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1

Characterization of activated carbons using liquid phase adsorption  

Microsoft Academic Search

A modification of the Dubinin–Radushkevich pore filling model by incorporation of the repulsive contribution to the pore potential, and of bulk non-ideality, is proposed in this paper for characterization of activated carbon using liquid phase adsorption. For this purpose experiments have been performed using ethyl propionate, ethyl butyrate, and ethyl isovalerate as adsorbates and the microporous–mesoporous activated carbons Filtrasorb 400,

S. Ismadji; S. K. Bhatia

2001-01-01

2

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

Microsoft Academic Search

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

Y. KAWASE; M. MOO-YOUNG

1990-01-01

3

Liquid phase adsorption behavior of inulin-type fructan onto activated charcoal.  

PubMed

This study describes liquid phase adsorption characteristics of inulin-type fructan onto activated charcoal. Batch mode experiments were conducted to study the effects of pH, contact time, temperature and initial concentration of inulin. Nearly neutral solution (pH 6-8) was favorable to the adsorption and the equilibrium was attained after 40min with the maximum adsorption Qmax 0.182g/g (adsorbate/adsorbent) at 298K. The experimental data analysis indicated that the adsorption process fitted well with the pseudo-second-order kinetic model (R(2)=1) and Langmuir isotherms model (R(2)>0.99). Thermodynamic parameters revealed that the adsorption process was spontaneous and exothermic with a physical nature. Inulin desorption could reach 95.9% using 50% ethanol solution and activated charcoal could be reused without significant losses in adsorption capacity. These results are of practical significance for the application of activated charcoal in the production and purification of inulin-type fructan. PMID:25817664

Li, Kecheng; Liu, Song; Xing, Ronge; Yu, Huahua; Qin, Yukun; Li, Pengcheng

2015-05-20

4

Catalyst activity maintenance study for the liquid phase dimethyl ether process  

SciTech Connect

The co-production of dimethyl ether (DME) and methanol from syngas is a process of considerable commercial attractiveness. DME coproduction can double the productivity of a LPMEOH process when using coal-derived syngas. This in itself may offer chemical producers and power companies increased flexibility and more profitable operation. DME is also known as a clean burning liquid fuel; Amoco and Haldor-Topsoe have recently announced the use of DME as an alternative diesel fuel. Moreover, DME can be an interesting intermediate in the production of chemicals such as olefins and vinyl acetate. The current APCl liquid phase dimethyl ether (LPDME) process utilizes a physical mixture of a commercial methanol synthesis catalyst and a dehydration catalyst (e.g., {gamma}-alumina). While this arrangement provides a synergy that results in much higher syngas conversion per pass compared to the methanol-only process, the stability of the catalyst system suffers. The present project is aimed at reducing catalyst deactivation both by understanding the cause(s) of catalyst deactivation and by developing modified catalyst systems. This paper describes the current understanding of the deactivation mechanism.

Peng, X.D.; Toseland, B.A.; Underwood, R.P. [Air Products and Chemicals, Inc., Allentown, PA (United States)

1995-12-31

5

Liquid phase methanol synthesis catalyst  

Microsoft Academic Search

This work focuses on the investigation of the stability of catalyst activity in the liquid phase methanol synthesis process. The effects of various kinds of metfhods to inhibit the deactivation of catalyst have been experimentally examined. The activity of catalyst was stabilized without lowering of activity by a suitable hydrothermal treatment, although the activity of the untreated catalyst decreased gradually

H Mabuse; K Hagihara; T Watanabe; M Saito

1997-01-01

6

Liquid-Phase Adsorption Fundamentals.  

ERIC Educational Resources Information Center

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

Cooney, David O.

1987-01-01

7

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

SciTech Connect

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

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

1999-05-25

8

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

9

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) mol m(-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

10

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

11

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

12

Analysis of the structural interaction of electrically active heterogeneous finely dispersed systems at the interfaces between the solid and liquid phases  

NASA Astrophysics Data System (ADS)

Strong electrical forces have been revealed in electrically active heterogeneous finely dispersed systems at the interfaces between the solid and liquid phases. It has been established that these forces give rise to gradients of the potential of an internal self-electric field that can provide circulation of electric currents in the systems under investigation. It has been found that, in these systems, there arises a double electric layer that represents a new structuring phase, which is characteristic of electrically active systems only. The mechanism of formation of a double electric layer includes electrocontact interaction between the surfaces of two heterogeneous liquid and solid polar dielectrics.

Shcherbachenko, L. A.; Maksimova, N. T.; Baryshnikov, S. S.; Karnakov, V. A.; Marchuk, S. D.; Ezhova, L. I.

2011-07-01

13

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

SciTech Connect

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

Gardin, D.E.

1993-12-01

14

A pronounced catalytic activity of heteropoly compounds supported on dealuminated USY for liquid-phase esterification of acetic acid with n -butanol  

Microsoft Academic Search

12-Phosphotungstic acid and its cesium salts supported on a dealuminated ultra-stable Y zeolite were prepared, and showed the high catalytic activity in the liquid-phase esterification of acetic acid with n-butanol. The supported Cs2.5H0.5PW12O40 catalyst gave a high conversion of n-butanol of 94.6% and a selectivity for n-butyl acetate of 100%, accompanying the high water-tolerance and catalytic reusability without regeneration.

Fu-Min Zhang; Jun Wang; Chao-Shu Yuan; Xiao-Qian Ren

2005-01-01

15

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

, Methanol and Nitrogen 2.1 Introduction 32 2.2 Activity Model 33 2....3 Universal Quasi Chemical Theory (UNIQUAC Model) 35 2.4 Interaction Parameters 38 2.4.1 Universal Quasi Chemical Functional Activity...

Ghanta, Madhav

2008-01-01

16

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

17

An activity coefficient model for proteins.  

PubMed

Modeling of the properties of biochemical components is gaining increasing interest due to its potential for further application within the area of biochemical process development. Generally protein solution properties such as protein solubility are expressed through component activity coefficients which are studied here. The original UNIQUAC model is chosen for the representation of protein activity coefficients and, to the best of our knowledge, this is the first time it has been directly applied to protein solutions. Ten different protein-salt-water systems with four different proteins, serum albumin, alphacymotrypsin, beta-lactoglobulin and ovalbumin, are investigated. A root-mean-squared deviation of 0.54% is obtained for the model by comparing calculated protein activity coefficients and protein activity coefficients deduced from osmotic measurements through virial expansion. Model predictions are used to analyze the effect of salt concentrations, pH, salt types, and temperature on protein activity coefficients and also on protein solubility and demonstrate consistency with results from other references. PMID:18636445

Agena, S M; Bogle, I D; Pessoa, F L

1997-07-01

18

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

19

Approach to In-Situ Producing Reinforcing Phase Within an Active-Transient Liquid Phase Bond Seam for Aluminum Matrix Composite  

NASA Astrophysics Data System (ADS)

To optimize the braze composition design route for aluminum matrix composite, the feasibility of in situ producing reinforcing phase within the transient liquid phase bond seam matrix, by adding active melting point increaser (MPI, e.g., Ti) together with general melting point depressant (MPD, e.g., Cu) into the interlayer, was demonstrated. For SiC p /A356 composite, by comparing the wettability, joint microstructure, joint shear strength, and fracture path for the developed Al-19Cu-1Ti, Al-19Cu, Al-33Cu-1Ti, Al-33Cu (wt pct), and commercial Cu foils as interlayer, the feasibility of in situ producing reinforcing phase within the bond seam by adding Ti was demonstrated. Especially for Al-19Cu-1Ti active braze, small and dispersed ternary aluminide of Al-Si-Ti phase was obtained within the bond seam as in situ reinforcement, leading to a favorable fracture path within SiC p /A356, not along the initial interface or within the bond seam. For the formation mechanism of the in situ reinforcing phase of MPI-containing intermetallic compound within the bond seam, a model of repeating concentration-precipitation-termination-engulfment during isothermal solidification is proposed.

Zhang, Guifeng; Liao, Xianjin; Chen, Bo; Zhang, Linjie; Zhang, Jianxun

2015-03-01

20

Advances in liquid phase technology  

SciTech Connect

The liquid phase methanol (LPMEOH) process uses a slurry reactor to convert synthesis gas (primarily a mixture of hydrogen and carbon monoxide) to methanol. Through its superior heat management, the process is ultimately suitable to handle synthesis gas generated through gasification of natural gas and other materials, such as coal, petroleum coke, residual oil, wastes and other environmentally disadvantaged hydrocarbon feedstocks. Apart from production of chemical grade methanol, the process provides economic advantages in the Integrated Gasification Combined Cycle (IGCC) power generation application. Coproduction of power and methanol via the IGCC and the LPMEOH process provides opportunities for energy storage for peak-shaving of electrical demand and/or clean fuel for export. The LPMEOH technology has been developed since the 1980`s, extensively proven in a process development unit in LaPorte, Texas and elected for demonstration under The Clean Coal Technology Program. The slurry reactor being demonstrated is also suitable for other exothermic synthesis gas conversion reactions, like synthesis of Dimethyl Ether and other alcohols/oxygenates. This paper presents an overview of LPMEOH and other liquid phase technology aspects and highlights the demonstration project at Eastman Chemical Company`s coal gasification facility in Kingsport, Tennessee. Commercial aspects of the LPMEOH process are also discussed.

Jijin, P.J.A. [Air Products and Chemicals, Inc., Allentown, PA (United States)

1997-12-31

21

Application of dynamic liquid-phase microextraction and injection port derivatization combined with gas chromatography-mass spectrometry to the determination of acidic pharmaceutically active compounds in water samples.  

PubMed

A method has been established for the determination of four pharmaceutically active compounds (ibuprofen, ketoprofen, naproxen and clofibric acid) in water samples using dynamic hollow fiber liquid-phase microextraction (HF/LPME) followed by gas chromatography (GC) injection port derivatization and GC-mass spectrometric (MS) determination. Dynamic HF/LPME is a novel approach to microextraction that involves the use of a programmable syringe pump to move the liquid phases participating in the extraction so as to facilitate the process. Trimethylanilinium hydroxide (TMAH) was used as derivatization reagent for the analytes to increase their volatility and improve chromatographic separation. Parameters that affect extraction efficiency (selection of organic solvent, volume of organic solvent, agitation in the donor phase, plunger movement and extraction time) were investigated. Under optimal conditions, the proposed method provided good enrichment factors up to 251, reproducibility ranging from 3.26% to 10.61%, and good linearity from 0.2 to 50 microg/L. The limits of detection ranged between 0.01 and 0.05 microg/L (S/N=3) using selective ion monitoring. This method was applied to the determination of the four pharmaceutically active compounds in tap water and wastewater collected from a drain in the vicinity of a hospital. PMID:19345366

Zhang, Jie; Lee, Hian Kee

2009-10-30

22

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

23

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

24

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

25

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...

26

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

27

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

28

Structure analysis of turbulent liquid phase by POD and LSE techniques  

NASA Astrophysics Data System (ADS)

In this paper, vortical structures and turbulence characteristics of liquid phase in both single liquid phase and two-phase slug flow in pipes were studied. Two dimensional velocity vector fields of liquid phase were obtained by Particle image velocimetry (PIV). Two cases were considered one single phase liquid flow at 80 l/m and second slug flow by introducing gas at 60 l/m while keeping liquid flow rate same. Proper orthogonal decomposition (POD) and Linear stochastic estimation techniques were used for the extraction of coherent structures and analysis of turbulence in liquid phase for both cases. POD has successfully revealed large energy containing structures. The time dependent POD spatial mode coefficients oscillate with high frequency for high mode numbers. The energy distribution of spatial modes was also achieved. LSE has pointed out the coherent structured for both cases and the reconstructed velocity fields are in well agreement with the instantaneous velocity fields.

Munir, S.; Heikal, M. R.; Aziz, A. Rashid A.; Muthuvalu, M. S.; Siddiqui, M. I.

2014-10-01

29

Structure analysis of turbulent liquid phase by POD and LSE techniques  

SciTech Connect

In this paper, vortical structures and turbulence characteristics of liquid phase in both single liquid phase and two-phase slug flow in pipes were studied. Two dimensional velocity vector fields of liquid phase were obtained by Particle image velocimetry (PIV). Two cases were considered one single phase liquid flow at 80 l/m and second slug flow by introducing gas at 60 l/m while keeping liquid flow rate same. Proper orthogonal decomposition (POD) and Linear stochastic estimation techniques were used for the extraction of coherent structures and analysis of turbulence in liquid phase for both cases. POD has successfully revealed large energy containing structures. The time dependent POD spatial mode coefficients oscillate with high frequency for high mode numbers. The energy distribution of spatial modes was also achieved. LSE has pointed out the coherent structured for both cases and the reconstructed velocity fields are in well agreement with the instantaneous velocity fields.

Munir, S., E-mail: shahzad-munir@comsats.edu.pk; Muthuvalu, M. S.; Siddiqui, M. I. [Department of Fundamental and Applied Science, Universiti Teknologi PETRONAS, Bandar Seri Iskandar, 31750 Tronoh, Perak Darul Ridzuan (Malaysia); Heikal, M. R., E-mail: morgan.heikal@petronas.com.my; Aziz, A. Rashid A., E-mail: morgan.heikal@petronas.com.my [Department of Mechanical Engineering, Universiti Teknologi PETRONAS, Bandar Seri Iskandar, 31750 Tronoh, Perak Darul Ridzuan (Malaysia)

2014-10-24

30

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.

31

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

32

A Liquid-Phase Diffusion Experiment.  

ERIC Educational Resources Information Center

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

Nemetz, Thomas M.; Ball, David W.

1995-01-01

33

Binary Solid-Liquid Phase Equilibria  

ERIC Educational Resources Information Center

Indicates some of the information that may be obtained from a binary solid-liquid phase equilibria experiment and a method to write a computer program that will plot an ideal phase diagram to which the experimental results may be compared. (Author/CP)

Ellison, Herbert R.

1978-01-01

34

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

35

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

36

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

SciTech Connect

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

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

1995-07-01

37

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

38

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

39

Liquid phase methanol and dimethyl ether synthesis from syngas  

Microsoft Academic Search

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

Sunggyu Lee; Abhay Sardesai

2005-01-01

40

Liquid-liquid phase transition in water  

NASA Astrophysics Data System (ADS)

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

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

2014-05-01

41

The possibility of determining the activity coefficients of individual ions from acid-base titration data  

Microsoft Academic Search

A method is described for obtaining the activity coefficients of individual ions from experimental titration data. For this purpose, a general polyprotic acid-base-titration-curve equation is derived. The equation allows obtaining the dissociation equilibrium constants of the acid and the ratio of the activity coefficient of each ion to the activity coefficient of the undissociated acid directly from the titration data.

I. Jano; J. E. Hardcastle

1998-01-01

42

Paranitrophenol liquid-phase adsorption in dealuminated Y zeolite.  

PubMed

Was studied the liquid-phase paranitrophenol (PNP) dynamic adsorption in a packed bed adsorption reactor (PBAR), filled with dealuminated Y zeolite (DAY) and granulated active carbon (GAC). In addition, was measured the equilibrium maximum amount of adsorption for the system: PNP aqueous solution-DAY zeolite, at 300 K, to compare it with other adsorbents. The DAY zeolite and the GAC were characterized with adsorption methods. The DAY zeolite was, as well, characterized with: XRD, SEM and EDAX. Some of the operational parameters which characterize the performance of the PBAR were calculated. To evaluate these results, was considered the breakthrough experiment as a frontal analysis chromatographic event and were applied the DeVault and van Deemter equations. It was concluded that the reactor filled with the DAY zeolite operates more efficiently than those filled with the GAC, because of the stronger adsorbate-adsorbent interaction in the case of the DAY zeolite. PMID:18930242

Muñiz-Lopez, C; Duconge, J; Roque-Malherbe, R

2009-01-01

43

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

SciTech Connect

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

Not Available

1991-02-02

44

POSTREDUCTION TREATMENT OF LIQUID PHASE METHANOL SYNTHESIS CATALYST USING CARBON DIOXIDE  

Microsoft Academic Search

This work focuses on the investigation of the catalyst post-treatment in the liquid phase methanol synthesis process. The novel post-treatment process, using carbon dioxide, has been developed and experimentally proven to be effective not only in maintaining the initial catalytic activity over a long period of usage but also in improving the mechanical and chemical strength of the catalyst. It

Sunggyu Lee; Byung Gwon Lee; Conrad J. Kulik

1991-01-01

45

Determination of infinite dilution activity coefficients and 1-octanol\\/water partition coefficients of volatile organic pollutants  

Microsoft Academic Search

The characterization of pollutants is of growing interest as concerns about the environment increase. One parameter useful in predicting the fate of a chemical in the environment, the infinite dilution activity coefficient, has been determined here for several EPA priority pollutants in 1-octanol at 25 C using a relative gas-liquid chromatographic measurement technique. A simple correlation has been developed relating

Ginger Tse; Stanley I. Sandler

1994-01-01

46

Transfer having a coupling coefficient higher than its active material  

NASA Technical Reports Server (NTRS)

A coupling coefficient is a measure of the effectiveness with which a shape-changing material (or a device employing such a material) converts the energy in an imposed signal to useful mechanical energy. Device coupling coefficients are properties of the device and, although related to the material coupling coefficients, are generally different from them. This invention describes a class of devices wherein the apparent coupling coefficient can, in principle, approach 1.0, corresponding to perfect electromechanical energy conversion. The key feature of this class of devices is the use of destabilizing mechanical pre-loads to counter inherent stiffness. The approach is illustrated for piezoelectric and thermoelectrically actuated devices. The invention provides a way to simultaneously increase both displacement and force, distinguishing it from alternatives such as motion amplification, and allows transducer designers to achieve substantial performance gains for actuator and sensor devices.

Lesieutre, George A. (Inventor); Davis, Christopher L. (Inventor)

2001-01-01

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

Directed Liquid Phase Assembly of Highly Ordered Metallic Nanoparticle Arrays  

E-print Network

, Newark, New Jersey 07102, United States § Center for Nanophase Materials Sciences, Oak Ridge NationalDirected Liquid Phase Assembly of Highly Ordered Metallic Nanoparticle Arrays Yueying Wu, Nanyi. Rack,§, * Department of Materials Science and Engineering, The University of Tennessee, Knoxville

Kondic, Lou

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

Spontaneous liquid-liquid phase separation of water  

NASA Astrophysics Data System (ADS)

We report a molecular dynamics simulation demonstrating a fast spontaneous liquid-liquid phase separation of water and a subsequent slow crystallization to ice. It is found that supercooled water separates rapidly into low- and high-density domains so as to reduce the surface energy in the rectangular simulation cell at certain thermodynamic states. The liquid-liquid phase separation, which is about two orders of magnitude faster than the crystallization, suggests a possibility to observe this phenomenon experimentally.

Yagasaki, Takuma; Matsumoto, Masakazu; Tanaka, Hideki

2014-02-01

52

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

PubMed

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

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

2007-08-01

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

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

Microsoft Academic Search

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

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

1999-01-01

55

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

SciTech Connect

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

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

1994-11-01

56

Formation of liquid and solid products from liquid phase pyrolysis.  

PubMed

The aim of the present work was to improve the C:O ratio in biomass by preserving the lignin macrostructure of lignocellulosic feed. The intention of liquid phase pyrolysis is to liquefy biomass and prepare biomass for further upgrading steps like hydrogenation and deoxygenation. Pyrolysis was carried out in a non-aqueous liquid phase heat carrier. The process was carried out in a semi-batch reaction vessel under isothermal conditions at T=350°C, supported by a quench to stop reactions instantaneously in order to observe formation of solid intermediates. This pyrolysis system enables the observation of liquid and solid product formation. Transformation of biomass into biochar was analyzed by infrared spectroscopy and elemental analysis. Stable lignin structure throughout the whole transformation was confirmed. It was shown that the lignin frame in wood remains without substantial loss, while the major amount of carbohydrates is pyrolyzed during liquid phase pyrolysis at T=350°C. PMID:22989638

Schwaiger, N; Witek, V; Feiner, R; Pucher, H; Zahel, K; Pieber, A; Pucher, P; Ahn, E; Chernev, B; Schroettner, H; Wilhelm, P; Siebenhofer, M

2012-11-01

57

Rapid microwave-assisted liquid-phase combinatorial synthesis of 2-(arylamino)benzimidazoles.  

PubMed

An efficient, facile, and practical liquid-phase combinatorial synthesis of benzimidazoles under microwave irradiation is described. In the first step of reaction sequence, polymer-bound activated aryl fluoride was condensed with selective primary amines via an ipso-fluoro displacement reaction. Reduction of the polymer-bound nitro group followed by cyclization with isothiocyanates afforded immobilized benzimidazoles. The desired products were obtained in high yield with high purity after detaching from the soluble matrix. All reactions involved (S(N)Ar reaction, reduction, cyclization, and support cleavage) were performed completely within a few minutes under microwave irradiation. The coupling of microwave technology with liquid-phase combinatorial synthesis constitutes a novel and particularly attractive avenue for the rapid generation of structurally diverse libraries. PMID:12099854

Bendale, Pravin M; Sun, Chung-Ming

2002-01-01

58

A Review of Liquid Phase Epitaxial Grown Gallium Arsenide  

Microsoft Academic Search

Liquid phase epitaxy of gallium arsenide (LPE GaAs) has been investigated intensively from the late 1960's to the present and has now a special place in the manufacture of wide band, compound semiconductor radiation detectors. Although this particular process appears to have gained prominence in the last three decades, it is interesting to note that its origins reach back to

D. Alexiev; D. A. Prokopovich; S. Thomson; L. Mo; A. B. Rosenfeld; M. Reinhard

2004-01-01

59

Analysis of particle growth by coalescence during liquid phase sintering  

Microsoft Academic Search

A statistical approach has been applied to particle coarsening during liquid phase sintering assuming direct particle coalescence as basic growth mechanism instead of Ostwald ripening. The coalescence process controlled by diffusion through the melt results in an increase of the average particle size proportional to the cube root of sintering time. After a short initial sintering interval the particle size

S. Takajo; W. A. Kaysser; G. Petzow

1984-01-01

60

High purity liquid phase epitaxial gallium arsenide nuclear radiation detector  

Microsoft Academic Search

Surface barrier radiation detector made from high purity liquid phase epitaxial gallium arsenide wafers have been operated as X- and gamma-ray detectors at various operating temperatures. Low energy isotopes are resolved including 241Am at 40°C and the higher gamma energies of 235U at -80°C.

Dimitri Alexiev; K. S. A. Butcher

1992-01-01

61

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

PubMed

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

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

2014-02-01

62

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

SciTech Connect

The Liquid Phase Methanol (LPMEOH) Demonstration Project at Kingsport, Tennessee, is a $213.7 million cooperative agreement between the U.S. Department of Energy (DOE) and Air Products Liquid Phase Conversion Company, L.P. (the Partnership). Ak Products and Chemicals, Inc. (Air Products) and Eastman Chemical Company (Eastman) formed the Partnership to execute the Demonstration Project. The LPMEOITM Process Demonstration Unit was built at a site located at the Eastman complex in Kingsport. During this reporting period, DOE accepted the recommendation to continue with dimethyl ether (DME) design verification testing (DVT). DME design verification testing studies show the liquid phase DME (LPDME) process will have a significant economic advantage for the coproduction of DME for local markets. An LPDME catalyst system with reasonable long-term activity and stzibility is being developed. Planning for a proof-of-concept test run at the LaPorte Alternative Fuels Development Unit (AFDU) was recommended. DOE issued a letter dated 31 July 1997 accepting the recommendation to continue design verification testing. In order to allow for scale-up of the manufacturing technique for the dehydration catalyst from the pilot plant to the commercial scale, the time required to produce the catalyst to the AFDU has slipped. The new estimated delivery date is 01 June 1998.

None

1997-09-30

63

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

64

A SINGLE-STAGE, LIQUID-PHASE DIMETHYL ETHER SYNTHESIS PROCESS FROM SYNGAS II. COMPARISON OF PER-PASS SYNGAS CONVERSION, REACTOR PRODUCTIVITY AND HYDROGENATION EXTENT  

Microsoft Academic Search

In part I of this series on the development of a single-stage, liquid-phase dimethyl ether (DME) synthesis process from syngas, the process feasibility and the process variable effects on the dual catalyst activity were discussed. This part focuses on the comparison of the single-stage reactor productivity of liquid phase methanol synthesis to that of the co-production of methanol and DME.

Sunggyu Lee; Makarand R. Gogate; Conrad J. Kulik

1991-01-01

65

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

Microsoft Academic Search

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

Natalia Semagina

2009-01-01

66

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

SciTech Connect

Activity coefficient derivatives with respect to molality are presented for the Scatchard Neutral Electrolyte description of a ternary common-ion electrolyte system. These quantities are needed for the calculation of 'diffusion Onsager coefficients' and in turn for tests of the Onsager Reciprocal Relations in diffusion. The usually-omitted b{sub 23} term is included. The direct SNE binary approximations and a further approximation are discussed. Binary evaluation strategies other than constant ionic strength are considered.

Miller, D G

2007-05-16

67

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

68

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

NASA Astrophysics Data System (ADS)

A critical evaluation of the mean acivity and osmotic coefficients in aqueous solutions of thirty-five uni-bivalent electrolytes at 298.15 K is presented. The systems which have been treated are ammonium orthophosphate, guanadinium carbonate, 1,2-ethane disulfonic acid, m-benzene disulfonic acid, ammonium decahydroborate, and the unibivalent compounds of lithium, sodium, potasium, rubidium, and cesium. Osmotic coefficients were calculated from direct vapor pressure measurements, from isopiestic measurements and from freezing-point depression measurements. Activity coefficients were calculated from electromotive force measurements on galvanic cells without transference and from diffusion measurements. Given are empirical coefficients for three different correlating equations, obtained by a weighted least squares fit to the experimental data, and tables consisting of the activity coefficients of the compounds, the osmotic coefficients and activity of water, and the excess Gibbs energy of the solution as functions of the molality for each electrolyte system. The literature coverage is through the computerized version of Chemical Abstracts of September 1979.

Goldberg, R. N.

1981-07-01

69

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

70

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

NASA Astrophysics Data System (ADS)

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.

Patsahan, O.

2014-06-01

71

Solid–Liquid Phase Change Driven by Internal Heat Generation  

SciTech Connect

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

John Crepeau; Ali s. Siahpush

2012-07-01

72

On Asymmetric Diffusional Solidification During Transient Liquid Phase Bonding  

NASA Astrophysics Data System (ADS)

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

Ghobadi Bigvand, A.; Ojo, Olanrewaju A.

2014-04-01

73

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 with the introduction of a new temperature dependence parameterisation. The improved temperature dependence parameterisation is derived from classical thermodynamic theory by describing effects from changes in molar enthalpy and heat capacity of a multicomponent 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 25% in comparison to the previous model version. The new parameterisation of AIOMFAC agrees well with a large number of experimental datasets and enables the calculation of activity coefficients of 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.

