

181

Computation of heat transfer with solid\\/liquid phase change including free convection  

Microsoft Academic Search

A computational model is presented for the prediction of solid\\/liquid phase change energy transport including the influence of free convection. The computational model considers the velocity components of all nonliquid PCM control volumes to be zero but fully solves the coupled mass-momentum problem within the liquid. The thermal energy model includes the entire domain and employs an enthalpy-like model in

G. E. Schneider

1985-01-01

182

Reaction kinetics of the liquid-phase hydrogenation of benzonitrile to benzylamine using Raney nickel catalyst  

Microsoft Academic Search

The liquid-phase catalytic hydrogenation of benzonitrile to benzylamine was carried out in 2-propanol using Raney nickel as a catalyst. The effects of hydrogen partial pressure (500–2000kPa), reaction temperature (328–358K), catalyst loading (2–8gdm?3), benzonitrile concentration (0.4–1.6moldm?3) and additives (acetic acid, water and liquor ammonia) on the hydrogenation of benzonitrile and the yield of benzylamine have been studied. The speed of stirring

Sunil P. Bawane; Sudhirprakash B. Sawant

2004-01-01

183

Kinetics of the catalytic liquid-phase hydrogenation of aqueous nitrate solutions  

Microsoft Academic Search

Liquid-phase reduction using a solid Pd\\/Cu bimetallic catalyst provides a potential technique for the removal of nitrates from waters. Kinetic measurements were performed for a wide range of reactant concentrations and reaction conditions in an isothermal semi-batch slurry reactor operating at atmospheric pressure. The effects of catalyst loading and initial nitrate concentration on the reaction rate were also investigated. The

Albin Pintar; Jurka Batista; Janez Levec; Toshio Kajiuchi

1996-01-01

184

Space cryogenics components based on the thermomechanical effect - Vapor-liquid phase separation  

NASA Technical Reports Server (NTRS)

Applications of the thermomechanical effect has been qualified including incorporation in large-scale space systems in the area of vapor-liquid phase separation (VLPS). The theory of the porous-plug phase separator is developed for the limit of a high thermal impedance of the solid-state grains. Extensions of the theory of nonlinear turbulent flow are presented based on experimental results.

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

1989-01-01

185

Sintered plug flow modulation of a vapor-liquid phase separator for a helium II vessel  

NASA Technical Reports Server (NTRS)

Presented is a system for modulation of a superfluid (helium II) flow in a vapor-liquid phase separator, for use in cryogenic storage tanks in future space missions. The system consists of a semicircular mechanically operated shutter, downstream of the separator plug, rotated at 0.1 rpm to control the operational surface area of the separator. The mass flow rate was varied from 10 to 22 mg/s. Pressure gradients across the plug are also discussed.

Frederking, T. H. K.; Chuang, C.; Kamioka, Y.; Lee, J. M.; Yuan, S. W. K.

1984-01-01

186

Liquid-phase impact diffusion welding of SiC p\\/6061Al and its mechanism  

Microsoft Academic Search

Liquid-phase impact diffusion welding (LPIDW) technique was used to join the aluminum matrix composite SiCp\\/6061Al. The composite joints welded successfully, gave tensile strength up to 260MPa and radial deformation below 3%. Analysis of the microstructure and tensile strength of the welded joints showed: (i) the achievement of prominent joint interface between SiC particles and the matrix; (ii) the change of

Wei Guo; Meng Hua; Hang Wai Law; John Kin Lim Ho

2008-01-01

187

Study on liquid-phase-impact diffusion welding SiC p\\/ZL101  

Microsoft Academic Search

A new method for welding SiCp\\/ZL101, liquid-phase-impact diffusion welding (LPIDW), was put forward. The effect of LPIDW parameters on the welded joint property was investigated, and the optimal welding parameters were brought forward at the same time. The microstructure of joint was analyzed by means of scanning electron microscope and transmission electron microscope in order to study the relationship between

Wei Guo; Meng Hua; John Kin Lim Ho

2007-01-01

188

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

NASA Technical Reports Server (NTRS)

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

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

2004-01-01

189

Barium Hexaferrite Thick Films Made by Liquid Phase Epitaxy Reflow Method  

Microsoft Academic Search

In this paper, we report on the growth of BaFe12O19 (BaM) thick films on sapphire Al2 O3 (0001) substrate. Our goal is to fabricate barium ferrite thick films which can be self-biased for circulator applications. We have modified the liquid phase epitaxy (LPE) method by conducting the experiment in vacuum. A small piece of the melt weighing approximately 0.035 g

Yanko A. Kranov; Allaedeen Abuzir; Tejashvi Prakash; David N. McIlroy; Wei J. Yeh

2006-01-01

190

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

Microsoft Academic Search

Tungsten heavy alloys with compositions ranging from 78 to 98 wt pct tungsten were liquid phase sintered at 1507 C under\\u000a microgravity conditions for 120 minutes. The sintered microstructures were quantitatively measured for solid volume fraction,\\u000a grain size, connectivity, and contiguity. Links between these microstructural parameters were analyzed and compared to previously\\u000a derived empirical equations. The macrostructures of the samples

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

1998-01-01

191

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

192

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

193

Transient liquid phase metallic bonding of an Inconel 718SPF superalloy  

Microsoft Academic Search

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

M. S. Yeh; T. H. Chuang

1997-01-01

194

Application of the transient liquid phase bonding to microelectronics and MEMS packaging  

Microsoft Academic Search

For high performance microelectronics and MEMS packaging, ceramic-based packages are preferred over plastics. There are a number of ways that ceramic-to-metal joining is of important concern in such applications. In this paper, the partial transient liquid phase bonding (PTLPB) method for ceramic-to-metal joining is reviewed. This method does not require high joining pressure and stringent surface preparation for cleanliness as

Jin-Woo Park; Thomas W. Eagar

2002-01-01

195

Gravity and configurational energy induced microstructural changes in liquid phase sintering  

NASA Technical Reports Server (NTRS)

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

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

1988-01-01

196

The liquid-liquid phase transition in silicon revealed by snapshots of valence electrons  

PubMed Central

The basis for the anomalies of water is still mysterious. Quite generally tetrahedrally coordinated systems, also silicon, show similar thermodynamic behavior but lack—like water—a thorough explanation. Proposed models—controversially discussed—explain the anomalies as a remainder of a first-order phase transition between high and low density liquid phases, buried deeply in the “no man’s land”—a part of the supercooled liquid region where rapid crystallization prohibits any experimental access. Other explanations doubt the existence of the phase transition and its first-order nature. Here, we provide experimental evidence for the first-order-phase transition in silicon. With ultrashort optical pulses of femtosecond duration we instantaneously heat the electronic system of silicon while the atomic structure as defined by the much heavier nuclear system remains initially unchanged. Only on a picosecond time scale the energy is transferred into the atomic lattice providing the energy to drive the phase transitions. With femtosecond X-ray pulses from FLASH, the free-electron laser at Hamburg, we follow the evolution of the valence electronic structure during this process. As the relevant phases are easily distinguishable in their electronic structure, we track how silicon melts into the low-density-liquid phase while a second phase transition into the high-density-liquid phase only occurs after the latent heat for the first-order phase transition has been transferred to the atomic structure. Proving the existence of the liquid-liquid phase transition in silicon, the hypothesized liquid-liquid scenario for water is strongly supported. PMID:20805512

Beye, Martin; Sorgenfrei, Florian; Schlotter, William F.; Wurth, Wilfried; Föhlisch, Alexander

2010-01-01

197

Enhanced particle rearrangement during liquid phase spark plasma sintering of silicon nitride-based ceramics  

Microsoft Academic Search

Densification evolution has been analysed in liquid phase assisted spark plasma sintering (SPS) of silicon nitride (Si3N4)-based materials. Monolithic ceramics with variable amounts of Al2O3\\/Y2O3 sintering additives, and carbon nanotubes (CNTs) containing Si3N4 composites have been considered. The shrinkage behaviour of SPSed monolithic Si3N4 showed a noticeable enhancement of the particle rearrangement stage, exhibiting a complete wetting of the grain

Pilar Miranzo; Jesús González-Julián; María Isabel Osendi; Manuel Belmonte

2011-01-01

198

Determination of sintering parameters for liquid phase sintering of silicon nitride  

Microsoft Academic Search

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

Claire Theron

2008-01-01

199

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

200

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

PubMed

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

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

2014-01-01

201

Effect of Titanium Addition on the Thermal Properties of Diamond/Cu-Ti Composites Fabricated by Pressureless Liquid-Phase Sintering Technique  

PubMed Central

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

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

2014-01-01

202

Two-liquid phase partitioning biotrickling filters for methane abatement: Exploring the potential of hydrophobic methanotrophs.  

PubMed

The potential of two-liquid phase biotrickling filters (BTFs) to overcome mass transfer limitations derived from the poor aqueous solubility of CH4 has been scarcely investigated to date. In this context, the abatement of diluted methane emissions in two-liquid phase BTFs was evaluated using two different inocula: a type II methanotrophs culture in BTF 1 and a hydrophobic microbial consortium capable of growing inside silicone oil in BTF 2. Both BTFs supported stable elimination capacities above 45 g m(-3) h(-1) regardless of the inoculum, whereas no improvement derived from the presence of hydrophobic microorganisms compared to the type II metanotrophs culture was observed. Interestingly, the addition of silicone oil mediated a reduced metabolites concentration in the recycling aqueous phase, thus decreasing the needs for mineral medium renewal. Moreover, a 78% similarity was recorded between the microbial communities enriched in both BTFs at the end of the experimental period in spite of the differences in the initial inoculum structure. The results obtained confirmed the superior performance of two-liquid phase BTFs for CH4 abatement compared with conventional biotrickling filters. PMID:25555135

Lebrero, Raquel; Hernández, Laura; Pérez, Rebeca; Estrada, José M; Muñoz, Raúl

2015-03-15

203

Numerical simulation of grain size distributions in liquid phase sintered materials  

SciTech Connect

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 such as grain growth so that these materials may be engineered for their respective applications. Grain growth in liquid phase sintered materials by Ostwald ripening has been modeled extensively by both analytical and numerical techniques. However, all models make simplifying approximations to make the problem tractable and the approximations used in these models make them most accurate at very low solid fractions. A two-dimensional, Monte Carlo simulation technique based on the Potts model that makes no assumptions about solid fraction, grain shapes or diffusion fields around grains has been used to study grain growth in fully wetting, liquid phase sintered systems. The grain size distribution, GSD, was found to vary with solid fraction, becoming broader and more peaked with increasing solid fraction. The skewness was near zero at solid fraction of 0.41 and shifted to larger grain sizes with increasing solid fraction.

Tikare, V. [Sandia National Labs., Albuquerque, NM (United States); Cawley, J.D. [Case Western Reserve Univ., Cleveland, OH (United States)

1995-08-01

204

Liquid-phase and solid-phase microwave irradiations for reduction of graphite oxide  

NASA Astrophysics Data System (ADS)

In this paper, two microwave irradiation methods: (i) liquid-phase microwave irradiation (MWI) reduction of graphite oxide suspension dissolved in de-ionized water and N, N-dimethylformamide, respectively, and (ii) solid-phase MWI reduction of graphite oxide powder have been successfully carried out to reduce graphite oxide. The reduced graphene oxide products are thoroughly characterized by scanning electron microscopy, atomic force microscopy, X-ray photoelectron spectroscopy, Fourier transform infrared spectral analysis, Raman spectroscopy, UV-Vis absorption spectral analysis, and four-point probe conductivity measurements. The results show that both methods can efficiently remove the oxygen-containing functional groups attached to the graphite layers, though the solid-phase MWI reduction method can obtain far more efficiently a higher quality-reduced graphene oxide with fewer defects. The I(D)/I(G) ratio of the solid-phase MWI sample is as low as 0.46, which is only half of that of the liquid-phase MWI samples. The electrical conductivity of the reduced graphene oxide by the solid method reaches 747.9 S/m, which is about 25 times higher than that made by the liquid-phase method.

Zhao, Na; Wen, Chen-Yu; Zhang, David Wei; Wu, Dong-Ping; Zhang, Zhi-Bin; Zhang, Shi-Li

2014-12-01

205

Effect of gravity on three-dimensional coordination number distribution in liquid phase sintered microstructures  

SciTech Connect

Gravity affects microstructural evolution when a liquid phase is present during sintering. The effect of gravity on the three-dimensional coordination number distribution of tungsten grains in liquid phase sintered heavy alloy specimens is quantitatively characterized. A combination of montage serial sectioning, digital image processing, and unbiased stereological sampling procedures is used to estimate the coordination number distribution in three-dimensional microstructures. The microgravity environment decreases the mean coordination number. However, hardly any isolated grains are observed in the specimens, liquid phase sintered in a microgravity environment. The effect of microgravity on the coordination numbers mainly resides in its effect on the mean coordination number. In all specimens, there is a strong correlation between grain size and coordination number, which can be expressed as [D{sub c}/{bar D}]{sup 2} = C/C{sub 0} where C{sub 0} is the mean coordination number, {bar D} the global average size of the tungsten grains, and D{sub c} the average size of only those grains which have coordination number C.

Tewari, A.; Gokhale, A.M.; Gereman, R.M.

1999-10-08

206

Probing the stability of the spin-liquid phases in the Kitaev-Heisenberg model using tensor network algorithms  

NASA Astrophysics Data System (ADS)

We study the extent of the spin liquid phases in the Kitaev-Heisenberg model using infinite projected entangled-pair states tensor network ansatz wave functions directly in the thermodynamic limit. To assess the accuracy of the ansatz wave functions, we perform benchmarks against exact results for the Kitaev model and find very good agreement for various observables. In the case of the Kitaev-Heisenberg model, we confirm the existence of six different phases: Néel, stripy, ferromagnetic, zigzag, and two spin liquid phases. We find finite extents for both spin liquid phases and discontinuous phase transitions connecting them to symmetry-broken phases.

Osorio Iregui, Juan; Corboz, Philippe; Troyer, Matthias

2014-11-01

207

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

NASA Astrophysics Data System (ADS)

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

Rahman, A. H. M. Esfakur

208

Preparation N-F-codoped TiO{sub 2} nanorod array by liquid phase deposition as visible light photocatalyst  

SciTech Connect

Research highlights: {yields} The formation of N, F-codoped TiO{sub 2} nanorod arrays via the LPD. {yields} Calcination temperature greatly effects the incorporation of N and F into TiO{sub 2}. {yields} TNRAs calcined at 450 {sup o}C showed highest visible light photocatalytic activity. {yields} A synergetic effect of 1D nanorod arrays and appropriate amount of N and F codoping. -- Abstract: An efficient method for the preparation of N-F-codoped visible light active TiO{sub 2} nanorod arrays is reported. In the process, simultaneous nitrogen and fluorine doped TiO{sub 2} nanorod arrays on the glass substrates were achieved by liquid phase deposition method using ZnO nanorod arrays as templates with different calcination temperature. The as-prepared samples were characterized by Raman spectroscopy, scanning electron microscopy (SEM), transmission electron microscopy (TEM), X-ray photoelectron spectroscopy (XPS) and UV-vis absorption spectra measurements. It was found that calcination temperature is an important factor influencing the microstructure and the amount of N and F in TiO{sub 2} nanorod arrays samples. The visible light photocatalytic properties were investigated using methylene blue (MB) dye as a model system. The results showed that N-F-codoped TiO{sub 2} nanorod arrays sample calcined at 450 {sup o}C demonstrated the best visible light activity in all samples, much higher than that of TiO{sub 2} nanoparticles and P25 particles films.

Lv, Yan; Fu, Zhengping [CAS Key Laboratory of Materials for Energy Conversion, Department of Materials Science, and Engineering, University of Science and Technology of China, Hefei, Anhui 230026 (China)] [CAS Key Laboratory of Materials for Energy Conversion, Department of Materials Science, and Engineering, University of Science and Technology of China, Hefei, Anhui 230026 (China); Yang, Beifang, E-mail: bfyang@ustc.edu.cn [CAS Key Laboratory of Materials for Energy Conversion, Department of Materials Science, and Engineering, University of Science and Technology of China, Hefei, Anhui 230026 (China)] [CAS Key Laboratory of Materials for Energy Conversion, Department of Materials Science, and Engineering, University of Science and Technology of China, Hefei, Anhui 230026 (China); Xu, Jiao; Wu, Min; Zhu, Changqiong; Zhao, Yongxun [CAS Key Laboratory of Materials for Energy Conversion, Department of Materials Science, and Engineering, University of Science and Technology of China, Hefei, Anhui 230026 (China)] [CAS Key Laboratory of Materials for Energy Conversion, Department of Materials Science, and Engineering, University of Science and Technology of China, Hefei, Anhui 230026 (China)

2011-03-15

209

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

PubMed

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

Hatami, Mehdi; Farhadi, Khalil

2012-07-01

210

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

SciTech Connect

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

Michael F. Gray; Peter Zalupski; Mikael Nilsson

2013-08-01

211

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

SciTech Connect

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

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

2011-09-15

212

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

NASA Astrophysics Data System (ADS)

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

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

2013-12-01

213

Texture development in liquid phase sintered alpha alumina via anisotropic template growth  

NASA Astrophysics Data System (ADS)

The anisotropic grain growth of liquid phase sintered alpha alumina was investigated. Samples of controlled anisotropic fraction (˜9 mum major axis, aspect ratio = 10) were prepared by adding anisotropic template particles to matrix material of fine particle size (initial median size = 0.2 mum) with CaO and SiO2 additives. The resulting slurry was tape cast, laminated and sintered to produce highly textured materials. This process is called templated grain growth, or TGG. The sample texture was measured by x-ray diffraction rocking curve measurements, and the orientation distribution function was fit using the March-Dollase function. The fitting parameters were used to calculate the stereological correction factors for template size, which was measured by image analysis of SEM micrographs. Together, these techniques yielded accurate measurements of the growth of the anisotropic template particles during sintering. Texture development in TGG materials was found to be directly controlled by the growth of the template particles, which in turn was strongly affected by liquid phase content and initial template concentration. Single crystal samples were embedded in alumina matrices of the same composition as the TGG samples. Growth of several crystal directions was measured under a variety of sintering conditions. Growth was found to be strongly affected by liquid phase content. Growth of the single crystals in non-basal directions was modeled using a diffusion controlled model of growth, while the basal growth of the single crystals was found to agree well with a two-dimensional nucleation and growth model. Using the expressions obtained for single crystal growth, the anisotropic grain growth of the template particles in the TGG samples was modeled. Template size and concentration played significant roles in the growth of template particles. These effects can be accommodated for within the single crystal growth theories to provide a measure of the effect of template-template impingement on growth.

Seabaugh, Matthew Mark

214

Thermodynamic Relationships for Bulk Crystalline and Liquid Phases in the Phase-Field Crystal Model  

E-print Network

We present thermodynamic relationships between the free energy of the phase-field crystal (PFC) model and thermodynamic state variables for bulk phases under hydrostatic pressure. This relationship is derived based on the thermodynamic formalism for crystalline solids of Larch\\'e and Cahn [Larch\\'e and Cahn, Acta Metallurgica, Vol. 21, 1051 (1973)]. We apply the relationship to examine the thermodynamic processes associated with varying the input parameters of the PFC model: temperature, lattice spacing, and the average value of the PFC order parameter, $\\bar{n}$. The equilibrium conditions between bulk crystalline solid and liquid phases are imposed on the thermodynamic relationships for the PFC model to obtain a procedure for determining solid-liquid phase coexistence. The resulting procedure is found to be in agreement with the method commonly used in the PFC community, justifying the use of the common-tangent construction to determine solid-liquid phase coexistence in the PFC model. Finally, we apply the procedure to an eighth-order-fit (EOF) PFC model that has been parameterized to body-centered-cubic ($bcc$) Fe [Jaatinen et al., Physical Review E 80, 031602 (2009)] to demonstrate the procedure as well as to develop physical intuition about the PFC input parameters. We demonstrate that the EOF-PFC model parameterization does not predict stable $bcc$ structures with positive vacancy densities. This result suggests an alternative parameterization of the PFC model, which requires the primary peak position of the two-body direct correlation function to shift as a function of $\\bar{n}$.

Victor W. L. Chan; Nirand Pisutha-Arnond; Katsuyo Thornton

2015-02-06

215

Optimization of high-molecular-weight polycyclic aromatic hydrocarbons' degradation in a two-liquid-phase bioreactor.  

PubMed

A microbial consortium degrading the high-molecular-weight polycyclic aromatic hydrocarbons (HMW PAHs) pyrene, chrysene, benzo[a]pyrene and perylene in a two-liquid-phase reactor was studied. The highest PAH-degrading activity was observed with silicone oil as the water-immiscible phase; 2,2,4,4,6,8, 8-heptamethylnonane, paraffin oil, hexadecane and corn oil were much less, or not efficient in improving PAH degradation by the consortium. Addition of surfactants (Triton X-100, Witconol SN70, Brij 35 and rhamnolipids) or Inipol EAP22 did not promote PAH biodegradation. Rhamnolipids had an inhibitory effect. Addition of salicylate, benzoate, 1-hydroxy-2-naphtoic acid or catechol did not increase the PAH-degrading activity of the consortium, but the addition of low-molecular-weight (LMW) PAHs such as naphthalene and phenanthrene did. In these conditions, the degradation rates were 27 mg l-1 d-1 for pyrene, 8.9 mg l-1 d-1 for chrysene, 1.8 mg l-1 d-1 for benzo[a]pyrene and 0.37 mg l-1 d-1 for perylene. Micro-organisms from the interface were slightly more effective in degrading PAHs than those from the aqueous phase. PMID:10792524

Marcoux, J; Déziel, E; Villemur, R; Lépine, F; Bisaillon, J G; Beaudet, R

2000-04-01

216

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

2013-11-01

217

Organic salt-assisted liquid-phase exfoliation of graphite to produce high-quality graphene  

NASA Astrophysics Data System (ADS)

Certain ordinary organic salts, such as edetate disodium, sodium tartrate, potassium sodium tartrate and sodium citrate were found to have universal and efficient assistant effect for liquid-phase exfoliation of graphite in common organic solvents to produce pristine graphene. Up to 123 times enhanced exfoliation efficiency was observed when sodium citrate was introduced into an exfoliation system consisting of natural graphite powder and dimethyl sulfoxide. TEM, AFM, Raman spectroscopy, EDX, TGA, and FTIR analysis showed graphite was successfully exfoliated into single or few-layer graphene nanosheets which were free of defects and oxides. The method is simple, effective, safe and economical.

Du, Wencheng; Lu, Jie; Sun, Peipei; Zhu, Yinyan; Jiang, Xiaoqing

2013-05-01

218

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

219

Computation of heat transfer with solid/liquid phase change including free convection  

NASA Astrophysics Data System (ADS)

A computational model is presented for the prediction of solid/liquid phase change energy transport including the influence of free convection. The computational model considers the velocity components of all nonliquid PCM control volumes to be zero but fully solves the coupled mass-momentum problem within the liquid. The thermal energy model includes the entire domain and employs an enthalpy-like model in addition to recent developments for handling the phase change interface nonlinearity. The predictions are compared with experimental data and with previous predictions for the test problem examined. The present procedure demonstrates both excellent agreement with the experimental data and a significant computational cost reduction from previous procedures.

Schneider, G. E.

1985-01-01

220

Kinetic study of liquid-phase hydrogenation of citral over Ir\\/TiO 2 catalysts  

Microsoft Academic Search

The kinetics of liquid-phase hydrogenation of citral (3,7-dimethyl-2,6-octadienal) on Ir\\/TiO2 catalysts were studied in the temperature range of 303–363K and a pressure range of 4.13–10.3bar H2. Geraniol and nerol were the only reaction products, generated through the hydrogenation of the carbonyl group of citral. Negative near second-order dependence on citral concentration and near first-order dependence on hydrogen pressure were observed

P Reyes; H Rojas; J. L. G Fierro

2003-01-01

221

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

222

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

223

Microstructural study of transient liquid phase bonded cast INCONEL 738LC superalloy  

Microsoft Academic Search

The microstructure of the transient liquid phase (TLP) bonded joint of a cast INCONEL 738LC superalloy, made with a commercial\\u000a Ni-Cr-B filler alloy, Nicrobraz 150, was examined by analytical scanning and transmission electron microscopic techniques.\\u000a Due to incomplete isothermal solidification at the bonding temperature, the residual liquid interlayer transformed to nonequilibrium\\u000a eutectic microconstituents consisting of chromium-rich M5B3, nickel-rich M23B6, and

O. A. Idowu; O. A. Ojo; M. C. Chaturvedi

2006-01-01

224

Low temperature liquid-phase sintering in the magnesium aluminosilicate glass - alumina system  

NASA Astrophysics Data System (ADS)

This study was carried out to obtain a fundamental understanding of the process conditions and strategies for lowering liquid phase sintering temperatures. Alumina coated with 9 vol% of a ternary eutectic glass in the MgO-Alsb2Osb3-SiOsb2 (MAS) was used as the model system. Homogeneous coating of the glass was ensured by using a sol-gel coating technique. Sintering behavior of the glass coated alumina was investigated over a temperature range of 1400sp°C-1460sp°C. Mullite and spinel or sapphirine crystallized from the MAS liquid during sintering. The formation of spinel was observed at the interface between the liquid and alumina, whereas mullite was found to homogeneously crystallize in the liquid. The rate of glass crystallization was enhanced by finer powder. The time at which crystallization rate became significant corresponded to the onset of the decrease of densification rate at the temperature. Attaining a balance of these two competing phenomena at the sintering temperature is proposed as an additional criteria for successful liquid phase sintering at low temperatures. Additional experiments revealed that this balance is not easy to control in the case of bimodal powder mixture, and that homogeneous distribution of liquid at the initial stage is essential for the control of this balance. Densification kinetics and crystallization behavior of 0.2 mum alumina coated with boron or sodium doped glass in the MAS system were also investigated at 1400sp°C and 1460sp°C. Doping the Alsb2Osb3-MAS glass system is effective for liquid phase sintering of alumina at 1400sp°C. The balance between densification and crystallization for the alumina coated with MAS glass was altered by the addition of boron and sodium. However, the mechanisms by which boron and sodium improve the sintering kinetics are different. From the experimentally obtained result, the ratio of the densification rate to crystallization rate was calculated. Using theoretically determined equations and the analysis of above mentioned ratio, strategies to lower the temperature of liquid phase sintering was proposed.

Nakajima, Akira

225

Cu-Sn transient liquid phase wafer bonding for MEMS applications  

NASA Astrophysics Data System (ADS)

The impact of process parameters on final bonding layer quality was investigated for Transient Liquid Phase (TLP) wafer-level bonding based on the Cu-Sn system. Subjects of this investigation were bonding temperature profile, bonding time and contact pressure as well as the choice of metal deposition method and the ratio of deposited metal layer thicknesses. Typical failure modes in Inter-Metallic Compound (IMC) growth for the mentioned process and design parameters were identified and subjected to qualitative and quantitative analysis. The possibilities to avoid abovementioned failures are indicated based on experimental results.

Flötgen, C.; Pawlak, M.; Pabo, E.; van de Wiel, H. J.; Hayes, G. R.; Dragoi, V.

2013-05-01

226

Absence of the liquid phase when the attraction is not pairwise additive  

E-print Network

Recent work on charged colloidal suspensions with very low levels of added salt has suggested that although pairs of the colloidal particles repel, clusters of the particles attract. Motivated by this, we study simple model particles which have many-body attractions. These attractions are generic many-body attractions and are not calculated for any specific colloidal suspension. We find that many-body attractions can stabilise solid phases at low pressures but that the liquid phase is either completely absent from the equilibrium phase diagram or present only within a small region of parameter space

Richard P. Sear

1999-09-06

227

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

228

Liquid phase microextraction using knitting wool as the extractant phase holder before chromatographic analysis: a new approach for trace analysis.  

PubMed

In this paper, a novel liquid phase microextraction (LPME) approach was developed in which a piece of knitting wool was used as the extractant solvent holder. Owing to the absorbability of the wool, the extractant could be easily held within the material. When the wool containing the organic solvent was exposed to the sample solution, analytes could directly diffuse from the sample solution to the solvent. Ultraviolet (UV) filters ([2,4-dihydroxybenzophenone (BP-1), benzophenone (BP) and 2-hydroxy-4-methoxybenzophenone (BP-3)]) were used as model analytes to evaluate the procedure. Parameters that affect the extraction efficiency (selection of organic solvent, volume of the extractant, agitation speed, extraction time, salt concentration and pH) were investigated. The proposed method in combination with liquid chromatography-UV detection, provided good enrichment factors up to 366, with relative standard deviations of between 0.6% and 4.2% on the same piece of wool, and good linearity from 0.1 ng/ml to 100 ng/ml for all the analytes with regression coefficients of between 0.9998 and 0.9999. The limits of quantification of these compounds, calculated at S/N=10, were 0.1 ng/ml, 0.07 ng/ml and 0.1 ng/ml for BP-1, BP, BP-3, respectively. The method was applied to the determination of BP-type UV filters in swimming pool water. This is the first report of an application of knitting wool as a solvent holder for LPME. The procedure is cost-effective, and easy to operate. PMID:23276647

Zhang, Yufeng; Lee, Hian Kee

2013-01-18

229

Electric and Elastic Coefficients of Lead Magnesium Niobate-Based Ceramics Under DC Bias for Active Smart Sensor Applications  

NASA Astrophysics Data System (ADS)

In this thesis, certain ceramics containing lead magnesium niobate rm (Pb(Mg_{1/3 }Nb_{2/3})O_3 or PMN) and lead titanate (PbTiO_3 or PT) were characterized as materials most suitable for active smart sensor applications. The selection of these active materials for use in smart systems which have "sensing," "actuating," and "intelligence" capabilities controlled by a DC bias field was based on earlier studies in which it was demonstrated that certain compositions of these materials under a weak DC bias field show a very strong induced piezoelectric effect. That is, these materials exhibit nonlinear strain-electric field characteristics in which an electric bias field can act as the controlling mechanism for the piezoelectric property of the material, which determines the sensing and indirectly determines the actuating capabilities of the material. Furthermore, with the goal of characterizing these PMN-based ceramics for active smart sensor applications, this thesis remarks on some of the effects that an externally applied DC bias field can have on a relaxor-type ferroelectric material like PMN. For the four compositions, (1 - x)PMN - (x)PT (x = 0.07 and x = 0.10), and (1 - x)PMN - (x)PT (x = 0.00 and x = 0.07) with 1 mole percent lanthanum the electric and elastic properties of the material were studied as a function of the DC bias over a range of conditions. For higher frequency applications, the complex material parameters (piezoelectric coefficient, elastic, and the dielectric constant) were measured as a function of bias at several temperatures using a modified resonance method. For lower frequency applications, the piezoelectric hydrostatic coefficient (d_{h}), and its DC field dependence, were evaluated from the relationship d_{h}=d_ {33}+2d_{31}, and measurements of d_{33} and d _{31} were made with an optical ultradilatometer. Finally, for a further understanding of the piezoelectric effect, the temperature dependence of the pyroelectric and dielectric response as a function of a selected DC bias field were investigated using the Byer-Roundy method and an LCR meter. In conclusion, this thesis provides the first truly comprehensive experimental study of PMN-based ceramics for device applications. In so doing it lays the groundwork for the development of active smart sensor applications.

