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1

GC–MS Analysis of Hydrogen Sulfide, Carbonyl Sulfide, Methanethiol, Carbon Disulfide, Methyl Thiocyanate and Methyl Disulfide in Mainstream Vapor Phase Cigarette Smoke  

Microsoft Academic Search

A method is described for the simultaneous analysis of hydrogen sulfide, carbonyl sulfide, methanethiol, carbon disulfide,\\u000a methyl thiocyanate and methyl disulfide in mainstream vapor phase (MVP) cigarette smoke by gas chromatography–mass spectrometry.\\u000a The fresh MVP smoke was collected in a gas bag, followed by injection of a 50 ?L gas sample into the GC inlet via an automatic\\u000a six-port valve. The

Ji-Zhou Dong; Samuel M. DeBusk

2010-01-01

2

Murine lung tumor response after exposure to cigarette mainstream smoke or its particulate and gas\\/vapor phase fractions  

Microsoft Academic Search

Knowledge on mechanisms of smoking-induced tumorigenesis and on active smoke constituents may improve the development and evaluation of chemopreventive and therapeutic interventions, early diagnostic markers, and new and potentially reduced-risk tobacco products. A suitable laboratory animal disease model of mainstream cigarette smoke inhalation is needed for this purpose. In order to develop such a model, A\\/J and Swiss SWR\\/J mouse

Walter Stinn; Josje H. E. Arts; Ansgar Buettner; Evert Duistermaat; Kris Janssens; C. Frieke Kuper; Hans-Juergen Haussmann

2010-01-01

3

Vapor Phase Pyrolysis.  

National Technical Information Service (NTIS)

The vapor phase pyrolysis process is designed exclusively for the lunar production of oxygen. In this concept, granulated raw material (soil) that consists almost entirely of metal oxides is vaporized and the vapor is raised to a temperature where it diss...

W. Steurer

1992-01-01

4

Adenylate Kinase 3 Sensitizes Cells to Cigarette Smoke Condensate Vapor Induced Cisplatin Resistance  

PubMed Central

Background The major established etiologic risk factor for bladder cancer is cigarette smoking and one of the major antineoplastic agents used for the treatment of advanced bladder cancer is cisplatin. A number of reports have suggested that cancer patients who smoke while receiving treatment have lower rates of response and decreased efficacy of cancer therapies. Methodology/Principal Findings In this study, we investigated the effect of cigarette smoke condensate (CSC) vapor on cisplatin toxicity in urothelial cell lines SV-HUC-1 and SCaBER cells. We showed that chronic exposure to CSC vapor induced cisplatin resistance in both cell lines. In addition, we found that the expression of mitochondrial-resident protein adenylate kinase-3 (AK3) is decreased by CSC vapor. We further observed that chronic CSC vapor-exposed cells displayed decreased cellular sensitivity to cisplatin, decreased mitochondrial membrane potential (??m) and increased basal cellular ROS levels compared to unexposed cells. Re-expression of AK3 in CSC vapor-exposed cells restored cellular sensitivity to cisplatin. Finally, CSC vapor increased the growth of the tumors and also curtail the response of tumor cells to cisplatin chemotherapy in vivo. Conclusions/Significance The current study provides evidence that chronic CSC vapor exposure affects AK3 expression and renders the cells resistant to cisplatin.

Chang, Xiaofei; Ravi, Rajani; Pham, Vui; Bedi, Atul; Chatterjee, Aditi; Sidransky, David

2011-01-01

5

Vapor phase lubrication of ceramics  

SciTech Connect

Vapor phase lubrication of ceramics under sliding wear has been extended up to 500{degrees}C, using tricresyl phosphate as the vaporized lubricant. In order to successfully lubricate ceramics, it was necessary to first activate the surface with a metal. Different methods of activating the surface have been investigated, including in-situ reaction with metal components. Continuous vapor phase lubrication of the activated ceramic reduced the coefficient of friction from 0.7 to less than 0.1, resulting in essentially no wear. The reduction in the wear rate and friction coefficient was due to a polymeric derivative of the original TCP which was formed on the high temperature surfaces. The deposit formed on the surface was analyzed using high performance liquid chromotography (HPLC). Results have suggested that it ins an organic polymer with a molecular range of 6000 to 60000 gmole/mole and an average molecular weight of approximately 30000 gmole/mole. This method of lubrication has direct application for the continuous lubrication of ceramic engines. 9 refs., 12 figs., 1 tab.

Hanyaloglu, B.; Graham, E.E. [Cleveland State Univ., OH (United States)

1994-10-01

6

Carbonyl compounds in gas and particle phases of mainstream cigarette smoke  

Microsoft Academic Search

Carbonyl compounds (carbonyls) are important constituents of cigarette smoke and some are toxic and may be carcinogenic or mutagenic to humans. In this study carbonyl emissions in the gas and particle phases of mainstream cigarette smoke were assessed by GC–MS with pentafluorophenyl hydrazine (PFPH) derivatization. Seven brands of cigarettes and one brand of cigar common in the UK market and

Xiaobing Pang; Alastair C. Lewis

2011-01-01

7

Carbon fibers from vapor phase hydrocarbons  

SciTech Connect

Less expensive carbon fibers may become available in the future by production from vapor phase hydrocarbons. In this process, iron based catalytic particles of a few nanometers diameter grow carbon filaments when they are exposed to hydrocarbon vapor near 1000 C. These filaments are of nanometer diameter but may be thickened by deposition of carbon from the vapor phase. The mechanical properties of the fibers made by this process resemble those of medium quality commercial fibers; the electrical and thermal conductivities are also desirable. 9 refs.

Tibbetts, G.G.

1990-01-01

8

Liquid-phase compositions from vapor-phase analyses  

Microsoft Academic Search

In the safe handling and processing of uranium hexafluoride (UFâ), it is often desirable to calculate vapor composition and pressure from known liquid composition and temperature. Furthermore, the ability to use analyses of equilibrium vapor-phase samples to calculate liquid-phase compositions would be economically advantageous to the International Atomic Energy Agency (IAEA) in its international safeguards program and to uranium enrichment

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

1989-01-01

9

Application of headspace solid phase microextraction to qualitative and quantitative analysis of tobacco additives in cigarettes  

Microsoft Academic Search

Cigarettes may contain up to 10% by weight additives which are intended to make them more attractive. A fast and rugged method for a cigarette-screening for additives with medium volatility was developed using automatic headspace solid phase microextraction (HS-SPME) with a 65?m carbowax-divinylbenzene fiber and gas chromatography–mass spectrometry (GC–MS) with standard electron impact ionisation. In three runs, each cigarette sample

Careen Merckel; Fritz Pragst; Astrid Ratzinger; Beat Aebi; Werner Bernhard; Frank Sporkert

2006-01-01

10

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

11

COMPARATIVE YIELDS OF MUTAGENS FROM CIGARETTE SMOKERS' URINE OBTAINED BY USING SOLID-PHASE EXTRACTION TECHNIQUES  

EPA Science Inventory

Urine from cigarette smokers was prepared for mutagenicity testing by extracting mutagens with solid phase extraction columns. ommercially available prepacked bonded silicas (cotadecyl, cyclohexyl, cyanopropyl) were compared for their efficiency and specificity in concentration o...

12

Electron beam targets vapor-phase contaminants  

SciTech Connect

Electron-beam bombardment has long been known to break down complex molecules. Zapit Technology, Inc. (Santa Clara, California) is in the process of commercializing a treatment system, tested in conjunction with the Lawrence Livermore National Laboratory, which uses electron beams to destroy vapor-phase toxic wastes. Drawing relatively low-power beams, the system is said to offer a low-cost way to oxidize chlorinated and non-chlorinated organic compounds. The unit has been developed to treat vapor-phase organic wastes at temperatures less than 400 F, and at ambient pressures. Candidates streams include process of gases, and organics collected during soil-vapor extraction or stripped from wastewater and groundwater streams. Inside the Zapit treatment unit, a continuous stream of ionizing electrons is generated by a cathode and is accelerated to nearly the speed of light through a metal grid. As the pollutant stream passes through the reaction chamber, it is bombarded by this electron beam. In the process, complex organic molecules are broken down into water, carbon dioxide, and, if chlorinated compounds are present, hydrochloric acid. During groundwater treatment, an air stripper converts dissolved organics in a vapor phase, which is passed through the electron-beam unit. The offgases from the Zapit unit are passed through an acid scrubber (using sodium hydroxide) to neutralize any byproduct HCl and through a carbon-adsorption unit for final polishing. Industrial offgases can be fed directly into the Zapit treatment unit, without the intermediate air stripper. Electrical power requirements are relatively low.

NONE

1995-07-01

13

Liquid-phase compositions from vapor-phase analyses  

SciTech Connect

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

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

1989-09-01

14

Mechanistic study of organometallic vapor phase epitaxy  

SciTech Connect

Only AsH{sub 3} and PH{sub 3} have been used as the group V source molecules for organometallic vapor phase epitaxy (OMVPE) of III/V semiconductors until recently, since they have been the only precursors yielding device quality materials. This paper reviews recent work on the pyrolysis of individual organometallic molecules, with emphasis on the group V sources, including: (1) the methylarsines, di- and tri-methylarsine, (2) the ethylarsines, mono-, di-, and tri-ethylarsine, and (3) the singly substituted tertiarybutyl arsine and phosphine molecules. The pyrolysis and growth reactions occurring when both group III and group V precursors are present simultaneously, i.e., the reactions occuring during OMVPE growth of several III/V semiconductors, are also briefly reviewed.

Stringfellow, G.B.

1990-01-01

15

Mechanistic study of organometallic vapor phase epitaxy  

SciTech Connect

Only AsH{sub 3} and PH{sub 3} have been used as the group V source molecules for organometallic vapor phase epitaxy (OMVPE) of III/V semiconductors until recently, since they have been the only precursors yielding device quality materials. This paper reviews recent work on the pyrolysis of individual organometallic molecules, with emphasis on the group V sources, including: (1) the methylarsines, di- and tri-methylarsine, (2) the ethylarsines, mono-, di-, and tri-ethylarsine, and (3) the singly substituted tertiarybutyl arsine and phosphine molecules. The pyrolysis and growth reactions occurring when both group III and group V precursors are present simultaneously, i.e., the reactions occuring during OMVPE growth of several III/V semiconductors, are also briefly reviewed.

Stringfellow, G.B.

1990-12-31

16

Chiroptical Spectroscopy in the Vapor Phase  

NASA Astrophysics Data System (ADS)

Electromagnetic radiation propagating through an isotropic chiral medium experiences a complex index of refraction that differs in both real (in-phase) and imaginary (in-quadrature) parts for the right-circular and left-circular polarization states that define the helicity basis. The resulting phenomena of circular birefringence (CB) and circular dichroism (CD) lead to observable effects in the form of dispersive rotation and absorptive elliptization for an impinging beam of plane-polarized light, which commonly are measured under conditions of nonresonant and resonant excitation, respectively. This talk will discuss ongoing efforts designed to elucidate the provenance of electronic optical activity under complementary solvated and isolated conditions, with the latter vapor-phase work made possible by our continuing development of Cavity Ring-Down Polarimetry (CRDP). Molecules of interest include the rigid bicyclic ketone (1R,4R)-norbornenone, where the spatial arrangement of distal alkene and carbonyl moeities gives rise to extraordinarily large specific rotation (CB) parameters that are predicted incongruously by different quantum-chemical methods; the monoterpene constitutional isomers (S)-2-carene and (S)-3-carene, which display surprisingly distinct chiroptical properties; and conjugated ketones such as (S)-verbenone, where CD probes of weak ?*?n absorption bands have been performed at vibronic resolution. The disparate nature of gas-phase and condensed-phase optical activity will be highlighted, with complementary ab initio calculations serving to elucidate the structural, chemical, and electronic origins of observed behavior. T. Müller, K. B. Wiberg, P. H. Vaccaro, J. R. Cheeseman, and M. J. Frisch, J. Opt. Soc. Am. B 19, 125 (2002) P. H. Vaccaro, ``Chapter 1.II.10: Optical Rotation and Intrinsic Optical Activity'' in Comprehensive Chiroptical Spectroscopy, N. Berova, P. L. Polavarapu, K. Nakanishi, and R. W. Woody, eds. (John Wiley and Sons, Inc., Hoboken, NJ, 2011).

Lahiri, Priyanka; Long, Benjamin D.; Wiberg, Kenneth B.; Vaccaro, Patrick H.

2011-06-01

17

Vapor phase extraction and separation of rare earths from bastnaesite concentrate mediated by vapor complexes  

Microsoft Academic Search

Vapor phase extraction and mutual separation characteristics of rare earths mediated by vapor complex in the LnCl3?Kcl systems (Ln = rare earth) were investigated using chemical vapor transport along a temperature gradient. Bastnaesite concentrate (LnFCO3) and potassium carbonate were used as raw material and precursor of the complex former, KCl, respectively oxyfluoride is complete within 2 h at 1000°Cin the

Tetsuya Ozaki; Toshiki Miyazawa; Kuniaki Murase; Ken-ichi Machida; Gin-ya Adachi

1996-01-01

18

The liquid to vapor phase transition in excited nuclei  

SciTech Connect

For many years it has been speculated that excited nuclei would undergo a liquid to vapor phase transition. For even longer, it has been known that clusterization in a vapor carries direct information on the liquid-vapor equilibrium according to Fisher's droplet model. Now the thermal component of the 8 GeV/c pion + 197 Au multifragmentation data of the ISiS Collaboration is shown to follow the scaling predicted by Fisher's model, thus providing the strongest evidence yet of the liquid to vapor phase transition.

Elliott, J.B.; Moretto, L.G.; Phair, L.; Wozniak, G.J.; Beaulieu, L.; Breuer, H.; Korteling, R.G.; Kwiatkowski, K.; Lefort, T.; Pienkowski, L.; Ruangma, A.; Viola, V.E.; Yennello, S.J.

2001-05-08

19

In-situ Vapor-Phase Lubrication of MEMS  

Microsoft Academic Search

In-situ vapor-phase lubrication of sidewall MicroElectroMechanical System (MEMS) devices is investigated with 1-pentanol vapor.\\u000a The 1-pentanol vapor successfully maintains lubricating properties between silicon contacts of MEMS devices. This is attributed\\u000a to the ability of alcohol to adsorb on the silicon surface and sustain a lubricating layer, which prevents wear of the MEMS\\u000a surfaces and minimizes friction. In the presence of

David B. Asay; Michael T. Dugger; Seong H. Kim

2008-01-01

20

Particle structure control in nanoparticle synthesis from the vapor phase  

Microsoft Academic Search

Nanostructured materials have generally been synthesized by condensation from the vapor phase in an inert carrier gas, most often in a buoyant plume above a hot vapor source. Particles form by homogeneous nucleation as the gases cool and grow by Brownian coagulation. Previous studies have shown that the size of the smallest structures is reduced with decreasing pressure, so most

Richard C. Flagan; Melissa M. Lunden

1995-01-01

21

[Electronic cigarette].  

PubMed

Electronic cigarette (e-cigarettes) belongs to the "ENDS (Electronic Nicotine Delivery Systems), ie systems that deliver nicotine electronically. Extract of tobacco does not burn, just warm. Vapors may or may not contain nicotine. E-cigarettes are also available with different flavors. They don't produce a classic smoke. There is a large variability of these products. It seems that the initial negative position has to be reconsidered. Although there has been demonstrated trace amounts of several toxic substances in the vapor, the risk compared to traditional smoking is minimal. Moreover, lately it was shown that they can really contribute to smoking quitting. The legislative framework varies considerably, from the prohibition on sales to the recommended assistance in quitting. In the CR they are included according to the Act 379/2005 in 2009 among the tobacco products. PMID:22679688

Králíková, Eva; Jezek, Martin

2012-01-01

22

REVIEW OF CRITERIA FOR VAPOR-PHASE HYDROCARBONS  

EPA Science Inventory

Information on vapor-phase hydrocarbons presented in this document covers basic atmospheric chemistry relative to secondary products, especially ozone; sources and emissions; ambient air concentrations; relationship of precursor hydrocarbons to resultant ozone levels in ambient a...

23

FIELD TRAPPING OF SUBSURFACE VAPOR PHASE PETROLEUM HYDROCARBONS  

EPA Science Inventory

Soil gas samples from intact soil cores were collected on adsorbents at a field site, then thermally desorbed and analyzed by laboratory gas chromatography (GC). ertical concentration profiles of predominant vapor phase petroleum hydrocarbons under ambient conditions were obtaine...

24

Preliminary assessment of halogenated alkanes as vapor-phase tracers  

SciTech Connect

New tracers are needed to evaluate the efficiency of injection strategies in vapor-dominated environments. One group of compounds that seems to meet the requirements for vapor-phase tracing are the halogenated alkanes (HCFCs). HCFCs are generally nontoxic, and extrapolation of tabulated thermodynamic data indicate that they will be thermally stable and nonreactive in a geothermal environment. The solubilities and stabilities of these compounds, which form several homologous series, vary according to the substituent ratios of fluorine, chlorine, and hydrogen. Laboratory and field tests that will further define the suitability of HCFCs as vapor-phase tracers are under way.

Adams, Michael C.; Moore, Joseph N.; Hirtz, Paul

1991-01-01

25

Hydride vapor phase epitaxy of aluminum nitride  

NASA Astrophysics Data System (ADS)

AlN is a promising substrate material for AlGaN-based UV optoelectronic devices and high-power, high-frequency electronic devices. Since large-area bulk AlN crystals are not readily available, one approach to prepare AlN substrates is to heteroepitaxially deposit thick (e.g., 10-300+ mum) AlN layers by hydride vapor phase epitaxy. Initial efforts focused on growing AlN layers on sapphire substrates with growth rates up to 75 mum/hr. The resulting layers were colorless, smooth, and specular. Subsurface cracking, attributed to the plastic relief of tensile strain from island coalescence, was observed but did not adversely affect the surface morphology of the AlN layers. The surfaces possessed rms roughnesses as low as 0.316 nm over 5 x 5 mum2 sampling areas, but hexagonal hillock formation was observed for thick films grown at high growth rates. TEM revealed that the threading dislocation (TD) density of the films was 2 x 109 cm-2. The high TD densities for direct growth of AlN films on foreign substrates motivated the development of lateral epitaxial overgrowth approaches for defect reduction. Growth of AlN layers on patterned SiC substrates produced coalesced AlN films possessing TD densities below 8.3 x 106 cm -2 in the laterally grown wing regions, as compared to 1.8 x 109 cm-2 in the seed regions. These films, however, cracked on cooldown due to the difference in thermal expansion coefficients for AlN and SiC. To avoid this cracking, AlN layers were grown on patterned sapphire substrates. Although the films were able to be coalesced and contained few or no cracks, the TDs in these films were not confined to the seed regions. This produced a relatively uniform distribution of TDs over the surfaces of the films, with only a modest reduction in the TD density of 1 x 10 8 cm-2. Selective area growth of AlN was also pursued using Si3N4, SiO2, and Ti masks. Growth selectivity and film coalescence was observed for films grown on each masking material, but none of the masks resulted in films with both smooth surface morphologies and low TD densities.

Kamber, Derrick Shane

26

An Overview: Vapor Phase Corrosion Inhibitors  

Microsoft Academic Search

When present as vapors, certain organic compounds offer inhibition against the corrosion of ferrous and nonferrous materials. The inhibitors include aliphatic, aromatic, cyclohexylamines, aminonitrobenzoates, heteroalkylated lower amines, etc. The mechanism of inhibition offered by these compounds was discussed and an unified mechanism was presented. Various methods of evaluating inhibition efficiency were discussed with a special reference to surface film characterization

A. Subramanian; T. Vasudevan; M. Natesan; V. S. Muralidharan; K. Balakrishnan

2000-01-01

27

Monitoring of LNG Vapors - Phase I.  

National Technical Information Service (NTIS)

This report documents the development and subsequent field testing of two rapid response instruments for the detection of methane gas in the vapor resulting from an LNG spill. The instruments were: a laser instrument with a 0.005 second response time and ...

E. D. Hinckley

1979-01-01

28

Studies on toxicological mechanisms of gas-phase cigarette smoke and protection effects of GTP  

Microsoft Academic Search

Gas-phase cigarette smoke (GPCS) was able to induce lipid peroxidation in lecithin liposomes, rat liver microsomes, and rat\\u000a lung cells (RLC), and change the membrane fluidity of RLCs. Lipid free radicals were trapped in a GPCS-treated microsomal\\u000a suspension by using 4-POBN as the spin trap. In addition, it was found that GPCS-peroxidized liposomes in appropriate degree\\u000a of lipid peroxidation had

F.-J. Yang; B.-L. Zhao; W.-J. Xin

1992-01-01

29

THE RADIOLYSIS OF ETHANOL. I. VAPOR PHASE  

Microsoft Academic Search

S>The alpha radiolysis of ethanol vapor at 108 deg C produced hydrogen ; as the major single product, with smaller amounts of methane, carbon monoxide, ; ethylene, ethane, acetaldehyde, formaldehyde, water, 2,3-butanediol, 1,2-; propanediol, propanol, and butanol. The intial yield of hydrogen was G(Hâ) ; = 8.9 plus or minus 0.4, which is much higher than the values reported for

J. M. Ramaradhya; G. R. Freeman

1961-01-01

30

Vapor phase oxidation of methylpyridine aldehydes  

Microsoft Academic Search

A study is made of the contact oxidation of a-, ß- and ?-methylpyridines by air, over the temperature range 390°–490° C, contact time 0.17–1.0 sec, mole ratio oxygen:methylpyridine 0.5 to 40:1, with dilution of the air-vapor mixture with water in the ratio 15–103 mole water per mole methylpyridine, using two vanadium oxide catalysts differing in respect of sizes of specific

L. Ya. Leitis; M. V. Shimanskaya

1967-01-01

31

Electronic Cigarettes  

MedlinePLUS

... Products Electronic Cigarettes Text Size: A A A Electronic Cigarettes Electronic cigarettes (e-cigarettes) are battery operated products designed ... more about: The latest news and events about electronic cigarettes on this FDA page Electronic cigarette basics ...

32

Elemental vapor-phase synthesis of nanostructured zinc oxide  

Microsoft Academic Search

We systematize experimental data on the elemental vapor-phase synthesis of zinc oxide nanocrystal arrays on substrates. This\\u000a process may yield nanostructures differing in shape and dimensions, in particular, well-aligned ZnO nanorod arrays. A model\\u000a is proposed in which aligned zinc oxide nanorod arrays may grow by the vapor-liquid-solid (VLS) mechanism, and liquid zinc\\u000a nanodroplets forming on the substrate surface at

A. N. Red’kin; Z. I. Makovei; A. N. Gruzintsev; E. E. Yakimov; O. V. Kononenko; A. A. Firsov

2009-01-01

33

Free-base nicotine in tobacco products. Part I. Determination of free-base nicotine in the particulate phase of mainstream cigarette smoke and the relevance of these findings to product design parameters.  

PubMed

The free-base nicotine (FBN) content of mainstream cigarette smoke (MSS) has been discussed in the peer-reviewed literature and popular press. It has been alleged that manufacturers adjust product design features to increase the percentage of total nicotine (TN) in the MSS gas-vapor phase that is unprotonated [P(g)(,nic)(%)] and/or the fraction of nicotine in the MSS total particulate matter (TPM) that is unprotonated (FBN/TN). Our research showed the Health Canada Intensive smoking conditions negated the effects of blend and cigarette design features reported to raise the pH of TPM collected under ISO or US FTC conditions. Our research also showed that when additive-free Canadian cigarettes were smoked under ISO conditions, the FBN/TN ratio increased as the tar/nicotine ratio decreased. Our findings are in line with other studies that have questioned allegations of a relationship between use of ammonia and its compounds as tobacco additives and amounts of unprotonated nicotine in MSS. In addition, the experimental work demonstrated how use of solid-phase microextraction to estimate FBN can yield erroneously high results due to improper conditioning and/or smoking of the cigarettes. Our research showed that there is no longer any scientific support for regulators to require smoke pH and FBN determinations on cigarette products. PMID:20621585

Lauterbach, J H; Bao, M; Joza, P J; Rickert, W S

2010-06-01

34

Gas phase reaction of sulfur trioxide with water vapor  

SciTech Connect

Sulfur trioxide (SO3) has long been known to react with water to produce sulfuric acid (H2S04). It has been commonly assumed that the gas phase reaction in the Earth`s atmosphere between SO3 and water vapor to produce sulfuric acid vapor is an important step in the production of sulfuric acid aerosol particles. The kinetics of the gas phase reaction of SO3 with water vapor have previously been studied by Castleman and co-workers, Wang et al and Reiner and Arnold. Each of these studies was carried out in a flow reactor, with the first two studies performed at low pressure (1-10 Torr) and the latter from approx. 30 to 260 Torr. Each of these studies measured SO3 decays over a range of H2O vapor levels, obtaining data consistent with interpreting the reaction of gaseous SO3 and H2O as a bimolecular process. It is not clear why previous experimental studies failed to observe a nonlinear dependence of SO3 consumption on water vapor concentration. It is probable that sufficient water dimer exists in much of the Earth`s atmosphere to allow dimer reactions to participate in sulfuric acid vapor formation.

Kolb, C.E.; Molina, M.J.; Jayne, J.T.; Meads, R.F.; Worsnop, D.R.

1994-12-31

35

Calibration of an explosives vapor generator based on vapor diffusion from a condensed phase  

SciTech Connect

In the field of explosives detection there is currently a need for a calibrated source of explosives vapor. Such a source could be used to test and calibrate explosives detection systems which identify explosives via the collection of vapor or air borne particulate matter. This paper describes the principles of operation and evaluation of one such explosives vapor generator. This generator is based on the diffusion of vapor from a condensed phase (i.e., solid or liquid) in a source reservoir, and the output has been tied to a National Institute of Standards and Technology (NIST) mass standard. We discuss results of the calibration of this generator using the explosives 2,4,6-trinitrotoluene (TNT) and cyclonite (RDX). The mass output of this generator is stable over hundreds of hours of continuous operation, and is adjustable from the low picograms(pg)/sec range to at least 10 nanograms(ng)/sec. In the case of TNT, the mass output correlates well with predictions based on gas phase diffusion theory. In the case of RDX, the agreement with theory is less good. This may be attributable to a variety of factors, possibly including inaccuracies in the published data on RDX vapor pressure as a function of temperature.

Parmeter, J.E. [Sandia National Labs., Albuquerque, NM (United States); Eiceman, G.A.; Preston, D.A.; Tiano, G.S. [New Mexico State Univ., Las Cruces, NM (United States)

1996-08-01

36

Early specific free radical-related cytotoxicity of gas phase cigarette smoke and its paradoxical temporary inhibition by tar  

Microsoft Academic Search

Electron paramagnetic resonance (EPR) spin trapping studies demonstrated aqueous tar particulate matter (TPM) and gas phase cigarette smoke (GPCS) to behave as different sources of free radicals in cigarette smoke (CS) but their cytotoxic implications have been only assessed in CS due to its relevance to the natural smoking process. Using a sensitive spin trapping detection with 5-(diethoxyphosphoryl)-5-methyl-1-pyrroline-N-oxide (DEPMPO), this

Marcel Culcasi; Agnès Muller; Anne Mercier; Jean-Louis Clément; Olivier Payet; Antal Rockenbauer; Véronique Marchand; Sylvia Pietri

2006-01-01

37

Quantitative Infrared Spectra of Vapor Phase Chemical Agents  

SciTech Connect

Quantitative high resolution (0.1 cm -1) infrared spectra have been acquired for a number of pressure broadened (101.3 KPa N2), vapor phase chemicals including: Sarin (GB), Soman (GD), Tabun (GA), Cyclosarin (GF), VX, nitrogen mustard (HN3), sulfur mustard (HD) and Lewisite (L).

Sharpe, Steven W.; Johnson, Timothy J.; Chu, P M.; Kleimeyer, J; Rowland, Brad; Gardner, Patrick J.

2003-04-21

38

Numerical Modeling of Liquid-Vapor Phase Change.  

National Technical Information Service (NTIS)

We implemented a two- and three-dimensional finite difference/front tracking technique to solve liquid-vapor phase change problems. The mathematical and the numerical features of the method were explained in great detail in our previous reports, Briefly, ...

A. Esmaeeli V. S. Arpaci

2001-01-01

39

Fog Machines, Vapors, and Phase Diagrams  

ERIC Educational Resources Information Center

|A series of demonstrations is described that elucidate the operation of commercial fog machines by using common laboratory equipment and supplies. The formation of fogs, or "mixing clouds", is discussed in terms of the phase diagram for water and other chemical principles. The demonstrations can be adapted for presentation suitable for elementary…

Vitz, Ed

2008-01-01

40

Assessment of radionuclide vapor-phase transport in unsaturated tuff  

SciTech Connect

This report describes bounding calculations performed to investigate the possibility of radionuclide migration in a vapor phase associated with the emplacement of high-level waste canister in unsaturated tuff formations. Two potential radionuclide transport mechanisms in the vapor phase were examined: aerosol migration and convection/diffusion of volatile species. The former may have significant impact on the release of radionuclides to the accessible environment as the concentration in the aerosols will be equal to that in the ground water. A conservative analysis of air diffusion in a stagnant liquid film indicated that for all expected repository conditions, aerosol formation is not possible. The migration of volatile species was examined both in the vicinity of a waste canister and outside the thermally disturbed zone. Two-dimensional (radial) and three-dimensional (radial-vertical) coupled heat transfer-gas flow-liquid flow simulations were performed using the TOUGH computer code. The gas flow rate relative to the liquid flow rate predicted from the simulations allowed calculations of mobility ratios due to convection which led to the conclusion that, except for the immediate region near the canister, transport in the liquid phase will be dominant for radionuclides heavier than radon. Near the waste canister, iodine transport may also be important in the vapor phase. Bounding calculations for vertical mobility ratios were carried out as a function of saturation. These calculations are conservative and agree well with the two-dimensional simulations. Based on this analysis, it is clear that vapor-phase transport will not be important for radionuclides such as cesium and heavier species. Vapor transport for iodine may play a role in the overall release scenario depending on the particular repository conditions.

Smith, D.M.; Updegraff, C.D.; Bonano, E.J.; Randall, J.D.

1986-11-01

41

Measurements of viscosity of refrigerants in the vapor phase  

SciTech Connect

Measurements of the viscosity of refrigerants R124, R125, R134a, and R152a in the vapor phase are presented. The measurements, performed in a new vibrating-wire instrument, cover a temperature range from 273 to 333 K from about atmospheric pressure up to below the saturation pressure. The uncertainty of the reported values is estimated to be better than {+-}1%. Comparison with measurements of other investigators reveals a lack of reliable data in the vapor region for these compounds.

Assael, M.J.; Polimatidou, S.K. [Aristotle Univ., Thessaloniki (Greece). Faculty of Chemical Engineering

1997-03-01

42

Adiabatic nucleation in the liquid-vapor phase transition  

NASA Astrophysics Data System (ADS)

The fundamental difference between classical (isothermal) nucleation theory (CNT) and adiabatic nucleation theory (ANT) is discussed. CNT uses the concept of isothermal heterophase fluctuations, while ANT depends on common fluctuations of the thermodynamic variables. Applications to the nonequilibrium liquid to vapor transition are shown. However, we cannot yet calculate nucleation frequencies. At present, we can only indicate at what temperatures and pressures copious homogeneous nucleation is expected in the liquid to vapor phase transition. It is also explained why a similar general indication cannot be made for the inverse vapor to liquid transition. Simultaneously, the validity of Peng-Robinson's equation of state [D.-Y. Peng and D. B. Robinson, Ind. Eng. Chem. Fundam. 15, 59 (1976)] is confirmed for highly supersaturated liquids.

de Sá, Elon M.; Meyer, Erich; Soares, Vitorvani

2001-05-01

43

Comparative Characterization of Organic Emissions from Diesel Particles, Coke Oven Mains, Roofing Tar Vapors and Cigarette Smoke Condensate.  

National Technical Information Service (NTIS)

The paper reports the characterization of the extractable organics from diesel particle emissions compared to other complex organics which have been reported to increase the risk of human lung cancer. Class fractions of diesel, cigarette smoke condensate,...

R. Williams C. Sparacino B. Petersen J. Bumgarner R. H. Jungers

1986-01-01

44

ACA phase calibration scheme with the ALMA water vapor radiometers  

NASA Astrophysics Data System (ADS)

In Atacama Large Millimeter/submillimeter Array (ALMA) commissioning and science verification we have conducted a series of experiments of a novel phase calibration scheme for Atacama Compact Array (ACA). In this scheme water vapor radiometers (WVRs) devoted to measurements of tropospheric water vapor content are attached to ACA’s four total-power array (TP Array) antennas surrounding the 7 m dish interferometer array (7 m Array). The excess path length (EPL) due to the water vapor variations aloft is fitted to a simple two-dimensional slope using WVR measurements. Interferometric phase fluctuations for each baseline of the 7 m Array are obtained from differences of EPL inferred from the two-dimensional slope and subtracted from the interferometric phases. In the experiments we used nine ALMA 12-m antennas. Eight of them were closely located in a 70-m square region, forming a compact array like ACA. We supposed the most four outsiders to be the TP Array while the inner 4 antennas were supposed to be the 7 m Array, so that this phase correction scheme (planar-fit) was tested and compared with the WVR phase correction. We estimated residual root-mean-square (RMS) phases for 17- to 41-m baselines after the planar-fit phase correction, and found that this scheme reduces the RMS phase to a 70 - 90 % level. The planar-fit phase correction was proved to be promising for ACA, and how high or low PWV this scheme effectively works in ACA is an important item to be clarified.

Asaki, Yoshiharu; Matsushita, Satoki; Morita, Koh-Ichiro; Nikolic, Bojan

2012-09-01

45

Electron-spin resonance study of mainstream and sidestream cigarette smoke: nature of the free radicals in gas-phase smoke and in cigarette tar.  