2014-06-01

74

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

75

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

76

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

77

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

78

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...

79

Catalytic performances of heteropoly compounds supported on dealuminated ultra-stable Y zeolite for liquid-phase esterification  

Microsoft Academic Search

A series of catalysts of 12-Phosphotungstic acid (PW) and its cesium salts immobilized on dealuminated ultra-stable Y zeolite\\u000a (DUSY) were prepared. Their specific surface area and acid strength were characterized, and their catalytic activity, selectivity\\u000a and stability were evaluated in the liquid-phase esterification of acetic acid with n-butanol. It was found that the catalytic activity could be improved remarkably by

Fumin Zhang; Jun Wang; Chaoshu Yuan; Xiaoqian Ren

2006-01-01

80

Topological and spin-liquid phases in strongly correlated iridates  

NASA Astrophysics Data System (ADS)

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

Kim, Yong Baek

2012-02-01

81

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

82

First-Order Liquid-Liquid Phase Transition in Cerium  

NASA Astrophysics Data System (ADS)

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

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

2013-03-01

83

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

84

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

NASA Astrophysics Data System (ADS)

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

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

85

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

SciTech Connect

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

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

2013-10-15

86

Transmission electron microscopy of liquid phase densified SiC  

SciTech Connect

Transmission electron microscopy was used to characterize microstructures of SiC densified using a transient liquid phase (resulting from the reaction of Al{sub 2}O{sub 3} with Al{sub 4}C{sub 3}) by hot pressing at 1875 {degree}C for 10 min in N{sub 2}. High resolution electron microscopy showed that the SiC grain boundaries were free of glassy phases, suggesting that all liquid phases crystallized upon cooling. Phases that might be expected due to reactive sintering (i.e., AlN, Al{sub 2}OC, Al{sub 2}O{sub 3}, Al{sub 4}O{sub 4}C, Al{sub 3}O{sub 3}N, or solid solutions of SiC, AlN, and Al{sub 2}OC) were not observed. However, significant Al, Si, O, and C concentrations were found at all triple junctions of these rapidly densified ceramics.

Carpenter, R.W.; Braue, W. (Center for Solid State Science, the Arizona State University, Tempe, Arizona (USA)); Cutler, R.A. (Ceramatec, Inc., 2425 South 900 West, Salt Lake City, Utah (USA))

1991-09-01

87

Activity coefficients for NH 4Cl in ethanol–water mixed solvents by electromotive force measurements  

Microsoft Academic Search

Pitzer ion-interaction model and electromotive force (emf) data of a galvanic cell without liquid junction were used for the determination of activity coefficients of NH4Cl in different ethanol–water mixed solvents at 25 °C. The used galvanic cell is schematically represented by: Ag?AgCl?NH4Cl (m), H2O (100-w%), EtOH (w%)?NH4+ (ISE), in which ISE stands for ion-selective electrode and w for the mass

Farzad Deyhimi; Bahram Ghalami-Choobar; Rahman Salamat-Ahangari

2005-01-01

88

A single-stage synthesis of dimethyl ether in liquid phase  

SciTech Connect

A novel, single-stage process for the synthesis of dimethyl ether (DME) has been developed using CO rich syngas in the liquid phase (LPDME). This process utilizes a three-phase, mechanically agitated slurry reactor and makes use of a dual catalyst system consisting of Cu/ZnO/Al{sub 2}O{sub 3} as the methanol synthesis catalyst and {gamma}-Al{sub 2}O{sub 3} for the subsequent conversion to DME. The catalyst is slurried in an inert mineral oil which facilitates effective heat removal. The process involves the synthesis of methanol as an inter-mediate in the production of DME. In doing so, there is a reduction of the chemical equilibrium limitations previously encountered in methanol synthesis alone. As a result, enhanced catalyst activity, per-pass conversion and reactor productivity over methanol synthesis is observed. The process excels over its liquid phase methanol counterpart (LPMeOH{trademark}) in many areas. Specifically, a increase in reactor productivity as high as 95% is attained in the production of DME over LPMeOH{trademark}. Also, a 60% increase in syngas conversion is attained over the production of methanol alone. Experimental studies compare reactor productivities for methanol vs. DME synthesis for several slurry ratios. Also, the effect of temperature and pressure on synthesis rates for methanol and DME are also examined.

Tartamella, T.L.; Lee, S. [Univ. of Akron, OH (United States); Kulik, C.J. [Electric Power Research Inst., Palo Alto, CA (United States)

1994-12-31

89

Morphologies of aerosol particles consisting of two liquid phases  

NASA Astrophysics Data System (ADS)

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

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

2013-04-01

90

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

Microsoft Academic Search

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

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

1991-01-01

91

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

92

Transient liquid-phase bonding of ODS steels  

NASA Astrophysics Data System (ADS)

The use of transient liquid-phase bonding of 9CrODS steels using Fe-3B-2Si-0.5C filler was investigated for bonding temperature of 1180 °C and hold times of 0.5-4.0 h. The sequential process, consisting of isothermal melting, solidification and homogenization, was confirmed for bonding the 9CrODS steel. The precipitation of chromium boride found in 19CrODS steel is avoided in 9CrODS steel due to the lower Cr content. Silicon tends to be slightly enriched inside the bonding zone. Agglomeration and coarsening of Y 2O 3 particles in 9CrODS steel lead to softening inside the bonding zone formed by incipient melting of the foil bonding alloy, and in a diffusion affected zone (DAZ) adjacent to the bonding zone.

Noto, H.; Ukai, S.; Hayashi, S.

2011-10-01

93

Liquid-phase-deposited barium titanate thin films on silicon  

NASA Astrophysics Data System (ADS)

Using a mixture of hexafluorotitanic acid, barium nitrate and boric acid, high refractive index (1.54) barium titanate films can be deposited on silicon substrates. The deposited barium titanate films have featureless surfaces. The deposition temperature is near room temperature (80°C). However, there are many fluorine and silicon incorporations in the films. The refractive index of the as-deposited film is 1.54. By current-voltage measurement, the leakage current of the as-deposited film with a thickness of 1000 Å is about 9.48×10-7 A cm-2 at the electrical field intensity of 0.3 MV cm-1. By capacitance-voltage measurement, the effective oxide charge of the liquid-phase-deposited barium titanate film is 3.06×1011 cm-2 and the static dielectric constant is about 22.

Lee, Ming-Kwei; Liao, Hsin-Chih; Tung, Kuan-Wen; Shih, Chung-Min; Shih, Tsung-Hsiang

2002-01-01

94

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

95

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

96

Liquid phase stability under an extreme temperature gradient.  

PubMed

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

Liang, Zhi; Sasikumar, Kiran; Keblinski, Pawel

2013-11-27

97

High temperature creep of SiC densified using a transient liquid phase  

SciTech Connect

Silicon carbide-based ceramics can be rapidly densified above approximately 1850 {degree}C due to a transient liquid phase resulting from the reaction between alumina and aluminum oxycarbides. The resulting ceramics are fine-grained, dense, and exhibit high strength at room temperature. SiC hot pressed at 1875 {degree}C for 10 min in Ar was subjected to creep deformation in bending at elevated temperatures between 1500 and 1650 {degree}C in Ar. Creep was thermally activated with an activation energy of 743 kJ/mol. Creep rates at 1575 {degree}C were between 10{sup {minus}9}/s and 10{sup {minus}7}/s at an applied stress between 38 and 200 MPa, respectively, resulting in a stress exponent of {approx}1.7.

Jou, Z.C.; Virkar, A.V. (Department of Materials Science and Engineering, The University of Utah, Salt Lake City, Utah (USA)); Cutler, R.A. (Ceramatec, Inc., 2425 South 900 West, Salt Lake City, Utah (USA))

1991-09-01

98

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

SciTech Connect

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

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

1995-02-01

99

Liquid-phase chemical sensing using lateral mode resonant cantilevers.  

PubMed

Liquid-phase operation of resonant cantilevers vibrating in an out-of-plane flexural mode has to date been limited by the considerable fluid damping and the resulting low quality factors (Q factors). To reduce fluid damping in liquids and to improve the detection limit for liquid-phase sensing applications, resonant cantilever transducers vibrating in their in-plane rather than their out-of-plane flexural resonant mode have been fabricated and shown to have Q factors up to 67 in water (up to 4300 in air). In the present work, resonant cantilevers, thermally excited in an in-plane flexural mode, are investigated and applied as sensors for volatile organic compounds in water. The cantilevers are fabricated using a complementary metal oxide semiconductor (CMOS) compatible fabrication process based on bulk micromachining. The devices were coated with chemically sensitive polymers allowing for analyte sorption into the polymer. Poly(isobutylene) (PIB) and poly(ethylene-co-propylene) (EPCO) were investigated as sensitive layers with seven different analytes screened with PIB and 12 analytes tested with EPCO. Analyte concentrations in the range of 1-100 ppm have been measured in the present experiments, and detection limits in the parts per billion concentration range have been estimated for the polymer-coated cantilevers exposed to volatile organics in water. These results demonstrate significantly improved sensing properties in liquids and indicate the potential of cantilever-type mass-sensitive chemical sensors operating in their in-plane rather than out-of-plane flexural modes. PMID:20715842

Beardslee, L A; Demirci, K S; Luzinova, Y; Mizaikoff, B; Heinrich, S M; Josse, F; Brand, O

2010-09-15

100

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

101

Propene and 1-Octene Hydroformylation with Silica-Supported, Ionic Liquid-Phase (SILP) Rh-Phosphine Catalysts in Continuous Fixed-Bed Mode  

Microsoft Academic Search

Supported ionic liquid-phase (SILP) catalysts were made by immobilizing Rh-monophosphine complexes of bis(m-phenylguanidinium)phenylphosphine 1 and NORBOS 2 ligands in 1-n-butyl-3-methylimidazolium hexafluorophosphate, [BMIM][PF6], on a silica support. The catalysts were active in continuous gas- and liquid-phase hydroformylation of propene and 1-octene, exhibiting TOFs up to 88 h-1 for SILP Rh-2 catalysts, while only low selectivities up to 74% n-aldehyde (n\\/iso ratio

Anders Riisager; K. Michael Eriksen; Peter Wasserscheid; Rasmus Fehrmann

2003-01-01

102

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

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

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

NASA Astrophysics Data System (ADS)

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

Koral, Kenneth F.; Dewaraja, Yuni

1999-02-01

106

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

NASA Astrophysics Data System (ADS)

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

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

2012-12-01

107

A reanalysis of the kinetics of neck growth during liquid phase sintering  

Microsoft Academic Search

During liquid phase sintering, solid particles make contact and can subsequently coalesce into one particle. This coalescence phenomena can affect the type of microstructure formed and its subsequent coarsening behavior during liquid phase sintering. The mechanism of particle coalescence is assumed to be the liquid state analog of the evaporation-condensation mechanism of sintering. In this work, a detailed study of

T. H. Courtney

1977-01-01

108

An analysis for estimating the probability of particle coalescence in liquid phase sintered systems  

Microsoft Academic Search

During liquid phase sintering solid particles move about within the liquid and make contact with each other. Microstructural examination of liquid phase sintered alloys clearly indicates that some of these contacts lead to particle coalescence even in systems in which wetting of the solid by the liquid is presumed to occur. Under these circumstances, the grain boundary formed by the

T. H. Courtney; J. K. Lee

1980-01-01

109

Laser-induced separation of hydrogen isotopes in the liquid phase  

Microsoft Academic Search

A process for separating hydrogen isotopes which comprises (A) forming a liquid phase of hydrogen-bearing feedstock compound at a temperature at which the spectral features of the feedstock compound are narrow enough or the absorption edges sharp enough to permit spectral features corresponding to the different hydrogen isotopes to be separated to be distinguished, (B) irradiating the liquid phase at

W. Beattie; S. Freund; R. Holland; W. Maier

1980-01-01

110

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.

111

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

E-print Network

the effect of process variables during the transient liquid phase bonding of Inconel 625 and 718 superalloys in the final joint microstructures. Introduction Inconel 625 and 718 superalloys are extensively used in aero welding [1], transient liquid phase bonding evolved as an effective way to join these superalloys. TLP

Medraj, Mamoun

112

Glass and liquid phase diagram of a polyamorphic monatomic system.  

PubMed

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

Reisman, Shaina; Giovambattista, Nicolas

2013-02-14

113

Glass and liquid phase diagram of a polyamorphic monatomic system  

NASA Astrophysics Data System (ADS)

We perform out-of-equilibrium molecular dynamics (MD) simulations of a monatomic system with Fermi-Jagla (FJ) pair potential interactions. This model system exhibits polyamorphism both in the liquid and glass state. The two liquids, low-density (LDL) and high-density liquid (HDL), are accessible in equilibrium MD simulations and can form two glasses, low-density (LDA) and high-density amorphous (HDA) solid, upon isobaric cooling. The FJ model exhibits many of the anomalous properties observed in water and other polyamorphic liquids and thus, it is an excellent model system to explore qualitatively the thermodynamic properties of such substances. The liquid phase behavior of the FJ model system has been previously characterized. In this work, we focus on the glass behavior of the FJ system. Specifically, we perform systematic isothermal compression and decompression simulations of LDA and HDA at different temperatures and determine "phase diagrams" for the glass state; these phase diagrams varying with the compression/decompression rate used. We obtain the LDA-to-HDA and HDA-to-LDA transition pressure loci, PLDA-HDA(T) and PHDA-LDA(T), respectively. In addition, the compression-induced amorphization line, at which the low-pressure crystal (LPC) transforms to HDA, PLPC-HDA(T), is determined. As originally proposed by Poole et al. [Phys. Rev. E 48, 4605 (1993)], 10.1103/PhysRevE.48.4605 simulations suggest that the PLDA-HDA(T) and PHDA-LDA(T) loci are extensions of the LDL-to-HDL and HDL-to-LDL spinodal lines into the glass domain. Interestingly, our simulations indicate that the PLPC-HDA(T) locus is an extension, into the glass domain, of the LPC metastability limit relative to the liquid. We discuss the effects of compression/decompression rates on the behavior of the PLDA-HDA(T), PHDA-LDA(T), PLPC-HDA(T) loci. The competition between glass polyamorphism and crystallization is also addressed. At our "fast rate," crystallization can be partially suppressed and the glass phase diagram can be related directly with the liquid phase diagram. However, at our "slow rate," crystallization cannot be prevented at intermediate temperatures, within the glass region. In these cases, multiple crystal-crystal transformations are found upon compression/decompression (polymorphism).

Reisman, Shaina; Giovambattista, Nicolas

2013-02-01

114

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

115

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

116

Hyperdoping silicon with selenium: solid vs. liquid phase epitaxy  

NASA Astrophysics Data System (ADS)

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.

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

2015-02-01

117

Liquid phase deposition synthesis of hexagonal molybdenum trioxide thin films  

SciTech Connect

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

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

2009-09-15

118

Thermal conductivity of alternative refrigerants in the liquid phase  

NASA Astrophysics Data System (ADS)

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

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

1996-05-01

119

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

120

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

PubMed

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

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

2002-05-01

121

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

122

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

123

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

PubMed Central

Hollow fiber liquid phase micro-extraction (LPME) of linear alkylbenzene sulfonates (LAS) from aqueous samples was studied. Ion pair extraction of C10, C11, C12 and C13 homologues was facilitated with trihexylamine as ion-pairing agent, using di-n-hexylether as solvent for the supported liquid membrane (SLM). Effects of extraction time, acceptor buffer concentration, stirring speed, sample volume, NaCl and humic acids were studied. At 10–50 ?g L?1 linear R2-coefficients were 0.99 for C10 and C11 and 0.96 for C12. RSD was typically ?15%. Three observations were especially made. Firstly, LPME for these analytes was unusually slow with maximum enrichment observed after 15–24 h (depending on sample volume). Secondly, the enrichment depended on LAS sample concentration with 35–150 times enrichment below ?150 ?g L?1 and 1850–4400 times enrichment at 1 mg L?1. Thirdly, lower homologues were enriched more than higher homologues at low sample concentrations, with reversed conditions at higher concentrations. These observations may be due to the fact that LAS and the amine counter ion themselves influence the mass transfer at the water-SLM interface. The observations on LPME of LAS may aid in LPME application to other compounds with surfactant properties or in surfactant enhanced membrane extraction of other compounds. PMID:24957870

Larsson, Niklas; Otrembska, Paulina; Villar, Mercedes; Jönsson, Jan Åke

2011-01-01

124

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

125

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

NASA Astrophysics Data System (ADS)

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

Yourdkhani, Amin

126

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

127

Activity coefficients at infinite dilution of organic solutes in the ionic liquid 1-ethyl-3-methylimidazolium methanesulfonate  

Microsoft Academic Search

Infinite dilution activity coefficients ?1? and gas–liquid partition coefficients KL of 30 selected hydrocarbons, alcohols, ketones, ethers, esters, haloalkanes, nitrogen- and sulphur-containing compounds in the ionic liquid (IL) 1-ethyl-3-methylimidazolium methanesulfonate [EMIM][MeSO3] were determined by gas–liquid chromatography at five temperatures in the range from 318.15 to 353.15K. Relative contribution of adsorption at gas–liquid interphase to the overall solute retention, as examined

Aleš Blahut; Marek Sobota; Vladimír Dohnal; Pavel Vrbka

2010-01-01

128

Adjustment of activity coefficients as a function of changes in temperature, using the specific interaction theory  

NASA Astrophysics Data System (ADS)

The aim of this work is to propose and to check approximations to calculate from only a few experimental measurements, ionic strength I and temperature T, influences on Gibbs' energy G, formal redox potential E and standard equilibrium constant K. Series expansions vs. T are first used: S and C(sub p)/2T (sup o) are typically the first- and second-order terms in -G. In the same way, -Delta H and T(exp 2) Delta C(sub p)/2 are the first- and second-order terms ofR ln K expansions vs. 1/T. This type of approximation is discussed for E of the M(4+)/M(3+), MO2(2+)/MO2(+) and MO2(CO3)3(4+)/MO2(CO3)3(4-)/MO2(CO3)3(4-) couples (M equivalent to U or Pu) measured from 5 to 70 C, for the standard Delta G of some solid U compounds, calculated from 17 to 117 C, and for Delta C(sub p), Delta G and log K of the CO2(aq)/HCO3(-) equilibrium from 0 to 150 C. Excess functions X(sup ex) are then calculated from activity coefficients gamma: enthalpy H or heat capacity C(sub p) adjustment as a function of I changes is needed only when the gamma adjustment as a function of T changes is needed. The variations in the specific interaction theory coefficient epsilon with T are small and roughly linear for the above redox equilibria and for the mean gamma of chloride electrolytes: first-order expansion seems enough to deduce epsilon, and then the excess functions G(sup ex), S(sup ex) and H(sup ex), in this T range; but second-order expansion is more consistent for estimation of C(sub p)(sup ex).

Giffaut, Eric; Vitorge, Pierre; Capdevila, Helene

1994-10-01

129

GaAs pyramidal microtips grown by selective liquid-phase epitaxy  

NASA Astrophysics Data System (ADS)

We present a simple selective liquid-phase epitaxial growth of GaAs pyramidal microtips for integrated scanning near-field optical microscopy sensors. The technique comprises oxide mask formation, openings creation, and liquid-phase epitaxial growth. SiO 2 mask is firstly formed on (0 0 1) GaAs substrate by liquid-phase deposition, periodic square windows are then created in the mask using photolithography and wet etching, and GaAs microtips are finally grown on the opening areas by liquid-phase epitaxy. Scanning electron microscopy images show high quality of the pyramidal microtips bounded by four equal {1 1 1} sidewalls. This differs greatly from those drawn from selective metalorganic chemical vapor deposition.

Lizhong, Hu; Hongzhi, Zhang; Zhijun, Wang; Jie, Sun; Yu, Zhao; Xiuping, Liang

2004-10-01

130

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

NASA Astrophysics Data System (ADS)

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

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

2013-10-01

131

Gapless Spin-Liquid Phase in an Extended Spin 1/2 Triangular Heisenberg Model  

NASA Astrophysics Data System (ADS)

We numerically study the Heisenberg models on triangular lattices by extending it from the simplest equilateral lattice with only the nearest-neighbor exchange interaction. We show that, by including an additional weak next-nearest-neighbor interaction, a quantum spin-liquid phase is stabilized against the antiferromagnetic order. The spin gap (triplet excitation gap) and spin correlation at long distances decay algebraically with increasing system size at the critical point between the antiferromagnetic phase and the spin-liquid phase. This algebraic behavior continues in the spin-liquid phase as well, indicating the presence of an unconventional critical (algebraic spin-liquid) phase characterized by the dynamical and anomalous critical exponents z + ? ˜ 1. Unusually small triplet and singlet excitation energies found in extended points of the Brillouin zone impose constraints on this algebraic spin liquid.

Kaneko, Ryui; Morita, Satoshi; Imada, Masatoshi

2014-09-01

132

Dynamic changes of integrated backscatter, attenuation coefficient and bubble activities during high-intensity focused ultrasound (HIFU) treatment.  

PubMed

This paper simultaneously investigated the transient characteristics of integrated backscatter (IBS), attenuation coefficient and bubble activities as time traces before, during and after HIFU treatment, with different HIFU parameters (acoustic power and duty cycle) in both transparent tissue-mimicking phantoms and freshly excised bovine livers. These dynamic changes of acoustic parameters and bubble activities were correlated with the visualization of lesion development selected from photos, conventional B-mode ultrasound images and differential IBS images over the whole procedure of HIFU treatment. Two-dimensional radiofrequency (RF) data were acquired by a modified diagnostic ultrasound scanner to estimate the changes of mean IBS and attenuation coefficient averaged in the lesion region, and to construct the differential IBS images and B-mode ultrasound images simultaneously. Bubble activities over the whole procedure of HIFU treatment were investigated by the passive cavitation detection (PCD) method and the changes in subharmonic and broadband noise were correlated with the transient characteristics of IBS and attenuation coefficient. When HIFU was switched on, IBS and attenuation coefficient increased with the appearance of bubble clouds in the B-mode and differential IBS image. At the same time, the level of subharmonic and broadband noise rose abruptly. Then, there was an initial decrease in the attenuation coefficient, followed by an increase when at lower HIFU power. As the lesion appeared, IBS and attenuation coefficient both increased rapidly to a value twice that of normal. Then the changes in IBS and attenuation coefficient showed more complex patterns, but still showed a slower trend of increases with lesion development. Violent bubble activities were visible in the gel and were evident as strongly echogenic regions in the differential IBS images and B-mode images simultaneously. This was detected by a dramatic high level of subharmonic and broadband noise at the same time. These bubble activities caused fluctuations in IBS and attenuation coefficient during HIFU treatment. After HIFU, IBS and attenuation coefficient decreased gradually accompanied by the fadeout of bright hyperechoic spot in the B-mode and differential IBS image, but were still higher than normal when they were stable. The increases of IBS and attenuation coefficient were greater when using higher acoustic power or a higher duty cycle of the therapeutic emission. These experiments indicated that the bubble activities had the dominant effects on the transient characteristics of IBS and attenuation. This should be taken into consideration when using the dynamic acoustic-property changes for the potentially real-time monitoring imaging of HIFU treatment. PMID:19716225

Zhang, Siyuan; Wan, Mingxi; Zhong, Hui; Xu, Cheng; Liao, Zhenzhong; Liu, Huanqing; Wang, Supin

2009-11-01

133

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

134

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

DOEpatents

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

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

1985-11-12

135

An analysis for estimating the probability of particle coalescence in liquid phase sintered systems  

Microsoft Academic Search

During liquid phase sintering solid particles move about within the liquid and make contact with each other. Microstructural\\u000a examination of liquid phase sintered alloys clearly indicates that some of these contacts lead to particle coalescence even\\u000a in systems in which wetting of the solid by the liquid is presumed to occur. Under these circumstances, the grain boundary\\u000a formed by the

T. H. Courtney; J. K. Lee

1980-01-01

136

A reanalysis of the kinetics of neck growth during liquid phase sintering  

Microsoft Academic Search

During liquid phase sintering, solid particles make contact and can subsequently coalesce into one particle. This coalescence\\u000a phenomena can affect the type of microstructure formed and its subsequent coarsening behavior during liquid phase sintering.\\u000a The mechanism of particle coalescence is assumed to be the liquid state analog of the evaporation-condensation mechanism of\\u000a sintering. In this work, a detailed study of

T. H. Courtney

1977-01-01

137

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

DOEpatents

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

Raj, R.; Baik, S.

1985-11-12

138

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 346-353 K. 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

139

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

SciTech Connect

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

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

1999-04-01

140

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

141

Infinite dilution activity coefficients and solubilities of biphenyl in octadecane and mineral oil  

SciTech Connect

Biphenyl is a very stable and highly toxic chemical, used extensively as a heat transfer medium. It is solid at ambient temperature, with a relatively high vapor pressure. Therefore, air treatment is required to reduce the biphenyl concentration to safe values in processing areas where biphenyl is exposed directly to the atmosphere. an absorption process has been developed to remove this contaminant from air. The absorption solvent has to be a nonpolar compound with a very low vapor pressure so as to avoid further contamination of the air. A suitable choice for this application is a mineral oil. The absorption cycle is completed with a crystallization stage to partially remove the biphenyl from the solution and to recover the oil. Infinite dilution activity coefficients and solubilities of biphenyl in octadecane and in mineral oil are reported. The mineral oil is characterized by means of its molecular weight, effective molar volume, and solubility parameter. Flory`s combinatorial model with a regular solution residual term is used to correlate the experimental results.

Mengarelli, A.C.; Bottini, S.B.; Brignole, E.A. [UNS-CONICET, Bahia Blanca (Argentina)

1995-07-01

142

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

2015-03-01

143

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

144

Development of refractory armored silicon carbide by infrared transient liquid phase processing  

NASA Astrophysics Data System (ADS)

Tungsten (W) and molybdenum (Mo) were coated on silicon carbide (SiC) for use as a refractory armor using a high power plasma arc lamp at powers up to 23.5 MW/m 2 in an argon flow environment. Both tungsten powder and molybdenum powder melted and formed coating layers on silicon carbide within a few seconds. The effect of substrate pre-treatment (vapor deposition of titanium (Ti) and tungsten, and annealing) and sample heating conditions on microstructure of the coating and coating/substrate interface were investigated. The microstructure was observed by scanning electron microscopy (SEM) and optical microscopy (OM). The mechanical properties of the coated materials were evaluated by four-point flexural tests. A strong tungsten coating was successfully applied to the silicon carbide substrate. Tungsten vapor deposition and pre-heating at 5.2 MW/m 2 made for a refractory layer containing no cracks propagating into the silicon carbide substrate. The tungsten coating was formed without the thick reaction layer. For this study, small tungsten carbide grains were observed adjacent to the interface in all conditions. In addition, relatively large, widely scattered tungsten carbide grains and a eutectic structure of tungsten and silicon were observed through the thickness in the coatings formed at lower powers and longer heating times. The strength of the silicon carbide substrate was somewhat decreased as a result of the processing. Vapor deposition of tungsten prior to powder coating helped prevent this degradation. In contrast, molybdenum coating was more challenging than tungsten coating due to the larger coefficient of thermal expansion (CTE) mismatch as compared to tungsten and silicon carbide. From this work it is concluded that refractory armoring of silicon carbide by Infrared Transient Liquid Phase Processing is possible. The tungsten armored silicon carbide samples proved uniform, strong, and capable of withstanding thermal fatigue testing.