Taylor, Deborah Jane

230

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

231

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

232

Transient-pressure analysis in geothermal steam reservoirs with an immobile vaporizing liquid phase  

USGS Publications Warehouse

A finite-difference model for the radial horizontal flow of steam through a porous medium is used to evaluate transient-pressure behavior in the presence of an immobile vaporizing or condensing liquid phase. Graphs of pressure drawdown and buildup in terms of dimensionless pressure and time are obtained for a well discharging steam at a constant mass flow rate for a specified time. The assumptions are made that the steam is in local thermal equilibrium with the reservoir rocks, that temperature changes are due only to phase change, and that effects of vapor-pressure lowering are negligible. Computations show that when a vaporizing liquid phase is present the pressure drawdown exhibits behavior similar to that observed in noncondensable gas reservoirs, but delayed in time. A theoretical analysis allows for the computation of this delay and demonstrates that it is independent of flow geometry. The response that occurs upon pressure buildup is markedly different from that in a noncondensable gas system. This result may provide a diagnostic tool for establishing the existence of phase-change phenomena within a reservoir. ?? 1979.

Moench, A.F.; Atkinson, P.G.

1978-01-01

233

Applications of liquid-phase microextraction in the sample preparation of environmental solid samples.  

PubMed

Solvent extraction remains one of the fundamental sample preparation techniques in the analysis of environmental solid samples, but organic solvents are toxic and environmentally harmful, therefore one of the possible greening directions is its miniaturization. The present review covers the relevant research from the field of application of microextraction to the sample preparation of environmental solid samples (soil, sediments, sewage sludge, dust etc.) published in the last decade. Several innovative liquid-phase microextraction (LPME) techniques that have emerged recently have also been applied as an aid in sample preparation of these samples: single-drop microextraction (SDME), hollow fiber-liquid phase microextraction (HF-LPME), dispersive liquid-liquid microextraction (DLLME). Besides the common organic solvents, surfactants and ionic liquids are also used. However, these techniques have to be combined with another technique to release the analytes from the solid sample into an aqueous solution. In the present review, the published methods were categorized into three groups: LPME in combination with a conventional solvent extraction; LPME in combination with an environmentally friendly extraction; LPME without previous extraction. The applicability of these approaches to the sample preparation for the determination of pollutants in solid environmental samples is discussed, with emphasis on their strengths, weak points and environmental impact. PMID:24858267

Prosen, Helena

2014-01-01

234

Probability analysis of contact forces in quasi-solid-liquid phase transition of granular shear flow  

NASA Astrophysics Data System (ADS)

The quasi-solid-liquid phase transition exists widely in different fields, and attracts more attention due to its instinctive mechanism. The structure of force chains is an important factor to describe the phase transition properties. In this study, the discrete element model (DEM) is adopted to simulate a simple granular shear flow with period boundary condition on micro scale. The quasi-solid-liquid phase transition is obtained under various volume fractions and shear rates. Based on the DEM results, the probability distribution functions of the inter-particle contact force are obtained in different shear flow phases. The normal, tangential and total contact forces have the same distributions. The distribution can be fitted as the exponential function for the liquid-like phase, and as the Weibull function for the solid-like phase. To describe the progressive evolution of the force distribution in phase transition, we use the Weibull function and Corwin-Ngan function, respectively. Both of them can determine the probability distributions in different phases and the Weibull function shows more reasonable results. Finally, the force distributions are discussed to explain the characteristics of the force chain in the phase transition of granular shear flow. The distribution of the contact force is an indicator to determine the flow phase of granular materials. With the discussions on the statistical properties of the force chain, the phase transition of granular matter can be well understood.

Ji, ShunYing

2013-02-01

235

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

236

Liquid-Liquid Phase Separation of a Monoclonal Antibody and Nonmonotonic Influence of Hofmeister Anions  

PubMed Central

Liquid-liquid phase separation was studied for a monoclonal antibody in the monovalent salt solutions of KF, KCl, and KSCN under different pH conditions. A modified Carnahan-Starling hard-sphere model was utilized to fit the experimental data, establish the liquid-liquid coexistence curve, and determine antibody-antibody interactions in the form of Tc (critical temperature) under the different solution conditions. The liquid-liquid phase separation revealed the complex relationships between antibody-antibody interactions and different solution conditions, such as pH, ionic strength, and the type of anion. At pH 7.1, close to the pI of the antibody, a decrease of Tc versus ionic strength was observed at low salt conditions, suggesting that the protein-protein interactions became less attractive. At a pH value below the pI of the antibody, a nonmonotonic relationship of Tc versus ionic strength was apparent: initially as the ionic strength increased, protein-protein interactions became more attractive with the effectiveness of the anions following the inverse Hofmeister series; then the interactions became less attractive following the direct Hofmeister series. This nonmonotonic relationship may be explained by combining the charge neutralization by the anions, perhaps with the ion-correlation force for polarizable anions, and their preferential interactions with the antibody. PMID:21112304

Mason, Bruce D.; Zhang-van Enk, Jian; Zhang, Le; Remmele, Richard L.; Zhang, Jifeng

2010-01-01

237

Liquid Phase Sintered Ceramic Bone Scaffolds by Combined Laser and Furnace  

PubMed Central

Fabrication of mechanically competent bioactive scaffolds is a great challenge in bone tissue engineering. In this paper, ?-tricalcium phosphate (?-TCP) scaffolds were successfully fabricated by selective laser sintering combined with furnace sintering. Bioglass 45S5 was introduced in the process as liquid phase in order to improve the mechanical and biological properties. The results showed that sintering of ?-TCP with the bioglass revealed some features of liquid phase sintering. The optimum amount of 45S5 was 5 wt %. At this point, the scaffolds were densified without defects. The fracture toughness, compressive strength and stiffness were 1.67 MPam1/2, 21.32 MPa and 264.32 MPa, respectively. Bone like apatite layer was formed and the stimulation for apatite formation was increased with increase in 45S5 content after soaking in simulated body fluid, which indicated that 45S5 could improve the bioactivity. Furthermore, MG-63 cells adhered and spread well, and proliferated with increase in the culture time. PMID:25196598

Feng, Pei; Deng, Youwen; Duan, Songlin; Gao, Chengde; Shuai, Cijun; Peng, Shuping

2014-01-01

238

Liquid-Liquid Phase Separation in Supersaturated Lysozyme Solutions and Associated Precipitate Formation/Crystallization  

NASA Technical Reports Server (NTRS)

Using cloud point determinations, the phase boundaries (binodals) for metastable liquid-liquid (L-L) separation in supersaturated hen egg white lysozyme solutions with 3%, 5%, and 7% (wlv) NaCl at pH= 4.5 and protein concentrations c between 40 and 400 mg/ml were determined. The critical temperature for the binodal increased approximately linearly with salt concentration. The coexisting liquid phases both remained supersaturated but differed widely in protein concentration. No salt repartitioning was observed between the initial and the two separated liquid phases. After the L-L separation, due to the presence of the high protein concentration phase, crystallization occurred much more rapidly than in the initial solution. At high initial protein concentrations, a metastable gel phase formed at temperatures above the liquid binodal. Both crystal nucleation and gel formation were accelerated in samples that had been cycled through the binodal. Solutions in the gel and L-L regions yielded various types of precipitates. Based on theoretical considerations, previous observations with other proteins, and our experimental results with lysozyme, a generic phase diagram for globular proteins is put forth. A limited region in the (T,c) plane favorable for the growth of protein single crystals is delineated.

Muschol, Martin; Rosenberger, Franz

1997-01-01

239

Liquid-liquid phase transition for an attractive isotropic potential with wide repulsive range.  

PubMed

We investigate how the phase diagram of a repulsive soft-core attractive potential, with a liquid-liquid phase transition in addition to the standard gas-liquid phase transition, changes by varying the parameters of the potential. We extend our previous work on short soft-core ranges to the case of large soft-core ranges, by using an integral equation approach in the hypernetted-chain approximation. We show, using a modified van der Waals equation we recently introduced, that if there is a balance between the attractive and repulsive part of the potential this potential has two fluid-fluid critical points well separated in temperature and in density. This implies that for the repulsive (attractive) energy U(R)(U(A)) and the repulsive (attractive) range w(R)(w(A)) the relation U(R)/U(A) proportional to w(R)/w(A) holds for short soft-core ranges, while U(R)/U(A) proportional to 3w(R)/w(A) holds for large soft-core ranges. PMID:16089740

Malescio, Gianpietro; Franzese, Giancarlo; Skibinsky, Anna; Buldyrev, Sergey V; Stanley, H Eugene

2005-06-01

240

Investigation of the growth of garnet films by liquid phase epitaxy  

NASA Technical Reports Server (NTRS)

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 deposited on Gd3Ga5012 substrates. The uniaxial anisotropy of the Gd-Y garnets is primarily stress-induced. These garnets are characterized by high-domain wall mobility, low coercivity and modest anisotropy. Characteristic length was found to be relatively sensitive to temperature. The Eu-Yb-Y garnets exhibit acceptable mobilities, good temperature stability and reasonable quality factors. The uniaxial anisotropy of these garnets is primarily growth-induced. The system is well suited for compositional "tailoring" to optimize specific desirable properties. Liquid phase epitaxy can be used to deposit Gd3Ga5012 spacing layers on magnetic garnet films and this arrangement possesses certain advantages over more conventional magnetic filmspacing layer combinations. However, it cannot be used if the magnetic film is to be ion implanted.

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

1974-01-01

241

Solvatochromic characterization of the liquid phase in liquid-supercritical CO{sub 2} mixtures  

SciTech Connect

The solvatochromic dye phenol blue (N,N-dimethylindoaniline) is used to characterize the solvent strength (polarity) of the saturated liquid phase in a series of solvent-carbon dioxide binary mixtures. Data were obtained at 35 and 55 C and at pressures up to {approximately}70 bar. Five solvents were investigated--acetone, cyclohexane, methanol, THF, and toluene. The polarity of the liquid phase decreases significantly with increasing pressure due to the increasing carbon dioxide content of this phase at equilibrium. For example, the polarity of acetone saturated with carbon dioxide at 35 C and {approximately}60 bar is equivalent to the polarity of pure cyclohexane at ambient pressure. The local environment about the dye is significantly richer in the polar liquid component than the bulk composition would indicate. The degree of enrichment reflects concentration effects at low pressure, and both concentration and pressure effects at high pressure where the mixtures are highly compressible. The NRTL model of Renon and Prausnitz is able to predict these local compositions with reasonable accuracy except at CO{sub 2}-rich conditions where compressibility effects are important.

Kelley, S.P.; Lemert, R.M. [Univ. of Toledo, OH (United States). Chemical Engineering Dept.] [Univ. of Toledo, OH (United States). Chemical Engineering Dept.

1996-07-01

242

Electro-thermal treatment of high concentration ammonia in water by gaseous oxidation in liquid phase (GOLP).  

PubMed

Gaseous oxidation in liquid phase (GOLP) process was proposed to degrade high concentration ammonium in water. The innovative concept behind the reactor design is that the monocrystalline silicon chip coated with catalyst could be heated instantaneously by direct current, which will gasify the surrounding ammonium solution and later catalytically convert it to harmless N(2). It is found out that Co(3)O(4) instead of Co(2)O(3) is the active catalytic component in the GOLP process and it coats the silicon chip evenly with nut-shell particle. The experimental results reveal that the GOLP process could degrade high concentration NH(4)(+) efficiently, in which when the current was 10A, the reactor could remove almost 98% NH(4)(+) after 2h treatment, at the initial concentration 1810mgL(-1). The overall GOLP process for de-nitrification could be presumed to have two steps: (1) the gasification of liquid around catalyst; and (2) catalytic conversion of NH(4)(+) to N(2), which is experimentally demonstrated by Ion Chromatography data. Also, the influences of current and pH were investigated to optimize the operating parameters for the GOLP reactor, and the preliminary energy consumption analysis based on lab data was provided for future reference. These results show that the GOLP process will be able to sustain without extra energy input theoretically if the ammonia concentration is higher than 1.48%. PMID:20462628

Cao, Limei; Yang, Ji; Jia, Jinping

2010-06-01

243

Liquid-phase methanation/shift process development. First quarterly progress report, September 1-November 30, 1980  

SciTech Connect

This program is a continuation of the Liquid Phase Methanation/Shift Program (EX-76-C-01-2036) which was completed on November 30, 1978. One of its primary goals is to study the rates of carbon formation during methanation over a wide range of process conditions and determine the effect of the carbon deposition on catalyst activity and selectivity. The second goal is to perform an engineering design of a hydrodynamic cold-flow unit of scale equivalent to the LPM/S pilot plant reactor for evaluation of the 3-phase reaction system hydrodynamics. Work to date has concentrated on the first task - Rates of Carbon Formation. The existing reaction units and analytical system have been refurbished and calibrated. Five nickel-based methanation catalysts were chosen as representative of the types available commercially. Carrier materials for the catalysts are alumina, kieselguhr and calcium aluminate. Nickel contents vary from 35 to 60% Ni. The first experimental scan, 100 hours - without steam, has been successfully completed. The second scan is in progress, 300 hours - without steam. Samples of both spent and virgin reduced catalysts have been sent out for analysis.

Not Available

1981-01-20

244

The use of multidimensional liquid-phase separations and mass spectrometry for the detailed characterization of posttranslational modifications in glycoproteins.  

PubMed

The goal of characterization of the proteome, while challenging in itself, is further complicated by the microheterogeneity introduced by posttranslational modifications such as glycosylation. A combination of liquid chromatography (LC), capillary electrophoresis (CE), and mass spectrometry (MS) offers the advantages of unique selectivity and high efficiency of the separation methods combined with the mass specificity and sensitivity of MS. In the current work, the combination of liquid-phase separations and mass spectrometry is demonstrated through the on-line coupling of electrospray ionization mass spectrometry (ESI-MS) and off-line coupling with matrix-assisted laser desorption/ionization time-of-flight mass spectrometry (MALDI TOF-MS). LC/ESI-MS yields real-time results while maintaining the separation obtained from the LC analysis. CE/MALDI TOF-MS offers high-mass detection and extremely low detection limits. The unique separation selectivity of CE relative to reversed-phase HPLC separations of the members of a glycopeptide family was used to develop an integrated multidimensional analysis achieved by the off-line coupling of LC, CE, and MALDI TOF-MS. To demonstrate the applicability of these techniques to the characterization of the heterogeneity of posttranslational modifications present in glycoproteins, we will report on the study of the glycoforms present in a N-linked site in a single-chain plasminogen activator (DSPA?1). PMID:21644704

Udiavar, S; Apffel, A; Chakel, J; Swedberg, S; Hancock, W S; Pungor, E

1998-09-01

245

Tracking plasma generated H2O2 from gas into liquid phase and revealing its dominant impact on human skin cells  

NASA Astrophysics Data System (ADS)

The pathway of the biologically active molecule hydrogen peroxide (H2O2) from the plasma generation in the gas phase by an atmospheric pressure argon plasma jet, to its transition into the liquid phase and finally to its inhibiting effect on human skin cells is investigated for different feed gas humidity settings. Gas phase diagnostics like Fourier transformed infrared spectroscopy and laser induced fluorescence spectroscopy on hydroxyl radicals (·OH) are combined with liquid analytics such as chemical assays and electron paramagnetic resonance spectroscopy. Furthermore, the viability of human skin cells is measured by Alamar Blue® assay. By comparing the gas phase results with chemical simulations in the far field, H2O2 generation and destruction processes are clearly identified. The net production rate of H2O2 in the gas phase is almost identical to the H2O2 net production rate in the liquid phase. Moreover, by mimicking the H2O2 generation of the plasma jet with the help of an H2O2 bubbler it is concluded that the solubility of gas phase H2O2 plays a major role in generating hydrogen peroxide in the liquid. Furthermore, it is shown that H2O2 concentration correlates remarkably well with the cell viability. Other species in the liquid like ·OH or superoxide anion radical (O_{2}^{\\cdot -} ) do not vary significantly with feed gas humidity.

Winter, J.; Tresp, H.; Hammer, M. U.; Iseni, S.; Kupsch, S.; Schmidt-Bleker, A.; Wende, K.; Dünnbier, M.; Masur, K.; Weltmann, K.-D.; Reuter, S.

2014-07-01

246

Mid-infrared photoconductive properties of heavily Bi-doped PbTe p-n homojunction diode grown by liquid-phase epitaxy  

NASA Astrophysics Data System (ADS)

We fabricated a heavily Bi-doped (xBi ? 2 × 1019 cm-3) PbTe p-n homojunction diode that detects mid-infrared wavelengths by the temperature difference method (TDM) under controlled vapor pressure (CVP) liquid phase epitaxy (LPE). The photocurrent density produced by the heavily Bi-doped diode sample is approximately 20 times and 3 times greater than that produced by an undoped and heavily In-doped sample, respectively. By varying the ambient temperature from 15 K to 225 K, the detectable wavelength is tunable from 6.18 ?m to 4.20 ?m. The peak shift of the detectable wavelength is shorter in the heavily Bi-doped sample than in the undoped sample, consistent with our previously proposed model, in which Bi-Bi nearest donor-acceptor pairs are formed in the heavily Bi-doped PbTe liquid phase epitaxial layer. Current-voltage (I-V) measurements of the heavily Bi-doped diode sample under infrared exposure at 77 K indicated a likely leak in the dark current, arising from the deeper levels. From the dark I-V measurements, the activation energy of the deep level was estimated as 0.067 eV, close to the energy of the deep Tl-doped PbTe acceptor layer. We conclude that the deep level originates from the Tl-doped p-type epitaxial layer.

Yasuda, Arata; Suto, Ken; Takahashi, Yatsuhiro; Nishizawa, Jun-ichi

2014-11-01

247

Pumice-supported Pd-Pt bimetallic catalysts: Synthesis, structural characterization, and liquid-phase hydrogenation of 1,3-cyclooctadiene  

SciTech Connect

A series of pumice-supported palladium-platinum bimetallic catalysts were prepared and investigated by X-ray scattering (WAXS and SAXS) and XPS techniques. An alloy Pd-Pt was formed. The less abundant metal was found to segregate to the surface. The catalysts were tested in the liquid-phase hydrogenation of 1,3-cyclooctadiene to cyclooctene, and compared with similarly prepared pumice-supported palladium and platinum catalysts and other supported Pd-Pt catalysts reported in the literature. The addition of platinum reduces the activity and the selectivity of the palladium catalysts. Differences between the activity of these pumice-supported catalysts and the activity of previously described Pd and Pd-Pt catalysts on other supports, are attributed to the presence, in the latter, of diffusional processes. 50 refs., 4 figs. 2 tabs.

Deganello, G.; Duca, D.; Liotta, L.F.; Martorana, A.; Venezia, M. [Istituto di Chimica e Technologia dei Prodotti Naturali del CNR, Palermo (Italy)] [Istituto di Chimica e Technologia dei Prodotti Naturali del CNR, Palermo (Italy); Benedetti, A.; Fagherazz, G. [Universita di Venezia, Venice (Italy)] [Universita di Venezia, Venice (Italy)

1995-01-01

248

Mass Transfer Correlation Coefficients for Two-Phase Systems: A General Review for Liquid-Liquid  

Microsoft Academic Search

A general review of the mass transfer correlation coefficients available in the literature was done. The emphasis was for liquid-liquid phases and the main mathematical forms of the correlations accessible are reported. In general, there is a necessity of general models. More work has to be done in this area in order to establish more general models that permit reporting

VICTOR VASQUEZ; RENATO G. BAUTISTA

1997-01-01

249

Decreased-activity mutants of phosphoglucose isomerase in the cytosol and chloroplast of Clarkia xantiana. Impact on mass-action ratios and fluxes to sucrose and starch, and estimation of Flux Control Coefficients and Elasticity Coefficients.  

PubMed Central

1. Subcellular-compartment-specific decreased-activity mutants of phosphoglucose isomerase in Clarkia xantiana were used to analyse the control of sucrose and starch synthesis during photosynthesis. Mutants were available in which the plastid phosphoglucose isomerase complement is decreased to 75% or 50% of the wild-type level, and the cytosol complement to 64%, 36% or 18% of the wild-type level. 2. The effects on the [product]/[substrate] ratio and on fluxes to sucrose or starch and the rate of photosynthesis were studied with the use of saturating or limiting light intensity to impose a high or low flux through these pathways. 3. Removal of a small fraction of either phosphoglucose isomerase leads to a significant shift of the [product]/[substrate] ratio away, from equilibrium. We conclude that there is no 'excess' of enzyme over that needed to maintain its reactants reasonably close to equilibrium. 4. Decreased phosphoglucose isomerase activity can also alter the fluxes to starch or sucrose. However, the effect on flux does not correlate with the extent of disequilibrium, and also varies depending on the subcellular compartment and on the conditions. 5. The results were used to estimate Flux Control Coefficients for the chloroplast and cytosolic phosphoglucose isomerases. The chloroplast isoenzyme exerts control on the rate of starch synthesis and on photosynthesis in saturating light intensity and CO2, but not at low light intensity. The cytosolic enzyme only exerts significant control when its complement is decreased 3-5-fold, and differs from the plastid isoenzyme in exerting more control in low light intensity. It has a positive Control Coefficient for sucrose synthesis, and a negative Control Coefficient for starch synthesis. 6. The Elasticity Coefficients in vivo of the cytosolic phosphoglucose isomerase were estimated to lie between 5 and 8 in the wild-type. They decrease in mutants with a lowered complement of cytosolic phosphoglucose isomerase. 7. The implications of these results for regulation and for evolution are discussed. PMID:2775228

Kruckeberg, A L; Neuhaus, H E; Feil, R; Gottlieb, L D; Stitt, M

1989-01-01

250

Liquid Phase Epitaxial Growth and Heterointerface Characteristics of Long-Wavelength Indium - Gallium Arsenide - Phosphide Heterostructures  

NASA Astrophysics Data System (ADS)

Data are presented that demonstrate that the InGaAsP quaternary grown by constant temperature liquid phase epitaxy on InP substrate can, under certain growth conditions, exhibit considerably narrower diffraction profile half -widths than previously reported. The double crystal x -ray diffraction half-width is a relatively new assay of crystalline alloy compositional homogeneity, and the 13 arc sec value presented here for InGaAsP may represent a lower limit for the homogeneity of this material system, as a result of alloy effects. Bandgap and lattice constant data are given that characterize the transient composition that occurs at the onset of liquid phase epitaxial growth of InGaAsP on InP substrates. This compositional inhomogeneity, a region of significantly different bandgap and lattice constant than that of the remainder of the layer, is a result of the extreme non-equilibrium conditions that exist in the first milliseconds of growth. The data presented here indicate a shift in mismatch and bandgap of (LESSTHEQ) 16 x 10('-4) and (LESSTHEQ) 20 meV, respectively, as a result of the transient composition. These results permit a calculation of the changes in the individual solidus atomic species, which illuminate some aspects of incorporation kinetic effects. Transmission electron microscopy (TEM) data are presented that characterize the interfacial "damage" that arises during the liquid phase epitaxial growth of an arsenic -poor InGaAsP quatenary on a previously grown arsenic-rich layer. This "damage" takes the form of a ragged heterointerface with extensive dislocations and is observed for some of the heterostructures examined. Other heterostructures are demonstrated that yield high-quality interfaces in TEM, which is corroborated by their performance as room -temperature lasers. Stimulated emission data for single-well quantum well heterostructures (QWH's) permit a direct measurement of the InGaAsP-InP valence-band discontinuity ((DELTA)E(,v)). As the width of a single quantum well grows small, photogenerated electrons are poorly collected, while the heavier-mass holes are efficiently collected. Recombination between "hot" electrons and bound holes produces radiation that is depressed from the InP bandgap energy by (DELTA)E(,v), which is observed in the photoluminescence of single-well QWH's. The photoluminescence method is potentially the most direct and accurate measurement of heterojunction band discontinuities.

Brunemeier, Paul Edward

251

Correlation of microstructural and physical properties in bulk BiFeO3 prepared by rapid liquid-phase sintering  

NASA Astrophysics Data System (ADS)

BiFeO3 sample prepared by rapid liquid phase sintering (RLPS) technique is found to posses better dielectric properties than the subsequently annealed sample. These samples also show ferromagnetism at room temperature. Detailed X-ray diffraction and Rietveld refinement of the data show that oxygen-iron-oxygen (O-Fe-O) bond angle is considerably more distorted in samples prepared by rapid liquid-phase sintering technique than in the annealed sample. In addition, synchrotron X-ray diffraction as well as high resolution transmission electron microscopy studies show higher concentration of impurity phases in the annealed samples, which is the likely reason for inferior dielectric properties. Further transmission electron microscopy results indicate that high crystalline order is not necessary for better dielectric properties. However weak ferromagnetism is observed in all these samples and appears to be the intrinsic property of samples prepared by rapid liquid phase sintering technique.

Sagdeo, Archna; Mondal, Puspen; Upadhyay, Anuj; Sinha, A. K.; Srivastava, A. K.; Gupta, S. M.; Chowdhury, P.; Ganguli, Tapas; Deb, S. K.

2013-04-01

252

Activity coefficients of NaCl in trehalose-water and maltose-water mixtures at 298.15 K.  

PubMed

The ionic mean activity coefficients of NaCl in trehalose-water and maltose-water mixtures have been experimentally determined at 298.15 K from emf measurements by electrochemical cell containing ion selective electrodes (ISE): Na-ISE/NaCl (m), sugar (Y%), H(2)O (100-Y%)/Cl-ISE. The electrolyte molality (m) ranged between 0.01 and 3 mol kg(-1), approximately, and the weight percent (Y%) of sugar in the mixture of solvents between 0, 10, 20, 30 and 40%. The system is considered as an electrolyte in a mixture of solvents and the data have been analysed by using the Debye-Hückel and Pitzer equations. The results obtained with both equations are in quite agreement with each other. The variation of the fit parameter from both equations were studied relative to the change in the dielectric properties of the mixture of solvents. Standard free energy of transference were comparatively discussed in terms of ion-solvent, ion-ion interactions and the hydration of both the electrolyte and the sugar. PMID:12801715

Hernández-Luis, Felipe; Amado-González, Eliseo; Esteso, Miguel A

2003-06-23

253

Liquid-liquid phase separation in particles containing organics mixed with ammonium sulfate, ammonium bisulfate, ammonium nitrate or sodium chloride  

NASA Astrophysics Data System (ADS)

As the relative humidity varies from high to low values in the atmosphere, particles containing organic species and inorganic salts may undergo liquid-liquid phase separation. The majority of the laboratory work on this subject has used ammonium sulfate as the inorganic salt. In the following we studied liquid-liquid phase separation in particles containing organics mixed with the following salts: ammonium sulfate, ammonium bisulfate, ammonium nitrate and sodium chloride. In each experiment one organic was mixed with one inorganic salt and the liquid-liquid phase separation relative humidity (SRH) was determined. Since we studied 23 different organics mixed with four different salts, a total of 92 different particle types were investigated. Out of the 92 types, 49 underwent liquid-liquid phase separation. For all the inorganic salts, liquid-liquid phase separation was never observed when the oxygen-to-carbon elemental ratio (O : C) ≥ 0.8 and was always observed for O : C < 0.5. For 0.5 ≤ O : C < 0.8, the results depended on the salt type. Out of the 23 organic species investigated, the SRH of 20 organics followed the trend: (NH4)2SO4 ≥ NH4HSO4 ≥ NaCl ≥ NH4NO3. This trend is consistent with previous salting out studies and the Hofmeister series. Based on the range of O : C values found in the atmosphere and the current results, liquid-liquid phase separation is likely a frequent occurrence in both marine and non-marine environments.

You, Y.; Renbaum-Wolff, L.; Bertram, A. K.

2013-12-01

254

Method for forming single phase, single crystalline 2122 BCSCO superconductor thin films by liquid phase epitaxy  

NASA Technical Reports Server (NTRS)

A substantially single phase, single crystalline, highly epitaxial film of Bi.sub.2 CaSr.sub.2 Cu.sub.2 O.sub.8 superconductor which has a T.sub.c (zero resistance) of 83 K is provided on a lattice-matched substrate with no intergrowth. This film is produced by a Liquid Phase Epitaxy method which includes the steps of forming a dilute supercooled molten solution of a single phase superconducting mixture of oxides of Bi, Ca, Sr, and Cu having an atomic ratio of about 2:1:2:2 in a nonreactive flux such as KCl, introducing the substrate, e.g., NdGaO.sub.3, into the molten solution at 850.degree. C., cooling the solution from 850.degree. C. to 830.degree. C. to grow the film and rapidly cooling the substrate to room temperature to maintain the desired single phase, single crystalline film structure.

Pandey, Raghvendra K. (Inventor); Raina, Kanwal (Inventor); Solayappan, Narayanan (Inventor)

1994-01-01

255

Liquid Phase - Pulsed Laser Ablation: A route to fabricate different carbon nanostructures  

NASA Astrophysics Data System (ADS)

Carbon nanostructures in various forms and sizes, and with different speciation properties have been prepared from graphite by Liquid Phase - Pulsed Laser Ablation (LP-PLA) using a high frequency Nd:YAG laser. High energy densities and pulse repetition frequencies of up to 10 kHz were used in this ablation process to produce carbon nanomaterials with unique chemical structures. Dynamic Light Scattering (DLS), micro-Raman and High-Resolution Transmission Electron Microscopy (HRTEM) were used to confirm the size distribution, morphology, chemical bonding, and crystallinity of these nanostructures. This article demonstrates how the fabrication process affects measured characteristics of the produced carbon nanomaterials. The obtained particle properties have potential use for various applications including biochemical speciation applications.

Al-Hamaoy, Ahmed; Chikarakara, Evans; Jawad, Hussein; Gupta, Kapil; Kumar, Dinesh; Rao, M. S. Ramachandra; Krishnamurthy, Satheesh; Morshed, Muhammad; Fox, Eoin; Brougham, Dermot; He, Xiaoyun; Vázquez, Mercedes; Brabazon, Dermot

2014-05-01

256

Salt-induced liquid-liquid phase separation of protein-surfactant complexes  

NASA Astrophysics Data System (ADS)

We report the cloud-point curve determination of lysozyme-sodium-doderyl-sulfate (SDS) complexes in solution. By varying the pH, salt concentration, and relative ratio of lysozyme to SDS, the phenomenon of clouding and liquid-liquid phase separation is investigated under different solution conditions. For the temperature, concentration, and pH ranges used in this study, the clouding phenomenon appears to be controlled by the electrostatic interaction between the lysozyme-SDS complexes. Any change in the solution condition that leads to a decrease in the charge on the lysozyme-SDS complexes results in an increase in cloud-point temperature. A generalized Flory-Huggins theory for polydisperse polymers is used to describe the cloud-point curve.

Narayanan, Janaky; Deotare, Vinod W.