PubMed Central

Radicals in the gas phase of both mainstream and sidestream cigarette smoke have been studied using electron-spin resonance ESR spin-trapping techniques with alpha-phenyl-N-tert-butyl nitrone (PBN) as the spin trap. The principal radicals we trap appear to be alkoxyl radicals. Mainstream and sidestream gas-phase smoke each have about the same concentration of radicals, about 1 X 10(16) radicals per cigarette (or 5 X 10(14) per puff). These radicals are reactive, yet they appear to be remarkably long-lived: they are still spin trapped from gas-phase smoke after more than 5 min. We propose that a steady-state concentration of reactive radicals exists in gas phase cigarette smoke. We suggest that this steady state is produced by the slow oxidation of nitric oxide (present in high concentrations in smoke and relatively unreactive) to the more reactive nitrogen dioxide, followed by the reaction of nitrogen dioxide with reactive organic molecules in smoke (such as olefins and dienes). Preliminary experiments reported here support this hypothesis. Tar from both mainstream and sidestream smoke contains persistent free radicals that exhibit broad, single-line ESR spectra with g values of 2.003. The tar radical can be extracted into tert-butylbenzene and other organic solvents, and we have applied a variety of fractionation procedures to these solutions. Most of the radicals occur in the fractions that contain the phenolic tobacco leaf pigments. Treatment of alcoholic solutions of tar with base generates a new group of radicals that appear to be semiquinone radicals derived from the oxidation of the phenolic and polyphenolic species in tar.

Pryor, W A; Prier, D G; Church, D F

1983-01-01

46

Nonaqueous phase liquid spreading during soil vapor extraction  

Microsoft Academic Search

Many non-aqueous phase liquids (NAPLs) are expected to spread at the air–water interface, particularly under non-equilibrium conditions. In the vadose zone, this spreading should increase the surface area for mass transfer and the efficiency of volatile NAPL recovery by soil vapor extraction (SVE). Observations of spreading on water wet surfaces led to a conceptual model of oil spreading vertically above

Timothy J. Kneafsey; James R. Hunt

2004-01-01

47

Vapor-phase hydration of propylene oxide over tricalcium phosphate  

Microsoft Academic Search

1.The catalytic activity of tricalcium phosphate in the vapor-phase hydration of propylene oxide to propylene glycol was studied.2.Calcium phosphate is a stable and selective catalyst for this reaction.3.The effect of temperature, contact time, and water excess on the glycol yield was studied. Considerable amounts of glycol were formed under the optimal conditions and the glycol yield reached 50–57% at 232°,

L. Kh. Freidlin; V. Z. Sharf

1960-01-01

48

QCM Studies of Alcohols as Vapor Phase Lubricants for MEMS  

NASA Astrophysics Data System (ADS)

The future of nanotechnology depends in part upon the development of successful lubrication for micromachines (MEMS). Atomic Force Microscopy (AFM) research at Pennsylvania State University* has suggested alcohols such as propanol, ethanol, butanol, and pentanol to be potential vapor phase lubricants for MEMS; propanol at its vapor pressure can greatly reduce the friction on silicon dioxide surfaces. Due to the relatively high vapor pressure of these alcohols, all surfaces of a MEMS, including buried interfaces not easily reached by solid coatings, should become coated in thin layers of the alcohol upon exposure. We are testing the ability of the alcohols to migrate to buried interfaces in the MEMS. The mass uptake of the alcohols will be measured using the quartz crystal microbalance (QCM) in a vacuum chamber. The resonant frequency of the QCM drops as alcohols adsorb on its face. The uptake of the alcohols is measured as the pressure increases using different geometries of the cans, allowing us to simulate a buried interface. The aforementioned alcohols are first thermally distilled, then leaked into the chamber until vapor pressure of the alcohol is reached. We see significant mass uptake even in extreme geometries, where the entire QCM face is only accessible through a tiny hole in the can encasing the QCM, 0.0006'' in diameter. *K. Strawhecker et al., Trib. Lett. 19, 17 (2005).

Nemetz, Heather; Jones, Jon; Coffey, Tonya

2006-11-01

49

Calibration of an explosives vapor generator based on vapor diffusion from a condensed phase.  

National Technical Information Service (NTIS)

Development of a vapor generator for consistently producing accurate amounts of vapor from low vapor pressure explosive materials is a pressing need within the explosives detection community. Of particular importance for reproducibility and widespread acc...

J. E. Parmeter L. Rhykerd F. J. Conrad G. S. Tiano D. Preston

1995-01-01

50

Nonequilibrium mass transfer between the vapor, aqueous, and solid phases in unsaturated soils during vapor extraction  

NASA Astrophysics Data System (ADS)

Vapor extraction is a commonly used method for removing nonaqueous phase liquid volatile organic compounds (VOC) from the vadose zone. Experience indicates that in the absence of liquid VOC, the efficiency of vapor extraction systems decreases dramatically with time as effluent concentrations approach zero asymptotically. When such systems are restarted after a temporary shutdown, effluent concentrations are often found to recover for a short period before dropping back to preshutdown levels. This behavior is generally attributed to kinetic processes which limit the transfer of contaminant into the moving air. A numerical model is developed to simulate the rate-limited extraction of volatile compounds governed by first-order kinetic mass transfer processes. A sensitivity analysis is performed to identify model responses to various kinetic and equilibrium partitioning processes. The model is calibrated using experimental data collected from a pilot-scale experiment involving vapor extraction of trichloroethylene from fine sand. An analysis of the relationships between airflow rates and the kinetic mass transfer coefficients under various pumping schemes shows that for a given condition, increasing the flow rate has little effect beyond a certain point. It is also shown that pulsed pumping is generally less efficient than continuous pumping at a low rate.

Armstrong, J. E.; Frind, E. O.; McClellan, R. D.

1994-02-01

51

Vapor-induced phase separation—effect of the humid air exposure step on membrane morphology  

Microsoft Academic Search

Vapor-induced phase separation (VIPS) involves a dry–wet casting process in which the dope solution is exposed to a nonsolvent vapor (often humid air) for a fixed time interval prior to immersion in a coagulation bath. Humid air exposure leads to a slow transfer of water from the vapor phase into the dope solution. By controlling the humid air exposure time,

V. P. Khare; A. R. Greenberg; W. B. Krantz

2005-01-01

52

Propane-induced biodegradation of vapor phase trichloroethylene  

SciTech Connect

Microbial degradation of trichloroethylene (TCE) has been demonstrated under aerobic conditions with propane. The primary objective of this research was to evaluate the feasibility of introducing a vapor phase form of TCE in the presence of propane to batch bioreactors containing a liquid phase suspension of Mycobacterium vaccae JOB5 to accomplish degradation. The reactor system consisted of three phases: a vapor phase introducing air, propane, and a solid phase in the form of the microorganisms. Long-term and initial rate experiments were conducted on three culture sets to evaluate microbial response. In two long-term tests fed propane and approximately 0.1 mg/L and 1 mg/L of TCE, respectively, propane utilization was more efficient at the high TCE concentration because the propane degradation rate was approximately the same for both tests. In addition, TCE utilization decreased after complete propane consumption. Initial rate tests on culture sets fed propane only revealed that cells with a history of exposure to a high concentration of TCE had the highest specific growth rate, but the lowest half-saturation constant. Tests fed variable TCE concentration (0.031 to 5.378 mg/L in the liquid phase) with no propane showed TCE depletion but no biomass growth. The tests revealed that the TCE removal increased as the TCE concentration increased, indicating a greater removal efficiency at the higher concentrations. Tests with a constant initial propane concentration and variable liquid phase TCE concentration revealed that specific propane utilization was essentially the same.

Wilcox, D.W. [John Carollo Engineers, College Station, TX (United States); Autenrieth, R.L.; Bonner, J.S. [Texas A and M Univ., College Station, TX (United States). Dept. of Civil Engineering

1995-05-20

53

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

Microsoft Academic Search

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

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

2009-01-01

54

Preventing Kinetic Roughening in Physical Vapor-Phase-Deposited Films  

NASA Astrophysics Data System (ADS)

The growth kinetics of the mostly used physical vapor-phase deposition techniques —molecular beam epitaxy, sputtering, flash evaporation, and pulsed laser deposition—is investigated by rate equations with the aim of testing their suitability for the preparation of ultraflat ultrathin films. The techniques are studied in regard to the roughness and morphology during early stages of growth. We demonstrate that pulsed laser deposition is the best technique for preparing the flattest films due to two key features [use of (i) a supersaturated pulsed flux of (ii) hyperthermal species] that promote a kinetically limited Ostwald ripening mechanism.

Vasco, E.; Polop, C.; Sacedón, J. L.

2008-01-01

55

AlN wafers fabricated by hydride vapor phase epitaxy  

SciTech Connect

The authors report on AlN wafers fabricated by hydride vapor phase epitaxy (HVPE). AlN thick layers were grown on Si substrates by HVPE. Growth rate was up to 60 microns per hour. After the growth of AlN layers, initial substrates were removed resulting in free-standing AlN wafers. The maximum thickness of AlN layer was about 1 mm. AlN free-standing single crystal wafers with a thickness ranging from 0.05 to 0.8 mm were studied by x-ray diffraction, transmission electron microscopy, optical absorption, and cathodoluminescence.

Nikolaev, A.; Nikitina, I.; Zubrilov, A.; Mynbaeva, M.; Melnik, Y.; Dmitriev, V.

2000-07-01

56

Sporicidal Activity of the KMT reagent in its vapor phase against Geobacillus stearothermophilus Spores.  

PubMed

In an investigation of the sporicidal activity of the KMT reagent, a vapor phase study was performed using five kinds of carriers contaminated with Geobacillus stearothermophilus spores. When 25 ml of the KMT reagent was vaporized in a chamber (capacity; approximately 95 liters), the 2-step heating method (vaporization by a combination of low temperature and high temperature) showed the most effective sporicidal activity in comparison with the 1-step heating method (rapid vaporization). The 2-step heating method appeared to be related to the sporicidal activity of vaporized KMT reagent, i.e., ethanol and iodine, which vaporized mainly when heated at a low temperature such as 55 C, and acidic water, which vaporized mainly when heated at a high temperature such as 300 C. We proposed that the KMT reagent can be used as a new disinfectant not only in the liquid phase but also in the vapor phase in the same way as peracetic acid and hydrogen peroxide. PMID:17237604

Kida, Nori; Mochizuki, Yasushi; Taguchi, Fumiaki

2007-01-01

57

Continuous Determination of High-Vapor Phase Concentrations of Tetrachloroethylene Using On-Line Mass Spectrometry  

EPA Science Inventory

A method was developed to determine the vapor concentration of tetrachloroethylene (PCE) at and below its equilibrium vapor phase concentration, 168,000 μg/L (25°C). Vapor samples were drawn by vacuum into a six-port sampling valve and injected through a jet separator into an io...

58

Vaporization behavior of non-stoichiometric refractory carbide materials and direct observations of the vapor phase using laser diagnostics  

NASA Astrophysics Data System (ADS)

Transition metal and actinide carbides, such as ZrC or NbC and UC or ThC, exhibit a wide range of stoichiometry, and therefore vaporize incongruently. At long times, steady state vaporization can be achieved where relative concentrations of atomic species on solid surface equals that in the gas phase. The surface composition under these steady state conditions is termed the congruently vaporizing composition, (CVC). Modeling the vaporization or corrosion behavior of this dynamic process is complex and requires an understanding of how the surface composition changes with time and a knowledge of CVC, which is both temperature and atmosphere dependent. This paper describes vaporization and corrosion behavior of non-stoichiometric refractory carbide materials and, as an example, describes a thermokinetic model that characterizes the vaporization behavior of the complex carbide U(x)Zr(1-x)C(y) in hydrogen at 2500 to 3200 K. This model demonstrates that steady state corrosion of U(x)Zr(1-x)C(y) is rate limited by gaseous transport of Zr where partial pressure of Zr is determined by CVC. This paper also briefly describes efforts to image and characterize the vapor phase above the surface of ZrC in static and flowing gas environments using planar laser induced fluorescence. We have developed the method for monitoring and controlling the corrosion behavior of nuclear fuels in nuclear thermal rockets. However, the techniques described can be used, to image boundary layers, and could be used verifying corrosion models.

Butt, D. P.; Wantuck, P. J.; Rehse, S. J.; Wallace, T. C., Sr.

59

Evidence of Phase Separation during Vapor Deposition Polymerization  

NASA Astrophysics Data System (ADS)

Initiated chemical vapor deposition (iCVD) is a solventless, free radical technique predominately used to deposit homogeneous films of linear and crosslinked polymers directly from gas phase feeds. We are developing multicomponent iCVD techniques to induce phase separation during film growth. Small molecule porogens and crosslinkers are introduced into the iCVD process during film growth of poly(glycidyl methacrylate). Analogous to well established polymerization induced phase separation (PIPS) processes, porogens, such as dimethyl phthalate, are well mixed at the growing gas-film interface but are immiscible with high molecular weight polymer. Polymerization, crosslinking and PIPS are intended to occur simultaneously on the substrate, resulting in a vitrified microstructure. A series of films were grown by varying deposition rate, porogen type, and reagent flowrates. Deposited films were studied by electron microscopy and spectroscopic techniques. Experiments are compared to Cahn-Hilliard theory predictions that relate the length and time scale of the phase separation to the polymer-porogen interaction energy, the rate of polymerization and the species mobility.

Tao, Ran; Anthamatten, Mitchell

2013-03-01

60

Vapor phase mediated cellular uptake of sub 5 nm nanoparticles  

PubMed Central

Nanoparticles became an important and wide-used tool for cell imaging because of their unique optical properties. Although the potential of nanoparticles (NPs) in biology is promising, a number of questions concerning the safety of nanomaterials and the risk/benefit ratio of their usage are open. Here, we have shown that nanoparticles produced from silicon carbide (NPs) dispersed in colloidal suspensions are able to penetrate into surrounding air environment during the natural evaporation of the colloids and label biological cells via vapor phase. Natural gradual size-tuning of NPs in dependence to the distance from the NP liquid source allows progressive shift of the fluorescence color of labeled cells in the blue region according to the increase of the distance from the NP suspension. This effect may be used for the soft vapor labeling of biological cells with the possibility of controlling the color of fluorescence. However, scientists dealing with the colloidal NPs have to seriously consider such a NP's natural transfer in order to protect their own health as well as to avoid any contamination of the control samples.

2012-01-01

61

Vapor phase mediated cellular uptake of sub 5 nm nanoparticles  

NASA Astrophysics Data System (ADS)

Nanoparticles became an important and wide-used tool for cell imaging because of their unique optical properties. Although the potential of nanoparticles (NPs) in biology is promising, a number of questions concerning the safety of nanomaterials and the risk/benefit ratio of their usage are open. Here, we have shown that nanoparticles produced from silicon carbide (NPs) dispersed in colloidal suspensions are able to penetrate into surrounding air environment during the natural evaporation of the colloids and label biological cells via vapor phase. Natural gradual size-tuning of NPs in dependence to the distance from the NP liquid source allows progressive shift of the fluorescence color of labeled cells in the blue region according to the increase of the distance from the NP suspension. This effect may be used for the soft vapor labeling of biological cells with the possibility of controlling the color of fluorescence. However, scientists dealing with the colloidal NPs have to seriously consider such a NP's natural transfer in order to protect their own health as well as to avoid any contamination of the control samples.

Serdiuk, Tetiana; Lysenko, Vladimir; Skryshevsky, Valery A.; Géloën, Alain

2012-04-01

62

Review of criteria for vapor-phase hydrocarbons. Final report  

SciTech Connect

Information on vapor-phase hydrocarbons presented in this document covers basic atmospheric chemistry relative to secondary products, especially ozone; sources and emissions; ambient air concentrations; relationship of precursor hydrocarbons to resultant ozone levels in ambient air; health effects; and welfare effects. The principal conclusions from this document are as follows. Hydrocarbons are a principal contributor to the formation of ozone and other photochemical oxidants; however, no fixed single quantitative relationship between precursor hydrocarbons and resulting ozone concentrations can be defined. This relationship varies from site to site depending on local precursor mixes, transport considerations, and meteorological factors. Consequently no single quantitative relationship can be defined nationwide. While specific hydrocarbon compounds can be of concern to public health and welfare, as a class this group of materials cannot be considered a hazard to human health or welfare at or even well above those concentrations observed in the ambient air.

Tilton, B.E.; Bruce, R.M.

1981-10-01

63

Quantitative Infrared Spectra of Vapor Phase Chemical Agents  

SciTech Connect

Quantitative, moderately high resolution (0.1 cm-1) infrared spectra have been acquired for a number of nitrogen broadened (1 atm N2) vapor phase chemicals including: Sarin (GB), Soman (GD), Tabun (GA), Cyclosarin (GF), VX, Nitrogen Mustard (HN3), Sulfur Mustard (HD), and Lewisite (L). The spectra are acquired using a heated, flow-through White Cell1 of 5.6 meter optical path length. Each reported spectrum represents a statistical fit to Beer’s law, which allows for a rigorous calculation of uncertainty in the absorption coefficients. As part of an ongoing collaboration with the National Institute of Standards and Technology (NIST), cross-laboratory validation is a critical aspect of this work. In order to identify possible errors in the Dugway flow-through system, quantitative spectra of isopropyl alcohol from both NIST and Pacific Northwest National Laboratory (PNNL) are compared to similar data taken at Dugway proving Grounds (DPG).

Sharpe, Steven W.; Johnson, Timothy J.; Chu, P. M.; Kleimeyer, J.; Rowland, Brad

2003-08-01

64

Quantitative infrared spectra of vapor phase chemical agents  

NASA Astrophysics Data System (ADS)

Quantitative, high resolution (0.1 cm-1) infrared spectra have been acquired for a number of pressure broadened (101.3 KPa N2), vapor phase chemicals including: Sarin (GB), Soman (GD), Tabun (GA), Cyclosarin (GF), VX, nitrogen mustard (HN3), sulfur mustard (HD) and Lewisite (L). The spectra are acquired using a heated, flow-through White cell of 5.6 m optical path length. Each reported spectrum represents a statistical fit to Beer"s law, which allows for a rigorous calculation of uncertainty in the absorption coefficients. As part of an ongoing collaboration with the National Institute of Standards and Technology (NIST), cross-laboratory validation is a critical aspect of this work. In order to identify possible errors in the Dugway flow-through system, quantitative spectra of isopropyl alcohol from both NIST and Pacific Northwest National Laboratory (PNNL) are compared to similar data taken at the Dugway Proving Ground (DPG).

Sharpe, Steven W.; Johnson, Timothy J.; Chu, Pamela M.; Kleimeyer, James; Rowland, Brad

2003-08-01

65

Field demonstration of vapor phase TCE bioreactor. Final report  

SciTech Connect

The objective of this Cooperative Research and Development Agreement (CRADA), was to demonstrate the effectiveness of a vapor-phase bioreactor system for the destruction of trichloroethylene (TCE) from contaminated groundwater. A field demonstration was per-formed using groundwater at the Oak Ridge K-25 Site contaminated with a complex mixture of organic chemicals. This site is managed and operated by Martin Marietta Energy Systems, Inc. for the Department of Energy (DOE). Analysis of the data generated during the test can be summarized in three major observations. First, TCE was degraded in the presence of all the organics found in the steam strip condensate. This was observed during treatment of both the steam strip condensate and condensate amended with TCE to increase its concentration relative to the other components. The conclusion that TCE was being biodegraded was supported by performing mass balance control experiments with the reactor and by tracking recalcitrant chemicals also present in the steam stripper condensate. Second, there appeared to be an initial lag period of up to 24 hours before onset of TCE degradation in the reactor. The source of this lag was not determined but could be related to either an acclimation of the microorganisms to other chemicals found in the condensate or reversible inhibitory effects on TCE degradation. The duration of TCE degradative activity was relatively short for only 2 to 5 days. compared to previous demonstrations where TCE was the sole contaminant. However, several of the runs were interrupted due to mechanical and not biological issues. Third, other chemical contaminants were also degraded. by the bacteria used in the vapor phase reactor which is consistent with previous work performed both at ENVIROGEN and elsewhere.

NONE

1994-12-14

66

Vapor-phase synthesis of metallic and intermetallic nanoparticles and nanowires: Magnetic and catalytic properties  

Microsoft Academic Search

In this paper, we present several examples of the vapor-phase synthesis of inter- metallic and alloy nanoparticles and nanowires, and investigate their magnetic and catalytic properties. In the first example, we report the vapor-phase synthesis of intermetallic alu- minide nanoparticles. Specifically, FeAl and NiAl nanoparticles were synthesized via laser vaporization controlled condensation (LVCC) from their bulk powders. The NiAl nanoparti-

Garry Glaspell; Victor Abdelsayed; Khaled M. Saoud; M. Samy El-Shall

2006-01-01

67

E-cigarettes: promise or peril?  

PubMed

Electronic cigarettes (e-cigarettes) use a heating element to vaporize nicotine and other ingredients, simulating the visual, sensory, and behavioral aspects of smoking without the combustion of tobacco. An ever-growing number of companies around the world manufacture a wide variety of e-cigarette brands, despite scant information on the safety of the ingredients for human inhalation. This article provides an overview of the history, production, and marketing of e-cigarettes, the contents of e-cigarettes and vapor, how they are used, public health concerns, and implications for nursing practice, research, and policy development. PMID:22289406

Riker, Carol A; Lee, Kiyoung; Darville, Audrey; Hahn, Ellen J

2012-03-01

68

Solid phase crystallization of thin films of Si prepared by plasma-enhanced chemical vapor deposition  

Microsoft Academic Search

Solid phase crystallization of thin films of undoped amorphous Si prepared by plasma enhanced chemical vapor deposition has been studied by transmission electron microscopy (TEM). From the TEM images, the thermodynamic parameters for the amorphous and crystalline phases were extracted. These parameters were compared with those previously reported for evaporated, chemical vapor deposited, and self-implanted amorphous Si. We conclude that

Y. Masaki; P. G. LeComber; A. G. Fitzgerald

1993-01-01

69

Vapor-phase deposition studies of phosphate esters on metal and ceramic surfaces. Final report  

Microsoft Academic Search

This study focuses on a novel means of lubrication for ceramics and metals at high temperatures; called vapor-phase lubrication. The deposition rate and mechanisms of tributyl phosphate ester and tricresyl phosphate ester were explored. A thermalgravimetric analyzer (TGA) was modified to measure the rate of surface-film formation of vapor phase deposition of lubricants on metal surfaces at elevated temperatures. Results

D. E. Deckman; S. M. Hsu; E. E. Klaus

1988-01-01

70

VAPOR-PHASE 2,3,7,8-TCDD SORPTION TO PLANT FOILAGE - A SPECIES COMPARISON  

EPA Science Inventory

Plant uptake rate constants (k1) were determined for vapor-phase 2,3,7,8-TCDD using grass, azalea, spruce, kale and pepper foliage, and the fruit from apple, tomato and pepper. lants were exposed to vapor-phase 3H-2,3,7,8-TCDD for 96 h, and the TCDD sorption rate constant for eac...

71

Intensive use of biomass feedstock in ethanol conversion: The alcohol-water, vapor-phase separation  

Microsoft Academic Search

Fermentation of ethanol in a system whereby the biomass is used intensively (both to separate alcohol from water by vapor phase adsorption and to serve as the feedstock) is shown to be possible on theoretical grounds when the biomass is grain. The rationale for a vapor-phase adsorption process as an alternative to distillation is shown to be energetically valid above

George H. Robertson; Larry R. Doyle; Attila E. Pavlath

1983-01-01

72

Closed-loop phase diagrams, vaporization, and multicriticality in binary liquid mixtures  

Microsoft Academic Search

The coupled Potts-Ising models of Walker and Vause, which successfully describe closed-loop phase diagrams in hydrogen-bonding mixtures, are generalized to encompass the vapor phase, and are studied using position-space renormalization-group techniques. Global phase diagrams are generated, exhibiting such features as miscibility-immiscibility criticality, liquid-vapor critical points, critical end points, and bicritical and tricritical points. In addition, new types of phase diagrams

Robert G. Caflisch; J. S. Walker

1983-01-01

73

Calibration of an explosives vapor generator based on vapor diffusion from a condensed phase.  

National Technical Information Service (NTIS)

In the field of explosives detection there is currently a need for a calibrated source of explosives vapor. Such a source could be used to test and calibrate explosives detection systems which identify explosives via the collection of vapor or air borne p...

J. E. Parmeter G. A. Eiceman D. A. Preston G. S. Tiano

1996-01-01

74

The nuclear liquid-vapor phase transition: Equilibrium between phases or free decay in vacuum?  

SciTech Connect

Recent analyses of multifragmentation in terms of Fisher's model and the related construction of a phase diagram brings forth the problem of the true existence of the vapor phase and the meaning of its associated pressure. Our analysis shows that a thermal emission picture is equivalent to a Fisher-like equilibrium description which avoids the problem of the vapor and explains the recently observed Boltzmann-like distribution of the emission times. In this picture a simple Fermi gas thermometric relation is naturally justified. Low energy compound nucleus emission of intermediate mass fragments is shown to scale according to Fisher's formula and can be simultaneously fit with the much higher energy ISiS multifragmentation data.

Phair, L.; Moretto, L.G.; Elliott, J.B.; Wozniak, G.J.

2002-11-14

75

Cellulose nitrate membrane formation via phase separation induced by penetration of nonsolvent from vapor phase  

Microsoft Academic Search

In this paper, the membrane formation containing cellulose nitrate\\/acetone solution without or with an additive reagent (glycerol) by the phase inversion process was studied. The forming mechanism of the ‘cellular surface’ structure was investigated by visualizing the different structures of the vapor-contacting surface, the cross-section and the glass-side surface of the membranes as well as differences in the whole porosity

Haixiang Sun; Shengnan Liu; Baosheng Ge; Li Xing; Huanlin Chen

2007-01-01

76

A review of porous media enhanced vapor-phase diffusion mechanisms, models, and data: Does enhanced vapor-phase diffusion exist?  

SciTech Connect

A review of mechanisms, models, and data relevant to the postulated phenomenon of enhanced vapor-phase diffusion in porous media is presented. Information is obtained from literature spanning two different disciplines (soil science and engineering) to gain a diverse perspective on this topic. Findings indicate that while enhanced vapor diffusion tends to correct the discrepancies observed between past theory and experiments, no direct evidence exists to support the postulated processes causing enhanced vapor diffusion. Numerical modeling analyses of experiments representative of the two disciplines are presented in this paper to assess the sensitivity of different systems to enhanced vapor diffusion. Pore-scale modeling is also performed to evaluate the relative significance of enhanced vapor diffusion mechanisms when compared to Fickian diffusion. The results demonstrate the need for additional experiments so that more discerning analyses can be performed.

Ho, C.K.; Webb, S.W.

1996-05-01

77

EPR study of the toxicological effects of gas-phase cigarette smoke and the protective effects of grape seed extract on the mitochondrial membrane  

Microsoft Academic Search

Electron paramagnetic resonance spin trapping and spin labeling techniques were used to study the effects of grape seed extract\\u000a on the biophysical propertiers of the mitochondrial membrane exposed to gas-phase cigarette smoke. The spin trapping results\\u000a indicated that grape seed extract can effectively scavenge free radicals in cigarette smoke and the lipid free radicals generated\\u000a from the lipid peroxidation of

J. Gao; H. Tang; Y. Li; H. Liu; B. Zhao I

2002-01-01

78

Nanostructure-based optoelectronic sensing of vapor phase explosives - a promising but challenging method.  

PubMed

Optoelectronic sensing of gas phase hazardous chemicals is a newly explored field, which shows great advantages towards low concentration sensing when compared to normal gas sensing in the dark. Here, based on the recent progress on nanostructured vapor phase explosive gas sensors operated in dark conditions, the attractiveness of developing optoelectronic sensors for vapor phase explosive detection was highlighted. Furthermore, we try to propose some new insights to enhance optoelectronic sensing of vapor phase explosives. We suggest employing photocatalysis principles to enhance the sensitivity and employing a molecular imprinting technique (MIT) to enhance the selectivity. PMID:24072058

Zu, Baiyi; Guo, Yanan; Dou, Xincun

2013-09-26

79

Liquid-vapor phase diagram of metals using EAM potential  

NASA Astrophysics Data System (ADS)

Pair-wise additive potentials are not adequate to describe the properties of metallic systems since many body effects are completely ignored in that approximation. In this regard, the embedded atom method is more appropriate because, in addition to the pair interaction, the total energy includes an embedding energy which is the energy required to add an impurity atom to the host electron fluid. Thus EAM takes into account the many body effects to some extent. We use the Cai and Ye's EAM potential to predict the liquid vapor phase diagram and critical constants of Aluminum and Copper within a perturbation theory approach. In this method, free energy of a fluid molecule, trapped in a cage formed by its nearest neighbors, is expanded about a hard sphere reference system. The first order correction term is calculated in terms of the zero temperature isotherm of the solid obtained using the EAM potential. Higher order correction terms are added to account for the deviation of the behavior of the real fluid from the reference hard sphere fluid.

Bhattacharya, Chandrani

2013-02-01

80

Non-aqueous phase liquid spreading during soil vapor extraction  

PubMed Central

Many non-aqueous phase liquids (NAPLs) are expected to spread at the air – water interface, particularly under non-equilibrium conditions. In the vadose zone, this spreading should increase the surface area for mass transfer and the efficiency of volatile NAPL recovery by soil vapor extraction (SVE). Observations of spreading on water wet surfaces led to a conceptual model of oil spreading vertically above a NAPL pool in the vadose zone. Analysis of this model predicts that spreading can enhance the SVE contaminant recovery compared to conditions where the liquid does not spread. Experiments were conducted with spreading volatile oils hexane and heptane in wet porous media and capillary tubes, where spreading was observed at the scale of centimeters. Within porous medium columns up to a meter in height containing stagnant gas, spreading was less than ten centimeters and did not contribute significantly to hexane volatilization. Water film thinning and oil film pinning may have prevented significant oil film spreading, and thus did not enhance SVE at the scale of a meter. The experiments performed indicate that volatile oil spreading at the field scale is unlikely to contribute significantly to the efficiency of SVE.

Kneafsey, Timothy J.; Hunt, James R.

2010-01-01

81

VALIDATION OF CHEMICAL AND BIOLOGICAL TECHNIQUES FOR EVALUATION OF VAPORS IN AMBIENT AIR/MUTAGENICITY TESTING OF TWELVE (12) VAPOR-PHASE COMPOUNDS  

EPA Science Inventory

The overall objective of this research was to further validate Ames mutagenicity preincubation system for detection of vapors in ambient air. Parametes for detection of vapors in the Ames/Salmonella mutagenicity assay were investigated and 12 vapor-phase compounds were tested for...

82

Calibration of an explosives vapor generator based on vapor diffusion from a condensed phase  

SciTech Connect

Development of a vapor generator for consistently producing accurate amounts of vapor from low vapor pressure explosive materials is a pressing need within the explosives detection community. Of particular importance for reproducibility and widespread acceptance of results is the correlation of such a vapor generator to a National Institute of Standards and Technology (NIST) mass standard. This paper describes an explosives vapor generator recently developed at Varian in which a solid explosive sample in a precision bore glass tube is put in an oven at constant temperature, and vapor diff-using from the top of the tube is entrained in a carrier gas flow. The rate of vapor output is thus dependent on both the equilibrium vapor pressure of the solid at oven temperature and the rate of diffusion up the length of the tube. Correlation to a NIST mass standard is achieved by periodic weighing of the sample tube on a microbalance. We report results obtained with the explosives TNT and RDX. Results for TNT show that the mass output rate is constant over hundreds of hours of continuous use, with outputs of {approximately} 10--2000 pg/sec for oven temperatures in the range of 60--120{degrees}C. Both the mass loss experiments and calibration with an ion mobility spectrometer (IMS) give a TNT mass output value of 85 pg/sec at 79{degrees}C, and this result is supported by transport theory calculations. Mass loss curves for RDX are also linear with time, and show the expected exponential increase of mass output with oven temperature.

Parmeter, J.E.; Rhykerd, L. Jr.; Conrad, F.J. [Sandia National Labs., Albuquerque, NM (United States); Tiano, G.S.; Preston, D.; Eiceman, G.A. [New Mexico State Univ., Las Cruces, NM (United States). Dept. of Chemistry and Biochemistry; Arnold, J.T. [Varian Associates, Palo Alto, CA (United States). Ginzton Research Laboratory

1995-12-31

83

Continuous determination of high-vapor-phase concentrations of tetrachloroethylene using on-line mass spectrometry.  

PubMed

A method was developed to determine the vapor concentration of tetrachloroethylene (PCE) at and below its equilibrium vapor-phase concentration, 168 000 microg/L (25 degrees C). Vapor samples were drawn by vacuum into a six-port sampling valve and injected through a jet separator into an ion trap mass spectrometer (MS). This on-line MS can continuously sample a vapor stream and provide vapor concentrations every 30 s. Calibration of the instrument was done by creating a saturated stream of PCE vapor, sampling the vapor with the on-line MS and with thermal desorption tubes, and correlating the peak area response from the MS with the vapor concentration determined by automated thermal desorption gas chromatography mass spectrometry. Dilution of the saturated stream provided lower concentrations of PCE vapor. The method was developed to monitor the vapor concentration of PCE that was sparged from a two-dimensional flow chamber and for determination of the total PCE mass removed during each sparge event. The method has potential application for analysis of gas-phase tracers. PMID:18205332

Fine, Dennis; Brooks, Michael C; Bob, Mustafa; Mravik, Susan; Wood, Lynn

2008-01-19

84

Determination of partition coefficients by automatic equilibrium headspace gas chromatography by vapor phase calibration  

Microsoft Academic Search

Equilibrium headspace gas chromatography has been applied to the determination of the partition coefficients of volatile compounds in water-air systems. Only techniques that are suited to a fully automatic headspace procedure using the pneumatic headspace sampling-technique have been considered. Particularly simple is the technique of “vapor phase calibration —VPC” where an external vapor standard is used to calibrate the concentration

B. Kolb; C. Welter; C. Bichler

1992-01-01

85

Vapor-Phase Lubricants: Nanometer-Scale Mechanisms and Applications to Sub-micron Machinery.  