Hinoki, Tatsuya; Snead, Lance L.; Blue, Craig A.

2005-12-01

145

Use of ionic liquids for liquid-phase microextraction of polycyclic aromatic hydrocarbons.  

PubMed

This paper demonstrates, for the first time, that ionic liquids (IL) such as 1-octyl-3-methylimidazolium hexafluorophosphate ([C(8)MIM][PF(6)]) are excellent extraction solvents in liquid-phase microextraction (LPME). The unique properties of nonvolatility and adequate viscosity allow IL to be conveniently adopted as extraction solvents in both direct-immersion and headspace LPME. Model compounds, polycyclic aromatic hydrocarbons (PAHs), are conveniently and rapidly enriched in a 3-microL drop of [C(8)MIM][PF(6)] suspended on the tip of a microsyringe followed by liquid chromatographic determination. Compared to 1-octanol, a larger volume drop of [C(8)MIM][PF(6)] can be formed and survive for a longer extraction time; therefore, a much higher enrichment factor for PAHs can be reached. For low-volatility PAHs, direct-immersion LPME provides higher enrichment factors than that of headspace LPME. However, the enrichment factor obtained by headspace LPME was almost 3-fold of that by direct-immersion LPME in a 30-min extraction of the most volatile PAH, naphthalene. For 30-min direction-immersion LPME of EPA priority PAHs, the enrichment factor, correlation coefficient (R(2)), and reproducibility (RSD, n = 5) were in the range of 42-166, 0.9169-0.9976, and 2.8-12%, respectively. Considering that IL can be easily prepared from relatively inexpensive materials and tuned by combination of different anions and cations for task-specific extraction of analytes from various solvent media, this proposed method should have great potentiality in sample preparation. Furthermore, the nonvolatility of IL makes it potentially useful for headspace LPME of volatile analytes. PMID:14588028

Liu, Jing-fu; Jiang, Gui-bin; Chi, Yu-guang; Cai, Ya-qi; Zhou, Qing-xiang; Hu, Jing-Tian

2003-11-01

146

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

EPA Science Inventory

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

147

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

PubMed

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?nm(2) 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

148

Liquid phase co-oxidation of thiophenol and styrene by oxygen and t-butyl hydroperoxide  

SciTech Connect

Instability problems in both shale and petroleum derived middle distillate jet fuels have been correlated with the presence of peroxidic species. Although a good body of knowledge exists concerning the formation of peroxides in the liquid phase, relatively little is known about the reaction/decomposition pathways available when other functional groups are present. Since sulfur is the most abundant heteroatom present in jet fuels, the reaction of t-butyl hydroperoxide (tBHP) and/or oxygen with thiophenol in the presence of the active olefin, styrene, was examined in deaerated benzene at 120{degrees}C. The complex product mixture was analyzed by combined capillary column GC/MS. Major products included acetone, t-butanol and isobutylene from the tBHP. Thiophenol and styrene combined to form addition products. Phenyl disulfide was observed from the thiophenol. The results indicate that although the product slate was complex, it was possible to explain the product mix in terms of a few competing reactions.

Mushrush, G.W.; Hazlett, R.N.; Hardy, D.R. (George Mason Univ., Fairfax, VA (USA)); Watkins, J.M.; Black, B.H. (Geocenters, Inc., Suitland, MD (US))

1990-01-01

149

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

150

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

151

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

152

Catalytic liquid-phase oxidation in heterogeneous system as green chemistry goal—advantages and disadvantages of MCM-41 used as catalyst  

Microsoft Academic Search

This review article is devoted to the discoveries and\\/or knowledge developed in the past 10 years in the area of catalytic liquid-phase oxidation with hydrogen peroxide on mesoporous molecular sieves of MCM-41 type modified with various transition metals. The following parameters influencing activity and selectivity of the catalysts are considered: (i) nature of matrix for metal species limiting diffusion effects;

Maria Ziolek

2004-01-01

153

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

154

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

155

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

156

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

157

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

PubMed

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

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

2013-10-01

158

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

159

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

160

Enhanced Spatial Localization of Neuronal Activation Using Simultaneous Apparent-Diffusion-Coefficient and Blood-Oxygenation  

E-print Network

-Diffusion-Coefficient and Blood-Oxygenation Functional Magnetic Resonance Imaging Allen W. Song, Marty G. Woldorff, StaceyMRI) can detect blood oxygen- ation level dependent (BOLD) hemodynamic re- sponses secondary to local based on the differences in the mobility of the blood within them, thereby revealing the contributions

161

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

SciTech Connect

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

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

1995-07-01

162

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

PubMed Central

We review our recent study on the polyamorphism of the liquid and glass states in a monatomic system, a two-scale spherical-symmetric Jagla model with both attractive and repulsive interactions. This potential with a parametrization for which crystallization can be avoided and both the glass transition and the liquid-liquid phase transition are clearly separated, displays water-like anomalies as well as polyamorphism in both liquid and glassy states, providing a unique opportunity to study the interplay between the liquid-liquid phase transition and the glass transition. Our study on a simple model may be useful in understanding recent studies of polyamorphism in metallic glasses. PMID:21614201

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

2010-01-01

163

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

164

Reentrant Liquid-Liquid Phase Separation in Protein Solutions at Elevated Hydrostatic Pressures  

NASA Astrophysics Data System (ADS)

We present results from small-angle x-ray scattering data on the effect of high pressure on the phase behavior of dense lysozyme solutions in the liquid-liquid phase separation region, and characterize the underlying intermolecular protein-protein interactions as a function of temperature and pressure in this region of phase space. A reentrant liquid-liquid phase separation region has been discovered at elevated pressures, which originates in the pressure dependence of the solvent-mediated protein-protein interactions.

Möller, Johannes; Grobelny, Sebastian; Schulze, Julian; Bieder, Steffen; Steffen, Andre; Erlkamp, Mirko; Paulus, Michael; Tolan, Metin; Winter, Roland

2014-01-01

165

Liquid Phases in SU(3) Chiral Perturbation Theory: Drops of Strange Chiral Nucleon Liquid & Ordinary Chiral Heavy Nuclear Liquid  

E-print Network

Chiral SU(3) Perturbation Theory (SU3XPT) identifies hadrons as the building blocks of strongly interacting matter at low densities and temperatures. We show that it admits two co-existing chiral nucleon liquid phases at zero external pressure with well-defined surfaces: 1) ordinary microscopic chiral heavy nuclear liquid drops (XNL) and 2) a new Strange Chiral Nucleon Liquid (SXNL) phase with both microscopic and macroscopic drop sizes. Liquid drops of both XNL and SXNL are simultaneously solutions to the SU3XPT semi-classical equations of motion and obey all relevant CVC and PCAC equations. Axial-vector currents are conserved inside macroscopic drops of SXNL, a new form of baryonic matter with zero electric charge density, which is by nature "dark". The numerical values of all SU3XPT coefficients are used to fit current scattering experiments and ordinary XNL drops (identified with the ground state of ordinary even-even spin-zero spherical closed-shell nuclei). SXNL then also emerges (i.e. without new adjustable parameters). For certain SU3XPT coefficients, finite microscopic and macroscopic drops of SXNL may be the ground state of a collection of nucleons: ordinary heavy nuclei may be meta-stable, while oceans of SXNL may force qualitative and experimentally observable changes to the neutron star equation of state.

Bryan W. Lynn

2010-05-12

166

Viscosity B-coefficients and activation parameters for viscous flow of a solution of heptanedioic acid in aqueous sucrose solution.  

PubMed

Viscosity and density data for the system of heptanedioic acid dissolved in aqueous sucrose solution at temperature range from 288.15 to 313.15 K have been measured. The viscosity B-coefficients for heptanedioic acid in aqueous sucrose solution has been calculated. The effect of temperature and sucrose concentration on the B-coefficients is discussed. On the basis of the Feakins equation, the activation parameters (Deltamu3++, DeltaH3++, DeltaS3++, DeltaG12(0)++, DeltaH12(0)++ and DeltaS12(0)++) for viscous flow of the solution have been evaluated, together with the Gibbs energy of transfer for the solute from the ground state solvent to the hypothetical viscous transition state solvent (DeltaG3++(1-1')). The effect of sucrose concentration and temperature on the activation parameters has been discussed. PMID:14667714

Bai, Tong-Chun; Yan, Guo-Bing

2003-11-21

167

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

168

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

169

On the Maximal Deviation from the Mirror Image Approximation due to Solid Liquid Phase Transition  

NASA Astrophysics Data System (ADS)

We extend the Walsh and Christian (1955) analysis in a manner which allows a reasonable estimation of the expected deviation from the mirror image approximation due to solid liquid phase transition. This estimate is limited to a phase transition that occurs at shock unloading. This analysis provides a good estimate to metals with low melting pressure such as Tin and Lead.

Pistinner, S. L.; Pecker, S.; Werdiger, M.; Eliezer, S.

2007-12-01

170

Little Artifices of Huge Libraries: Secrets of Parallel Liquid-Phase Synthesis  

Microsoft Academic Search

Key aspects of differences between liquid-phase parallel synthesis and preparation of a single compound at a time are reviewed. Specific technique and equipment is required to make in the parallel manner such processes as heating (involving MW ovens and flow microreactors), extraction, filtration, and chromatography. Rich illustrations may be useful in educational courses on medicinal and combinatorial chemistry. In the

E. V. Babaev

2010-01-01

171

Application Of Continuous Liquid Phase Fluorescence Analysis For The Selective Determination Of Gases  

NASA Astrophysics Data System (ADS)

A porous membrane "Diffusion Scrubber" represents an ideal interface between trace atmospheric gases of interest and sensitive fluorescence-based continuous liquid phase analysis methods for the corresponding analytes. Analytical methods capable of determining low to sub-parts-per-billion levels of hydrogen peroxide, sulfur dioxide, ammonia and formaldehyde on a continuous basis are described.

Dasgupta, Purnendu K.

1987-01-01

172

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

173

The effects of liquid-phase rheology on the extrusion behaviour of paste  

Microsoft Academic Search

A description is given of experiments carried out to determine the effect of liquid-phase rheology on the extrusion behaviour of particulate pastes. These were prepared by mixing alumina powder with chosen amounts of four liquids. Measurements show that the properties of the pastes are directly related to those of the liquids from which they were made. Rheological properties of the

J. J. Benbow; S. Blackburn; H. Mills

1998-01-01

174

Environmental Application of Catalytic Processes: Heterogeneous Liquid Phase Oxidation of Phenol With Hydrogen Peroxide  

Microsoft Academic Search

The authors review the status of heterogeneous catalytic oxidation processes with hydrogen peroxide as an oxidant in a liquid phase. They focus on the priority organic pollutant–phenol as one of the most common persistent organic water contaminants, toxic even at low concentrations. A wide range of heterogeneous catalysts is covered, with a special emphasis on rapidly developing new catalytic systems.

Ekaterina V. Rokhina; Jurate Virkutyte

2010-01-01

175

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

176

Liquid-phase microextraction based on carrier mediated transport combined with liquid chromatography–mass spectrometry  

Microsoft Academic Search

Recently, we demonstrated for the first time liquid-phase microextraction (LPME) of polar drugs based on carrier mediated transport. In this new extraction technique, selected analytes were extracted as ion-pairs from small volumes of biological samples, through a thin layer of a water immiscible organic solvent immobilised in the pores of a porous hollow fibre (liquid membrane), and into a ?l

Tung Si Ho; Jan Leon Egge Reubsaet; Hanne Sofie Anthonsen; Stig Pedersen-Bjergaard; Knut Einar Rasmussen

2005-01-01

177

Comparison of solid and liquid-phase bioassays using ecoscores to assess1 contaminated soils2  

E-print Network

chemicals that may contaminate22 soils located in the vicinity of plants. Soil pollutants include polycyclic1 Comparison of solid and liquid-phase bioassays using ecoscores to assess1 contaminated soils2 3 on aqueous and solid phases of contaminated soils were compared,18 belonging to a wide array of trophic

Paris-Sud XI, Université de

178

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.

179

Critical interlayer thickness for transient liquid phase bonding in the CuSn system  

E-print Network

. Keywords: Transient liquid phase bonding; Electron beam methods; Copper; Intermetallic compounds 1 of the growth and subsequent contact of Cu6Sn5 intermetallic grains on the two surfaces to be bonded, prior, based on the heights of the largest intermetallic grains. Experiments are performed to ascertain

Zok, Frank

180

Liquid Phase 3D Printing for Quickly Manufacturing Metal Objects with Low Melting Point Alloy Ink  

E-print Network

Conventional 3D printings are generally time-consuming and printable metal inks are rather limited. From an alternative way, we proposed a liquid phase 3D printing for quickly making metal objects. Through introducing metal alloys whose melting point is slightly above room temperature as printing inks, several representative structures spanning from one, two and three dimension to more complex patterns were demonstrated to be quickly fabricated. Compared with the air cooling in a conventional 3D printing, the liquid-phase-manufacturing offers a much higher cooling rate and thus significantly improves the speed in fabricating metal objects. This unique strategy also efficiently prevents the liquid metal inks from air oxidation which is hard to avoid otherwise in an ordinary 3D printing. Several key physical factors (like properties of the cooling fluid, injection speed and needle diameter, types and properties of the printing ink, etc.) were disclosed which would evidently affect the printing quality. In addition, a basic route to make future liquid phase 3D printer incorporated with both syringe pump and needle arrays was also suggested. The liquid phase 3D printing method, which owns potential values not available in a conventional modality, opens an efficient way for quickly making metal objects in the coming time.

Lei Wang; Jing Liu

2014-02-25

181

Structured fiber supports for ionic liquid-phase catalysis used in gas-phase continuous hydrogenation  

Microsoft Academic Search

Structured supported ionic liquid-phase (SSILP) catalysis is a new concept with the advantages of ionic liquids (ILs) used as solvents for homogeneous catalyst and the further benefits of structured heterogeneous catalysts. This is achieved by confining the IL with the transition metal complex to the surface of a structured support consisting of sintered metal fibers (SMFs). In an attempt to

Marina Ruta; Igor Yuranov; Paul J. Dyson; Gabor Laurenczy; Lioubov Kiwi-Minsker

2007-01-01

182

Solid-liquid phase diagrams for the determination of the solid state nature of both polymorphs of (RS)-2-(2-oxo-pyrrolidin-1-yl)-butyramide.  

PubMed

This work focuses on the determination of the solid state nature of (RS)-2-(2-oxo-pyrrolidin-1-yl)-butyramide (Etiracetam), the racemic intermediate of (S)-2-(2-oxo-pyrrolidin-1-yl)-butyramide, an Active Pharmaceutical Ingredient, marketed under the name Levetiracetam(®). It is show how this information can easily be extracted from solid-liquid phase diagrams of the racemic system. As two polymorphs of Etiracetam are known (Forms I and II), the analyses have been performed considering both polymorphs. The solid-liquid phase diagrams are determined experimentally, using Differential Scanning Calorimetry, and theoretically, using the Prigogine-Defay and Schroeder-Van Laar equations. Only the phase diagram involving the polymorph stable at higher temperatures (Form II) can be constructed experimentally. The theoretical phase diagram involving this polymorph compares well with the experimental one, thus allowing the use of theoretical equations for the prediction of the solid-liquid phase diagram involving Form I, which is meta-stable above 30.5 °C. Our findings confirm that both polymorphs are racemic compounds, which is also confirmed by XRPD analysis. PMID:22846407

Herman, Christelle; Haut, Benoît; Aerts, Luc; Leyssens, Tom

2012-11-01

183

Properties of undoped and manganese-doped InGaAsP grown by liquid phase electroepitaxy  

NASA Technical Reports Server (NTRS)

Undoped and manganese-doped InGaAsP epilayers lattice matched to InP substrate have been grown by the liquid phase electroepitaxy technique. The dependence of growth velocity on current density for both undoped and doped layers has been studied. Layers of good surface morphology with hole concentrations in the range from 8 x 10 to the 16th to 4 x 10 to the 18th/cu cm have been achieved. The activation energy of the manganese acceptor level was estimated to vary from 57 to 32 meV with increasing hole concentration. The temperature dependence of carrier mobility data was analyzed in terms of different scattering mechanisms and the values of acceptor and donor densities determined were compared with those obtained from the temperature variation of Hall concentration data. Dependences of photoluminescence peak energy and intensity on the temperature and incident excitation levels have been investigated.

Iyer, Shanthi N.; Abul-Fadl, Ali; Collis, Ward J.; Khorrami, Mohammad N.

1988-01-01

184

Mixture distribution and flame propagation in a heavy-duty liquid petroleum gas engine with liquid phase injection  

Microsoft Academic Search

Enhanced mixture preparation by liquid phase injection on to the port could promote the application of liquefied petroleum gas (LPG) in spark ignition (SI) engines. Mixture distribution and flame propagation of the liquid phase LPG injection (LPLI) engine with a large bore size were investigated in a single-cylinder optical engine which had optical accesses through both sides of the cylinder

S Oh; C Bae

2004-01-01

185

Binary Solid-Liquid Phase Diagram of Phenol and t-Butanol: An Undergraduate Physical Chemistry Experiment  

ERIC Educational Resources Information Center

The determination of the solid-liquid phase diagram of a binary system is always used as an experiment in the undergraduate physical chemistry laboratory courses. However, most phase diagrams investigated in the lab are simple eutectic ones, despite the fact that complex binary solid-liquid phase diagrams are more common. In this article, the…

Xu, Xinhua; Wang, Xiaogang; Wu, Meifen

2014-01-01

186

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

NASA Astrophysics Data System (ADS)

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

Zuend, A.; Seinfeld, J.

2012-12-01

187

Predicted vs. Actual Resting Energy Expenditure and Activity Coefficients: Post-Gastric Bypass, Lean and Obese Women  

PubMed Central

Total Energy Expenditure (TEE) and energy requirements are commonly estimated from equations predicting Resting Energy Expenditure (REE) multiplied by a Physical Activity (PA) coefficient that accounts for both PA energy expenditure and the thermogenic effect of food. PA coefficients based on PA self-reports are a potential source of error that has not been evaluated. Therefore, in this study we compared: 1) the Harris-Benedict (HB), Mifflin-St. Jeor (MSJ), and the Food and Agriculture Organization/World Health Organization/United Nations University (FAO/WHO/UNU) REE equations with REE measured (REE-m) with indirect calorimetry; 2) PA coefficients determined with PA self-reports vs. objectively assessed PA; and 3) TEE estimates in post-Gastric Bypass (GB = 13), lean (LE = 7), and obese (OB = 12) women. REE was measured in the morning after an overnight fast with participants resting supine for 30 min. Self-reported PA was evaluated with a questionnaire and objectively measured with accelerometers worn for 5-7 days. Nutritional intake was evaluated with a food frequency questionnaire. Anthropometry included DEXA, and abdominal CT scans. Eligible GB had surgery ? 12 months before the study, and had ? 10 kg of body weight loss. All participants were 18-45 years of age, able to engage in ambulatory activities, and not taking part in exercise training programs. One-way ANOVA was used to detect differences in REE and TEE. Accuracy of REE prediction equations were determined by cases within 10% of REE-m, and agreement analyses. REE predictions were not different than REE-m, but agreements were better with HB and MSJ, particularly in the GB and LE groups. Discrepancies in the PA coefficients determined with self-report vs. objectively assessed PA resulted in TEE overestimates (approximately 200-300 Kcal/day) using HB and MSJ equations. FAO/WHO/UNU overestimated TEE in all groups regardless of the PA assessment method (approximately 300-900 kcal/day). These results suggest that: 1) HB and MSJ equations are good predictors of REE among GB and LE, but not among OB women, 2) PA coefficients used to estimate TEE must be determined with objective PA assessment, and 3) TEE estimates using PA coefficients with the FAO/WHO/UNU equation must be used with caution.

Ramirez-Marrero, Farah A.; Edens, Kim L.; Joyner, Michael J.; Curry, Timothy B.

2015-01-01

188

Liquid phase epitaxial growth of GaAs  

SciTech Connect

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

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

1997-10-01

189

[Determination of dichloromethane and trichloromethane residues in ranitidine hydrochloride by headspace liquid phase microextraction coupled with gas chromatography].  

PubMed

A method for the determination of residual dichloromethane and trichloromethane in ranitidine hydrochloride by headspace liquid phase microextraction coupled with gas chromatography (GC) was developed. A homemade device was used to protect the organic drop. The effects of the nature of extraction solvent, extraction time, extraction temperature and microdrop volume on the extraction efficiency were investigated separately. The optimal experimental conditions were as follows: 2 microL of n-tridecane as extraction solvent, 30 min of extraction time, 60 degrees C of extraction temperature. The correlation coefficients of linear calibration curve were 0.9733 and 0.9724 within the concentration ranges of dichloromethane (1-10 microg/g) and trichloromethane (1-10 microg/g), respectively. The detection limits of dichlormethane and trichloromethane were 0.0273 microg/g and 0.0410 microg/g, respectively, the relative standard deviations were lower than 4.36% and 5.89%, and the recoveries of the method were 93.6%-102% and 98.1% respectively. The method is simple and reliable. PMID:20352943

Shen, Shuchang; Yun, Dan; Li, Fei

2009-11-01

190

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

191

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

PubMed Central

The neural mechanisms of sensory responses recorded from the scalp or cortical surface remain controversial. Evoked vs. induced response components (i.e., changes in mean vs. variance) are associated with bottom-up vs. top-down processing, but trial-by-trial response variability can confound this interpretation. Phase reset of ongoing oscillations has also been postulated to contribute to sensory responses. In this article, we present evidence that responses under passive listening conditions are dominated by variable evoked response components. We measured the mean, variance, and phase of complex time-frequency coefficients of epidurally recorded responses to acoustic stimuli in rats. During the stimulus, changes in mean, variance, and phase tended to co-occur. After the stimulus, there was a small, low-frequency offset response in the mean and modest, prolonged desynchronization in the alpha band. Simulations showed that trial-by-trial variability in the mean can account for most of the variance and phase changes observed during the stimulus. This variability was state dependent, with smallest variability during periods of greatest arousal. Our data suggest that cortical responses to auditory stimuli reflect variable inputs to the cortical network. These analyses suggest that caution should be exercised when interpreting variance and phase changes in terms of top-down cortical processing. PMID:23657279

Krause, Bryan M.

2013-01-01

192

Liquid phase migration in the extrusion and squeezing of microcrystalline cellulose pastes.  

PubMed

Extensive movement of the liquid phase relative to the solids in solid-liquid pastes during extrusion forming is an undesirable process phenomenon. The impact of formulation and flow pattern on liquid phase migration (LPM) during extrusion of model pharmaceutical pastes (40-50 wt% microcrystalline cellulose/water) has been investigated by ram extrusion through square-entry and 45 degrees conical-entry dies, and by lubricated squeeze flow (extensional flow). Threshold velocities for LPM were observed in both configurations. Squeeze flow testing showed that dilation during extension can cause LPM, while ram extrusion featured both dilation effects and drainage due to compaction. The threshold velocities observed in the two configurations agreed when presented as characteristic shear rates. The threshold velocity increased with paste solids content. PMID:16766162

Mascia, S; Patel, M J; Rough, S L; Martin, P J; Wilson, D I

2006-09-01

193

Diffusion-stress coupling in liquid phase during rapid solidification of binary mixtures  

NASA Astrophysics Data System (ADS)

An analytical model has been developed to describe the diffusion-viscous stress coupling in the liquid phase during rapid solidification of binary mixtures. The model starts with a set of evolution equations for diffusion flux and viscous pressure tensor, based on extended irreversible thermodynamics. It has been demonstrated that the diffusion-stress coupling leads to non-Fickian diffusion effects in the liquid phase. With only diffusive dynamics, the model results in the nonlocal diffusion equations of parabolic type, which imply the transition to complete solute trapping only asymptotically at an infinite interface velocity. With the wavelike dynamics, the model leads to the nonlocal diffusion equations of hyperbolic type and describes the transition to complete solute trapping and diffusionless solidification at a finite interface velocity in accordance with experimental data and molecular dynamic simulation.

Sobolev, S. L.

2014-01-01

194

Methods and apparatus for using gas and liquid phase cathodic depolarizers  

NASA Technical Reports Server (NTRS)

The invention provides methods for using gas and liquid phase cathodic depolarizers in an electrochemical cell having a cation exchange membrane in intimate contact with the anode and cathode. The electrochemical conversion of cathodic depolarizers at the cathode lowers the cell potential necessary to achieve a desired electrochemical conversion, such as ozone evolution, at the anode. When gaseous cathodic depolarizers, such as oxygen, are used, a gas diffusion cathode having the cation exchange membrane bonded thereto is preferred. When liquid phase cathodic depolarizers are used, the cathode may be a flow-by electrode, flow-through electrode, packed-bed electrode or a fluidized-bed electrode in intimate contact with the cation exchange membrane.

Murphy, Oliver J. (Inventor); Hitchens, G. Duncan (Inventor)

1998-01-01

195

The effect of catalyst ratio on catalytic performance in liquid phase dimethyl ether process  

SciTech Connect

In the liquid phase dimethyl ether (LPDME) process, two functionally different catalysts are slurried together in an inert liquid medium. Syngas reacts on the surface of the methanol catalyst and methanol is dehydrated on the surface of the dehydration catalyst dispersed in the liquid. The process is adaptable to carbon monoxide-rich syngas derived from second generation coal gasifiers. The effect of catalyst ratio on catalytic performances of the dual catalyst was studied in liquid phase dimethyl ether synthesis from syngas at 280 C, 4.0 MPa. CO conversion, H{sub 2} conversion and DME productivity increased with an increase of catalyst ratio initially, reached their maximum at a catalyst ratio of 4.0--5.0, and then decreased. Methanol productivity and methanol equivalent productivity had a similar trend to that of DME productivity. DME selectivity and hydrocarbon selectivity increased with an increase in catalyst ratio whereas methanol selectivity decreased with catalyst ratio.

Guo Junwang; Niu Yuqin; Zhang Bijiang [Chinese Academy of Sciences, Taiyuan, Shanxi (China). Inst. of Coal Chemistry

1997-12-31

196

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

197

Liquid-Liquid Phase Transitions in Tetrahedrally Coordinated Fluids via Wertheim Theory.  