1999-10-01

257

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

NASA Astrophysics Data System (ADS)

Transient-liquid phase (TLP) bonding of a nickel-based superalloy, IN 738, was performed. Contrary to conventional TLP bonding analytical models, which assume a parabolic relationship between liquid/solid interface migration and holding time, deviation from this law was observed experimentally and by numerical simulation. The deviation, which is caused by reduction in solute concentration gradient below a critical value, is suggested as an alternate phenomenon responsible for anomalous extension of processing time required to produce an eutectic-free joint with increase in bonding temperature. A decrease in the filler gap size and the use of a melting-point depressant (MPD) solute with higher solubility in the base material could reduce the occurrence of the anomalous behavior during a high-temperature TLP joining process.

Abdelfatah, M. M.; Ojo, O. A.

2009-02-01

258

Finite difference computation of solid/liquid phase change energy transport - Comparison with experimental data  

NASA Astrophysics Data System (ADS)

A computational model is presented for the prediction of solid/liquid phase change energy transport including the influence of free convection and comparisons made with experimental data for which the phase change material is heated from the side and from below. The computational model considers the velocity components of all nonliquid PCM control volumes to be zero but fully solves the coupled mass-momentum problem within the liquid. The thermal energy model includes the entire domain and employs an enthalpy-like model in addition to recent development for handling the phase change interface non-linearily. The predictions are compared with experimental data for the test problem examined. The present procedure demonstrates both excellent agreement with the experimental data and a significant computational advance for this class of problem.

Schneider, G. E.

1986-01-01

259

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

260

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

PubMed Central

Ex situ spectroscopic ellipsometry (SE) measurements have been employed to investigate the effect of liquid-phase hydrofluoric acid (HF) cleaning on Si<100> surfaces for microelectromechanical systems application. The hydrogen terminated (H-terminated) Si surface was realized as an equivalent dielectric layer, and SE measurements are performed. The SE analyses indicate that after a 20-s 100:5 HF dip with rinse, the Si (100) surface was passivated by the hydrogen termination and remained chemically stable. Roughness of the HF-etched bare Si (100) surface was observed and analyzed by the ex-situ SE. Evidence for desorption of the H-terminated Si surface layer is studied using Fourier transform infrared spectroscopy and ellipsometry, and discussed. This piece of work explains the usage of an ex situ, non-destructive technique capable of showing state of passivation, the H-termination of Si<100> surfaces. PMID:24619506

Kurhekar, Anil Sudhakar; Apte, Prakash R

2014-01-01

261

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

262

Barium Hexaferrite Thick Films Made by Liquid Phase Epitaxy Reflow Method  

NASA Astrophysics Data System (ADS)

In this work, we report on the growing of BaFe12O19(or BaM) thick films on (0001) sapphire Al2O3 substrate. Our goal is to fabricate barium ferrite thick films which can be self-biased for circulator application. We have modified the liquid phase epitaxy (LPE) method by conducting the experiment in vacuum. A small chunk piece of the melt weighing about 0.035 g was placed on 1cm x 1cm Al2O3 substrate and remelted at 1200^oC for one hour. The thickness of our thick films grown by this reflow method range from 300 to 550 ?m. The coercivities of the thick films in the perpendicular direction were about 100Oe.

Abuzir, Alaaedeen

2006-05-01

263

Harnessing the liquid-phase exfoliation of graphene using aliphatic compounds: a supramolecular approach.  

PubMed

The technological exploitation of the extraordinary properties of graphene relies on the ability to achieve full control over the production of a high-quality material and its processing by up-scalable approaches in order to fabricate large-area films with single-layer or a few atomic-layer thickness, which might be integrated in working devices. A simple method is reported for producing homogenous dispersions of unfunctionalized and non-oxidized graphene nanosheets in N-methyl-2-pyrrolidone (NMP) by using simple molecular modules, which act as dispersion-stabilizing compounds during the liquid-phase exfoliation (LPE) process, leading to an increase in the concentration of graphene in dispersions. The LPE-processed graphene dispersion was shown to be a conductive ink. This approach opens up new avenues for the technological applications of this graphene ink as low-cost electrodes and conducting nanocomposite for electronics. PMID:25044532

Ciesielski, Artur; Haar, Sébastien; El Gemayel, Mirella; Yang, Huafeng; Clough, Joseph; Melinte, Georgian; Gobbi, Marco; Orgiu, Emanuele; Nardi, Marco V; Ligorio, Giovanni; Palermo, Vincenzo; Koch, Norbert; Ersen, Ovidiu; Casiraghi, Cinzia; Samorì, Paolo

2014-09-22

264

Regulating surface wettability of PEO/PLLA composite electrospun nanofibrous membrane for liquid phase filtration  

NASA Astrophysics Data System (ADS)

The PEO/PLLA composite nanofibrous membranes were prepared by electrospinning technique for liquid phase filtration application. In this experiment, PLLA homopolymer and PLLA-PEG copolymer were added into PEO solution to increase hydrophobicity of nanofibrous membrane surface. PLLA content was fixed at 30% by weight of total solid. Morphology and fiber diameter were characterized from scanning electron microscope (SEM) images. Fiber diameters of PEO/PLLA homopolymer and PEO/PLLA-PEG copolymer are 582+/-78 nm and 657+/-167 nm, respectively. Surface wettability property of PEO/PLLA composite nanofibrous membranes were measured by apparent water contact angle. The apparent water contact angle value of PEO/PLLA is 120°+/-2°, while PEO/PEG-b-PLLA is 99°+/-7°. The surface wettability of PEO/PLLA composite nanofibrous membranes can be modified by varying type of polymer.

Poonsit, Lalada; Sunthornvarabhas, Jackapon; Akira, Ito; Lertworasirikul, Amornrat

2014-06-01

265

Methods for sulfate removal in liquid-phase catalytic hydrothermal gasification of biomass  

DOEpatents

Processing of wet biomass feedstock by liquid-phase catalytic hydrothermal gasification must address catalyst fouling and poisoning. One solution can involve heating the wet biomass with a heating unit to a pre-treatment temperature sufficient for organic constituents in the feedstock to decompose, for precipitates of inorganic wastes to form, for preheating the wet feedstock in preparation for subsequent removal of soluble sulfate contaminants, or combinations thereof. Processing further includes reacting the soluble sulfate contaminants with cations present in the feedstock material to yield a sulfate-containing precipitate and separating the inorganic precipitates and/or the sulfate-containing precipitates out of the wet feedstock. Having removed much of the inorganic wastes and the sulfate contaminants that can cause poisoning and fouling, the wet biomass feedstock can be exposed to the heterogeneous catalyst for gasification.

Elliott, Douglas C; Oyler, James R

2014-11-04

266

Crystallization and Phase Changes in Paracetamol from the Amorphous Solid to the Liquid Phase  

PubMed Central

For the case of paracetamol, we show how terahertz time-domain spectroscopy can be used to characterize the solid and liquid phase dynamics. Heating of supercooled amorphous paracetamol from 295 K in a covered sample under vacuum leads to its crystallization at 330 K. First, form III is formed followed by the transformation of form III to form II at 375 K, to form I at 405 K, and finally melting is observed around 455 K. We discuss the difference between the featureless spectra of the supercooled liquid and its liquid melt. Lastly, we studied the onset of crystallization from the supercooled liquid in detail and quantified its kinetics based on the Avrami–Erofeev model. We determined an effective rate constant of k = 0.056 min–1 with a corresponding onset of crystallization at T = 329.5 K for a heating rate of 0.4 K min–1. PMID:24579729

2014-01-01

267

Liquid-phase thermodynamics and structures in the Cu-Nb binary system  

NASA Astrophysics Data System (ADS)

An embedded atom method (EAM) interatomic potential is constructed to reproduce the main topological features of the experimental equilibrium phase diagram of the Cu-Nb system in both solid and liquid states. The potential is fitted to composition-dependent enthalpies of mixing for bcc and fcc random solid solutions obtained from first-principles calculations at 0 K. Compared with two other EAM Cu-Nb potentials in the literature, the phase diagram of the current potential shows better agreement with the experimental phase diagram. Our potential predicts that the Cu-Nb liquid phase at equilibrium is compositionally patterned over lengths of about 2.3 nm. The newly constructed potential may be used to study the effect of liquid thermodynamics and structure on properties of binary systems, such as radiation-induced mixing.

Zhang, Liang; Martinez, Enrique; Caro, Alfredo; Liu, Xiang-Yang; Demkowicz, Michael J.

2013-03-01

268

Luminescence from erbium-doped silicon epi layers grown by liquid-phase epitaxy  

SciTech Connect

Dislocation-related photoluminescence at 0.806 and 0.873 eV is observed in erbium-doped silicon epi layers grown by liquid-phase epitaxy on (100) Si wafers. These signals are detected at T = 2 K only on epi layers deposited on Czochralski grown silicon substrates. No luminescence is observed when float zone-grown substrates are used. The peak intensity shows temperature quenching, but the signal remains detectable up to 195 K. The luminescence apparently is due to dislocations in silicon in the simultaneous presence of high oxygen concentration and erbium impurities. A comparison with the typical infrared emission from erbium-implanted silicon samples is presented.

Pizzini, S.; Donghi, M.; Binetti, S.; Wagner, G.; Bersani, M. [Univ. Degli Studi di Milano, Milan (Italy)

1998-01-01

269

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

270

Microwave-enhanced liquid-phase synthesis of thiohydantoins and thioxotetrahydropyrimidinones.  

PubMed

An efficient, microwave-assisted method for the liquid-phase combinatorial synthesis of 3,5-disubstituted thiohydantoins and 3,5-disubstituted 2-thioxotetrahydropyrimidin-4-ones has been developed. In synthesizing thiohydantoins, Fmoc-protected amino acids were coupled with polymer support and then deprotected to give primary amines. While in synthesizing thioxotetrahydropyrimidinones, 3-chloropropionyl chloride was immobilized to the support and subsequently reacted with various amines to form secondary amines. The PEG bound primary/secondary amines then were incorporated with various isothiocyanates to give thiourea intermediates and concomitant cyclization/cleavage steps occurred under mild basic condition. The desired products were then liberated from the soluble matrix in good yield and purity. All reactions described here were performed under microwave irradiation. PMID:14870850

Yeh, Wen-Ben; Lin, Mei-Jung; Lee, Ming-Juan; Sun, Chung-Ming

2003-01-01

271

Liquid-phase deposition of thin Si films by ballistic electro-reduction  

NASA Astrophysics Data System (ADS)

It is shown that the nanocryatalline silicon ballistic electron emitter operates in a SiCl4 solution without using any counter electrodes and that thin amorphous Si films are efficiently deposited on the emitting surface with no contaminations and by-products. Despite the large electrochemical window of the SiCl4 solution, electrons injected with sufficiently high energies preferentially reduce Si4+ ions at the interface. Using an emitter with patterned line emission windows, a Si-wires array can be formed in parallel. This low-temperature liquid-phase deposition technique provides an alternative clean process for power-effective fabrication of advanced thin Si film structures and devices.

Ohta, T.; Gelloz, B.; Kojima, A.; Koshida, N.

2013-01-01

272

Effects of molecular weight and temperature on liquid-liquid phase separation in particles containing organic species and ammonium sulfate  

NASA Astrophysics Data System (ADS)

Atmospheric particles containing organic species and inorganic salts may undergo liquid-liquid phase separation when the relative humidity varies between high and low values. To better understand the parameters that affect liquid-liquid phase separation in atmospheric particles, we studied the effects of molecular weight and temperature on liquid-liquid phase separation in particles containing one organic species mixed with ammonium sulfate. In the molecular weight dependent studies, we measured liquid-liquid phase separation relative humidity (SRH) in particles containing ammonium sulfate and organic species with large molecular weights (up to 1153 Da). These results were combined with recent studies of liquid-liquid phase separation in the literature to assess if molecular weight is a useful parameter for predicting SRH. The combined results, which include results from 33 different particle types, illustrate that SRH does not depend strongly on molecular weight (i.e. a clear relationship between molecular weight and SRH was not observed). In the temperature dependent studies, we measured liquid-liquid phase separation in 20 particle types at 244 ± 1 K, 263 ± 1 K, and 278 ± 1 K, as well as 290 ± 1 K for a few of these particle types. These new results were combined with previous measurements of the same particle types at 290 ± 1 K. The combined SRH data illustrate that for the particle types studied the SRH does not depend strongly on temperature. At most the SRH varied by 9.7% as the temperature varied from 290 to 244 K. In addition, for all the particle types studied and at all the temperatures studied, liquid-liquid phase separation was always observed when the O : C < 0.57, frequently observed when 0.57 ? O : C < 0.8, and never observed when O : C ? 0.8. These combined results suggest that liquid-liquid phase separation is likely a common occurrence in the atmospheric particles at temperatures from 244-290 K. Additional studies at temperatures < 244 K and with other organic species are still needed.

You, Y.; Bertram, A. K.

2014-09-01

273

An immersed boundary-thermal lattice Boltzmann method for solid-liquid phase change  

NASA Astrophysics Data System (ADS)

In this work, an immersed boundary-thermal lattice Boltzmann method (IB-TLBM) is proposed to simulate solid-liquid phase change problems. To treat the velocity and temperature boundary conditions on the solid-liquid interface, immersed boundary method (IBM) is adopted, in which the solid-liquid interface is represented as a sharp interface rather than a diffusive interface and is tracked explicitly by Lagrangian grid. The surface forces along the immersed boundary, including the “momentum force” for velocity boundary condition and the “energy force” for temperature boundary condition, are calculated by the direct-forcing scheme. The moving velocity of solid-liquid interface induced by phase change is calculated by the amount of latent heat absorbed or released in a time step directly, with no need to compute temperature gradients in solid and liquid phases separately. The temperature on the solid-liquid interface is specified as the melting temperature, which means phase change happens at a constant temperature. As the solid-liquid interface evolves with time, the identification of phase of Eulerian points and the rearrangement of Lagrangian points are also considered. With regard to the velocity and temperature fields, passive scalar thermal lattice Boltzmann method (TLBM) with multiple-relaxation-time (MRT) collision schemes is adopted. Numerical examples, including conduction-induced melting in a semi-infinite space and melting in a square cavity, are carried out to verify the present method and good results are obtained. As a further application, melting in a circular cylinder with considering the motion of solid phase is simulated successfully by the present method; numerical results show that the motion of solid phase accelerates the melting process obviously.

Huang, Rongzong; Wu, Huiying

2014-11-01

274

Liquid-phase hydrogenation of citral over Pt/SiO{sub 2} catalysts. 2. Hydrogenation of reaction intermediate compounds  

SciTech Connect

Liquid-phase hydrogenation of the four principal reaction intermediates formed during citral hydrogenation, i.e., nerol, geraniol, citronellal, and citronellol, was studied at 298 and 373 K under 20 atm H{sub 2} at concentrations of 0.5 to 1.0 M in hexane. A decrease in the initial reaction rate as temperature increased from 298 to 373 K was exhibited during the hydrogenation of all four compounds, just as reported earlier for citral; however, the decrease in rate at 373 K was only one-half for citronellal whereas it was orders of magnitude greater for nerol and geraniol. Furthermore, simultaneous hydrogenation of citronellal and geraniol at 298 K resulted in a continuous decrease in the rate of citronellal disappearance in contrast to the nearly constant rate of disappearance observed during hydrogenation of citronellal alone. Competitive hydrogenation of citral with either geraniol or citronellal showed that geraniol hydrogenation to citronellol is kinetically insignificant during citral hydrogenation at 373 K. The initial activity for hydrogenation of the intermediates at 298 K follows the following trend: geraniol > nerol < citronellol < E-citral, citronellal > Z-citral. Based on the relative hydrogenation rates of the intermediate alone versus its hydrogenation in the presence of other reactants, the relative size of the adsorption equilibrium constants for the various organic compounds appears to be as follows: citral > citronellal > geraniol, nerol > citronellol > 3,7-dimethyloctanol. This study indicates that activation of the C{double_bond}O bond should be performed at higher reaction temperatures to maximize selectivity to the unsaturated alcohols.

Singh, U.K.; Sysak, M.N.; Vannice, M.A.

2000-04-01

275

Unraveling the behavior of the individual ionic activity coefficients on the basis of the balance of ion-ion and ion-water interactions  

E-print Network

We investigate the individual activity coefficients of pure 1:1 and 2:1 electrolytes using our theory that is based on the competition of ion-ion (II) and ion-water (IW) interactions (Vincze et al., J. Chem. Phys. 133, 154507, 2010). The II term is computed from Grand Canonical Monte Carlo simulations on the basis of the implicit solvent model of electrolytes using hard sphere ions with Pauling radii. The IW term is computed on the basis of Born's treatment of solvation using experimental hydration free energies. The two terms are coupled through the concentration-dependent dielectric constant of the electrolyte. With this approach we are able to reproduce the nonmonotonic concentration dependence of the mean activity coefficient of pure electrolytes qualitatively without using adjustable parameters. In this paper, we show that the theory can provide valuable insight into the behavior of individual activity coefficients too. We compare our theoretical predictions against experimental data measured by electrochemical cells containing ion-specific electrodes. As in the case of the mean activity coefficients, we find good agreement for 2:1 electrolytes, while the accuracy of our model is worse for 1:1 systems. This deviation in accuracy is explained by the fact that the two competing terms (II and IW) are much larger in the 2:1 case so errors in the two separate terms have less effects. The difference of the excess chemical potentials of cations and anions (the ratio of activity coefficients) is determined by asymmetries in the properties of the two ions: charge, radius, and hydration free energies.

Mónika Valiskó; Dezs? Boda

2014-09-15

276

Transient Liquid Phase Diffusion Bonding of Magnesium Alloy (Mg-AZ31) to Titanium Alloy (Ti-6Al-4V)  

NASA Astrophysics Data System (ADS)

The magnesium alloy Mg-AZ31 and titanium alloy Ti-6Al-4V have physical characteristics and mechanical properties that makes it attractive for a wide range of engineering applications in the aerospace and automotive industries. However, the differences in melting temperature and coefficient of thermal expansion hinder the use of traditional fusion welding techniques. Transient liquid phase (TLP) bonding of magnesium alloy Mg-AZ31 and titanium alloy Ti-6Al- 4V was performed and different interlayer types and configurations were used to facilitate joint formation. The joining of these alloys using Ni foils was successful at a bonding temperature of 515°C, bonding pressure 0.2 MPa, for bonding time of 5 minutes. At the Ni/Mg-AZ31 bond interface, the formation of a eutectic liquid between Mg and Ni was observed. The formation of Mg2Ni and Mg3AlNi2 were identified along the bond interface resulting in an isothermally solidified joint. At the Ni/Ti-6Al-4V interface, the solid-state diffusion process results in joint formation. The use of double Ni-Cu sandwich joint resulted in further enhancement in joint formation and this produced joints with greater shear strength values. The configuration of Mg-AZ31/Cu- Ni/Ti-6Al-4V or Mg-AZ31/Ni-Cu/Ti-6Al-4V influence the mechanism of bonding and the type of intermetallics formed within the joint. The application of thin Ni electrodeposited coatings resulted in further enhancements of joint quality due to better surface-to-surface contact and a reduction in the formation of intermetallics at the joint. The effect of Cu nano-particles in the coatings was found to decrease the eutectic zone width and this resulted in an increase the shear strength of the joints. The highest shear strength of 69 MPa was possible with bonds made using coatings containing Cu nano-particle dispersion.

Atieh, Anas Mahmoud

277

Effect of liquid phase composition on the microstructure and properties of (W,Ti)C cemented carbide cutting tools  

E-print Network

constituent is tungsten carbide (WC) with 70­90 vol% content; this constituent improves the hardness at lowEffect of liquid phase composition on the microstructure and properties of (W,Ti)C cemented carbide: Received 15 July 2007 Accepted 4 April 2008 Keywords: (W,Ti)C Cemented carbides Microstructure Hardness

Hong, Soon Hyung

278

Liquid-phase hydrogenation on new AlPO 4 ?SiO 2 supported rhodium catalysts  

Microsoft Academic Search

The liquid-phase catalytic hydrogenation of various organic compounds was carried out using new rhodium catalysts supported on AlPO4?SiO2 (20?80 wt. %) system, in methanol as solvent, under low hydrogen pressure (0.55 MPa) and at 293 K. Neither alkene isomerization nor hydrogenolysis products were detected in any of the cases.

J. M. Campelo; A. Garcia; D. Luna; J. M. Marinas

1982-01-01

279

Pyrolysis in the Liquid Phase Inside Single Droplets of Light Oil Studied with Laser Light Scattering Methods  

Microsoft Academic Search

A new optical set up for the measurement of the angular distribution of the polarized components of light scattered by single droplets has been realized. It allows the simultaneous determination of the size, velocity and complex refractive index of the droplets. The vaporization and chemical transformation in the liquid phase have been studied with this technique in the temperature range

P. MASSOLI; F. BERETTA; A. DALESSIO

1990-01-01

280

Limits of stability of the liquid phase in a lattice model with water-like Srikanth Sastry  

E-print Network

Limits of stability of the liquid phase in a lattice model with water-like properties Srikanth properties of water, while an alternate, thermodynamicapproach is offered by the reentrant limit of stability- perimental studies have established that the anomalous properties of water are related to the hydrogen bond

Sciortino, Francesco

281

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

282

Influence of process parameters on microstructure of transient liquid phase bonded Inconel 738LC superalloy with Amdry DF3 interlayer  

Microsoft Academic Search

The effect of bonding temperature and time on microstructure of diffusion brazed joint of nickel base superalloy Inconel 738LC using Amdry DF-3 filler, alloy was investigated. It was observed that the formation of eutectic microconstituents, within the joint regions, was significantly influenced by the brazing temperature and time. A deviation from the conventional transient liquid phase (TLP) bonding diffusion models

N. P. Wikstrom; O. A. Ojo; M. C. Chaturvedi

2006-01-01

283

Effect of bonding temperature on isothermal solidification rate during transient liquid phase bonding of Inconel 738LC superalloy  

Microsoft Academic Search

A commercial cast Inconel 738 superalloy was transient liquid phase (TLP) bonded using a commercial Ni–Cr–B filler alloy, Nicrobraz 150. In contrast to the solidification behavior predicted by the current TLP models, isothermal solidification occurred under two separate regimes, depending on the bonding temperature. The rate of isothermal solidification in the first regime was faster than in the second regime.

O. A. Idowu; N. L. Richards; M. C. Chaturvedi

2005-01-01

284

Transient-Liquid-Phase (TLP) Bonding of Al2O3 Using Nb-based Multilayer Interlayers.  

E-print Network

??Transient-liquid-phase (TLP) bonding was used to join high-strength, high-purity Al2O3 ceramic. This method uses a multilayer interlayer (B/A/B sandwich structure), which forms thin transient-liquid layers… (more)

Hong, Sung Moo

2009-01-01

285

Saddle-like deformation in a dielectric elastomer actuator embedded with liquid-phase gallium-indium electrodes  

E-print Network

Saddle-like deformation in a dielectric elastomer actuator embedded with liquid-phase gallium properties of liquid gallium and eutectic gallium-indium Phys. Fluids 24, 063101 (2012); 10); 10.1063/1.3670048 Evaluation of gallium-indium alloy as an acoustic couplant for high-impedance, high

Deseri, Luca

286

Effects of unsteady state conditions on the biooxidation of methyl ethyl and methyl isobutyl ketone in continuous flow liquid phase cultures  

E-print Network

in continuous flow liquid phase cultures D.P. Geoghegan, G. Hamer, M.A. Deshusses Abstract The effects liquid waste streams. Both MEK and MIBK have been designated high-priority toxic chemicals [2] in spite, but details of the kinetics of such biodegradation processes are scant, particularly in liquid phase cultures

287

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

288

Advanced far infrared blocked impurity band detectors based on germanium liquid phase epitaxy  

NASA Technical Reports Server (NTRS)

This research has shown that epilayers with residual impurity concentrations of 5 x 10(sup 13) cm(exp -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 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(exp -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.

1998-01-01

289

Segregation to interphase boundaries in liquid-phase sintered tungsten alloys  

NASA Astrophysics Data System (ADS)

Scanning Auger electron spectroscopy has been used to examine the distribution of impurity elements on the fracture surfaces of liquid-phase sintered W-Ni-Cu and W-Ni-Fe alloys. On the interphase boundaries between the fcc Ni-based matrix phase and the tungsten particles, segregation levels of ~0.4 and ~0.2 monolayers of phosphorus have been observed in as-sintered, furnace-cooled specimens of W-Ni-Cu and W-Ni-Fe, respectively. The phosphorus is homogeneously distributed but at fracture adheres preferentially to the matrix phase. High temperature heat treatment (1350 °C) followed by water quenching reduces significantly the phosphorus segregation and improves the degree of cohesion across these boundaries. Segregated sulfur is detected on both sides of the interphase boundaries after fracture. The sulfur is much less uniformly distributed than the phosphorus, and its segregation level increases in the heat treated specimens. Copper also segregates to the interphase boundaries during the heat treatment of W-Ni-Cu specimens, but no equivalent segregation of iron was observed in the W-Ni-Fe system. The boundaries developed between adjacent tungsten particles are free of impurity contamination in both alloy systems but have a segregated layer of nickel.

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

1983-03-01

290

Phase equilibria in InAsSbP quaternary alloys grown by liquid phase epitaxy  

NASA Astrophysics Data System (ADS)

The quaternary alloy InAs1-x-ySbxPy, lattice-matched to InAs, is a promising material for the production of infrared light sources for the detection of gases in the 2 4 ?m region of the spectrum. In this work, thermodynamic phase equilibrium calculations have been carried out to determine the compositions required for liquid phase epitaxial growth and the extent of the miscibility gap in the solid material. For high band gap materials, the desired growth temperature is found to be intermediate between a low temperature required to grow P-rich solids and higher temperatures required to avoid spinodal decomposition. Conventional LPE growth at an intermediate temperature of 583°C is found to produce good material with high luminescence efficiency and excellent optical characteristics. Problems with phosphorus loss from the melt are also discussed and lower growth temperatures are found to considerably reduce this problem. Growth in the metastable region between the binodal and spinodal lines has been achieved with the production of phosphorus-rich solids with concentrations up to y = 0.445.

Wilson, M. R.; Krier, A.; Mao, Y.

1996-09-01

291

Glass-liquid phase separation in highly supersaturated aqueous solutions of telaprevir.  

PubMed

Amorphous solid dispersions are of great current interest because they can improve the delivery of poorly water-soluble compounds. It has been recently noted that the highly supersaturated solutions generated by dissolution of some ASDs can undergo a phase transition to a colloidal, disordered, drug-rich phase when the concentration exceeds the "amorphous solubility" of the drug. The purpose of this study was to investigate the phase behavior of supersaturated solutions of telaprevir, which is formulated as an amorphous solid dispersion in the commercial product. Different analytical techniques including proton nuclear magnetic resonance spectroscopy (NMR), ultraviolet spectroscopy (UV), fluorescence spectroscopy and flux measurements were used to evaluate the properties of aqueous supersaturated solutions of telaprevir. It was found that highly supersaturated solutions of telaprevir underwent glass-liquid phase separation (GLPS) when the concentration exceeded 90 ?g/mL, forming a water-saturated colloidal, amorphous drug-rich phase with a glass transition temperature of 52 °C. From flux measurements, it was observed that the "free" drug concentration reached a maximum at the concentration where GLPS occurred, and did not increase further as the concentration was increased. This phase behavior, which results in a precipitate and a metastable equilibrium between a supersaturated solution and a drug-rich phase, is obviously important in the context of evaluating amorphous solid dispersion formulations and their crystallization routes. PMID:25541813

Mosquera-Giraldo, Laura I; Taylor, Lynne S

2015-02-01

292

Liquid-phase reactions induced by atmospheric pressure glow discharge with liquid electrode  

NASA Astrophysics Data System (ADS)

We experimentally investigated some of the initial reactions in a liquid induced by electron or positive-ion irradiation from an atmospheric-pressure dc glow discharge in contact with the liquid. We used an H-shaped glass reactor to observe the effects of electron irradiation and positive-ion irradiation on the liquid-phase reaction separately and simultaneously. Aqueous solutions of NaCl, AgNO3, HAuCl4, and FeCl2 are used as the electrolyte. Solutions of AgNO3 and HAuCl4 are used for the generation of Ag and Au nanoparticles, respectively. Solution of FeCl2 is used for the generation of ferromagnetic particles. Experimental results showed that electron irradiation of the liquid surface generates OH? in water and that positive-ion irradiation of the liquid surface generates H+ in water even without the dissolution of gas-phase nitrogen oxide. A possible reaction process is qualitatively discussed. We also showed that the control of reductive and oxidative environment in the liquid is possible not only by the gas composition for the plasma generation but also by the liquid composition.

Tochikubo, Fumiyoshi; Shirai, Naoki; Uchida, Satoshi

2014-12-01

293

Synthesis of structurally well-defined and liquid-phase-processable graphene nanoribbons.  

PubMed

The properties of graphene nanoribbons (GNRs) make them good candidates for next-generation electronic materials. Whereas 'top-down' methods, such as the lithographical patterning of graphene and the unzipping of carbon nanotubes, give mixtures of different GNRs, structurally well-defined GNRs can be made using a 'bottom-up' organic synthesis approach through solution-mediated or surface-assisted cyclodehydrogenation reactions. Specifically, non-planar polyphenylene precursors were first 'built up' from small molecules, and then 'graphitized' and 'planarized' to yield GNRs. However, fabrication of processable and longitudinally well-extended GNRs has remained a major challenge. Here we report a bottom-up solution synthesis of long (>200 nm) liquid-phase-processable GNRs with a well-defined structure and a large optical bandgap of 1.88 eV. Self-assembled monolayers of GNRs can be observed by scanning probe microscopy, and non-contact time-resolved terahertz conductivity measurements reveal excellent charge-carrier mobility within individual GNRs. Such structurally well-defined GNRs may prove useful for fundamental studies of graphene nanostructures, as well as the development of GNR-based nanoelectronics. PMID:24451588

Narita, Akimitsu; Feng, Xinliang; Hernandez, Yenny; Jensen, Søren A; Bonn, Mischa; Yang, Huafeng; Verzhbitskiy, Ivan A; Casiraghi, Cinzia; Hansen, Michael Ryan; Koch, Amelie H R; Fytas, George; Ivasenko, Oleksandr; Li, Bing; Mali, Kunal S; Balandina, Tatyana; Mahesh, Sankarapillai; De Feyter, Steven; Müllen, Klaus

2014-02-01

294

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

SciTech Connect

Making use of detailed classical Monte Carlo simulations, we study the critical properties of a two-dimensional planar spin model on a square lattice composed by weakly interacting helimagnetic chains. We find a large temperature window where the vector chirality order parameter, <{kappa}{sub jk}> = , the key quantity in multiferroic systems, takes nonzero value in the absence of long-range order or quasi-long-range order. The phase diagram we obtain for different strengths of the interchain coupling clearly shows that the weakness of the interchain interaction plays an essential role in order to observe the vector chiral spin liquid phase in a temperature range of up to now unattained width ({approx_equal}7%, to be compared with {approx_equal}1% or less previously reported for fully frustrated models, the only well-investigated systems unambiguously displaying spin-chirality decoupling). The relevance of our results for three-dimensional models is also discussed.