National Technical Information Service (NTIS)

TCP (tricresylphosphate) is a high-temperature vapor-phase lubricant, known for its demonstrated anti-wear properties for macroscopic systems and potential for MEMS applications. We have performed adsorption measurements of TCP on high purity iron and chr...

J. Krim

2004-01-01

86

Enhanced Vapor-Phase Diffusion in Porous Media - LDRD Final Report.  

National Technical Information Service (NTIS)

As part of the Laboratory-Directed Research and Development (LDRD) Program at Sandia National Laboratories, an investigation into the existence of enhanced vapor-phase diffusion (EVD) in porous media has been conducted. A thorough literature review was in...

C. K. Ho S. W. Webb

1999-01-01

87

Phase Behavior and Vapor Pressures of the Pyrene + 9,10-Dibromoanthracene System  

PubMed Central

The present work concerns the thermochemical and vapor pressure behavior of the pyrene + 9,10-dibromoanthracene system. The phase diagram of the system has been studied using the thaw melt method and the results show the formation of non-eutectic multiphase mixtures. The temperatures of crystallization, and enthalpies of fusion and crystallization of the system were determined by differential scanning calorimetry. The system behavior can be divided into 5 regions. The X-ray diffraction results also indicated the existence of multiple phase characteristics. The solid-vapor equilibrium studies showed that for mixtures with high mole fractions of pyrene, two different preferred states exist that determine the vapor pressure. For those mixtures with moderate and low mole fractions of pyrene, only one preferred state exists that determines vapor pressure behavior. It was also demonstrated that the vapor pressure of the mixtures is independent of the mixture preparation technique.

Fu, Jinxia; Rice, James W.; Suuberg, Eric M.

2010-01-01

88

Micro vapor-phase hydrogenation monitored with tanden chromatography-radioactivity: III. Isomeric monoenes  

Microsoft Academic Search

Micro vapor-phase hydrogenation and radiotracer techniques have been utilized to investigate the effect of geometric configuration\\u000a and double bond position on the rate of hydrogenation of octadecenoates. These techniques provide for simultaneously monitoring\\u000a the time course of vapor-phase hydrogenation both for an essentially pure monoene isomer by thermal conductivity and for methyl\\u000a oleate by radioactivity. The two hydrogenations proceed independently

T. L. Mounts; R. O. Butterfield; C. R. Scholfield; H. J. Dutton

1970-01-01

89

Microwave heated vapor-phase digestion method for biological sample materials  

Microsoft Academic Search

A microwave heated, vapor-phase nitric acid-hydrogen peroxide digestion method for pulverized, biological sample materials\\u000a was developed. Sample masses up to 200 mg were digested using calibrated quartz inserts inside first generation type, low-pressure,\\u000a Teflon-PFA microwave vessels. In the first step, samples were digested in the vapor-phase for 80 min using a progressive heating\\u000a pattern. Three mL of 70% nitric acid

K. Eilola; P. Perämäki

2001-01-01

90

Making inert polypropylene fibers chemically responsive by combining atomic layer deposition and vapor phase chemical grafting  

NASA Astrophysics Data System (ADS)

Uniformly grafting organic reactive molecular species, e.g. -NH2, onto substrates that have three-dimensional complex structures and are chemically inert is challenging. The vapor phase chemical grafting of organic molecules enabled by low temperature metal oxide atomic layer deposition (ALD) is presented as a general and promising solution to functionalize inert matrices with complex morphology, such as nonwoven polypropylene mats, through the controllable self-limited molecular assembly mechanism in a combined ALD and vapor phase chemical grafting process.

Peng, Qing; Gong, Bo; Parsons, Gregory N.

2011-04-01

91

Cigarette filter as sorbent for on-line coupling of solid-phase extraction to high-performance liquid chromatography for determination of polycyclic aromatic hydrocarbons in water  

Microsoft Academic Search

An on-line solid-phase extraction (SPE) protocol using the cigarette filter as sorbent coupled with high-performance liquid chromatography (HPLC) was developed for simultaneous determination of trace naphthalene (NAPH), phenanthrene (PHEN), anthracene (ANT), fluoranthene (FLU), benzo(b)fluoranthene (BbF), benzo(k)fluoranthene (BkF), benzo(a)pyrene (BaP), and benzo(ghi)perylene (BghiP) in water samples. To on-line interface solid-phase extraction to HPLC, a preconcentration column packed with the cigarette filter

Hua-Ding Liang; De-Man Han; Xiu-Ping Yan

2006-01-01

92

Vapor-Phase Thermal Conductivity, Vapor Pressure, and Liquid Density of R365mfc  

Microsoft Academic Search

The thermal conductivity of a new fluoroalkane, R365mfc (1,1,1,3,3-pentafluorobutane), important for the production of polyurethane rigid foams, was measured using a transient hot wire method, at temp- eratures between 336.85 K and 377.4 K. The extended corresponding states theory was used successfully to predict the results, with an average absolute deviation of 0.5%. The vapor pressure (302.90 K to 358.15

Isabel M. Marrucho; Nelson S. Oliveira; Ralf Dohrn

2002-01-01

93

Closed-loop phase diagrams, vaporization, and multicriticality in binary liquid mixtures  

SciTech Connect

The coupled Potts-Ising models of Walker and Vause, which successfully describe closed-loop phase diagrams in hydrogen-bonding mixtures, are generalized to encompass the vapor phase, and are studied using position-space renormalization-group techniques. Global phase diagrams are generated, exhibiting such features as miscibility-immiscibility criticality, liquid-vapor critical points, critical end points, and bicritical and tricritical points. In addition, new types of phase diagrams are found, involving upper and lower azeotropes, for example, which are expected to be physically realizable in experimental systems.

Caflisch, R.G.; Walker, J.S.

1983-09-01

94

Student Understanding of Liquid-Vapor Phase Equilibrium  

ERIC Educational Resources Information Center

|Student understanding of the equilibrium coexistence of a liquid and its vapor was the subject of an extended investigation. Written assessment questions were administered to undergraduates enrolled in introductory physics and chemistry courses. Responses have been analyzed to document conceptual and reasoning difficulties in sufficient detail to…

Boudreaux, Andrew; Campbell, Craig

2012-01-01

95

Student Understanding of Liquid-Vapor Phase Equilibrium  

ERIC Educational Resources Information Center

Student understanding of the equilibrium coexistence of a liquid and its vapor was the subject of an extended investigation. Written assessment questions were administered to undergraduates enrolled in introductory physics and chemistry courses. Responses have been analyzed to document conceptual and reasoning difficulties in sufficient detail to…

Boudreaux, Andrew; Campbell, Craig

2012-01-01

96

Determination of oxides of nitrogen (NO/sub x/) in cigarette smoke by chemiluminescent analysis  

SciTech Connect

The successful application of a commercial chemiluminescent No/sub x/ analyzer to the determination of oxides of nitrogen in cigarette smoke is reported. Individual puffs of the smoke vapor phase are rapidly diluted in an air stream before introduction into the analyzer. This acts to both reduce quenching of the chemiluminescent response by CO/sub 2/ and to prevent side reactions of the NO/sub x/ with vapor phase organic constituents. Sweeping the dilute smoke through a reduced silver-ion exchange resin bed removed a substantial positive interference from hydrogen cyanide. A range of deliveries of 3 to 47 ..mu..mol of NO/sub x/ per cigarette was observed for nine types of experimental cigarettes. Statistically significant differences between NO/sub x/ and NO levels (NO/sub x/ - NO = NO/sub 2/) in smoke were observed in only one type of cigarette, presumably due to large cigarette-to-cigarette variability in constituent deliveries. 2 figures, 3 tables.

Jenkins, R.A.; Gill, B.E.

1980-05-01

97

Vapor Pressure, Speed of Sound, and PVT Properties of R-404a in the Vapor Phase  

Microsoft Academic Search

The density (300–363 K, up to 3.5 MPa) and speed of sound (293–373 K, 7.5–480 kPa) in gaseous R-404a have been studied by\\u000a an isochoric piezometer method and an ultrasonic interferometer, respectively. The pressures of the saturated vapor along\\u000a the dew line were measured from 298 to 330 K. The experimental uncertainties of the temperature, pressure, density, and speed-of-sound\\u000a measurements were estimated to be within

V. A. Gruzdev; S. G. Komarov; S. V. Stankus

2008-01-01

98

LLNL vapor phase manufacturing progress report, June--December 1995  

SciTech Connect

This report gives progress made on the following milestones: demonstrate Ti and Nb monitoring at 3M site, demonstrate Al monitoring at LLNL, complete baseline melt and vapor plume model for the metal matrix process (3M fiber coating process), prototype a laser at LLNL to monitor Cu, ZrO{sub 2} monitoring demonstration at LLNL, Se monitoring demonstration, and process scale-up study for YBCO high-temperature superconductor.

Anklam, T.; Benterou, J.; Berzins, L.; Braun, D.; Haynam, C.; Heestand, G.; McClelland, M.

1996-01-09

99

Producing titanium powder by continuous vapor-phase reduction  

Microsoft Academic Search

One of the goals of the U.S. Department of Energy's Albany Research Center is to reduce the cost of titanium parts by developing a continuous titanium process. In this work, titanium powder was produced by feeding liquid TiCl4, with argon as a carrier gas, and magnesium wire into a shaft reactor at 1,000°C. The magnesium and TiCl4 vaporized and reacted

Dennis A. Hansen; Stephen J. Gerdemann

1998-01-01

100

Producing titanium powder by continuous vapor-phase reduction  

Microsoft Academic Search

One of the goals of the U.S. Department of Energy’s Albany Research Center is to reduce the cost of titanium parts by developing\\u000a a continuous titanium process. In this work, titanium powder was produced by feeding liquid TiCl4, with argon as a carrier gas, and magnesium wire into a shaft reactor at 1,000C. The magnesium and TiCl4 vaporized and reacted

Dennis A. Hansen; Stephen J. Gerdemann

1998-01-01

101

Possibility of metallic intercalation of transition-metal dichalcogenide crystals during their growth from vapor phase  

SciTech Connect

The proper thermodynamic characteristics of vapor-transport systems, used for simultaneous processes of growth and intercalation of layered crystals, may be determined directly from tensimetric investigations of heterogeneous equilibria in dichalcogenide layered structure-intercalating metal-transport agent systems. It serves the purpose of optimizing the deposition conditions of intercalates from the vapor phase. Investigation of the simultaneous growth and intercalation processes of layered crystals reveals the possibility of producing layered crystals with alternate layers of intercalating metals in streaming vapor-transport systems and of creating different physical properties in the bulk of the matrix through sandwiching.

Kulikov, L.M.

1987-09-01

102

Desorption efficiencies of vapor phase polynuclear aromatic compounds on solid adsorbents  

SciTech Connect

Polynuclear aromatic compounds (PNAs) in the vapor phase can be collected by adsorption onto solid adsorbents. This paper reports the results of a study using several liquid and gas chromatographic packing materials to determine their applicability for vapor phase sampling of PNAs. The desorption procedure for PNAs from the solid adsorbents involves extraction with non-polar organic solvents. The desorption efficiency for each adsorbent is evaluated using gas chromatography. The combined adsorption/desorption (recovery) efficiency of several adsorbents was evaluated. These adsorbents can be grouped into four classifications: (1) carbon or charcoal, (2) macroreticular resins such as Tenax GC or the XAD-series, (3) adsorbents solids such as silica, alumina, and Florisil, and (4) bonded-phases on silica such as C/sub 18/. The resin XAD-8 was found to be most suitable for sampling vapor phase PNAs as a result of its high adsorption desorption efficiency and good reproducibility.

Timmons, K.D.; Karlesky, D.; Johnson, E.; Warner, I.M.

1984-01-01

103

Possibility of metallic intercalation of transition-metal dichalcogenide crystals during their growth from vapor phase  

Microsoft Academic Search

The proper thermodynamic characteristics of vapor-transport systems, used for simultaneous processes of growth and intercalation of layered crystals, may be determined directly from tensimetric investigations of heterogeneous equilibria in dichalcogenide layered structure-intercalating metal-transport agent systems. It serves the purpose of optimizing the deposition conditions of intercalates from the vapor phase. Investigation of the simultaneous growth and intercalation processes of layered

Kulikov

1987-01-01

104

The space–time CESE method applied to phase transition of water vapor in compressible flows  

Microsoft Academic Search

The space–time CESE method has been used to simulate phase transition of water vapor in compressible flows. The governing equations consists 1-D Euler equations and four equations from the method of moments of the size distribution function, which deal with the homogeneous condensation or evaporation. The source terms due to the phase transition are integrated in time either explicitly by

Xisheng Luo; Meili Wang; Jiming Yang; Ge Wang

2007-01-01

105

Investigation of local evaporation flux and vapor-phase pressure at an evaporative droplet interface.  

PubMed

In the steady-state experiments of water droplet evaporation, when the throat was heating at a stainless steel conical funnel, the interfacial liquid temperature was found to increase parabolically from the center line to the rim of the funnel with the global vapor-phase pressure at around 600 Pa. The energy conservation analysis at the interface indicates that the energy required for evaporation is maintained by thermal conduction to the interface from the liquid and vapor phases, thermocapillary convection at interface, and the viscous dissipation globally and locally. The local evaporation flux increases from the center line to the periphery as a result of multiple effects of energy transport at the interface. The local vapor-phase pressure predicted from statistical rate theory (SRT) is also found to increase monotonically toward the interface edge from the center line. However, the average value of the local vapor-phase pressures is in agreement with the measured global vapor-phase pressure within the measured error bar. PMID:19371050

Duan, Fei; Ward, C A

2009-07-01

106

Surface morphology and chemical characterization of Si surfaces prepared with HF/alcohol vapor phase chemistries  

NASA Astrophysics Data System (ADS)

The surface affects of HF/alcohol vapor phase cleaning of Si at ambient pressure in a batch process or single wafer process at low pressures (5--50 Torf) in ambient temperature an investigated. Residue island formation on the silicon surface as a result of cleaning with HF/alcohol vapor phase chemistries was observed with atomic force microscopy. While particle generation during the vapor cleaning process was suppressed, a new surface defect arose in the form of residue islands due to the vapor cleaning process Secondary ion mass spectroscopy (SIMS) was employed to characterize the elemental concentrations of O, C, F, and N in the passivating oxide layers. A correlation between oxide purity and residue island density was observed. Results indicate that the density of the residue islands remaining upon the surface was dependent upon the nitrogen concentration in the passivating oxide that was etched. SIMS and lateral force microscopy (LFM) were used to deduce the chemical composition of the residue islands. It was determined that the residual islands consisted of silicon and nitrogen atoms. Combining experimental data obtained via AFM, LFM and SIMS analysis, a model for residue island formation is proposed. After developing a model for the residue island nucleation, a vapor cleaning process was developed which was able to suppress the formation of residue islands. It was found that by exposing the oxide surface to methanol vapor first and then to AHF resulted in clean, residue-free Si surfaces. However, this technique proved successful only for vapor etching UV-ozone oxides. In the case of using the two step technique to etch chemical oxides, an anneal of the oxide was necessary prior to vapor cleaning, in order to achieve residue-free surfaces. Alternative surface preparation chemistries were also investigated to achieve residue-free, surfaces. Vapor etching oxides grown via dilute RCA or SC-2 chemistries resulted in residue-free surfaces.

Carter, Richard Jerome

1999-11-01

107

Reaction kinetics of ethylene glycol reforming over platinum in the vapor versus aqueous phases  

SciTech Connect

First-principles, periodic, density functional theory (DFT) calculations are carried out on Pt(111) to investigate the structure and energetics of dehydrogenated ethylene glycol species and transition states for the cleavage of C-H/O-H and C-C bonds. Additionally, reaction kinetics studies are carried out for the vapor phase reforming of ethylene glycol (C{sub 2}H{sub 6}O{sub 2}) over Pt/Al{sub 2}O{sub 3} at various temperatures, pressures, and feed concentrations. These results are compared to data for aqueous phase reforming of ethylene glycol on this Pt catalyst, as reported in a previous publication (Shabaker, J. W.; et al. J. Catal. 2003, 215, 344). Microkinetic models were developed to describe the reaction kinetics data obtained for both the vapor-phase and aqueous-phase reforming processes. The results suggest that C?C bond scission in ethylene glycol occurs at an intermediate value of x (3 or 4) in C{sub 2}H{sub x}O{sub 2}. It is also found that similar values of kinetic parameters can be used to describe the vapor and aqueous phase reforming data, suggesting that the vapor phase chemistry of this reaction over platinum is similar to that in the aqueous phase over platinum.

Kandoi, S.; Greeley, J.; Simonetti, D.; Shabaker, J.; Dumesic, J. A.; Mavrikakis, M. (Center for Nanoscale Materials); (Univ. of Wisconsin at Madison)

2011-01-01

108

Application of Exciplex Chemical Sensor for Visualization of Liquid- and Vapor-Phase Fuel Distribution  

NASA Astrophysics Data System (ADS)

Two-dimensional slices of the cross-sectional distributions of fuel images in the combustion chamber were visualized quantitatively using a laser-induced exciplex fluorescence technique. A new exciplex visualization system consisting of 5% N,N-dimethylaniline (DMA)\\cdot5%1,4,6-trimethylnaphthalene (TMN) in 90% isooctane (2,2,4-trimethylpentane) fuel was employed. In this method, the vapor phase was tagged by the monomer fluorescence while the liquid phase was tracked by the exciplex fluorescence with good spectral and spatial resolution. The 308 nm (XeCl) line of an excimer laser was used to excite the doped molecules in the fuel and the resulting fluorescence images were obtained with an intensified charge coupled device (ICCD) detector as a function of time. The results demonstrate that at the end of the compression stroke, the liquid fuel was almost vaporized and a dense stratified vapor phase charge developed near the two spark plugs.

Kim, Jong-Uk; Kim, Guang-Hoon; Suk, Hyyong

2002-02-01

109

Kinetic Analysis of InN Selective Area Metal--Organic Vapor Phase Epitaxy  

NASA Astrophysics Data System (ADS)

The selective area metal--organic vapor phase epitaxy (SA-MOVPE) of InN was realized and its kinetics was investigated. InN deposition selectivity between the mask and the crystal surface was found to strongly depend on the growth temperature, and good selectivity was obtained above 600 °C. Under this growth condition, the thickness profile of InN between the masks exhibited a catenary shape, which resulted from the vapor phase diffusion. This fact shows that vapor phase diffusion is the dominant supply mechanism in InN SA-MOVPE as well as for the growth of GaN and InGaAsP. These kinetic analysis will contribute to the development of monolithically integrated AlInGaN-based devices.

Shioda, Tomonari; Sugiyama, Masakazu; Shimogaki, Yukihiro; Nakano, Yoshiaki

2008-07-01

110

[Estimation of ethanol concentrations in biological media. Comparison of alkylnitrite and direct vapor-phase methods].  

PubMed

Ethanol assays in the blood, saliva and urine were made according to two methods: alkylnitrite gas-liquid chromatography and direct vapor-phase method without thermostating. N-propanol was used as an internal standard. For saliva and urine the methods produced similar results. For blood, the direct vapor-phase method detected significantly lower level of ethanol compared to alkylnitrite one (p = 0.001). 24-h storage of the samples in refrigerator does not deviate the results. Recommendations are provided for most effective usage of each method. PMID:17191726

Barinskaia, T O; Tiurin, I A; Smirnov, A V

111

Effect of vapor phase corrosion inhibitor on microbial corrosion of aluminum alloys.  

PubMed

Vapor phase corrosion inhibitors were used to investigate the antimicrobial activities and anticorrosion of aluminum alloy. Aspergillus flavus, A. niger, A. versicolor, Chaetomium globosum and Penicillium funiculosum had moderate to abundant growth on the aluminum alloy AA 1100 at Aw 0.901, while there was less growth at Aw 0.842. High humidity stimulated microbial growth and induced microbial corrosion. Dicyclohexylammonium carbonate had a high inhibitory effect on the growth of test fungi and the microbial corrosion of aluminum alloy, dicyclohexylammonium caprate and dicyclohexylammonium stearate were the next. Aluminum alloy coating with vapor phase corrosion inhibitor could prevent microbial growth and retard microbial corrosion. PMID:10592784

Yang, S S; Ku, C H; Bor, H J; Lin, Y T

1996-02-01

112

Measurements of the thermal conductivity of refrigerants in the vapor phase  

SciTech Connect

Measurements of the thermal conductivity of refrigerants R124, R125, and R134a in the vapor phase are presented. The measurements, performed in a newly developed transient hot-wire instrument, cover a temperature range from 273 to 333 K, and a pressure range from about atmospheric up to below the saturation pressure. A finite-elements program developed allowed the reexamination of the major corrections employed in the analysis of the results. The uncertainty of the reported values is estimated to be better than {+-}1%. Comparisons with measurements of other investigators along the saturation line show a lack of reliable thermal conductivity data in the vapor phase for these compounds.

Assael, M.J.; Malamataris, N.; Karagiannidis, L. [Aristotle Univ., Thessaloniki (Greece). Faculty of Chemical Engineering

1997-03-01

113

Water vapor in the atmosphere: an examination for CARMA phase correction  

NASA Astrophysics Data System (ADS)

We report on the current progress of the water vapor radiometer (WVR) phase correction project for the Combined Array for Research in Millimeter-wave Astronomy (CARMA). CARMA is a new millimeter array that merges the Owens Valley Radio Observatory (OVRO) array, the Berkeley-Illinois-Maryland Association (BIMA) array and eventually the Sunyaev-Zel'dovich Array (SZA). WVRs are designed for phase correction by monitoring the water vapor in the atmosphere along the line of sight toward astronomical sources. In addition, we discuss the stability of the current OVRO water vapor radiometers in preparation for testing at the CARMA site. We will systematically analyze the receivers with atmospheric correlations to decouple the effects of instrumentation and atmospheric noise. Finally, we report on the status of the correlation receivers in development.

Shiao, Yu-Shao; Looney, Leslie W.; Woody, David P.; Plambeck, Richard L.; Bolatto, Alberto D.

2006-07-01

114

Large core Yb-doped optical fiber through vapor phase doping technique  

NASA Astrophysics Data System (ADS)

Rare earth (RE) doped optical fibers have shown tremendous progress for producing high power fiber lasers for industrial, medical and strategic applications. However, fabrication of large core, high Yb-doped fiber is still a challenge through conventional process due to poor repeatability and limitation regarding core size. This paper presents successful fabrication of Yb-doped fibers through vapor phase doping technique. Preform fabrication was carried out using a specially constructed MCVD system containing High Temperature Vapor Delivery Unit with sublimators for Al and Yb precursors. The novelty of the present work lies in deposition of Al2O3 and Yb2O3 in vapor phase simultaneously with silica during formation of sintered core layer which result in uniform dopants distribution in the preform. The fibers exhibited lasing efficiency of 76% with low `photodarkening effect'.

Saha, Maitreyee; Pal, Atasi; Pal, Mrinmay; Sen, Ranjan

2013-05-01

115

Effects of very rapid versus vapor phase freezing on human sperm parameters.  

PubMed

The aim of the present study was to compare the effects of two freezing methods, vapor phase and very rapid freezing, with and without cryoprotectant on semen parameters in men with normal semen criteria. Cryopreservation was done on semen samples from 31 men by two methods of vapor phase freezing and very rapid freezing, with and without Test Yolk buffered glycerol (TYBG) as cryoprotectant. The motility, viability, acrosome and DNA integrity were evaluated on fresh and post-thaw samples. Post-thaw sperm progressive motility was significantly higher in the presence of TYBG in the vapor phase cryopreservation (%6.30 ± 3.74) compared with the very rapid freezing method (%2.2 ± 1.97 and %4.00 ± 2.42 in the presence and absence of TYBG, respectively). There was no significant difference in viability, acrosome status and DNA integrity between two methods in presence or absence of TYBG. The very rapid freezing method in the absence of TYBG showed better sperm motility but viability, acrosome and DNA integrity were similar to the presence of TYBG. The results show that cryopreservation of human spermatozoa together with seminal plasma by using vapor phase method is better than very rapid freezing method to preserve sperm progressive motility; however very rapid freezing method is quick and simple and do not require special cryoprotectant. It can be used for cryopreservation of small number of spermatozoa in IVF centers. PMID:23184170

Darvishnia, Hamid; Lakpour, Niknam; Lahijani, Maryam Shams; Heidari-Vala, Hamed; Akhondi, Mohammad A; Zeraati, Hojjat; Sadeghi, Mohammad Reza

2012-11-25

116

Synthesis of dimethyl carbonate by vapor phase oxidative carbonylation of methanol over Cu-based catalysts  

Microsoft Academic Search

Dimethyl carbonate (DMC) synthesis reaction by oxidative carbonylation of methanol has been studied using vapor phase flow reaction system in the presence of Cu-based catalysts. A series of Cu-based catalysts were prepared by the conventional impregnation method using activated carbon (AC) as support. The effect of various promoters and reaction conditions on the catalytic reactivities were intensively evaluated in terms

Man Seok Han; Byung Gwon Lee; Insuk Suh; Hoon Sik Kim; Byoung Sung Ahn; Suk In Hong

2001-01-01

117

Vapor phase sorbent precursors for toxic metal emissions control from combustors  

Microsoft Academic Search

A bench scale system incorporating a high temperature flow reactor has been utilized to study the reaction of metallic species and sorbent compounds. The reaction and interaction between a lead precursor and a vapor phase silica precursor is studied. The effect of chlorine and the effect of sorbent to metal feed ratio on lead speciation and size distribution is determined.

Timothy M. Owens; Pratim Biswas

1996-01-01

118

SIMULTANEOUS ABSORPTION OF VAPOR PHASE POLYCYCLIC AROMATIC HYDROCARBON AND CARBON DIOXIDE IN ANIONIC SURFACTANT SOLUTIONS  

Microsoft Academic Search

The goal of this work was to investigate whether the solubility of vapor phase polycyclic aromatic compounds (PAHs) and CO2 in water could be enhanced by adding anionic surfactant during the absorption process. Naphthalene was the PAH surrogate and sodium dodecyl sulfate (SDS) was the anionic surfactant. A series of batch experiments in an absorption cell were performed at 50°C

Hsiao-Lin Huang; Whei-May Grace Lee

2001-01-01

119

Vapor-phase bioreactors: Avoiding problems through better design and operation  

Microsoft Academic Search

Vapor-phase bioreactors are an efficient method to treat air contaminated with volatile organic compounds. To ensure stable long term performance, several design and operating factors must be considered. Common problems include nutrient limitations, biomass clogging, inactive biomass, low moisture content and reductions in pH. Based on several bioreactor studies, the underlying cause of each of these problems is identified, monitoring

K. A. Kinney; R. C. Loehr; R. L. Corsi

1999-01-01

120

DEVELOPMENT OF AN AIR-TO-LEAF VAPOR PHASE TRANSFER FACTOR FOR DIOXINS AND FURANS  

EPA Science Inventory

Results of an experiment in which grass was grown in a greenhouse and outdoors, and in soils of different concentration levels of dioxins and furans, were used in a modeling exercise to derive an air-to-leaf vapor phase transfer factor. The purpose of the experiment was to under...

121

Vapor-phase fabrication of ?-iron oxide nanopyramids for lithium-ion battery anodes.  

PubMed

The other polymorph: A vapor-phase route for the fabrication of ?-Fe(2)O(3) nanomaterials on Ti substrates at 400-500 °C is reported. For the first time, the ? polymorph is tested as anode for lithium batteries, exhibiting promising performances in terms of Li storage and rate capability. PMID:23097215

Carraro, Giorgio; Barreca, Davide; Cruz-Yusta, Manuel; Gasparotto, Alberto; Maccato, Chiara; Morales, Julián; Sada, Cinzia; Sánchez, Luis

2012-10-23

122

Organometallic Vapor Phase Epitaxy of Zinc Selenide: Growth and Doping Studies  

Microsoft Academic Search

ZnSe at present is the most promising material for the commercial fabrication of blue light emitting devices. The successful fabrication and performance of these blue light emitting devices depends primarily on the structural, optical and electrical properties of the materials used to fabricate them. This study involves the epitaxial growth of ZnSe by organometallic vapor phase epitaxy (OMVPE) and the

Salman Akram

1994-01-01

123

POTENTIAL USE AND MODIFICATION OF EXISTING MESOCOSMS FOR VAPOR PHASE PHOTOTOXICITY  

EPA Science Inventory

With vapor phase plant toxicity testing becoming a requirement in Europe, there is a pressing need to develop and implement acceptable tests protocols. The quickest way to proceed is to examine and modify existing methodologies while determining if new technologies are needed. ...

124

Magnetic resonance imaging of nonaqueous phase liquid during soil vapor extraction in heterogeneous porous media  

Microsoft Academic Search

Soil vapor extraction (SVE) is commonly used to remediate nonaqueous phase liquids (NAPLs) from the vadose zone. This paper aims to determine the effect of grain size heterogeneity on the removal of NAPL in porous media during SVE. Magnetic resonance imaging (MRI) was used to observe and quantify the amount and location of NAPL in flow-through columns filled with silica

Yanjie Chu; Charles J. Werth; Albert J. Valocchi; Hongkyu Yoon; Andrew G. Webb

2004-01-01

125

MODELING THE REBOUNDING OF CONTAMINANT CONCENTRATIONS IN SUBSURFACE GASEOUS PHASE DURING INTERMITTENT SOIL VAPOR EXTRACTION OPERATION  

Microsoft Academic Search

Soil vapor extraction (SVE) process for contaminated soil remediation often shows a tailing of the breakthrough concentration in the contaminant plume and rebounding of gaseous phase concentration after a pause of the extraction operation. These phenomena are believed to have something to do with the limitation of mass transfer between mobile fluid and some stagnant aggregates or clay lens. An

Mei-Sheue Wang; Shian-Chee Wu; Chun-Wei Kuo

2007-01-01

126

Two-dimensional searching of unknowns using GC retention index data and vapor phase IR data  

Microsoft Academic Search

The use of capillary GC retention data as a second independent search dimension in the GC-FT-IR analyses of unknown samples is examined. A reference retention index library is used along with a reference vapor phase infrared library in order to improve and assist in the identification of unknown compounds.

Richard H. Shaps; Michael Boruta; Antonio Varano

1988-01-01

127

Analysis of TNT and related compounds in vapor and solid phase in different types of soil  

NASA Astrophysics Data System (ADS)

Trinitrotoluene (TNT) explosives contain small amounts of dinitrotoluene (DNT). DNT exhibit a higher vapor pressure than TNT which indicates higher concentration of DNT than of TNT in the vapor phase of the explosive. Analysis of soil samples reveal extended information compared to air samples and thereby increases the probability for chemical detection. Detected substances in soil samples are TNT and related compounds. Therefore, sampling of DNT in vapor phase near the ground or soil solid phase may be an efficient approach to detect buried land mines or unexploded ordnance (UXO) containing TNT. Charges of TNT has been placed both in desiccators ane in a set of different types of soil in the laboratory. Analysis of air samples repeatedly taken in desiccators during a period of 299 days shows a perpetually higher concentration of DNT than of TNT. TNT was also placed in outdoor test beds where the presence of DNT in vapor phase near to the ground were confirmed, as well as TNT and related compounds in soil samples. In mine affected areas, air sample near to the ground over buried miens and soil sampling near the same miens were performed.

Kjellstrom, Ann H.; Sarholm, Lena M.

2000-08-01

128

Failure analysis of heat exchanger fluid vapor phase vent lines in a Polyester plant  

Microsoft Academic Search

A Polyester plant is using Proprietary heat exchange fluids (26.5% biphenyl, 73.5% diphenyloxide). The plant hot condensate tank, condensate feed tank, and heat exchanger vapor phase dead end and ventable lines (ASTM 106 Grade B) with isolation valves were suffering frequent leakages with severe gouging and pitting corrosion. Lustrous (shiny) coke deposit was prominent inside the cut sections due to

M. A. Virk; M. A. Butt; A. Chughtai; M. Ahmad; I. H. Khan; K. M. Deen

2010-01-01

129

Selected Vapor Phase Sensing of Small Molecules Using Biofunctionalized Field Effect Transistors.  

National Technical Information Service (NTIS)

This work details a proof of concept study for vapor phase selective sensing using a strategy of biorecognition elements (BRE) integrated into a zinc oxide field effect transistor (ZnO FET). ZnO FETs are highly sensitive to changes to the environment with...

J. A. Hagen M. O. Stone N. Kelley-Loughnane R. R. Naik S. N. Kim

2012-01-01

130

Enhanced Vapor-Phase Diffusion in Porous Media - LDRD Final Report  

Microsoft Academic Search

As part of the Laboratory-Directed Research and Development (LDRD) Program at Sandia National Laboratories, an investigation into the existence of enhanced vapor-phase diffusion (EVD) in porous media has been conducted. A thorough literature review was initially performed across multiple disciplines (soil science and engineering), and based on this review, the existence of EVD was found to be questionable. As a

C. K. Ho; S. W. Webb

1999-01-01

131

Gallium hydride vapor phase epitaxy of GaN nanowires  

PubMed Central

Straight GaN nanowires (NWs) with diameters of 50 nm, lengths up to 10 ?m and a hexagonal wurtzite crystal structure have been grown at 900°C on 0.5 nm Au/Si(001) via the reaction of Ga with NH3 and N2:H2, where the H2 content was varied between 10 and 100%. The growth of high-quality GaN NWs depends critically on the thickness of Au and Ga vapor pressure while no deposition occurs on plain Si(001). Increasing the H2 content leads to an increase in the growth rate, a reduction in the areal density of the GaN NWs and a suppression of the underlying amorphous (?)-like GaN layer which occurs without H2. The increase in growth rate with H2 content is a direct consequence of the reaction of Ga with H2 which leads to the formation of Ga hydride that reacts efficiently with NH3 at the top of the GaN NWs. Moreover, the reduction in the areal density of the GaN NWs and suppression of the ?-like GaN layer is attributed to the reaction of H2 with Ga in the immediate vicinity of the Au NPs. Finally, the incorporation of H2 leads to a significant improvement in the near band edge photoluminescence through a suppression of the non-radiative recombination via surface states which become passivated not only via H2, but also via a reduction of O2-related defects.