PubMed

Network interpenetration has been proposed as a mechanism for generating liquid-liquid phase transitions in one component systems. We introduce a model of four coordinated particles, which explicitly treats the system as a mixture of two interacting interpenetrating networks that can freely exchange particles. This model can be solved within Wertheim's theory for associating fluids and shows liquid-liquid phase separations (in addition to the gas-liquid) for a wide range of model parameters. We find that originating a liquid-liquid transition requires a small degree of interpenetrability and a preference for intranetwork bonding. Physically, these requirements can be seen as controlling the softness of the particle-particle interaction and the bond flexibility, in full agreement with recent findings [Smallenburg, F.; Filion, L.; Sciortino, F. Nat. Phys. 2014, 10, 653]. PMID:25384011

Smallenburg, Frank; Filion, Laura; Sciortino, Francesco

2014-11-10

198

Spin-liquid phase and order by disorder of classical Heisenberg spins on the swedenborgite lattice  

NASA Astrophysics Data System (ADS)

Frustration refers to the inability to satisfy competing interactions simultaneously, often leading to a large number of degenerate ground states. This can suppress ordering tendencies, sometimes resulting in a spin-liquid phase. An intrinsic effect lifting this degeneracy is entropic order by disorder. We present strong evidence that a classical nearest-neighbor Heisenberg model on the swedenborgite lattice exhibits both an extended spin-liquid phase as well as entropic order-by-disorder choosing coplanar configurations after a first-order transition. We argue that this observation renders magnetic insulators such as RBaCo4O7, where R denotes a rare-earth atom, prime candidates for displaying spin-liquid behavior and entropic order-by-disorder physics due to their large exchange constant.

Buhrandt, Stefan; Fritz, Lars

2014-07-01

199

Liquid Phase 3D Printing for Quickly Manufacturing Metal Objects with Low Melting Point Alloy Ink  

E-print Network

Conventional 3D printings are generally time-consuming and printable metal inks are rather limited. From an alternative way, we proposed a liquid phase 3D printing for quickly making metal objects. Through introducing metal alloys whose melting point is slightly above room temperature as printing inks, several representative structures spanning from one, two and three dimension to more complex patterns were demonstrated to be quickly fabricated. Compared with the air cooling in a conventional 3D printing, the liquid-phase-manufacturing offers a much higher cooling rate and thus significantly improves the speed in fabricating metal objects. This unique strategy also efficiently prevents the liquid metal inks from air oxidation which is hard to avoid otherwise in an ordinary 3D printing. Several key physical factors (like properties of the cooling fluid, injection speed and needle diameter, types and properties of the printing ink, etc.) were disclosed which would evidently affect the printing quality. In addit...

Wang, Lei

2014-01-01

200

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

SciTech Connect

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

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

1997-08-01

201

Effective liquid-phase exfoliation and sodium ion battery application of MoS2 nanosheets.  

PubMed

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

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

2014-05-28

202

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

203

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

204

Local order in liquid phases of Al–Ga–Zn alloys  

Microsoft Academic Search

In this paper, neutron scattering experiments at different temperatures allow us to study local order in the different liquid phases which can exist in Al–Ga–Zn alloys. The ternary phase diagram of these phases has been established from calorimetry and X-ray diffraction results. This study showed that the liquid structure factors in these samples agreed with the presence of a local

K. Jardet; C. Favotto; R. Bellissent; P. Satre

2003-01-01

205

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

206

Microstructural evolution during liquid phase sintering: Part I. Development of microstructure  

Microsoft Academic Search

During liquid phase sintering, numerous solid-solid particle contacts can be generated by particle motion within the fluid. It is shown that, somewhat surprisingly, Brownian motion can produce such contacts. If such contacts are accompanied by particle adherence, the particles can then subsequently fuse into one ( i.e., coalesce) by the liquid state analog of the evaporation-condensation mechanism of sintering. An

T. H. Courtney

1977-01-01

207

Microstructural development and evolution in liquid-phase sintered Fe-Cu alloys  

Microsoft Academic Search

An experimental study relating the scale and contiguity of liquid-phase sintered Fe-Cu alloys to sintering conditions has been conducted over a broad range of solid-phase volume fraction. It is found that the solid-phase contiguity attains a steady-state value at fairly short sintering times and that contiguity increases with increasing particle volume fraction, but is essentially independent of sintering temperature. Both

A. N. Niemi; T. H. Courtney

1981-01-01

208

Microstructural evolution during liquid phase sintering: Part I. Development of microstructure  

Microsoft Academic Search

During liquid phase sintering, numerous solid-solid particle contacts can be generated by particle motion within the fluid.\\u000a It is shown that, somewhat surprisingly, Brownian motion can produce such contacts. If such contacts are accompanied by particle\\u000a adherence, the particles can then subsequently fuse into one (i.e., coalesce) by the liquid state analog of the evaporation-condensation mechanism of sintering. An isolated

T. H. Courtney

1977-01-01

209

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

PubMed

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

2010-09-28

210

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

211

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

212

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

Microsoft Academic Search

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

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

1999-01-01

213

The effect of applied magnetic field on the growth mechanisms of liquid phase electroepitaxy  

Microsoft Academic Search

Binary (GaAs) and ternary (InGaAs) single crystals were grown by the growth process of liquid phase electroepitaxial (LPEE) under an applied static magnetic field. The effect of the applied magnetic field on two main growth mechanisms of the LPEE growth process, namely the “electromigration” and “natural convection” in the liquid zone, were examined numerically and experimentally. Numerical results show that

Hamdi Sheibani; Yongcai Liu; Susumu Sakai; Brian Lent; Sadik Dost

2003-01-01

214

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

Microsoft Academic Search

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

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

2000-01-01

215

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

Microsoft Academic Search

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

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

2004-01-01

216

Separation of Liquid Phases in Giant Vesicles of Ternary Mixtures of Phospholipids and Cholesterol  

PubMed Central

We use fluorescence microscopy to directly observe liquid phases in giant unilamellar vesicles. We find that a long list of ternary mixtures of high melting temperature (saturated) lipids, low melting temperature (usually unsaturated) lipids, and cholesterol produce liquid domains. For one model mixture in particular, DPPC/DOPC/Chol, we have mapped phase boundaries for the full ternary system. For this mixture we observe two coexisting liquid phases over a wide range of lipid composition and temperature, with one phase rich in the unsaturated lipid and the other rich in the saturated lipid and cholesterol. We find a simple relationship between chain melting temperature and miscibility transition temperature that holds for both phosphatidylcholine and sphingomyelin lipids. We experimentally cross miscibility boundaries both by changing temperature and by the depletion of cholesterol with ?-cyclodextrin. Liquid domains in vesicles exhibit interesting behavior: they collide and coalesce, can finger into stripes, and can bulge out of the vesicle. To date, we have not observed macroscopic separation of liquid phases in only binary lipid mixtures. PMID:14581208

Veatch, Sarah L.; Keller, Sarah L.

2003-01-01

217

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

218

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

PubMed

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

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

2013-08-01

219

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

220

On the relation between the activation energy for electron attachment reactions and the size of their thermal rate coefficients.  

PubMed

Rate coefficients k(T) for dissociative electron attachment (DEA) to molecules in many cases exhibit a more or less strong rise with increasing temperature T (the electron temperature T(e) and the molecular temperature T(G) are assumed to be in thermal equilibrium, i.e., T = T(e) = T(G)). This rise is frequently modeled by the Arrhenius equation k(T) = k(A) exp[-E(a)?(k(B)T)], and an activation energy E(a) is deduced from fits to the experimental data k(T). This behavior reflects the presence of an energy barrier for the anion on its path to the dissociated products. In a recent paper [J. Kopyra, J. Wnorowska, M. Forys?, and I. Szamrej, Int. J. Mass Spectrom. 268, 60 (2007)] it was suggested that the size of the rate coefficients for DEA reactions at room temperature exhibits an exponential dependence on the activation energy, i.e., k(E(a); T ? 300 K) = k(1) exp[-E(a)?E(0)]. More recent experimental data for molecules with high barriers [T. M. Miller, J. F. Friedman, L. C. Schaffer, and A. A. Viggiano, J. Chem. Phys. 131, 084302 (2009)] are compatible with such a correlation. We investigate the validity and the possible origin of this dependence by analyzing the results of R-matrix calculations for temperature-dependent rate coefficients of exothermic DEA processes with intermediate barrier toward dissociation. These include results for model systems with systematically varied barrier height as well as results of molecule-specific calculations for CH(3)Cl, CH(3)Br, CF(3)Cl, and CH(2)Cl(2) (activation energies above 0.2 eV) involving appropriate molecular parameters. A comparison of the experimental and theoretical results for the considered class of molecules (halogenated alkanes) supports the idea that the exponential dependence of k(T = 300 K) on the activation energy reflects a general phenomenon associated with Franck-Condon factors for getting from the initial neutral vibrational levels to the dissociating final anion state in a direct DEA process. Cases are discussed for which the proposed relation does not apply. PMID:21322676

Hotop, H; Ruf, M-W; Kopyra, J; Miller, T M; Fabrikant, I I

2011-02-14

221

On the relation between the activation energy for electron attachment reactions and the size of their thermal rate coefficients  

NASA Astrophysics Data System (ADS)

Rate coefficients k(T) for dissociative electron attachment (DEA) to molecules in many cases exhibit a more or less strong rise with increasing temperature T (the electron temperature Te and the molecular temperature TG are assumed to be in thermal equilibrium, i.e., T = Te = TG). This rise is frequently modeled by the Arrhenius equation k(T) = kA exp[-Ea/(kBT)], and an activation energy Ea is deduced from fits to the experimental data k(T). This behavior reflects the presence of an energy barrier for the anion on its path to the dissociated products. In a recent paper [J. Kopyra, J. Wnorowska, M. Fory?, and I. Szamrej, Int. J. Mass Spectrom. 268, 60 (2007)] it was suggested that the size of the rate coefficients for DEA reactions at room temperature exhibits an exponential dependence on the activation energy, i.e., k(Ea; T ? 300 K) = k1 exp[-Ea/E0]. More recent experimental data for molecules with high barriers [T. M. Miller, J. F. Friedman, L. C. Schaffer, and A. A. Viggiano, J. Chem. Phys. 131, 084302 (2009)] are compatible with such a correlation. We investigate the validity and the possible origin of this dependence by analyzing the results of R-matrix calculations for temperature-dependent rate coefficients of exothermic DEA processes with intermediate barrier toward dissociation. These include results for model systems with systematically varied barrier height as well as results of molecule-specific calculations for CH3Cl, CH3Br, CF3Cl, and CH2Cl2 (activation energies above 0.2 eV) involving appropriate molecular parameters. A comparison of the experimental and theoretical results for the considered class of molecules (halogenated alkanes) supports the idea that the exponential dependence of k(T = 300 K) on the activation energy reflects a general phenomenon associated with Franck-Condon factors for getting from the initial neutral vibrational levels to the dissociating final anion state in a direct DEA process. Cases are discussed for which the proposed relation does not apply.

Hotop, H.; Ruf, M.-W.; Kopyra, J.; Miller, T. M.; Fabrikant, I. I.

2011-02-01

222

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

NASA Astrophysics Data System (ADS)

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

Bechtel, Kate L.

223

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

224

A Microfluidic System for the Continuous Recycling of Unmodified Homogeneous Palladium Catalysts through Liquid/Liquid Phase Separation  

E-print Network

A prototype microflow system for the continuous recycling of homogeneous catalysts through liquid/liquid phase separation was developed and its effectiveness demonstrated in a challenging palladium-catalyzed hydroxylation ...

Li, Pengfei

225

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

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 either ammonium sulfate or ammonium bisulfate. 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 particles containing ammonium sulfate mixed with 20 different organic species at 244 ± 1 K, 263 ± 1 K, and 278 ± 1 K; a few particles were also studied at 290 ± 1 K. 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 organic-ammonium sulfate particles 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. The high SRH values (> 65%) in these experiments may explain the lack of temperature dependence. Since water is a plasticizer, high relative humidities can lead to high water contents, low viscosities, and high diffusion rates in the particles. For these cases, unless the temperature is very low, liquid-liquid phase separation is not expected to be kinetically inhibited. The occurrence of liquid-liquid phase separation and SRH did depend strongly on temperature over the range of 290-244 K for particles containing ?,4-dihydroxy-3-methoxybenzeneacetic acid mixed with ammonium bisulfate. For this particle type, a combination of low temperatures and low water content likely favored kinetic inhabitation of the liquid-liquid phase separation by slow diffusion rates in highly viscous particles. The combined results suggest that liquid-liquid phase separation is likely a common occurrence in atmospheric particles at temperatures from 244-290 K, although particles that do not undergo liquid-liquid phase separation are also likely common.

You, Y.; Bertram, A. K.

2015-02-01

226

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

227

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

NASA Astrophysics Data System (ADS)

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

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

2011-09-01

228

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

229

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

SciTech Connect

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

National Energy Technology Laboratory

2003-10-27

230

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

PubMed

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

Pawar, Nisha; Bohidar, H B

2010-09-01

231

Hall Effect Studies of AlGaAs Grown by Liquid-Phase Epitaxy for Tandem Solar Cell Applications  

NASA Astrophysics Data System (ADS)

We report results from Hall effect studies on Al x Ga1- x As ( x = 0.23-0.24) with bandgap energies of 1.76 ± 0.01 eV grown by liquid-phase epitaxy (LPE). Room-temperature Hall measurements on unintentionally doped AlGaAs revealed p-type background doping for concentrations in the range 3.7-5.2 × 1016 cm-3. Sn, Te, Ge, and Zn-doped AlGaAs were also characterized to study the relationship between doping concentrations and the atomic fractions of the dopants in the melt. Temperature-dependent Hall measurements were performed to determine the activation energies of the four dopants. Deep donor levels (DX centers) were dominant for Sn-doped Al0.24Ga0.76As, but not for Te-doped Al0.24Ga0.76As. Comparison of the temperature-dependent Hall effect results for unintentionally and intentionally doped Al0.24Ga0.76As indicated that the impurity contributing to the p-type background doping had the same activation energy as Mg. We thus suggest a Te-doped emitter and an undoped or Ge-doped base to maximize the efficiency of Al x Ga1- x As ( x ˜ 0.23) solar cells grown by LPE.

Zhao, Xin; Montgomery, Kyle H.; Woodall, Jerry M.

2014-11-01

232

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

233

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

234

Enhanced degradation of bioremediation residues in petroleum-contaminated soil using a two-liquid-phase bioslurry reactor.  

PubMed

A study was performed to determine the potential of two-liquid-phase (TLP) bioslurry reactors using silicon oil as solvent for degradation of residual contaminants in petroleum-contaminated soil. The residues were characterized by gas chromatography-mass spectrometry and electrospray ionization Fourier transform ion cyclotron resonance mass spectrometry. This allowed for the identification of a mixture of residual biomarkers, metabolic byproducts, oxygenated and hetero-polynuclear aromatic hydrocarbons in the contaminated soil. The removal amount of total extractable organics (TEO) was 15900mgkg(-1) soil in the TLP reactor within 12weeks. However, TEO remained intact in the bioslurry reactor without the addition of silicon oil for the duration of the experiment, due to high toxicity of metabolites to the microorganisms. The availability of TEO was calculated using a mild extraction with Triton X-100, and the amount of TEO extracted was in accord with the amount of biodegraded TEO. Significantly reduced toxicity in soil was observed at week 12 through TLP remediation. Dehydrogenase activity in the bioslurry reactor was strongly suppressed. Fluorescein diacetate was significantly hydrolyzed by the composition of bioremediation residues in the contaminated soil. Microbial adhesion to the solvent was revealed by the determination of microbial activity in the water-immiscible-liquid. PMID:19709718

Lu, Mang; Zhang, Zhongzhi; Sun, Shanshan; Wang, Qinfang; Zhong, Weizhang

2009-09-01

235

Mössbauer characterization of joints of steel pieces in transient liquid phase bonding experiences  

NASA Astrophysics Data System (ADS)

Joining of seamless, low carbon, steel tubes were performed by means of Transient Liquid Phase Bonding process employing a foil of Fe-Si-B metallic glass as filler material. The influence of the main parameters of the process was evaluated: temperature, holding time, pressure and post weld heat treatment. Powder samples were obtained from the joint of tubes and characterized employing Mössbauer Spectroscopy in transmission geometry. The sampling was performed both in tubes successfully welded and in those which show joint defects. The results obtained are correlated with the obtained microstructure and the diffusion of Si and B during the process.

di Luozzo, N.; Martínez Stenger, P. F.; Canal, J. P.; Fontana, M. R.; Arcondo, B.

2011-11-01

236

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

237

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

238

Hyphenating liquid phase separation techniques with mass spectrometry: on-line or off-line.  

PubMed

The advantages of hyphenating analytical separation techniques to mass spectrometers have been recognised since the 1970s. The first attempts to couple liquid phase separations to mass spectrometry(MS) were problematic, but the development of electrospray ionisation (ES) in 1984 facilitated the production of routinely used, commercial interfaces. This review considers the most recent major developments in hyphenating liquid chromatographic and electrophoretic separations to mass spectrometry, and considers the role the post genomic sciences have played in driving them. It also considers why, despite all of the advances in hyphenation, the future appears to hold a major role for off-line analysis. PMID:15685782

Edwards, Emma; thomas-Oates, Jane

2005-01-01

239

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

SciTech Connect

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

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

2005-02-09

240

An enthalpy-based lattice Boltzmann model for diffusion dominated solid liquid phase transformation  

NASA Astrophysics Data System (ADS)

An extended lattice Boltzmann (LB) formulation is developed for simulation of three-dimensional heat diffusion, coupled with solid liquid phase transition aspects. Thermodynamic variables are obtained through the evolution equation of a single particle distribution function. Phase change aspects are tackled by an enthalpy-based approach. The proposed model is subsequently utilized to simulate a generic laser surface melting process and compared with the continuum model results obtained by solving the governing equation for energy transport. The comparison shows a potentiality of the developed LB method to solve phase change problems in a computationally effective and convenient manner.

Chatterjee, Dipankar; Chakraborty, Suman

2005-06-01

241

Kinetics of methyl ter-butyl ether synthesis in liquid phase  

SciTech Connect

Studies carried out on the reaction of the isobutylene etherification with methanol in liquid phase, and in presence of commercial resins such as Bayer K-2634, Lewatit SP 112 MB and Amberlyst 15 show an excellent selectivity towards MTBE. The tests show that Bayer K-2634 resin produces the highest conversion values of isobutylene within the range of variables analyzed. The behavior of different catalysts corresponds to an exothermic reversible reaction, where a maximum conversion value is reached, at a given temperature. However, the conversion value decreases at higher temperatures. Conversions show the following reactivity order: Bayer > Amberlyst > Lewatit. 13 refs., 2 figs.

Trujillo de H., J.; Marzuka, S.; Giannetto, G. [Universidad Central de Venezuela, Caracas (Venezuela)

1996-12-31

242

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

PubMed

In this work, we compare experimental data on myoglobin hydrated powders from elastic neutron scattering, broadband dielectric spectroscopy, and differential scanning calorimetry. Our aim is to obtain new insights on the connection between the protein dynamical transition, a fundamental phenomenon observed in proteins whose physical origin is highly debated, and the liquid-liquid phase transition (LLPT) possibly occurring in protein hydration water and related to the existence of a low temperature critical point in supercooled water. Our results provide a consistent thermodynamic/dynamic description which gives experimental support to the LLPT hypothesis and further reveals how fundamental properties of water and proteins are tightly related. PMID:24089711

Schirò, Giorgio; Fomina, Margarita; Cupane, Antonio

2013-09-28

243

Cathodoluminescence of Al/x/Ga/1-x/As grown by liquid-phase epitaxy  

NASA Technical Reports Server (NTRS)

Small-area contrast fluctuations observed in cathodoluminescence-mode SEM images of thin Al(x)Ga(1-x)As layers grown by liquid-phase epitaxy on GaAs:Cr substrates are attributed to local variations in alloy composition. Quantitative estimates of the composition excursions are obtained from the variations in CL intensity by calibration against compositions known from electron-probe microanalysis. In a typical sample, the CL variations are shown to correspond to peak-to-peak fluctuations of about 1 at. % of Al and occur over irregular regions generally in the range 6-20 microns in diameter.

Levin, E. R.; Ladany, I.

1978-01-01

244

The Plastic and Liquid Phases of CCl$_3$Br Studied by Molecular Dynamics Simulations  

E-print Network

We present a molecular dynamics study of the liquid and plastic crystalline phases of CCl$_3$Br. We investigated the short-range orientational order using a recently developed classification method and we found that both phases behave in a very similar way. The only differences occur at very short molecular separations, which are shown to be very rare. The rotational dynamics was explored using time correlation functions of the molecular bonds. We found that the relaxation dynamics corresponds to an isotropic diffusive mode for the liquid phase, but departs from this behavior as the temperature is decreased and the system transitions into the plastic phase.

Nirvana Caballero; Mariano Zuriaga; Marcelo Carignano; Pablo Serra

2013-07-12

245

Polymorphism in glassy silicon: Inherited from liquid-liquid phase transition in supercooled liquid  

PubMed Central

Combining molecular dynamics (MD) simulation and Voronoi polyhedral analyses, we discussed the microstructure evolution in liquid and glassy silicon during cooling by focusing on the fraction of various clusters. Liquid-liquid phase transition (LLPT) is detected in supercooled liquid silicon However, freezing the high-density liquid (HDL) to the glassy state is not achieved as the quenching rate goes up to 1014?K/s. The polyamorphism in glassy silicon is found to be mainly associated with low-density liquid (LDL). PMID:25716054

Zhang, Shiliang; Wang, Li-Min; Zhang, Xinyu; Qi, Li; Zhang, Suhong; Ma, Mingzhen; Liu, Riping

2015-01-01

246

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

PubMed

The phase diagram of the two-dimensional particles interacting through a smooth version of Stell-Hemmer interaction was studied using Monte Carlo computer simulations. By evaluating the pressure-volume isotherms, we observed liquid-liquid, liquid-gas phase transitions and three stable crystal phases. The model shows the liquid-liquid critical point in stable liquid phase and is confirmed by observing properties of other thermodynamic functions such as heat capacity and isothermal compressibility, for example. The liquid-gas and the liquid-liquid critical points were estimated within the thermodynamic limit. PMID:24483440

Urbic, Tomaz

2013-12-01

247

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

NASA Astrophysics Data System (ADS)

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

Urbic, Tomaz

2013-12-01

248

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

NASA Astrophysics Data System (ADS)

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

Schirò, Giorgio; Fomina, Margarita; Cupane, Antonio

2013-09-01

249

Polymorphism in glassy silicon: Inherited from liquid-liquid phase transition in supercooled liquid  

NASA Astrophysics Data System (ADS)

Combining molecular dynamics (MD) simulation and Voronoi polyhedral analyses, we discussed the microstructure evolution in liquid and glassy silicon during cooling by focusing on the fraction of various clusters. Liquid-liquid phase transition (LLPT) is detected in supercooled liquid silicon However, freezing the high-density liquid (HDL) to the glassy state is not achieved as the quenching rate goes up to 1014 K/s. The polyamorphism in glassy silicon is found to be mainly associated with low-density liquid (LDL).

Zhang, Shiliang; Wang, Li-Min; Zhang, Xinyu; Qi, Li; Zhang, Suhong; Ma, Mingzhen; Liu, Riping

2015-02-01

250

The Plastic and Liquid Phases of CCl$_3$Br Studied by Molecular Dynamics Simulations  

E-print Network

We present a molecular dynamics study of the liquid and plastic crystalline phases of CCl$_3$Br. We investigated the short-range orientational order using a recently developed classification method and we found that both phases behave in a very similar way. The only differences occur at very short molecular separations, which are shown to be very rare. The rotational dynamics was explored using time correlation functions of the molecular bonds. We found that the relaxation dynamics corresponds to an isotropic diffusive mode for the liquid phase, but departs from this behavior as the temperature is decreased and the system transitions into the plastic phase.

Caballero, Nirvana; Carignano, Marcelo; Serra, Pablo

2013-01-01

251

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

SciTech Connect

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

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

1995-10-01

252

Cluster Monte Carlo and numerical mean field analysis for the water liquid--liquid phase transition  

E-print Network

By the Wolff's cluster Monte Carlo simulations and numerical minimization within a mean field approach, we study the low temperature phase diagram of water, adopting a cell model that reproduces the known properties of water in its fluid phases. Both methods allows us to study the water thermodynamic behavior at temperatures where other numerical approaches --both Monte Carlo and molecular dynamics-- are seriously hampered by the large increase of the correlation times. The cluster algorithm also allows us to emphasize that the liquid--liquid phase transition corresponds to the percolation transition of tetrahedrally ordered water molecules.

Marco G. Mazza; Kevin Stokely; Elena Strekalova; H. Eugene Stanley; Giancarlo Franzese

2009-01-20

253

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

SciTech Connect

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

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

2009-01-01

254

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

255

Research on Si-Al based catalysts prepared by complete liquid-phase method for DME synthesis in a slurry reactor  

NASA Astrophysics Data System (ADS)

A series of Si-Al based DME synthesis catalysts were prepared by complete liquid-phase method and characterized by in situ XPS, XRD, N 2 adsorption and NH 3-TPD analyses. Based on the results, the addition of Si could adjust the pore structure and surface acidity of catalyst, exhibiting a strong promoting effect on the CO conversion and DME selectivity. However, when Si/Al ratio is higher, Si would cover active sites and increase the amount of strong acidity sites, causing the reduction in catalytic activity. It was found from in situ XPS characterization that Cu 0 is the active center of methanol synthesis in DME production, and the addition of Si changes the chemical surroundings of active components and weaken the interaction between Cu, Zn and Al, which maybe give rise to the decrease in catalyst stability.

Li, Zhihong; Zuo, Zhijun; Huang, Wei; Xie, Kechang

2011-01-01

256

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

NASA Astrophysics Data System (ADS)

Tungsten-nickel-iron heavy metals are fabricated from powders by liquid phase sintering. A study of the sintering mechanism of heavy metals with a low amount of tungsten particles can, depending on sedimentation, only be done under microgravity. At two earlier Texus flights, No 10 & 19, the growth rate and agglomeration of tungsten particles under microgravity were compared to that under gravity and sedimentation. During the first minute sintering period the particles in the agglomerates were separated and the particle distribution became even. The particle growth rate under microgravity, initially high, is slowing down. At further studies under gravity the influence of surface energy between the liquid phase and the tungsten particles have been investigated. Additions of sulphur and cobolt were used to decrease the surface energy and the use of nickel without iron to increase the energy. At a high surface energy the growth rate increases due to increased driving force. Preliminary results from the Texus 26 flight (April 90) are included.