Cinti, Fabio [Department of Physics, University of Alberta, Edmonton, Alberta, Canada T6G 2J1 (Canada); Department of Physics, University of Florence and CNISM, 50019 Sesto Fiorentino (Finland) (Italy); Cuccoli, Alessandro; Rettori, Angelo [Department of Physics, University of Florence and CNISM, 50019 Sesto Fiorentino (Finland) (Italy)

2011-05-01

295

Liquid phase exfoliation of 2D layered materials and their application  

NASA Astrophysics Data System (ADS)

In this work, several materials possessing a layered structure were investigated using a technique of exfoliation in liquid phase to produce few- to mono-layers of the material. Materials exfoliated in such a way included graphite, boron nitride, molybdenum disulfide and tungsten disulfide. Subsequent transmission electron microscopy and accompanying electron diffraction patterns revealed that few and mono layer forms of these materials have been realized through this exfoliation method. Ultraviolet-visible spectroscopy confirmed the shifting of the band gaps in molybdenum and tungsten disulfides that is predicted in reducing the number of layers of these materials and was also used to confirm the band gap of the boron nitride. As a potential application, exfoliated molybdenum disulfide was used in the construction of electrodes for electrical charge storage in an electrochemical double layer capacitor, or supercapacitor, style device. Cyclic voltammetry, galvanostatic charge discharge, and electrochemical impedance spectroscopy measurements were performed using three different electrolytes, which showed good capacitive behavior for these devices. Using the data from electrochemical impedance spectroscopy, equivalent circuit models were generated to represent the systems in different electrolytes. From this, it was determined that the capacitive behavior of these systems was partially diffusion limited.

Winchester, Andrew J.

296

Investigating the solid-liquid phase transition of water nanofilms using the generalized replica exchange method.  

PubMed

The generalized Replica Exchange Method (gREM) was applied to study a solid-liquid phase transition in a nanoconfined bilayer water system using the monatomic water (mW) model. Exploiting optimally designed non-Boltzmann sampling weights with replica exchanges, gREM enables an effective sampling of configurations that are metastable or unstable in the canonical ensemble via successive unimodal energy distributions across phase transition regions, often characterized by S-loop or backbending in the statistical temperature. Extensive gREM simulations combined with Statistical Temperature Weighted Histogram Analysis Method (ST-WHAM) for nanoconfined mW water at various densities provide a comprehensive characterization of diverse thermodynamic and structural properties intrinsic to phase transitions. Graph representation of minimized structures of bilayer water systems determined by the basin-hopping global optimization revealed heterogeneous ice structures composed of pentagons, hexagons, and heptagons, consistent with an increasingly ordered solid phase with decreasing density. Apparent crossover from a first-order solid-liquid transition to a continuous one in nanoconfined mW water with increasing density of the system was observed in terms of a diminishing S-loop in the statistical temperature, smooth variation of internal energies and heat capacities, and a characteristic variation of lateral radial distribution functions, and transverse density profiles across transition regions. PMID:25399190

Lu, Qing; Kim, Jaegil; Farrell, James D; Wales, David J; Straub, John E

2014-11-14

297

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. PMID:19241043

Zhao, Jia; Patwa, Tasneem H.; Pal, Manoj; Qiu, Weilian; Lubman, David M.

2010-01-01

298

Microstructural evolution during transient liquid phase bonding of Inconel 738LC using AMS 4777 filler alloy  

SciTech Connect

IN-738LC nickel-based superalloy was joined by transient liquid phase diffusion bonding using AMS 4777 filler alloy. The bonding process was carried out at 1050 Degree-Sign C under vacuum atmosphere for various hold times. Microstructures of the joints were studied by optical and scanning electron microscopy. Continuous centerline eutectic phases, characterized as nickel-rich boride, chromium-rich boride and nickel-rich silicide were observed at the bonds with incomplete isothermal solidification. In addition to the centerline eutectic products, precipitation of boron-rich particles was observed in the diffusion affected zone. The results showed that, as the bonding time was increased to 75 min, the width of the eutectic zone was completely removed and the joint was isothermally solidified. Homogenization of isothermally solidified joints at 1120 Degree-Sign C for 300 min resulted in the elimination of intermetallic phases formed at the diffusion affected zone and the formation of significant {gamma} Prime precipitates in the joint region. - Highlights: Black-Right-Pointing-Pointer TLP bonding of IN-738LC superalloy was performed using AMS 4777 filler alloy. Black-Right-Pointing-Pointer Insufficient diffusion time resulted in the formation of eutectic product. Black-Right-Pointing-Pointer Precipitation of B-rich particles was observed within the DAZ. Black-Right-Pointing-Pointer The extent of isothermal solidification increased with increasing holding time. Black-Right-Pointing-Pointer Homogenizing of joints resulted in the dissolution of DAZ intermetallics.

Jalilvand, V., E-mail: jalilvand@aut.ac.ir [Department of Mining and Metallurgical Engineering, Amirkabir University of Technology (Tehran Polytechnic), Tehran 15875-4413 (Iran, Islamic Republic of); Omidvar, H. [Department of Mining and Metallurgical Engineering, Amirkabir University of Technology (Tehran Polytechnic), Tehran 15875-4413 (Iran, Islamic Republic of)] [Department of Mining and Metallurgical Engineering, Amirkabir University of Technology (Tehran Polytechnic), Tehran 15875-4413 (Iran, Islamic Republic of); Shakeri, H.R. [Department of Materials Science and Engineering, University of Toronto, Toronto, Ontario M5S 3E4 (Canada)] [Department of Materials Science and Engineering, University of Toronto, Toronto, Ontario M5S 3E4 (Canada); Rahimipour, M.R. [Department of Ceramic, Materials and Energy Research Center, Karaj 31787-316 (Iran, Islamic Republic of)] [Department of Ceramic, Materials and Energy Research Center, Karaj 31787-316 (Iran, Islamic Republic of)

2013-01-15

299

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

300

Growth of SiO 2 on InP substrate by liquid phase deposition  

NASA Astrophysics Data System (ADS)

We have grown silicon dioxide (SiO 2) on indium phosphorous (InP) substrate by liquid phase deposition (LPD) method. With inserting InP wafer in the treatment solution composed of SiO 2 saturated hydrofluorosilicic acid (H 2SiF 6), 0.1 M boric acid (H 3BO 3) and 1.74 M diluted hydrochloric acid (HCl), the maximum deposition rate and refractive index for the as-grown LPD-SiO 2 film were about 187.5 Å/h and 1.495 under the constant growth temperature of 40 °C. The secondary ion mass spectroscope (SIMS) and energy dispersive X-ray (EDX) confirmed that the elements of silicon, oxygen, and chloride were found in the as-grown LPD-SiO 2 film. On the other hand, the effects of treatment solution incorporated with the hydrogen peroxide (H 2O 2) that can regulate the concentration of OH - ion were also shown in this article. The experimental results represented that the deposition rate decreases with increasing the concentration of hydrogen peroxide due to the reduced concentration of SiO 2 saturated H 2SiF 6 in treatment solution.

Lei, Po Hsun; Yang, Chyi Da

2010-04-01

301

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

302

Application of liquid-phase microextraction to the analysis of trihalomethanes in water.  

PubMed

A liquid-phase microextraction method for the determination of trihalomethanes (THMs) including chloroform (CHCl3), bromodichloromethane (CHBrCl2), dibromochloromethane (CHBr2Cl) and bromoform (CHBr3) in water samples was developed, with analysis by gas chromatography-electron capture detection (GC-ECD). After the determination of the most suitable solvent and stirring rate for the extraction, several other parameters (solvent drop volume, extraction time and ionic strength of the sample) were optimized using a factorial design to obtain the most relevant variables. The optimized extraction conditions for 5 mL of sample volume in a 10 mL vial were as follows: n-hexane an organic solvent; a solvent drop volume of 2 microL; an extraction time of 5.0 min; a stirring rate of 600 rpm at 25 degrees C; sample ionic strength of 3M sodium chloride. The linear range was 1-75 microg L(-1) for the studied THMs. The limits of detection (LODs) ranged from 0.23 microg L(-1) (for CHBr2Cl) to 0.45 microg L(-1) (for CHCl3). Recoveries of THMs from fortified distilled water were over 70% for a fortification level of 15 microg L(-1), and relative standard deviations of the recoveries were below 5%. Real samples collected from tap water and well water were successfully analyzed using the proposed method. The recovery of spiked water samples was from 73% to 78% with relative standard deviations below 7%. PMID:17723583

Tor, Ali; Aydin, M Emin

2006-08-01

303

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

304

Liquid-Phase Epitaxial Growth of Two-Dimensional Semiconductor Hetero-nanostructures.  

PubMed

Although many two-dimensional (2D) hybrid nanostructures are being prepared, the engineering of epitaxial 2D semiconductor hetero-nanostructures in the liquid phase still remains a challenge. The preparation of 2D semiconductor hetero-nanostructures by epitaxial growth of metal sulfide nanocrystals, including CuS, ZnS and Ni3 S2 , is achieved on ultrathin TiS2 nanosheets by a simple electrochemical approach by using the TiS2 crystal and metal foils. Ultrathin CuS nanoplates that are 50-120?nm in size and have a triangular/hexagonal shape are epitaxially grown on TiS2 nanosheets with perfect epitaxial alignment. ZnS and Ni3 S2 nanoplates can be also epitaxially grown on TiS2 nanosheets. As a proof-of-concept application, the obtained 2D CuS-TiS2 composite is used as the anode in a lithium ion battery, which exhibits a high capacity and excellent cycling stability. PMID:25530025

Tan, Chaoliang; Zeng, Zhiyuan; Huang, Xiao; Rui, Xianhong; Wu, Xue-Jun; Li, Bing; Luo, Zhimin; Chen, Junze; Chen, Bo; Yan, Qingyu; Zhang, Hua

2015-02-01

305

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

2012-03-16

306

Biodegradation of polycyclic aromatic hydrocarbons in a two-liquid-phase system  

SciTech Connect

The use of a two-liquid-phase system consisting of silicone oil and water for biodegrading polycyclic aromatic hydrocarbons (PAHs) was investigated. Biomass determinations indicated that the cells were mainly growing at the silicon oil-water interface. In shaken and aerated systems with PAHs and inoculum, 97% and 80%, respectively, of the total biomass was attached to the silicone phase. PAH concentrations in the silicon phase dropped by a factor 2 to 100 when microorganisms were present. Biodegradation rates in these systems varied from 3.6 to 5 mg PAH-C/L reactor{center_dot}d. In the shaken systems at 28 C, the measured CO{sub 2} production rate was equal to 9.1 mg CO{sub 2}/L reactor{center_dot}d and corresponded to a 50% conversion to CO{sub 2}. In the aerated systems at 10 C, however, only 25% of the PAH-C was converted to CO{sub 2}, resulting in a CO{sub 2} production rate of 0.5 mg CO{sub 2}/L reactor{center_dot}d.

Vanneck, P.; Beeckman, M.; Saeyer, N. De; Verstraete, W. [Univ. of Ghent (Belgium). Centre for Environmental Sanitation; D`Haene, S. [Soils N.V., Zwijndrecht (Belgium)

1995-12-31

307

Investigating the solid-liquid phase transition of water nanofilms using the generalized replica exchange method  

NASA Astrophysics Data System (ADS)

The generalized Replica Exchange Method (gREM) was applied to study a solid-liquid phase transition in a nanoconfined bilayer water system using the monatomic water (mW) model. Exploiting optimally designed non-Boltzmann sampling weights with replica exchanges, gREM enables an effective sampling of configurations that are metastable or unstable in the canonical ensemble via successive unimodal energy distributions across phase transition regions, often characterized by S-loop or backbending in the statistical temperature. Extensive gREM simulations combined with Statistical Temperature Weighted Histogram Analysis Method (ST-WHAM) for nanoconfined mW water at various densities provide a comprehensive characterization of diverse thermodynamic and structural properties intrinsic to phase transitions. Graph representation of minimized structures of bilayer water systems determined by the basin-hopping global optimization revealed heterogeneous ice structures composed of pentagons, hexagons, and heptagons, consistent with an increasingly ordered solid phase with decreasing density. Apparent crossover from a first-order solid-liquid transition to a continuous one in nanoconfined mW water with increasing density of the system was observed in terms of a diminishing S-loop in the statistical temperature, smooth variation of internal energies and heat capacities, and a characteristic variation of lateral radial distribution functions, and transverse density profiles across transition regions.

Lu, Qing; Kim, Jaegil; Farrell, James D.; Wales, David J.; Straub, John E.

2014-11-01

308

Gas-Purged Headspace Liquid Phase Microextraction System for Determination of Volatile and Semivolatile Analytes  

PubMed Central

In order to achieve rapid, automatic, and efficient extraction for trace chemicals from samples, a system of gas-purged headspace liquid phase microextraction (GP-HS-LPME) has been researched and developed based on the original HS-LPME technique. In this system, semiconductor condenser and heater, whose refrigerating and heating temperatures were controlled by microcontroller, were designed to cool the extraction solvent and to heat the sample, respectively. Besides, inert gas, whose gas flow rate was adjusted by mass flow controller, was continuously introduced into and discharged from the system. Under optimized parameters, extraction experiments were performed, respectively, using GP-HS-LPME system and original HS-LPME technique for enriching volatile and semivolatile target compounds from the same kind of sample of 15 PAHs standard mixture. GC-MS analysis results for the two experiments indicated that a higher enrichment factor was obtained from GP-HS-LPME. The enrichment results demonstrate that GP-HS-LPME system is potential in determination of volatile and semivolatile analytes from various kinds of samples. PMID:22448341

Zhang, Meihua; Bi, Jinhu; Yang, Cui; Li, Donghao; Piao, Xiangfan

2012-01-01

309

Liquid-liquid phase transition in quasi-two-dimensional supercooled silicon.  

PubMed

Anomalies of the local structural order in quasi-two-dimensional liquid silicon upon cooling are investigated. Results show that the appearance of the left subpeak in pair correlation functions is the signature of the liquid-liquid phase transition (LLPT). The structural origin of the LLPT is the formation of a crystal-like ordered structure with a short-range scale, which in turn forms the local well-organized paracrystalline region. Unlike in the bulk liquid silicon, the stages of the LLPT and liquid-solid phase transition (LSPT) in the quasi-two-dimensional liquid silicon do not overlap. The crystal-like ordered structures formed in the LLPT are precursors which are prepared for the subsequent LSPT. Also observed was a strong interconnection between the local well-organized paracrystalline region and the transition from the typical metal to the semimetal in the two-dimensional silicon. This study will aid in better understanding of the essential phase change in two-dimensional liquid silicon. PMID:25050842

Zhang, K; Li, H; Jiang, Y Y

2014-09-01

310

Local liquid phase deposition of silicon dioxide on hexagonally close-packed silica beads.  

PubMed

Liquid phase deposition (LPD) is a useful method for the production of oxide film with low reaction temperature and production cost. With the report that the LPD of oxide films is conformally processed with uniform thickness and composition, there has been significant attention given to investigating its kinetic controls and growth mechanism on the flat surface. In this work, we explored the LPD of silicon dioxide on the hexagonally close-packed silica beads array as a nanostructured surface. The deposition and etching reactions of SiO2 occurred locally and simultaneously on silica beads, and were distinguished from the amount of fumed silica added in LPD solution. From locally competitive reactions, we obtained the anisotropic morphology of close-packed silica beads, and proposed a mechanism for the local LPD of SiO2 driven by nanostructured surfaces. This work contributes highly to improve metal oxide-based engineering, and also provide greater insight into the topography-driven LPD. PMID:25494033

Yoon, Seo Young; Park, Yi-Seul; Lee, Jin Seok

2015-01-13

311

Microstructural development in NiAl/Ni-Si-B/Ni transient liquid phase bonds  

SciTech Connect

A transmission electron microscopy (TEM) based investigation of microstructural development during transient liquid phase bonding of near-stoichiometric NiAl to commercial purity nickel is presented in this article. The work described employed Ni-4.5 wt pct Si-3.2 wt pct B (BNi-3) melt-spun interlayers. The precipitation of both Ni-Al based phases and borides within the joint and adjacent substrate regions is discussed. The article considers martensite formation (within the NiAl substrate) and the precipitation of L1{sub 2} type phases (both within the joint and at the interface with the NiAl substrate). The relative roles of the two substrate materials (NiAl and Ni) in the isothermal resolidification process are identified. The preferential formation of Ni{sub 3}B boride phases in the Ni substrate near the original location of the Ni substrate-joint interface is discussed and contrasted with the absence of similar events in the NiAl substrate.

Gale, W.F.; Orel, S.V. [Auburn Univ., AL (United States). Materials Research and Education Center

1996-07-01

312

Joining of NiAl to nickel-base alloys by transient liquid phase bonding  

SciTech Connect

A transmission and scanning electron microscope investigation is undertaken to study microstructural development during transient liquid phase (TLP) bonding of NiAl to Ni-base substrates. The bonds were produced through a conventional technique employing a Cu foil interlayer or a wide-gap technique using a composite preform containing powders of NiAl and Cu. The time required for completion of isothermal solidification was greatly reduced in wide-gap bonds as compared to conventional bonds. Microstructural features of conventional TLP bonds of polycrystalline-NiAl/Ni were controlled by the ratio of Al: Cu across the joint. The precipitation of the {sigma} phase encountered in polycrystalline-NiAl/Martin Marietta 247 superalloy (MM247) bonds was suppressed in wide-gap bonds of single crystal-NiAl(Hf) and MM247. In general, the extent of second phase precipitation, in the as-bonded condition, was greatly reduced by the use of the wide-gap technique. However, extensive precipitation of HfC and W-rich phases was observed after post-bond heat treatments.

Abdo, Z.A.M.; Guan, Y.; Gale, W.F.

1999-07-01

313

Kinetic model for scanning laser-induced deposition from the liquid phase  

NASA Astrophysics Data System (ADS)

The effect of precursor concentration (0.005-0.05M) and scanning speed (0.20-0.96 mm/s) on the volume of the deposited material, determined with a circumstantial procedure using the cross-sectional data measured by a DEKTAK profilometer, in pyrolytic laser writing from aqueous solutions of ammonium heptamolybdate has been studied. From the detailed investigation we have given evidences that the structures of the deposits and their concentration and scanning speed dependencies can be consequently interpreted on the basis of material supply speeds, i.e. short illumination times, minutes deposition rates are observed indicating that material transport takes place via short-range diffusion. On decreasing the writing speed, i.e. increasing the dwell time, the slope of the volume versus dwell time function is higher because of forced (convectional) material supply due to local stirring in the liquid phase in close proximity to the heated surface area. With a further increase of the dwell time a saturation effect was also observed due to material depletion from the vortex affected liquid volume which can only be eliminated by less effective long-range diffusion. The main result of this work is a semi-quantitative description of the kinetics of the deposition process which gives an explanation for the large variety of morphologies and changes in deposition rates in terms of material transport.

Geretovszky, Zs.; Kelemen, L.; Bali, K.; Szörényi, T.

1995-02-01

314

Measurements of activity coefficients at infinite dilution of aliphatic and aromatic hydrocarbons, alcohols, thiophene, tetrahydrofuran, MTBE, and water in ionic liquid [BMIM][SCN] using GLC  

Microsoft Academic Search

The activity coefficients at infinite dilution, ?13? for 32 solutes: alkanes, alken-1-es, alkyn-1-es, cycloalkanes, aromatic hydrocarbons, alcohols, thiophene, tetrahydrofuran, tert-butyl methyl ether, and water in the ionic liquid 1-butyl-3-methylimidazolium thiocyanate [BMIM][SCN] were determined by gas-liquid chromatography at the temperatures from 298.15K to 368.15K. The values of the partial molar excess enthalpies at infinite dilution ?H1E,? were calculated from the experimental

Urszula Doma?ska; Marta Laskowska

2009-01-01

315

Activity coefficients and thermodynamic parameters for RbCl/CsCl + amide (acetamide, propanamide, and n-butanamide) + water system at 298.15 K.  

PubMed

Electromotive force (emf) of the chemical cell without liquid-junction K-ISE | RbCl/CsCl ( m(E)) | ISE-Cl and K-ISE | RbCl/CsCl (m(E)), amide (m(N)) | ISE-Cl, have been measured at 298.15 K, where m(E)=(0.005 to 0.5) mol kg(-1) and m(N)= (0.05 to 3.0) mol kg(-1). The activity coefficients of RbCl/CsCl in amide (acetamide, propanamide, and n-butanamide) + water mixture can be obtained from these electromotive force data and in the mean time the Gibbs free energy interaction parameters of RbCl/CsCl + amide pair in water, g(EN), as well as the salt constant, k(S), can be evaluated. The results show that both g(EN)>0, k(S)>0 at 298.15 K, and all the activity coefficients of electrolyte in amide + water mixture increase with increasing the m(N), but it is a little complicated for the dependence of activity coefficients on m(E). These thermodynamic parameters were discussed in terms of a model of the structural interaction and electrostatic interaction and the dependence of them on the number of carbon atoms in amide as well as the radius of metal ions were interpreted by the group additivity principle. PMID:16039039

Jiang, Yucheng; Hu, Mancheng; Fan, Peng; Wang, Jianji; Zhuo, Kelei

2005-10-22

316

Quantification of tetramethyl-terephthalic acid in rat liver, spleen and urine matrices by liquid-liquid phase extraction and HPLC-photodiode array detection.  

PubMed

Tetramethyl-terephthalate (TMT) is the constitutive linker of the flexible porous iron(III) carboxylate Metal Organic Framework (MOF) MIL-88B_4CH? based drug nanocarrier (MIL stands for Material from Institut Lavoisier). A method for the determination of the concentration of tetramethyl-terephthalic acid has been developed in different biological rat matrices (liver, spleen and urine) using a liquid-liquid phase extraction and high-performance liquid chromatography (HPLC) coupled to photodiode array detection with 4-aminosalicylic acid as internal standard. The extraction conditions of TMT have been varied from urine to tissue depending on the complexity of the biological matrices. The chromatographic separation was performed with a gradient elution. In all matrices, the limits of detection and quantification of TMT was 0.01 and 0.05 ?g ml?¹, respectively. The recovery of the TMT reached 86, 89 and 97% for urine, spleen and liver tissues, respectively. The linearity of the calibration curves in urine and tissues was satisfactory in all cases as evidenced by correlation coefficients >0.990. The within-day and between-day precisions were <15% (n=6) and the accuracy ranged in all cases between 86 and 103%. This method has finally allowed the quantification of TMT in rat urine and in tissue samples of rats administered intravenously with iron(III) tetramethyltherepthalate MIL-88B_4CH? nanoparticles. PMID:22608098

Baati, Tarek; Horcajada, Patricia; David, Olivier; Gref, Ruxandra; Couvreur, Patrick; Serre, Christian

2012-01-01

317

Determination of lewisite constituents in aqueous samples using hollow-fibre liquid-phase microextraction followed by gas chromatography-mass spectrometry.  

PubMed

The applicability of hollow-fibre liquid-phase microextraction for extracting 2-chlorovinyldichloroarsine (lewisite 1), bis(2-chlorovinyl)chloroarsine (lewisite 2), tris(2-chlorovinyl)arsine (lewisite 3) and arsenic trichloride from aqueous samples is reported. Parameters affecting the extraction efficiency of these chemicals were optimised. These parameters included the type of derivatising agent, extraction solvent, derivatisation method, pH, ionic strength, stirring speed and extraction time. A linear range between 0.002 and 0.2 ?g/mL was established for the lewisites with good square regression coefficients (0.9955-0.9992). Good reproducibility with relative standard deviations (RSDs) from 8 to 10% was achieved. The limit of detection was 0.002 ?g/mL for the lewisites and 0.005 ?g/mL for arsenic trichloride (3:1 signal-to-noise ratio). The extraction method was validated with a proficiency test sample issued by the Organisation for the Prohibition of Chemical Weapons (OPCW). The rapidity and precision of the new method should help deter against the employment of lewisite as a chemical warfare agent: its use could be confirmed easily from analysis of aqueous samples. PMID:24633588

Cheh, M Y; Chua, H C; Hopkins, F B; Riches, J R; Timperley, C M; Lee, H S Nancy

2014-08-01

318

Investigation of bioaccumulation profile of oestrogens in zebrafish liver by hollow fibre protected liquid phase microextraction with gas chromatography-mass spectrometric detection.  

PubMed

The applicability of hollow fibre protected liquid phase microextraction (HF-LPME) for the determination of three oestrogens, namely estrone (E1), 17?-estradiol (E2) and 17?-ethinylestradiol (EE2) from individual zebrafish liver samples, in a bioaccumulation study on these organisms, is reported. The oestrogens were extracted from single, mechanically crushed and minced livers from fish that were heaved in tubes containing water spiked at low concentration of the analytes. Extraction was performed with ?3 ?L of toluene contained in the hollow fibre. In order to achieve high extraction efficiency, the parameters that could affect the effectiveness of HF-LPME were optimized, i.e. the extracting organic solvent, extraction time, stirring speed and pH of the aqueous phase. For gas chromatography/mass spectrometry (GC/MS) analysis, injection port derivatization of the oestrogens with bis(trimethylsilyl)trifluoroacetamide was conducted. Under the most favourable extraction and derivatization conditions, enrichment factors of 158-279 were obtained. Linearity of the HF-LPME-GC/MS method was evaluated from 1 to 50 ?g/L and the coefficient of determination (r²) ranged from 0.9687 to 0.9926. The LODs were between 0.017 and 0.033 ?g/L (at a signal to noise ratio of 3) with relative standard deviations (RSDs, analytes spiked at 5 ?g/L) of between 15 and 17% (n=3). PMID:23153642

Kanimozhi, Sivarajan; Basheer, Chanbasha; Neveliappan, Shanmugam; Ang, Kelvin; Xue, Feng; Lee, Hian Kee

2012-11-15

319

Magnetic Properties of Liquid-Phase Sintered CoFe2O4 for Application in Magnetoelastic and Magnetoelectric Transducers  

PubMed Central

Cobalt ferrite is a ferrimagnetic magnetostrictive ceramic that has potential application in magnetoelastic and magnetoelectric transducers. In this work, CoFe2O4 was obtained using a conventional ceramic method and Bi2O3 was used as additive in order to obtain liquid-phase sintered samples. Bi2O3 was added to the ferrite in amounts ranging from 0.25 mol% to 0.45 mol% and samples were sintered at 900 °C and 950 °C. It was observed the presence of Bi-containing particles in the microstructure of the sintered samples and the magnetostriction results indicated microstructural anisotropy. It was verified that it is possible to get dense cobalt ferrites, liquid-phase sintered, with relative densities higher than 90% and with magnetostriction values very close to samples sintered without additives. PMID:23112589

de Brito, Vera Lúcia Othéro; Cunha, Stéphanie Alá; Lemos, Leonardo Violim; Nunes, Cristina Bormio

2012-01-01

320

Fabrication of Nanostructured Medical-Grade Stainless Steel by Mechanical Alloying and Subsequent Liquid-Phase Sintering  

NASA Astrophysics Data System (ADS)

This article focuses on the microstructure of medical-grade P558 (ASTM F2581) stainless steel produced by mechanical alloying and liquid-phase sintering. Rietveld X-ray diffraction and transmission electron microscopy reflect that the mechanically alloyed stainless steel powder is a nanocrystal dispersed amorphous matrix composite. Mn-11.5 wt pct Si eutectic alloy as additive improves densification of the synthesized P558 alloy via liquid-phase sintering mechanism. X-ray mapping shows that after sintering at 1323 K (1050 °C) for 1 hour, a uniform distribution of dissolved Mn and Si is achieved. Moreover, the development of a nanostructured, fully austenitic stainless steel after sintering at the same temperature is realized by X-ray diffraction and transmission electron microscopy.

Salahinejad, Erfan; Hadianfard, Mohammad J.; Ghaffari, Mohammad; Mashhadi, Shirazeh Bagheri; Okyay, Ali K.

2012-08-01

321

Magnetic properties of liquid-phase sintered CoFe?O? for application in magnetoelastic and magnetoelectric transducers.  

PubMed

Cobalt ferrite is a ferrimagnetic magnetostrictive ceramic that has potential application in magnetoelastic and magnetoelectric transducers. In this work, CoFe(2)O(4) was obtained using a conventional ceramic method and Bi(2)O(3) was used as additive in order to obtain liquid-phase sintered samples. Bi(2)O(3) was added to the ferrite in amounts ranging from 0.25 mol% to 0.45 mol% and samples were sintered at 900 °C and 950 °C. It was observed the presence of Bi-containing particles in the microstructure of the sintered samples and the magnetostriction results indicated microstructural anisotropy. It was verified that it is possible to get dense cobalt ferrites, liquid-phase sintered, with relative densities higher than 90% and with magnetostriction values very close to samples sintered without additives. PMID:23112589

de Brito, Vera Lúcia Othéro; Cunha, Stéphanie Alá; Lemos, Leonardo Violim; Nunes, Cristina Bormio

2012-01-01

322

Elastic constants and ultrasound attenuation in the spin-liquid phase of Cs2CuCl4  

NASA Astrophysics Data System (ADS)

The spin excitations in the spin-liquid phase of the anisotropic triangular lattice quantum antiferromagnet Cs2CuCl4 have been shown to propagate dominantly along the crystallographic b axis. To test this dimensional reduction scenario, we have performed ultrasound experiments in the spin-liquid phase of Cs2CuCl4 probing the elastic constant c22 and the sound attenuation along the b axis as a function of an external magnetic field along the a axis. We show that our data can be quantitatively explained within the framework of a nearest-neighbor spin-1 /2 Heisenberg chain, where fermions are introduced via the Jordan-Wigner transformation and the spin-phonon interaction arises from the usual exchange-striction mechanism.

Streib, S.; Kopietz, P.; Cong, P. T.; Wolf, B.; Lang, M.; van Well, N.; Ritter, F.; Assmus, W.