2011-01-01

132

Are Published Minimum Vapor Phase Spark Ignition Energy Data Valid?  

SciTech Connect

The use of sprayed flammable fluids as solvents in dissolution and cleaning processes demand detailed understanding of ignition and fire hazards associated with these applications. When it is not feasible to inert the atmosphere in which the spraying process takes place, then elimination of all possible ignition sources must be done. If operators are involved in the process, the potential for human static build-up and ultimate discharge is finite, and it is nearly impossible to eliminate. The specific application discussed in this paper involved the use of heated Dimethyl Sulfoxide (DMSO) to dissolve high explosives (HE). Search for properties of DMSO yielded data on flammability limits and flash point, but there was no published information pertaining to the minimum energy for electrical arc ignition. Due to the sensitivity of this procedure, The Hazards Control Department of Lawrence Livermore National Laboratory (LLNL) was tasked to determine the minimum ignition energy of DMSO aerosol and vapor an experimental investigation was thus initiated. Because there were no electrical sources in spray chamber, Human Electro-Static Discharge (HESD) was the only potential ignition source. Consequently, the electrostatic generators required for this investigation were designed to produce electrostatic arcs with the defined voltage and current pulse characteristics consistent with simulated human capacitance. Diagnostic procedures required to insure these characteristics involve specific data gathering techniques where the voltage and current sensors are in close proximity to the electrodes, thus defining the arc energy directly between the electrodes. The intriguing finding derived from this procedure is how small these measured values are relative to the arc energy as defined by the capacitance and the voltage measure at the capacitor terminals. The suggested reason for this difference is that the standard procedure for determining arc energy from the relation; E = 1/2CV{sup 2} does not account for the total capacitance and impedance of the system.

Staggs, K J; Alvares, N J; Greenwood, D W

2001-11-21

133

Solid and Vapor Phase UV Photocathodes for Gaseous Detectors  

SciTech Connect

We measured the relative quantum efficiency of four organic materials: tetrathiafulvalene and bis(cyclopentadienyl)magnesium in the solidphase and t-butylferrocene and n-butylferrocene in the vapour phase. The measurements were performed in the wavelength range of 150-220 nm. We also present a new quantum efficiency measurement of ethylferrocene. The three ferrocene derivatives exhibit relatively high quantum efficiency.

Vasileiadis, G.; Malamud, G.; Mine, P.; Vartsky, D.; /Ecole Polytechnique

2012-09-20

134

In situ direct measurement of vapor pressures and thermodynamic parameters of volatile organic materials in the vapor phase: benzoic acid, ferrocene, and naphthalene.  

PubMed

We report the direct determination of vapor pressures and optical and thermodynamic parameters of powders of low-volatile materials in their vapor phase using a commercial UV/Vis spectrometer. This methodology is based on the linear proportionality between the density of the saturated gas of the material and the absorbance of the gas at different temperatures. The vapor pressure values determined for benzoic acid and ferrocene are in good agreement with those reported in the literature with ?2-7?% uncertainty. Thermodynamic parameters of benzoic acid, ferrocene, and naphthalene are determined in situ at temperatures below their melting points. The sublimation enthalpies of the investigated organic molecules are in excellent agreement with the ICTAC recommended values (less than 1?% difference). This method has been used to measure vapor pressures and thermodynamic parameters of organic volatile materials with vapor pressures of ?0.5-355 Pa in the 50-100?°C temperature range. PMID:23606455

Hikal, Walid M; Weeks, Brandon L

2013-04-19

135

Waste retrieval sluicing system vapor sampling and analysis plan for evaluation of organic emissions, process test phase III  

Microsoft Academic Search

This sampling and analysis plan identifies characterization objectives pertaining to sample collection, laboratory analytical evaluation, and reporting requirements for vapor samples obtained to address vapor issues related to the sluicing of tank 241-C-106. Sampling will be performed in accordance with Waste Retrieval Sluicing System Emissions Collection Phase III (Jones 1999) and Process Test Plan Phase III, Waste Retrieval Sluicing System

1999-01-01

136

Determination of nicotine and other minor alkaloids in international cigarettes by solid-phase microextraction and gas chromatography/mass spectrometry.  

PubMed

Nicotine, nornicotine, anabasine, and anatabine are the most abundant alkaloids in tobacco. Along with the addictiveness of nicotine, other properties, including their occurrence in tobacco at relatively high concentrations, and as the primary precursors for the highly carcinogenic tobacco-specific nitrosoamines, make these chemicals important from a public health standpoint Therefore, developing a fast and accurate quantitative method to screen large numbers of cigarette samples for these alkaloids was important. This report describes the first use of headspace analysis using solid-phase microextraction combined with gas chromatography/mass spectrometry for the unambiguous detection of tobacco alkaloids. Detection and confirmation of each analyte isestablished by both chromatographic retention times and the ratio of reconstructed ion chromatogram peak areas from characteristic quantitation ion and confirmation ion. Twenty-eight cigarette brands from 14 countries were analyzed. Surprisingly, the minor alkaloids' response factors varied considerably among different styles of cigarettes. Accurate quantification was achieved using a three-point standard addition protocol. The standard addition approach was essential to obtain accurate measurements by minimizing matrix effects that would otherwise have contributed to quantitation bias. Significant differences in the alkaloid profiles were measured in the different cigarette brands. These results strongly suggest that such differences reflect variations associated with blend compositions, tobacco quality, and manufacturing practices. PMID:12380807

Wu, Weijia; Ashley, David L; Watson, Clifford H

2002-10-01

137

Vapor Pressure, Speed of Sound, and PVT-Properties of R-404a in the Vapor Phase  

NASA Astrophysics Data System (ADS)

The density (300 363 K, up to 3.5 MPa) and speed of sound (293 373 K, 7.5 480 kPa) in gaseous R-404a have been studied by an isochoric piezometer method and an ultrasonic interferometer, respectively. The pressures of the saturated vapor along the dew line were measured from 298 to 330 K. The experimental uncertainties of the temperature, pressure, density, and speed-of-sound measurements were estimated to be within ±20 mK, ±1.5 kPa, ±0.15%, and ±(0.1 0.2)%, respectively. On the basis of the obtained data, the isobaric molar heat capacity of R-404a was calculated for the ideal-gas state. An eight-coefficient Benedict Webb Rubin equation of state has been developed for the gaseous phase of R-404a.

Gruzdev, V. A.; Komarov, S. G.; Stankus, S. V.

2008-04-01

138

Analysis of gas phase compounds in chemical vapor deposition of carbon from light hydrocarbons  

Microsoft Academic Search

Product distributions in the pyrolysis of ethylene, acetylene, and propylene are studied to obtain an experimental database for a detailed kinetic modeling of gas phase reactions in chemical vapor deposition of carbon from these light hydrocarbons. Experiments were performed with a vertical flow reactor at 900°C and pressures from 2 to 15kPa. Gas phase components were analyzed by both on-line

Koyo Norinaga; Olaf Deutschmann; Klaus J. Hüttinger

2006-01-01

139

Vapor-phase detection of trinitrotoluene by AIEE-active hetero-oligophenylene-based carbazole derivatives.  

PubMed

New AIEE-active hetero-oligophenylene carbazole derivatives 3 and 4 have been synthesized and serve as fluorescent probes for the selective detection of 2,4,6-trinitrotoluene (TNT) in the vapor phase, the solid phase, and aqueous media. In addition, paper strips prepared by dip-coating a solution of aggregates of derivatives 3 and 4 can provide a simple, portable, sensitive, selective, low-cost method for the detection of TNT on the picogram level. PMID:22839571

Kumar, Manoj; Vij, Varun; Bhalla, Vandana

2012-08-09

140

Menthol Cigarettes  

Center for Biologics Evaluation and Research (CBER)

Text Version... 10 Page 11. Design (Construction Variables) Design • Construction variables for both menthol and non-menthol cigarettes include: ... More results from www.fda.gov/downloads/advisorycommittees/committeesmeetingmaterials

141

Vapor-liquid phase transition and multifragmentation of nuclei  

Microsoft Academic Search

Nucleation theory based on the steady-state solution of Fokker-Plank kinetic equation is applied to study of the liquid-gas phase transition in nuclear matter. Theoretical predictions are compared with the parameters extracted from the analysis of the charge distributions of fragments in heavy ion collisions at intermediate energies. The phenomenological droplet model is shown to be able to explain both the

Eugene E. Zabrodin

1995-01-01

142

Vapor-liquid phase transition and multifragmentation of nuclei  

SciTech Connect

Nucleation theory based on the steady-state solution of Fokker-Plank kinetic equation is applied to study of the liquid-gas phase transition in nuclear matter. Theoretical predictions are compared with the parameters extracted from the analysis of the charge distributions of fragments in heavy ion collisions at intermediate energies. The phenomenological droplet model is shown to be able to explain both the characteristic power-law falloff and the long tail of the yields of light and heavy nuclear fragments correspondingly. It is shown that the traditional equilibrium approach to the analysis of the multifragmentation data leads to significant overestimation of the parameters of nuclear equation of state.

Zabrodin, E.E. [Department of Physics, University of Bergen, Allegaten 55, N-5007 Bergen (Norway)]|[Institute for Nuclear Physics, Moscow State University, 119899 Moscow (Russian Federation)

1995-11-01

143

Trace element partitioning between vapor, brine and halite under extreme phase separation conditions  

NASA Astrophysics Data System (ADS)

Experiments were conducted to investigate the partitioning of Li, Br, Rb, Cs and B between vapor, brine and halite during subcritical and supercritical phase separation in the NaCl-H 2O system (388-550 °C, 250-350 bars). Results indicate that Li and Br partition preferentially into the low-salinity vapor fluids, while Rb and Cs become more enriched in the coexisting brines. Under more extreme conditions of pressure and temperature in the two-phase region, especially near the vapor-brine-halite boundary, strong salting-out effects imposed on neutral aqueous species enhance significantly partitioning of all trace elements into the low-salinity fluid. Dissolved boron is strongly affected by this and a particularly strong enrichment into vapors is observed, a trend that can be effectively correlated with changes in reduced density. Exclusion of Li, Br, Rb, Cs and B from halite, when precipitated, further increases the solubility of these species in the coexisting Cl-poor fluid. In general, the lack of distortion in the partitioning behavior of trace elements between vapor, brine and/or halite with the transition from subcritical to supercritical conditions in the NaCl-H 2O system precludes the need for special reference to the critical point of seawater when interpreting phase relations in submarine hydrothermal systems. The combination of experimentally determined trace element partitioning data with constraints imposed by mineral solubility provides a means to better understand the origin and evolution of hot spring vent fluids. For example, in Brandon hydrothermal system (21°S EPR) supercritical phase separation and subseafloor mixing appear to be the main heat and mass transport mechanisms fueled by a shallow magmatic intrusion, with boron systematics ruling out major contributions from magmatic degassing processes accompanying the near-seafloor volcanism.

Foustoukos, D. I.; Seyfried, W. E.

2007-04-01

144

Novel method for preparing nickel/YSZ cermet by a vapor-phase process  

SciTech Connect

A novel method for preparing a nickel/YSZ (yttria-stabilized zirconia) cermet has been developed. In the present work, YSZ was deposited onto a substrate containing NiO as an oxygen source by allowing it to undergo a phase reaction in a vapor mixture of ZrCl{sub 4} and YCI{sub 3}. In the initial stage of the reaction, a porous YSZ layer was deposited onto an NiO pellet by chemical vapor deposition (CVD). The porous layer became finer and more gas-tight as the CVD reactions proceeded, and the process then changed from CVD to electrochemical vapor deposition (EVD), resulting in the growth of a dense YSZ layer on the NiO pellet.

Ogumi, Zempachi; Ioroi, Tsutomu; Uchimoto, Yoshiharu; Takehara, Zenichiro [Kyoto Univ. (Japan)

1995-03-01

145

Novel Process for Removal and Recovery of Vapor Phase Mercury  

SciTech Connect

We demonstrated in the Phase I program all key attributes of a new technology for removing mercury from flue gases, namely, a) removal of greater than 95% of both elemental and oxidized forms of mercury, both in the laboratory and in the field b) regenerability of the sorbent c) ability to scale up, and d) favorable economics. The Phase I program consisted of four tasks other than project reporting: Task I-1 ? Screen Sorbent Configurations in the Laboratory Task I-2 ? Design and Fabricate Bench-Scale Equipment Task I-3 ? Test Bench-Scale Equipment on Pilot Combustor Task I-4 ? Evaluate Economics Based on Bench-Scale Results In Task I-1, we demonstrated that the sorbents are thermally durable and are regenerable through at least 55 cycles of mercury uptake and desorption. We also demonstrated two low-pressure- drop configurations of the sorbent, namely, a particulate form and a monolithic form. We showed that the particulate form of the sorbent would take up 100% of the mercury so long as the residence time in a bed of the sorbent exceeded 0.1 seconds. In principle, the particulate form of the sorbent could be imbedded in the back side of a higher temperature bag filter in a full-scale application. With typical bag face velocities of four feet per minute, the thickness of the particulate layer would need to be about 2000 microns to accomplish the uptake of the mercury. For heat transfer efficiency, however, we believed the monolithic form of the sorbent would be the more practical in a full scale application. Therefore, we purchased commercially-available metallic monoliths and applied the sorbent to the inside of the flow channels of the monoliths. At face velocities we tested (up to 1.5 ft/sec), these monoliths had less than 0.05 inches of water pressure drop. We tested the monolithic form of the sorbent through 21 cycles of mercury sorption and desorption in the laboratory and included a test of simultaneous uptake of both mercury and mercuric chloride. Overall, in Task I-1, we found that the particulate and monolith forms of the sorbent were thermally stable and durable and would repeatedly sorb and desorb 100% of the mercury, including mercuric chloride, with low pressure drop and short residence times at realistic flue gas conditions.

Collin Greenwell; Daryl L. Roberts; Jason Albiston; Robin Stewart; Tom Broderick

1998-03-09

146

Higher cigarette prices influence cigarette purchase patterns  

Microsoft Academic Search

Objective: To examine cigarette purchasing patterns of current smokers and to determine the effects of cigarette price on use of cheaper sources, discount\\/generic cigarettes, and coupons.Background: Higher cigarette prices result in decreased cigarette consumption, but price sensitive smokers may seek lower priced or tax-free cigarette sources, especially if they are readily available. This price avoidance behaviour costs states excise tax

A Hyland; J E Bauer; Q Li; S M Abrams; C Higbee; L Peppone; K M Cummings

2005-01-01

147

Raman spectroscopic study of the vapor phase of 1-methylimidazolium ethanoate, a protic ionic liquid.  

PubMed

The gas phase over the ionic liquid 1-methylimidazolium ethanoate, [Hmim][O(2)CCH(3)], was studied by means of Raman spectroscopy. Raman spectra are presented, the species in the gas phase are identified, and their bands are assigned. The results are interpreted using ab initio quantum mechanical calculations that also predict vibrational spectra. The obtained data reinforce a previous interpretation, based on FT-ICR mass spectrometric data, that the vapor phase over [Hmim][O(2)CCH(3)] consists predominantly of two neutral molecules, monomeric ethanoic acid and 1-methylimidazole. PMID:20857986

Berg, Rolf W; Canongia Lopes, José N; Ferreira, Rui; Rebelo, Luís Paulo N; Seddon, Kenneth R; Tomaszowska, Alina A

2010-10-14

148

VUV photoionization of gas phase adenine and cytosine: a comparison between oven and aerosol vaporization.  

PubMed

We studied the single photon ionization of gas phase adenine and cytosine by means of vacuum ultraviolet synchrotron radiation coupled to a velocity map imaging electron?ion coincidence spectrometer. Both in-vacuum temperature-controlled oven and aerosol thermodesorption were successfully applied to promote the intact neutral biological species into the gas phase. The photoion yields are consistent with previous measurements. In addition, we deduced the threshold photoelectron spectra and the slow photoelectron spectra for both species, where the close to zero kinetic energy photoelectrons and the corresponding photoions are measured in coincidence. The photoionization close and above the ionization energies are found to occur mainly via direct processes. Both vaporization techniques lead to similar electronic spectra for the two molecules, which consist of broadbands due to the complex electronic structure of the cationic species and to the possible contribution of several neutral tautomers for cytosine prior to ionization. Accurate ionization energies are measured for adenine and cytosine at, respectively, 8.267 ± 0.005 eV and 8.66 ± 0.01 eV, and we deduce precise thermochemical data for the adenine radical cation. Finally, we performed an evaluation and a comparison of the two vaporization techniques addressing the following criteria: measurement precision, thermal fragmentation, sensitivity, and sample consumption. The aerosol thermodesorption technique appears as a promising alternative to vaporize large thermolabile biological compounds, where extended thermal decomposition or low sensitivity could be encountered when using a simple oven vaporization technique. PMID:23485287

Touboul, D; Gaie-Levrel, F; Garcia, G A; Nahon, L; Poisson, L; Schwell, M; Hochlaf, M

2013-03-01

149

Vapor-phase proton-exchange in lithium tantalate for high-quality waveguides fabrication  

NASA Astrophysics Data System (ADS)

Vapor-phase proton-exchange has been applied to lithium tantalate for the first time, as a waveguide fabrication technique. This technique provides alpha-phase waveguides without the need for annealing. A sealed ampoule set-up has been used employing pure benzoic acid as the vapor source. Various waveguides have been realized and optically characterized by means of standard m-lines spectroscopy. The profile shape is a step plus an exponential tail toward the substrate, as that found for vapor-phase proton-exchange waveguides in lithium niobate. The total depth of the refractive index profile increases with the exchange time, following a linear diffusion model. The ordinary index change has been determined by an interferometric method, giving values that confirmed the alpha-crystallographic phase of the fabricated waveguides. The propagation losses have been measured with a new method using an isosceles coupling prism and an out-coupling objective. The values found for the different modes of the various waveguides ranged from 0.5 to 0.8 dB/cm. An aging phenomenon in the fabricate waveguides has been observed during the first month after the exchange process. The extraordinary index change decreased of 5 percent, while the optical depth increased of 2 percent. Application of this technology to periodically poled substrates for QPM devices seems feasible.

Ramponi, Roberta; Osellame, Roberto; Marangoni, Marco; Russo, Vera

2001-05-01

150

Axially phase-matched parametric four- and six-wave mixing in potassium vapor  

NASA Astrophysics Data System (ADS)

Systematic experimental observations of axially phase-matched parametric four- and sixwave mixing processes have been made in potassium vapor pumped on or near the 4 S 6 S two-photon resonance. An IR up-conversion with a beta barium borate crystal was used for the detection of IR emissions. All the predicted processes have been observed. It is found that the excitation spectra of the emissions for those processes observed in this work are quite different from the excitation spectra of similar processes in sodium vapor. A dye-dependence of some emissions generated by the axially phase-matched parametric six-wave mixing processes has been found by using different dyes in the dye laser. The reason for the dye-dependence is discussed.

Lu, Mao-Hong; Liu, Yu-Mei

1992-04-01

151

Melting, ablation, and vapor phase condensation during atmospheric passage of the Bjurbole meteorite  

NASA Astrophysics Data System (ADS)

A detailed study of the Bjurbole fusion crust using scanning electron microscopy (SEM) and energy dispersive analysis (EDS) shows that filamentary crystals and ablation spheres may form on the meteoroid surface. Filamentary crystals, hollow spheres, and porous regions of the surface point to a period of intense vapor phase activity during atmospheric passage. Filamentary crystals can be divided into three categories on the basis of bulk composition and morphology. Two types of filamentary crystals are vapor phase condensation products formed during atmospheric entry of the meteoroid. The other type forms by the interaction of seawater with the fusion surface. The density and composition of ablation spheres varies with the flight orientation of the meteorite. The size range and composition of iron-nickel spheres on the surface of Bjurbole are similar to spheres collected in the stratosphere. A comparison of stratospheric dust collections with meteorite surfaces may provide further insight into the mechanisms of meteoroid entry into planetary atmospheres.

Rietmeijer, F. J. M.; MacKinnon, I. D. R.

1984-02-01

152

Models of p- T diagrams for a ternary system with invariant equilibrium of three solid phases, liquid, and vapor  

NASA Astrophysics Data System (ADS)

A version of a model of the p- T diagram for a ternary system in which three solid phases, liquid, and vapor are in invariant five-phase equilibrium is developed. The phase equilibria and phase transitions in the isobaric T- x- y diagram are analyzed, and isothermal and polythermal sections are presented.

Khaldoyanidi, K. A.

2013-03-01

153

Vapor phase near infrared spectroscopy of the hydrogen bonded methanol-trimethylamine complex.  

PubMed

The spectroscopy of the vapor phase hydrogen bonded complex formed between methanol and trimethylamine has been studied in the near-infrared region. A combination band involving one quantum of OH stretch and one quantum of COH bend has been observed for the complex. The much less intense first OH-stretching overtone transition has been tentatively assigned. This assignment is supported by anharmonic oscillator local mode calculations. PMID:16884192

Howard, Daryl L; Kjaergaard, Henrik G

2006-08-10

154

Lateral epitaxial overgrowth of (0001) AlN on patterned sapphire using hydride vapor phase epitaxy  

Microsoft Academic Search

Coalesced, crack-free (0001) AlN films were grown on stripe patterned sapphire substrates without AlN seed layers using hydride vapor phase epitaxy. Using templates with stripes oriented in the sapphire direction, lateral epitaxial overgrowth AlN films were coalesced over trench regions as wide as 10 mum despite parasitic sidewall and trench growth. Using transmission electron microscopy, a reduction in the dislocation

Scott A. Newman; Derrick S. Kamber; Troy J. Baker; Yuan Wu; Feng Wu; Zhen Chen; Shuji Namakura; James S. Speck; Steven P. Denbaars

2009-01-01

155

The Catalysis of Vapor-Phase Beckmann Rearrangement for the Production of ?-Caprolactam  

Microsoft Academic Search

Recently, Sumitomo Chemical Co., Ltd. developed the vapor-phase Beckmann rearrangement process for the production of e-caprolactam. In the process, cyclohexanone oxime is rearranged into e-caprolactam using a zeolite as a catalyst instead of sulfuric acid. EniChem in Italy developed the ammoximation process that involves the direct production of cyclohexanone oxime without producing any ammonium sulfate. Sumitomo Chemical Co., Ltd. has

Hiroshi Ichihashi; Masaya Ishida; Akinobu Shiga; Masaru Kitamura; Tatsuya Suzuki; Katsuhiro Suenobu; Keisuke Sugita

2003-01-01

156

The contribution of nitro- and methylnitronaphthalenes to the vapor-phase mutagenicity of ambient air samples  

Microsoft Academic Search

1- and 2-Nitronaphthalene (NN) and the 14 methylnitronaphthalene (MNN) isomers were identified and quantified in ambient vapor-phase samples collected in Redlands, CA during moderate photochemical air pollution. The mutagenic activities of NN and MNN standards were determined using a microsuspension-preincubation modification of the Ames Salmonella bacterial reversion assay in strain TA98 without microsomal activation. The calculated contributions of the NNs

Pamela Gupta; William P. Harger; Janet Arey

1996-01-01

157

Sulfated TiO 2 Decontaminate 2-CEES and DMMP in Vapor Phase  

Microsoft Academic Search

An acid photocatalyst TiO2, modified with H2SO4, is prepared and used to decontaminate Chemical Warfare Agents (CWAs) simulants 2-CEES (2-chloroethyl ethyl sulfide) and\\u000a DMMP (dimethyl methylphosphonate) in vapor phase. Compared with the unmodified pure TiO2 photocatalyst, the adsorption capacity on the sulfated photocatalyst increases by 50%, and the conversion for 2-CEES increases\\u000a more than 20%. It is found that the

ShiTong Han; GuoYing Zhang; HaiLing Xi; DaNian Xu; XianZhi Fu; XuXu Wang

2008-01-01

158

The far-infrared vapor phase spectra of some halosubstituted anilines  

Microsoft Academic Search

Vapor phase far-infrared spectra from 35 to 675 cm?1 of the nine ortho-, meta-, and para-substituted fluoro-, chloro-, and bromoanilines obtained with an interferometer are reported. The vi=1, 2, and 3 levels of the amino group inversion vibration are established from the observed transitions, and the barriers to inversion are derived from these, using a simple double minimum harmonic well

R. A. Kydd; P. J. Krueger

1978-01-01

159

Evidence of critical scaling behavior during vapor phase synthesis of continuous filament composites  

SciTech Connect

The authors present experimental measurements of the accessible pore fraction in ceramic matrix composites during consolidation by vapor phase infiltration. For two topologically distinct filament architectures, the accessible pore fraction decreased during consolidation with a power law decay and a critical scaling exponent of 0.41 (R{sup 2} = 0.97). A three-dimensional analysis of the percolating pores revealed that the structures became topologically equivalent and simply connected near the critical density.

Kinney, J. H., LLNL

1997-02-01

160

Lamp-heated rapid vapor-phase doping technology for 100GHz Si bipolar transistors  

Microsoft Academic Search

High-speed Si bipolar transistor technology that uses lamp-heated Rapid Vapor-phase Doping (RVD) for shallow base formation is demonstrated. By applying RVD to a self-aligned metal\\/IDP (SMI) base electrode structure, excellent characteristics, 82-GHz fT and 92-GHz fmax, were obtained simultaneously. Devices with longer emitters attained 100 GHz fT and fmax

Yukihiro Kiyota; Eiji Ohue; Takahiro Onai; Katsuyoshi Washio; Masamichi Tanabe; Taroh Inada

1996-01-01

161

Product yields and kinetics from the vapor phase cracking of wood pyrolysis tars  

Microsoft Academic Search

The homogeneous vapor phase cracking of newly formed wood pyrolysis tar was studied at low molar concentrations as a function of temperature (773 - 1.073 K), at residence times of 0.9 - 2.2 s. Tar conversions ranged from about 5 to 88%. The tars were generated by low heating rate (0.2 K\\/s) pyrolysis of --2 cm deep beds of sweet

Michael L. Boroson; Jack B. Howard; W. A. Peters

1989-01-01

162

Vapor-phase isomerization of endo-tetrahydrodicyclopentadiene to its exo isomer over zeolite catalysts  

Microsoft Academic Search

Vapor-phase isomerization of endo-tetrahydrodicyclopentadiene (endo-THDCPD) to exo-THDCPD over zeolite catalysts (HY, H-USY, H?, HZSM-5 and HMOR) was studied as a green synthesis route for exo-THDCPD. The HY and H-USY catalysts showed catalytic activity while the H?, HZSM-5 and HMOR catalysts did not. Higher yield of exo-THDCPD was obtained over the H-USY catalyst than that over the HY catalyst, attributing to

Cong-ming Sun; Gang Li

2011-01-01

163

Vapor-phase hydrothermal growth of novel segmentally configured nanotubular crystal structure.  

PubMed

A new form of nanotubular crystal structure is directly grown by a vapor-phase hydrothermal method via an epitaxial orientated crystal growth mechanism. The as-prepared nanotubes possess a unique multi-tunnel core-shell layered nanotubular structure with droplet shaped polygonal periphery and segmental crystal configuration. They are dimension-tunable and demonstrate superior ion exchange properties in terms of exchange rate and ion accommodating capacity. PMID:23589320

Liu, Porun; Zhang, Haimin; Liu, Hongwei; Wang, Yun; An, Taicheng; Cai, Weiping; Yang, Huagui; Yao, Xiangdong; Zhu, Guangshan; Webb, Robyn; Zhao, Huijun

2013-04-16

164

Nitrogen Doped p-Type ZnSe Layer Grown by Metalorganic Vapor Phase Epitaxy  

Microsoft Academic Search

Nitrogen-doped ZnSe layers have been grown on (100) GaAs substrates by metalorganic vapor phase epitaxy using NH3 as the doping material. The N-doped layers exhibit a strong free-to-acceptor transition emission at 77 K and a strong acceptor bound-exciton emission line at 15 K. The layers with a high doping level, which exhibit broader excitonic emission lines, indicate p-type conduction with

Akira Ohki; Noriyoshi Shibata; Sakae Zembutsu

1988-01-01

165

Isothermal vapor phase epitaxy as a versatile technology for infrared photodetectors  

Microsoft Academic Search

We report here the use of isothermal vapor phase epitaxy to grow 3D Hg1-xCdxTe heterostructures for photoconductive, photovoltaic and photoelectromagnetic infrared detectors operated at near room temperatures. A reusable two-zone atmospheric pressure growth system has been developed.the system makes it possible not only to grow epilayers but also to perform in situ other processes such as high temperature annealing to

Krzysztof Adamiec; Miroslaw Grudzien; Zenon Nowak; Jaroslaw Pawluczyk; Jozef Piotrowski; Jaroslaw Antoszewski; John M. dell; Charles A. Musca; Lorenzo Faraone

1997-01-01

166

Vapor-Phase Diffusion Flames in the Combustion of Magnesium, Calcium and Strontium  

Microsoft Academic Search

This paper describes an experimental investigation of the flame structure of metal vapor-phase diffusion flames, in particular the low-pressure flames of Mg, Ca, and Sr. Two types of experiments were employed. In the first type, metal wire samples were mounted between electrodes and heated electrically. In the second type, a two-dimensional diffusion flame burner was adapted to low-pressure metal combustion

H. F. SULLIVAN; I. GLASSMAN

1971-01-01

167

Infrared spectroscopic studies of the conformation in ethyl ?-haloacetates in the vapor, liquid and solid phases  

Microsoft Academic Search

Infrared spectra of ethyl ?-fluoroacetate, ethyl ?-chloroacetate, ethyl ?-bromoacetate and ethyl ?-iodoacetate have been measured in the solid, liquid and vapor phases in the region 4000–200cm?1. Vibrational frequency assignment of the observed bands to the appropriate modes of vibration was made. Calculations at DFT B3LYP\\/6-311+G** level, Job: conformer distribution, using Spartan program ‘08, release 132 was made to determine which

Naserallah A. Jassem; Muhsin F. El-Bermani

2010-01-01

168

Gallium arsenide and indium arsenide surfaces produced by metalorganic vapor-phase epitaxy  

Microsoft Academic Search

Thin films of GaAs and InAs were deposited on GaAs(001) substrates by metalorganic vapor-phase epitaxy (MOVPE), and their surfaces were characterized by scanning tunneling microscopy (STM), X-ray photoelectron spectroscopy (XPS), and low-energy electron diffraction (LEED). Gallium arsenide surfaces produced in the MOVPE reactor at 570°C and a V\\/III ratio of 50 exhibit a (1×2) reconstruction, and are covered with weakly

L. Li; B.-K. Han; D. Law; M. Begarney; R. F. Hicks

1998-01-01

169

Selective area metalorganic vapor-phase epitaxy of gallium arsenide on silicon  

Microsoft Academic Search

The selective area, metalorganic vapor-phase epitaxy of gallium arsenide on silicon substrates was investigated. Low-temperature arsenic passivation of the silicon surface was realized at 650°C. A two-step growth method was used to deposit the GaAs films with an optimum nucleation temperature of 400°C. Layers nucleated at 350°C or below were found to be polycrystalline whereas those nucleated at 400°C and

S. F. Cheng; L. Gao; R. L. Woo; A. Pangan; G. Malouf; M. S. Goorsky; K. L. Wang; R. F. Hicks

2008-01-01

170

Influence of vapor phase pre-oxide-cleaning on the oxidation characteristics  

Microsoft Academic Search

In this paper the oxide growth with and without annealing in nitric oxide (NO) is investigated for different types of pre-oxidation cleaning.Two types of vapor phase cleaning (VPC), so called VPC1 and VPC2, are investigated and compared to standard wet cleaning. The VPC1 cleaning uses anhydrous HF (AHF)\\/methanol for the removal of the native oxide. The VPC2 cleaning is similar

B Froeschle; N Sacher; F Glowacki; T Theiler

1998-01-01

171

Vapor phase catalytic degradation of bis(2-chloroethyl) ether on supported vanadia–titania catalyst  

Microsoft Academic Search

Series of V2O5–TiO2 catalysts with varying vanadium content are prepared by impregnation method. The catalyst composition is determined by XRD and Smart mapping (SEM–EDAX), respectively. The bulk reducibility of the catalyst is determined by the temperature programmed reduction (TPR). Catalyst activity and stability are elucidated in vapor phase catalytic degradation of bis(2-chloroethyl) ether (CEE). The factors affecting the process parameters

S. Chandra Shekar; Keshav Soni; Rajendra Bunkar; Manoj Sharma; Beer Singh; M. V. S. Suryanarayana; R. Vijayaraghavan

2011-01-01

172

Preparation of symmetric network PVDF membranes for protein adsorption via vapor induced phase separation  

Microsoft Academic Search

Symmetric network poly(vinylidene fluoride) (PVDF) membranes without a dense skin layer were prepared by vapor induced phase separation from a PVDF\\/ N,N-dimethyl acetamide (DMAc)\\/ water system. The effects of evaporation atmosphere, temperature and humidity during the preparation of the membranes on their morphologies were investigated by SEM. With low temperature and high humidity, the polymer crystallization mechanism dominated the membrane

Qian Ye; Lihua Cheng; Lin Zhang; Li Xing; Huanlin Chen

2011-01-01

173

Preparation of Symmetric Network PVDF Membranes for Protein Adsorption via Vapor-Induced Phase Separation  

Microsoft Academic Search

Symmetric network poly(vinylidene fluoride) (PVDF) membranes without a dense skin layer were prepared by vapor-induced phase separation from a PVDF\\/N,N-dimethylacetamide (DMAc)\\/water system. The effects of evaporation atmosphere, temperature, and humidity during the preparation of the membranes on their morphologies were investigated by scanning electron microscope (SEM). With low temperature and high humidity, the polymer crystallization mechanism dominated the membrane formation

Qian Ye; Lihua Cheng; Lin Zhang; Li Xing; Huanlin Chen

2011-01-01

174

Evolution of deep centers in GaN grown by hydride vapor phase epitaxy  

SciTech Connect

Deep centers and dislocation densities in undoped n GaN, grown by hydride vapor phase epitaxy (HVPE), were characterized as a function of the layer thickness by deep level transient spectroscopy and transmission electron microscopy, respectively. As the layer thickness decreases, the variety and concentration of deep centers increase, in conjunction with the increase of dislocation density. Based on comparison with electron-irradiation induced centers, some dominant centers in HVPE GaN are identified as possible point defects.