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

257

Liquid-liquid phase separation in solutions of living semiflexible polymers  

NASA Astrophysics Data System (ADS)

We consider a model of living semiflexible polymers in a solution and obtain results for the liquid-liquid phase separation, which has been a subject of growing interest in the literature and has been studied in some recent experiments. The tetrahedral lattice model is solved exactly on a Husimi cactus of coordination number q=4. The exact solution on the Husimi cactus forms the approximate theory for the original lattice. We consider the end groups to be a different species from the middle groups. This allows us to incorporate the end-group effects in our calculations, which become important at low molecular weights. We investigate the effect of chain rigidity, end-group/middle-group interactions, solvent quality, and the chemical potential of the end-group on the liquid-liquid coexistence curve. We also calculate the average molecular weights of the coexisting liquid phases. The bending penalty ? is found to shift the phase diagram only slightly. Attractive end-group/middle-group interaction enhances the phase separation. Due to the exactness of our calculations, the theory never violates thermodynamics and is applicable in the entire parameter space. Our theory also improves upon the classical theories and hence our results should prove useful.

Rane, Sagar S.

2003-01-01

258

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

259

Liquid phase preparation and fluorescence of flake-liked NdF{sub 3} nanomaterials  

SciTech Connect

Graphical abstract: Room-temperature emission spectra of NdF{sub 3} nanoflakes exhibit a strong luminescence emission peak at 402 nm when irradiated by an excitation wavelength of 250 nm. Display Omitted Highlights: ? NdF{sub 3} nanoflakes have been successfully prepared by a facile and repeatable liquid phase preparation. ? The action of oxalic acid in the reaction process was studied, showing important in the morphology of neodymium fluorides. ? The study on the fluorescent properties of flake-like NdF{sub 3} nanomaterials shows a strong emission peak at 402 nm by the excitation wavelength of 250 nm. -- Abstract: Neodymium fluoride nanoflakes were successfully prepared by a facile liquid phase preparation with Nd(NO{sub 3}){sub 3} and NaF as raw materials. In the process, oxalic acid acting as template agent was found to play important roles in the morphology of neodymium fluorides. The as-synthesized NdF{sub 3} nanoflakes were characterized by various techniques of X-ray diffraction (XRD), scanning electron microscope (SEM) and energy dispersive X-ray spectrometer instrument (EDS). The fluorescent properties of neodymium fluoride nanoflakes were investigated, showing a strong luminescence emission peak at 402 nm by the excitation wavelength of 250 nm.

Tian, Li, E-mail: ltian@hnust.edu.cn [Institute of Chemistry and Chemical Engineering, Hunan University of Science and Technology, Xiangtan 411201 (China) [Institute of Chemistry and Chemical Engineering, Hunan University of Science and Technology, Xiangtan 411201 (China); State Key Laboratory of Inorganic Synthesis and Preparative Chemistry, College of Chemistry, Jilin University, Changchun 130012 (China); Lian, Peili; Sun, Qiliang; Long, Peng; Xiang, Shaobin [Institute of Chemistry and Chemical Engineering, Hunan University of Science and Technology, Xiangtan 411201 (China)] [Institute of Chemistry and Chemical Engineering, Hunan University of Science and Technology, Xiangtan 411201 (China); Zhu, Guangshan [State Key Laboratory of Inorganic Synthesis and Preparative Chemistry, College of Chemistry, Jilin University, Changchun 130012 (China)] [State Key Laboratory of Inorganic Synthesis and Preparative Chemistry, College of Chemistry, Jilin University, Changchun 130012 (China)

2013-01-15

260

Confinement effect on the adsorption from a binary liquid system near liquid/liquid phase separation.  

PubMed

The preferential adsorption of one component of a binary system at the inner surfaces of mesoporous silica glasses was studied in a wide composition range at temperatures close to liquid/liquid phase separation. Confinement effects on the adsorption were investigated by using three controlled-pore glass (CPG-10) materials of different mean pore size (10 to 50 nm). For the experimental system (2-butoxyethanol+water), which exhibits an upper miscibility gap, strong preferential adsorption of water occurs, as the coexistence curve is approached at bulk compositions, at which water is the minority component. In this strong adsorption regime the area-related surface excess amount of adsorbed water decreases with decreasing pore width, while the shift in the volume-related mean composition of the pore liquid shows an opposite trend, i.e., greatest deviation from bulk composition occurring in the most narrow pores. A simple mean-field lattice model of a liquid mixture confined by parallel walls is adopted to rationalize these experimental findings. This model reproduces the main findings of the confinement effect on the adsorption near liquid/liquid phase separation. PMID:15268220

Rother, Gernot; Woywod, Dirk; Schoen, Martin; Findenegg, Gerhard H

2004-06-22

261

Investigation of metal-matrix composite containing liquid-phase dispersion  

NASA Astrophysics Data System (ADS)

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

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

2012-02-01

262

Liquid-liquid phase transition in a family of simple models of tetrahedral liquid  

NASA Astrophysics Data System (ADS)

Liquids with tetrahedral symmetry of the first coordination shell often display anomalous thermodynamic and dynamic behavior. Sometimes, these anomalies are associated with the liquid-liquid phase transition at high pressures and low temperatures. We study a family of simple models with few parameters and investigate the conditions for the existence of the liquid-liquid phase transition. A molecule in these models consists of a hard sphere with a square well and four point particles attached to the center of the hard sphere by directional bonds arranged in tetrahedral geometry. We also impose a condition which does not allow a point particle in one molecule to include in its attractive well more than one point particle belonging to different molecules. We find an optimal range of flexibility of the bonds created by the point particles for which the model displays a clear liquid-liquid critical point in the accessible region of the phase diagram: too flexible bonds weaken the anomalies and destroy the critical point, while too rigid bonds slow down the diffusion and shift the critical point beyond the glass transition. We also investigate how minor changes in the model parameters influence crystallization which might make liquid-liquid unobservable.

Buldyrev, Sergey; Franzese, Giancarlo; Giovambattista, Nicolas

2013-03-01

263

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

264

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

265

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

266

Accurate measurements of infinite dilution activity coefficients using gas chromatography with static-wall-coated open-tubular columns.  

PubMed

Wall-coated open-tubular (WCOT) columns provide higher column efficiency and lower solute interfacial adsorption effect than packed columns. However, previous efforts used to measure the infinite dilution activity coefficient (?(?)) via a chromatographic technique have used packed columns, because the low carrier gas flow rate (U) and the small stationary phase amount (n(2)) in WCOT columns raise large errors. By rationally revising the ?(?)-calculation equation for static-wall-coated open-tubular column, we observed that U and n(2) are not necessarily needed and the resulting error could be reduced, and WCOT column gas chromatography subsequently became a superior method for the accurate ?(?) determination. In this study, we validate our revised ?(?)-calculation equation by measuring ?(?) in an ionic liquid 1-butyl-3-methylimidazolium hexafluorophosphate system, in which 55 organic compounds covering a wide range of functional groups were used as probe solutes and their ?(?) values in the ionic liquid were determined at 40.0, 50.0, and 60.0 °C. Experimental error analysis shows that our revised equation remarkably reduces the error compared to the common ?(?)-calculation equation. Our data is consistent with previously reported values obtained via other techniques, which further proves the credibility of our revised equation. The accurately determined ?(?) values can be directly used to calculate the partial molar excess enthalpy, selectivity, and capacity, which will benefit for the rapid screening of solvents (especially ionic liquids) in separation approaches. PMID:23039405

Xu, Qianqian; Su, Baogen; Luo, Xinyi; Xing, Huabin; Bao, Zongbi; Yang, Qiwei; Yang, Yiwen; Ren, Qilong

2012-11-01

267

Linear solvation energy relationship of the limiting partition coefficient of organic solutes between water and activated carbon  

USGS Publications Warehouse

A linear solvation energy relationship has been found for 353 values of the limiting adsorption coefficients of diverse chemicals:? log K = ?0.37 + 0.0341Vi ? 1.07? + D + 0.65P with R = 0.951, s = 0.51, n = 353, and F = 818.0, where Vi is the intrinsic molar volume; ? is a measure of the hydrogen bond acceptor strength of the solute; D is an index parameter for the research group which includes the effects of the different types of carbon used, the temperature, and the length of time allowed for the adsorption equilibrium to be established; and P is an index parameter for the flatness of the molecule. P is defined to be unity if there is an aromatic system in the molecule or if there is a double bond or series of conjugated double bonds with no more that one non-hydrogen atom beyond the double bond and zero otherwise. A slightly better fit is obtained if the two-thirds power of Vi is used as a measure of the surface area in place of the volume term:? log K = ?1.75 + 0.227V2/3 ? 1.10? + D + 0.60P with R = 0.954, s = 0.49, n = 353, and F = 895.39. This is the first quantitative measure of the effect of the shape of the molecule on its tendency to be adsorbed on activated carbon.

Luehrs, Dean C.; Hickey, James P.; Nilsen, Peter E.; Godbole, K.A.; Rogers, Tony N.

1995-01-01

268

COMMERCIAL-SCALE DEMONSTRATION OF THE LIQUID PHASE METHANOL (LPMEOH) PROCESS  

SciTech Connect

This project, which was sponsored by the U.S. Department of Energy (DOE) under the Clean Coal Technology Program to demonstrate the production of methanol from coal-derived synthesis gas (syngas), has completed the 69-month operating phase of the program. The purpose of this Final Report for the ''Commercial-Scale Demonstration of the Liquid Phase Methanol (LPMEOH{trademark}) Process'' is to provide the public with details on the performance and economics of the technology. The LPMEOH{trademark} Demonstration Project was a $213.7 million cooperative agreement between the DOE and Air Products Liquid Phase Conversion Company, L.P. (the Partnership). The DOE's cost share was $92,708,370 with the remaining funds coming from the Partnership. The LPMEOH{trademark} demonstration unit is located at the Eastman Chemical Company (Eastman) chemicals-from-coal complex in Kingsport, Tennessee. The technology was the product of a cooperative development effort by Air Products and Chemicals, Inc. (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 coal gasifiers. Originally tested at the Alternative Fuels Development Unit (AFDU), a small, DOE-owned process development facility 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. The LPMEOH{trademark} Demonstration Project accomplished the objectives set out in the Cooperative Agreement with DOE for this Clean Coal Technology project. Overall plant availability (defined as the percentage of time that the LPMEOH{trademark} demonstration unit was able to operate, with the exclusion of scheduled outages) was 97.5%, and the longest operating run without interruption of any kind was 94 days. Over 103.9 million gallons of methanol was produced; Eastman accepted all of the available methanol for use in the production of methyl acetate, and ultimately cellulose acetate and acetic acid.

E.C. Heydorn; B.W. Diamond; R.D. Lilly

2003-06-01

269

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

SciTech Connect

The equilibrium-limited liquid-phase synthesis of ethyl tert-butyl ether (ETBE) from the combination of ethanol and isobutylene over an ion-exchange resin catalyst, typically Amberlyst 15, is a reaction of considerable industrial importance now. An equilibrium constant relationship is developed here for the liquid-phase ETBE reaction by following three alternative thermodynamic pathways and critically evaluating the resulting expressions. The final theoretical expression is compared against experimental data obtained in this study from the decomposition of ETBE over Amberlyst 15, as well as that reported in the literature for ETBE synthesis. It can thus be used with reasonable confidence for the calculation of the equilibrium constant, despite a dearth of thermodynamic data yet available in the literature for ETBE. In addition, an expression is derived for the gas-phase equilibrium constant and compared to experimental data from the literature. The thermodynamic approach utilized here should also be useful for other liquid-phase reaction systems.

Jensen, K.L.; Datta, R. (Univ. of Iowa, Iowa City, IA (United States). Dept. of Chemical and Biochemical Engineering)

1995-01-01

270

Double multiple-relaxation-time lattice Boltzmann model for solid-liquid phase change with natural convection in porous media  

E-print Network

In this paper, a double multiple-relaxation-time lattice Boltzmann model is developed for simulating transient solid-liquid phase change problems in porous media at the representative elementary volume scale. The model uses two different multiple-relaxation-time lattice Boltzmann equations, one for the flow field and the other for the temperature field with nonlinear latent heat source term. The model is based on the generalized non-Darcy formulation, and the solid-liquid phase change interface is traced through the liquid fraction which is determined by the enthalpy method. The model is validated by numerical simulations of conduction melting in a semi-infinite space, solidification in a semi-infinite corner, and convection melting in a square cavity filled with porous media. The numerical results demonstrate the efficiency and accuracy of the present model for simulating transient solid-liquid phase change problems in porous media.

Liu, Qing

2015-01-01

271

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

272

Liquid-phase-deposited siloxane-based capping layers for silicon solar cells  

NASA Astrophysics Data System (ADS)

We apply non-vacuum processing to deposit dielectric capping layers on top of ultrathin atomic-layer-deposited aluminum oxide (AlOx) films, used for the rear surface passivation of high-efficiency crystalline silicon solar cells. We examine various siloxane-based liquid-phase-deposited (LPD) materials. Our optimized AlOx/LPD stacks show an excellent thermal and chemical stability against aluminum metal paste, as demonstrated by measured surface recombination velocities below 10 cm/s on 1.3 ?cm p-type silicon wafers after firing in a belt-line furnace with screen-printed aluminum paste on top. Implementation of the optimized LPD layers into an industrial-type screen-printing solar cell process results in energy conversion efficiencies of up to 19.8% on p-type Czochralski silicon.

Veith-Wolf, Boris; Wang, Jianhui; Hannu-Kuure, Milja; Chen, Ning; Hadzic, Admir; Williams, Paul; Leivo, Jarkko; Karkkainen, Ari; Schmidt, Jan

2015-02-01

273

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

274

BPTI liquid-liquid phase separation monitored by light and small angle X-ray scattering.  

PubMed

In the field of protein crystallization, a better knowledge of the nucleation process is essential to control the nucleation rate, the growth and therefore the size and the quality of crystals. With that aim, it becomes clear that the important stage is the determination of the protein phase diagram. We highlighted and investigated the bovine pancreatic trypsin inhibitor (BPTI) binary liquid-liquid phase separation in 350 mM KSCN solutions as a function of temperature. We measured the low concentration part of the binodal curve using light scattering and optical microscopy. We show, from small angle X-ray scattering experiments, that the high concentrated phase sediments in the bottom of the capillary and we analysed the low concentrated phase in terms of monomers/decamers equilibrium. PMID:12351861

Grouazel, S; Perez, J; Astier, J P; Bonneté, F; Veesler, S

2002-10-01

275

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

276

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

277

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

PubMed

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

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

2006-01-01

278

Yield of H2O2 in Gas-Liquid Phase with Pulsed DBD  

NASA Astrophysics Data System (ADS)

Electric discharge in water can generate a large number of oxidants such as ozone, hydrogen peroxide and hydroxyl radicals. In this paper, a non-thermal plasma processing system was established by means of pulsed dielectric barrier discharge in gas-liquid phase. The electrodes of discharge reactor were staggered. The yield of H2O2 was enhanced after discharge. The effects of discharge time, discharge voltage, frequency, initial pH value, and feed gas were investigated. The concentration of hydrogen peroxide and ozone was measured after discharge. The experimental results were fully analyzed. The chemical reaction equations in water were given as much as possible. At last, the water containing Rhodamine B was tested in this system. The degradation rate came to 94.22% in 30 min.

Jiang, Song; Wen, Yiyong; Liu, Kefu

2014-01-01

279

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

DOEpatents

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

Elliott, Douglas C; Oyler, James

2013-12-17

280

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

281

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

282

Liquid-liquid phase transition and structure inheritance in carbon films  

PubMed Central

Molecular dynamics simulations are performed to study the cooling process of quasi-2D liquid carbon. Our results show an obvious liquid-liquid phase transition (LLPT) from the twofold coordinated liquid to the threefold coordinated liquid with the decrease of temperature, followed by a liquid-solid phase transition (LSPT). The LLPT can be regarded as the preparation stage of LSPT. During the cooling process, the chain structures firstly self-assemble into some ring structures and then aggregate into some stable islands which can further connect together to form a complete polycrystalline film. The threefold coordinated structures play an important role in the formation of atomic rings. The inheritance of the threefold coordinated structures provides essential condition to form rings and islands. PMID:24407276

He, Yezeng; Li, Hui; Jiang, Yanyan; Li, Xiongying; Bian, Xiufang

2014-01-01

283

Liquid-liquid phase transition and structure inheritance in carbon films  

NASA Astrophysics Data System (ADS)

Molecular dynamics simulations are performed to study the cooling process of quasi-2D liquid carbon. Our results show an obvious liquid-liquid phase transition (LLPT) from the twofold coordinated liquid to the threefold coordinated liquid with the decrease of temperature, followed by a liquid-solid phase transition (LSPT). The LLPT can be regarded as the preparation stage of LSPT. During the cooling process, the chain structures firstly self-assemble into some ring structures and then aggregate into some stable islands which can further connect together to form a complete polycrystalline film. The threefold coordinated structures play an important role in the formation of atomic rings. The inheritance of the threefold coordinated structures provides essential condition to form rings and islands.

He, Yezeng; Li, Hui; Jiang, Yanyan; Li, Xiongying; Bian, Xiufang

2014-01-01

284

Indication of liquid-liquid phase transition in CuZr-based melts  

NASA Astrophysics Data System (ADS)

We study the dynamic behavior of CuZr-based melts well above the liquidus temperature. The results show a discontinuous change in viscosity during cooling, which is attributed to an underlying liquid-liquid phase transition (LLPT) in these melts. The LLPT is further verified by thermodynamic response in the same temperature region. We find that the LLPT in the Cu46Zr46Al8 melt is reversible above 1350 K upon repeated heating and cooling. Based on the concept of fluid cluster in metallic melts, the reversible LLPT is attributed to the structural transition from the strongly ordered high-density liquids to the weak-local low-density liquids upon cooling.

Zhou, Chao; Hu, Lina; Sun, Qijing; Qin, Jingyu; Bian, Xiufang; Yue, Yuanzheng

2013-10-01

285

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

NASA Astrophysics Data System (ADS)

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

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

2013-03-01

286

Crystallization and phase changes in paracetamol from the amorphous solid to the liquid phase.  

PubMed

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

Sibik, Juraj; Sargent, Michael J; Franklin, Miriam; Zeitler, J Axel

2014-04-01

287

Liquid-phase exfoliation of expanded graphites into graphene nanoplatelets using amphiphilic organic molecules.  

PubMed

Graphenes with a two-dimensional lattice of carbons have been widely employed in diverse applications owing to their excellent electrical, thermal, mechanical, and gas-barrier properties. However, the frequently-used reduced graphene oxide (rGO), which is synthesized from natural graphites by strong oxidation and subsequent reduction via highly toxic components, exhibits imperfect characteristics because of remaining defect sites on its basal planes. Therefore, in this work, we present a convenient way to prepare graphene nanoplatelets (GNPs) with minimized defect sites on their basal planes employing liquid-phase exfoliation of edge-functionalized expanded graphites (EGs) with amphiphilic organic molecules. Exfoliated GNPs revealed approximately sub-7-nm-thickness and showed stable dispersibility in an organic media during 9 months. Furthermore, spray-coated GNP films presented homogeneously stacked morphologies without noticeable agglomerations. PMID:24407700

Park, Ji Sun; Yu, Lan; Lee, Churl Seung; Shin, Kwonwoo; Han, Jong Hun

2014-03-01

288

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

SciTech Connect

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

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

2000-05-15

289

Activity Coefficients of HCl in the HCl + NH4Cl + H2O Systems at 298.15 and 313.15 K  

E-print Network

a volatile component, which may migrate and contaminate the reference solutions. Recently and silver-silver chloride electrodes. Zhao et al. (1992) mea- sured the activity coefficients of HCl in the same system at 298.15 K, using cells containing H glass ISEs and silver-silver chloride electrodes

Zhang, Luzheng

290

Kalman filter for updating the coefficients of regression models. A case study from an activated sludge waste-water treatment plant  

Microsoft Academic Search

A Kalman filter was developed to overcome the problems caused by process drifting. Different types of models were used to predict response variables of an activated sludge waste-water treatment plant. These models were constructed using MLR, PCR, and PLS. The MLR-type regression coefficients were calculated for both the PCR and PLS models. After that, the Kalman filter was used to

Pekka Teppola; Satu-Pia Mujunen; Pentti Minkkinen

1999-01-01

291

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

292

Crystallization of belite–melilite clinker minerals in the presence of liquid phase  

SciTech Connect

Crystallization of belite–melilite clinker minerals was studied from the view point of a high temperature equilibrium. Ca{sub 2}SiO{sub 4}–Ca{sub 2}Al{sub 2}SiO{sub 7} and Ca{sub 2}SiO{sub 4}–Ca{sub 2}AlFeSiO{sub 7} clinkers were synthesized at 1330 °C–1650 °C. The constituent phases were determined by X-ray powder diffractometry and optical microscopy. Chemical compositions of the individual clinker minerals were determined using an electron probe microanalyzer. We established the two types of P{sub 2}O{sub 5}-bearing pseudobinary phase diagrams in the systems Ca{sub 2}SiO{sub 4}–Ca{sub 2}Al{sub 2}SiO{sub 7} at 1505 °C–1650 °C and Ca{sub 2}SiO{sub 4}–Ca{sub 2}(Al,Fe){sub 2}SiO{sub 7} at 1330 °C–1550 °C. In the latter system, the liquid phase appeared at 1390 °C, which is approximately 150 °C lower than the temperature of liquid formation in the former system. The melilite phenocrysts larger than 50 ?m were observed not only in the slowly cooled Ca{sub 2}SiO{sub 4}–Ca{sub 2}(Al,Fe){sub 2}SiO{sub 7} clinker but also in commercial belite–melilite clinkers. These crystals would be nucleated and grown from a liquid phase which was formed at relatively low temperatures.

Kurokawa, Daisuke, E-mail: daisuke_kurokawa@taiheiyo-cement.co.jp [Central Research Laboratory, Taiheiyo Cement Corporation, Chiba 285-8655 (Japan); Department of Materials Science and Engineering, Nagoya Institute of Technology, Nagoya 466-8555 (Japan); Yoshida, Hideto [Department of Earth and Planetary Science, Graduate School of Science, The University of Tokyo, Tokyo 113-0033 (Japan); Fukuda, Koichiro [Department of Materials Science and Engineering, Nagoya Institute of Technology, Nagoya 466-8555 (Japan)

2014-06-01

293

Liquid Phase Deposition of a Space-Durable, Antistatic SnO2 Coating on Kapton.  

PubMed

Polyimides are widely used in thermal blankets covering the external surfaces of spacecrafts due to their space durability and their thermo-optical properties. However, they are susceptible to atomic oxygen (AO) erosion, the main hazard of low Earth orbit (LEO), and to electrical charging. This work demonstrates that liquid phase deposition (LPD) of 100 nm of tin oxide creates a protective coating on Kapton polyimide that has good adherence and is effective in preventing AO-induced surface erosion and in reducing electrical charging. The as-deposited tin oxide induces no significant changes in the original thermo-optical properties of the polymer and is effective in preventing electrostatic discharge (ESD). The durability of the oxide coating under AO attack was studied using oxygen RF plasma. The AO exposure did not result in any significant changes in surface morphology, thermo-optical, mechanical, and electrical properties of the tin oxide-coated Kapton. The erosion yield of tin oxide-coated Kapton was negligible after exposure to 6.4 × 10(20) O atoms·cm(-2) of LEO equivalent AO fluence, indicating a complete protection of Kapton by the LPD deposited coating. Moreover, the tin oxide coating is flexible enough so that its electrical conductivity stays within the desired range of antistatic materials despite mechanical manipulations. The advantages of liquid phase deposited oxides in terms of their not being line of site limited are well established. We now extend these advantages to coatings that reduce electrostatic discharge while still providing a high level of protection from AO erosion. PMID:25607925

Gotlib-Vainstein, Katya; Gouzman, Irina; Girshevitz, Olga; Bolker, Asaf; Atar, Nurit; Grossman, Eitan; Sukenik, Chaim N

2015-02-18

294

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

SciTech Connect

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

None

1997-09-30

295

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

SciTech Connect

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

None

1997-12-31

296

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

297

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

298

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

299

Liquid-phase oxidation of cyclohexene in the presence of inhibitors and metallocomplexes chemically fixed on silica  

SciTech Connect

In an investigation of the mechanism of the liquid-phase oxidation of cyclohexene in the presence of heterogeneous catalysts, heterogeneous inhibitors - amines, ionol (BHT), the stable nitroxyl radical - were used, which made it possible to exclude the mutual influence of the sites of catalysis and inhibition. The efficiency factor was calculated for all types of inhibitors.

Berentsveig, V.V.; Barinova, T.V.; Staroverov, S.M.

1989-02-01

300

Novelties of kinetics of chemoselective reduction of citronellal to citronellol by sodium borohydride under liquid–liquid phase transfer catalysis  

Microsoft Academic Search

Borohydride reductions, although common, have not been studied from kinetic and mechanistic view points due to complex chemistry and more so, there is no report on kinetics and mechanism of such reductions under phase transfer catalysis. The novelties of phase transfer catalysed chemoselective reduction of citronellal to citronellol using sodium borohydride were studied in detail in liquid–liquid phase transfer catalysis

Ganapati D. Yadav; Sharad V. Lande

2006-01-01

301

Use of a CCD camera for the thermographic study of a transient liquid phase bonding process in steel  

Microsoft Academic Search

The bonding of steel pieces and the development of novel soldering methods, appropriate to the extended variety of applications of steels nowadays, bring the sensing of temperature an outstanding role in any metallurgical process. Transient liquid phase bonding (TLPB) processes have been successfully employed to join metals, among them steels. A thin layer of metal A, with a liquids temperature

Eduardo H. Castro; Carlos Epelbaum; Angel Carnero; Bibiana Arcondo

2001-01-01

302

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-indium 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

303

Biodegradation of azaarenes and creosote in aqueous and organic liquid phase immobilized cell bioreactors by bacteria isolated from creosote contaminated soil  

SciTech Connect

The biodegradation of azaarenes and coal-tar creosote was studied using aerobic bacteria isolated from creosote contaminated soil as inocula in batch cultures and in immobilized cell bioreactors. Biodegradation of quinoline, isoquinoline, and 6-methylquinoline by pure and mixed cultures yielded mono-hydroxylated metabolites as the primary products of azaarene metabolism. All azaarene degrading cultures could degrade quinoline, suggesting a common metabolic pathway based on quinoline metabolism. Mixed cultures attacking creosote degraded 2- and 3-ring polyaromatic hydrocarbons and heterocycles, but were unable to degrade 4- and 5-ring PAH. The degradation rate and loading capacity for quinoline was greatly enhanced in the bioreactors in comparison to batch cultures. The rates of isoquinoline, 6-methylquinoline degrading strain of Pseudomonas putida successfully removed 6-methylquinoline from solution in decane in a water-limited, non-aqueous liquid phase immobilized cell bioreactor. These experiments demonstrate the ability of environmental organisms to biodegrade several biologically active compounds under conditions suitable for bioremediation applications.