2015-01-01

323

Separation of glycyrrhizic acid and liquiritin from Glycyrrhiza uralensis Fisch extract by three-liquid-phase extraction systems  

Microsoft Academic Search

Some stable three-liquid-phase extraction systems have been used for isolation and separation of glycyrrhizic acid (GA) and liquiritin (LQ) in aqueous Glycyrrhizia uralensis Fisch extract. Partition behaviors of two compounds were investigated at various conditions. Organic extractants and the pH of solution were two main factors to affect their partitioning among the phases and separation strategies. Different extraction profiles showed

Shufeng Shen; Zhidong Chang; Ji Liu; Xinghua Sun; Xin Hu; Huizhou Liu

2007-01-01

324

The Effects of Composition and Microstructure on the Thermal Conductivity of Liquid-Phase-Sintered W-Cu  

Microsoft Academic Search

Liquid-phase sintering of high-purity, submicron, co-reduced W-15Cu powders at temperatures of 1463 to 1623 K (1190 to 1350 °C) produces W grain sizes ranging from 0.6 to 1.2 mum while maintaining less than 2 pct porosity. Measured thermal conductivities of 185 to 221 W\\/(m·K) are related to the grain size and contiguity, which ranged from 0.51 to 0.62. The effects

John L. Johnson; Seong Jin Park; Young-Sam Kwon; Randall M. German

2010-01-01

325

Effect of the hydrogen pressure on the kinetics of the liquid-phase catalytic hydrogenation of aromatic nitro compounds  

Microsoft Academic Search

1.The relation between the rate of liquid-phase nitro compound hydrogenation and the hydrogen pressure is complex. Over the pressure range from 0.1 to 0.9 MPa, the concentration of the initial nitro product varies in direct proportion to the hydrogen pressure, and this despite the fact that the rate of conversion of the intermediate phenylhydroxylamine into the amino product is unaffected

I. A. Makaryan; V. I. Savchenko; Kh. A. Brikenshtein

1981-01-01

326

Comparison of Methods to Obtain a Liquid Phase in Marine Sediment Toxicity Bioassays with Paracentrotus lividus Sea Urchin Embryos  

Microsoft Academic Search

Sediment toxicity bioassays using planktonic organisms are widespread tools in environmental quality assessment, but they\\u000a have limitations because the method for extracting and diluting the liquid phase may affect the final toxicity. The present\\u000a study compares the toxicity on sea urchin embryos and larvae of elutriates and pore water obtained from intertidal sediments\\u000a by various methods. The effects of mixing

R. Beiras

2002-01-01

327

Quantum wires prepared by liquid-phase-epitaxial overgrowth of dry-etched AlGaAs-GaAs heterostructures  

NASA Astrophysics Data System (ADS)

We have developed a technique to overgrow deep-mesa-etched AlGaAs-GaAs quantum wires with AlGaAs by liquid-phase epitaxy and achieve improved interfacial properties. In particular, we find a significant reduction of the surface-state density and related lateral edge depletion in modulation-doped quantum wires. We demonstrate the formation of a quasi-one-dimensional electron system by far infrared spectroscopy.

Hornischer, W.; Grambow, P.; Demel, T.; Bauser, E.; Heitmann, D.; von Klitzing, K.; Ploog, K.

1992-06-01

328

Preparation, structure and crystallinity of chitosan nano-fibers by a solid–liquid phase separation technique  

Microsoft Academic Search

Chitosan acetate nano-fibers were fabricated via a solid–liquid phase separation technique. The chitosan acetate structure was influenced by phase separation temperature, chitosan concentration and acetic acid concentration. Uniform nano-fibrous chitosan acetate of 50–500nm in diameter was engineered at 0.05% (w\\/v) chitosan and 0.025% (v\\/v) acetic acid in liquid nitrogen, as opposed to film-shape and micro-fibrous structure at ?18°C and ?80°C

Jianhao Zhao; Wanqing Han; Haodong Chen; Mei Tu; Rong Zeng; Yunfeng Shi; Zhengang Cha; Changren Zhou

2011-01-01

329

X-ray analysis of the phase composition of liquid-phase interaction products of W, Co, and Sn powders  

Microsoft Academic Search

X-ray analysis (in Cu and Mo radiation) is used to examine the phase composition of pseudoalloys for the first time. The pseudoalloys\\u000a are formed in the liquid-phase sintering of W, Co, and Sn powders in hydrogen at 1200°C. After cooling, all pseudoalloys contain\\u000a tungsten (intensive reflections) and W6Co7 (weak reflections) phases, ??-phases of Co3Sn2, and CoSn2.

V. G. Chuprina; I. M. Shalya

2008-01-01

330

Silicone-stimulated anthraquinone production and release by Morinda citrifolia in a two-liquid-phase system  

Microsoft Academic Search

A 2.5-fold increase in the release of intracellular anthraquinones was obtained by adding 1 ml L-1 silicone A to suspension cultures of Morinda citrifolia. Cell growth and secondary metabolite production were not affected even at high silicone A concentrations. Performance of the silicone treatment in a two-liquid-phase system (5 ml n-hexadecane\\/50 ml medium) resulted in a 150% increase of the

Lucilla Bassetti; Joli Pijnenburg; Johannes Tramper

1996-01-01

331

Interfacial microstructure of partial transient liquid phase bonded Si 3N 4-to-Inconel 718 joints  

Microsoft Academic Search

This work presents transmission electron microscopy (TEM) analysis of the interfacial microstructure in Si3N4-to-Inconel 718 joints with Ni interlayers produced by partial transient liquid phase bonding (PTLPB). Ti and Cu microfoils have been inserted between Si3N4 and the Ni interlayer and joining has been performed at lower temperatures than previous PTLPBs of Si3N4 with the same insert metals. The TEM

Jae Joong Kim; Jin-Woo Park; Thomas W. Eagar

2003-01-01

332

Microstructural evolution during transient liquid phase bonding of Inconel 617 using Ni–Si–B filler metal  

Microsoft Academic Search

The influence of process parameters on microstructural characteristics of transient liquid phase (TLP) bonded Inconel 617 alloy was investigated. Experiments were carried out at 1065°C using nickel based filler metal (Ni–4.5% Si–3% B) with B as the melting point depressant (MPD) element. Two different thickness of interlayer and various holding times were employed. The influence of these processing parameters on

F. Jalilian; M. Jahazi; R. A. L. Drew

2006-01-01

333

Electric transport properties of YBCO bicrystal films with 45o misorientation angle grown by liquid phase epitaxy  

Microsoft Academic Search

We report on transport properties of grain boundaries fabricated in YBa2Cu3O7-x thin films grown by the liquid phase epitaxy (LPE) technique on MgO asymmetrical bicrystal substrate with 45o misorientation angle. In total around 10 samples have been studied. Substantial scatter of zero field values of the critical current density at 5K has been observed. The upper limit of Jc of

Yu. Eltsev; Y. Yamada; K. Nakao

2009-01-01

334

Numerical Method for Computer Study of Liquid Phase Sintering: Densification Due to Gravity-Induced Skeletal Settling  

Microsoft Academic Search

\\u000a In this paper we will investigate numerically densification due to gravity-induced skeletal settling during liquid phase sintering.\\u000a For domain definition we will use small identical cubic elements, voxels, of finite size. Solid skeleton formation will be introduced by defining skeleton units and by their time evolution and formation\\u000a of large solid skeleton arranged in a long chain of connected solid-phase

Zoran S. Nikoli?

335

Liquid-phase processing of fast pyrolysis bio-oil using platinum/HZSM-5 catalyst  

NASA Astrophysics Data System (ADS)

Recent developments in converting biomass to bio-chemicals and liquid fuels provide a promising sight to an emerging biofuels industry. Biomass can be converted to energy via thermochemical and biochemical pathways. Thermal degradation processes include liquefaction, gasification, and pyrolysis. Among these biomass technologies, pyrolysis (i.e. a thermochemical conversion process of any organic material in the absence of oxygen) has gained more attention because of its simplicity in design, construction and operation. This research study focuses on comparative assessment of two types of pyrolysis processes and catalytic upgrading of bio-oil for production of transportation fuel intermediates. Slow and fast pyrolysis processes were compared for their respective product yields and properties. Slow pyrolysis bio-oil displayed fossil fuel-like properties, although low yields limit the process making it uneconomically feasible. Fast pyrolysis, on the other hand, show high yields but produces relatively less quality bio-oil. Catalytic transformation of the high-boiling fraction (HBF) of the crude bio-oil from fast pyrolysis was therefore evaluated by performing liquid-phase reactions at moderate temperatures using Pt/HZSM-5 catalyst. High yields of upgraded bio-oils along with improved heating values and reduced oxygen contents were obtained at a reaction temperature of 200°C and ethanol/HBF ratio of 3:1. Better quality, however, was observed at 240 °C even though reaction temperature has no significant effect on coke deposition. The addition of ethanol in the feed has greatly attenuated coke deposition in the catalyst. Major reactions observed are esterification, catalytic cracking, and reforming. Overall mass and energy balances in the conversion of energy sorghum biomass to produce a liquid fuel intermediate obtained sixteen percent (16 wt.%) of the biomass ending up as liquid fuel intermediate, while containing 26% of its initial energy.

Santos, Bjorn Sanchez

336

Microstructural study of transient liquid phase bonded DD98 and K465 superalloys at high temperature  

SciTech Connect

Microstructure of a transient liquid phase (TLP) bonded joint between single crystal DD98 and polycrystalline K465 superalloys was investigated by scanning electron microscopy, transmission electron microscopy and X-ray diffraction techniques. After bonding at 1190 deg. C for 2 h, many phases formed in the centerline of the bonding zone due to an incompletely solidified liquid interlayer. There are script-like, tree-like and blocky compounds besides solid solution {gamma} phase in this region. The script-like phase is CrB boride that is rich in Cr, the tree-like compound rich in Ni is M{sub 23}B{sub 6} with FCC structure, and the blocky phase enriched in Ti, Ta, and Nb, is MC carbide that resulted from the interdiffusion of C atoms between dissimilar base metals. After TLP bonding, many blocky and fine M{sub 6}C particles rich in Cr and W appeared in the diffusion zone of the K465 side. A number of blocky and platelet M{sub 3}B{sub 2} borides rich in W, Cr and Mo precipitated in the diffusion zone of the DD98 side. - Research Highlights: {yields} DD98 and K465 alloy was TLP bonded. {yields} The microstructure changes of different parts were studied. {yields} CrB, M{sub 23}B{sub 6} and MC formed in the bonding zone. {yields} M{sub 6}C appeared in diffusion zone of K465 side and M{sub 3}B{sub 2} existed in diffusion zone of DD98 side.

Liu Jide, E-mail: jdliu@imr.ac.cn; Jin Tao; Zhao Nairen; Wang Zhihui; Sun Xiaofeng; Guan Hengrong; Hu Zhuangqi

2011-05-15

337

Liquid-liquid phase transitions for soft-core attractive potentials.  

PubMed

Using event-driven molecular dynamics simulations, we study a three-dimensional one-component system of spherical particles interacting via a discontinuous potential combining a repulsive square soft core and an attractive square well. In the case of a narrow attractive well, it has been shown that this potential has two metastable gas-liquid critical points. Here we systematically investigate how the changes of the parameters of this potential affect the phase diagram of the system. We find a broad range of potential parameters for which the system has both a gas-liquid critical point C1 and a liquid-liquid critical point C2. For the liquid-gas critical point we find that the derivatives of the critical temperature and pressure, with respect to the parameters of the potential, have the same signs: they are positive for increasing width of the attractive well and negative for increasing width and repulsive energy of the soft core. This result resembles the behavior of the liquid-gas critical point for standard liquids. In contrast, for the liquid-liquid critical point the critical pressure decreases as the critical temperature increases. As a consequence, the liquid-liquid critical point exists at positive pressures only in a finite range of parameters. We present a modified van der Waals equation which qualitatively reproduces the behavior of both critical points within some range of parameters, and gives us insight on the mechanisms ruling the dependence of the two critical points on the potential's parameters. The soft-core potential studied here resembles model potentials used for colloids, proteins, and potentials that have been related to liquid metals, raising an interesting possibility that a liquid-liquid phase transition may be present in some systems where it has not yet been observed. PMID:15244553

Skibinsky, A; Buldyrev, S V; Franzese, G; Malescio, G; Stanley, H E

2004-06-01

338

Determination of bile acids by hollow fibre liquid-phase microextraction coupled with gas chromatography.  

PubMed

A method based on hollow-fibre liquid phase microextraction combined with gas chromatography was developed for determination of specific bile acids in caecal materials of rats. Nine unconjugated bile acids, including the primary bile acids (cholic acid, chenodeoxycholic acid and ?-muricholic acid) and the secondary bile acids (lithocholic acid, deoxycholic acid, ursodeoxycholic acid, hyodeoxycholic acid, ?-muricholic acid and ?-muricholic acid) were quantified. Extraction conditions were evaluated, including: sample pH, type of organic solvent and amount of caecal material to be extracted. To compensate for sample matrix effects during extraction the method of standard addition was applied. The satisfactory linearity (r(2)>0.9840), high recovery (84.2-108.7%) and good intra-assay (6.3-10.6%) and inter-assay (6.9-11.1%) precision illustrated the good performance of the present method. The method is rapid, simple and capable of detecting and determining bile acids with limit of detection (LOD) ranged from 0.002 to 0.067?g/mL and limits of quantification (LOQ) varied from 0.006 to 0.224?g/mL. The results indicated that the concentration of some secondary bile acids, which usually are associated with health problems, were lower in rats fed with fermentable dietary fibre compared with a fibre free control diet, while the concentration of primary bile acids, usually connected with positive health effects, were higher in rats fed with diets containing dietary fibre. Of the dietary fibres, guar gum and to some extent the mixture of pectin+guar gum had the most positive effects. Thus, it was concluded that the composition of bile acids can be affected by the type of diet. PMID:24295906

Ghaffarzadegan, T; Nyman, M; Jönsson, J Å; Sandahl, M

2014-01-01

339

A Monte Carlo study of absorbed dose distributions in both the vapor and liquid phases of water by intermediate energy electrons based on different condensed-history transport schemes  

NASA Astrophysics Data System (ADS)

Monte Carlo transport calculations of dose point kernels (DPKs) and depth dose profiles (DDPs) in both the vapor and liquid phases of water are presented for electrons with initial energy between 10 keV and 1 MeV. The results are obtained by the MC4 code using three different implementations of the condensed-history technique for inelastic collisions, namely the continuous slowing down approximation, the mixed-simulation with ?-ray transport and the addition of straggling distributions for soft collisions derived from accurate relativistic Born cross sections. In all schemes, elastic collisions are simulated individually based on single-scattering cross sections. Electron transport below 10 keV is performed in an event-by-event mode. Differences on inelastic interactions between the vapor and liquid phase are treated explicitly using our recently developed dielectric response function which is supplemented by relativistic corrections and the transverse contribution. On the whole, the interaction coefficients used agree to better than ~5% with NIST/ICRU values. It is shown that condensed phase effects in both DPKs and DDPs practically vanish above 100 keV. The effect of ?-rays, although decreases with energy, is sizeable leading to more diffused distributions, especially for DPKs. The addition of straggling for soft collisions is practically inconsequential above a few hundred keV. An extensive benchmarking with other condensed-history codes is provided.

Bousis, C.; Emfietzoglou, D.; Hadjidoukas, P.; Nikjoo, H.

2008-07-01

340

Influence of gangue existing states in iron ores on the formation and flow of liquid phase during sintering  

NASA Astrophysics Data System (ADS)

Gangue existing states largely affect the high-temperature characteristics of iron ores. Using a micro-sintering method and scanning electron microscopy, the effects of gangue content, gangue type, and gangue size on the assimilation characteristics and fluidity of liquid phase of five different iron ores were analyzed in this study. Next, the mechanism based on the reaction between gangues and sintering materials was unraveled. The results show that, as the SiO2 levels increase in the iron ores, the lowest assimilation temperature (LAT) decreases, whereas the index of fluidity of liquid phase (IFL) increases. Below 1.5wt%, Al2O3 benefits the assimilation reaction, but higher concentrations proved detrimental. Larger quartz particles increase the SiO2 levels at the local reaction interface between the iron ore and CaO, thereby reducing the LAT. Quartz-gibbsite is more conductive to assimilation than kaolin. Quartz-gibbsite and kaolin gangues encourage the formation of liquid-phase low-Al2O3-SFCA with high IFL and high-Al2O3-SFCA with low IFL, respectively.

Zhang, Guo-liang; Wu, Sheng-li; Chen, Shao-guo; Su, Bo; Que, Zhi-gang; Hou, Chao-gang

2014-10-01

341

Detection of intermediates for the Eschweiler-Clarke reaction by liquid-phase reactive desorption electrospray ionization mass spectrometry.  

PubMed

Desorption electrospray ionization mass spectrometry (DESI-MS) has been developed dramatically as a powerful tool for the rapid analysis of samples in their native environment. Here a novel application of DESI-MS was demonstrated for direct probing of the reactive intermediates in the liquid-phase Eschweiler-Clarke reaction, a reductive amination reaction whereby a primary (or secondary) amine is successively N-methylated using excess formaldehyde and formic acid. The intermediates ion species of sodiated amino alcohol ([I + Na](+)) and iminium ([II](+)), along with the corresponding protonated molecules of amine reactant ([M + H](+)) and end product ([III + H](+)), were simultaneously and unambiguously characterized by the positive ion DESI-MS in the native liquid-phase reactive condition. The operating variables were optimized for better analytical performance including the spray solvent composition (such as formic acid concentration, proportion of methanol-water), voltage applied, spray spatial distance and incident angle. The feasibility of the reactive DESI-MS detection of acid-formaldehyde methylations was further validated using amines of a large variety of chemical types (2 primary and 3 secondary amines). Thus, the liquid-phase reactive DESI-MS technique allows the direct analysis of reaction intermediates occurring in complex liquid solutions without sample preparation to provide a valuable insight into chemical reaction mechanisms. PMID:21491029

Xu, Guangming; Chen, Bo; Guo, Bin; He, Dongxiu; Yao, Shouzhuo

2011-06-01

342

On inferring liquid-liquid phase boundaries and tie lines from ternary mixture light scattering  

NASA Astrophysics Data System (ADS)

We investigate the possibility of using light scattering data in the single-phase regions of a ternary liquid mixture phase diagram to infer ternary mixture coexistence curves, and to infer tie lines joining the compositions of isotropic liquid phases in thermodynamic equilibrium. Previous analyses of a nonlinear light scattering partial differential equation (LSPDE) show that it provides for reconstruction of ternary [D. Ross, G. Thurston, and C. Lutzer, J. Chem. Phys. 129, 064106 (2008), 10.1063/1.2937902; C. Wahle, D. Ross, and G. Thurston, J. Chem. Phys. 137, 034201 (2012), 10.1063/1.4731694] and quaternary [C. Wahle, D. Ross, and G. Thurston, J. Chem. Phys. 137, 034202 (2012)] mixing free energies from light scattering data, and that if the coexistence curves are already known, it can also yield ternary tie lines and triangles [D. Ross, G. Thurston, and C. Lutzer, J. Chem. Phys. 129, 064106 (2008), 10.1063/1.2937902]. Here, we show that the LSPDE can be used more generally, to infer phase boundaries and tie lines from light scattering data in the single-phase region, without prior knowledge of the coexistence curve, if the single-phase region is connected. The method extends the fact that the reciprocal light scattering intensity approaches zero at the thermodynamic spinodal. Expressing the free energy as the sum of ideal and excess parts leads to a natural family of Padé approximants for the reciprocal Rayleigh ratio. To test the method, we evaluate the single-phase reciprocal Rayleigh ratio resulting from the mean-field, regular solution model on a fine grid. We then use a low-order approximant to extrapolate the reciprocal Rayleigh ratio into metastable and unstable regions. In the metastable zone, the extrapolation estimates light scattering prior to nucleation and growth of a new phase. In the unstable zone, the extrapolation produces a negative function that in the present context is a computational convenience. The original and extrapolated reciprocal light scattering are jointly used as input to solving the LSPDE to deduce the mixing free energy and its convex hull. When projected onto the composition triangle, the boundary of the convexified part of the free energy is the phase boundary, and lines on the convexified region along which the second directional derivative is zero are the tie lines. We find that the tie lines and phase boundaries so deduced agree well with their exact values. This work is a step toward developing methods for inferring phase boundaries from real light scattering intensities measured with noise, from mixtures having compositions on a coarser grid.

Wahle, Chris W.; Ross, David S.; Thurston, George M.

2012-07-01

343

Scale-down studies on the hydrodynamics of two-liquid phase biocatalytic reactors.  

PubMed

The maintenance of constant interfacial area per unit volume is a key parameter for the successful scale-up of two-liquid phase bioconversion processes. To date, however, there is little published information on the hydrodynamics of such systems and a suitable basis for scale-up has yet to be defined and verified. Here we report power input and hydrodynamic data for a whole-cell bioconversion process using resting cells of Rhodococcus R312 to catalyse the hydration of a poorly water-soluble substrate 1,3-dicyanobenzene (1,3-DCB). Experiments were performed in geometrically similar 3-L and 75-L reactors, each fitted with a three-stage Rushton turbine impeller system. The two-phase system used comprised of 20% v/v toluene dispersed in 0.1 M aqueous phosphate buffer containing up to 10 g(ww) x L(-1) of resuspended biocatalyst and 20 g x L(-1) 1,3-DCB. The power input to the 3-L reactor was first determined using an air-bearing technique for both single-phase and two-phase mixing. In both cases, the power number attained a constant value of 11 at Re>10,000, while the measured power inputs were in the range 0.15-3.25 kW x m(-3). Drop size distributions and Sauter mean drop diameters (d(32)) were subsequently measured on-line in both reactors, using an in-situ light-backscattering technique, for scale-up on the basis of either constant power input per unit volume or constant tip speed. At both scales d(32) decreased with increasing agitation rate, while the drop size distributions obtained were log-normal. All the measured d(32) values were in the range of 30-50 microm, with the lowest values being obtained in systems with biocatalyst present. In all cases, constant power input per unit volume was found to be the most suitable basis for scale-up. This gave virtually identical d(32) values and drop size distributions at both scales. A number of correlations were also identified that would allow reasonable prediction of d(32) values for various agitation rates at each scale. While the results obtained are for a particular phase system, the scale-down methodology presented here would allow the rapid evaluation of other bioconversion processes in the 3-L reactor with a 25-fold reduction in scale. In this way, potential problems that might be encountered at the larger scale, such as the carryover of antifoam from the fermentation stage, could be quickly and efficiently identified. PMID:14508672

Cull, S G; Lovick, J W; Lye, G J; Angeli, P

2002-09-01

344

Conformational properties of asymmetrically substituted mono-, di- and trisulfides: solid and liquid phase Raman spectra  

NASA Astrophysics Data System (ADS)

The Raman spectra of diallyl trisulfide, allyl methyl sulfide, allyl methyl disulfide and allyl methyl trisulfide in the liquid and solid states are interpreted in terms of their conformational behavior. In both the liquid and solid states, the allyl moieties in all molecules are in a gauche conformation in which the sulfur atoms and the terminal vinyl carbons form a dihedral angle of between 105° and 120°. For diallyl trisulfide and allyl methyl trisulfide in both the liquid and solid states, only a near- cis S?S rotational conformer exists with a C?S?S?S dihedral angle of approximately 25°. Furthermore, the rotational isomerism of both S?S bonds of these molecules is the same. For allyl methyl disulfide in the solid and liquid phases only the gauche S?S conformer exists, with a C?S?S?C dihedral angle of approximately 70°. In the liquid state, two C?S rotational conformers occur in each of the four molecules examined. The gauche conformer corresponds to a C?C?S?C (allyl methyl sulfide) or C?C?S?S (allyl methyl disulfide, allyl methyl trisulfide and diallyl trisulfide) dihedral angle of 70°, while the trans conformer corresponds to a C?C?S?C or C?C?S?S dihedral angle of 180°. For allyl methyl sulfide in the solid state only the trans C?S conformer exists, while for allyl methyl disulfide and diallyl trisulfide only the gauche C?S conformers exist in the solid phase. For allyl methyl trisulfide in the solid state both C?S conformers exist, with the gauche C?S conformer being more stable. We suggest that the gauche C?S conformers for the di- and trisulfide systems are stabilized by attractive 1,4 C··S interactions analogous to those proposed for other sulfur containing molecules (H.E. Van Wart, L.L. Shipman and H.A. Scheraga, J. Phys. Chem., 79 (1975) 1428; ibid., 79 (1975) 1436.)

Devlin, Mark T.; Barany, George; Levin, Ira W.

1990-10-01

345

Kinetic aspects of hollow fiber liquid-phase microextraction and electromembrane extraction.  

PubMed

In this paper, extraction kinetics was investigated experimentally and theoretically in hollow fiber liquid-phase microextraction (HF-LPME) and electromembrane extraction (EME) with the basic drugs droperidol, haloperidol, nortriptyline, clomipramine, and clemastine as model analytes. In HF-LPME, the analytes were extracted by passive diffusion from an alkaline sample, through a (organic) supported liquid membrane (SLM) and into an acidic acceptor solution. In EME, the analytes were extracted by electrokinetic migration from an acidic sample, through the SLM, and into an acidic acceptor solution by application of an electrical potential across the SLM. In both HF-LPME and EME, the sample (donor solution) was found to be rapidly depleted for analyte. In HF-LPME, the mass transfer across the SLM was slow, and this was found to be the rate limiting step of HF-LPME. This finding is in contrast to earlier discussions in the literature suggesting that mass transfer across the boundary layer at the donor-SLM interface is the rate limiting step of HF-LPME. In EME, mass transfer across the SLM was much more rapid due to electrokinetic migration. Nevertheless, mass transfer across the SLM was rate limiting even in EME. Theoretical models were developed to describe the kinetics in HF-LPME, in agreement with the experimental findings. In HF-LPME, the extraction efficiency was found to be maintained even if pH in the donor solution was lowered from 10 to 7-8, which was below the pK(a)-value for several of the analytes. Similarly, in EME, the extraction efficiency was found to be maintained even if pH in the donor solution increased from 4 to 11, which was above the pK(a)-value for several of the analytes. The two latter experiments suggested that both techniques may be used to effectively extract analytes from samples in a broader pH range as compared to the pH range recommended in the literature. PMID:22884201

Gjelstad, Astrid; Jensen, Henrik; Rasmussen, Knut Einar; Pedersen-Bjergaard, Stig

2012-09-12

346

Numerical simulation and experimental study of transient liquid phase bonding of single crystal superalloys  

NASA Astrophysics Data System (ADS)

The primary goals of the research in this dissertation are to perform a systematic study to identify and understand the fundamental cause of prolonged processing time during transient liquid phase bonding of difficult-to-bond single crystal Ni-base materials, and use the acquired knowledge to develop an effective way to reduce the isothermal solidification time without sacrificing the single crystalline nature of the base materials. To achieve these objectives, a multi-scale numerical modeling approach, that involves the use of a 2-D fully implicit moving-mesh Finite Element method and a Cellular Automata method, was developed to theoretically investigate the cause of long isothermal solidification times and determine a viable way to minimize the problem. Subsequently, the predictions of the theoretical models are experimentally validated. Contrary to previous suggestions, numerical calculations and experimental verifications have shown that enhanced intergranular diffusivity has a negligible effect on solidification time in cast superalloys and that another important factor must be responsible. In addition, it was found that the concept of competition between solute diffusivity and solubility as predicted by standard analytical TLP bonding models and reported in the literature as a possible cause of long solidification times is not suitable to explain salient experimental observations. In contrast, however, this study shows that the problem of long solidification times, which anomalously increase with temperature is fundamentally caused by departure from diffusion controlled parabolic migration of the liquid-solid interface with holding time during bonding due to a significant reduction in the solute concentration gradient in the base material. Theoretical analyses showed it is possible to minimize the solidification time and prevent formation of stray-grains in joints between single crystal substrates by using a composite powder mixture of brazing alloy and base alloy as the interlayer material, which prior to the present work has been reported to be unsuitable. This was experimentally verified and the use of the composite powder mixture as interlayer material to reduce the solidification time and avoid stray-grain formation during TLP bonding of single crystal superalloys has been reported for the first time in this research.

Ghoneim, Adam

347

Active Control of Fan Noise: Feasibility Study. Volume 5; Numerical Computation of Acoustic Mode Reflection Coefficients for an Unflanged Cylindrical Duct  

NASA Technical Reports Server (NTRS)

A computational method to predict modal reflection coefficients in cylindrical ducts has been developed based on the work of Homicz, Lordi, and Rehm, which uses the Wiener-Hopf method to account for the boundary conditions at the termination of a thin cylindrical pipe. The purpose of this study is to develop a computational routine to predict the reflection coefficients of higher order acoustic modes impinging on the unflanged termination of a cylindrical duct. This effort was conducted wider Task Order 5 of the NASA Lewis LET Program, Active Noise Control of aircraft Engines: Feasibility Study, and will be used as part of the development of an integrated source noise, acoustic propagation, ANC actuator coupling, and control system algorithm simulation. The reflection coefficient prediction will be incorporated into an existing cylindrical duct modal analysis to account for the reflection of modes from the duct termination. This will provide a more accurate, rapid computation design tool for evaluating the effect of reflected waves on active noise control systems mounted in the duct, as well as providing a tool for the design of acoustic treatment in inlet ducts. As an active noise control system design tool, the method can be used preliminary to more accurate but more numerically intensive acoustic propagation models such as finite element methods. The resulting computer program has been shown to give reasonable results, some examples of which are presented. Reliable data to use for comparison is scarce, so complete checkout is difficult, and further checkout is needed over a wider range of system parameters. In future efforts the method will be adapted as a subroutine to the GEAE segmented cylindrical duct modal analysis program.

Kraft, R. E.

1996-01-01

348

A study on diffusion coefficient and diffusion activation energy of rare earth atoms in surface layer of steel rare earth nitrocarburized  

SciTech Connect

Steels, 20CrMnTi and 30CrMnSi, were nitrocarburized at 600 C and 650 C for 5h with rare earths (RE). The experimental results show that the rare earth elements can diffuse into the treated surface layer, in which the concentration profiles of the rare earth La were measured by chemical analysis and ion probe. The diffusion coefficient and activation energy of La have been calculated based on the experimental results mentioned above. The rare earth atoms diffuse mainly along the grain boundaries according to thermodynamic theory and analysis of the calculated data.

Mufu, Y.; Qun, L.; Teqiang, Z.; Yang, C.; Fayi, Z.; Zhiru, L. [Harbin Inst. of Tech. (China)

1995-12-31

349

Measurements of liquid-phase turbulence in gas-liquid two-phase flows using particle image velocimetry  

NASA Astrophysics Data System (ADS)

Liquid-phase turbulence measurements were performed in an air-water two-phase flow loop with a circular test section of 50 mm inner diameter using a particle image velocimetry (PIV) system. An optical phase separation method--planar laser-induced fluorescence (PLIF) technique—which uses fluorescent particles and an optical filtration technique, was employed to separate the signals of the fluorescent seeding particles from those due to bubbles and other noises. An image pre-processing scheme was applied to the raw PIV images to remove the noise residuals that are not removed by the PLIF technique. In addition, four-sensor conductivity probes were adopted to measure the radial distribution of the void fraction. Two benchmark tests were performed: the first was a comparison of the PIV measurement results with those of similar flow conditions using thermal anemometry from previous studies; the second quantitatively compared the superficial liquid velocities calculated from the local liquid velocity and void fraction measurements with the global liquid flow rate measurements. The differences of the superficial liquid velocity obtained from the two measurements were bounded within ±7% for single-phase flows and two-phase bubbly flows with the area-average void fraction up to 18%. Furthermore, a preliminary uncertainty analysis was conducted to investigate the accuracy of the two-phase PIV measurements. The systematic uncertainties due to the circular pipe curvature effects, bubble surface reflection effects and other potential uncertainty sources of the PIV measurements were discussed. The purpose of this work is to facilitate the development of a measurement technique (PIV-PLIF) combined with image pre-processing for the liquid-phase turbulence in gas-liquid two-phase flows of relatively high void fractions. The high-resolution data set can be used to more thoroughly understand two-phase flow behavior, develop liquid-phase turbulence models, and assess high-fidelity codes for multi-phase flows.