Fang, Z.-Q.; Look, D. C.; Jasinski, J.; Benamara, M.; Liliental-Weber, Z.; Molnar, R. J.

2001-01-15

175

Vapor phase acoustic measurements for R125 and development of a Helmholtz free energy equation  

Microsoft Academic Search

This paper presents speed of sound measurements on pentafluoroethane (R125) in the vapor phase. The measurements were performed in a stainless steel spherical resonator of ?900cm3 at temperatures in the range 260–360K and pressures up to 500kPa. Acoustic virial coefficients and ideal gas heat capacities are deduced directly from the data. The whole set of speed of sound measurements and

M. Grigiante; G. Scalabrin; G. Benedetto; R. M. Gavioso; R. Spagnolo

2000-01-01

176

Chirality-dependent vapor-phase epitaxial growth and termination of single-wall carbon nanotubes.  

PubMed

Structurally uniform and chirality-pure single-wall carbon nanotubes are highly desired for both fundamental study and many of their technological applications, such as electronics, optoelectronics, and biomedical imaging. Considerable efforts have been invested in the synthesis of nanotubes with defined chiralities by tuning the growth recipes but the approach has only limited success. Recently, we have shown that chirality-pure short nanotubes can be used as seeds for vapor-phase epitaxial cloning growth, opening up a new route toward chirality-controlled carbon nanotube synthesis. Nevertheless, the yield of vapor-phase epitaxial growth is rather limited at the present stage, due in large part to the lack of mechanistic understanding of the process. Here we report chirality-dependent growth kinetics and termination mechanism for the vapor-phase epitaxial growth of seven single-chirality nanotubes of (9, 1), (6, 5), (8, 3), (7, 6), (10, 2), (6, 6), and (7, 7), covering near zigzag, medium chiral angle, and near armchair semiconductors, as well as armchair metallic nanotubes. Our results reveal that the growth rates of nanotubes increase with their chiral angles while the active lifetimes of the growth hold opposite trend. Consequently, the chirality distribution of a nanotube ensemble is jointly determined by both growth rates and lifetimes. These results correlate nanotube structures and properties with their growth behaviors and deepen our understanding of chirality-controlled growth of nanotubes. PMID:23937554

Liu, Bilu; Liu, Jia; Tu, Xiaomin; Zhang, Jialu; Zheng, Ming; Zhou, Chongwu

2013-08-23

177

Shared retronasal identifications of vapor-phase 18-carbon fatty acids.  

PubMed

The long-chain 18-carbon fatty acids linoleic, oleic, and stearic acids, retronasally in vapor phase, are discriminated from blanks and each other. However, ability to linguistically identify them was unknown. To explore this, a Focus Group and then Check-All-That-Apply measures gave 9 identifiers for the 3 fatty acids plus phenylethyl alcohol (PEA) and geraniol. Next, participants selected 1 of the 9 identifiers from a computer-based display. It was found that the modal identification for linoleic acid was 23% "Rubbery" (next 18% "Oily" and "New Plastic"), oleic acid was 21% Oily (next 19% Rubbery), and stearic acid was 43% Rubbery (next 22% New Plastic), but linoleic acid received ~40% food-related identifiers. Geraniol was 96% "Lemon," and PEA was 67% "Flowers." Identifications for fatty acids differed significantly (P ? 0.05) from those for geraniol for most participants (86%) and from those for PEA for 59% of participants. Stearic acid identifications differed significantly from those for linoleic and oleic acids for 32% of participants. However, identification for linoleic acid differed significantly from those for oleic acid for only 14% of participants. Overall, retronasal vapor-phase stearic acid was identified differently from other 18-carbon fatty acids by a substantial minority of participants, but linoleic and oleic acids were not, suggesting that these 2 vapor-phase 18-carbon fatty acids can be identified retronasally as a group but not separately. PMID:23424022

Chukir, Tariq; Darlington, Richard B; Halpern, Bruce P

2013-02-19

178

Metastable phase formation in thin films formed by laser breakdown chemical vapor deposition  

NASA Astrophysics Data System (ADS)

Thin films produced by laser breakdown chemical vapor deposition (LBCVD) from Ni and Fe carbonyls were examined and their structure characterized, with emphasis on identifying the phases present. A brightfield micrograph observed in the Ni samples and the corresponding selected area diffraction (SAD) pattern are shown along with two darkfield micrographs of Ni-C film obtained from two positions on the same diffraction ring. It is seen that the decomposition of both carbonyls results in the formation of a supersaturated fcc phase and the carbide phase. The study shows that even a severe quench from the gas phase fails to completely stop the system from approaching its equilibrium structure. This indicates that the carbides Ni3C and Fe3C are associated with a very high thermodynamic driving force for their formation even though both of these phases are metastable.

Menon, S. K.; Jervis, T. R.

1986-11-01

179

Sorption equilibria of vapor-phase organic pollutants on unsaturated soils and soil minerals. Final report, Mar 85-Mar 89  

SciTech Connect

Most groundwater pollutants are volatile organic compounds; however, there is relatively little understanding of the sorption reactions that control the transport and fate of organic vapors in the vadose zone. This investigation identified the physical/chemical properties of the soil matrix and organic vapors which control vapor-solid phase distribution. The dominant property which regulates vapor sorption in the unsaturated zone is the moisture content of the soil. Under very dry conditions, soil mineral/vapor interactions are regulated by specific surface area, indicating the dominance of a relatively non-specific physical adsorption process. However, at moisture contents exceeding an average surface coverage of four to eight layers of water, vapor uptake is controlled by partitioning reactions into soil moisture and soil organic matter.

Lion, L.W.; Ong, S.K.; Linder, S.R.; Swager, J.L.; Schwager, S.J.

1990-04-01

180

Biodegradation of high concentrations of benzene vapors in a two phase partition stirred tank bioreactor  

PubMed Central

The present study examined the biodegradation rate of benzene vapors in a two phase stirred tank bioreactor by a bacterial consortium obtained from wastewater of an oil industry refinery house. Initially, the ability of the microbial consortium for degrading benzene was evaluated before running the bioreactor. The gaseous samples from inlet and outlet of bioreactor were directly injected into a gas chromatograph to determine benzene concentrations. Carbone oxide concentration at the inlet and outlet of bioreactor were also measured with a CO2 meter to determine the mineralization rate of benzene. Influence of the second non-aqueous phase (silicon oil) has been emphasized, so at the first stage the removal efficiency (RE) and elimination capacity (EC) of benzene vapors were evaluated without any organic phase and in the second stage, 10% of silicon oil was added to bioreactor media as an organic phase. Addition of silicon oil increased the biodegradation performance up to an inlet loading of 5580?mg/m3, a condition at which, the elimination capacity and removal efficiency were 181?g/m3/h and 95% respectively. The elimination rate of benzene increased by 38% in the presence of 10% of silicone oil. The finding of this study demonstrated that two phase partition bioreactors (TPPBs) are potentially effective tools for the treatment of gas streams contaminated with high concentrations of poorly water soluble organic contaminant, such as benzene.

2013-01-01

181

Pyrolysis-Molecular Weight Chromatography-Vapor Phase Infrared Spectrophotometry: An On-Line System for Analysis of Polymers.  

National Technical Information Service (NTIS)

An instrumental system consisting of a combination of a programmable pyrolyzer, a thermal conductivity detector, a mass chromatograph, a gas chromatograph, a fast-scan vapor-phase infrared spectrophotometer, and a computer is discussed and reviewed with e...

E. Kiran J. K. Gillham

1979-01-01

182

Vapor-Phase Free Radical Polymerization in the Presence of Ionic Liquids  

NASA Astrophysics Data System (ADS)

Ionic liquids (ILs) have recently attracted significant interest as an environmentally-friendly alternative to traditional volatile organic solvents because ILs are non-volatile, non-flammable, and can be easily recycled. ILs can be exploited in many ways to improve the selectivity and kinetics of chemical reactions, including polymer synthesis. Ionic liquids have negligible vapor pressure and are therefore stable under vacuum. A few studies have investigated ILs as substrates in inorganic vacuum deposition processes, but to our knowledge ILs have not been used in vapor phase polymerization systems. We have recently introduced ionic liquids into the initiated chemical vapor deposition (iCVD) process for the first time. The iCVD polymerization process occurs via a free-radical mechanism, and the deposited polymeric films are compositionally analogous to solution-phase polymers. Despite the wide range of polymers that have been synthesized using iCVD, it has proven difficult to polymerize monomers with low surface concentrations such as styrene and low propagation rates such as methyl methacrylate and it is difficult to produce block copolymers. In this talk, we will show that our novel ILiCVD system can address some of these shortcomings. We will explain the effects of deposition time, temperature, and monomer solubility on the morphology of the polymer and the molecular weight of the polymer chains.

Gupta, Malancha

2011-03-01

183

Enhanced Vapor-Phase Diffusion in Porous Media - LDRD Final Report  

SciTech Connect

As part of the Laboratory-Directed Research and Development (LDRD) Program at Sandia National Laboratories, an investigation into the existence of enhanced vapor-phase diffusion (EVD) in porous media has been conducted. A thorough literature review was initially performed across multiple disciplines (soil science and engineering), and based on this review, the existence of EVD was found to be questionable. As a result, modeling and experiments were initiated to investigate the existence of EVD. In this LDRD, the first mechanistic model of EVD was developed which demonstrated the mechanisms responsible for EVD. The first direct measurements of EVD have also been conducted at multiple scales. Measurements have been made at the pore scale, in a two- dimensional network as represented by a fracture aperture, and in a porous medium. Significant enhancement of vapor-phase transport relative to Fickian diffusion was measured in all cases. The modeling and experimental results provide additional mechanisms for EVD beyond those presented by the generally accepted model of Philip and deVries (1957), which required a thermal gradient for EVD to exist. Modeling and experimental results show significant enhancement under isothermal conditions. Application of EVD to vapor transport in the near-surface vadose zone show a significant variation between no enhancement, the model of Philip and deVries, and the present results. Based on this information, the model of Philip and deVries may need to be modified, and additional studies are recommended.

Ho, C.K.; Webb, S.W.

1999-01-01

184

Phase Composition and Microstructural Responses of Graded Mullite/YSZ Coatings Under Water Vapor Environments  

NASA Astrophysics Data System (ADS)

Mullite-based systems have been considered as environmental barrier coatings (EBCs) for high temperature protection of Si-based ceramic (Si3N4, SiC) substrates against water vapor corrosion, for application in forthcoming turbine engines. Graded mullite/Y-ZrO2 composites plasma sprayed over Hexoloy SiC substrates were analyzed as EBCs. All feedstock materials were purposely prepared and singular spraying conditions were used to assure superior crystallization. The different coated specimens were subjected to temperatures of 1300 °C for 100-500 h under water vapor environment. The effect of water corrosion on the exposed coatings was investigated by focusing on their phase and microstructure changes.

Garcia, E.; Mesquita-Guimarães, J.; Miranzo, P.; Osendi, M. I.; Cojocaru, C. V.; Wang, Y.; Moreau, C.; Lima, R. S.

2011-01-01

185

Nonphosphor White Light Emitting Diodes by Mixed-Source Hydride Vapor Phase Epitaxy  

NASA Astrophysics Data System (ADS)

In this paper, we approached a novel fabrication for non phosphor white light emitting diodes (LEDs) by the growth of AlGaN/InAlGaN double-hetero structures using by mixed-source hydride vapor phase epitaxy (HVPE) system with multi-sliding boat. It is unique crystal growth technology different from conventional HVPE and metal organic chemical vapor deposition (MOCVD) system using mixed metal source of aluminum, indium and gallium. The characterization of non phosphor white LEDs was examined by photoluminescence (PL) and electroluminescence (EL). The results of EL were found green and yellow emissions as spectrum peaks near 500, 550, and 610 nm definitely. The CIE chromaticity coordinates of white LEDs was measured at injection current 30 mA. Our results are nearly positions; at x = 0.28 and y = 0.31. Even though the LED needs more improved in optical properties, we demonstrated achieving phosphor-free solid-state white lighting.

Lee, Gang Seok; Jeon, Hunsoo; Jung, Se-Gyo; Bae, Seon Min; Shin, Min Jung; Kim, Kyoung Hwa; Yi, Sam Nyung; Yang, Min; Ahn, Hyung Soo; Yu, Young-Moon; Kim, Suck-Whan; Ha, Hong-Ju; Sawaki, Nobuhiko

2012-01-01

186

Structural and Optical Properties of Carbon-Doped AlN Substrates Grown by Hydride Vapor Phase Epitaxy Using AlN Substrates Prepared by Physical Vapor Transport  

NASA Astrophysics Data System (ADS)

Freestanding AlN substrates with various carbon (C) concentrations were prepared from C-doped thick layers grown by hydride vapor phase epitaxy (HVPE) on bulk AlN substrates prepared by physical vapor transport (PVT). The structural properties of the AlN substrates up to a C concentration of 3× 1019 cm-3 were the same as those of the nominally undoped substrates, while the absorption coefficient ? at 265 nm was increased by C doping from 6.6 to 97 cm-1, when C concentration changed from <2× 1017 to 1× 1019 cm-3, respectively. Photoluminescence (PL) below 4.0 eV also increased by C doping.

Nagashima, Toru; Kubota, Yuki; Kinoshita, Toru; Kumagai, Yoshinao; Xie, Jinqiao; Collazo, Ramón; Murakami, Hisashi; Okamoto, Hiroshi; Koukitu, Akinori; Sitar, Zlatko

2012-12-01

187

Vapor-phase infrared spectroscopy on solid organic compounds with a pulsed resonant photoacoustic detection scheme  

NASA Astrophysics Data System (ADS)

There is a great need for a low cost and sensitive method to measure infrared spectra of solid organic compounds in the gas phase. To record such spectra, we propose an optical parametric generator-based photoacoustic spectrometer, which emits in the mid-infrared fingerprint region between 3 and 4 microns. In this system, the sample is heated in a vessel before entering a home built photoacoustic cell, where the gaseous molecules are excited by a tunable laser source with a frequency repetition rate that matches the first longitudinal resonance frequency of the photocaoustic cell. In a first phase, we have focused on low-melting point stimulants such as Nikethamide, Mephentermine sulfate, Methylephedrine, Ephedrine and Pseudoephedrine. The vapor-phase spectra of these doping substances were measured between 2800 and 3100 cm-1, where fundamental C-H stretching vibrations take place. Our spectra show notable differences with commercially available condensed phase spectra. Our scheme enables to measure very low vapor pressures of low-melting point (<160 °C) solid organic compounds. Furthermore, the optical resolution of 8 cm-1 is good enough to distinguish closely related chemical structures such as the Ephedra alkaloids Ephedrine and Methylephedrine, but doesn't allow to differentiate diastereoisomeric pairs such as Ephedrine and Pseudoephedrine, two important neurotransmitters which reveal different biological activities. Therefore, higher resolution and a system capable of measuring organic compounds with higher melting points are required.

Bartlome, Richard; Fischer, Cornelia; Sigrist, Markus W.

2005-08-01

188

Vapor-Phase Garnet at Yucca Mountain, Nevada: Geochemistry and Oxygen-Isotope Thermometry  

SciTech Connect

About 20 vapor-phase garnets were studied in two samples of the Topopah Spring Tuff from Yucca Mountain, in southern Nevada. The Miocene-age Topopah Spring Tuff is a 350-m-thick, devitrified, moderately to densely welded ash flow that is compositionally zoned from high-silica rhyolite to quartz latite. During cooling of the tuff, escaping vapor produced lithophysae (former gas cavities) lined with an assemblage of tridymite, cristobalite, alkali feldspar, and locally, hematite and/or garnet. Vapor-phase topaz and economic deposits (such as porphyry molybdenum-tungsten) commonly associated with topaz-bearing rhyolites (characteristically enriched in fluorine) were not found in the Topopah Spring Tuff at Yucca Mountain. The garnets are not primary igneous phenocrysts, but rather crystals that grew from a fluorine-poor magma-derived vapor trapped during emplacement of the tuff. The garnets are euhedral, vitreous, reddish brown, trapezohedral, as large as 2 mm in diameter, and fractured. The garnets also contain inclusions of tridymite. Electron-microprobe analyses of the garnets reveal that they are almandine-spessartine (48.0 and 47.9 mol percent, respectively), have an average chemical formula of (Fe{sub 1.46}, Mn{sub 1.45}, Mg{sub 0.03}, Ca{sub 0.10}) (Al{sub 1.93}, TiO{sub 0.02}) Si{sub 3.01}O{sub 12}, and are homogeneous in Fe and Mn concentrations from core to rim. Composited garnets from each sample site have {delta}{sup 18}O values of 7.2 and 7.4{per_thousand}. The coexisting tridymite, however, has {delta}{sup 18}O values of 17.4 and 17.6{per_thousand} values indicative of reaction with later, low-temperature water. Unaltered tridymite from higher in the stratigraphic section has a {delta}{sup 18}O of 11.1{per_thousand} which, when coupled with the garnet {delta}{sup 18}O values in a quartz-garnet fractionation equation, indicates vapor-phase crystallization at temperatures of almost 600 C. This high-temperature mineralization, formed during cooling of the tuffs, is distinct from the later and commonly recognized low-temperature stage (generally 50-70 C) of calcite, quartz, and opal secondary mineralization, formed from percolating meteoric water, that locally coats fracture footwalls and lithophysal floors.

R. J. Moscati; C.A. Johnson; J.F. Whelan

2001-07-03

189

Solid state phase transition and vapor pressure studies in ammonium nitrate-potassium nitrate binary system  

NASA Astrophysics Data System (ADS)

The solid-state phase transitions in ammonium nitrate (NH4NO 3) and potassium nitrate (KNO3) solid solutions and the equilibrium NH4NO3-KNO3 (AN-KN) phase diagram have been determined. The phase transitions and phase diagram were determined by using the differential scanning calorimetry (DSC) and high temperature X-ray diffractometry. Samples of several different compositions were made for these analyses in a special "Dry Room" with very low humidity. In the X-ray diffraction experiments, the samples were heated on Pt-Rh strip and LaB6 or Si was added for internal calibration. Equilibrium phase diagram was also calculated by using the "FactSage" computer program. A single (AN III) phase region without any phase transitions between 293 to 373 K was observed for compositions between 5 to 25wt% KNO3 in NH4NO3 that is critical for air bag gas generators. The higher temperature KNO3 (KN I) phase has a wide stability range, from 100%KNO3 to 20%KNO3 solution. There is one eutectic, two eutectoids, and two peritectoids in this phase diagram. Two newly discovered solid-state phases were found in the mid-composition range of AN-KN solid solutions. Details of phase equilibria and lattice expansions during heating have been determined. Phase diagram calculations show a reasonable match of the phase boundaries. The total vapor pressures as well as the average molecular weights of pure ammonium nitrate and 16% KNO3 solid solution were measured at various temperatures by the torsion-Knudsen effusion method. The partial pressures of NH4NO3 (PNH4NO 3), NH3 (PNH3), and HNO3 (PHNO 3) have also been determined.

Chien, Wen-Ming

190

Higher cigarette prices influence cigarette purchase patterns  

PubMed Central

Objective: To examine cigarette purchasing patterns of current smokers and to determine the effects of cigarette price on use of cheaper sources, discount/generic cigarettes, and coupons. Background: Higher cigarette prices result in decreased cigarette consumption, but price sensitive smokers may seek lower priced or tax-free cigarette sources, especially if they are readily available. This price avoidance behaviour costs states excise tax money and dampens the health impact of higher cigarette prices. Methods: Telephone survey data from 3602 US smokers who were originally in the COMMIT (community intervention trial for smoking cessation) study were analysed to assess cigarette purchase patterns, use of discount/generic cigarettes, and use of coupons. Results: 59% reported engaging in a high price avoidance strategy, including 34% who regularly purchase from a low or untaxed venue, 28% who smoke a discount/generic cigarette brand, and 18% who report using cigarette coupons more frequently that they did five years ago. The report of engaging in a price avoidance strategy was associated with living within 40 miles of a state or Indian reservation with lower cigarette excise taxes, higher average cigarette consumption, white, non-Hispanic race/ethnicity, and female sex. Conclusion: Data from this study indicate that most smokers are price sensitive and seek out measures to purchase less expensive cigarettes, which may decrease future cessation efforts.

Hyland, A; Bauer, J; Li, Q; Abrams, S; Higbee, C; Peppone, L; Cummings, K

2005-01-01

191

Pin-in-paste DFM constraints in vapor phase soldering technology for optoelectronic components  

NASA Astrophysics Data System (ADS)

The topical trends in the field of electronic equipments developing are a large integration on pcb support for different types of components and devices, including optoelectronic type, from small to medium power, in condition of reducing physical dimensions, in order to create new electronic products in short time at lower manufacturing cost. The condition for economical success for a product is to assure the product, even from the conception stage, with a high level of quality by reducing the product cost; to conclude, designing according with production possibilities by using Design For Manufacturing (DFM) concept. This desideratum depends on the conception and design of the product. According to DFM concept, a successful project assures design requirements for the system and finally for printed circuit boards (PCB), accomplishes the assembling technology constraints defined by international standards in the field of electronic packaging, such as IPC or Restriction of Hazardous Substances Directive. Active from July 1, 2006, the RoHS Directive 2002/95/EC adopted in February 2003 by the European Union, and adopted in Romania by HG - 992/2005, completed by HG - 816/2006, call forth important consequences in assembling technologies. In order to minimize manufacturing cost, Pin-In-Paste offers solutions for complete assembling of high complexity PCBs in Vapor Phase Technology using only one reflow machine avoiding overheating of the assemblies relatively to infrared reflow oven. Starting from RoHS consequences analysis, especially thermal profile, the paper presents the applied research performed in the assembling lines on VPS machine in order to define the design requirements for Pin-In-Paste dedicated stencils and PCBs, experiments result and conclusions regarding DFM requirements for lead-free assembling technologies of optoelectronic components. Finally, scientific and practical conclusions shall be drawn to configure the optimum implementation way for Pin-In-Paste in Vapor Phase Technology. The authors emphasizes that Vapor Phase Technology has all the conditions to become the disruptive technology of the moment.

Plotog, I.; Varzaru, G.; Turcu, C.; Cucu, T. C.; Svasta, P.; Vasile, A.

2009-01-01

192

Real-time trace detection of vapor-phase elemental mercury and its compounds  

NASA Astrophysics Data System (ADS)

The high toxicity of mercury species (elemental and compound) has prompted a demand for accurate, real-time inventory and control of their emissions. Our method of choice for mercury compound vapor is Photofragment Fluorescence spectroscopy. Target compound concentrations can be related to the fluorescence intensity from an excited fragment. Fragment identities and distributions, as revealed in the fluorescence spectrum provide information on the composition of the parent species. In the first experimental phase, a static cell (no flow) containing mercury compound (e.g. HgCl2 vapor was probed with a deep ultraviolet (UV) laser to generate characteristic spectra. An atmospheric pressure flow cell was used in the second stage. Limits-of-detection have been estimated. Detection schemes have included both photomultiplier tube (with interference filter) and charge- coupled-device camera (with monochromator). To reduce fluorescence quenching, we have expanded an argon gas stream containing Hg vapor through a micro-jet into a vacuum. The jet is crossed with a laser beam at 253.7 nm to excite atomic fluorescence, which is distinguished from the background by time gating.

Tong, Xiaomei; Barat, Robert B.; Poulos, Arthur T.

1999-12-01

193

A field-space conformal-solution method: Binary vapor-liquid phase behavior  

NASA Astrophysics Data System (ADS)

The field-space conformal solution method provides an entirely new thermodynamic framework for the description of fluid mixtures in terms of the properties of a pure reference fluid. The utility and performance of the method are examined in the special case of vapor-liquid equilibrium correlation for simple mixtures. This is one of several cases in which field-space methods have numerical or theoretical advantages over methods presently used in mixture property correlation; only properties along the vapor pressure curve of the purefluid reference system are required for a complete description of the mixture phase behavior. Vapor-liquid equilibrium data for three binary hydrocarbon mixtures, n-butane + n-pentane, n-butane + n-hexane, and n-butane + n-octane, are correlated with a simple implementation of the method having two independent mixture parameters. Two pure-fluid equations of state, a Peng-Robinson equation and a 32-constant modified Benedict-Webb-Rubin equation, are tested as reference systems. The effects of differences in the quality of the reference system and of a range of mixture component size ratios are examined.

Storvick, T. S.; Fox, J. R.

1990-01-01

194

A qualitative analysis of the effects of water vapor on multi-component vapor-phase carbon adsorption  

SciTech Connect

The effects of water vapor on binary vapor adsorption of toluene and methylene chloride by activated carbon were investigated on a bench-scale experimental system. Three levels of relative humidity (15, 65 and 90 percent) in conjunction with different concentrations of individual adsorbates (from 400 to 1200 ppmv) were tested by tracing the breakthrough curves of each adsorbate eluted from a fixed-bed adsorber. The adsorption capacities of the activated carbon tested for each adsorbate under the various conditions were obtained from calculations based on area integration of the breakthrough curves. It was found that with increasing relative humidity, the shape of breakthrough curves was asymmetrically distorted and the width of the breakthrough curves was broadened for toluene and steepened for methylene chloride. The adsorption capacities for both toluene and methylene chloride were decreased with the increase of relative humidity. The magnitude of the effect of water vapor is greater at the lower toluene concentration and at the higher concentration of methylene chloride. The mechanisms of water vapor influence on the process of multicomponent vapor adsorption are discussed. 12 refs., 9 figs., 1 tab.

Gong, R.; Keener, T.C. [Univ. of Cincinnati, OH (United States)

1993-06-01

195

Metalorganic vapor phase epitaxy of Zn 1? x Fe x Se films  

Microsoft Academic Search

Thin single-crystalline films of the diluted magnetic semiconductor (DMS) Zn1?xFexSe (0 < x ? 0.22) have recently been grown by metalorganic vapor phase epitaxy (MOVEP) [1]. The films were deposited on GaAs(100) substrates in a vertical axisymmetric stagnation-flow reactor equipped with a specially designed split inlet to minimize pre-reactions between the group II and VI precursors. The precursors were (CH3)2Zn:N(C2H5)3,

J. Peck; T. J. Mountziaris; S. Stoltz; A. Petrou; P. G. Mattocks

1997-01-01

196

Experimental study of thermal conductivity of refrigerant R-409A in vapor phase  

NASA Astrophysics Data System (ADS)

Thermal conductivity of refrigerant R-409A in vapor phase was studied in the range of temperatures 306-425 K and pressures 0.12-1.33 MPa. Measurements were performed with the stationary method of coaxial cylinders. Uncertainty of experimental data on thermal conductivity was 1.5-2.5 %, and errors of temperature and pressure measurements did not exceed 0.05 K and 4 kPa, respectively. Approximating dependence of thermal conductivity on pressure and temperature was obtained. Thermal conductivity on dew line and in ideal gas state was calculated.

Verba, O. I.; Raschektaeva, E. P.; Stankus, S. V.

2011-12-01

197

Collective Thomson scattering experiments on a tin vapor discharge in the prepinch phase.  

PubMed

Partially collective Thomson scattering measurements have been performed on a triggered vacuum arc in tin vapor, which is a candidate source of extreme ultraviolet light for application in semiconductor lithography. In this paper, results on the electron densities and temperatures are presented for the prepinch phase of the discharge. Electron densities and temperatures increase from 1 x 10(23) m(-3) to 1 x 10(24) m(-3) and from 5 eV to over 30 eV, respectively, in about 100 ns. The results are confirmed by Stark broadening data. PMID:15600771

Kieft, E R; van der Mullen, J J A M; Kroesen, G M W; Banine, V; Koshelev, K N

2004-11-30

198

Quantitative study of carbon doping of GaAs grown by metalorganic vapor-phase epitaxy  

Microsoft Academic Search

Based on the analysis of experimental data from the atmospheric-pressure-metalorganic vapor-phase epitaxy (AP-MOVPE) of carbon-doped GaAs, using trimethylgallium (TMGa) and arsine (AsH3) as growth precursors and carbon tetrachloride (CCl4) as dopant precursor, the quantitative relation between control parameters, namely growth temperature and flow rates of CCl4 and AsH3, and hole concentration has been investigated and established, which is p=5×108FCCl4F?1.5AsH3exp(2×105\\/RTg), with

Yanning Gong; Jinji Mo; Haisheng Yu; Le Wang; Guanqun Xia

2000-01-01

199

Process for catalytic vapor phase reduction of nitrogen oxides and catalyst composition used therefor  

SciTech Connect

A catalyst composition is disclosed for the vapor phase reduction of nitrogen oxides with ammonia, which consists essentially of a non-noble transition metal compound supported on a shaped carrier comprising a titanium oxide and a clay mineral having an average particle size of 0.1 to 100 microns. The shaped carrier preferably contains an additional component which is an inorganic fibrous material, silica hydrogel, silica sol, or a mixture of at least two of these. An exhaust gas containing nitrogen oxides is treated, with a high percent no removal, by contacting it with the catalyst composition in the presence of ammonia gas at 200 to 600/sup 0/C.

Arima, Y.; Itaya, S.; Tanaka, H.; Yoshioka, T.

1980-02-12

200

Carrier dynamics studies of thick GaN grown by HVPE[Hydride Vapor Phase Epitaxy  

SciTech Connect

The authors present a comparison between optical properties of two samples grown by hydride vapor phase epitaxy, one directly on Sapphire substrate (non-ELO) and one epitaxial lateral overgrown (ELO) on SiO{sub 2} patterned Sapphire substrate. The ELO material shows an improvement of the UV emission and slight decrease of the yellow emission. The band edge emission is red shifted due to the relaxation of the compressive strain. In spite of the increase in the UV emission, the lifetime of the excitons in the ELO material is more than twice lower than non-ELO material. The authors attribute this to screening effects of the background electron concentration.

Bunea, G.E.; Uenlue, M.S.; Goldberg, B.B.

2000-07-01

201

XeF2 vapor phase silicon etch used in the fabrication of movable SOI structures.  

SciTech Connect

Vapor phase XeF{sub 2} has been used in the fabrication of various types of devices including MEMS, resonators, RF switches, and micro-fluidics, and for wafer level packaging. In this presentation we demonstrate the use of XeF{sub 2} Si etch in conjunction with deep reactive ion etch (DRIE) to release single crystal Si structures on Silicon On Insulator (SOI) wafers. XeF{sub 2} vapor phase etching is conducive to the release of movable SOI structures due to the isotropy of the etch, the high etch selectivity to silicon dioxide (SiO{sub 2}) and fluorocarbon (FC) polymer etch masks, and the ability to undercut large structures at high rates. Also, since XeF{sub 2} etching is a vapor phase process, stiction problems often associated with wet chemical release processes are avoided. Monolithic single crystal Si features were fabricated by etching continuous trenches in the device layer of an SOI wafer using a DRIE process optimized to stop on the buried SiO{sub 2}. The buried SiO{sub 2} was then etched to handle Si using an anisotropic plasma etch process. The sidewalls of the device Si features were then protected with a conformal passivation layer of either FC polymer or SiO{sub 2}. FC polymer was deposited from C4F8 gas precursor in an inductively coupled plasma reactor, and SiO{sub 2} was deposited by plasma enhanced chemical vapor deposition (PECVD). A relatively high ion energy, directional reactive ion etch (RIE) plasma was used to remove the passivation film on surfaces normal to the direction of the ions while leaving the sidewall passivation intact. After the bottom of the trench was cleared to the underlying Si handle wafer, XeF{sub 2} was used to isotropically etch the handle Si, thus undercutting and releasing the features patterned in the device Si layer. The released device Si structures were not etched by the XeF{sub 2} due to protection from the top SiO{sub 2} mask, sidewall passivation, and the buried SiO{sub 2} layer. Optimization of the XeF{sub 2} process and the sidewall passivation layers will be discussed. The advantages of releasing SOI devices with XeF{sub 2} include avoiding stiction, maintaining the integrity of the buried SiO{sub 2}, and simplifying the fabrication flow for thermally actuated devices.