Rothenburger, S.J.

1992-01-01

304

SOLID-LIQUID PHASE TRANSFER CATALYZED SYNTHESIS OF CINNAMYL ACETATE-KINETICS AND ANALYSIS OF FACTORS AFFECTING THE REACTION IN A BATCH REACTOR  

EPA Science Inventory

The use of solid-liquid phase transfer catalysis has an advantage of carrying out reaction between two immiscible substrates, one in solid phase and the other in liquid phase, with high selectivity and at relatively low temperatures. In this study we investigated the synthesis ci...

305

Liquid-liquid phase transitions and water-like anomalies in liquids  

NASA Astrophysics Data System (ADS)

In this thesis we employ computer simulations and statistical physics to understand the origin of liquid-liquid phase transitions and their relationship with anomalies typical of liquid water. Compared with other liquids, water has many anomalies. For example the density anomaly: when water is cooled below 4 °C the density decreases rather than increases. This and other anomalies have also been found to occur in a few other one-component liquids, sometimes in conjunction with the existence of a liquid-liquid phase transition (LLPT) between a low-density liquid (LDL) and a high-density liquid (HDL). Using simple models we explain how these anomalies arise from the presence of two competing length scales. As a specific example we investigate the cut ramp potential, where we show the importance of "competition" in this context, and how one length scale can sometimes be zero. When there is a clear energetic preference for either LDL or HDL for all pressures and temperatures, then there is insufficient competition between the two liquid structures and no anomalies occur. From the simple models it also follows that anomalies can occur without the presence of a LLPT and vice versa. It remains therefore unclear if water has a LLPT that ends in a liquid-liquid critical point (LLCP), a hypothesis that was first proposed based on simulations of the ST2 water model. We confirm the existence of a LLCP in this model using finite size scaling and the Challa-Landau-Binder parameter, and show that the LLPT is not a liquid-crystal transition, as has recently been suggested. Previous research has indicated the possible existence of a LLCP in liquid silica. We perform a detailed analysis of two different silica models (WAC and BKS) at temperatures much lower than was previously simulated. Within the accessible temperature range we find no LLCP in either model, although in the case of WAC potential it is closely approached. We compare our results with those obtained for other tetrahedral liquids and conclude that insufficient "stiffness" in the Si-O-Si bond angle might be responsible for the absence of a LLCP.

Lascaris, Erik

306

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.

307

Multi-colorimetric sensor array for detection of explosives in gas and liquid phase  

NASA Astrophysics Data System (ADS)

In the framework of the research project "Xsense" at the Technical University of Denmark (DTU) we are developing a simple colorimetric sensor array which can be useful in detection of explosives like DNT, TATP, HMX, RDX and identification of reagents needed for making homemade explosives. The technology is based on an array of chemoselective compounds immobilized on a solid support. Upon exposure to the analyte in suspicion the colorimetric array changes color. Each chosen compound reacts chemo-selectively with analytes of interest. A change in a color signature indicates the presence of unknown explosives and volatile organic compounds (VOCs). We are working towards the selection of compounds that undergo color changes in the presence of explosives and VOCs, as well as the development of an immobilization method for the molecules. Digital imaging of the colorimetric array before and after exposure to the analytes creates a color difference map which gives a unique fingerprint for each explosive and VOCs. Such sensing technology can be used for screening relevant explosives in a complex background as well as to distinguish mixtures of volatile organic compounds distributed in gas and liquid phases. This sensor array is inexpensive, and can potentially be produced as single use disposable.

Kostesha, N.; Alstrøm, T. S.; Johnsen, C.; Nielsen, K. A.; Jeppesen, J. O.; Larsen, J.; Boisen, A.; Jakobsen, M. H.

2011-05-01

308

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

309

Liquid-phase epitaxy processing of RBa2Cu3O7-?  

NASA Astrophysics Data System (ADS)

The study of processing by liquid-phase epitaxy (LPE) is promising because the LPE process can provide rapid and thick film formation of RBa2 Cu3 O7-icons/Journals/Common/delta" ALT="delta" ALIGN="MIDDLE"/> (RBCO). The growth rate can reach 10 µm min-1 and films of more than 5 µm in thickness formed by the LPE process show a high critical current density of about 1 MA cm-2 . To apply this process widely, a decrease of the processing temperature is required because it gives rise to a reaction between the solution and many of the substrate materials. Film formation on yttria-stabilized ZrO2 and silver substrates, which are more reactive than other materials such as MgO or SrTiO3 , has been achieved by decreasing the temperature to below 920 °C, with the addition of BaF2 in the solution. This paper describes processing by LPE for forming RBCO films and efforts for practical application towards coated conductors and RF electronic devices.

Yamada, Y.

2000-01-01

310

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

311

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

312

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

313

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.

1998-05-01

314

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

315

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

316

Fabrication of particle dispersed inert matrix fuel based on liquid phase sintered SiC  

NASA Astrophysics Data System (ADS)

In the present work, liquid phase sintered SiC (LPS-SiC) was proposed as an inert matrix for the particle dispersed inert matrix fuel (IMF). The fuel particles containing plutonium and minor actinides were substituted with pure yttria stabilized zirconia beads. The LPS-SiC matrix was produced from the initial mixtures prepared using submicron sized ?-SiC powder and oxide additives Al 2O 3, Y 2O 3 in the amount of 10 wt.% with the molar ratio 1Y 2O 3/1Al 2O 3. Powder mixtures were sintered using two sintering methods; namely conventional high temperature sintering and novel spark plasma sintering at different temperatures depending on the method applied in order to obtain dense samples. The phase reaction products were identified using X-ray diffraction (XRD) and microstructures were investigated using light microscopy and scanning electron microscopy with energy dispersive X-ray spectroscopy (SEM/EDX) techniques. The influence of powder mixing methods, sintering temperatures, pressures applied and holding time on the density of the obtained pellets was investigated. The samples sintered by slow conventional sintering show lower relative density and more pronounced interaction between the fuel particles and matrix in comparison with those obtained with the fast spark plasma sintering method.

Pavlyuchkov, D.; Baney, R. H.; Tulenko, J. S.; Seifert, H. J.

2011-08-01

317

High-yield production of graphene by liquid-phase exfoliation of graphite  

NASA Astrophysics Data System (ADS)

Fully exploiting the properties of graphene will require a method for the mass production of this remarkable material. Two main routes are possible: large-scale growth or large-scale exfoliation. Here, we demonstrate graphene dispersions with concentrations up to ~0.01 mg ml-1, produced by dispersion and exfoliation of graphite in organic solvents such as N-methyl-pyrrolidone. This is possible because the energy required to exfoliate graphene is balanced by the solvent-graphene interaction for solvents whose surface energies match that of graphene. We confirm the presence of individual graphene sheets by Raman spectroscopy, transmission electron microscopy and electron diffraction. Our method results in a monolayer yield of ~1 wt%, which could potentially be improved to 7-12 wt% with further processing. The absence of defects or oxides is confirmed by X-ray photoelectron, infrared and Raman spectroscopies. We are able to produce semi-transparent conducting films and conducting composites. Solution processing of graphene opens up a range of potential large-area applications, from device and sensor fabrication to liquid-phase chemistry.

Hernandez, Yenny; Nicolosi, Valeria; Lotya, Mustafa; Blighe, Fiona M.; Sun, Zhenyu; de, Sukanta; McGovern, I. T.; Holland, Brendan; Byrne, Michele; Gun'ko, Yurii K.; Boland, John J.; Niraj, Peter; Duesberg, Georg; Krishnamurthy, Satheesh; Goodhue, Robbie; Hutchison, John; Scardaci, Vittorio; Ferrari, Andrea C.; Coleman, Jonathan N.

2008-09-01

318

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

319

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

320

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

321

Dynamical and structural heterogeneities close to liquid-liquid phase transitions: The case of gallium  

NASA Astrophysics Data System (ADS)

Liquid-liquid phase transitions (LLPT) have been proposed in order to explain the thermodynamic anomalies exhibited by some liquids. Recently, it was found, through molecular dynamics simulations, that liquid elemental gallium, described by a modified embedded-atom model, exhibits a LLPT between a high-density liquid (HDL) and a low-density liquid (LDL), about 60 K below the melting temperature. In this work [1], we studied the dynamics of supercooled liquid gallium close to the LLPT. Our results show a large increase in the plateau of the self-intermediate scattering function (?-relaxation process) and in the non-Gaussian parameter, indicating a pronounced dynamical heterogeneity upon the onset of the LLPT. The dynamical heterogeneity of the LDL is closely correlated to its structural heterogeneity, since the fast diffusing atoms belong to high-density domains of predominantly 9-fold coordinated atoms, whereas the slow diffusing ones are mostly in low-density domains of 8-fold coordinated atoms. The energetics suggests that the reason for the sluggish dynamics of LDL is due to its larger cohesive energy as compared to that of the HDL. [1] S. Cajahuaringa, M. de Koning, and A. Antonelli, J. Chem. Phys. 136, 064513 (2012).

Antonelli, Alex; Cajahuaringa, Samuel; de Koning, Maurice

2013-03-01

322

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

SciTech Connect

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 [Division of Materials Science and Engineering, Boston University, Brookline, Massachusetts 02446 (United States); Kim, Jaegil; Straub, John E., E-mail: straub@bu.edu [Department of Chemistry, Boston University, Boston, Massachusetts 02215 (United States); Farrell, James D.; Wales, David J. [University Chemical Laboratories, Lensfield Road, Cambridge CB2 1EW (United Kingdom)

2014-11-14

323

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

324

Analysis of Ginzburg-Landau-type models of surfactant-assisted liquid phase separation  

NASA Astrophysics Data System (ADS)

In this paper diffuse interface models of surfactant-assisted liquid-liquid phase separation are addressed. We start from the generalized version of the Ginzburg-Landau free-energy-functional-based model of van der Sman and van der Graaf. First, we analyze the model in the constant surfactant approximation and show the presence of a critical point at which the interfacial tension vanishes. Then we determine the adsorption isotherms and investigate the validity range of previous results. As a key point of the work, we propose a new model of the van der Sman/van der Graaf type designed for avoiding both unwanted unphysical effects and numerical difficulties present in previous models. In order to make the model suitable for describing real systems, we determine the interfacial tension analytically more precisely and analyze it over the entire accessible surfactant load range. Emerging formulas are then validated by calculating the interfacial tension from the numerical solution of the Euler-Lagrange equations. Time-dependent simulations are also performed to illustrate the slowdown of the phase separation near the critical point and to prove that the dynamics of the phase separation is driven by the interfacial tension.

Tóth, Gyula I.; Kvamme, Bjørn

2015-03-01

325

PAHs balance in solid and liquid phase of sewage sludge during fermentation process.  

PubMed

The results of the quantitative and qualitative analysis of PAHs both in sewage sludge and in supernatants before, during, and after methane fermentation process are presented in this paper. The investigations were carried out under laboratory scale in two series. The sludge samples originated from a municipal treatment plant. The process of fermentation was conducted using batch tests (a one-off batch supplemented with sludges). The content of 16 PAHs, listed by the US EPA, was determined using GC-MS technique. The aim of this investigation was to study changes in contribution groups of hydrocarbons (2-, 3-, 4-, 5-, and 6-ring) in relation to total concentration in PAHs. The objective of these investigations was to follow the changes in the PAHs content not only in sewage sludge (drymass) but also in supernatants (in the liquid phase), and to follow changes in concentration of PAHs during the methane fermentation process as well. The balance of PAHs load in sewage sludge and supernatants mixture was also calculated. An approximate two-fold decrease in dry matter of sludge was observed during the methane fermentation process. During sewage sludge digestion process 3- and 4-ring compounds were released from a solid phase to supernatants. PMID:18988097

W?odarczyk-Maku?a, Maria

2008-12-01

326

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

NASA Astrophysics Data System (ADS)

Gas-liquid interphase mass transfer operations, such as gas-liquid phase separation, gas absorption into liquid or dissolved gas separation from liquid, gas humidification and drying via liquid contact, and evaporative cooling are readily accomplished on the Earth with settling/spray chambers, packed towers, or bubble columns. This paper reports on gas-water mass transfer tests performed utilizing microporous hydrophobic Hollow Fiber Modules (HFMs) of the type currently employed as blood oxygenators in heart-lung machines. In these HFMs, gases are transferrred to and from water or other hydrophilic liquids through the microporous fiber walls; liquid water does not enter the pores of the highly hydrophobic wall material. The experiments included air-water phase separation, absorption of oxygen and carbon dioxide into water and separation of these dissolved gases from water, air humidification and drying by contact with temperature-controlled water, and controlled evaporation of water into a vacuum. In each of these experiments, a small, light HFM sucessfully performed the mass tranfer function, with no leakage of liquid water through the porous walls of the hollow fibers, even with high pressure across the fiber wall for extended periods of time. These results demonstrate that gas-liquid mass transfer unit operations on hydrophilic liquids, implemented with microporous hydrophobic HFM technology, are ready for use in microgravity fluid processing systems.

Noyes, Gary

327

Ionic liquids in refinery desulfurization: comparison between biphasic and supported ionic liquid phase suspension processes.  

PubMed

The desulfurization of fuel compounds in the presence of ionic liquids is reported. For this purpose, the desulfurization efficiency of a variety of imidazolium phosphate ionic liquids has been tested. Dibenzothiophene/dodecane and butylmercaptan/decane mixtures were used as model systems. Single-stage extractions reduced the sulfur content from 500 ppm to 200 ppm. In multistage extractions the sulfur content could be lowered to less than 10 ppm within seven stages. Regeneration of the ionic liquid was achieved by distillation or re-extraction procedures. Supported ionic liquid phase (SILP) materials, obtained by dispersing the ionic liquid as a thin film on highly porous silica, exhibited a significantly higher extraction performance owing to their larger surface areas, reducing the sulfur content to less than 100 ppm in one stage. Multistage extraction with these SILP materials reduced the sulfur level to 50 ppm in the second stage. The SILP technology offers very efficient utilization of ionic liquids and circumvents mass transport limitations because of the small film thickness and large surface area, and allows application of the simple packed-bed column extraction technique. PMID:19798713

Kuhlmann, Esther; Haumann, Marco; Jess, Andreas; Seeberger, Andreas; Wasserscheid, Peter

2009-01-01

328

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

329

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 Ni3S2, 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 Ni3S2 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

330

Fuel and power coproduction: The Liquid Phase Methanol (LPMEOH{trademark}) process demonstration at Kingsport  

SciTech Connect

The Liquid Phase Methanol (LPMEOH{trademark}) process uses a slurry bubble column reactor to convert syngas (primarily a mixture of carbon monoxide and hydrogen) to methanol. Because of its superior heat management, the process is able to be designed to directly handle the carbon monoxide (CO)-rich syngas characteristic of the gasification of coal, petroleum coke, residual oil, wastes, or of other hydrocarbon feedstocks. When added to an integrated gasification combined cycle (IGCC) power plant, the LPMEOH{trademark} process converts a portion of the CO-rich syngas produced by the gasifier to methanol, and the remainder of the unconverted gas is used to fuel the gas turbine combined-cycle power plant. The LPMEOH{trademark} process has the flexibility to operate in a daily electricity demand load-following manner. Coproduction of power and methanol via IGCC and the LPMEOH{trademark} process provides opportunities for energy storage for electrical demand peak shaving, clean fuel for export, and/or chemical methanol sales.

Drown, D.P.; Brown, W.R.; Heydorn, E.C.; Moore, R.B.; Schaub, E.S.; Brown, D.M.; Jones, W.C.; Kornosky, R.M.

1997-12-31

331

The Activity of Gamma Emitters as Measured by Ionization Chambers. The Determination of the Specific Gamma Emission Coefficient for Some Radioelements (thesis); MESURE DE L'ACTIVITE DES EMETTEURS GAMMA PAR CHAMBRES D'IONISATION. DETERMINATION DU COEFFICIENT SPECIFIQUE D'EMISSION GAMMA DE QUELQUES RADIOELEMENTS (thesis)  

Microsoft Academic Search

The object of this work is to study techniques of measurement using the ; gamma ionization chamber, making it possible either to measure the activities of ; radioactive sources, or to determine the specific emission coefficient gamma ; (or the coefficient K) of a given radio-element. The ionization chambers studied ; belong to two categories: graphite cavity-chambers, and 4 pi

Englemann

1962-01-01

332

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

333

Comparison of conventional hollow fiber based liquid phase microextraction and electromembrane extraction efficiencies for the extraction of ephedrine from biological fluids.  

PubMed

In the present study, hollow fiber liquid phase microextraction (HF-LPME) based on pH gradient and electromembrane extraction (EME) coupled with high-performance liquid chromatography (HPLC) was compared for the extraction of ephedrine from biological samples. The influences of fundamental parameters affecting the extraction efficiency of ephedrine were studied and optimized for both methods. Under the optimized conditions, preconcentration factors of 120 and 35 for urine and 51 and 8 for human plasma were obtained using EME and HF-LPME, respectively. The calibration curves showed good linearity for urine and plasma samples by both methods with the coefficient of estimations higher than 0.98. The limits of detection were obtained 5 and 10 ng mL(-1) using EME and 60 and 200 ng mL(-1) by HF-LPME for urine and plasma samples respectively. The relative standard deviations of the analysis were found in the range of 5.2-8.6% (n=3). The results showed that in comparison with HF-LPME based on pH gradient, EME is a much more effective transport process, providing high extraction efficiencies in very short time. PMID:22024341

Fotouhi, Lida; Yamini, Yadollah; Molaei, Saeideh; Seidi, Shahram

2011-12-01

334

Determination of phenols in environmental water samples by two-step liquid-phase microextraction coupled with high performance liquid chromatography.  

PubMed

In this work, a two-step liquid-phase microextraction (LPME) method was presented for the extraction of phenols in environmental water samples. Firstly, the polar phenol in water samples (donor phase) was transferred to 1-octanol (extraction mesophase) by magnetic stirring-assisted LPME. Subsequently, target analytes in the 1-octanol was back extracted into 0.1 mol/L sodium hydroxide solution (acceptor phase) by vortex-assisted LPME. By combination of the two-step LPME, the enrichment factors were multiplied. The main features of this two-step LPME for phenols lie in the following aspects. Firstly, the extraction can be accomplished within relatively short time (ca. 20 min). Secondly, it was compatible with HPLC analysis, avoiding derivatization step that is generally necessary for GC analysis. Thirdly, high enrichment factors (296-954 fold) could be obtained for these analytes. Under the optimized conditions, the linearities were 10-1000, 1-500, 1-500, 5-500 and 1-500 ng/mL for different phenols with all regression coefficients higher than 0.9985. The limits of detection were in the range from 0.3 to 3.0 ng/mL for these analytes. Intra-and inter-day relative standard deviations were below 7.6%, indicating a good precision of the proposed method. PMID:21962686

Zhang, Ping-Ping; Shi, Zhi-Guo; Feng, Yu-Qi

2011-10-15

335

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

336

Study on liquid-liquid phase transitions of gallium at high pressure and temperature with x-ray microtomography  

NASA Astrophysics Data System (ADS)

There are three crystalline structures for a solid state under ambient condition for gallium. Local structures in melts trend to show short range ordering within a few tenths of a nanometer, which are often considered to be correlated with the atomic arrangements of their solid counterparts. For non-crystalline samples, such as amorphous materials and melts, Due to their lack of periodicity, diffraction patterns from amorphous and liquid phases are very broad; therefore, it is challenging to obtain density information under high-pressure conditions. On the other hand, x-ray microtomography can provide density and geometry information on samples regardless of their crystallinity. Synchrotron x-ray microtomography enables us to carry out in situ density measurements on liquids at high pressures. Thus, we can address whether there are liquid-liquid phase transitions of gallium and better understand the physical processes of phase transitions.

li, R.; li, L.; Rivers, M. L.; Liu, H.

2013-12-01

337

Ab initio investigation of a possible liquid-liquid phase transition in MgSiO3 at megabar pressures  

NASA Astrophysics Data System (ADS)

We perform density functional molecular dynamics simulations of liquid and solid MgSiO3 in the pressure range of 120-1600 GPa and for temperatures up to 20,000 K in order to provide new insight into the nature of the liquid-liquid phase transition that was recently predicted on the basis of decaying laser shock wave experiments [Phys. Rev. Lett. 108 (2012) 065701]. However, our simulations did not show any signature of a phase transition in the liquid phase. We derive the equation of state for the liquid and solid phases and compute the shock Hugoniot curves. We discuss different thermodynamic functions and by explore alternative interpretations of the experimental findings.

Militzer, Burkhard

2013-03-01

338

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

339

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

340

In Situ Activation of Microcapsules  

NASA Technical Reports Server (NTRS)

Disclosed are microcapsules comprising a polymer shell enclosing two or more immiscible liquid phases in which a drug, or a prodrug and a drug activator are partitioned into separate phases. or prevented from diffusing out of the microcapsule by a liquid phase in which the drug is poorly soluble. Also disclosed are methods of using the microcapsules for in situ activation of drugs where upon exposure to an appropriate energy source the internal phases mix and the drug is activated in situ.

Morrison, Dennis R. (Inventor); Mosier, Benjamin (Inventor)

2000-01-01

341

A comparative study on liquid phase alkylation of 2-methylnaphthalene with long chain olefins using different solid acid catalysts  

Microsoft Academic Search

A comparative study has been made over a variety of solid acid catalysts, which include isopoly and heteropoly ions supported on various supports such as zirconia, titania, a large variety of zeolites and a couple of mesoporous materials for liquid phase alkylation of 2-methylnaphthalene with 1-octene. All the catalyst systems were characterized by nitrogen sorption analysis, X-ray diffraction and NH3-TPD.

Nishita Lucas; Ankur Bordoloi; Amol P. Amrute; Palraj Kasinathan; Ajayan Vinu; Walter Bohringer; Jack C. Q. Fletcher; S. B. Halligudi

2009-01-01

342

Highly sensitive and selective liquid-phase sensors based on a solvent-resistant organic-transistor platform.  

PubMed

Liquid-phase sensing of various organic solvents is performed for the first time, using a solvent-resistant organic-transistor platform. Sensors composed of a cross-linked poly(3-hexylthiophene) (P3HT)-azide co-polymer and a calixarene derivative exhibit highly sensitive and selective sensing behavior, owing to the selective binding effects of the liquid analytes with the calixarene-functionalized P3HT-azide, extending the range of their use in practical applications. PMID:25640109

Lee, Moo Yeol; Kim, Hyeong Jun; Jung, Gwan Yeong; Han, A-Reum; Kwak, Sang Kyu; Kim, Bumjoon J; Oh, Joon Hak

2015-03-01

343

Microstructure and mechanical properties of transient liquid phase bonds between NiAl and a Nickel-Base superalloy  

Microsoft Academic Search

An investigation of microstructural development in transient liquid phase bonds between the B2 type intermetallic compound NiAl and a nickel-base superalloy MM–247 is presented in this paper. The bonds discussed in the paper employed pure copper interlayers. Based on edge-on transmission electron microscopy investigations, the paper examines both microstructural development at the bond-line and the influence of bonding on the

W. F. Gale; Y. Guan

1999-01-01

344

Soot and liquid-phase fuel distributions in a newly designed optically accessible D.I. diesel engine  

SciTech Connect

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. [Sandia National Labs., Livermore, CA (United States); Espey, C. [Pennsylvania State Univ., University Park, PA (United States)

1993-10-01

345

Interphase boundary precipitation in liquid phase sintered W-Ni-Fe and W-Ni-Cu alloys  

Microsoft Academic Search

The microstructure of liquid-phase sintered, tungsten-based heavy alloys comprises a continuous network of spheroidal tungsten\\u000a single crystals embedded in a ductile, fcc matrix phase, and the integrity of the tungsten-matrix interphase boundaries established\\u000a during processing is of major importance in determining the resultant mechanical properties. A serious potential source of\\u000a embrittlement in these systems involves the precipitation of a brittle

1984-01-01

346

Reaction sintering of an Fe6 Wt Pct B48 Wt Pct Mo alloy in the presence of liquid phases  

Microsoft Academic Search

The mechanism of liquid phase sintering of an Fe-6 wt pct B-48 wt pct Mo alloy was investigated by means of thermal dilatometry,\\u000a differential thermal analysis (DTA), X-ray diffraction (XRD), and scanning electron microscopy (SEM). A fine composite microstructure\\u000a of Mo2FeB2 and ferrite was produced from powders of Fe, Mo, and FeB by a reaction sintering process involving two liquid

Tsuneyuki Ide; Teiichi Ando

1989-01-01

347

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

348

Orthogonal array design for the optimization of hollow fiber protected liquid-phase microextraction of salicylates from environmental waters  

Microsoft Academic Search

In the present study, a three phase-based hollow fiber protected liquid-phase microextraction (HF-LPME) method combined with high-performance liquid chromatography (HPLC) for the determination of salicylates in environmental waters was developed. The HF-LPME procedure was optimized by an L16(45) orthogonal array experimental design (OAD) with five factors at four levels. Under the optimal extraction condition (pHs of donor and receiving phases

Cong Zhang; Lei Ye; Li Xu

2011-01-01

349

Light Extraction Efficiency Enhancement of GaN Blue LED by Liquid-Phase-Deposited ZnO Rods  

Microsoft Academic Search

We investigate the light extraction efficiency of a GaN light-emitting diode (LED) by using liquid-phase-deposited ZnO rods at near-room temperature. Zinc nitrate and hexamethylenetetramine were used as the deposition precursors. Compared with the conventional GaN LED, the optical power output of the GaN LED with crystalline ZnO rods on its surface has about 1.6 times enhancement.