Zhou, Xinquan; Doup, Benjamin; Sun, Xiaodong

2013-12-01

350

The Effects of Composition and Microstructure on the Thermal Conductivity of Liquid-Phase-Sintered W-Cu  

Microsoft Academic Search

Liquid-phase sintering of high-purity, submicron, co-reduced W-15Cu powders at temperatures of 1463 to 1623 K (1190 to 1350 °C)\\u000a produces W grain sizes ranging from 0.6 to 1.2 ?m while maintaining less than 2 pct porosity. Measured thermal conductivities of 185 to 221 W\\/(m·K) are related to the grain\\u000a size and contiguity, which ranged from 0.51 to 0.62. The effects of composition and microstructure on

John L. Johnson; Seong Jin Park; Young-Sam Kwon; Randall M. German

2010-01-01

351

Liquid-phase plasma synthesis of silicon quantum dots embedded in carbon matrix for lithium battery anodes  

SciTech Connect

Graphical abstract: - Highlights: • Silicon quantum dots embedded in carbon matrix (SiQDs/C) were fabricated. • SiQDs/C exhibits excellent battery performance as anode materials with high specific capacity. • The good performance was attributed to the marriage of small sized SiQDs and carbon. - Abstract: Silicon quantum dots embedded in carbon matrix (SiQDs/C) nanocomposites were prepared by a novel liquid-phase plasma assisted synthetic process. The SiQDs/C nanocomposites were demonstrated to show high specific capacity, good cycling life and high coulmbic efficiency as anode materials for lithium-ion battery.

Wei, Ying [Institute of Functional Nano and Soft Materials (FUNSOM) and Jiangsu Key Laboratory for Carbon-Based Functional Materials and Devices, Soochow University, Suzhou (China); College of Chemistry and Chemical Engineering, Bohai University, Jinzhou 121000 (China); Yu, Hang; Li, Haitao; Ming, Hai; Pan, Keming; Huang, Hui [Institute of Functional Nano and Soft Materials (FUNSOM) and Jiangsu Key Laboratory for Carbon-Based Functional Materials and Devices, Soochow University, Suzhou (China); Liu, Yang, E-mail: yangl@suda.edu.cn [Institute of Functional Nano and Soft Materials (FUNSOM) and Jiangsu Key Laboratory for Carbon-Based Functional Materials and Devices, Soochow University, Suzhou (China); Kang, Zhenhui, E-mail: zhkang@suda.edu.cn [Institute of Functional Nano and Soft Materials (FUNSOM) and Jiangsu Key Laboratory for Carbon-Based Functional Materials and Devices, Soochow University, Suzhou (China)

2013-10-15

352

Boride Zone Formation in Transient Liquid Phase Bonding of Pairings of Parent Superalloy Materials with Different Compositions and Grain Structures  

NASA Astrophysics Data System (ADS)

Two nickel-base superalloys are joined via transient liquid phase (TLP) bonding with boron as the MPD. Boride formation is observed in the parent materials at some distance from the solid/liquid interface. The boron concentration profile over the joint is measured with glow discharge optical emission spectroscopy (GDOES). Boron concentration peaks are observed corresponding to the boride formation. Boron distribution is discussed on the basis of theoretical predictions in the literature. It is concluded that diffusion of another element is necessary to explain the results with the second element influencing the solubility of boron.

Steuer, S.; Singer, R. F.

2013-05-01

353

Catalytic and kinetic study of the liquid-phase hydrogenation of acetophenone over Cu\\/SiO 2 catalyst  

Microsoft Academic Search

The liquid-phase hydrogenation of acetophenone (AP) to 1-phenylethanol (PhE) was studied on Cu(6.8%)\\/SiO2 catalyst. Catalytic tests were carried out in a batch reactor by varying temperature, total pressure and AP initial concentration between 353–373K, 5–20bar, and 0.038–0.251M, respectively, and using four different solvents: isopropylic alcohol (IPA), cyclohexane, toluene and benzene. The selectivity to PhE was about 100% irrespective of the

Nicolás M. Bertero; Carlos R. Apesteguía; Alberto J. Marchi

2008-01-01

354

Liquid-Phase Hydrogenation of Chloronitrobenzene Over Pt-Sn-B Amorphous Catalyst Supported by Carbon Nanotubes  

Microsoft Academic Search

The Pt-Sn-B\\/carbon nanotubes (CNTs) catalyst was prepared by impregnation-chemical reduction method. Its catalytic performance\\u000a was evaluated by liquid-phase hydrogenation of chloronitrobenzene (CNB). The results showed that the catalyst had higher catalytic\\u000a performance than common hydrogenation catalysts. The conversion of CNB could reach 99.9%, and the dechlorination of chloroaniline\\u000a (CAN) was less than 1.9% when catalyzed by Pt-Sn-B\\/CNTs and more than

Xinhuan Yan; Junqing Sun; Yongbin Fang; Zhenyuan Xu; Wenjing Wang

2006-01-01

355

A liquid phase affinity capture assay using magnetic beads to study protein-protein interaction: the poliovirus-nanobody example.  

PubMed

In this article, a simple, quantitative, liquid phase affinity capture assay is presented. Provided that one protein can be tagged and another protein labeled, this method can be implemented for the investigation of protein-protein interactions. It is based on one hand on the recognition of the tagged protein by cobalt coated magnetic beads and on the other hand on the interaction between the tagged protein and a second specific protein that is labeled. First, the labeled and tagged proteins are mixed and incubated at room temperature. The magnetic beads, that recognize the tag, are added and the bound fraction of labeled protein is separated from the unbound fraction using magnets. The amount of labeled protein that is captured can be determined in an indirect way by measuring the signal of the labeled protein remained in the unbound fraction. The described liquid phase affinity assay is extremely useful when conformational conversion sensitive proteins are assayed. The development and application of the assay is demonstrated for the interaction between poliovirus and poliovirus recognizing nanobodies(1). Since poliovirus is sensitive to conformational conversion(2) when attached to a solid surface (unpublished results), the use of ELISA is limited and a liquid phase based system should therefore be preferred. An example of a liquid phase based system often used in polioresearch(3,4) is the micro protein A-immunoprecipitation test(5). Even though this test has proven its applicability, it requires an Fc-structure, which is absent in the nanobodies(6,7). However, as another opportunity, these interesting and stable single-domain antibodies(8) can be easily engineered with different tags. The widely used (His)(6)-tag shows affinity for bivalent ions such as nickel or cobalt, which can on their turn be easily coated on magnetic beads. We therefore developed this simple quantitative affinity capture assay based on cobalt coated magnetic beads. Poliovirus was labeled with (35)S to enable unhindered interaction with the nanobodies and to make a quantitative detection feasible. The method is easy to perform and can be established with a low cost, which is further supported by the possibility of effectively regenerating the magnetic beads. PMID:22688388

Schotte, Lise; Rombaut, Bart; Thys, Bert

2012-01-01

356

Total synthesis of elastin peptide using high pressure-liquid phase synthesis assisted by a soluble tag strategy.  

PubMed

A highly aggregating elastin peptide was prepared efficiently using a high pressure-liquid phase synthesis approach assisted by a soluble tag strategy. Two standard syringes were connected to each other to construct a reactor. This simple reactor was used to apply high pressure to the highly viscous reaction mixture thereby maintaining its fluidity. The reactions were completely inhibited due to aggregation when conducted in a standard flask reactor, whereas our high pressure approach accelerated the couplings to realize complete conversion within 5-7 min. All steps were conducted at 0.10 M concentration, affording grams of the desired product. PMID:25494479

Okada, Yohei; Hosoya, Shoichi; Suzuki, Hidenobu; Chiba, Kazuhiro

2014-12-19

357

Liquid-phase immunoassay utilizing binding reactions between magnetic markers and targets in the presence of a magnetic field  

NASA Astrophysics Data System (ADS)

We developed a new and improved method for the liquid-phase detection of biological targets using magnetic markers. Unlike conventional studies, we performed a binding reaction between markers and targets in the presence of a magnetic field. This field acts to prevent the Brownian rotation of markers during the reaction. In this case, markers are bound to the targets with their magnetic moments (m’s) aligned, which is in contrast to the conventional case where m’s are randomly oriented after the reaction. As a result, we could obtain much larger signals from the bound markers without increasing the blank signal from the free markers.

Enpuku, Keiji; Ueoka, Yuta; Sakakibara, Tatsuto; Ura, Masakazu; Yoshida, Takashi; Mizoguchi, Takako; Kandori, Akihiko

2014-09-01

358

Liquid–liquid phase behaviour, liquid–liquid density, and interfacial tension of multicomponent systems at 298 K  

Microsoft Academic Search

Experimental liquid–liquid phase diagrams are presented for the multicomponent systems isooctane–benzene–(80mass% methanol+20mass% water)–5mass% isobutyl alcohol (2-methyl-1-propanol) and isooctane–benzene–(80mass% methanol+20mass% water)–15mass% isobutyl alcohol, at 298.15K. The density and interfacial tension of conjugate phases of concentration located in the isothermal binodal have been determined at 298.15K for the partially miscible systems: isooctane–benzene–methanol, isooctane–benzene–(80mass% methanol+20mass% water), isooctane–benzene–(80mass% methanol+20mass% water)–5mass% isobutyl alcohol, and isooctane–benzene–(80mass%

Blanca Estela García-Flores; Arturo Trejo; Jacinto Águila-Hernández

2007-01-01

359

Epitaxial gallium phosphide on silicon (111) from the liquid phase for solar cell applications  

NASA Astrophysics Data System (ADS)

Multijunction structures composed of III-V materials grown on a III-V or Ge substrate are often employed to achieve high solar cell conversion efficiencies. However, it is advantageous to consider alternate substrates that can lower cost, such as the well developed Si, as a platform on which multi-junction solar structures can be grown. Growth of III-Vs on an alternate substrate such as Si requires careful consideration of the lattice constant mismatch as this will greatly influence the physical and electronic quality of the film. A material that is closely lattice matched with Si is Gallium phosphide (GaP). This lattice matching allows for good quality epitaxial growth and GaP can be alloyed with other III-V materials to tune the bandgap, which is an important property for multi-junction solar cells. In this work, liquid phase epitaxy (LPE) was used to grow GaP films on miscut and aligned Si (111) substrates. The films have been characterized by SEM and XRD to show that the GaP films are planar with uniform morphology and good crystal quality. The composition has been found by XPS and Auger spectroscopy to be GaP with 10-20% Si content. High resolution XRD analysis confirmed that the films are epitaxial and have a threading dislocation density of 2 x 106 cm-2 for growth on aligned Si (111) which is promising for the development of III-V/Si multi-junction solar cells. A four junction solar cell stack that includes a Si junction has a theoretical efficiency greater than 50%. In this structure, a GaP layer can act as a buffer layer on Si to growth other III-V materials with optimized bandgaps. Therefore, the effect of a GaP film on a Si solar cell was investigated. The results of this investigation show that growing a GaP layer on a Si solar cell fabricated by a diffusion process increases the series resistance and has lower Voc. Quantum efficiency measurements show that there is some reduction in efficiency of collection of carriers excited by wavelengths shorter than 450 nm which could be due to absorption in the GaP layer and recombination at the interface. A GaP layer grown on a p-type Si substrate exhibited similar current voltage characteristics as the GaP layer grown on a Si solar cell. SIMS depth profiling showed that phosphorus diffusion occurs during growth of GaP, creating a n-type doped. This indicates that a GaP layer can be grown on a Si substrate to directly make a solar cell. Epitaxial GaP layers have been grown on Si (111) substrates with high crystal quality which is promising for use as a buffer layer. Growth of GaP on Si can be used to directly fabricate a Si solar cell. This GaP/Si structure will be beneficial to solar cell and many other optoelectronic applications.

Huang, Susan R.

360

Unraveling the behavior of the individual ionic activity coefficients on the basis of the balance of ion-ion and ion-water interactions.  

PubMed

We investigate the individual activity coefficients of pure 1:1 and 2:1 electrolytes using our theory that is based on the competition of ion-ion (II) and ion-water (IW) interactions (Vincze et al. J. Chem. Phys. 2010, 133, 154507). The II term is computed from grand canonical Monte Carlo simulations on the basis of the implicit solvent model of electrolytes using hard sphere ions with Pauling radii. The IW term is computed on the basis of Born's treatment of solvation using experimental hydration free energies. The two terms are coupled through the concentration-dependent dielectric constant of the electrolyte. We show that the theory can provide valuable insight into the nonmonotonic concentration dependence of individual activity coefficients. We compare our theoretical predictions against experimental data measured by electrochemical cells containing ion-specific electrodes. We find good agreement for 2:1 electrolytes, while the accuracy is worse for 1:1 systems. This deviation in accuracy is explained by the fact that the two competing terms (II and IW) are much larger in the 2:1 case, resulting in smaller relative errors. The difference of the excess chemical potentials of cations and anions is determined by asymmetries in the properties of the two ions: charge, radius, and hydration free energies. PMID:25549274

Valiskó, Mónika; Boda, Dezs?

2015-01-29

361

The nonmonotonic concentration dependence of the mean activity coefficient of electrolytes is a result of a balance between solvation and ion-ion correlations  

NASA Astrophysics Data System (ADS)

We propose a simple model to explain the nonmonotonic concentration dependence of the mean activity coefficient of simple electrolytes without using any adjustable parameters. The primitive model of electrolytes is used to describe the interaction between ions computed by the adaptive grand canonical Monte Carlo method. For the dielectric constant of the electrolyte, we use experimental concentration dependent values. This is included through a solvation term in our treatment to describe the interaction between ions and water that changes as the dielectric constant changes with concentration. This term is computed by a Born-treatment fitted to experimental hydration energies. Our results for LiCl, NaCl, KCl, CsCl, NaBr, NaI, MgCl2, CaCl2, SrCl2, and BaCl2 demonstrate that the principal reason of the nonmonotonic behavior of the activity coefficient is a balance between the solvation and ion-ion correlation terms. This conclusion differs from previous studies that assumed that it is the balance of hard sphere repulsion and electrostatic attraction that produces the nonmonotonic behavior. Our results indicate that the earlier assumption that solvation can be taken into account by a larger, "solvated" ionic radius should be reconsidered. To explain second order effects (such as dependence on ionic size), we conclude that explicit water models are needed.

Vincze, Julianna; Valiskó, Mónika; Boda, Dezs?

2010-10-01

362

ERRORS IN APPLYING LOW ION-STRENGTH ACTIVITY COEFFICIENT ALGORITHMS TO HIGHER IONIC-STRENGTH AQUATIC MEDIA  

EPA Science Inventory

The toxicological and regulatory communities are currently exploring the use of free-ion-activity- models as a means of reducing uncertainties in current methods for assessing metals bioavailabi- lity from contaminated aquatic media. While most practitioners would support the des...

363

Novel one-step headspace dynamic in-syringe liquid phase derivatization-extraction technique for the determination of aqueous aliphatic amines by liquid chromatography with fluorescence detection.  

PubMed

A novel one-step headspace (HS) dynamic in-syringe (DIS) based liquid-phase derivatization-extraction (LPDE) technique has been developed for the selective determination of two short-chain aliphatic amines (SCAAs) in aqueous samples using high performance liquid chromatography (HPLC) with fluorescence detection (FLD). Methylamine (MA) and dimethylamine (DMA) were selected as model compounds of SCAAs. In this method, a micro-syringe pre-filled with derivatizing reagent solution (9-fluorenylmethyl chloroformate) in the barrel was applied to achieve the simultaneous derivatization and extraction of two methylamines evolved from alkalized aqueous samples through the automated reciprocated movements of syringe plunger. After the derivatization-extraction process, the derivatized phase was directly injected into HPLC-FLD for analysis. Parameters influencing the evolution of methylamines and the HS-DIS-LPDE efficiency, including sample pH and temperature, sampling time, as well as the composition of derivatization reagent, reaction temperature, and frequency of reciprocated plunger movements, were thoroughly examined and optimized. Under optimal conditions, detections were linear in the range of 25-500?gL(-1) for MA and DMA with correlation coefficients all above 0.995. The limits of detection (based on S/N=3) were 5 and 19ngmL(-1) for MA and DMA, respectively. The applicability of the developed method was demonstrated for the determination of MA and DMA in real water samples without any prior cleanup of the sample. The present method provides a simple, selective, automated, low cost and eco-friendly procedure to determine aliphatic amines in aqueous samples. PMID:23591526

Muniraj, Sarangapani; Shih, Hou-Kung; Chen, Ying-Fang; Hsiech, Chunming; Ponnusamy, Vinoth Kumar; Jen, Jen-Fon

2013-06-28

364

Determination of ammonium in aqueous samples using new headspace dynamic in-syringe liquid-phase microextraction with in situ derivitazation coupled with liquid chromatography-fluorescence detection.  

PubMed

A new simultaneous derivatization and extraction method for the preconcentration of ammonia using new one-step headspace dynamic in-syringe liquid-phase microextraction with in situ derivatization was developed for the trace determination of ammonium in aqueous samples by liquid chromatography with fluorescence detection (LC-FLD). The acceptor phase (as derivatization reagent) containing o-phthaldehyde and sodium sulfite was held within a syringe barrel and immersed in the headspace of sample container. The gaseous ammonia from the alkalized aqueous sample formed a stable isoindole derivative with the acceptor phase inside the syringe barrel through the reciprocated movements of plunger. After derivatization-cum-extraction, the acceptor phase was directly injected into LC-FLD for analysis. Parameters affecting the ammonia evolution and the extraction/derivatization efficiency such as sample matrix, pH, temperature, sampling time, and the composition of derivatization reagent, reaction temperature, and frequency of reciprocated plunger, were studied thoroughly. Results indicated that the maximum extraction efficiency was obtained by using 100?L derivatization reagent in a 1-mL gastight syringe under 8 reciprocated movements of plunger per min to extract ammonia evolved from a 20mL alkalized aqueous solution at 70°C (preheated 4min) with 380rpm stirring for 8min. The detection was linear in the concentration range of 0.625-10?M with the correlation coefficient of 0.9967 and detection limit of 0.33?M (5.6ng mL(-1)) based on SN(-1)=3. The method was applied successfully to determine ammonium in real water samples without any prior cleanup of the samples, and has been proved to be a simple, sensitive, efficient and cost-effective procedure for trace ammonium determination in aqueous samples. PMID:23140954

Muniraj, Sarangapani; Yan, Cheing-Tong; Shih, Hou-Kung; Ponnusamy, Vinoth Kumar; Jen, Jen-Fon

2012-11-19

365

Thermal conductivities of solid and liquid phases for pure Al, pure Sn and their binary alloys  

Microsoft Academic Search

The variations of thermal conductivities of solid phases versus temperature for pure Sn, pure Al and Sn–0.5wt.% Al, Sn–2.2wt.% Al, Sn–25wt.% Al, Sn–50wt.% Al, Sn–75wt.% Al binary alloys were measured with a radial heat flow apparatus. From thermal conductivity variations versus temperature, the thermal conductivities of the solid phases at their melting temperature and temperature coefficients for same materials were

Fatma Meydaneri; Buket Saatçi; Mehmet Özdemir

2010-01-01

366

Thermal conductivities of solid and liquid phases for neopentylglycol, aminomethylpropanediol and their binary alloy  

Microsoft Academic Search

The variations of thermal conductivities of solid phases versus temperature for neopentylglycol (NPG), 2-amino-2-methyl-1,3-propanediol (AMPD) and AMPD–42.2mol% NPG alloy were measured with a radial heat flow apparatus. From the graphs of the solid phases thermal conductivity variations versus temperature, the thermal conductivities of the solid phases at their melting temperature and temperature coefficients for same materials were also found to

S. Akbulut; Y. Ocak; K. Keslioglu; N. Marasli

2009-01-01

367

Preservation of Geometrical Integrity of Supersolidus-Liquid-Phase-Sintered SKD11 Tool Steels Prepared with Powder Injection Molding  

NASA Astrophysics Data System (ADS)

The powder injection molded SKD11 tool steels often manifest shape retention problems during supersolidus liquid phase sintering due to the difficulties in controlling the amount of liquid phase. The typical temperature range for the sintering of SKD11 is only 10 K, between 1503 and 1513 K (1230 and 1240 °C), and this narrow sintering range demands a special furnace with very uniform temperature distribution. Through the addition of carbides, in particular TiC, this problem is resolved by enlarging the liquid + ? + carbide region in the phase diagram and by impeding the grain growth with the carbides. The resulting sintering window is broadened to 40 K, between 1513 and 1553 K (1240 and 1280 °C). The relevant mechanisms on the improvement of shape retention are discussed with a focus on the effect of carbide addition on the changes in the phase diagram and the microstructure. A guideline for the selection of effective carbides is also proposed based on the experimental results and the phase diagram analyses.

Chuang, K. H.; Hwang, K. S.

2011-07-01

368

Immunoassay of paralytic shellfish toxins by moving magnetic particles in a stationary liquid-phase lab-on-a-chip.  

PubMed

In this study, we devised a stationary liquid-phase lab-on-a-chip (SLP LOC), which was operated by moving solid-phase magnetic particles in the stationary liquid phase. The SLP LOC consisted of a sample chamber to which a sample and reactants were added, a detection chamber containing enzyme substrate solution, and a narrow channel connecting the two chambers and filled with buffer. As a model system, competitive immunoassays of saxitoxin (STX), a paralytic shellfish toxin, were conducted in the SLP LOC using protein G-coupled magnetic particles (G-MPs) as the solid phase. Anti-STX antibodies, STX-horseradish peroxidase conjugate, G-MPs, and a STX sample were added to the sample chamber and reacted by shaking. While liquids were in the stationary state, G-MPs were transported from the sample chamber to the detection chamber by moving a magnet below the LOC. After incubation to allow the enzymatic reaction to occur, the absorbance of the detection chamber solution was found to be reciprocally related to the STX concentration of the sample. Thus, the SLP LOC may represent a novel, simple format for point-of-care testing applications of enzyme-linked immunosorbent assays by eliminating complicated liquid handling steps. PMID:25460894

Kim, Myoung-Ho; Choi, Suk-Jung

2015-04-15

369

Gaseous hexane biodegradation by Fusarium solani in two liquid phase packed-bed and stirred-tank bioreactors.  

PubMed

Biofiltration of hydrophobic volatile pollutants is intrinsically limited by poor transfer of the pollutants from the gaseous to the liquid biotic phase, where biodegradation occurs. This study was conducted to evaluate the potential of silicone oil for enhancing the transport and subsequent biodegradation of hexane by the fungus Fusarium solani in various bioreactor configurations. Silicone oil was first selected among various solvents for its biocompatibility, nonbiodegradability, and good partitioning properties toward hexane. In batch tests, the use of silicone oil improved hexane specific biodegradation by approximately 60%. Subsequent biodegradation experiments were conducted in stirred-tank (1.5 L) and packed-bed (2.5 L) bioreactors fed with a constant gaseous hexane load of 180 g x m(-3)(reactor) x h(-1) and operated for 12 and 40 days, respectively. In the stirred reactors, the maximum hexane elimination capacity (EC) increased from 50 g x m(-3)(reactor) x h(-1) (removal efficiency, RE of 28%) in the control not supplied with silicone oil to 120 g x m(-3)(reactor) x h(-1) in the biphasic system (67% RE). In the packed-bed bioreactors, the maximum EC ranged from 110 (50% RE) to 180 g x m(-3)(reactor) x h(-1) (> 90% RE) in the control and two-liquid-phase systems, respectively. These results represent, to the best of our knowledge, the first reported case of fungi use in a two-liquid-phase bioreactor and the highest hexane removal capacities so far reported in biofilters. PMID:16646479

Arriaga, Sonia; Muñoz, Raúl; Hernández, Sergio; Guieysse, Benoit; Revah, Sergio

2006-04-01

370

Preconcentration of aqueous dyes through phase-transfer liquid-phase microextraction with a room-temperature ionic liquid.  

PubMed

In this study, we employed the room-temperature ionic liquid [bmim][PF(6)] as both ion-pair agent and an extractant in the phase-transfer liquid-phase microextraction (PTLPME) of aqueous dyes. In the PTLPME method, a dye solution was added to the extraction solution, comprising a small amount of [bmim][PF(6)] in a relatively large amount of CH(2)Cl(2), which serves as the disperser solvent to an extraction solution. Following extraction, CH(2)Cl(2) was evaporated from the extractant, resulting in the extracted dyes being concentrated in a small volume of the ionic liquid phase to increase the enrichment factor. The enrichment factors of for the dye Methylene Blue, Neutral Red, and Methyl Red were approximately 500, 550 and 400, respectively; their detection limits were 0.014, 0.43, and 0.02 ?g L(-1), respectively, with relative standard deviations of 4.72%, 4.20%, and 6.10%, respectively. PMID:22884207

Chen, Hsiu-Liang; Chang, Shuo-Kai; Lee, Chia-Ying; Chuang, Li-Lin; Wei, Guor-Tzo

2012-09-12

371

TeO{sub 2} liquid phase: Viscosity measurements and evaluation of the thermal conductivity from crystal growth experiments  

SciTech Connect

Current applications of paratellurite TeO{sub 2} in optics and nuclear physics require improving the yield and optical quality of synthesized single crystals. Modelling of the growth process is a useful tool for such purpose, however, involving the knowledge of several thermodynamic parameters of both solid and liquid phase of the compound. This work describes the determination of two main unknown ones, namely dynamic viscosity {eta} and thermal conductivity {lambda}{sub l} of the liquid phase. Measurements of {eta} are performed by means of a specifically designed apparatus; over a 40 K temperature interval above the melting point we find a mean value of 0.028 Pa.s. This data is used in commercial software to depict the evolution of the solid-liquid interface in our Bridgman growth set-up. Comparison of the distribution of defects observed in grown ingots with the results of modelling allows estimating {lambda}{sub l} as lying in the range 3.50-3.75 W m{sup -1} K{sup -1}.

Veber, P. [Institut Carnot de Bourgogne, UMR CNRS no5209, Universite de Bourgogne, F-21078 Dijon (France)], E-mail: philippe.veber@u-bourgogne.fr; Mangin, J. [Institut Carnot de Bourgogne, UMR CNRS no5209, Universite de Bourgogne, F-21078 Dijon (France)

2008-11-03

372

Solidification of floating organic drop liquid-phase microextraction cell fishing with gas chromatography-mass spectrometry for screening bioactive components from Amomum villosum Lour.  

PubMed

In this study, a novel solidification of floating organic drop liquid-phase microextraction cell fishing with gas chromatography-mass spectrometry (SFOD-LPME-CF-GC-MS) method was established and used to screen, isolate and analyze bioactive components from Amomum villosum Lour. extract. Through comparision of its effect on the models of normal cell and inflammatory cells, anti-inflammatory active components of essential oil from A. villosum Lour. were readily screened, and the components obtained are in agreement with related pharmacological articles. SFOD-LPME-CF-GC-MS was used to analyze the interaction of A. villosum Lour. extracts with normal and lipopolysaccharide-stimulated RAW264.7 macrophage cells. The effect of A. villosum Lour. essential oil extracts in the LPS-stimulated RAW264.7 model were also assessed in terms of cytotoxicity and nitric oxide production as an indication of bioactivity. Three potentially bioactive components were identified, demonstrating that SFOD-LPME-CF-GC-MS can be used successfully in the drug-screening process. This approach avoids the requirement for protein precipitation, but more importantly, generates a high concentration ratio, allowing analysis of trace components in traditional Chinese medicines. SFOD-LPME-CF-GC-MS is a simple, fast, effective and reliable method for the screening and analysis of bioactive components, and it can be extended to screen other bioactive components from TCMs. Copyright © 2014 John Wiley & Sons, Ltd. PMID:25251881

Xue, Xue; Yang, Depo; Wang, Dongmei; Xu, Xinjun; Zhu, Longping; Zhao, Zhimin

2014-09-24

373

Modeling of the Phase behavior of light (C2 & C3) olefins in liquid phase epoxidation systems and experimental determination of gas/liquid mass transfer coefficients  

E-print Network

-115 o C and about 82.7 bars pressure in presence of a copper-chromium catalyst, with copper dispersed in a zinc oxide matrix. The major side reaction of this step is the excessive hydrogenation of ACP to ethylbenzene. This process conditions ()52... of ethylene oxide are the chlorohydrin process and the vapor phase oxidation of ethylene which was developed in 1931 by T. E. Lefort [32]. Union Carbide Chemicals was the first to manufacture EO commercially using either route. This business is now owned...

Ghanta, Madhav

2008-01-01

374

Liquid-phase hydrogenation of 1,5-cyclooctadiene on zeolite-encapsulated noble metal–salen complexes 1 Dedicated to Professor Lovat V.C. Rees in recognition and appreciation of his lifelong devotion to zeolite science and his outstanding achievements in this field. 1  

Microsoft Academic Search

The preparation of palladium and rhodium complexes of the Schiff base salen (N,N?-bis-(salicylidene)-ethylenediamine) in the intracrystalline cavities of zeolites with the FAU and the EMT framework topology is reported. The host\\/guest compounds obtained are active catalysts for the selective hydrogenation of 1,5-cyclooctadiene in the liquid phase at 60°C and under a hydrogen pressure of 1.5MPa. In addition, the immobilization of

S. Ernst; H. Disteldorf; X. Yang

1998-01-01

375

Activity coefficients for NaCl-monosaccharide (D-glucose, D-galactose, D-xylose, D-arabinose)-water systems at 298.15 K.  

PubMed

Electrochemical cells with a sodium ion selectivity electrode (Na-ISE) versus a chloride ion selectivity electrode (Cl-ISE) as a reference electrode were used to determine the activity coefficients for NaCl-monosaccharide (D-glucose, D-galactose, D-xylose, and D-arabinose) systems in water at 298.15 K. A comparison of the results thus obtained was made with those determined by another electromotive force (emf) method. It is shown that agreement is excellent. The Gibbs free energy parameters of the interactions between these sugars and NaCl in water were evaluated together with the parameter C1(CHOH, exo), indicating the interaction of the exocyclic CHOH group of saccharide molecules and NaCl. The results suggested that the interactions of these monosaccharides with NaCl are controlled mostly by the dominant conformer of their molecules in water. PMID:10741826

Zhuo, K; Wang, J; Wang, H

2000-03-24

376

Modeling solubility, acid-base properties and activity coefficients of amoxicillin, ampicillin and (+)6-aminopenicillanic acid, in NaCl(aq) at different ionic strengths and temperatures.  