Wiwi, M.; Sanchez, Carlos Anthony; Plut, Thomas Alvin; Salazar, M.; Stevens, Jeffrey; Bauer, Todd M.; Ford, C.; Shul, Randy John; Grossetete, Grant David

2010-10-01

202

Thermodynamics of Si(OH) 4 in the vapor phase of water: Henry's and vapor-liquid distribution constants, fugacity and cross virial coefficients  

NASA Astrophysics Data System (ADS)

The fugacity coefficients of Si(OH) 4 are evaluated from solubilities of solid phases of SiO 2 in the vapor phase of water. The virial equation of state, truncated at the third virial coefficient, is employed to describe the fugacity coefficients of Si(OH) 4. The temperature dependencies of the second, B12, and the third, C112, cross virial coefficients for H 2O-Si(OH) 4 interactions are approximated by empirical relations. It is found that silica-water interactions in the vapor phase are significantly more non-ideal compared to water-water interactions. Knowledge of B12 and C112 allows calculation of solubilities of quartz (Q) and amorphous silica (AS) in steam up to the density of 200 kg m -3 in satisfactory agreement with available data, and should provide reasonable solubility values at temperatures where no experimental results exist. The calculated values of the solubility of Q and AS in saturated vapor up to the critical temperature of water, Tc, are tabulated. The partial molar properties of dilute solutes close to the critical point of water are governed by the Krichevskii parameter, the value of which for Si(OH) 4 is evaluated from available data (mainly vapor-liquid distribution constants for silica) to be equal to -187 ± 10 MPa. The knowledge of the thermodynamic properties of Si(OH) 4 in the ideal gas state and in the state of the standard solution in liquid water allows calculating Henry's constant, kH, for Si(OH) 4 up to 623.15 K at water saturation pressure P1?. The theoretically-based equation, containing the Krichevskii parameter, allows extrapolating kH values all the way toward the critical temperature of water. This, in turn, makes possible calculation of the solubility of quartz and amorphous silica in liquid water at P1? at all temperatures up to Tc. The presented results should be useful for modeling solid-liquid-vapor, solid-vapor and liquid-vapor equilibria in the H 2O-SiO 2 system at steam densities up to 200 kg m -3.

Plyasunov, Andrey V.

2012-01-01

203

Mechanistic investigation of non-ideal sorption behavior in natural organic matter. 1. Vapor phase equilibrium.  

PubMed

Results from an experimental and modeling investigation of the influence of thermodynamic properties of highly purified natural organic matter (NOM) on observed equilibrium sorption/desorption behaviors of vapor phase trichloroethylene (TCE) is presented. Identification of glass transition (T(g)) behavior in Leonardite humic acid and Organosolv lignin enabled evaluation of equilibrium and nonequilibrium sorption behavior in glassy and rubbery NOM. Specific differences in vapor phase equilibrium behavior in NOM above and below their T(g) were identified. In the glassy state (below T(g)), sorption of TCE is well-described by micropore models, with enthalpies of sorption characteristic of microporous, glassy macromolecules. Above T(g), sorptive behavior was well-described by Flory-Huggins theory, indicating that the mobility and structural configuration of rubbery NOM materials may be analogous to the characteristic sorption behavior observed in more mobile, rubbery macromolecules, including strong entropic changes during sorption. Results from this work provide further support that, at least for the samples employed in this study, NOM possesses macromolecular characteristics which display sorption behavior similar to synthetic macromolecules-an important assumption in conceptual sorption equilibrium models used in the analysis of the fate and transport of VOCs in the environment. PMID:22642948

Bell, Katherine Young; Leboeuf, Eugene J

2012-06-11

204

The influence of temperature on the polymerization of ethyl cyanoacrylate from the vapor phase  

SciTech Connect

The polymerization of ethyl cyanoacrylate fumes from surface bound initiators is an important step in many novel and mature technologies. Understanding the effect of temperature on the rate of poly(ethyl cyanoacrylate) (PECA) growth and its molecular weight during its polymerization from the vapor phase from surface bound initiators provides insight into the important mechanistic aspects that impact the polymerizations success. In these studies, it is shown that the amount of PECA formed during the polymerization of ECA from a latent fingerprint increases with decreasing temperature, while the polymer molecular weight varies little. This is interpreted to be the result of the loosening of the ion pair that initiates the polymer chain growth and resides on the end of the growing polymer chain with decreasing temperature. Comparison of temperature effects and counter-ion studies show that in both cases loosening the ion pair results in the formation of more polymer with similar molecular weight, verifying this interpretation. These results further suggest that lowering the temperature may be an effective method to optimize anionic vapor phase polymerizations, including the improvement of the quality of aged latent prints and preliminary results are presented that substantiate this prediction.

Dadmun, Mark D [ORNL; Algaier, Dana [University of Tennessee, Knoxville (UTK); Baskaran, Durairaj [University of Tennessee, Knoxville (UTK)

2011-01-01

205

Vapor phase deposition of functional polymers onto paper-based microfluidic devices for advanced unit operations.  

PubMed

Paper-based microfluidic devices have recently received significant attention as a potential platform for low-cost diagnostic assays. However, the number of advanced unit operations, such as separation of analytes and fluid manipulation, that can be applied to these devices has been limited. Here, we use a vapor phase polymerization process to sequentially deposit functional polymer coatings onto paper-based microfluidic devices to integrate multiple advanced unit operations while retaining the fibrous morphology necessary to generate capillary-driven flow. A hybrid grafting process was used to apply hydrophilic polymer coatings with a high surface concentration of ionizable groups onto the surface of the paper fibers in order to passively separate analytes, which allowed a multicomponent mixture to be separated into its anionic and cationic components. Additionally, a UV-responsive polymer was sequentially deposited to act as a responsive switch to control the path of fluid within the devices. This work extends the advanced unit operations available for paper-based microfluidics and allows for more complex diagnostics. In addition, the vapor phase polymerization process is substrate independent, and therefore, these functional coatings can be applied to other textured materials such as membranes, filters, and fabrics. PMID:23113699

Kwong, Philip; Gupta, Malancha

2012-11-09

206

Microwave heated vapor-phase digestion method for biological sample materials.  

PubMed

A microwave heated, vapor-phase nitric acid-hydrogen peroxide digestion method for pulverized, biological sample materials was developed. Sample masses up to 200 mg were digested using calibrated quartz inserts inside first generation type, low-pressure, Teflon-PFA microwave vessels. In the first step, samples were digested in the vapor-phase for 80 min using a progressive heating pattern. Three mL of 70% nitric acid and 0.5 mL of 30% hydrogen peroxide were used as digestion reagents. In the second step, the small residue left after first step digestion was dissolved in 1.4% nitric acid or additionally with 0.5% hydrofluoric acid by heating for 15 min. The digestion method was optimized using pike (Esox lucius) muscle as a test material. The method was further optimized using three certified reference materials. Ca, Cu, Fe, Mg and Zn were determined from NIST-SRM 1577a bovine liver by ICP-AES. Cr and Ni were determined from NIST-SRM 8433 corn bran and NRCC DOLT-2 dogfish liver by GFAAS. For all elements the values obtained were close or within certified limits. Spike recoveries were between 96 to 107%. Digestion efficiency ranged from 91 to 99%. PMID:11210223

Eilola, K; Perämäki, P

2001-01-01

207

Molecular Simulations of Liquid/Vapor Phase Equilibria for Single Component and Binary Mixtures of Nanoparticles  

NASA Astrophysics Data System (ADS)

Self-assembly of nano and colloidal particles into ordered structures is an important technological challenge for the design of future materials and devices. One promising self-assembly technique is the evaporation of nanoparticles suspended in droplets. However, it is difficult to experimentally observe the self-assembly process in the evaporating droplet. Computer simulation provides an avenue with which to address and directly observe the self-assembly of model nano and colloidal particles within the droplet provided an efficient model can be developed. Here we present the liquid-vapor phase envelopes for model particles as a function of particle size. We compare the liquid/vapor phase envelopes and the computational efficiency for several different models including composite particles comprised of Lennard-Jones (LJ) atoms and particles interacting via integrated LJ potentials. Results for binary mixtures of nanoparticles in a solvent of LJ atoms will also be presented. These studies provide a framework for the size range of particles that can be addressed by each model. Sandia is a multiprogram laboratory operated by Sandia Corp., a Lockheed Martin Company, for the United States Department of Energy's National Nuclear Security Administration under Contract DE-AC04-94AL85000.

Horsch, Mark; in't Veld, Pieter; Lechman, Jermey; Grest, Gary

2007-03-01

208

Uptake rate constants and partition coefficients for vapor phase organic chemicals using semipermeable membrane devices (SPMDs)  

NASA Astrophysics Data System (ADS)

To fully utilize semipermeable membrane devices (SPMDs) as passive samplers in air monitoring, data are required to accurately estimate airborne concentrations of environmental contaminants. Limited uptake rate constants ( kua) and no SPMD air partitioning coefficient ( Ksa) existed for vapor-phase contaminants. This research was conducted to expand the existing body of kinetic data for SPMD air sampling by determining kua and Ksa for a number of airborne contaminants including the chemical classes: polycyclic aromatic hydrocarbons, organochlorine pesticides, brominated diphenyl ethers, phthalate esters, synthetic pyrethroids, and organophosphate/organosulfur pesticides. The kuas were obtained for 48 of 50 chemicals investigated and ranged from 0.03 to 3.07 m 3 g -1 d -1. In cases where uptake was approaching equilibrium, Ksas were approximated. Ksa values (no units) were determined or estimated for 48 of the chemicals investigated and ranging from 3.84E+5 to 7.34E+7. This research utilized a test system (United States Patent 6,877,724 B1) which afforded the capability to generate and maintain constant concentrations of vapor-phase chemical mixtures. The test system and experimental design employed gave reproducible results during experimental runs spanning more than two years. This reproducibility was shown by obtaining mean kua values ( n = 3) of anthracene and p, p'-DDE at 0.96 and 1.57 m 3 g -1 d -1 with relative standard deviations of 8.4% and 8.6% respectively.

Cranor, Walter L.; Alvarez, David A.; Huckins, James N.; Petty, Jimmie D.

209

The partition coefficients of ethane between vapor and hydrate phase for methane + ethane + water and methane + ethane + THF + water systems  

Microsoft Academic Search

The vapor–hydrate equilibria were measured firstly for CH4 + C2H6 + water system beyond incipient conditions and the results showed that the partition coefficients of ethane between vapor and hydrate phase were not promising. And then the gas–hydrate equilibria were studied experimentally in detail for CH4 + C2H6 + tetrahydrofuran (THF) + water systems in the temperature range of 274.15–282.15K,

L.-W. Zhang; G.-J. Chen; X.-Q. Guo; C.-Y. Sun; L.-Y. Yang

2004-01-01

210

Effect of Liquid Phase and Vaporization on the Formation of Microstructure of Pr Doped ZnO Varistor  

Microsoft Academic Search

Our previous works and our recent data were summarized to discuss the effect of liquid phase formation and vaporization of the components on the densification, grain growth and change of the microstructure of Pr doped ZnO ceramics in air. In the ZnO-Pr2O3 binary system, eutectic liquid forms at 1382± 5°C° and significant vaporization of the components occurred above the eutectic

Naoki Wakiya; Sung-Yong Chun; Chae Hyun Lee; Osamu Sakurai; Kazuo Shinozaki; Nobuyasu Mizutani

1999-01-01

211

Brand marketing management in China cigarette enterprises  

Microsoft Academic Search

With the competition environment of economic globalization and market internationalization, this paper systematically analyzes some important points of brand and competitiveness, attempts to generalize the main sources of cigarette brand competitiveness from both intrinsic and extrinsic aspects. At the initial phase of brand development, cigarette brand image and impression are of great importance, so as to intensify the awareness and

Kang Canhua; Hang Cao; Yan Xi

2011-01-01

212

Cigarette smuggling mitigates the public health benefits of cigarette taxes  

Microsoft Academic Search

Merriman (2002) argues that cigarette smuggling does not reduce the health benefits of cigarette taxation, because, in addition to the purchase price of smuggled cigarettes, those purchasing smuggled cigarettes have to pay a higher inconvenience price for their cigarettes, so that smuggled cigarettes no more than replace legal cigarettes. Here, it is argued that Merriman is incorrect, that while smuggled

R. Andrew Luccasen III; R. Morris Coats; G. Karahan

2005-01-01

213

Vapor Pressure, Speed of Sound, and PVT-Properties of R-404a in the Vapor Phase  

Microsoft Academic Search

The density (300 363 K, up to 3.5 MPa) and speed of sound (293 373 K, 7.5 480 kPa) in gaseous R-404a have been studied by an isochoric piezometer method and an ultrasonic interferometer, respectively. The pressures of the saturated vapor along the dew line were measured from 298 to 330 K. The experimental uncertainties of the temperature, pressure, density,

V. A. Gruzdev; S. G. Komarov; S. V. Stankus

2008-01-01

214

Desalination of water by vapor-phase transport through hydrophobic nanopores  

NASA Astrophysics Data System (ADS)

We propose a new approach to desalination of water whereby a pressure difference across a vapor-trapping nanopore induces selective transport of water by isothermal evaporation and condensation across the pore. Transport of water through a nanopore with saline water on one side and pure water on the other side under a pressure difference was theoretically analyzed under the rarefied gas assumption using a probabilistic framework that accounts for diffuse scattering from the pore walls as well as reflection from the menisci. The analysis revealed that in addition to salinity, temperature, and pressure difference, the nanopore aspect ratio and the probability of condensation of a water molecule incident on a meniscus from the vapor phase, known as the condensation coefficient, are key determinants of flux. The effect of condensation coefficient on mass flux becomes critical when the aspect ratio is small. However, the mass flux becomes independent of the condensation coefficient as the pore aspect ratio increases, converging to the Knudsen flux for long nanopores. For design of a nanopore membrane that can trap vapor, a minimum aspect ratio is derived for which coalescence of the two interfaces on either side of the nanopore remains energetically unfavorable. Based on this design criterion, the analysis suggests that mass flux in the range of 20-70 g/m2 s may be feasible if the system is operated at temperatures in the range of 30-50 °C. The proposed approach further decouples transport properties from material properties of the membrane, which opens the possibility of engineering membranes with appropriate materials that may lead to reverse osmosis membranes with improved flux, better selectivity, and high chlorine resistance.

Lee, Jongho; Karnik, Rohit

2010-08-01

215

Triple sorbent thermal desorption/gas chromatography/mass spectrometry determination of vapor phase organic contaminants  

SciTech Connect

A thermal desorption/ps chromatography/mass spectrometry (TD/GC/MS) has been evaluated for the determination of volatile organic compounds (VOCS) in vapor phase samples using Carbosieve S-III/Carbotrap/Carotrap C triple sorbent traps (TST) similar to those available from a commercial source. The analysis was carried out with a Hewlett-Packard 5985A or 5995 GC/MS system with a modified injector to adapt an inhouse manufactured short-path desorber for transferring desorbate directly onto a cryofocusing loop for subsequent GC/MS analysis. Vapor phase standards generated from twenty six compounds were used for method validation, including alkanes, alkyl alcohols, alkyl ketones, and alkyl nitrites, a group of representative compounds that have previously been identified in a target airborne matrix. The method was validated based on the satisfactory results in terms of reproducibility, recovery rate, stability, and linearity. A relative, standard deviation of 0.55 to 24.3 % was obtained for the entire TD process (generation of gas phase standards, spiking the standards on and desorbing from TST) over a concentration range of 20 to 500 ng/trap. Linear correlation coefficients for the calibration curves as determined ranged from 0.81 to 0.99 and limits of detection ranged from 3 to 76 ng. For a majority of standards, recoveries of greater than 90% were observed. For three selected standards spiked on TSTS, minimal loss (10 to 22%) was observed after storing the spiked in, a 4{degree}C refrigerator for 29 days. The only chromatographable artifact observed was a 5% conversion of isopropanol to acetone. The validated method been successfully applied, to the determination of VOCs collected from various emission sources in a diversified concentration range.

Ma, C.Y.; Skeen, J.T.; Dindal, A.B.; Higgins, C.E.; Jenkins, R.A.

1994-05-01

216

Calculation of liquid water-hydrate-methane vapor phase equilibria from molecular simulations.  

PubMed

Monte Carlo simulation methods for determining fluid- and crystal-phase chemical potentials are used for the first time to calculate liquid water-methane hydrate-methane vapor phase equilibria from knowledge of atomistic interaction potentials alone. The water and methane molecules are modeled using the TIP4P/ice potential and a united-atom Lennard-Jones potential, respectively. The equilibrium calculation method for this system has three components, (i) thermodynamic integration from a supercritical ideal gas to obtain the fluid-phase chemical potentials, (ii) calculation of the chemical potential of the zero-occupancy hydrate system using thermodynamic integration from an Einstein crystal reference state, and (iii) thermodynamic integration to obtain the water and guest molecules' chemical potentials as a function of the hydrate occupancy. The three-phase equilibrium curve is calculated for pressures ranging from 20 to 500 bar and is shown to follow the Clapeyron behavior, in agreement with experiment; coexistence temperatures differ from the latter by 4-16 K in the pressure range studied. The enthalpy of dissociation extracted from the calculated P-T curve is within 2% of the experimental value at corresponding conditions. While computationally intensive, simulations such as these are essential to map the thermodynamically stable conditions for hydrate systems. PMID:20392117

Jensen, Lars; Thomsen, Kaj; von Solms, Nicolas; Wierzchowski, Scott; Walsh, Matthew R; Koh, Carolyn A; Sloan, E Dendy; Wu, David T; Sum, Amadeu K

2010-05-01

217

Reduction of degradation in vapor phase transported InP/InGaAsP mushroom stripe lasers  

SciTech Connect

The rapid degradation rate generally observed in InP/InGaAsP mushroom stripe lasers can be considerably decreased by regrowing the open sidewalls of the active stripe with low-doped InP in a second epitaxial step using the hydride vapor phase transport technique. This technique does not change the fundamental laser parameters like light-current and current-voltage characteristics. Because of this drastic reduction in degradation, the vapor phase epitaxy regrown InP/InGaAsP mushroom laser seems to be an interesting candidate for application in optical communication.

Jung, H.; Burkhardt, E.G.; Pfister, W.

1988-10-03

218

Gas phase and surface reactions in subatmospheric chemical vapor deposition of tetraethylorthosilicate-ozone  

SciTech Connect

A new physical-chemical model, which applies over a wide range of operating pressures, describes the gas phase and surface reactions in subatmospheric chemical vapor deposition of silicon dioxide for producing inter-layer dielectrics in a cold-wall reactor. Tetraethylorthosilicate (TEOS) reacts in the gas phase to form an intermediate which is adsorbed and reacts on the surface to produce a silicon dioxide film. The results compare favorably with experimental data over a pressure range of 100{endash}600 Torr and a temperature range of 370{endash}500{degree}C. The concentration distributions of TEOS, intermediate and ozone in the gas phase and their ratios at the surface of the wafer are determined to study gas phase nucleation and the relationship between composition distributions and film quality. Previous models based on low pressure data in the range of 30{endash}90 Torr need to be modified to predict accurately the rates of deposition from 100 Torr to atmospheric pressure. Gas phase reactions cause the maximum in the deposition rates to shift to higher pressures at lower deposition temperatures, both in the model and experiments. At higher pressures, particulates are formed by the gas phase reactions which must be included to represent properly the chemical dynamics of the process. The deposition rate increases up to an asymptotic value as the TEOS flow rate is increased; above this level no further increase in growth rate occurs. This is a consequence of the basic mechanism of the surface reaction which predicts the asymptotic behavior observed. {copyright} {ital 1997 American Vacuum Society.}

Gill, W.N.; Ganguli, S. [Department of Chemical Engineering, Rensselaer Polytechnic Institute, Troy, New York 12180-3590 (United States)

1997-07-01

219

Migration of carbon nanotubes from liquid phase to vapor phase in the refrigerant-based nanofluid pool boiling  

PubMed Central

The migration characteristics of carbon nanotubes from liquid phase to vapor phase in the refrigerant-based nanofluid pool boiling were investigated experimentally. Four types of carbon nanotubes with the outside diameters from 15 to 80 nm and the lengths from 1.5 to 10 ?m were used in the experiments. The refrigerants include R113, R141b and n-pentane. The oil concentration is from 0 to 10 wt.%, the heat flux is from 10 to 100 kW·m-2, and the initial liquid-level height is from 1.3 to 3.4 cm. The experimental results indicate that the migration ratio of carbon nanotube increases with the increase of the outside diameter or the length of carbon nanotube. For the fixed type of carbon nanotube, the migration ratio decreases with the increase of the oil concentration or the heat flux, and increases with the increase of the initial liquid-level height. The migration ratio of carbon nanotube increases with the decrease of dynamic viscosity of refrigerant or the increase of liquid phase density of refrigerant. A model for predicting the migration ratio of carbon nanotubes in the refrigerant-based nanofluid pool boiling is proposed, and the predictions agree with 92% of the experimental data within a deviation of ±20%.

2011-01-01

220

Migration of carbon nanotubes from liquid phase to vapor phase in the refrigerant-based nanofluid pool boiling.  

PubMed

The migration characteristics of carbon nanotubes from liquid phase to vapor phase in the refrigerant-based nanofluid pool boiling were investigated experimentally. Four types of carbon nanotubes with the outside diameters from 15 to 80 nm and the lengths from 1.5 to 10 ?m were used in the experiments. The refrigerants include R113, R141b and n-pentane. The oil concentration is from 0 to 10 wt.%, the heat flux is from 10 to 100 kW·m-2, and the initial liquid-level height is from 1.3 to 3.4 cm. The experimental results indicate that the migration ratio of carbon nanotube increases with the increase of the outside diameter or the length of carbon nanotube. For the fixed type of carbon nanotube, the migration ratio decreases with the increase of the oil concentration or the heat flux, and increases with the increase of the initial liquid-level height. The migration ratio of carbon nanotube increases with the decrease of dynamic viscosity of refrigerant or the increase of liquid phase density of refrigerant. A model for predicting the migration ratio of carbon nanotubes in the refrigerant-based nanofluid pool boiling is proposed, and the predictions agree with 92% of the experimental data within a deviation of ±20%. PMID:21711730

Peng, Hao; Ding, Guoliang; Hu, Haitao

2011-03-14

221

Liquid-vapor phase diagram and cluster formation of two-dimensional ionic fluids  

NASA Astrophysics Data System (ADS)

Direct molecular dynamics simulations on interfaces at constant temperature are performed to obtain the liquid-vapor phase diagram of the two-dimensional soft primitive model, an equimolar mixture of equal size spheres carrying opposite charges. Constant temperature and pressure simulations are also carried out to check consistency with interface simulations results. In addition, an analysis of the cluster formation of mixtures of particles with charge asymmetry in the range 1:1 to 1:36 at low and high densities is performed. The number of free ions, when plotted as a function of the positive ion charge, Z+, has an oscillatory behavior and is independent of the density. The formation of aggregates is analyzed in terms of the attraction and repulsion between ions.

Méndez-Maldonado, Gloria Arlette; González-Melchor, Minerva; Alejandre, José

2012-08-01

222

Growth of boron-doped ZnTe homoepitaxial layer by metalorganic vapor phase epitaxy  

NASA Astrophysics Data System (ADS)

We have investigated boron (B) as a n-type dopant for ZnTe homoepitaxial layer by atmospheric pressure metalorganic vapor phase epitaxy using triethylboron (TEB). The introduction of TEB induces considerable change in the photoluminescence spectrum of the layer. Two distinctive luminescence peaks associated with excitons bound to neutral dononor and donor-acceptor pair (DAP) transition are emerged in the spectrum, implying that the incorporated B acts as donor impurity in ZnTe. From the temperature dependence of the PL intensity of DAP recombination, the value of donor level was estimated to be 18 meV. This value seems to be reasonable, comparing with the previous studies on Cl and Al doping of ZnTe.

Saito, Katsuhiko; Yamashita, Tetsuo; Tanaka, Tooru; Nishio, Mitsuhiro; Guo, Qixin; Ogawa, Hiroshi

2006-03-01

223

Photoresponses of manganese-doped gallium nitride grown by metalorganic vapor-phase epitaxy  

NASA Astrophysics Data System (ADS)

The photoresponses of gallium nitride (GaN) doped with manganese (Mn) grown by metalorganic vapor-phase epitaxy were investigated. The transmission spectroscopy obtained from the Mn-doped GaN exhibited three distinct absorption thresholds at approximately 365, 650, and 830 nm, respectively. The below-band-gap absorption peaks were attributed to the fact that the deep Mn-related states mediate the electronic transition between the valence and conduction bands. A below-band-gap spectral response ranging from 400 nm to 1000 nm was also observed from a typical GaN p-i-n photodetector with Mn-doped absorption layer. The significant below-band-gap spectral responses showed that the Mn-doped GaN-based materials have promising applications in intermediate band solar cells.

Sheu, Jinn-Kong; Huang, Feng-Wen; Liu, Yu-Hsuan; Chen, P. C.; Yeh, Yu-Hsiang; Lee, Ming-Lun; Lai, Wei-Chih

2013-02-01

224

Accumulation of Background Impurities in Hydride Vapor Phase Epitaxy Grown GaN Layers  

NASA Astrophysics Data System (ADS)

We report on accumulation of background Si and O impurities measured by secondary ion mass spectrometry (SIMS) at the sub-interfaces in undoped, Zn- and Mg-doped multi-layer GaN structures grown by hydride vapor phase epitaxy (HVPE) on sapphire substrates with growth interruptions. The impurities accumulation is attributed to reaction of ammonia with the rector quartz ware during the growth interruptions. Because of this effect, HVPE-grown GaN layers had excessive Si and O concentration on the surface that may hamper forming of ohmic contacts especially in the case of p-type layers and may complicate homo-epitaxial growth of a device structure.

Usikov, Alexander; Soukhoveev, Vitali; Kovalenkov, Oleg; Syrkin, Alexander; Shapovalov, Liza; Volkova, Anna; Ivantsov, Vladimir

2013-08-01

225

Kinetics of gas-phase reactions relevant to the chemical vapor deposition of indium compounds  

SciTech Connect

Compounds containing indium are of interest for electronic and optical applications. These compounds include III-V semiconductors such as InP and InAs used in both electronic devices and solar cells, and indium tin oxide, which can be used for optical memory and antireflection coatings. Chemical vapor deposition (CVD) techniques can be used to deposit these materials on a variety of substrates. At the temperatures typically employed (550--900 K), gas-phase chemical reactions involving the indium-containing precursor can occur. The kinetics of trimethylindium pyrolysis are investigated in a flow reactor equipped with a molecular-beam mass-spectrometric sampling system. Data are analyzed using a new computational approach that accounts for heat and mass transport in the reactor. The measured activation energy, 46.2 kcal/mol, is in good agreement with previously reported values.

Allendorf, M.D.; McDaniel, A.H.

1998-03-01

226

Liquid-vapor phase diagram and cluster formation of two-dimensional ionic fluids.  

PubMed

Direct molecular dynamics simulations on interfaces at constant temperature are performed to obtain the liquid-vapor phase diagram of the two-dimensional soft primitive model, an equimolar mixture of equal size spheres carrying opposite charges. Constant temperature and pressure simulations are also carried out to check consistency with interface simulations results. In addition, an analysis of the cluster formation of mixtures of particles with charge asymmetry in the range 1:1 to 1:36 at low and high densities is performed. The number of free ions, when plotted as a function of the positive ion charge, Z(+), has an oscillatory behavior and is independent of the density. The formation of aggregates is analyzed in terms of the attraction and repulsion between ions. PMID:22894375

Méndez-Maldonado, Gloria Arlette; González-Melchor, Minerva; Alejandre, José

2012-08-01

227

Carbothermal reduction vapor phase transport growth of ZnO nanostructures: Effects of various carbon sources  

NASA Astrophysics Data System (ADS)

ZnO nanostructures were grown via carbothermal reduction vapor phase transport with carbon black, activated carbon, and graphite powders. Nanostructures can be grown at significantly lower temperatures with carbon black and activated carbon, although with different morphologies compared to graphite. The surface areas of the carbon black and activated carbon are higher than those of graphite; this has been used previously to explain the origin of such growth and morphology differences. We use different ZnO/graphite ratios to equalize surface areas compared to carbon black and eliminate this effect, but differences in nanostructure growth and morphology remain. We discuss the effects of thermodynamics and carbon purity and conclude that the high surface activities of the carbon black and activated carbon are the reason for our results.

Biswas, M.; McGlynn, E.; Henry, M. O.; McCann, M.; Rafferty, A.

2009-05-01

228

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

NASA Astrophysics Data System (ADS)

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

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

2012-08-01

229

Measurement and chemical characterization of vapor-phase mutagens in diesel exhaust. Final report  

SciTech Connect

Methods for the collection, extraction, fractionation, and concentration of vapor-phase compounds from the undiluted exhaust of a medium heavy-duty diesel truck were developed and integrated with chemical analysis and a sensitive mutagenicity bioassay. A sampling system composed of a Teflon filter, polyurethane foam (PUF) and XAD-4 (XAD) adsorbents, in series, was used to directly trap PM and VM in the diesel truck exhaust. The VM on the PUF and XAD adsorbents were extracted with supercritical carbon dioxide (s-CO2) into concentrated methanol fractions which were directly analyzed by a specially modified Ames Salmonella mutagenicity assay and gas chromatograph interfaced to a quadrupole mass spectrometer (GC-MS). The PM-associated mutagens were extracted with organic solvents and assayed for mutagenicity.

Hsieh, D.P.H.; Kado, N.Y.; Okamoto, R.; Kuzmicky, P.A.; Rathbun, C.

1993-03-01

230

GaAs surface control during metalorganic vapor phase epitaxy by reflectance anisotropy spectroscopy  

SciTech Connect

GaAs(001) surfaces are studied during metalorganic vapor phase epitaxy by reflectance anisotropy spectroscopy (RAS). In analogy to RAS spectra measured from GaAs(001) surfaces under ultrahigh vacuum conditions which were simultaneously controlled by reflection high-energy electron diffraction or low-energy electron diffraction certain surface reconstructions can be assigned to specific RAS spectra. Arsenic-rich disordered (4 X 4), centered (4 X 4), and (2 X 4) like surfaces are identified during deoxidation, of the substrate at pregrowth heating. After starting growth the RAS signal shows oscillations the period of which corresponds to the growth of 1 ML of GaAs. This is verified by postgrowth layer thickness measurements. A (4 X 4) reconstructed surface before growth turns out to be the necessary condition for the appearance of these monolayer oscillations in the RAS signal. 16 refs., 6 figs.

Reinhardt, F.; Richter, W.; Mueller, A.B. [Institut fuer Festkoerperphysik der TU Berlin (Germany)] [and others

1993-07-01

231

Solid Composition Control of MgxZn1-xO in Halide Vapor Phase Epitaxy  

NASA Astrophysics Data System (ADS)

Using thermodynamic analysis, the solid compositions of Mg in MgxZn1-xO grown by halide vapor phase epitaxy (HVPE) are calculated in terms of the various input partial pressures of the gaseous species. It is revealed that the Mg composition shows temperature stability up to 1200 °C, while there is a strong dependence on the input VI/II ratio and the input H2 partial pressure at high temperatures. Based on the thermodynamic calculations, the epitaxial growth of MgxZn1-xO layers with different Mg compositions has been demonstrated. The thermodynamic model is found to accurately describe the experimentally observed dependence of Mg compositions on the input VI/II ratio that is used in the growth of MgxZn1-xO.

Fujii, Tetsuo; Yoshii, Naoki; Kumagai, Yoshinao; Koukitu, Akinori

2010-12-01

232

Low-temperature growth of GaAs with high quality by metalorganic vapor phase epitaxy  

NASA Astrophysics Data System (ADS)

Growth of GaAs by MOVPE (Metal-Organic Vapor-Phase Epitaxy) at a much lower temperature than conventional conditions of 650°C required to produce highly resistive buffer layers and molecular-layer-level abrupt heterojunctions and doped-layer interfaces. It has been widely recognized that growth at 550~600°C causes poor morphological surfaces on the grown layers. This paper describes a fundamental improvement of the low-temperature growth of GaAs, resulting in smooth surfaces with very low impurity concentrations. Excellent GaAs layers can be grown at 500°C by increasing partial pressure of AsH3 during growth. The method has been applied to high quality epitaxial layers for electronic device production.

Sakaguchi, Harunori; Mishima, Tomoyoshi; Meguro, Takeshi; Fujiwara, Yasufumi

2009-05-01

233

Mechanism of doping gallium arsenide with carbon tetrachloride during organometallic vapor-phase epitaxy  

NASA Astrophysics Data System (ADS)

The rates of decomposition of carbon tetrachloride (CCl4), triethylgallium (TEGa), and tertiarybutylarsine (TBAs), and the rate of GaAs film growth, were measured as a function of the process conditions during organometallic vapor phase epitaxy. In addition, the reaction of CCl4 with the GaAs(001) surface was monitored in ultrahigh vacuum using infrared spectroscopy, temperature-programmed desorption, and scanning tunneling microscopy. These experiments have revealed that CCl4 adsorbs onto Ga sites, and decomposes by transferring chlorine ligands to other Ga atoms on the surface. Chlorine and gallium desorb from the surface as GaCl, while the carbon incorporates into the lattice. Triethylgallium is consumed by two competing reactions: GaAs film growth and GaCl etching. Depending on the V/III and IV/III ratios and temperature, the etch rate can be high enough to prevent any GaAs deposition.

Warddrip, M. L.; Kappers, M. J.; Li, L.; Qi, H.; Han, B. K.; Gan, S.; Hicks, R. F.

1997-10-01

234

Vapor-phase adsorption kinetics of 1-decene on H-terminated Si(100).  