Ming-Kwei Lee; Chen-Lin Ho; Po-Chun Chen

2008-01-01

350

The effect of applied magnetic field on flow structures in liquid phase electroepitaxy—a three-dimensional simulation model  

Microsoft Academic Search

A three-dimensional numerical simulation for the liquid phase electroepitaxial growth of GaAs under a vertical stationary magnetic field was carried out. The effect of magnetic field intensity and non-uniformity on the flow field in the liquid solution was investigated. Numerical results show that the flow patterns exhibit three distinct stability characteristics: a stable flow field up to a magnetic field

Y. C. Liu; Y. Okano; S. Dost

2002-01-01

351

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

352

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

353

Transient liquid phase bonding of Cu to Cu–W composite using an electron beam energy source  

Microsoft Academic Search

This paper presents an alternative method for fabricating Cu\\/Cu–W joints suitable for electrical contacts. The process applied to join the Cu to the Cu–W composite involved using an electron beam welding machine operated in conduction mode to form a transient liquid phase at the interface from the melting of a thin Al foil. Analysis of the microstructure of the joints

M. Brochu; P. Wanjara

2007-01-01

354

High purity liquid phase epitaxial GaAs for radiation detectors  

SciTech Connect

The authors report on the growth of high purity n-GaAs using Liquid Phase Epitaxy (LPE) and the fabrication of room temperature p-i-n radiation detectors. The epilayers are grown from a Ga solvent in a graphite boat in a pure hydrogen atmosphere. Growth is started at a temperature of approximately 800 C. The best epilayers show a net-residual-donor concentration of 2 {times} 10{sup 13} cm{sup {minus}3}, confirmed by Hall effect measurements. The residual donors have been analyzed by far infrared spectroscopy and found to be sulfur and silicon. Epilayers with thicknesses of up to 120 {micro}m have been deposited on 650 {micro}m thick semi-insulating GaAs substrates and on 500 {micro}m thick n{sup +}-type GaAs substrates. The authors report the results obtained with Schottky barrier diodes fabricated from these high purity n-type GaAs epilayers and operated as X-ray detectors. The Schottky barrier contacts consisted of evaporated circular gold contacts on epilayers on n{sup +} substrates. The ohmic contacts were formed by evaporated and alloyed Ni-Ge-Au films on the back of the substrate. Several of the diodes exhibit currents of the order of 1 to 10 nA at reverse biases depleting approximately 50 {micro}m of the epilayer. This very encouraging result, demonstrating the possibility for fabricating GaAs p-i-n diodes with depletion layers in high purity GaAs instead of semi-insulating GaAs, is supported by similar results obtained by several other groups. The consequences of using high purity instead of semi-insulating GaAs will be much reduced charge carrier trapping. Diode electrical characteristics and detector performance results using {sup 55}Fe and {sup 241}Am radiation will be discussed.

Wynne, D.I.; Haller, E.E. [Lawrence Berkeley National Lab., CA (United States); [Univ. of California, Berkeley, CA (United States). Dept. of Materials Science and Mineral Engineering; Rossington Tull, C.S. [Lawrence Berkeley National Lab., CA (United States)

1998-12-31

355

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

NASA Astrophysics Data System (ADS)

Transient-liquid-phase (TLP) bonding was used to join high-strength, high-purity Al2O3 ceramic. This method uses a multilayer interlayer (B/A/B sandwich structure), which forms thin transient-liquid layers between the Al2O3 and the refractory core layer (A), then isothermally solidifies through a diffusive mechanism. The presence of thin liquid layers allow interfacial gaps and voids to be filled, while allowing bonding times comparable to those used for conventional brazing. It was shown that TLP bonding produces high-strength joints with re-melt temperatures that are significantly higher than the bonding temperatures used. This study explores the interrelationships between the processing conditions, fracture strengths of the joints, wetting behavior of the TLP, and the diffusion/isothermal solidification kinetics. In particular, when Ni/Nb/Ni interlayers were utilized, four-point bend tests revealed that the fracture strengths of the joints matched those of the monolithic Al2O3, even after a 5-min holding time at 1400°C, the bonding temperature. The resulting interlayer consists of >99% Nb, which has a melting point >2000°C. Sessile-drop wetting experiments revealed that the Ni-Nb liquid alloy formed during bonding exhibits relatively low contact angles (?90°) on Al2O3, which enables the formation of nearly flaw-free interfaces. An analytical diffusion calculation model was also used to describe the isothermal-solidification and homogenization kinetics, and will be used in future studies to aid new interlayer designs.

Hong, Sung Moo

356

Thermal Diffusivity and Thermal Conductivity of Five Different Steel Alloys in the Solid and Liquid Phases  

NASA Astrophysics Data System (ADS)

The need for characterization of thermophysical properties of steel and nickel-based alloys was addressed in the FFG-Bridge Project 810999 in cooperation with a partner from industry, Böhler Edelstahl GmbH & Co KG. To optimize numerical simulations of production processes, such as remelting or plastic deformation, additional, and more accurate data were necessary for the alloys under investigation. With a fast ohmic pulse heating circuit system, the temperature-dependent specific electrical resistivity, density, and specific heat capacity for a set of five high alloyed steels were measured. Hence, using the Wiedemann-Franz law with a Lorenz number of L =2.45× 10^{-8} {V}2{\\cdot }{K}^{-2} , the thermal diffusivity and thermal conductivity could be calculated for the solid and liquid phases up to temperatures of 2500 K. This experimental approach is limited by the following requirements for the specimens: they have to be electrically conducting, the melting point has to be high enough for the implemented pyrometric temperature measurement, and one has to be able to draw wires of the material. The latter restriction is technologically challenging with some of the materials being very brittle. For all samples, electrical and temperature signals are recorded and a fast shadowgraph method is used to measure the volume expansion. For each material under investigation, a set of data including the chemical composition, the density at room temperature, solidus and liquidus temperatures, and the change of enthalpy, resistivity, density, thermal conductivity, and thermal diffusivity as a function of temperature is reported.

Wilthan, B.; Schützenhöfer, W.; Pottlacher, G.

2015-02-01

357

Interplay of the Glass Transition and the Liquid-Liquid Phase Transition in Water  

NASA Astrophysics Data System (ADS)

Most liquids can form a single glass or amorphous state when cooled sufficiently fast (in order to prevent crystallization). However, there are a few substances that are relevant to scientific and technological applications which can exist in at least two different amorphous states, a property known as polyamorphism. Examples include silicon, silica, and in particular, water. In the case of water, experiments show the existence of a low-density (LDA) and high-density (HDA) amorphous ice that are separated by a dramatic, first-order like phase transition. It has been argued that the LDA-HDA transformation evolves into a first-order liquid-liquid phase transition (LLPT) at temperatures above the glass transition temperature Tg. However, obtaining direct experimental evidence of the LLPT has been challenging since the LLPT occurs at conditions where water rapidly crystallizes. In this talk, I will (i) discuss the general phenomenology of polyamorphism in water and its implications, and (ii) explore the effects of a LLPT on the pressure dependence of Tg(P) for LDA and HDA. Our study is based on computer simulations of two water models -- one with a LLPT (ST2 model), and one without (SPC/E model). In the absence of a LLPT, Tg(P) for all glasses nearly coincide. Instead, when there is a LLPT, different glasses exhibit dramatically different Tg(P) loci which are directly linked with the LLPT. Available experimental data for Tg(P) are only consistent with the scenario that includes a LLPT (ST2 model) and hence, our results support the view that a LLPT may exist for the case of water.

Giovambattista, Nicolas

2013-03-01

358

Automation and optimization of liquid-phase microextraction by gas chromatography.  

PubMed

Several fully automated liquid-phase microextraction (LPME) techniques, including static headspace LPME (HS-LPME) (a drop of solvent is suspended at the tip of a microsyringe needle and exposed to the headspace of the sample solution), exposed dynamic HS-LPME (the solvent is exposed in the headspace of sample vial for different time, and then withdrawn into the barrel of the syringe. This procedure is repeated a number of times), unexposed dynamic HS-LPME (the solvent is moved inside the needle and the barrel of a syringe, and the gaseous sample is withdrawn into the barrel and then ejected), static direct-immersed LPME (DI-LPME) (a drop of solvent is suspended at the tip of a microsyringe needle and directly immersed into the sample solution), dynamic DI-LPME (the solvent is moved inside the needle and the barrel of a syringe, and the sample solution is withdrawn and ejected), and two phase hollow fiber-protected LPME (HF-LPME) (a hollow fiber is used to stabilize and protect the solvent), auto-performed with a commercial CTC CombiPal autosampler, are described in this paper. Critical experimental factors, including temperature, choice of extraction solvent, solvent volume, plunger movement rate, and extraction time were investigated. Among the three HS-LPME techniques that were evaluated, the exposed dynamic HS-LPME technique provided the best performance, compared to the unexposed dynamic HS-LPME and static HS-LPME approaches. For DI-LPME, the dynamic process can enhance the extraction efficiency and the achieved method precision is comparable with the static DI-LPME technique. The precision of the fully automated HF-LPME is quite acceptable (RSD values below 6.8%), and the concentration enrichment factors are better than the DI-LPME approaches. The fully automated LPME techniques are more accurate and more convenient, and the reproducibility achieved eliminates the need for an internal standard to improve the method precision. PMID:17116305

Ouyang, Gangfeng; Zhao, Wennan; Pawliszyn, Janusz

2007-01-01

359

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

360

Development and evaluation of plunger-in-needle liquid-phase microextraction.  

PubMed

In this work, a novel, simple and fast one-step liquid-phase microextraction (LPME) approach, termed plunger-in-needle LPME was developed. In this method, the stainless steel plunger wire of a commercially available plunger-in-needle microsyringe was simply etched by immersion in hydrofluoric acid to form a microporous structure, and was used as the extractant solvent holder. The extractant solvent could be easily held within the pores created by the etching. When the plunger wire with the extractant solvent was exposed to the sample solution, analytes directly diffused from the sample solution to the solvent. After extraction, the plunger wire was directly introduced into the injection port of a gas chromatography-mass spectrometry (GC-MS) system for analysis of the analytes after thermal desorption. Polycyclic aromatic hydrocarbons (PAHs) were used as model analytes to evaluate the extraction performance of this new approach to LPME. Parameters affecting the extraction efficiency were investigated in detail. Under the optimized conditions, the method detection limits for 10PAHs were in the range of 0.003 and 0.136?g/L (at a signal/noise ratio of 3), with relative standard deviations of between 2.9% and 9.6% on the same etched plunger wire. The linearities of the calibration plots were from 0.05 to 50 or from 1 to 50?g/L, depending on the PAHs. When this method was applied for the spiked river water sample, the relative recoveries ranged from 70.1% to 106.4%. The proposed method integrates the extraction and extract introduction into one device, without extraneous sorbent needed, which makes the procedure fast and simple. It is also an environmentally friendly approach as the organic solvent consumed is almost negligible. PMID:24406144

Zhang, Hong; Ng, Benedict Wen Long; Lee, Hian Kee

2014-01-24

361

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

362

Bacterial diversity of a consortium degrading high-molecular-weight polycyclic aromatic hydrocarbons in a two-liquid phase biosystem.  

PubMed

High-molecular-weight (HMW) polycyclic aromatic hydrocarbons (PAHs) are pollutants that persist in the environment due to their low solubility in water and their sequestration by soil and sediments. Although several PAH-degrading bacterial species have been isolated, it is not expected that a single isolate would exhibit the ability to degrade completely all PAHs. A consortium composed of different microorganisms can better achieve this. Two-liquid phase (TLP) culture systems have been developed to increase the bioavailability of poorly soluble substrates for uptake and biodegradation by microorganisms. By combining a silicone oil-water TLP system with a microbial consortium capable of degrading HMW PAHs, we previously developed a highly efficient PAH-degrading system. In this report, we characterized the bacterial diversity of the consortium with a combination of culture-dependent and culture-independent methods. Polymerase chain reaction (PCR) of part of the 16S ribosomal RNA gene (rDNA) sequences combined with denaturing gradient gel electrophoresis was used to monitor the bacterial population changes during PAH degradation of the consortium when pyrene, chrysene, and benzo[a]pyrene were provided together or separately in the TLP cultures. No substantial changes in bacterial profiles occurred during biodegradation of pyrene and chrysene in these cultures. However, the addition of the low-molecular-weight PAHs phenanthrene or naphthalene in the system favored one bacterial species related to Sphingobium yanoikuyae. Eleven bacterial strains were isolated from the consortium but, interestingly, only one-IAFILS9 affiliated to Novosphingobium pentaromativorans-was capable of growing on pyrene and chrysene as sole source of carbon. A 16S rDNA library was derived from the consortium to identify noncultured bacteria. Among 86 clones screened, 20 were affiliated to different bacterial species-genera. Only three strains were represented in the screened clones. Eighty-five percent of clones and strains were affiliated to Alphaproteobacteria and Betaproteobacteria; among them, several were affiliated to bacterial species known for their PAH degradation activities such as those belonging to the Sphingomonadaceae. Finally, three genes involved in the degradation of aromatic molecules were detected in the consortium and two in IAFILS9. This study provides information on the bacterial composition of a HWM PAH-degrading consortium and its dynamics in a TLP biosystem during PAH degradation. PMID:18615233

Lafortune, Isabelle; Juteau, Pierre; Déziel, Eric; Lépine, François; Beaudet, Réjean; Villemur, Richard

2009-04-01

363

Systematic and practical solvent system selection strategy based on the nonrandom two-liquid segment activity coefficient model for real-life counter-current chromatography separation.  

PubMed

Solvent system selection is the first step toward a successful counter-current chromatography (CCC) separation. This paper introduces a systematic and practical solvent system selection strategy based on the nonrandom two-liquid segment activity coefficient (NRTL-SAC) model, which is efficient in predicting the solute partition coefficient. Firstly, the application of the NRTL-SAC method was extended to the ethyl acetate/n-butanol/water and chloroform/methanol/water solvent system families. Moreover, the versatility and predictive capability of the NRTL-SAC method were investigated. The results indicate that the solute molecular parameters identified from hexane/ethyl acetate/methanol/water solvent system family are capable of predicting a large number of partition coefficients in several other different solvent system families. The NRTL-SAC strategy was further validated by successfully separating five components from Salvia plebeian R.Br. We therefore propose that NRTL-SAC is a promising high throughput method for rapid solvent system selection and highly adaptable to screen suitable solvent system for real-life CCC separation. PMID:25818557

Ren, Da-Bing; Yi, Lun-Zhao; Qin, Yan-Hua; Yun, Yong-Huan; Deng, Bai-Chuan; Lu, Hong-Mei; Chen, Xiao-Qing; Liang, Yi-Zeng

2015-05-01

364

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

365

Liquid phase sintered composite solders for next generation thermal interface applications  

NASA Astrophysics Data System (ADS)

It is undeniable that electronics are becoming increasingly powerful and that there is continual effort towards miniaturization of these devices and thus increasing heat generation requires a new paradigm in thermal interface materials (TIM) design. This work was aimed at optimizing the processing parameters and characterizing the performance of Cu-In composite solders produced by liquid phase sintering (LPS). These composites comprise a high-melting phase (HMP) such as Cu embedded in a matrix of a low-melting phase (LMP) such as In. Copper contributes to high thermal and electrical conductivity of composites, whereas the soft In matrix helps maintain high shear compliance. This combination of high electrical/thermal conductivities and high shear compliance makes these solders suitable for a range of next-generation thermal interface material (TIM) and interconnect (IC) applications. After considering a range of compositions, a solder with 60 volume percent In was found to possess the requisite combination of high compliance and high conductivity. During the study, interfacial engineering was introduced to slow down the reaction between Cu and In, and hence further improve the performance of composite solders. A dual interfacial layer consisting of Al 2O3 and Au was used to mitigate the reaction between Cu and In. A 1 nm Al2O3 layer was used as a diffusion barrier to prohibit the inter-diffusion between Cu and In, while a 20 nm Au layer was coated on top of the ceramic Al2O3 for wetting enhancement. The dual layer increased the thermal conductivity of the solder by a factor of ˜2 while reducing the yield strength to make the solder more compliant. The effects of particle size, shape and volume fraction was also studied, and a simple model was utilized to explain the trends in the mechanical and the thermal properties. The optimized Cu-In composite solders were further used to study the performance of solder joints. Mechanical properties under shear and joint thermal resistance were measured as a function of joint thickness, thermal excursion history, and different inter-layers between solder and Cu. Minimizing interfacial contact-resistance is desired, especially when the joint thickness becomes sub-millimeter, and hence role of inter-layer on the contact-resistance was studied.

Liu, Jia

366

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

367

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

SciTech Connect

The Liquid Phase Methanol (LPMEOH) process uses a slurry bubble column reactor to convert synthesis (syngas) gas to methanol. Because of its superior heat management, the process can directly utilize the carbon monoxide (CO)-rich syngas characteristic of the gasification of coal, petroleum coke, residual oil, wastes, or other hydrocarbon feedstocks. When added to an integrated gasification combined cycle (IGCC) power plant for peak shaving, the LPMEOH process converts a portion of the CO-rich syngas produced by the gasifier to methanol, and the unconverted gas is used to fuel the gas turbine combined-cycle power plant. A 260 short tons per day LPMEOH Process Demonstration Plant has been in operation at Eastman Chemical Company's chemicals-from-coal complex in Kingsport, Tennessee since April 1997. One of the advantages of the LPMEOH Process for coproduction of electric power and methanol from coal-derived syngas is that the as-produced, stabilized (degassed) methanol product is of unusually high quality (e.g. less than 1 wt% water) which may be suitable for direct use premium fuel applications. When compared to conventional methanol synthesis processes, cost savings of $0.04 to $0.11 per gallon of methanol can be achieved in coproduction facilities. However, the suitability of the stabilized product as a fuel must be demonstrated. A product-use test program has been developed to enhance the early commercial acceptance of central clean coal technology processing facilities, coproducing electricity and methanol. The objective of this program is to demonstrate commercial market applications for the ``as produced'' or stabilized methanol as a replacement fuel and as a fuel supplement. Fuel economics will be evaluated for the ``as produced'' methanol for use in municipal, industrial, and utility applications and as fuel supplements for gasoline, diesel, and natural gas. The applications (for example, as a hydrogen source for fuel cells, and as a clean transportable, storable fuel for dispersed power) require testing of the stabilized methanol to confirm its suitability. Stabilized methanol produced at the LPMEOH Process Demonstration Plant in Kingsport is being made available to seven applications selected to participate in this study. The tests are currently on-going and the results will be presented in this paper.

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

1999-07-01

368

Liquid phase epitaxial growth of InGaAs on InP using rare-earth-treated and Paul R. Bergerb)  

E-print Network

Liquid phase epitaxial growth of InGaAs on InP using rare-earth-treated melts Wei Gaoa) and Paul R-doped InP substrates. The growths were performed by liquid phase epitaxy LPE using rare-earth-doped melts in a graphite boat. The rare-earth elements studied were Yb, Gd and Er which act as gettering agents

369

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

370

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...

371

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

EPA Science Inventory

The toxicological and regulatory communities are currently exploring the use of the free-ion-activity (FIA) model both alone and in conjunction with the biotic ligand model (BLM) as a means of reducing uncertainties in current methods for assessing metals bioavailability from aqu...

372

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

373

Calculated gamma-ray and\\/or neutron attenuation coefficients in 14 MeV neutron activation analysis  

Microsoft Academic Search

A program of theoretical and experimental work was performed to develop a mathematical model which can represent all the parameters\\u000a of the neutron activation analysis operation. However, we avoid absolute technique by using a sample containing the same element\\u000a as the reference but having a different geometry and weight. In the present work we apply this model to determine the

A. G. Elayi

1983-01-01

374

The effect of melt composition on trace element partitioning: an experimental investigation of the activity coefficients of FeO, NiO, CoO, MoO2 and MoO3 in silicate melts  

Microsoft Academic Search

The thermodynamic theory describing the partitioning of trace elements between crystals and silicate melt implies that partition coefficients should depend on the major-element composition of the melt from two different causes, namely (1) the activity coefficient of the trace-element oxide component in the melt, and (2) the activities of all the major-element components needed to balance the trace-element substitution in

C. O'Neill; Stephen M. Eggins

2002-01-01

375

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

376

An Estimate for the Deviation from the Mirros Image Due to Solid Liquid Phase Transition of Metals at Shock Unloading.  

NASA Astrophysics Data System (ADS)

We extend the underlying physical reasoning of Walsh and Christian (1955) in a manner which allows a reasonable estimation for the excepted deviation from the mirror image approximation due to solid liquid phase transition. This estimated is limited to a phase transition that occurs at the unloading phase in metals such as Tin and Lead. The idea underlying this estimate is the accumulation of various contributions to the entropy and an estimation of the expected expansion at atmospheric pressure. These estimates combined with the Lindmann melting law and the Clausius Clyperon equation are used to estimate the expansion at the phase transition and the resulting change in free surface velocity.

Pistinner, Shlomi; Peker, Sharon; Werdiger, Meir; Eliezer, Shalom

2007-06-01

377

A solid-liquid diffusion model for growth and dissolution of ternary alloys by liquid phase epitaxy  

NASA Astrophysics Data System (ADS)

This paper presents a solid-liquid diffusion model for ternary alloys formed by liquid phase epitaxy (LPE). A fully numerical procedure is developed to simulate the growth and dissolution processes. The simulation results for the Al?Ga?As system show that the growth rate and the solid composition are functions of the growth temperature and the cooling rate. The computed solid composition and growth thickness are compared with available experimental data. The numerical and experimental results are in good agreement. The computational model developed in this study is suitable for simulations of solution growth of ternary alloys.

Kimura, M.; Qin, Z.; Dost, S.

1996-01-01

378

Calorimetric determination of the thermodynamic behavior of reversible liquid-phase reactions for use in energy storage  

SciTech Connect

A new calorimetric method of determining equilibrium mole fractions of labile species that participate in reversible, liquid-phase reactions has been developed. This technique relies on the fact that a reactant-solvent mixture of just the right composition will shift the equilibrium neither to the left nor to the right and thus will neither absorb nor generate heat when injected into an equilibrium mixture. Using the open-system energy balance, initial mole fraction valves for each constituent, and the experimentally determined composition of the reactant-solvent mixture which causes no reaction, the equilibrium mole fraction of each constituent can be determined.

Thompson, P.F.

1983-01-01

379

Application of single ion activity coefficients to determine solvent extraction mechanism for components of high level nuclear waste  

SciTech Connect

The TRUEX solvent extraction process is being developed to remove and concentrate transuranic (TRU) elements from high-level and TRU radioactive wastes currently stored at US Department of Energy sites. Phosphoric acid is one of the chemical species of concern at the Hanford site where bismuth phosphate was used to recover plutonium. The mechanism of phosphoric acid extraction with TRUEX-NPH solvent at 25{degrees}C was determined by phosphoric acid distribution ratios, which were measured by using phosphoric acid radiotracer and a variety of aqueous phases containing different concentrations of nitric acid and nitrate ions. A model was developed for predicting phosphoric acid distribution ratios as a function of the thermodynamic activities of nitrate ion and hydrogen ion. The Generic TRUEX Model (GTM) was used to calculate these activities based on the Bromley method. The derived model supports CMPO and TBP extraction of a phosphoric acid-nitric acid complex and a CMPO-phosphoric acid complex in TRUEX-NPH solvent.

Nunez, L.; Vandegrift, G.F.

1995-12-31

380

[Determination of seven phenoxyacid herbicides in environmental water by high performance liquid chromatography coupled with three phase hollow fiber liquid phase microextraction].  

PubMed

A novel method for the simultaneous determination of seven phenoxyacid herbicides such as dicamba, fluroxypyr, 4-chlorophenoxyacetic acid (4-CPA), 2-methyl-4-chlorophenoxyacetic acid (MCPA), 2, 4-dichlorophenoxyacetic acid (2,4-D), 2,4-dichlorophenoxybutyric acid (2,4-DB) and 4-(2-methyl-4-chlorophenoxy) butyric acid (MCPB) in environmental water by three phase hollow fiber liquid phase microextraction (HF-LPME) coupled with high performance liquid chromatography (HPLC) was developed. In order to optimize the experimental conditions, the orthogonal test has been used. The effects of extraction solvent, pH of the donor phase and acceptor phase, extraction time, stirring speed and salt concentration on the detection were investigated. The optimal experimental conditions were as follows: octanol as organic solvent, pH 3 of donor phase, pH 12 of acceptor phase, extraction time of 30 min, stirring speed of 400 r/min. The results showed that the proposed method provided a wide linear range for 7 phenoxyacid herbicides with correlation coefficients of 0.995 3 - 0.998 8. The detection limits ranged from 0.2 to 1.0 microg/L. The enrichment factors were in the range of 76.7 - 121. The recoveries were in the range of 68% - 104% and the relative standard deviations (RSDs) were less than 8.1% for the environmental water samples. The method has the advantages of sensitivity, simplicity, fastness and the use of very small amounts of organic solvent. The method can meet the requirements of the determination of trace phenoxyacid herbicides in the environmental water samples, and the study provided a useful method for the analysis of trace substances in water samples. PMID:22500447

Peng, Xiaojun; Pang, Jinshan; Deng, Aihua

2011-12-01

381

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

382

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

383

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

384

Liquid-phase explosive crystallization of electron-beam-evaporated a-Si films induced by flash lamp annealing  

NASA Astrophysics Data System (ADS)

We succeed in the formation of micrometer-order-thick polycrystalline silicon (poly-Si) films through the flash-lamp-induced liquid-phase explosive crystallization (EC) of precursor a-Si films prepared by electron-beam (EB) evaporation. The velocity of the explosive crystallization (vEC) is estimated to be ˜14 m/s, which is close to the velocity of the liquid-phase epitaxy (LPE) of Si at a temperature around the melting point of a-Si of 1418 K. Poly-Si films formed have micrometer-order-long grains stretched along a lateral crystallization direction, and X-ray diffraction (XRD) and electron diffraction pattern measurements reveal that grains in poly-Si films tend to have a particular orientation. These features are significantly different from our previous results: the formation of poly-Si films containing randomly-oriented 10-nm-sized fine grains formed from a-Si films prepared by catalytic chemical vapor deposition (Cat-CVD) or sputtering. One possible reason for the emergence of a different EC mode in EB-evaporated a-Si films is the suppression of solid-phase nucleation (SPN) during Flash Lamp Annealing (FLA) due to tensile stress which precursor a-Si films originally hold. Poly-Si films formed from EB-evaporated a-Si films would contribute to the realization of high-efficiency thin-film poly-Si solar cells because of large and oriented grains.

Ohdaira, Keisuke; Matsumura, Hideki

2013-01-01

385

Surfactant enhanced liquid-phase microextraction of basic drugs of abuse in hair combined with high performance liquid chromatography.  