PubMed

The total solubility of three penicillin derivatives was determined, in pure water and NaCl aqueous solutions at different salt concentrations (from ?0.15 to 1.0 mol L(-1) for ampicillin and amoxicillin, and from ?0.05 to 2.0 mol L(-1) for (+)6-aminopenicillanic acid), using the shake-flask method for generating the saturated solutions, followed by potentiometric analysis. The knowledge of the pH of solubilization and of the protonation constants determined in the same experimental conditions, allowed us to calculate, by means of the mass balance equations, the solubility of the neutral species at different ionic strength values, to model its dependence on the salt concentration and to determine the corresponding values at infinite dilution. The salting parameter and the activity coefficients of the neutral species were calculated by the Setschenow equation. The protonation constants of ampicillin and amoxicillin, determined at different temperatures (from T=288.15 to 318.15K), from potentiometric and spectrophotometric measurements, were used to calculate, by means of the Van't Hoff equation, the temperature coefficients at different ionic strength values and the corresponding protonation entropies. The protonation enthalpies of the (+)6-aminopenicillanic acid were determined by isoperibol calorimetric titrations at T=298.15K and up to I=2.0 mol L(-1). The dependence of the protonation constants on ionic strength was modeled by means of the Debye-Hückel and SIT (Specific ion Interaction Theory) approaches, and the specific interaction parameters of the ionic species were determined. The hydrolysis of the ?-lactam ring was studied by spectrophotometric and H NMR investigations as a function of pH, ionic strength and time. Potentiometric measurements carried out on the hydrolyzed (+)6-aminopenicillanic acid allowed us to highlight that the opened and the closed ?-lactam forms of the (+)6-aminopenicillanic acid have quite different acid-base properties. An analysis of literature solubility, protonation constants, enthalpies and activity coefficients is reported too. PMID:22903046

Crea, Francesco; Cucinotta, Daniela; De Stefano, Concetta; Milea, Demetrio; Sammartano, Silvio; Vianelli, Giuseppina

2012-11-20

377

Commercial-scale demonstration of the Liquid Phase Methanol (LPMEOH{trademark}) process. Technical progress report number 11, January 1--March 31, 1997  

SciTech Connect

During this quarter, the third draft of the Topical Report on Process Economics Studies was issued for review. A recommendation to continue with design verification testing on the coproduction of methanol and dimethyl ether (DME) was made. A liquid phase dimethyl ether (LPDME) catalyst system with reasonable long-term activity and stability is being developed, and a decision to proceed with a proof-of-concept test run at the LaPorte Alternative Fuels Development Unit (AFDU) is pending the release of a memo from Air Products on the catalyst targets and corresponding economics for a commercially successful LPDME catalyst. The off-site product-use test plan is to be updated in June of 1997. During this quarter, Air Products and Acurex Environmental Corporation continued developing the listing of product-use test participants who are involved in fuel cell, transportation, and stationary power plant applications. Start-up activities (Task 3.1) began during the reporting period, and coal-derived synthesis gas (syngas) was introduced to the demonstration unit. The recycle compressor was tested successfully on syngas at line pressure of 700 psig, and the reactor loop reached 220 C for carbonyl burnout. Iron carbonyl in the balanced gas feed remained below the 10 ppbv detection limit for all samples but one. Within the reactor loop, iron carbonyl levels peaked out near 200 ppbv after about 40 hours on-stream, before decreasing to between 10--20 ppbv at 160 hours on -stream. Nickel carbonyl measurements reached a peak of about 60 ppbv, and decreased at all sampling locations to below the 10 ppbv detection limit by 70 hours on-stream. Catalyst activation of the nine 2,250 lb batches required for the initial catalyst charge began and concluded. All batches met or slightly exceeded the theoretical maximum uptake of 2.82 SCF of reducing gas/lb catalyst.

NONE

1997-06-11

378

Condensation coefficient of methanol vapor near vapor-liquid equilibrium states  

NASA Astrophysics Data System (ADS)

This paper is concerned with the nonequilibrium condensation from a vapor to a liquid phase on the plate endwall of a shock tube behind a reflected shock wave. The growth of a liquid film on the endwall is measured by an optical interferometer using a laser beam. The experiment is carefully conducted on the precisely designed apparatus, and thereby the condensation coefficient of methanol vapor is determined in a wide range of vapor-liquid conditions from near to far from equilibrium states. The result shows that the condensation coefficient increases with the increase of the ratio of number densities of vapor and saturated vapor at the interface.

Fujikawa, S.; Yano, T.; Ichijo, M.; Iwanami, K.

379

Continuous-flow, atmospheric-pressure microplasmas: a versatile source for metal nanoparticle synthesis in the gas or liquid phase  

NASA Astrophysics Data System (ADS)

Continuous-flow, atmospheric-pressure microplamas are a unique class of plasmas that are highly suitable for emerging nanomaterials applications. Here, we present two schemes for the preparation of metal nanoparticles based on these plasma sources. Nanoparticles are synthesized in the gas phase by non-thermal dissociation of vapor precursors in a microplasma reactor. Monometallic Ni and Fe nanoparticles, as well as compositionally controlled NiFe bimetallic nanoparticles, can be grown with tunable mean diameters between 1 and 5 nm and narrow size distributions. Alternatively, colloidal metal nanoparticles are produced directly in aqueous solutions. Metal cations generated from anodic dissolution of a bulk metal or present in the form of metal salt are reduced by the microplasma to form nanoparticles and capped by a stabilizer. Both approaches are low cost, scalable and general and should allow a wide range of nanoparticle materials to be synthesized in the gas or liquid phase.

Chiang, Wei-Hung; Richmonds, Carolyn; Mohan Sankaran, R.

2010-06-01

380

Liquid Phase Epitaxial Growth of InAs1-x-yPxSby on InAs Substrate  

NASA Astrophysics Data System (ADS)

InAsPSb quaternary alloy, lattice-matched to InAs substrate, is promising material for 3-4 ?m wavelength optical sources. This quaternary alloy was grown on (001) InAs substrate by liquid phase epitaxy. The lattice constant for this epitaxial layer, grown by the equilibrium cooling method, increases along the growth direction, because P content in this quaternary decreases and Sb content increases along the growth direction. The InAs-InP-InSb pseudoternary phase diagram was also calculated. From these results, it was shown that in order to obtain a quaternary solid with higher P and Sb concentration under lattice-matching to InAs substrate condition, lower growth temperature is required.

Kobayashi, Naoki; Horikoshi, Yoshiji

1981-12-01

381

Characterization of Transient Liquid-Phase Bonded Joints in a Copper-Beryllium Alloy with Silver-base Interlayer  

NASA Astrophysics Data System (ADS)

Transient liquid-phase diffusion bonding was employed to join copper-beryllium alloy using three silver-base interlayers. The bonding process was carried out at different temperatures under argon and vacuum atmospheres for various hold times. Interfacial microstructures were examined by scanning electron microscopy. Microhardness, tensile, and fatigue tests were used for evaluating the mechanical properties. Maximum tensile strength of 156.45 MPa was obtained for bonds processed at 780 °C. Fatigue strength of bonds fabricated in vacuum was higher than those of bonds prepared in argon atmosphere. The diffusion of the main elements from the interlayers into the base metal was the main controlling factor pertaining to the microstructural evolution of the joint interface.

Mazar Atabaki, M.

2012-06-01

382

Tailoring of high-order multiple emulsions by the liquid-liquid phase separation of ternary mixtures.  

PubMed

Multiple emulsions with an "onion" topology are useful vehicles for drug delivery, biochemical assays, and templating materials. They can be assembled by ternary liquid phase separation by microfluidics, but the control over their design is limited because the mechanism for their creation is unknown. Herein we show that phase separation occurs through self-similar cycles of mass transfer, spinodal decomposition or nucleation, and coalescence into multiple layers. Mapping out the phase diagram shows a linear relationship between the diameters of concentric layers, the slope of which depends on the initial ternary composition and the molecular weight of the surfactant. These general rules quantitatively predict the number of droplet layers (multiplicity), which we used to devise self-assembly routes for polymer capsules and liposomes. Moreover, we extended the technique to the assembly of lipid-stabilized droplets with ordered internal structures. PMID:25199633

Haase, Martin F; Brujic, Jasna

2014-10-27

383

Evidence for the quantum vortex liquid phase in thick a-Mo xSi 1- x films  

NASA Astrophysics Data System (ADS)

We perform detailed measurements of the ac complex resistivity of thick amorphous (a-)Mo xSi 1- x films at low temperatures T to study the vortex states near T=0 K. We obtain evidence for the vortex-glass transition (VGT) down to low enough temperatures T?0.1 K and up to high fields B near the upper critical field Bc2(0) at T=0 K. In the limit T?0 K, the VGT line Bg( T) becomes independent of T and extrapolates to a field Bg(0) lower than Bc2(0). From this result, together with the finding that Bg(0) coincides with the T=0 K superconductor-metal transition, we conclude that the metallic quantum vortex liquid phase is present in the field region Bg(0)< B< Bc2(0).

Okuma, S.; Imamoto, Y.; Morita, M.

2001-11-01

384

Ab-initio MD simulation on the Liquid-liquid Phase Transition in AlSi Alloy  

NASA Astrophysics Data System (ADS)

Motivated by the recent experimental paper [X.F.Bian et al. Mater. Lett. 44, 54 (2000); F.Q.Zu et al. Phy s. Rev. lett 89, 125505,(2001)], we use ab-initio molecular-dynamics method to study the phase transitions in binary alloy liquid at high temperature. Our calculations are based on the density functional theory with local density approximation, the interaction between core and valence electrons is modeled by ultrasoft pseudopotential. The simulation cell contains 54 Al atoms and 10 Si atoms, which are simulated from 900K-2400K in the liquid phase. We have calculated the temperature-dependent energy, volume, pair-correlation function. But we did not see the expected phase transition as observed in experiment. The possible reason of the inconsistence between simulation and experimental results are discussed.

Ji, M.; Gong, X. G.

2003-03-01

385

Exploring the solid-liquid phase change of an adapted Dzugutov model using generalized replica exchange method.  

PubMed

The generalized replica exchange method (gREM) is applied to simulate a solid-liquid phase change in an adapted Dzugutov model system. The idea of gREM is to incorporate the merit of sampling from a generalized ensemble into the replica exchange paradigm. The generalized ensemble weights are determined from effective temperatures tailored for this system, through an inverse mapping strategy. The ordered and disordered phases are smoothly joined together through a succession of unimodal energy distributions, providing a continuous transformation from an isotropic liquid into an amorphous solid phase under the given condition. The phase change temperature is determined by evaluation of various thermodynamic and structural order parameters. The increasing tendency for icosahedral local order under cooling is quantified using bond order parameters. The ergodic measure is used to demonstrate the advantage of gREM over the traditional temperature-based REM in sampling the phase change region. PMID:22452532

Lu, Qing; Kim, Jaegil; Straub, John E

2012-07-26

386

Bonding Interface Formation between Mg Alloy and Steel by Liquid-phase Bonding using the Ag Interlayer  

NASA Astrophysics Data System (ADS)

Liquid-phase bonding between a Mg alloy (AZ31) and low-carbon steel was attempted at 773 K (500 °C) using Ag as an interlayer that forms a eutectic melt with the Mg alloy at this temperature. On the AZ31 side, eutectic melting and subsequent isothermal solidification were observed, and it was confirmed that the solidification of the eutectic liquid was promoted by the diffusion of Ag into the AZ31 base metal. On the steel side, Al was transported from AZ31 during the eutectic melting and isothermal solidification. This transported Al was enriched at the steel surface and reacted with steel to form a uniform, thin Fe-Al intermetallic compound layer. After the isothermal solidification, strong bonding was achieved via the thin intermetallic compound layer between AZ31 and steel, and no Ag remained at the bonding interface. The strength of the joint was found to be higher than the yield strength of AZ31.

Koba, Masaki; Araki, Toshio; Nambu, Shoichi; Inoue, Junya; Koseki, Toshihiko

2012-02-01

387

Rapid liquid phase sintered Mn doped BiFeO{sub 3} ceramics with enhanced polarization and weak magnetization  

SciTech Connect

Single-phase BiFe{sub 1-x}Mn{sub x}O{sub 3} multiferroic ceramics have been synthesized by rapid liquid phase sintering method to study the influence of Mn substitution on their crystal structure, dielectric, magnetic, and ferroelectric behaviors. From XRD analysis it is seen that Mn substitution does not affect the crystal structure of the BiFe{sub 1-x}Mn{sub x}O{sub 3} system. An enhancement in magnetization was observed for BiFe{sub 1-x}Mn{sub x}O{sub 3} ceramics. However, the ferooelectric hysteresis loops were not really saturated, we observed a spontaneous polarization of 10.23 {mu}C/cm{sup 2} under the applied field of 42 kV/cm and remanent polarization of 3.99 {mu}C/cm{sup 2} for x=0.3 ceramic.

Kumar, Manoj; Yadav, K. L. [Smart Material Research Laboratory, Department of Physics, Indian Institute of Technology, Roorkee-247667 (India)

2007-12-10

388

Mode-locked Er-doped fiber laser based on liquid phase exfoliated Sb2Te3 topological insulator  

NASA Astrophysics Data System (ADS)

In this paper, femtosecond pulse generation in an Er-doped fiber laser is reported. The laser is passively mode-locked by an antimony telluride (Sb2Te3) topological insulator (TI) saturable absorber (SA) placed on a side-polished fiber. The Sb2Te3/chitosan suspension used to prepare the SA was obtained via liquid phase exfoliation from bulk Sb2Te3.Ultra-short 449?fs soliton pulses were generated due to the interaction between the evanescent field propagated in the fiber cladding and the Sb2Te3 layers. The optical spectrum is centered at 1556?nm with 6?nm of full-width at half maximum bandwidth. The presented method benefits from a much better repeatability compared to mechanical exfoliation.

Boguslawski, J.; Sotor, J.; Sobon, G.; Tarka, J.; Jagiello, J.; Macherzynski, W.; Lipinska, L.; Abramski, K. M.

2014-10-01

389

Antireflection and SiO2 Surface Passivation by Liquid-Phase Chemistry for Efficient Black Silicon Solar Cells: Preprint  

SciTech Connect

We report solar cells with both black Si antireflection and SiO2 surface passivation provided by inexpensive liquid-phase chemistry, rather than by conventional vacuum-based techniques. Preliminary cell efficiency has reached 16.4%. Nanoporous black Si antireflection on crystalline Si by aqueous etching promises low surface reflection for high photon utilization, together with lower manufacturing cost compared to vacuum-based antireflection coating. Ag-nanoparticle-assisted black Si etching and post-etching chemical treatment recently developed at NREL enables excellent control over the pore diameter and pore separation. Performance of black Si solar cells, including open-circuit voltage, short-circuit current density, and blue response, has benefited from these improvements. Prior to this study, our black Si solar cells were all passivated by thermal SiO2 produced in tube furnaces. Although this passivation is effective, it is not yet ideal for ultra-low-cost manufacturing. In this study, we report, for the first time, the integration of black Si with a proprietary liquid-phase deposition (LPD) passivation from Natcore Technology. The Natcore LPD forms a layer of <10-nm SiO2 on top of the black Si surface in a relatively mild chemical bath at room temperature. We demonstrate black Si solar cells with LPD SiO2 with a spectrum-weighted average reflection lower than 5%, similar to the more costly thermally grown SiO2 approach. However, LPD SiO2 provides somewhat better surface-passivation quality according to the lifetime analysis by the photo-conductivity decay measurement. Moreover, black Si solar cells with LPD SiO2 passivation exhibit higher spectral response at short wavelength compared to those passivated by thermally grown SiO2. With further optimization, the combination of aqueous black Si etching and LPD could provide a pathway for low-cost, high-efficiency crystalline Si solar cells.

Yuan, H. C.; Oh, J.; Zhang, Y.; Kuznetsov, O. A.; Flood, D. J.; Branz, H. M.

2012-06-01

390

Commercial-scale demonstration of the Liquid Phase Methanol process. Technical progress report number 8, April 1--June 30, 1996  

SciTech Connect

The project involves the construction of an 80,000 gallon per day (260 tons per day (TPD)) methanol unit utilizing coal-derived synthesis gas from 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 LPMEOH{trademark} process is ideally suited for directly processing gases produced by modern-day coal gasifiers. Originally tested at a small (10 TPD), 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. At the Eastman complex, the technology is being integrated with existing coal-gasifiers. A carefully developed test plan will allow operations at Eastman to simulate electricity demand load-following in coal-based IGCC facilities. The operations will also demonstrate the enhanced stability and heat dissipation of the conversion process, its reliable on/off operation, and its ability to produce methanol as a clean liquid fuel without additional upgrading.

NONE

1996-12-31

391

Normal spectral emissivity near 680 nm at melting and in the liquid phase for 18 metallic elements  

NASA Astrophysics Data System (ADS)

Optical and thermophysical properties of pure metals at the melting point and in the liquid phase are of general interest for technological applications. This is especially true for those metals that are commonly applied. Many of these elements are used either in their pure form or as alloying components. Due to their widespread use in industry an ongoing need for new and more accurate data exists. Based on an ohmic pulse-heating apparatus, properties of conducting materials can be obtained from temperatures of about 1200 K, at which most metals are in the solid state, up to about 5000 K in the liquid state. To enable a fast and accurate temperature measurement over such a vast range, pyrometric temperature detection based on Planck's radiation law is employed. Furthermore, a microsecond-resolution ellipsometric device with no moving parts, called ?s-DOAP (Division-of-Amplitude-Photopolarimeter) as first described by Azzam [1], is applied to measure normal spectral emissivity close to the wavelength of the pyrometer (650 nm). In the present paper, measurements of normal spectral emissivity at 684.5 nm, obtained by means of the above-mentioned pulse-heating technique combined with a ?s-DOAP, are summarized for 18 metals, namely cobalt (Co), copper (Cu), gold (Au), hafnium (Hf-3%Zr), iron (Fe), iridium (Ir), molybdenum (Mo), nickel (Ni), niobium (Nb), palladium (Pd), platinum (Pt), rhenium (Re), silver (Ag), tantalum (Ta), titanium (Ti), tungsten (W), vanadium (V) and zirconium (Zr). The results are very important in order to eliminate uncertainties arising from the unknown behavior of emissivity at melting and in the liquid phase when investigating temperature-dependent thermophysical properties.

Pottlacher, G.; Boboridis, K.; Cagran, C.; Hüpf, T.; Seifter, A.; Wilthan, B.

2013-09-01

392

Synthesis of dimethyl ether and alternative fuels in the liquid phase from coal-derived synthesis gas  

SciTech Connect

As part of the DOE-sponsored contract Synthesis of Dimethyl Ether and Alternative Fuels in the Liquid Phase from Coal-Derived Syngas'' experimental evaluations of the one-step synthesis of alternative fuels were carried out. The objective of this work was to develop novel processes for converting coal-derived syngas to fuels or fuel additives. Building on a technology base acquired during the development of the Liquid Phase Methanol (LPMEOH) process, this work focused on the development of slurry reactor based processes. The experimental investigations, which involved bench-scale reactor studies, focused primarily on three areas: (1) One-step, slurry-phase syngas conversion to hydrocarbons or methanol/hydrocarbon mixtures using a mixture of methanol synthesis catalyst and methanol conversion catalyst in the same slurry reactor. (2) Slurry-phase conversion of syngas to mixed alcohols using various catalysts. (3) One-step, slurry-phase syngas conversion to mixed ethers using a mixture of mixed alcohols synthesis catalyst and dehydration catalyst in the same slurry reactor. The experimental results indicate that, of the three types of processes investigated, slurry phase conversion of syngas to mixed alcohols shows the most promise for further process development. Evaluations of various mixed alcohols catalysts show that a cesium-promoted Cu/ZnO/Al[sub 2]O[sub 3] methanol synthesis catalyst, developed in Air Products' laboratories, has the highest performance in terms of rate and selectivity for C[sub 2+]-alcohols. In fact, once-through conversion at industrially practical reaction conditions yielded a mixed alcohols product potentially suitable for direct gasoline blending. Moreover, an additional attractive aspect of this catalyst is its high selectivity for branched alcohols, potential precursors to iso-olefins for use in etherification.

Underwood, R.P.

1993-01-01

393

Factor Scores, Structure Coefficients, and Communality Coefficients  

ERIC Educational Resources Information Center

This paper presents heuristic explanations of factor scores, structure coefficients, and communality coefficients. Common misconceptions regarding these topics are clarified. In addition, (a) the regression (b) Bartlett, (c) Anderson-Rubin, and (d) Thompson methods for calculating factor scores are reviewed. Syntax necessary to execute all four…

Goodwyn, Fara

2012-01-01

394

Improved control of composition and electrical properties of liquid phase epitaxial (CdHg)Te layers  

NASA Astrophysics Data System (ADS)

Excellent compositional reproducibility, x value, and thickness are presently shown to be obtainable through the use of powdered HgTe as a source of Hg in an LPE growth sliding boat for Cd(x)Hg(1-x)Te production from Te-rich solutions at 460 C. SIMS analysis indicates that the In of the composition is 100-percent electrically active after Hg-rich annealing; the In dopant does not diffuse during the anneal treatment. Cu doping is also entirely electrically active in as-grown layers, but diffuses to the surface during annealing.

Astles, M. G.; Shaw, N.; Blackmore, G.; Hall, R. S.

1992-02-01

395

ABIOTIC TRANSFORMATIONS OF TOXIC ORGANIC CHEMICALS IN THE LIQUID PHASE AND SEDIMENTS  

EPA Science Inventory

Analyses of selected groundwater databases provide insight into the abiotic reaction conditions that occur in subsurface ecosystems. With this information it is possible to impose boundaries on the activity of selected chemical species in porous media and narrow the ranges of rea...

396

Novel approaches to low temperature transient liquid phase bonding in the In-Sn/Cu and In-Sn-Bi/Cu systems  

E-print Network

A fluxless low temperature transient liquid phase (LTTLP) bonding process was studied as a method of producing Cu/Cu joints below 125°C and 75°C using interlayer alloys from the In-Sn and In-Sn-Bi systems. Using thermodynamic ...

Fischer, David S., Ph. D. Massachusetts Institute of Technology

2008-01-01

397

Gas interaction and liquid phase reactions associated with swirl combustion and combustion instability. Final report 1 Jun 77-30 Jun 82  

Microsoft Academic Search

Three fundamental problems related to the combustion efficiency and smoother burning of an airbreathing propulsion system are studied. The first problem deals with the coupling of evaporation\\/decomposition of a liquid fuel and a novel technique of handling a slurry fuel. It has been found that at higher pressures liquid phase decomposition of a fuel is one of the primary sources

P. R. Choudhury; M. Gerstein

1982-01-01

398

Characterization of solar cells for space applications. Volume 14: Electrical characteristics of Hughes liquid phase epitaxy gallium arsenide solar cells as a function of intensity, temperature and irradiation  

NASA Technical Reports Server (NTRS)

Electrical characteristics of liquid phase epitaxy, P/N gallium aluminum arsenide solar cells are presented in graphical and tabular format as a function of solar illumination intensity and temperature. The solar cells were exposed to 1 MeV electron fluences of, respectively, 0, one hundred trillion, one quadrillion, and ten quadrillion e/sq cm.

Anspaugh, B. E.; Downing, R. G.; Miyahira, T. F.; Weiss, R. S.

1981-01-01

399

Advance Digital Imaging Process for Tungsten Alloys Liquid-Phase Sintered in Microgravity W. B Goodwin, University of Tennessee, SURF 2009 Fellow  

E-print Network

Advance Digital Imaging Process for Tungsten Alloys Liquid-Phase Sintered in Microgravity W. BW-35Ni-15Fe (wt%) alloys were LPS at 1500°C in the microgravity environment of NASA's space shuttle by the particle size in a microgravity environment. This dihedral angle was comparable to the mean angle of 47

Li, Mo

400

Pre-Service Primary Science Teachers' Understandings of the Effect of Temperature and Pressure on Solid-Liquid Phase Transition of Water  

ERIC Educational Resources Information Center

The aim of this study was to explore pre-service primary teachers' understandings of the effect of temperature and pressure on the solid-liquid phase transition of water. In the study a survey approach was used, and the sample consisted of one-hundred and three, third year pre-service primary science teachers. As a tool for data collection, a test…

Yalcin, Fatma Aggul

2012-01-01

401

The Influence of MSI (Metal-Support Interactions) and the Solvent in Liquid-Phase Reactions  

SciTech Connect

Results were repeatedly obtained that were consistent with a hypothesis proposed at the beginning of this program, i.e., due to Metal-Support Interactions (MSI), unique active sites can be created in the metal-support interfacial region to enhance activity and improve selectivity in certain types of reactions, especially those involving the hydrogenation of carbonyl and unsaturated C=C bonds. Higher turnover frequencies (TOF-molecule/s/site) and increased selectivity for C=O bond versus C=C bond hydrogenation was established in the hydrogenation reactions of: acetone, crotonaldehyde, acetophenone, phenylethanol, acetylcyclohexane, benzaldehyde, benzyl alcohol, phenylacetaldehyde and citral over Pt/TiO{sub 2} MSI catalysts. Higher rates of hydrogenation benzene, toluene and xylene could be obtained over certain supported Pt and Pd catalysts. Au/TiO{sub 2} catalysts were developed that were active for CO hydrogenation at subambient temperatures. The influence of support and metal crystallite size were established for the adsorption of H{sub 2}, CO and O{sub 2} on families of Pt and Pd catalysts.

Vannice, M. A.

2003-05-30

402

Biosorption of model pollutants in liquid phase on raw and modified rice husks  

NASA Astrophysics Data System (ADS)

We studied the application of rice husk (RH) as a biosorbent and we demonstrated that it can be employed for the treatment of dyeing wastewater streams. RH was obtained from Nile Delta (Egypt) and it was used as received, or after a chemical treatment using HNO3 or NaOH, or after conversion into activated carbon (RH-AC) using H3PO4 as activating agent. A commercial activated carbon GAC 830 provided by NORIT was also tested for comparison purposes. These materials were evaluated by adsorption of methylene blue (MB) with an initial concentration of 20 ppm in an aqueous solution at 30°C. The results showed that alkali-treated and RH-AC were the best sorbents. They got a nearly complete MB removal from water and they had better performance than GAC 830. Therefore, the use of RH for pollutant removal makes this method an environment-friendly option and an economically feasible alternative to treat industrial effluents.

Toniazzo, L.; Fierro, V.; Braghiroli, F.; Amaral, G.; Celzard, A.

2013-03-01

403

Defect structure of Cd{sub x}Hg{sub 1-x}Te films grown by liquid-phase epitaxy, studied by means of low-energy ion treatment  

SciTech Connect

Treatment with low-energy ions and measurements of electrical parameters of samples have been used to study the defect structure of Cd{sub x}Hg{sub 1-x}Te films grown by liquid-phase epitaxy. The films contain neutral defects supposedly associated with tellurium nanoinclusions. Ion treatment electrically activates these defects, with a high concentration of donor centers ({approx}10{sup 17} cm{sup -3}) created in the films. These defects decompose in {approx}10{sup 3} min of aging at room temperature. Then the properties of the material are determined by the concentration of residual donors, which is found to be very low (down to {approx}10{sup 14} cm{sup -3}) for the films under study.

Izhnin, I. I., E-mail: granat@ipm.lviv.ua; Izhnin, A. I.; Fitsych, E. I. [SRC Carat, Research Institute for Materials (Ukraine); Smirnova, N. A.; Denisov, I. A. [Giredmet State Institute for Rare Metals (Russian Federation); Pociask, M. [Rzeszow University, Institute of Physics (Poland); Mynbaev, K. D. [Russian Academy of Sciences, Ioffe Physical Technical Institute (Russian Federation)

2011-09-15

404

Modeling the gas-particle partitioning of secondary organic aerosol: the importance of liquid-liquid phase separation  

NASA Astrophysics Data System (ADS)

The partitioning of semivolatile organic compounds between the gas phase and aerosol particles is an important source of secondary organic aerosol (SOA). Gas-particle partitioning of organic and inorganic species is influenced by the physical state and water content of aerosols, and therefore ambient relative humidity (RH), as well as temperature and organic loading levels. We introduce a novel combination of the thermodynamic models AIOMFAC (for liquid mixture non-ideality) and EVAPORATION (for pure compound vapor pressures) with oxidation product information from the Master Chemical Mechanism (MCM) for the computation of gas-particle partitioning of organic compounds and water. The presence and impact of a liquid-liquid phase separation in the condensed phase is calculated as a function of variations in relative humidity, organic loading levels, and associated changes in aerosol composition. We show that a complex system of water, ammonium sulfate, and SOA from the ozonolysis of ?-pinene exhibits liquid-liquid phase separation over a wide range of relative humidities (simulated from 30% to 99% RH). Since fully coupled phase separation and gas-particle partitioning calculations are computationally expensive, several simplified model approaches are tested with regard to computational costs and accuracy of predictions compared to the benchmark calculation. It is shown that forcing a liquid one-phase aerosol with or without consideration of non-ideal mixing bears the potential for vastly incorrect partitioning predictions. Assuming an ideal mixture leads to substantial overestimation of the particulate organic mass, by more than 100% at RH values of 80% and by more than 200% at RH values of 95%. Moreover, the simplified one-phase cases stress two key points for accurate gas-particle partitioning calculations: (1) non-ideality in the condensed phase needs to be considered and (2) liquid-liquid phase separation is a consequence of considerable deviations from ideal mixing in solutions containing inorganic ions and organics that cannot be ignored. Computationally much more efficient calculations relying on the assumption of a complete organic/electrolyte phase separation below a certain RH successfully reproduce gas-particle partitioning in systems in which the average oxygen-to-carbon (O:C) ratio is lower than ~0.6, as in the case of ?-pinene SOA, and bear the potential for implementation in atmospheric chemical transport models and chemistry-climate models. A full equilibrium calculation is the method of choice for accurate offline (box model) computations, where high computational costs are acceptable. Such a calculation enables the most detailed predictions of phase compositions and provides necessary information on whether assuming a complete organic/electrolyte phase separation is a good approximation for a given aerosol system. Based on the group-contribution concept of AIOMFAC and O:C ratios as a proxy for polarity and hygroscopicity of organic mixtures, the results from the ?-pinene system are also discussed from a more general point of view.

Zuend, A.; Seinfeld, J. H.

2012-05-01

405

Metal nanoparticles in liquid phase catalysis; from recent advances to future goals.  