SciTech Connect

We have investigated in situ and in real time vapor-phase self-assembly of 1-decene on Si, using attenuated total reflection Fourier transform infrared spectroscopy (ATR-FTIRS). The adsorption of 1-decene on hydrogenated Si(100) results in a decane-terminated hydrophobic surface, indicated by the sessile-drop water contact angle at 107 {+-} 2. This maximum contact angle is achieved at 160 C under 30 mTorr of vapor-phase 1-decene. The fractional surface coverage of decane, calculated from the IR absorbance of C-H stretching vibrational modes near 2900 cm{sup -1}, follows a Langmuir isotherm. The absolute surface coverage calculated from the IR absorbance saturates at 3.2 x 10{sup 14} cm{sup -2}. On the basis of this isotherm, the empirical rate constant (k{prime}{sub 2}) that governs the rate-limiting step in 1-decene adsorption on HF-treated Si(100) is (3.3 {+-} 0.7) x 10{sup -2} min{sup -1}. The thickness and cant angle of the decane monolayer at the saturation coverage are calculated from angle resolved X-ray photoelectron spectroscopy (AR-XPS). The calculated thickness ranges from 8.4 to 18 {angstrom} due to the uncertainty in the attenuation lengths of C(1s) and Si(2p) photoelectrons through the decane layer. For the same uncertainty, the calculated cant angle ranges from 0 to 55{sup o}. Spectroscopic ellipsometry is independently used to approximate the film thickness at 16 {angstrom}. Monitoring the decane monolayer over a period of 50 days using AR-XPS indicates that the Si surface underneath the decane monolayer gets oxidized with time, leading to the degradation of the decane layer.

Kosuri, Madhava R. (University of New Mexico, Albuquerque, NM); Mayer, Thomas Michael; Han, Sang M. (University of New Mexico, Albuquerque, NM); Bunker, Bruce Conrad; Li, Qiming (University of New Mexico, Albuquerque, NM); Gerung, Henry (University of New Mexico, Albuquerque, NM)

2003-06-01

235

Waste retrieval sluicing system vapor sampling and analysis plan for evaluation of organic emissions, process test phase III.  

SciTech Connect

This sampling and analysis plan identifies characterization objectives pertaining to sample collection, laboratory analytical evaluation, and reporting requirements for vapor samples obtained to address vapor issues related to the sluicing of tank 241-C-106. Sampling will be performed in accordance with Waste Retrieval Sluicing System Emissions Collection Phase III (Jones 1999) and Process Test Plan Phase III, Waste Retrieval Sluicing System Emissions Collection (Powers 1999). Analytical requirements include those specified in Request for Ecology Concurrence on Draft Strategy/Path Forward to Address Concerns Regarding Organic Emissions from C-106 Sluicing Activities (Peterson 1998). The Waste Retrieval Sluicing System was installed to retrieve and transfer high-heat sludge from tank 241-C-106 to tank 241-AY-102, which is designed for high-heat waste storage. During initial sluicing of tank 241-C-106 in November 1998, operations were halted due to detection of unexpected high volatile organic compounds in emissions that exceeded regulatory permit limits. Several workers also reported smelling sharp odors and throat irritation. Vapor grab samples from the 296-C-006 ventilation system were taken as soon as possible after detection; the analyses indicated that volatile and semi-volatile organic compounds were present. In December 1998, a process test (phase I) was conducted in which the pumps in tanks 241-C-106 and 241-AY-102 were operated and vapor samples obtained to determine constituents that may be present during active sluicing of tank 241-C-106. The process test was suspended when a jumper leak was detected. On March 7, 1999, phase I1 of the process test was performed; the sluicing system was operated for approximately 7 hours and was ended using the controlled shutdown method when the allowable amount of solids were transferred to 241-AY-102. The phase II test was successful, however, further testing is required to obtain vapor samples at higher emission levels and to demonstrate control of the VOC below acceptable limits during the different modes of sluicing. A goal of phase III of the process test will be to obtain representative vapor samples at higher concentrations than those achieved in phase I and phase I1 of the process test. During phase III of the process test, vapor samples will be obtained from the 296-C-006 ventilation system stack. Ambient air samples will also be obtained at two locations within 241-C Tank Farm. Results will be used to address the following: (1) Provide gas composition data that can be used to determine personnel protective measures, (2) Provide gas composition data that can be used for control equipment selection and design, if required, and (3) Substantiate that ammonia and organic emissions are below regulatory thresholds during the test.

SASAKI, L.M.

1999-05-19

236

On the deposition of volatiles and semivolatiles from cigarette smoke aerosols: relative rates of transfer of nicotine and ammonia from particles to the gas phase.  

PubMed

The hypothesis that elevated levels of ammonia-releasing compounds in tobacco and ammonia in mainstream (MS) smoke increase the rate and amount of nicotine evaporation from the particles of MS smoke aerosol was examined by kinetic modeling and experiments with MS cigarette smoke. Computational simulation of a kinetic mechanism describing volatile loss of nicotine, ammonia, and acetic acid from an aqueous solution was used to compute the time-dependent concentration of all species in the model. Because of the high volatility of ammonia relative to that of nicotine, variation over a wide range of initial ammonia concentration had no significant effect upon the rate of loss of nicotine from the model system. The effects of a variation in the volatile loss rate constant for ammonia and for the acid were examined. The simulations show that ammonia is lost from the model solution at a greater rate than nicotine and acid, and the loss of volatile acid has a significant role in the rate and amount of nicotine loss. Simulations with a model system undergoing a continuous steady addition of ammonia showed that high rates of ammonia addition could significantly increase the rate of nicotine volatile loss from the model solution. A series of smoking experiments was performed using blended cigarettes connected to a denuder tube. Deposition of smoke constituents can occur directly from the gas phase and by the deposition of smoke aerosol particles themselves. As nicotine exists >99% in the particle phase of MS smoke, in the absence of particle deposition, denuder tube deposition of nicotine occurs via the evaporation-deposition pathway. Solanesol, a nonvolatile tobacco and smoke terpene, was used to quantify the amount of particle deposition onto the denuder tube. The amount of ammonia deposited on the denuder tube was an order of magnitude greater than that of nicotine, showing that ammonia evaporates from the MS smoke particles much faster than does nicotine. The experimental results were supported and explained by the aqueous model simulations. Included in these experiments are cigarettes that differ in their MS smoke ammonia content by a factor of ca. five. However, an increased amount of MS smoke ammonia does not increase the rate of nicotine loss from the particles. The combined results support the conclusion that ammonia in mainstream smoke has little effect, if any, upon the rate and amount of nicotine evaporation from MS smoke particles. PMID:15310234

Seeman, Jeffrey I; Lipowicz, Peter J; Piadé, Jean-Jacques; Poget, Laurent; Sanders, Edward B; Snyder, James P; Trowbridge, Clarence G

2004-08-01

237

Mid-infrared laser-absorption diagnostic for vapor-phase fuel mole fraction and liquid fuel film thickness  

NASA Astrophysics Data System (ADS)

A novel two-wavelength mid-infrared laser-absorption diagnostic has been developed for simultaneous measurements of vapor-phase fuel mole fraction and liquid fuel film thickness. The diagnostic was demonstrated for time-resolved measurements of n-dodecane liquid films in the absence and presence of n-decane vapor at 25°C and 1 atm. Laser wavelengths were selected from FTIR measurements of the C-H stretching band of vapor n-decane and liquid n-dodecane near 3.4 ?m (3000 cm-1). n-Dodecane film thicknesses <20 ?m were accurately measured in the absence of vapor, and simultaneous measurements of n-dodecane liquid film thickness and n-decane vapor mole fraction (300 ppm) were measured with <10% uncertainty for film thicknesses <10 ?m. A potential application of the measurement technique is to provide accurate values of vapor mole fraction in combustion environments where strong absorption by liquid fuel or oil films on windows make conventional direct absorption measurements of the gas problematic.

Porter, J. M.; Jeffries, J. B.; Hanson, R. K.

2011-02-01

238

Vapor-phase synthesis of ethyl tert -butyl ether on heteropoly acid-polymer composite film catalysts  

Microsoft Academic Search

H3PMo12O40-polysulfone and H3PMo12O40-polyphenylene oxide composite film catalysts were prepared by a membrane preparation technique. They showed the higher catalytic activities than H3PMo12O40 in the vapor-phase synthesis of ethyl tert-butyl ether.

Gyo Ik Park; Seong Soo Lim; In Kyu Song; Wha Young Lee

2002-01-01

239

Some aspects of the vapor phase Beckmann rearrangement for the production of ?-caprolactam over high silica MFI zeolites  

Microsoft Academic Search

A high silica MFI zeolite catalyst has been developed for the vapor phase Beckmann rearrangement of cyclohexanone oxime to ?-caprolactam. Methanol fed into the reactor with the oxime improves the yield of caprolactam. Methanol is not converted to dimethylether during the reaction. Moreover, when ammonia is fed to the catalyst with cyclohexanone oxime and methanol, the selectivity remains at a

Hiroshi Ichihashi; Masaru Kitamura

2002-01-01

240

Melting and Vaporization of the 1223 Phase in the System (Tl-Pb-Ba-Sr-Ca-Cu-O).  

National Technical Information Service (NTIS)

The melting and vaporization of the 1223 ((Tl,Pb):(Ba,Sr):Ca:Cu) oxide phase in the system (Tl-Pb-Ba-Sr-Ca-Cu-O) have been investigated using a combination of dynamic methods (differential thermal analysis, thermogravimetry, effusion) and post-quenching c...

L. P. Cook W. Wong-Ng P. Paranthaman

1996-01-01

241

Nanotribology of a Vapor Phase Lubricant: A Quartz Crystal Microbalance Study of Tricresylphosphate (TCP) Reactive Films on Iron and Chrome  

Microsoft Academic Search

Vapor phase lubrication is receiving increased attention as a high temperature lubrication technique. We show how a quartz crystal microbalance (QCM) under ultra-high vacuum can be used to characterize reactions and film formation of tricresylphosphate (TCP) on both chromium and iron surfaces. The effect of oxygen on film formation was also studied. Shifts in QCM resonant frequency and amplitude are

Cherno Jaye; Mohammed Abdelmaksoud; Jonathan Bender; Jacqueline Krim

2002-01-01

242

Use of dissolved and vapor-phase gases to investigate methanogenic degradation of petroleum hydrocarbon contamination in the subsurface  

Microsoft Academic Search

At many sites contaminated with petroleum hydrocarbons, methanogenesis is a significant degradation pathway. Techniques to estimate CH4 production, consumption, and transport processes are needed to understand the geochemical system, provide a complete carbon mass balance, and quantify the hydrocarbon degradation rate. Dissolved and vapor-phase gas data collected at a petroleum hydrocarbon contaminated site near Bemidji, Minnesota, demonstrate that naturally occurring

Richard T. Amos; K. Ulrich Mayer; Barbara A. Bekins; Geoffrey N. Delin; Randi L. Williams

2005-01-01

243

Production of nanocrystalline silicon layers using the plasma enhanced chemical vapor deposition from the gas phase of silicon tetrafluoride  

Microsoft Academic Search

The production of silicon layers using plasma enhanced chemical vapor deposition in the mixture of silicon tetrafluoride and hydrogen is reported. The samples have been analyzed by X-ray diffraction, Raman spectroscopy, and secondary ion mass spectrometry. The phase composition of the layers is nanocrystalline silicon with the crystalline-domain sizes from 3 to 9 nm in dependence of the conditions of

P. G. Sennikov; S. V. Golubev; V. I. Shashkin; D. A. Pryakhin; M. N. Drozdov; B. A. Andreev; Yu. N. Drozdov; A. S. Kuznetsov; H.-J. Pohl

2009-01-01

244

Determination of the Adsorption Isotherm of Vapor-Phase Mercury Chloride on Powdered Activated Carbon Using Thermogravimetric Analysis  

Microsoft Academic Search

This study investigated the use of thermogravimetric analysis (TGA) to determine the adsorptive capacity and adsorption isotherm of vapor-phase mercury chloride on powdered activated carbon (PAC). The technique is commonly applied to remove mercury-containing air pollutants from gas streams emitted from municipal solid waste incinerators. An alternative form of powdered activated carbon derived from a pyrolyzed tire char was prepared

Hsun-Yu Lin; Chung-Shin Yuan; Wei-Ching Chen; Chung-Hsuang Hung

2006-01-01

245

THE EFFECT OF WATER (VAPOR-PHASE) AND CARBON ON ELEMENTAL MERCURY REMOVAL IN A FLOW REACTOR  

EPA Science Inventory

The paper gives results of studying the effect of vapor-phase moisture on elemental mercury (Hgo) removal by activated carbon (AC) in a flow reactor. tests involved injecting AC into both a dry and a 4% moisture nitrogen (N2) /Hgo gas stream. A bituminous-coal-based AC (Calgon WP...

246

Vapor-phase oxidation of 3-picoline to nicotinic acid over Cr 1? x Al x VO 4 catalysts  

Microsoft Academic Search

Some metal vanadates were precipitated as the pure phases by adjusting the pH of aqueous solutions of the raw materials. The precipitates were calcined at 550°C and tested for the vapor phase oxidation of 3-picoline to nicotinic acid. Chromium vanadate showed the highest activity among the vanadates tested; its structure belongs to monoclinic CrVO4-I. An addition of aluminum into CrVO4-I

Tetsuya Shishido; Zhaoxia Song; Eriko Kadowaki; Ye Wang; Katsuomi Takehira

2003-01-01

247

Growth of strained GaAs1-ySby layers using metalorganic vapor phase epitaxy  

NASA Astrophysics Data System (ADS)

The growth of pseudomorphically strained GaAs1-ySby layers with high Sb-mole fractions of y?0.35 are desired on GaAs substrates for making lasers and detectors in the mid-infrared range. The effect of gas-phase precursor chemistry on the strained-layer Sb-incorporation efficiency in metalorganic vapor phase epitaxy (MOVPE) was determined using four combinations of ethyl- and methyl-Ga and Sb precursors. The Sb-mole fractions in the strained GaAs1-ySby layers were found to be lower than those in relaxed films due to the strain-induced ‘lattice-latching’ effects. The Sb-mole fraction in the strained GaAs1-ySby layers decreased with the increasing AsH3/Ga ratio for all the precursor chemistries. Higher Sb-incorporation efficiencies were observed for the ethyl-Ga chemistries. The experimental results were discussed in terms of lattice-latching effects, Sb-segregation phenomena and different decomposition kinetics for various precursor chemistries.

Khandekar, A. A.; Yeh, J. Y.; Mawst, L. J.; Song, Xueyan; Babcock, S. E.; Kuech, T. F.

2007-01-01

248

Spectroscopic determination of enthalpies of sublimation of organic materials in the vapor phase: Benzoic acid, ferrocene, and naphthalene  

NASA Astrophysics Data System (ADS)

Techniques for determining the enthalpies of sublimation of low volatile materials in the vapor phase are quite rare. Although benzoic acid, ferrocene, and naphthalene are used as reference materials for indirect determination of vapor pressure of volatile materials, the discrepancy of the values of their enthalpies of sublimation is considerably large (˜10-15 kJ/mol). In this work, the enthalpies of sublimation of vapors of these materials are determined using absorbance spectroscopy in the ultraviolet region of the electromagnetic spectrum. This methodology is based on the linear proportionality between the density of the saturated gas of the material and the absorbance of the gas. The determined values of enthalpies of sublimation are in excellent agreement with the mean value of those reported in literature and those recommended by the ICTAC. This method is shown to be accurate and rapid.

Hikal, Walid M.; Weeks, Brandon L.

2013-03-01

249

Magnetism of cigarette ashes  

Microsoft Academic Search

Mineral composition of cigarette ashes is well studied in the literature, but no reports are available about the magnetic fraction. Our study presents an investigation of the basic magnetic characteristics of ashes from several commercially available cigarette brands and a wood ash. Magnetic susceptibility, which is a concentration-dependent parameter in case of uniform mineralogy, shows that cigarette ashes contain relatively

Neli Jordanova; Diana Jordanova; Bernard Henry; Maxime Le Goff; Dimo Dimov; Tsenka Tsacheva

2006-01-01

250

Cigars, Cigarettes, and Adolescents  

ERIC Educational Resources Information Center

|Objective: To examine public health implications of adolescent use of cigars only, cigarettes only, and both cigarettes and cigars. Methods: A cross-sectional health risk survey was administered to a random sample of 4486 high school students in a Midwestern county. Results: More adolescents reported using both cigarettes and cigars (10.6%) than…

Brooks, Ashley; Larkin, Elizabeth M. Gaier; Kishore, Sonal; Frank, Scott

2008-01-01

251

Cigarette Ignition Performance  

Microsoft Academic Search

Two sample cigarettes (coded B and D) along with a control were tested according to the two cigarette ignition propensity test methods published by the National Institute of Standards and Technology (NIST). The primary test uses duck fabrics over polyurethane foam in a flat configuration, and the secondary test uses Whatman #2 filter paper. The three cigarettes were also tested

J. T. Wanna; P. X. Chen

2001-01-01

252

Vapor-phase silanization of oxidized porous silicon for stabilizing composition and photoluminescence  

NASA Astrophysics Data System (ADS)

A vapor-phase deposition approach to the silanization modification of the oxidized porous silicon (PSi) surface using (CH3O)3Si(CH2)3NH2 has been exploited. Standard clean (SC)-1 (NH3H2O/H2O2/H2O, 1:1:5,v/v) and SC-2 [HCl/H2O2/H2O (1:1:6,v/v)] solutions are utilized for the first time to obtain oxidized PSi and have been proved to be a very efficient combination for creating Si-OH species on the PSi surface. After the modification, an amine group terminated surface was successfully created as demonstrated by the contact angle with water, the x-ray photoelectron spectroscopy, and the Fourier transform infrared (FTIR) spectra. The influences of the surface derivatives on the composition stability of the PSi layer and on its photoluminescence properties were investigated by means of FTIR spectra, photoluminescence spectra, and time-resolved photoluminescence measurements.

Li, Hong-Liang; Zhu, Yingchun; Xu, Dongsheng; Wan, Yong; Xia, Linhua; Zhao, Xiu-Song

2009-06-01

253

Semipolar GaN growth on patterned sapphire substrates by hydride vapor phase epitaxy  

NASA Astrophysics Data System (ADS)

This paper presents the growth of thick semipolar {10-11}, {11-22}, and {20-21} GaN layers on n, r, and {22-43} patterned sapphire substrates (PSSs), respectively, by hydride vapor phase epitaxy. The reduction rate of the dislocation density varied with growth planes. For {10-11} GaN layers, the dislocation density drastically decreased at over 100 ?m, which was as fast the reduction rate as in the case of the c-plane. It was revealed that the reduction rate of the dislocation density could be controlled by the proper selection of the growth plane. We obtained a freestanding GaN of 2 inch diameter. Thick GaN growth led to the self-separation of the GaN layer from the PSS during cooling process. The separation plane formed at the interface between GaN and PSS, which is different from the case of a conventional c-plane GaN/sapphire. The separationability of the GaN layer from the PSS depended on the selective growth area of the sapphire sidewall.

Yamane, K.; Okada, N.; Furuya, H.; Tadatomo, K.

2013-03-01

254

Optical Properties of ZnO Soccer-Ball Structures Grown by Vapor Phase Transport  

NASA Astrophysics Data System (ADS)

ZnO soccer balls were grown on an Au-catalyzed Si(100) substrate by vapor phase transport (VPT) with a mixture of zinc oxide and graphite powders. Temperature-dependent PL was carried out to investigate the mechanism governing the quenching behavior of the PL spectra. From the PL spectra of the ZnO soccer balls at 10 K, several PL peaks were observed at 3.365, 3.318, 3.249, and 3.183 eV corresponding to excitons bound to neutral donors (D\\text{oX), a donor--acceptor pair (DAP), first-order longitudinal optical phonon replica of donor--acceptor pair (DAP-1LO), and DAP-2LO, respectively. The mixed system composed of the free exciton (FX) and D\\text{oX and the DAP radiative lifetimes were estimated with a theoretical relation between the lifetime and the spectral width. The exciton radiative lifetimes were observed to increase linearly with temperature.

Nam, Giwoong; Lee, Sang-heon; Kim, Soaram; Kim, Min Su; Kim, Do Yeob; Yim, Kwang Gug; Lee, Dong-Yul; Kim, Jin Soo; Kim, Jong Su; Son, Jeong-Sik; Kim, Sung-O; Jung, Jae Hak; Leem, Jae-Young

2012-02-01

255

Unintentional Ga incorporation in metalorganic vapor phase epitaxy of In-containing III-nitride semiconductors  

NASA Astrophysics Data System (ADS)

We prepared InAlN barrier layer films on GaN buffer layers using the metalorganic vapor phase epitaxy (MOVPE) method and investigated the InAlN/GaN heterointerfaces. Secondary ion spectroscopy experiments revealed that a quaternary alloy of InAlGaN is grown on GaN even when trimethylindium (TMIn) and trimethylaluminum (TMAl) are exclusively supplied as group-III precursors, indicating that Ga is unintentionally incorporated into the InAlN layers. This Ga incorporation is also observed in InGaN/GaN heterostructures. Our systematic investigations of the growth condition dependence, such as the TMIn flow rate, indicate that the Ga is supplied by a transmetalation reaction between TMIn and residual Ga on the flow distributor in the reactor. Here, we show that the Ga incorporation can be eliminated by adopting an elaborate growth sequence, including reactor cleaning and regrowth processes. This study provides guides for designing the MOVPE reactor configuration, as well as the growth sequences, for the growth of device structures with In-containing nitride layers.

Hiroki, Masanobu; Oda, Yasuhiro; Watanabe, Noriyuki; Maeda, Narihiko; Yokoyama, Haruki; Kumakura, Kazuhide; Yamamoto, Hideki

2013-11-01

256

Identification of Si and O donors in hydride-vapor-phase epitaxial GaN  

NASA Astrophysics Data System (ADS)

Donor impurity excitation spectra in the infrared from two high-quality, not-intentionally doped, hydride-vapor-phase epitaxial GaN wafers are reported. Two previously observed shallow donors which we designate N1 and N2 were observed in both wafers. However, spectra of one wafer are dominated by N1 and spectra of the other by N2. A comparison of infrared and secondary ion mass spectroscopic data allows identification of N1 as Si and N2 as O. Silicon is the shallowest uncompensated donor in these samples with an activation energy of 30.18+/-0.1 meV in the freestanding Samsung wafer. The activation energy of O is found to be 33.20+/-0.1 meV. An unidentified third donor with an activation energy of 31.23+/-0.1 meV also was observed. Integrated absorption cross sections are found to be 8.5×10-14 cm for Si and 8.6×10-14 cm for O.

Moore, W. J.; Freitas, J. A.; Braga, G. C. B.; Molnar, R. J.; Lee, S. K.; Lee, K. Y.; Song, I. J.

2001-10-01

257

Self-assembly of Arg-Phe nanostructures via the solid-vapor phase method.  

PubMed

We report for the first time on the self-assembly of nanostructures composed exclusively of alternating positively charged and hydrophobic amino acids. A novel arginine/phenylalanine octapeptide, RF8, was synthesized. Because the low hydrophobicity of this sequence makes its spontaneous ordering through solution-based methods difficult, a recently proposed solid-vapor approach was used to obtain nanometric architectures on ITO/PET substrates. The formation of the nanostructures was investigated under different preparation conditions, specifically, under different gas-phase solvents (aniline, water, and dichloromethane), different peptide concentrations in the precursor solution, and different incubation times. The stability of the assemblies was experimentally studied by electron microscopy and thermogravimetric analysis coupled with mass spectrometry. The secondary structure was assessed by infrared and Raman spectroscopy, and the arrays were found to assume an antiparallel ?-sheet conformation. FEG-SEM images clearly reveal the appearance of fibrillar structures that form extensive homogeneously distributed networks. A close relationship between the morphology and preparation parameters was found, and a concentration-triggered mechanism was suggested. Molecular dynamics simulations were performed to address the thermal stability and nature of intermolecular interactions of the putative assembly structure. Results obtained when water is considered as solvent shows that a stable lamellar structure is formed containing a thin layer of water in between the RF8 peptides that is stabilized by H-bonding. PMID:23286315

Liberato, Michelle S; Kogikoski, Sergio; Silva, Emerson R; Coutinho-Neto, Mauricio D; Scott, Luis P B; Silva, Ricardo H; Oliveira, Vani X; Ando, Rômulo A; Alves, Wendel A

2013-01-14

258

High-Temperature Growth of GaP on Si Substrates by Metalorganic Vapor Phase Epitaxy  

NASA Astrophysics Data System (ADS)

GaP was grown on misoriented Si substrates using metalorganic vapor phase epitaxy (MOVPE). At 700 and 800 °C, no mirror surface was obtained. A mirror surface was achieved at 830 °C with a high PH3 flow rate. The island nucleation density at the initial growth stage increased with temperature between 700 and 800 °C and saturated beyond 800 °C. Islands with a density of 1011 cm-2 nucleated at 830 °C. Cross-sectional transmission electron microscopy (c-TEM) shows that a 5-nm-thick GaP layer was formed by coalescence of the islands at 830 °C. A cross-hatched pattern (CHP) was observed for a 200-nm-thick GaP layer grown at 830 °C. The CHP indicates that the quality of the GaP layer was high. Cross-sectional TEM reveals that few stacking faults and dislocations exist in 5- and 40-nm-thick GaP layers on Si substrates.

Takano, Yasushi; Morizumi, Kenta; Watanabe, Satoshi; Masuda, Hiroyuki; Okamoto, Takuya; Noda, Kunihiro; Fukuda, Shinya; Ozeki, Tomokazu; Kuwahara, Kazuhiro; Fuke, Shunro; Furukawa, Yuzo; Yonezu, Hiroo

2009-01-01

259

Characterization of Cu2ZnSnS4 Thin Films Prepared by Vapor Phase Sulfurization  

NASA Astrophysics Data System (ADS)

Cu2ZnSnS4 (CZTS) thin films could be successfully formed by vapor phase sulfurization of electron-beam-evaporated precursors on a soda-lime glass substrate. This film is an interesting material for absorber layer in a solar cell because all the constituents are readily available in the earth’s crust. In this study, using a new type of precursors containing ZnS, we could achieve the strong adhesion of CZTS films to a glass substrate. From the result of scanning electron microscope (SEM) observation, it was confirmed that the surface morphology of CZTS films is much improved by using this new type of precursor. The X-ray diffraction pattern revealed that CZTS thin films have kesterite structures. From the measurement of transmittance and reflectance, the optical band-gap energy was estimated as 1.40-1.45 eV, which is very close to the optimum value for a solar-cell absorber. The highest open-circuit voltage of our cells based on CZTS films is 735 mV, which is a higher value than that reported in numerous other studies on CZTS.

Katagiri, Hironori; Ishigaki, Naoya; Ishida, Takeshi; Saito, Kotoe

2001-02-01

260

Investigation of deep levels in bulk GaN material grown by halide vapor phase epitaxy  

NASA Astrophysics Data System (ADS)

Electron traps in thick free standing GaN grown by halide vapor phase epitaxy were characterized by deep level transient spectroscopy. The measurements revealed six electron traps with activation energy of 0.252 (E1), 0.53 (E2), 0.65 (E4), 0.69 (E3), 1.40 (E5), and 1.55 eV (E6), respectively. Among the observed levels, trap E6 has not been previously reported. The filling pulse method was employed to determine the temperature dependence of the capture cross section and to distinguish between point defects and extended defects. From these measurements, we have determined the capture cross section for level E1, E2, and E4 to 3.2 × 10-16 cm2, 2.2 × 10-17 cm2, and 1.9 × 10-17 cm2, respectively. All of the measured capture cross sections were temperature independent in the measured temperature range. From the electron capturing kinetic, we conclude that trap E1, E2, and E3 are associated with point defects. From the defect concentration profile obtained by double correlated deep level transient spectroscopy, we suggest that trap E4 and E6 are introduced by the polishing process.

Duc, Tran Thien; Pozina, Galia; Janzén, Erik; Hemmingsson, Carl

2013-10-01

261

Dislocation mechanisms in the GaN lateral overgrowth by hydride vapor phase epitaxy  

SciTech Connect

The authors have carried out a series of lateral epitaxial overgrowths (LEO) of GaN through thin oxide windows by the hydride vapor phase epitaxy (HVPE) technique at different growth temperatures. High lateral growth rate at 1,100 C allows coalescing of neighboring islands into a continuous and flat film, while the lower lateral growth rate at 1,050 C produces triangular-shaped ridges over the growth windows. In either case, threading dislocations bend into laterally grown regions to relax the shear stress developed in the film during growth. In regions close to the mask edge, where the shear stress is highest, dislocations interact and multiply into arrays of edge dislocations lying parallel to the growth window. This multiplication and pileup of dislocations cause a large-angle tilting of the laterally grown regions. The tilt angle is high ({approximately}8 degrees) when the growth is at 1,050 C and becomes smaller (3--5 degrees) at 1,100 C. At the coalescence of growth facets, a tilt-type grain boundary is formed. During the high-temperature lateral growth, the tensile stress in the GaN seed layer and the thermal stress from the mask layer both contribute to a high shear stress at the growth facets. Finite element stress simulations suggest that this shear stress may be sufficient to cause the observed excessive dislocation activities and tilting of LEO regions at high growth temperatures.

Kuan, T.S.; Inoki, C.K.; Hsu, Y.; Harris, D.L.; Zhang, R.; Gu, S.; Kuech, T.F.

2000-07-01

262

Metalorganic Vapor Phase Epitaxy Growth of InAlAsSb on InP  

NASA Astrophysics Data System (ADS)

This paper studies the characteristic of InAlAsSb grown on InP substrates by metalorganic vapor phase epitaxy (MOVPE) using trimethylindium (TMI), trimethylaluminum (TMA), trimethylantimony (TMSb) and arsine (AsH3). Composition analyses of InAlAsSb layers grown at various TMSb flow rates show, for the first time, that the Al concentration in the InAlAsSb layer decreases as the TMSb flow rate increases. We also find that the growth rate of InAlAsSb decreases remarkably as the TMSb flow rate increases. To clarify the reasons for these phenomena, the growth rates of the InAsSb and AlAsSb components are estimated. The growth rate of AlAsSb component shows a similar remarkable tendency with the InAlAsSb growth rate but that of InAsSb almost retains. This means that the decomposition of TMA is suppressed by the presence of TMSb. It is shown that excess Sb on the growth surface is related to this suppression.

Yokoyama, Haruki; Sugiyama, Hiroki; Oda, Yasuhiro; Sato, Michio; Watanabe, Noriyuki; Kobayashi, Takashi

2004-08-01

263

Growth of GaN nanotubes by halide vapor phase epitaxy.  

PubMed

We have investigated low temperature growth of GaN nanostructures using halide vapor phase epitaxy on c-oriented Al(2)O(3) and Au coated Al(2)O(3) substrates. Depending on the III/V ratio and the growth temperature, the shape and density of the structures could be controlled. By increasing the GaCl partial pressure, the structure changed from dot-like to nanotubes. The nanotubes, which could be open or closed, were about 1 µm long with a diameter of typically 200 nm. In addition, it was observed that the nanostructures were spontaneously nucleated at droplets of Ga or, when using Au coated Al(2)O(3), on droplets of Au/Ga alloy. By varying the growth temperature, the inner diameter of the nanotubes could be controlled. The experimental results suggest that this approach with pre-patterned Au coated Al(2)O(3)substrates has the potential for fabrication of well-organized nanotubes with a high density. PMID:21242622

Hemmingsson, Carl; Pozina, Galia; Khromov, Sergey; Monemar, Bo

2011-01-17

264

Epitaxy of GaN on Si(111) substrate by the hydride vapor phase epitaxy method  

NASA Astrophysics Data System (ADS)

GaN epilayers were grown on Si(111) at 980 °C by a hydride vapor phase epitaxy (HVPE) method. AlxGa1-xN with thickness of ˜900 nm was inserted between Si substrate and GaN epilayer to act as a buffer layer. The investigation of the influence of different V/III ratios on GaN epilayer qualities reveals that high GaCl flow rate can increase the growth rate and improve the surface morphologies of GaN epilayers while high NH3 flow rate is not good for reducing dislocations in GaN epilayers, which can be proved from the analysis of X-ray diffraction rocking curve (XRC), cross-sectional image of scanning electron microscopy (SEM) and image of atomic force microscopy (AFM). Finally, 1.22 ?m GaN epilayer without cracks was successfully obtained with a three-step growth method. The surface roughness average (Ra) was measured to be 1.45 nm and the FWHM of GaN(0002) was 599 arcsec. The measured lattice constants for GaN epilayer were a=3.210 Å and c=5.177 Å, indicating the in-plane tensile stress and out-of-plane compressive stress of GaN epilayer.

Wang, Juan; Ryu, Heui-Bum; Park, Mi-Seon; Lee, Won-Jae; Choi, Young-Jun; Lee, Hae-Yong

2013-05-01

265

Evolutionary phase diagrams for plasma-enhanced chemical vapor deposition of silicon thin films from hydrogen-diluted silane  

SciTech Connect

Real-time optical studies have been applied to develop phase diagrams that characterize plasma-enhanced chemical vapor deposition (PECVD) of silicon thin films at low temperature (200&hthinsp;{degree}C). The deposition phase diagrams describe regimes over which predominantly amorphous and microcrystalline Si phases are obtained as a function of the accumulated thickness and the hydrogen-to-silane gas flow ratio R=[H{sub 2}]/[SiH{sub 4}] in the PECVD process. The diagrams for different substrates provide insights into optimization of amorphous Si materials and solar cells. {copyright} {ital 1999 American Institute of Physics.}

Koh, J.; Ferlauto, A.S.; Rovira, P.I.; Wronski, C.R.; Collins, R.W. [Center for Thin Film Devices and Materials Research Laboratory, The Pennsylvania State University, University Park, Pennsylvania 16802 (United States)

1999-10-01

266

FTIR in situ studies of the gas phase reactions in chemical vapor deposition of SiC  

SciTech Connect

The gas phase during the chemical vapor deposition of silicon carbide from CH{sub 3}SiCl{sub 3} has been investigated by means of FTIR spectroscopy in the in situ conditions. Results show the formation of SiCl{sub 4} and CH{sub 4} molecules which are the transition products in the deposition process, according to earlier suppositions. The gas phase reaction induced by small amounts of HCl (or H{sub 2}O) in the system is an autocatalytic one. The mechanism of surface reactions is proposed. The importance of gas phase analysis in the deposition process is indicated.