PubMed

The aim of this study was to evaluate the performance of a technique for simultaneous testing of hydrophilic abuse drugs in hair. The analysis of, codeine and methadone in morphine hair included incubation in methanol (5h, 50 degrees C), Surfactant enhanced liquid-phase microextraction (SE-LPME) and HPLC analysis. This study has demonstrated that SE-LPME constitute a real alternative to the other liquid-phase microextraction methods, for pre-concentration and extraction of hydrophilic drugs in biological samples and has shown the advantages of these optimized methodologies over the traditional microextraction techniques. For these drugs recoveries in the range of 57.5-93.7 were obtained from hair. The drugs were enriched by a factor of 61-128 during SE-LPME. Linearity (r2, 0.9982-0.9997) was obtained in the range of 50-500 microg/l for morphine and 10-500 microg/l for codeine and methadone. PMID:16257282

Sarafraz Yazdi, Ali; Es'haghi, Zarrin

2005-11-11

386

A study of the transient liquid phase bonding process applied to a Ag/Cu/Ag sandwich joint  

NASA Astrophysics Data System (ADS)

Transient liquid phase (TLP) bonding is a process currently used for joining heat resistant alloys, for example nickel- and cobalt-based superalloys. It involves the formation of a liquid layer between two adjoining pieces and the formation of a solid bond as the liquid disappears during annealing at a suitable constant temperature. In the present study, a model Ag/Cu/Ag sandwich joint associated with a simple eutectic phase diagram was used to study the different stages of this process. The results confirm that the TLP bonding is a diffusional process occurring in clearly distinctive stages. The two most important stages are the widening and homogenization of the previously dissolved liquid interlayer, and the subsequent solidification and shrinking of the interlayer. Whereas the former stage involves diffusional processes both in the liquid phase and in the adjoining solids, the latter is controlled mainly by the diffusion in the solid phase. A modeling approach has been explored which shows that in most eutectic systems there exists an optimal bonding temperature corresponding to the shortest time needed for complete solidification. The results of a study on a Ag/Ag-20 wt pct Cu/Ag sandwich joint provide evidence that the use of an alloy close to the eutectic composition as an interlayer material shortens the TLP process substantially.

Tuah-Poku, Isaac; Dollar, M.; Massalski, T. B.

1988-03-01

387

Evidence for a simple monatomic ideal glass former: the thermodynamic glass transition from a stable liquid phase.  

PubMed

Under cooling, a liquid can undergo a transition to the glassy state either as a result of a continuous slowing down or by a first-order polyamorphous phase transition. The second scenario has so far always been observed in a metastable liquid domain below the melting point where crystalline nucleation interfered with the glass formation. We report the first observation of the liquid-glass transition by a first-order polyamorphous phase transition from the equilibrium stable liquid phase. The observation was made in a molecular dynamics simulation of a one-component system with a model metallic pair potential. In this way, the model, demonstrating the thermodynamic glass transition from a stable liquid phase, may be regarded as a candidate for a simple monatomic ideal glass former. This observation is of conceptual importance in the context of continuing attempts to resolve the long-standing Kauzmann paradox. The possibility of a thermodynamic glass transition from an equilibrium melt in a metallic system also indicates a new strategy for the development of bulk metallic glass-forming alloys. PMID:21054046

Elenius, Måns; Oppelstrup, Tomas; Dzugutov, Mikhail

2010-11-01

388

Removal of carbon, nitrogen and phosphorus from the separated liquid phase of hog manure by the multi-zone BioCAST technology.  

PubMed

The removal of chemical oxygen demand (COD), total nitrogen (TN) and total phosphorus (TP) at concentrations of 960 ± 38 to 2400 ± 96 mg/L, 143 ± 9 to 235 ± 15 mg/L and 25 ± 2 to 57 ± 4 mg/L, respectively, from the separated liquid phase of hog manure by the multi-zone BioCAST technology is discussed. Despite the inhibitory effect of hog waste toward microbial activities, removal efficiencies up to 89.2% for COD, 69.2% for TN and 47.6% for TP were obtained during 185 d of continuous operation. The free ammonia inhibition was postulated to be responsible for the steady reduction of COD and TP removal with the increase of TN/TP ratio from 3.6 to 5.8. On the contrary, the increase of COD/TN ratio from 4.8 to 14.1 improved the removal of all contaminants. Nitrogen removal did not show any dependence on the COD/TP ratio, despite the steady increase of COD and TP removal with this ratio in the range of 19.3-50.6. The removal efficiencies of organic and inorganic contaminants increased progressively owing to the adaptation of microbial biomass, resulting from the presence of suspended biomass in the mixed liquor that circulated continuously between the three zones of aerobic, microaerophilic and anoxic, as well as the attached biomass immobilized inside the aerobic zone. PMID:23643960

Yerushalmi, Laleh; Alimahmoodi, Mahmood; Afroze, Niema; Godbout, Stephane; Mulligan, Catherine N

2013-06-15

389

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

2015-04-01

390

Binding of complement proteins C1q and C4bp to serum amyloid P component (SAP) in solid contra liquid phase.  

PubMed

Serum amyloid P component (SAP), a member of the conserved pentraxin family of plasma proteins, binds calcium dependently to its ligands. The authors investigated SAPs interaction with the complement proteins C4b binding protein (C4bp) and C1q by ELISA, immunoelectrophoresis and electron microscopy. Binding of these proteins to SAP was demonstrated when SAP was immobilized using F(ab')2 anti-SAP, but not when SAP reacted with these proteins in liquid phase; thus the binding to human SAP was markedly phase state dependent. Presaturation of solid phase SAP with heparin, which binds SAP with high affinity, did not interfere with the subsequent binding of C4bp or C1q to SAP. In contrast, collagen I and IV showed partial competition with the binding of C1q to SAP. Using fresh serum, immobilized native SAP bound C4bp whereas binding of C1q/C1 could not be demonstrated. Altogether the results indicate that firm binding of C1q and C4bp to SAP requires that SAP is presented on a solid phase, that C1q and C4bp react with sites distinct from the heparin binding site, and that C1q and collagen I share binding sites on SAP. Immobilized native SAP, aggregated SAP and SAP-heparansulphate complexes induced no detectable complement activation. PMID:8845035

Sørensen, I J; Nielsen, E H; Andersen, O; Danielsen, B; Svehag, S E

1996-10-01

391

Calculation of activity coefficients from a novel numerical solution of the Poisson-Boltzmann equation and application to 23Na NMR of sodium polystyrene sulfonate  

NASA Astrophysics Data System (ADS)

Interaction of sodium cations with polystyrene sulfonate (PSS) is studied. The Poisson-Boltzmann equation, modified in order to incorporate ion-ion correlation, is solved numerically using a cell model. Outstanding agreement is found between the calculated and measured activity coefficients ?± for systems consisting of NaPSS+NaCl, KPSS+KCl, CaPSS+CaCl2, and the more complex system, the quarternary mixture NaPSS+CaPSS+NaCl+CaCl2. A complementary study by sodium-23 NMR provides a reliable estimate of the fractions of bound, atmospherically condensed, and free sodium ions for NaPSS in the presence of added NaCl, HCl, MgCl2, and MnCl2. We find a nice correlation (? = 0.93, N = 16) between the observed 23Na line broadenings and the calculated electrostatic field gradients for these various cases.

Delville, Alfred; Gilboa, Haggai; Laszlo, Pierre

1982-08-01

392

The CPA Equation of State and an Activity Coefficient Model for Accurate Molar Enthalpy Calculations of Mixtures with Carbon Dioxide and Water/Brine  

E-print Network

Thermodynamic property calculations of mixtures containing carbon dioxide (CO$_2$) and water, including brines, are essential in theoretical models of many natural and industrial processes. The properties of greatest practical interest are density, solubility, and enthalpy. Many models for density and solubility calculations have been presented in the literature, but there exists only one study, by Spycher and Pruess, that has compared theoretical molar enthalpy predictions with experimental data. In this report, we recommend two different models for enthalpy calculations: the CPA equation of state by Li and Firoozabadi, and the CO$_2$ activity coefficient model by Duan and Sun. We show that the CPA equation of state, which has been demonstrated to provide good agreement with density and solubility data, also accurately calculates molar enthalpies of pure CO$_2$, pure water, and both CO$_2$-rich and aqueous (H$_2$O-rich) mixtures of the two species. It is applicable to a wider range of conditions than the Spy...

Myint, P C; Firoozabadi, A

2015-01-01

393

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

394

Effective interaction potentials for alkali and alkaline earth metal ions in SPC/E water and prediction of mean ion activity coefficients.  

PubMed

The potential of mean force (PMF) acting between two simple ions surrounded by SPC/E water have been determined by molecular dynamics (MD) simulations using a spherical cavity approach. Such effective ion-ion potentials were obtained for Me-Me, Me-Cl-, and Cl(-)-Cl- pairs, where Me is a Li+, Na+, K+, Mg2+, Ca2+, Sr2+, and Ba2+ cation. The ionic sizes estimated from the effective potentials are not pairwise additive, a feature in the frequently used primitive model for electrolytes. The effective potentials were used in Monte Carlo (MC) simulations with implicit water to calculate mean ion activity coefficients of LiCl, NaCl, KCl, MgCl2, CaCl2, SrCl2, and BaCl2. Predicted activities were compared with experimental ones in the electrolyte concentration range 0.1-1 M. A qualitative agreement for LiCl and a satisfactory agreement for NaCl were found, whereas the predictions for KCl by two K+ models were less coherent. In the case of alkaline earth metal ions, all experimental activities were successfully reproduced at c = 0.1 M. However, at higher concentrations, similar deviations occurred for all divalent cations, suggesting that the dependence of the permittivity on the salt concentration and the polarization deficiency arising from the ordering of water molecules in the ion hydration shells are important in such systems. PMID:16771340

Gavryushov, Sergei; Linse, Per

2006-06-01

395

Rapid determination of partition coefficients between n-octanol/water for cardiovascular therapies.  

PubMed

The lipid solubility of a pharmaceutical may greatly influence its tissue activity. To evaluate lipid solubility of a group of cardiovascular agents a procedure to determine partition coefficients in n-octanol/water for a series of cardiovascular compounds was described. Ultraviolet absorbance measurements were used to assess partitioning between the two liquid phases of these compounds. In this study, sotalol was found to be the most hydrophilic (n-octanol/water ratio of 0.33) and fosinopril-sodium was the most lipophilic (ratio of 6.19). This is a versatile method permitting the evaluation of lipophilicity and, thus, parameters governing the events leading to pharmacologic actions such as gastrointestinal dissolution, absorption, and bioavailability. These observations can be related to a drug series, composed of several compounds having structural similarities or minor variations. The lipid solubility of a compound can markedly alter its side-effects profile, especially because lipophilic drugs enter the central nervous system with facility. Additionally, lipophilic agents may enter target tissue with greater ease than nonlipophilic compounds and thus possess local intracellular effects in addition to a macro systemic action. PMID:11782815

Ranade, Vasant; Somberg, John C

2002-01-01

396

Modeling, design, packing and experimental analysis of liquid-phase shear-horizontal surface acoustic wave sensors  

NASA Astrophysics Data System (ADS)

Recent advances in microbiology, computational capabilities, and microelectromechanical-system fabrication techniques permit modeling, design, and fabrication of low-cost, miniature, sensitive and selective liquid-phase sensors and lab-on-a-chip systems. Such devices are expected to replace expensive, time-consuming, and bulky laboratory-based testing equipment. Potential applications for devices include: fluid characterization for material science and industry; chemical analysis in medicine and pharmacology; study of biological processes; food analysis; chemical kinetics analysis; and environmental monitoring. When combined with liquid-phase packaging, sensors based on surface-acoustic-wave (SAW) technology are considered strong candidates. For this reason such devices are focused on in this work; emphasis placed on device modeling and packaging for liquid-phase operation. Regarding modeling, topics considered include mode excitation efficiency of transducers; mode sensitivity based on guiding structure materials/geometries; and use of new piezoelectric materials. On packaging, topics considered include package interfacing with SAW devices, and minimization of packaging effects on device performance. In this work novel numerical models are theoretically developed and implemented to study propagation and transduction characteristics of sensor designs using wave/constitutive equations, Green's functions, and boundary/finite element methods. Using developed simulation tools that consider finite-thickness of all device electrodes, transduction efficiency for SAW transducers with neighboring uniform or periodic guiding electrodes is reported for the first time. Results indicate finite electrode thickness strongly affects efficiency. Using dense electrodes, efficiency is shown to approach 92% and 100% for uniform and periodic electrode guiding, respectively; yielding improved sensor detection limits. A numerical sensitivity analysis is presented targeting viscosity using uniform-electrode and shear-horizontal mode configurations on potassium-niobate, langasite, and quartz substrates. Optimum configurations are determined yielding maximum sensitivity. Results show mode propagation-loss and sensitivity to viscosity are correlated by a factor independent of substrate material. The analysis is useful for designing devices meeting sensitivity and signal level requirements. A novel, rapid and precise microfluidic chamber alignment/bonding method was developed for SAW platforms. The package is shown to have little effect on device performance and permits simple macrofluidic interfacing. Lastly, prototypes were designed, fabricated, and tested for viscosity and biosensor applications; results show ability to detect as low as 1% glycerol in water and surface-bound DNA crosslinking.

Pollard, Thomas B

397

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

398

Diffusion coefficients for hydrogen sulfide, carbon dioxide, and nitrous oxide in water over the temperature range 293--368 K  

SciTech Connect

Acid gases such as H[sub 2]S and CO[sub 2] are generally removed from natural gas, biogas, synthetic natural gas, and other process gas streams by means of absorption into aqueous alkanolamine solutions. A key parameter needed to model this diffusion with chemical reaction process in the liquid phase is the diffusion coefficient. A wetted-sphere absorption apparatus was used to measure the liquid-phase diffusion coefficients for hydrogen sulfide, carbon dioxide, and nitrous oxide over the temperature range 293--368 K. The experimental results obtained in this work are compared with values in the literature and with predictions from the Wilke-Chang equation. The data presented here extend the temperature range of reported diffusivities for these gases in water.

Tamimi, A.; Rinker, E.B.; Sandall, O.C. (Univ. of California, Santa Barbara, CA (United States). Chemical and Nuclear Engineering Dept.)

1994-04-01

399

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

400

Bioconversion of N-octane to octanoic acid by a recombinant Escherichia coli cultured in a two-liquid phase bioreactor  

SciTech Connect

The alk genes from the catabolic OCT plasmid of Pseudomonas oleovorans, which encode the enzymes involved in the oxidation of n-alkanes to carboxylic acids, were introduced into E. coli W3110. The resulting recombinant converts n-octane in a two-liquid phase medium into the corresponding alkanoate and excretes this compound into the aqueous phase. The rate of octanoic acid production by the recombinant E. coli is equal to or better than the alkane oxidation rate of P. oleovorans, suggesting that two-liquid phase fermentations with E. coli might have future industrial applications.

Favre-Bulle, O.; Schouten, T.; Kingma, J.; Witholt, B. (Univ. of Groningen (Netherlands))

1991-04-01

401

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

402

The {alpha}-particle excited scintillation response of the liquid phase epitaxy grown LuAG:Ce thin films  

SciTech Connect

Liquid phase epitaxy grown Lu{sub 3}Al{sub 5}O{sub 12}:Ce (LuAG:Ce) 20 {mu}m thick films and plate cut from the bulk Czochralski-grown LuAG:Ce crystal were prepared for comparison of photoelectron yield (PhY) and PhY dependence on shaping time (0.5-10 {mu}s). {sup 241}Am ({alpha} particles) was used for excitation. At the 0.5 {mu}s shaping time, the best film shows comparable PhY with the bulk sample. PhY of bulk material increases noticeably more with shaping time than that of the films. Energy resolution of films is better. Influence of Pb{sup 2+} contamination in the films (from the flux) and antisite Lu{sub Al} defect in bulk material is discussed.

Prusa, P.; Cechak, T.; Mares, J. A.; Nikl, M.; Beitlerova, A.; Solovieva, N.; Zorenko, Yu. V.; Gorbenko, V. I.; Tous, J.; Blazek, K. [Faculty of Nuclear Sciences and Physical Engineering, Czech Technical University in Prague, Brehova 7, 11519 Prague (Czech Republic); Institute of Physics AS CR, Cukrovarnicka 10, 16253 Prague (Czech Republic); Laboratory of Optoelectronic Materials, Ivan Franko National University of Lviv, 107 Gen. Tarnavskyj Str., 79017 Lviv (Ukraine); Crytur Ltd., Palackeho 175, 51101 Turnov (Czech Republic)

2008-01-28

403

New impurity-induced defect in heavily zinc-doped GaAs grown by liquid phase epitaxy  

NASA Astrophysics Data System (ADS)

The electrical and photoluminescence properties of heavily doped GaAs:Zn(100) layers grown by liquid phase epitaxy from gallium and bismuth solutions at various temperatures have been studied. It is shown that a new line at 1.35 eV appears in low-temperature photoluminescence spectra of the layers doped at a level over 0268-1242/13/10/012/img1. It is found that this line is associated with a novel defect. The concentration of defects increases with the doping level proportionally to the concentration of free holes to the power 0268-1242/13/10/012/img2. The exponent is independent of the growth solution used (gallium or bismuth) and growth temperature. It has been found that the defect is a neutral complex consisting of native point defects of GaAs - an antisite defect of gallium in an arsenic site and two arsenic vacancies.

Shamirzaev, T. S.; Zhuravlev, K. S.; Yakusheva, N. A.; Petrenko, I. P.

1998-10-01

404

High-quality single-crystal Ge on insulator by liquid-phase epitaxy on Si substrates  

NASA Astrophysics Data System (ADS)

Ge on insulator (GOI) is desired to obtain metal-oxide-semiconductor transistors with high performance and low leakage current. We have developed a method to make GOI based on liquid-phase epitaxial (LPE) growth on Si substrates and a defect necking technique in which defects are confined to a very short distance. Self-aligned microcrucibles were used to hold the Ge liquid. High-quality single-crystal (100) as well as (111) oriented GOI structures were obtained with a process compatible with Si-based fabrication. No dislocations or stacking faults were found in the LPE Ge films on insulator. The orientation of the Ge crystals was controlled by the seeding Si substrate. This method opens up the possibility of integrating Ge device structures in a baseline Si integrated circuit process.

Liu, Yaocheng; Deal, Michael D.; Plummer, James D.

2004-04-01

405

Vulcanization reaction of squalene and S8 powder studied by Sulfur K-edge NEXAFS under liquid phase  

NASA Astrophysics Data System (ADS)

Vulcanized rubber materials are useful in our surroundings. However, detail structure and reaction are not revealed even in present. Since squalene molecule possesses some same properties compared with natural rubber, we have prepared the samples of vulcanized squalene at 140 °C for several hours. To understand the vulcanization reaction,sulfur K-edge NEXAFS measurements have been carried out for the vulcanized squalene under liquid phase with He-path system and fluorescence detection mode. Moreover, we have tried curve fitting analysis of NEXAFS spectra. The results indicate that the squalene has been vulcanized by the S8 molecule at 140 °C and the S8 molecule length is shortened from 8 to 5-6 after the vulcanization reaction.

Yagi, S.; Menjo, Y.; Tsukada, C.; Ogawa, S.; Kutluk, G.; Namatame, H.; Taniguchi, M.

2015-03-01

406

Effect of water presence on methyl tert-butyl ether and ethyl tert-butyl ether liquid-phase syntheses  

SciTech Connect

Equilibrium constants for the liquid-phase synthesis of methyl tert-butyl ether (MTBE) and ethyl tert-butyl ether (ETBE) were determined experimentally in the temperature range 40-80 C, using an initial water percentage range in the alcohol of 1.4-5 wt%. The initial molar alcohol-isobutylene ratio varied from 0.8 to 1.44. Both systems behave nonideally, and the equilibrium constants found agree with those determined without initial water quoted in the literature. In experimental kinetic runs performed at 40 C, ETBE and MTBE production rates are strongly lowered by the initial water presence. This inhibitor effect disappears as water is converted into tert-butyl alcohol (TBA). The TBA equilibrium is reached faster than those of the ethers, and the residual water is rather small.

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

1993-03-01

407

Highly luminescent undoped and Mn-doped ZnS nanoparticles by liquid phase pulsed laser ablation  

NASA Astrophysics Data System (ADS)

In this paper we report the synthesis of highly luminescent ZnS and Mn-doped ZnS nanoparticles with uniform particle size distribution by liquid phase pulsed laser ablation. The formation of nanosized ZnS crystallites was confirmed by high-resolution transmission electron microscopy (HRTEM) images. The optical properties of these nanoparticles were studied by room temperature photoluminescence (PL) spectra. The PL emission from the ZnS nanoparticles shows a sharp peak in the UV region (334 nm) corresponding to the band edge and a broad peak in the visible region which can be attributed to the sulphur vacancies, cation vacancies and surface states in the nanocrystals. The yellow emission from the Mn-doped ZnS nanoparticles can be attributed to the radiative transition between 4T1 and 6A1 levels within the 3d5 orbital of Mn2+.

Aneesh, P. M.; Shijeesh, M. R.; Aravind, Arun; Jayaraj, M. K.

2014-09-01

408

Free-Surface Optical Scattering as an Indicator of the Shock-Induced Solid-Liquid Phase Transition 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. A familiar manifestation of this phenomenon is the loss of signal light in VISAR measurements, which 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 indication of the solid-liquid phase transition. Data will be presented that support the hypothesis that specularity changes indicate melt in a way that can be measured easily and unambiguously.

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

2008-07-01

409

Photoluminescences from Al{sub x}Ga{sub 1{minus}x}P liquid phase epitaxial layers  

SciTech Connect

Homogenous Al{sub x}Ga{sub 1{minus}x}P liquid phase epitaxial layers have been obtained with the temperature difference method under controlled vapor pressure (TDM-CVP). Very clear fine structures near band edge in photoluminescence spectra have been observed at 77 K for the first time. Photoluminescence measurement results confirmed that the free exciton recombination without phonon assistance plays an important role in the luminescence at 77 K and becomes dominant at room temperature. It is considered that Zero-phonon assisted free exciton recombination is intensified by some local perturbations to electrical potentials against carriers or excitons introduced by Al atoms in Al{sub x}Ga{sub 1{minus}x}P layers, which can give momentum change necessary for recombination.

Yu, T.J.; Matsuo, T.; Suto, K.; Nishizawa, J.

1999-10-01

410

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

411

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

412

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

413

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

414

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

415

Commercial-scale demonstration of the Liquid Phase Methanol (LPMEOH{sup trademark}) process. Third quarterly report, 1996  

SciTech Connect

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

NONE

1997-09-01

416

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 for the Synthesis of Dimethyl Ether (DME) and Alternative Fuels in the Liquid Phase from Coal- Derived Syngas, the single-step, slurry phase DME synthesis process was developed. The development involved screening of catalyst systems, process variable studies, and catalyst life studies in two 300 ml stirred autoclaves. As a spin-off of the Liquid Phase Methanol (LPMEOH*) process, the new process significantly improves the syngas conversion efficiency of the LPMEOH process. This improvement can be achieved by replacing a portion of methanol catalyst with a dehydration catalyst in the reactor, resulting in the product methanol being converted to DME, thus avoiding the thermodynamic equilibrium constraint of the methanol reaction. Overall, this increases syngas conversion per-pass. The selectivity and productivity of DME and methanol are affected by the catalyst system employed as well as operating conditions. A preferred catalyst system, consisting of a physical mixture of a methanol catalyst and a gamma alumina, was identified. An improvement of about 50% in methanol equivalent productivity was achieved compared to the LPMEOH process. Results from the process variable study indicate that higher pressure and CO[sub 2] removal benefit the process significantly. Limited life studies performed on the preferred catalyst system suggest somewhat higher than expected deactivation rate for the methanol catalyst. Several DME/methanol mixtures were measured for their key properties as transportation fuels. With small amounts of DME added, significant improvements in both flash points and Reid Vapor Pressure (RVP) were observed over the corresponding values of methanol alone.

Bhatt, B.L.

1992-09-01

417

Diffusion coefficients for hydrogen sulfide, carbon dioxide, and nitrous oxide in water over the temperature range 293--368 K  

Microsoft Academic Search

Acid gases such as H[sub 2]S and CO[sub 2] are generally removed from natural gas, biogas, synthetic natural gas, and other process gas streams by means of absorption into aqueous alkanolamine solutions. A key parameter needed to model this diffusion with chemical reaction process in the liquid phase is the diffusion coefficient. A wetted-sphere absorption apparatus was used to measure

A. Tamimi; Edward B. Rinker; Orville C. Sandall

1994-01-01

418

Calculation of the standard partial molal thermodynamic properties of KCl{sup 0} and activity coefficients of aqueous KCl at temperatures and pressures to 1000{degree}C and 5 kbar  

SciTech Connect

Regression of experimental activity coefficient and dissociation constant data reported in the literature with the Hueckel and Setchenow equations and the revised HKF equations of state generated parameters and thermodynamic properties of dissociated KCl and KCl{sup 0} at 25{degrees}C and bar that can be used to calculate the standard partial molal thermodynamic properties of KCl{sup 0} and the activity coefficients of KCl at temperatures and pressures to 1000{degrees}C and 5 kbar. 46 refs., 6 figs., 4 tabs.

Pokrovskii, V.A. [ETH Zentrum, Zuerich (Switzerland)] [ETH Zentrum, Zuerich (Switzerland); Helgeson, H.C. [Univ. of California, Berkeley, CA (United States)] [Univ. of California, Berkeley, CA (United States)

1997-06-01

419

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...

420

Syntheses and reactivities of disubstituted and trisubstituted fluorous pyridines with high fluorous phase affinities: solid state, liquid crystal, and ionic liquid-phase properties.  

PubMed

Reactions of 2,6-dibromo-, 3,5-dibromo-, and 2,4,6-tribromopyridine with IZnCH(2)CH(2)R(f8) (R(f8) = (CF(2))(7)CF(3)) in THF at 65 degrees C in the presence of trans-Cl(2)Pd(PPh(3))(2) (5 mol %) gave the fluorous pyridines 2,6- and 3,5-NC(5)H(3)(CH(2)CH(2)R(f8))(2) (1 and 2; 85%, 31%) and 2,4,6-NC(5)H(2)(CH(2)CH(2)R(f8))(3) (3, 61%). Reaction of 2,6-pyridinedicarboxaldehyde with [Ph(3)PCH(2)CH(2)R(f8)](+)I(-)/K(2)CO(3) (p-dioxane/H(2)O, 95 degrees C) gave 2,6-NC(5)H(3)(CH[double bond]CHCH(2)R(f8))(2) (95%; 70:30 ZZ/ZE), which was treated with H(2) (1 atm, 12 h) and 10% Pd/C to yield 2,6-NC(5)H(3)(CH(2)CH(2)CH(2)R(f8))(2) (5, 95%), a higher homologue of 1. Longer reaction times afforded piperidine cis-2,6-HNC(5)H(8)(CH(2)CH(2)CH(2)R(f8))(2) (6, 98%). The stereochemistry was established by NMR analysis of the N-benzylpiperidine. Pyridines 1-3 and 5 are low-melting white solids with CF(3)C(6)F(11)/toluene partition coefficients (24 degrees C) of 93.8:6.2, 93.9:6.1, >99.7:<0.3, and 90.4:9.6, respectively (6, 93.6:6.4). Reaction of 1 and CF(3)SO(3)H gave a pyridinium salt, and Cl(2)Pd(NCCH(3))(2) (0.5 equiv) yielded trans-Cl(2)Pd(1)(2). The crystal structure of the former, which also exhibited liquid crystalline and ionic liquid phases, was determined. PMID:12353975

Rocaboy, Christian; Hampel, Frank; Gladysz, J A

2002-10-01