PubMed

Metal nanoparticles have attracted much attention over the last decade owing to their unique properties, different to their bulk counterparts, which pave the way for their application in different fields from materials science and engineering to biomedical applications. Of particular interest, the use of metal nanoparticles in catalysis has brought superior efficiency in terms of activity, selectivity and lifetime to heterogeneous catalysis. This article reviews the recent developments in the synthesis routes and the catalytic performance of metal nanoparticles depending on the solvent used for various organic and inorganic transformations. Additionally, we also discuss the prevalent complications and their possible solutions plus future prospects in the field of nanocatalysis. PMID:21833406

Zahmak?ran, Mehmet; Ozkar, Saim

2011-09-01

406

Plasmas in Multiphase Media: Bubble Enhanced Discharges in Liquids and Plasma/Liquid Phase Boundaries  

SciTech Connect

In this research project, the interaction of atmospheric pressure plasmas with multi-phase media was computationally investigated. Multi-phase media includes liquids, particles, complex materials and porous surfaces. Although this investigation addressed fundamental plasma transport and chemical processes, the outcomes directly and beneficially affected applications including biotechnology, medicine and environmental remediation (e.g., water purification). During this project, we made advances in our understanding of the interaction of atmospheric pressure plasmas in the form of dielectric barrier discharges and plasma jets with organic materials and liquids. We also made advances in our ability to use computer modeling to represent these complex processes. We determined the method that atmospheric pressure plasmas flow along solid and liquid surfaces, and through endoscopic like tubes, deliver optical and high energy ion activation energy to organic and liquid surfaces, and produce reactivity in thin liquid layers, as might cover a wound. We determined the mechanisms whereby plasmas can deliver activation energy to the inside of liquids by sustaining plasmas in bubbles. These findings are important to the advancement of new technology areas such as plasma medicine

Kushner, Mark Jay [University of Michigan] [University of Michigan

2014-07-10

407

Activity and selectivity of palladium catalysts during the liquid-phase hydrogenation of phenol. Influence of temperature and pressure  

Microsoft Academic Search

Two series of highly dispersed palladium catalysts supported on alumina have been prepared by adsorption from solution, with palladium contents varying from 0.25 to 2.0 wt %. The first series was calcined at 773 K for 4 h in air, whereas the second series was just heated at 423 K for 1 h in nitrogen, before reduction. Complete dispersion of

J. R. Gonzalez-Velasco; M. P. Gonzalez-Marcos; S. Arnaiz; J. I. Gutierrez-Ortiz; M. A. Gutierrez-Ortiz

1995-01-01

408

LIQUID PHASE SELECTIVE OXIDATION OF ETHYLBENZENE OVER ACTIVATED AL2O3 SUPPORTED V2O5 CATALYST  

EPA Science Inventory

Acetophenone, a very useful industrial chemical for fragrance and flavoring agent and a solvent for plastics and resins, is usually produced as a byproduct of phenol production from cumeme. Aluminia supported vandium oxide catalyst is now explored for the selective oxidation of e...

409

Mechanism of mutarotation in supercooled liquid phase: Studies on L-sorbose  

NASA Astrophysics Data System (ADS)

We have studied mutarotation in anhydrous supercooled L-sorbose by means of dielectric spectroscopy. The phenomenon observed in L-sorbose is much faster than in the structurally similar D-fructose. The kinetics of this process has been determined by applying 1st order kinetics model. Activation energy equal to 68 kJ/mol was obtained from temperature dependence of rate constants. To understand differences in mutarotation rate between D-fructose and L-sorbose, quantum mechanical calculations were performed to study mechanism of this phenomenon. The possible impact of water absorbed from air on the mutarotation in supercooled liquid state has been checked. It turned out that the process is probably intermolecular and the water molecules or other carbohydrate molecules assist in the proton transfer process. Finally we have shown that the rate constant can be alternatively determined from frequency of the maximum of peak, obtained by performing Fourier transform of kinetic curve.

Wlodarczyk, P.; Paluch, M.; Grzybowski, A.; Kaminski, K.; Cecotka, A.; Ziolo, J.; Markowski, J.

2012-09-01

410

Mechanism of mutarotation in supercooled liquid phase: Studies on L-sorbose.  

PubMed

We have studied mutarotation in anhydrous supercooled L-sorbose by means of dielectric spectroscopy. The phenomenon observed in L-sorbose is much faster than in the structurally similar D-fructose. The kinetics of this process has been determined by applying 1st order kinetics model. Activation energy equal to 68 kJ/mol was obtained from temperature dependence of rate constants. To understand differences in mutarotation rate between D-fructose and L-sorbose, quantum mechanical calculations were performed to study mechanism of this phenomenon. The possible impact of water absorbed from air on the mutarotation in supercooled liquid state has been checked. It turned out that the process is probably intermolecular and the water molecules or other carbohydrate molecules assist in the proton transfer process. Finally we have shown that the rate constant can be alternatively determined from frequency of the maximum of peak, obtained by performing Fourier transform of kinetic curve. PMID:23020340

Wlodarczyk, P; Paluch, M; Grzybowski, A; Kaminski, K; Cecotka, A; Ziolo, J; Markowski, J

2012-09-28

411

[Temperature dependent Raman spectra and micro-structure study of cuspidine in solid and liquid phases].  

PubMed

Cuspidine plays an important role in conventional metallurgical continuous casting mould flux. An UV laser source was used to record its ambient and high temperature Raman spectra (temperature range: 298-1 723 K) combined with a charge coupled device (CCD) detector. Both increasing and decreasing processes as well as characteristic spectra and shifts in wavenumber were observed. Micro-structure of cuspidine in liquid state is not unitary and different from that in solid state, suggesting multi clusters coexisting. Density functional theory (DFT) simulation method was applied to calculate its wavenumbers of Raman active vibrations by introducing the crystal spatial configuration model of cuspidine. Thus the experimental vibrational wavenumbers of the characteristic peaks could be assigned. This will help study physical and chemical behavior of cuspidine in continuous casting mould flux and provide an unique in-situ method under varying temperature with Raman spectroscopic technique. PMID:21322211

Niu, Yu-Jing; You, Jing-Lin; Wang, Yuan-Yuan; Wang, Zhi-Chao; Dai, Su-Juan; Xu, Jian-Lun; Zheng, Shao-Bo

2010-12-01

412

Isopiestic Investigation of the Osmotic and Activity Coefficients of {yMgCl2 + (1 - y)MgSO4}(aq) and the Osmotic Coefficients of Na2SO4.MgSO4(aq) at 298.15 K  

SciTech Connect

Isopiestic vapor pressure measurements were made for {l_brace}yMgCl{sub 2} + (1-y)MgSO{sub 4}{r_brace}(aq) solutions with MgCl{sub 2} ionic strength fractions of y = 0, 0.1997, 0.3989, 0.5992, 0.8008, and (1) at the temperature 298.15 K, using KCl(aq) as the reference standard. These measurements for the mixtures cover the ionic strength range I = 0.9794 to 9.4318 mol {center_dot} kg{sup -1}. In addition, isopiestic measurements were made with NaCl(aq) as reference standard for mixtures of {l_brace}xNa{sub 2}SO{sub 4} + (1-x)MgSO{sub 4}{r_brace}(aq) with the molality fraction x = 0.50000 that correspond to solutions of the evaporite mineral bloedite (astrakanite), Na{sub 2}Mg(SO{sub 4}){sub 2} {center_dot} 4H{sub 2}O(cr). The total molalities, m{sub T} = m(Na{sub 2}SO{sub 4}) + m(MgSO{sub 4}), range from m{sub T} = 1.4479 to 4.4312 mol {center_dot} kg{sup -1} (I = 5.0677 to 15.509 mol {center_dot} kg{sup -1}), where the uppermost concentration is the highest oversaturation molality that could be achieved by isothermal evaporation of the solvent at 298.15 K. The parameters of an extended ion-interaction (Pitzer) model for MgCl2(aq) at 298.15 K, which were required for an analysis of the {l_brace}yMgCl{sub 2} + (1-y)MgSO{sub 4}{r_brace}(aq) mixture results, were evaluated up to I = 12.025 mol {center_dot} kg{sup -1} from published isopiestic data together with the six new osmotic coefficients obtained in this study. Osmotic coefficients of {l_brace}yMgCl{sub 2} + (1-y)MgSO{sub 4}{r_brace}(aq) solutions from the present study, along with critically-assessed values from previous studies, were used to evaluate the mixing parameters of the extended ion-interaction model.

Miladinovic, J; Ninkovic, R; Todorovic, M; Rard, J A

2007-06-06

413

Picosecond dynamics of reactions in the liquid phase: studies of iodine photodissociation and development of new laser techniques  

SciTech Connect

Iodine photodissociation and recombination was studied as a model for processes common to chemical reaction in the liquid phase. Picosecond transient absorption measurements from 1000 to 295 nm were used to monitor the dynamics in a variety of solvents. Most of the atoms which undergo geminate recombination were found to do so in less than or equal to 15 ps, in agreement with the results of existing molecular dynamics simulations. Vibrational relaxation times vary from approx.15 ps near the middle of the ground state well to approx.150 ps for complete relaxation to v = 0. The prediction of strong resonant vibrational energy transfer to chlorinated methane solvents was not supported, but some evidence for this mechanism was found for alkane solvents. Current theory is unable to explain the large variation (65 to 2700 ps) of the excited A'-state lifetime in various solvents. The 10-Hz amplified, synchronously-pumped dye laser which was used in these studies is described and characterized. SERS (Stimulated Electronic Raman Scattering) and difference frequency mixing were used in the generation of the infrared and far-infrared, respectively. 54 refs., 38 figs., 3 tabs. (WRF)

Berg, M.A.

1985-09-01

414

Spin-liquid phase in a spatially anisotropic frustrated antiferromagnet: A Schwinger boson mean-field approach  

NASA Astrophysics Data System (ADS)

We explore the effect of the third-nearest neighbors on the magnetic properties of the Heisenberg model on an anisotropic triangular lattice. We obtain the phase diagram of the model using Schwinger boson mean-field theory. Competition between Néel, spiral, and collinear magnetically ordered phases is found as we vary the ratios of the nearest J1, next-nearest J2, and third-nearest J3 neighbor exchange couplings. A spin-liquid phase is stabilized between the spiral and collinear ordered states when J2/J1?1.8, for rather small J3/J1?0.1. The lowest-energy two-spinon dispersions relevant to neutron scattering experiments are analyzed and compared to semiclassical magnon dispersions finding significant differences in the spiral and collinear phases between the two approaches. The results are discussed in the context of the anisotropic triangular materials: Cs2CuCl4 and Cs2CuBr4 and layered organic materials, ?-(BEDT-TTF)2X, and Y[Pd(dmit)2]2.

Merino, Jaime; Holt, Michael; Powell, Ben J.

2014-06-01

415

3D structures of liquid-phase GaIn alloy embedded in PDMS with freeze casting.  

PubMed

Liquid phase electronic circuits are created by freeze casting gallium-indium (GaIn) alloys, such as eutectic gallium-indium (EGaIn), and encapsulating these frozen components within an elastomer. These metal alloys are liquid at room temperature, and can be cast using either injection or a vacuum to fill a PDMS mold and placing the mold in a freezer. Once solidified, a GaIn alloy segment can be manipulated, altered, or bonded to other circuit elements. A stretchable circuit can be fabricated by placing frozen components onto an elastomer substrate, which can be either patterned or flat, and sealing with an additional layer of elastomer. Circuits produced in this fashion are soft, stretchable, and can have complex 3D channel geometries. In contrast, current fabrication techniques, including needle injection, mask deposition, and microcontact printing, are limited to 2D planar designs. Additionally, freeze casting fabrication can create closed loops, multi-terminal circuits with branching features, and large area geometries. PMID:24067934

Fassler, Andrew; Majidi, Carmel

2013-11-21

416

Direct screening of ground water samples for fuel oxygenates by headspace liquid phase microextraction-gas chromatography.  

PubMed

The applicability of the headspace liquid phase microextraction and gas chromatography (HS-LPME/GC) for the expeditious and reliable screening of 68 well water samples for selected fuel oxygenates compounds, viz. methyl tertiary-butyl ether (MTBE), tertiary-amyl methyl ether (TAME), ethyl tertiary-butyl ether (ETBE) and n-butyl ethyl ether (n-BEE) has been evaluated. The method used 3 microl of 1:1 benzyl alcohol/1-octanol as extraction solvent, 20 min extraction time with stirring at 1,250 rpm, at 20 degrees C and salt addition of a mixture of 0.3 g ml(-1) sodium sulphate/0.1 g ml(-1) sodium chloride. The enrichment factors of this method were from 171 to 571. Limits of detection were in the range of 77-110 ng l(-1). The relative standard deviations (RSDs) at 0.05, 0.50 and 10.0 mg l(-1) of spiking levels were in the range of 1.28-6.80% with recoveries between 96.2 and 106.0%. Sixty-eight groundwater wells that were located near different gasoline reservoirs in eight largest cities of the Sistan and Balouchestan province were screened by the method. Eight contaminated wells were identified contained MTBE at levels between 0.3 and 1.7 mg l(-1). In all cases, other target analytes were at low concentrations or not detected. PMID:18214700

Kaykhaii, Massoud; Mirbaloochzahi, Mohammad Reza

2008-12-01

417

Revisiting Dynamics Near a Liquid-Liquid Phase Transition in Si and Ga: The Fragile-to-Strong Transition  

E-print Network

Using molecular dynamics simulations we analyze the dynamics of two atomic liquids that display a liquid-liquid phase transition (LLPT): Si described by the Stillinger-Weber potential and Ga as modeled by the modified embedded-atom model (MEAM). In particular, our objective is to investigate the extent to which the presence of a dip in the self-intermediate scattering function is a manifestation of an excess of vibrational states at low frequencies and may be associated with a fragile-to-strong transition (FTST) across the LLPT, as suggested recently. Our results do not lend support to these suggestions. Specifically, in the case of Ga we observe the appearance of an excess of vibrational states at low frequencies, even in the absence of the appearance of a dip in the self-intermediate scattering function across the LLPT. Furthermore, studying the behavior of the shear viscosities traversing the LLPTs we find that, despite the development of a dip in the self-intermediate scattering function for the case of Si and its absence in Ga, both substances are fragile in character above and below their respective LLPT temperatures.

Samuel Cajahuaringa; Maurice de Koning; Alex Antonelli

2013-11-05

418

Revisiting dynamics near a liquid-liquid phase transition in Si and Ga: The fragile-to-strong transition  

NASA Astrophysics Data System (ADS)

Using molecular dynamics simulations we analyze the dynamics of two atomic liquids that display a liquid-liquid phase transition (LLPT): Si described by the Stillinger-Weber potential and Ga as modeled by the modified embedded-atom model. In particular, our objective is to investigate the extent to which the presence of a dip in the self-intermediate scattering function is a manifestation of an excess of vibrational states at low frequencies and may be associated with a fragile-to-strong transition (FTST) across the LLPT, as suggested recently. Our results suggest a somewhat different picture. First, in the case of Ga we observe the appearance of an excess of vibrational states at low frequencies, even in the absence of the appearance of a dip in the self-intermediate scattering function across the LLPT. Second, studying the behavior of the shear viscosities traversing the LLPTs we find that both substances are fragile in character above and below their respective LLPT temperatures. Instead of a FTST in an absolute sense these findings are more in line with a view in which the LLPTs are accompanied by a transition from a more fragile to a less fragile liquid. Furthermore, we do not find this transition to correlate with the presence of a dip in the intermediate scattering function.

Cajahuaringa, Samuel; de Koning, Maurice; Antonelli, Alex

2013-12-01

419

Interface Development in Cu-Based Structures Transient Liquid Phase (TLP) Bonded with Thin Al Foil Intermediate Layers  

NASA Astrophysics Data System (ADS)

Proper bonding and assembly techniques are essential for fabrication of functional metal-based microdevices. Transient liquid phase (TLP) bonding is a promising technique for making enclosed metallic microchannel devices. In this paper, we report results of TLP bonding of Cu-based structures at temperatures between 823 K and 883 K (550 °C and 610 °C) with thin elemental Al foils as intermediate boding layers. In situ X-ray diffraction was utilized to examine the structure of Cu/Al interface in real time, resulting in a proposed sequence of structural evolution of the Cu/Al/Cu TLP bonding interface region. Three different types of bonding interface structures, the " ? 1 structure," the "eutectoid structure" ("E structure"), and the "E/ ? 1/E structure," were observed through electron microscopy, and related to the proposed sequence of interfacial structural evolution. Tensile fracture tests were conducted on TLP-bonded Cu/Al/Cu coupon assemblies. Hardness of the various phases within the bonding interface region was probed with instrumented nanoindentation. Results of mechanical testing were correlated to the structure of the bonding interface region. The present results provide an understanding of the structural evolution within the Cu/Al/Cu TLP bonding interface region, and offer guidance to future bonding of Cu-based microsystems.

Chen, Ke; Meng, Wen Jin; Eastman, J. A.

2014-08-01

420

Determination of sulfonamides in butter samples by ionic liquid magnetic bar liquid-phase microextraction high-performance liquid chromatography.  

PubMed

A novel, simple, and environmentally friendly pretreatment method, ionic liquid magnetic bar liquid-phase microextraction, was developed for the determination of sulfonamides in butter samples by high-performance liquid chromatography. The ionic liquid magnetic bar was prepared by inserting a stainless steel wire into the hollow of a hollow fiber and immobilizing ionic liquid in the micropores of the hollow fiber. In the extraction process, the ionic liquid magnetic bars were used to stir the mixture of sample and extraction solvent and enrich the sulfonamides in the mixture. After extraction, the analyte-adsorbed ionic liquid magnetic bars were readily isolated with a magnet from the extraction system. It is notable that the present method was environmentally friendly since water and only several microliters of ionic liquid were used in the whole extraction process. Several parameters affecting the extraction efficiency were investigated and optimized, including the type of ionic liquid, sample-to-extraction solvent ratio, the number of ionic liquid magnetic bars, extraction temperature, extraction time, salt concentration, stirring speed, pH of the extraction solvent, and desorption conditions. The recoveries were in the range of 73.25-103.85 % and the relative standard deviations were lower than 6.84 %. The experiment results indicated that the present method was effective for the extraction of sulfonamides in high-fat content samples. PMID:25384336

Wu, Lijie; Song, Ying; Hu, Mingzhu; Xu, Xu; Zhang, Hanqi; Yu, Aimin; Ma, Qiang; Wang, Ziming

2015-01-01

421

Evaluation of the Transient Liquid Phase (TLP) Bonding Process for Ti3Al-Based Honeycomb Core Sandwich Structure  

NASA Technical Reports Server (NTRS)

The suitability of using transient liquid phase (TLP) bonding to fabricate honeycomb core sandwich panels with Ti-14Al-21Nb (wt%) titanium aluminide (T3Al) face sheets for high-temperature hypersonic vehicle applications was evaluated. Three titanium alloy honeycomb cores and one Ti3Al alloy honeycomb core were investigated. Edgewise compression (EWC) and flatwise tension (FWT) tests on honeycomb core sandwich specimens and tensile tests of the face sheet material were conducted at temperatures ranging from room temperature to 1500 F. EWC tests indicated that the honeycomb cores and diffusion bonded joints were able to stabilize the face sheets up to and beyond the face sheet compressive yield strength for all temperatures investigated. The specimens with the T3Al honeycomb core produced the highest FWT strengths at temperatures above 1000 F. Tensile tests indicated that TLP processing conditions resulted in decreases in ductility of the Ti-14Al-21Nb face sheets. Microstructural examination showed that the side of the face sheets to which the filler metals had been applied was transformed from equiaxed alpha2 grains to coarse plates of alpha2 with intergranular Beta. Fractographic examination of the tensile specimens showed that this transformed region was dominated by brittle fracture.

Bird, R. Keith; Hoffman, Eric K.

1998-01-01

422

Saddle-like deformation in a dielectric elastomer actuator embedded with liquid-phase gallium-indium electrodes  

NASA Astrophysics Data System (ADS)

We introduce a dielectric elastomer actuator (DEA) composed of liquid-phase Gallium-Indium (GaIn) alloy electrodes embedded between layers of poly(dimethylsiloxane) (PDMS) and examine its mechanics using a specialized elastic shell theory. Residual stresses in the dielectric and sealing layers of PDMS cause the DEA to deform into a saddle-like geometry (Gaussian curvature K <0). Applying voltage ? to the liquid metal electrodes induces electrostatic pressure (Maxwell stress) on the dielectric and relieves some of the residual stress. This reduces the longitudinal bending curvature and corresponding angle of deflection ?. Treating the elastomer as an incompressible, isotropic, NeoHookean solid, we develop a theory based on the principle of minimum potential energy to predict the principal curvatures as a function of ?. Based on this theory, we predict a dependency of ? on ? that is in strong agreement with experimental measurements performed on a GaIn-PDMS composite. By accurately modeling electromechanical coupling in a soft-matter DEA, this theory can inform improvements in design and fabrication.

Wissman, J.; Finkenauer, L.; Deseri, L.; Majidi, C.

2014-10-01

423

Liquid-phase extraction coupled with metal-organic frameworks-based dispersive solid phase extraction of herbicides in peanuts.  

PubMed

Liquid-phase extraction coupled with metal-organic frameworks-based dispersive solid phase extraction was developed and applied to the extraction of pesticides in high fatty matrices. The herbicides were ultrasonically extracted from peanut using ethyl acetate as extraction solvent. The separation of the analytes from a large amount of co-extractive fat was achieved by dispersive solid-phase extraction using MIL-101(Cr) as sorbent. In this step, the analytes were adsorbed on MIL-101(Cr) and the fat remained in bulk. The herbicides were separated and determined by high-performance liquid chromatography. The experimental parameters, including type and volume of extraction solvent, ultrasonication time, volume of hexane and eluting solvent, amount of MIL-101(Cr) and dispersive solid phase extraction time, were optimized. The limits of detection for herbicides range from 0.98 to 1.9 ?g/kg. The recoveries of the herbicides are in the range of 89.5-102.7% and relative standard deviations are equal or lower than 7.0%. The proposed method is simple, effective and suitable for treatment of the samples containing high content of fat. PMID:25059170

Li, Na; Wang, Zhibing; Zhang, Liyuan; Nian, Li; Lei, Lei; Yang, Xiao; Zhang, Hanqi; Yu, Aimin

2014-10-01

424

Revisiting dynamics near a liquid-liquid phase transition in Si and Ga: The fragile-to-strong transition  

SciTech Connect

Using molecular dynamics simulations we analyze the dynamics of two atomic liquids that display a liquid-liquid phase transition (LLPT): Si described by the Stillinger-Weber potential and Ga as modeled by the modified embedded-atom model. In particular, our objective is to investigate the extent to which the presence of a dip in the self-intermediate scattering function is a manifestation of an excess of vibrational states at low frequencies and may be associated with a fragile-to-strong transition (FTST) across the LLPT, as suggested recently. Our results suggest a somewhat different picture. First, in the case of Ga we observe the appearance of an excess of vibrational states at low frequencies, even in the absence of the appearance of a dip in the self-intermediate scattering function across the LLPT. Second, studying the behavior of the shear viscosities traversing the LLPTs we find that both substances are fragile in character above and below their respective LLPT temperatures. Instead of a FTST in an absolute sense these findings are more in line with a view in which the LLPTs are accompanied by a transition from a more fragile to a less fragile liquid. Furthermore, we do not find this transition to correlate with the presence of a dip in the intermediate scattering function.

Cajahuaringa, Samuel; Koning, Maurice de, E-mail: dekoning@ifi.unicamp.br; Antonelli, Alex, E-mail: aantone@ifi.unicamp.br [Instituto de Física Gleb Wataghin, Universidade Estadual de Campinas, UNICAMP, 13083-859 Campinas, São Paulo (Brazil)] [Instituto de Física Gleb Wataghin, Universidade Estadual de Campinas, UNICAMP, 13083-859 Campinas, São Paulo (Brazil)

2013-12-14

425

Preparation of Few-Layer Bismuth Selenide by Liquid-Phase-Exfoliation and Its Optical Absorption Properties  

PubMed Central

Bismuth selenide (Bi2Se3), a new topological insulator, has attracted much attention in recent years owing to its relatively simple band structure and large bulk band gap. Compared to bulk, few-layer Bi2Se3 is recently considered as a highly promising material. Here, we use a liquid-phase exfoliation method to prepare few-layer Bi2Se3 in N-methyl-2-pyrrolidone or chitosan acetic solution. The resulted few-layer Bi2Se3 dispersion demonstrates an interesting absorption in the visible light region, which is different from bulk Bi2Se3 without any absorption in this region. The absorption spectrum of few-layer Bi2Se3 depends on its size and layer number. At the same time, the nonlinear and saturable absorption of few-layer Bi2Se3 thin film in near infrared is also characterized well and further exploited to generate laser pulses by a passive Q-switching technique. Stable Q-switched operation is achieved with a lower pump threshold of 9.3?mW at 974?nm, pulse energy of 39.8?nJ and a wide range of pulse-repetition-rate from 6.2 to 40.1?kHz. Therefore, the few-layer Bi2Se3 may excite a potential applications in laser photonics and optoelectronic devices. PMID:24762534

Sun, Liping; Lin, Zhiqin; Peng, Jian; Weng, Jian; Huang, Yizhong; Luo, Zhengqian

2014-01-01

426

Saddle-like deformation in a dielectric elastomer actuator embedded with liquid-phase gallium-indium electrodes  

SciTech Connect

We introduce a dielectric elastomer actuator (DEA) composed of liquid-phase Gallium-Indium (GaIn) alloy electrodes embedded between layers of poly(dimethylsiloxane) (PDMS) and examine its mechanics using a specialized elastic shell theory. Residual stresses in the dielectric and sealing layers of PDMS cause the DEA to deform into a saddle-like geometry (Gaussian curvature K<0). Applying voltage ? to the liquid metal electrodes induces electrostatic pressure (Maxwell stress) on the dielectric and relieves some of the residual stress. This reduces the longitudinal bending curvature and corresponding angle of deflection ?. Treating the elastomer as an incompressible, isotropic, NeoHookean solid, we develop a theory based on the principle of minimum potential energy to predict the principal curvatures as a function of ?. Based on this theory, we predict a dependency of ? on ? that is in strong agreement with experimental measurements performed on a GaIn-PDMS composite. By accurately modeling electromechanical coupling in a soft-matter DEA, this theory can inform improvements in design and fabrication.

Wissman, J., E-mail: jwissman@andrew.cmu.edu [Department of Mechanical Engineering, Carnegie Mellon University, Pittsburgh, Pennsylvania 15213 (United States); Finkenauer, L. [Department of Mechanical Engineering, Carnegie Mellon University, Pittsburgh, Pennsylvania 15213 (United States); Department of Materials Science and Engineering, Carnegie Mellon University, Pittsburgh, Pennsylvania 15213 (United States); Deseri, L. [DICAM, Department of Mechanical, Civil and Environmental Engineering, University of Trento, via Mesiano 77 38123 Trento (Italy); TMHRI-Department of Nanomedicine, The Methodist Hospital Research Institute, 6565 Fannin St., MS B-490 Houston, Texas 77030 (United States); Mechanics, Materials and Computing Center, CEE and ME-CIT, Carnegie Mellon University, Pittsburgh, Pennsylvania 15213 (United States); Majidi, C. [Department of Mechanical Engineering, Carnegie Mellon University, Pittsburgh, Pennsylvania 15213 (United States); Robotics Institute and Department of Civil and Environmental Engineering, Carnegie Mellon University, Pittsburgh, Pennsylvania 15213 (United States)

2014-10-14

427

A Phenomenological Theory for the Z2 Spin-Liquid Phase of the S=1/2 Kagome Heisenberg Antiferromagnet  

NASA Astrophysics Data System (ADS)

The spin-1/2 kagome Heisenberg antiferromagnet is one of the most promising candidate systems for a quantum spin liquid. However, the precise nature of its ground state is still being debated. Recent density-matrix renormalization group (DMRG) calculations show evidence for a possible Z2 spin-liquid phase, the effective description of which is a Z2 gauge theory [1,2]. In this work, we construct a minimal Z2 gauge Hamiltonian encapsulating the DMRG phenomenology in the S=0 sector. We generalize Misguich's Hamiltonian [3] by including dynamical visons [4]. We show that our minimal model naturally produces the diamond resonance pattern observed in DMRG. Moreover, puzzling even-odd effects in kagome cylinders are easily explained by our model. We also predict the existence of edge spinons in certain cylindrical geometries.[4pt] [1] S. Yan, D. A. Huse, and S. R. White, Science 332, 1173 (2011).[0pt] [2] S. Depenbrock, I. P. McCulloch, and U. Schollw"ock, Phys. Rev. Lett. 109, 067201 (2012).[0pt] [3] G. Misguich, D. Serban, and V. Pasquier, Phys. Rev. Lett. 89, 137202 (2002).[0pt] [4] Y. Huh, M. Punk, and S. Sachdev, Phys. Rev. B 84, 094419 (2011).

Wan, Yuan

2013-03-01

428

Optimization of pretreatment for liquid-phase deposition of SiO2 on ARTON plastic substrate  

NASA Astrophysics Data System (ADS)

This study extends our previous work on liquid-phase deposition (LPD) of dense, high-quality, silicon-dioxide (SiO2) films deposited on Si and GaAs substrates from supersaturated, hexafluorosilicic-acid aqueous at near room temperature. Pretreatment to coat the substrate surface with hydroxyl groups was found to be necessary for rapid and high-quality growth. More recent work has extended the range of LPD SiO2 to plastic. The current paper studies optimal LPD pretreatment of a plastic (ARTON) substrate. It is shown that treating ARTON plastic, first, by exposure to oxygen plasma, second, by potassium manganese (KMnO4) etching, and finally, by H2O2 etching, provides the plastic surface with rich OH-radical formation. The resulting SiO2/ARTON film is of good quality and reliability. Deposition rate is up to 659 Å/h, and the refractive index is about 1.44 with growth at 40°C. A growth mechanism for LPD-SiO2 deposition on plastic is proposed.

Huang, C. J.; Shih, W. C.

2003-06-01

429

An Experimental Study of Transient Liquid Phase Bonding of the Ternary Ag-Au-Cu System Using Differential Scanning Calorimetry  

NASA Astrophysics Data System (ADS)

An experimental approach using differential scanning calorimetry (DSC) has been applied to quantify the solid/liquid interface kinetics during the isothermal solidification stage of transient liquid phase (TLP) bonding in an Ag-Au-Cu ternary alloy solid/liquid diffusion couple. Eutectic Ag-Au-Cu foil interlayers were coupled with pure Ag base metal to study the effects of two solutes on interface motion. Experimental effects involving baseline shift and primary solidification contribute to a systematic underestimation of the fraction of liquid remaining. A temperature program has been used to quantify and correct these effects. The experimental results show a linear relationship between the interface position and the square root of the isothermal hold time. The shifting tie line composition at the interface has been shown to affect the DSC results; however, the impact on the calculated interface kinetics has been shown to be minimal in this case. This work has increased the knowledge of isothermal solidification in ternary alloy systems and developed accurate experimental methods to characterize these processes, which is valuable for designing TLP bonding schedules.

Kuntz, M. L.; Panton, B.; Wasiur-Rahman, S.; Zhou, Y.; Corbin, S. F.

2013-08-01

430

The Effects of Composition and Microstructure on the Thermal Conductivity of Liquid-Phase-Sintered W-Cu  

NASA Astrophysics Data System (ADS)

Liquid-phase sintering of high-purity, submicron, co-reduced W-15Cu powders at temperatures of 1463 to 1623 K (1190 to 1350 °C) produces W grain sizes ranging from 0.6 to 1.2 ?m while maintaining less than 2 pct porosity. Measured thermal conductivities of 185 to 221 W/(m·K) are related to the grain size and contiguity, which ranged from 0.51 to 0.62. The effects of composition and microstructure on thermal conductivity are further investigated with a model based on a computational cell that allows adjustment of the grain shape to produce selected matrix volume fractions and contiguities. The model considers porosity, the effects of transition metal impurities on the thermal conductivities of the W and Cu phases, and the rol