Jonas, S.; Ptak, W.S.; Sadowski, W.; Walasek, E. [Univ. of Mining and Metallurgy, Krakow (Poland). Dept. of Ceramics; Paluszkiewicz, C. [Jagiellonian Univ., Krakow (Poland). Regional Lab.

1995-07-01

267

Exchange of Na+ and K+ between water vapor and feldspar phases at high temperature and low vapor pressure  

USGS Publications Warehouse

In order to determine whether gas (steam) containing a small amount of dissolved alkali chloride is effective in promoting base exchange of Na+ and K+ among alkali feldspars and coexisting brine or brine plus solid salt, experiments were carried out at 400-700??C and steam densities ranging down to less than 0.05. For bulk compositions rich in potassium, the low pressure results are close to previous high-pressure results in composition of the fluid and coexisting solid phase. However, when the bulk composition is more sodic, alkali feldspars are relatively richer in potassium at low pressure than at high pressure. This behaviour corresponds to enrichment of potassium in the gas phase relative to coexisting brine and precipitation of solid NaCl when the brine plus gas composition becomes moderately sodic. The gas phase is very effective in promoting base exchange between coexisting alkali feldspars at high temperature and low water pressure. This suggests that those igneous rocks which contain coexisting alkali feldspars out of chemical equilibrium either remained very dry during the high-temperature part of their cooling history or that the pore fluid was a gas containing very little potassium relative to sodium. ?? 1976.

Fournier, R. O.

1976-01-01

268

Models of Gas-phase and Surface Chemistry for Plasma Enhanced Chemical Vapor Deposition  

NASA Astrophysics Data System (ADS)

Plasma enhanced chemical vapor deposition for inter-metal-layer gap-fill processes are increasingly important in semiconductor device manufacture, as the devices include increasing numbers of metal layers with decreasing linewidth and spacing. Optimization of these processes requires knowledge of the microscopic consequences of variations in reactor operating conditions. Topographical simulation can address the gap-fill performance of a depositing film, but the predictive capabiliities are limited by the ability of the model user to accurately supply ion and radical fluxes at a gas/surface interface. Critical to determining this information are the chemical kinetics between gas-phase species and the deposition surfaces. Recent improvements and extensions to the CHEMKIN and Surface CHEMKIN software allow general inclusion of detailed chemical mechanisms in plasma simulations and in models of plasma-surface interactions. In the results presented here (This work represents a collaboration with R. Larson and P. Ho at Sandia, J. Rey and J. Li at TMA, S. M. Han and E. Aydil of UCSB, and S. Huang at Lam Research Corporation), we have used a CHEMKIN-based well mixed reactor model of a high-density SiH_4/O_2/Ar plasma to predict and characterize species fluxes, oxide-deposition rates, and ion-milling rates on a flat surface. These calculated rates can be used as direct input to a topographical simulator. The gas-phase chemistry in the plasma reactor model is comprised of electron impact reactions with silane, oxygen, hydrogen, and argon, as well as neutral radical recombination, abstraction, and oxidation reactions. The surface reaction mechanism contains four classes of reactions: silicon-containing radical deposition, radical abstraction, ion-induced desorption, and physical ion sputtering. We include relative thermochemistry of the surface and gas species to allow reversible reaction dynamics. The plasma model results show good agreement with measured ion densities, as well as with measured net deposition rates.

Meeks, Ellen

1996-10-01

269

Influence Nonuniformity of the Atmospheric Water Vapor Field on the Phase Measurements of Radio Signals from Global Navigation Satellite Systems  

NASA Astrophysics Data System (ADS)

We present the experimental results for the horizontal gradients of integrated content of atmospheric water vapor, which are retrieved from the phase measurements of signals in the receiver network of the global navigation satellite systems in 2011 in the Republic of Tatarstan. The seasonal gradient variation is found. The meridional gradient usually shows a decrease in integrated water vapor with increasing latitude, and its monthly mean values are equal to -1.8 mm and 0.1 mm of precipitable water per 100 km in August and December, respectively. The zonal monthly average gradient is somewhat smaller in magnitude than the meridional one and is equal 0.1 mm and -0.8 mm per 100 km in March/June and May/October, respectively. Instantaneous values of the gradients can by an order of magnitude higher than the monthly mean values. Contribution from the gradient of integral water vapor to the phase-measurement difference between two antennas spaced 30 km apart is shown to attain its maximum of 141.5 mm in August for the zenith angle 80°. Errors in determining the mutual location of the ground-based antennas of global navigation satellite systems due to the water vapor gradients can reach 66 mm and 16.9 mm in August and February, respectively.

Kalinnikov, V. V.; Khutorova, O. G.; Teptin, G. M.

2013-07-01

270

Quasi-equilibrium crystal shapes and kinetic Wulff plots for gallium nitride grown by hydride vapor phase epitaxy  

NASA Astrophysics Data System (ADS)

In this paper we demonstrate work on developing the kinetic Wulff plots and quasi-equilibrium crystal shapes of GaN by hydride vapor phase epitaxy to understand the stable polar, semipolar, and nonpolar planes that emerge naturally from the GaN crystal. High quality bulk m-plane GaN substrates were masked with circular openings to perform selective area growth studies. Growths were performed by hydride vapor phase epitaxy over a range of temperatures, pressures and carrier gases. The quasi-equilibrium crystal shapes were shown to have clear m-plane {11¯00} facets and a sharp and flat (0001¯) N-face or c- face. The (0001) Ga-face or c+ face became faceted with {101¯1} planes emerging with reduced pressures and temperatures. Based on the stable facets, kinetic Wulff plots were constructed.

Bryant, Benjamin N.; Hirai, Asako; Young, Erin C.; Nakamura, Shuji; Speck, James S.

2013-04-01

271

New membrane preconcentration devices for trace vapor detection systems phase 1  

NASA Astrophysics Data System (ADS)

This report describes the results of a six month feasibility program to develop a membrane vapor concentration device. The device would be used to concentrate trace organic vapors in air prior to introduction to a detector instrument. In this way the complexity and cost of the instrumentation required to detect vapors emitted from hidden explosives could be reduced. The membrane concentrator involves the use of ultrathin silicone rubber composite membranes contained in a novel separation cell. Toluene was used as a model organic vapor for explosive vapors. The membrane system was able to obtain enrichments of as much as 50-fold with toluene at pressure ratios of less than 10 across the cell. However, the time to reach this degree of concentration was excessively long at 200 minutes. It appears that large amounts of the organic vapor are sorbed onto and into the membrane and adhesives of the membrane cell. It was not possible to overcome this sorption effect and reduce the system's lag time to a more useful value. Thus, this membrane concentration device does not appear to be a practical preconcentrator for a trace vapor detection instrument.

Armstrong, D.; Baker, R. W.; Mohr, J.

272

Long-lived chemiluminescence in cigarette smoke  

Microsoft Academic Search

Cigarette smoke contains high concentrations of unstable molecules that react with oxygen to produce chemiluminescence. The chemiluminescent activity concentrated in the aerosol phase that can be absorbed on glass-fiber filters and extracted into organic solvents. Cigarette smoke in N,N-dimethylformamide produces a long-lasting luminescence visible to the dark-adapted eye. We have demonstrated the oxygen dependence and have measured the kinetics, activation

H. H. Seliger; W. H. Biggley; J. P. Hamman

1974-01-01

273

Long-Lived Chemiluminescence in Cigarette Smoke  

Microsoft Academic Search

Cigarette smoke contains high concentrations of unstable molecules that react with oxygen to produce chemiluminescence. The chemiluminescent activity is concentrated in the aerosol phase that can be absorbed on glass-fiber filters and extracted into organic solvents. Cigarette smoke in N,N-dimethylformamide produces a long-lasting luminescence visible to the dark-adapted eye. We have demonstrated the oxygen dependence and have measured the kinetics,

H. H. Seliger; W. H. Biggley; J. P. Hamman

1974-01-01

274

Development of Binary Liquid-Vapor Phase Diagram Laboratory Procedures to Replace the Traditional Tetrachloroethylene\\/Cyclohexanone System  

Microsoft Academic Search

Two chemical systems were investigated and implemented as alternatives to the traditional tetrachloroethylene\\/cyclohexanone system used in the binary liquid-vapor phase diagram physical chemistry laboratory. Both the 2-butanone\\/cyclohexane and the ethyl acetate\\/cyclohexane systems reduce the cost of waste disposal and eliminate the use of chlorinated solvents. Student data showed that the azeotropic composition and temperature could be easily identified from a

Kelly J. Gordon; Laura Kenkel; Stephanie Prescia; Marcy Towns

275

Mo¨ssbauer spectroscopy of Sn-doped GaAs grown by metalorganic vapor-phase epitaxy  

Microsoft Academic Search

GaAs epitaxial layers, doped with 119Sn-enriched tin, have been grown by metalorganic vapor-phase epitaxy (MOVPE). 119Sn Mo¨ssbauer spectroscopy and Hall measurements have been used to characterize the layers. Three tin species are observed in the as-grown material. One of these is identified as the SnGa shallow donor site and another is associated with electrically inactive Sn sites that may be

D. L. Williamson; P. Gibart; B. El Jani; K. N’Guessan

1987-01-01

276

Vapor-phase nitration of benzene over solid acid catalysts (1): Nitration with nitric oxide (NO 2)  

Microsoft Academic Search

Vapor-phase nitration of benzene over acidic catalysts is expected to be a clean process with no sulfuric acid waste. We investigated this process over acidic catalysts utilizing nitric oxide (NO2) as a nitrating agent, and found that several mixed metal oxides, such as silica–alumina, zinc-oxide–titania, and tungsten-oxides–molybdenum-oxide, exhibited a fairly good activity. Among them, WO3–MoO3 is the most active, but

H. Sato; K. Hirose

1998-01-01

277

A New Hard Sphere Cubic Equation of State for Predicting Fluids’ Properties and Vapor-Liquid Phase Equilibrium Calculations  

Microsoft Academic Search

In this study, a new cubic hard sphere equation of state (EOS) was developed from standard classical thermodynamics. The new\\u000a equation is applied to calculate properties of fluids and vapor-liquid phase equilibrium calculations. The derived equation\\u000a is a simplified expression of the hard sphere equation which yields satisfactory agreement with the molecular simulation of\\u000a hard molecule data. The EOS is

S. Hajipour; M. Edalat

2008-01-01

278

Vapor pressure and gas phase PVT data and correlation for 1,1,1-trifluoroethane (R143a)  

Microsoft Academic Search

A constant volume apparatus has been used to measure the vapor pressure and single phase densities (PVT) for 1,1,1-trifluoroethane (R143a), an ozone friendly refrigerant. The sample has a purity greater than 99.91% by mass. The measurements were done from 244 to 365 K at pressures up to 4.4 MPa and at densities ranging from 5% to 99% of the critical

G. Giuliani; F. Polonara; S. Kumar; P. Zazzini

1995-01-01

279

Separation of butane and xylene isomers with MFI-type zeolitic membrane synthesized by a vapor-phase transport method  

Microsoft Academic Search

MFI-type zeolitic membranes were prepared by a vapor-phase transport (VPT) method on porous ?-alumina flat disks. Single- and mixed-gas permeation measurements of butane isomers were performed in the temperature range of 300–375K. The separation factor was always greater than the ideal selectivity. This result is explained by the preferential adsorption of n-butane on MFI in the binary system.The pervaporation tests

Takaaki Matsufuji; Norikazu Nishiyama; Masahiko Matsukata; Korekazu Ueyama

2000-01-01

280

Method of varying a characteristic of an optical vertical cavity structure formed by metalorganic vapor phase epitaxy  

DOEpatents

A process for forming an array of vertical cavity optical resonant structures wherein the structures in the array have different detection or emission wavelengths. The process uses selective area growth (SAG) in conjunction with annular masks of differing dimensions to control the thickness and chemical composition of the materials in the optical cavities in conjunction with a metalorganic vapor phase epitaxy (MOVPE) process to build these arrays.

Hou, Hong Q. (Albuquerque, NM); Coltrin, Michael E. (Albuquerque, NM); Choquette, Kent D. (Albuquerque, NM)

2001-01-01

281

Computational prediction of standard gas, liquid, and solid-phase heats of formation and heats of vaporization and sublimation  

Microsoft Academic Search

We present a B3PW91\\/6-31G** computational procedure for predicting standard gas phase heats of formation at 298.15 K by finding DeltaH for the process whereby the molecule is produced from its elements and then adding empirical atomic correction terms. Heats of vaporization and sublimation are estimated on the basis of the calculated electrostatic potential on the molecular surface. These results permit

Peter Politzer; Yuguang Ma; Monica C. Concha

2005-01-01

282

Base catalysis for the synthesis of ?,?-unsaturated ketones from the vapor-phase aldol condensation of acetone  

Microsoft Academic Search

The vapor-phase aldol condensation of acetone was studied over MgO promoted with 0.7–1.0 wt.-% of alkali (Li, Na, K and Cs) or alkaline earth (Ca, Sr and Ba) metal ions. The basic properties of the samples were characterized by chemisorption of carbon dioxide. The basicity of MgO increased on addition of the promoter following the basicity order of the promoter

J. I. Di Cosimo; V. K. Díez; C. R. Apesteguía

1996-01-01

283

Study of vapor liquid two-phase frictional pressure drop in a vertical heated spirally internally ribbed tube  

Microsoft Academic Search

Experiments of vapor liquid two-phase frictional pressure drop of upward flow boiling in a smooth tube and in a spirally internally ribbed tube were conducted, respectively. The spirally internally ribbed tube has an outside diameter of 22mm and an inside diameter of 11mm (an equivalent inside diameter of 11.6mm) and the smooth tube has an outside diameter of 19mm and

Lixin Cheng; Tingkuan Chen

2007-01-01

284

Parameter sensitivity analysis of a high-voltage, vaporization-cooled, three-phase, core-type transformer  

Microsoft Academic Search

This parameter sensitivity analysis considers which independent design parameters have the most influence upon the determination of the weight and volume of a high-voltage, vaporization-cooled, three-phase, core-type transformer. The analysis is conducted through the use of a computer program which given a set of independent design parameters calculates a consistent set of values for the transformer's dependent design parameters. Two

E. L. Dove

1976-01-01

285

Carbon doping of gallium arsenide and reflectance difference spectroscopy of compound semiconductors grown by metalorganic vapor-phase epitaxy  

Microsoft Academic Search

The surface structure and chemistry of compound semiconductors used in heterojunction bipolar transistors was investigated. Lattice-matched, single crystal films of gallium arsenide and indium phosphide were deposited by metalorganic vapor-phase epitaxy in a horizontal-flow, quartz reactor. Two areas of the transistor fabrication process were studied: (1) carbon doping of the gallium arsenide base layer using carbon tetrachloride, and (2) in-situ

Michael John Begarney

2000-01-01

286

Kinetics of carbon tetrachloride decomposition during the metalorganic vapor-phase epitaxy of gallium arsenide and indium arsenide  

Microsoft Academic Search

Carbon tetrachloride is used to dope gallium arsenide and indium–gallium arsenide films with carbon during metalorganic vapor-phase epitaxy (MOVPE). In this study, the decomposition kinetics of CCl4 and of the other precursors (triethylgallium, trimethylindium and tertiarybutylarsine) were determined by monitoring the reactor feed and effluent gases with on-line infrared and mass spectroscopies. As the CCl4 partial pressure was increased from

M. J. Begarney; M. L. Warddrip; M. J. Kappers; R. F. Hicks

1998-01-01

287

Electron Transport in a High Mobility Free-Standing GaN Substrate Grown by Hydride Vapor Phase Epitaxy  

Microsoft Academic Search

We studied electron transport properties in a high quality free-standing GaN grown by hydride vapor phase epitaxy. The GaN, with a thickness of more than 200 mum, was lifted off the sapphire substrate and mechanically polished. At room temperature the carrier density is 1.3x10^16cm-3 and the Hall mobility is 1200 cm^2\\/V-s, which is the highest reported electron mobility for GaN

L. Farina; C. Kurdak; F. Yun; H. Morkoc; D. L. Rode; K. T. Tsen; S. S. Park; K. Y. Lee

2001-01-01

288

Production of nanocrystalline silicon layers using the plasma enhanced chemical vapor deposition from the gas phase of silicon tetrafluoride  

NASA Astrophysics Data System (ADS)

The production of silicon layers using plasma enhanced chemical vapor deposition in the mixture of silicon tetrafluoride and hydrogen is reported. The samples have been analyzed by X-ray diffraction, Raman spectroscopy, and secondary ion mass spectrometry. The phase composition of the layers is nanocrystalline silicon with the crystalline-domain sizes from 3 to 9 nm in dependence of the conditions of the process. The samples are characterized by intense photoluminescence at room temperature.

Sennikov, P. G.; Golubev, S. V.; Shashkin, V. I.; Pryakhin, D. A.; Drozdov, M. N.; Andreev, B. A.; Drozdov, Yu. N.; Kuznetsov, A. S.; Pohl, H.-J.

2009-03-01

289

Production of nanocrystalline silicon layers using the plasma enhanced chemical vapor deposition from the gas phase of silicon tetrafluoride  

Microsoft Academic Search

The production of silicon layers using plasma enhanced chemical vapor deposition in the mixture of silicon tetrafluoride and\\u000a hydrogen is reported. The samples have been analyzed by X-ray diffraction, Raman spectroscopy, and secondary ion mass spectrometry.\\u000a The phase composition of the layers is nanocrystalline silicon with the crystalline-domain sizes from 3 to 9 nm in dependence\\u000a of the conditions of

P. G. Sennikov; S. V. Golubev; V. I. Shashkin; D. A. Pryakhin; M. N. Drozdov; B. A. Andreev; Yu. N. Drozdov; A. S. Kuznetsov; H.-J. Pohl

2009-01-01

290

Comparisons between a gas-phase model of silane chemical vapor deposition and laser-diagnostic measurements  

Microsoft Academic Search

Theoretical modeling and experimental measurements have been used to study gas-phase chemistry in the chemical vapor deposition (CVD) of silicon from silane. Pulsed laser Raman spectroscopy was used to obtain temperature profiles and to obtain absolute density profiles of silane during deposition at atmospheric and 6-Torr total pressures for temperatures ranging from 500 to 800°C. Laser-excited fluorescence was used to

William G. Breiland; Michael E. Coltrin; Pauline Ho

1986-01-01

291

Comparisons between a gas-phase model of silane chemical vapor deposition and laser-diagnostic measurements  

Microsoft Academic Search

Theoretical modeling and experimental measurements have been used to study gas-phase chemistry in the chemical vapor deposition (CVD) of silicon from silane. Pulsed laser Raman spectroscopy was used to obtain temperature profiles and to obtain absolute density profiles of silane during deposition at atmospheric and 6-Torr total pressures for temperatures ranging from 500 to 800 °C. Laser-excited fluorescence was used

William G. Breiland; Michael E. Coltrin; Pauline Ho

1986-01-01

292

Antimicrobial effects of vapor phase thymol, modified atmosphere, and their combination against Salmonella spp. on raw shrimp.  

PubMed

Salmonella contamination on raw shrimp is a big food safety concern in the United States currently. This research evaluated the inhibition effects of vapor phase thymol, modified atmosphere (MA), and their combination against Salmonella spp. on raw shrimp. Growth profiles of a Salmonella spp. cocktail (6 strains), inoculated onto the surface of raw shrimp, treated with vapor phase thymol at 3 levels (0, 0.8, and 1.6 mg/L), or MA (59.5% CO2 + 39.5% N2 + 1% O2 ), both alone and in combination, at 3 temperatures (8, 12, and 16 ºC), were determined. Lag time and maximum growth rate of Salmonella spp. under each treatment were obtained using Baranyi and Roberts models. Results indicated that both vapor phase thymol and MA treatments alone inhibited the growth potential of Salmonella spp. effectively, extending the lag time by 10% to 100% and reducing the maximum growth rate by 14% to 71% compared with controlled samples at experimental temperatures (8, 12, and 16 ºC). Combination treatments of vapor phase thymol and MA exhibited greater inhibition effectiveness than each individual treatment and a synergistic antimicrobial effectiveness could be observed on the lag time extension. To the maximum, at 12 ºC, lag time of Salmonella spp. was extended 59.6% more by the combination treatment of 0.8 mg/L thymol + MA (36.97 h) than those effects combined from 0.8 mg/L thymol treatment and MA treatment alone (23.16 h in total). This combination strategy could be potentially utilized for Salmonella inhibition during the long distance and temperature-abused raw shrimp import process. PMID:23574427

Zhou, Siyuan; Sheen, Shiowshuh; Pang, Yu-Hsin; Liu, LinShu; Yam, Kit L

2013-04-09

293

Material transport regimes and mechanisms for growth of molecular organic thin films using low-pressure organic vapor phase deposition  

Microsoft Academic Search

We determine the physical mechanisms controlling the growth of amorphous organic thin films by the process of low-pressure organic vapor phase deposition (LP-OVPD). In LP-OVPD, multiple host and dopant molecular sources are introduced into a hot wall reactor via several injection barrels using an inert carrier gas, allowing for controlled film growth rates exceeding 10 Å\\/s. The temperature and carrier

Max Shtein; Herman F. Gossenberger; Jay B. Benziger; Stephen R. Forrest

2001-01-01

294

Enhanced vapor-phase processing in fluorinated Fe4 single-molecule magnets.  

PubMed

A new tetrairon(III) single-molecule magnet with enhanced volatility and processability was obtained by partial fluorination of the ancillary ?-diketonato ligands. Fluorinated proligand Hpta = pivaloyltrifluoroacetone was used to assemble the bis(alkoxido)-bridged dimer [Fe2(OEt)2(pta)4] (1) in crystalline form, from which the new tetranuclear complex [Fe4(L)2(pta)6] (2) was synthesized in a one-pot reaction with H3L = 2-hydroxymethyl-2-phenylpropane-1,3-diol, NaOEt, and FeCl3 in a Et2O:EtOH solvent mixture. The structure of compound 2 was inferred from (1)H NMR, mass spectrometry, magnetic measurements, and DFT calculations. Direct current magnetic data are consistent with the expected metal-centered triangular topology for the iron(III) ions, with an antiferromagnetic coupling constant J = 16.20(6) cm(-1) between the central iron and the peripheral ones and consequent stabilization of an S = 5 spin ground state. Alternating current (ac) susceptibility measurements in 0 and 1 kOe static applied fields show the presence of a thermally activated process for magnetic relaxation, with ?0 = 2.3(1) 10(-7) s and U(eff)/kB = 9.9(1) K at zero static field and ?0 = 2.0(2) 10(-7) s and U(eff)/kB = 13.0(2) K at 1 kOe. At a pressure of 10(-7) mbar, compound 2 sublimates at (440 ± 5) K vs (500 ± 10) K for the nonfluorinated variant [Fe4(L)2(dpm)6] (Hdpm = dipivaloylmethane). According to XPS, ToF-SIMS, and ac susceptibility studies, the chemical composition, fragmentation pattern, and slow magnetic relaxation of the pristine material are retained in sublimated samples, suggesting that the molecular structure remains totally unaffected upon vapor-phase processing. PMID:23659465

Rigamonti, Luca; Piccioli, Marco; Malavolti, Luigi; Poggini, Lorenzo; Mannini, Matteo; Totti, Federico; Cortigiani, Brunetto; Magnani, Agnese; Sessoli, Roberta; Cornia, Andrea

2013-05-09

295

Organometallic vapor phase epitaxy growth of upright metamorphic multijunction solar cells  

NASA Astrophysics Data System (ADS)

We demonstrate an integrated metamorphic AlGaInP/AlGaInAs/GaInAs/Ge 4 J solar cell on Ge substrate using organometallic vapor phase epitaxy (OMVPE). A step graded GaInAs buffer was grown right after the Ge subcell was formed to change the lattice constant from that of Ge to that of Ga0.8In0.2As lattice constant followed by a 1.14 eV Ga0.8In0.2As subcell, a 1.5 eV (AlGa)0.8In0.2As subcell, and a 1.85 eV AlxGa0.32-xIn0.68P subcell. Transmission electron microscope (TEM) study shows the threading dislocation density (TDD) is about 6×106 cm-2. The X-ray diffraction reciprocal space map (RSM) shows that the structure is 100% relaxed. Bandgap dependent (AlxGa1-x)0.32In0.68P subcell performance is systematically investigated. As the AlxGa0.32-xIn0.68P cell bandgap goes up to 1.9 eV, the external quantum efficiency (EQE) goes down significantly. Theoretical simulation shows that the decrease of diffusion length causes the lower EQE, which indicates the material quality degrades with the increasing Al content. Integrated 4 J solar cells are fabricated and characterized with spectral response and tested under the AM1.5D terrestrial spectrum at both 1 sun and 2000 suns.

Liu, X. Q.; Fetzer, C. M.; Rehder, E.; Cotal, H.; Mesropian, S.; Law, D.; King, R. R.

2012-08-01

296

Vapor-liquid phase coexistence and transport properties of two-dimensional oligomers.  

PubMed

Grand-canonical transition-matrix Monte Carlo and histogram reweighting techniques are used herein to study the vapor-liquid coexistence properties of two-dimensional (2D) flexible oligomers with varying chain lengths (m = 1-8). The phase diagrams of the various 2D oligomers follow the correspondence state (CS) principle, akin to the behavior observed for bulk oligomers. The 2D critical density is not influenced by the oligomer chain length, which contrasts with the observation for the bulk oligomers. Line tension, calculated using Binder's formalism, in the reduced plot is found to be independent of chain length in contrast to the 3D behavior. The dynamical properties of 2D fluids are evaluated using molecular dynamics simulations, and the velocity and pressure autocorrelation functions are investigated using Green-Kubo (GK) relations to yield the diffusion and viscosity. The viscosity determined from 2D non-equilibrium molecular dynamics simulation is compared with the viscosity estimated from the GK relations. The GK relations prove to be reliable and efficient for the calculation of 2D transport properties. Normal diffusive regions are identified in dense oligomeric fluid systems. The influence of molecular size on the diffusivity and viscosity is found to be diminished at specific CS points for the 2D oligomers considered herein. In contrast, the viscosity and diffusion of the 3D bulk fluid, at a reduced temperature and density, are strongly dependent on the molecular size at the same CS points. Furthermore, the viscosity increases and the diffusion decreases multifold in the 2D system relative to those in the 3D system, at the CS points. PMID:22938253

Patra, Tarak K; Hens, Abhiram; Singh, Jayant K

2012-08-28

297

Recent progress in GaInAsSb thermophotovoltaics grown by organometallic vapor phase epitaxy  

SciTech Connect

Studies on the materials development of Ga{sub 1{minus}x}In{sub x}As{sub y}Sb{sub 1{minus}y} alloys for thermophotovoltaic (TPV) devices are reviewed. Ga{sub 1{minus}x}In{sub x}As{sub y}Sb{sub 1{minus}y} epilayers were grown lattice matched to GaSb substrates by organometallic vapor phase epitaxy (OMVPE) using all organometallic precursors including triethylgallium, trimethylindium, tertiarybutylarsine, and trimethylantimony with diethyltellurium and dimethylzinc as the n- and p-type dopants, respectively. The overall material quality of these alloys depends on growth temperature, In content, V/III ratio, substrate misorientation, and to a lesser extent, growth rate. A mirror-like surface morphology and room temperature photoluminescence (PL) are obtained for GaInAsSb layers with peak emission in the wavelength range between 2 and 2.5 {micro}m. The crystal quality improves for growth temperature decreasing from 575 to 525 C, and with decreasing In content, as based on epilayer surface morphology and low temperature PL spectra. A trend of smaller full width at half-maximum for low temperature PL spectra is observed as the growth rate is increased from 1.5 to 2.5 and 5 {micro}m/h. In general, GaInAsSb layers grown on (100) GaSb substrates with a 6{degree} toward (111)B misorientation exhibited overall better material quality than layers grown on the more standard substrate (100)2{degree} toward (110). Consistent growth of high performance lattice-matched GaInAsSb TPV devices is also demonstrated.

Wang, C.A.; Choi, H.K.; Oakley, D.C. [Massachusetts Inst. of Tech., Lexington, MA (United States). Lincoln Lab.; Charache, G.W. [Lockheed Martin, Inc., Schenectady, NY (United States)

1998-06-01

298

Matrix isolation studies of carbonic acid--the vapor phase above the ?-polymorph.  

PubMed

Twenty years ago two different polymorphs of carbonic acid, ?- and ?-H2CO3, were isolated as thin, crystalline films. They were characterized by infrared and, of late, by Raman spectroscopy. Determination of the crystal structure of these two polymorphs, using cryopowder and thin film X-ray diffraction techniques, has failed so far. Recently, we succeeded in sublimating ?-H2CO3 and trapping the vapor phase in a noble gas matrix, which was analyzed by infrared spectroscopy. In the same way we have now investigated the ?-polymorph. Unlike ?-H2CO3, ?-H2CO3 was regarded to decompose upon sublimation. Still, we have succeeded in isolation of undecomposed carbonic acid in the matrix and recondensation after removal of the matrix here. This possibility of sublimation and recondensation cycles of ?-H2CO3 adds a new aspect to the chemistry of carbonic acid in astrophysical environments, especially because there is a direct way of ?-H2CO3 formation in space, but none for ?-H2CO3. Assignments of the FTIR spectra of the isolated molecules unambiguously reveal two different carbonic acid monomer conformers (C(2v) and C(s)). In contrast to the earlier study on ?-H2CO3, we do not find evidence for centrosymmetric (C(2h)) carbonic acid dimers here. This suggests that two monomers are entropically favored at the sublimation temperature of 250 K for ?-H2CO3, whereas they are not at the sublimation temperature of 210 K for ?-H2CO3. PMID:23631554

Bernard, Jürgen; Huber, Roland G; Liedl, Klaus R; Grothe, Hinrich; Loerting, Thomas

2013-05-14

299

Defects in a-GaN grown on r-sapphire by hydride vapor phase epitaxy  

NASA Astrophysics Data System (ADS)

Non-polar a-GaN films grown on r-sapphire by hydride vapor phase epitaxy (HVPE) are studied using transmission electron microscopy (TEM). Despite the small lattice mismatch in a-GaN ([101\\OverBar 0]˜1.1% and [0 0 0 1] ˜16%), high dislocation and basal stacking fault densities are observed. Epitaxial lateral overgrowth (ELO) technique is implemented in order to reduce the defect density. ELO reduces both densities by two orders of magnitude: the dislocation density is reduced from 1×1010 to 3×108cm-2 and the stacking fault density is reduced from 1×106 to 4×104cm-1. Threading dislocations (TDs) are observed in the ELO mask openings with screw and mixed characters which have Burgers vectors b?=13[112\\OverBar 0] and b?=13[112\\OverBar 3] respectively. In the ELO areas, three kind of dislocations are observed: screw dislocations with b?=13[112\\OverBar 0], edge dislocations with b?=13[2\\OverBar 110] and partial dislocations (PDs) with b?=13[101\\OverBar 0] and b?=16[202\\OverBar 3]. Basal stacking faults (BSFs) of the type I1 (R?=16[202\\OverBar 3]) and I2 (R?=13[101\\OverBar 0]), and prismatic stacking faults (PSFs) with a R?=12[11\\OverBar 01] are also observed. Cathodoluminescence, spectra and imaging, has shown that TDs are non-radiative recombination centers contrary to BSFs.

Arroyo Rojas Dasilva, Y.; Zhu, T.; Martin, D.; Grandjean, N.; Jahn, U.; Stadelmann, P.

2011-07-01

300

Vapor Deposition of Organic Nonlinear Optics Materials. Phase 1 Final Report.  

National Technical Information Service (NTIS)

Thin films of organic materials were deposited by vapor deposition from sublimation sources in vacuum. The materials chosen for study contained functional groups that often lead to large optical nonlinearities and included nitroaniline, catechol, and seve...

J. C. Buchholz J. P. Stec N. A. Kotar

1988-01-01

301

Influence of bond flexibility on the vapor-liquid phase equilibria of water.  

PubMed

The authors performed Gibbs ensemble simulations on the vapor-liquid equilibrium of water to investigate the influence of incorporating intramolecular degrees of freedom in the simple point charge (SPC) water model. Results for vapor pressures, saturation densities, heats of vaporization, and the critical point for two different flexible models are compared with data for the corresponding rigid SPC and SPC/E models. They found that the introduction of internal vibrations, and also their parametrization, has an observable effect on the prediction of the vapor-liquid coexistence curve. The flexible SPC/Fw model, although optimized to describe bulk diffusion and dielectric constants at ambient conditions, gives the best prediction of saturation densities and the critical point of the examined models. PMID:17286493

Raabe, Gabriele; Sadus, Richard J

2007-01-28

302

Sorption Equilibria of Vapor Phase Organic Pollutants on Unsaturated Soils and Soil Minerals.  

National Technical Information Service (NTIS)

Most groundwater pollutants are volatile organic compounds; however, there is relatively little understanding of the sorption reactions that control the transport and fate of organic vapors in the vadose zone. This investigation identified the physical/ch...

J. L. Swager L. W. Lion S. J. Schwager S. K. Ong S. R. Linder

1990-01-01

303

Liquid-Phase Diffusion-Controlled Solute Escape from a Droplet Cooled by Vaporization and Radiation.  

National Technical Information Service (NTIS)

Only a fraction of a volatile solute initially present in a droplet can escape prior to ultimate droplet solidification caused by radiative and vaporization cooling. If the droplet size does not appreciably change during the escape process, the authors sh...

D. E. Rosner

1972-01-01

304

Testing Mixed-Phase Cloud Water Vapor Parameterizations with SHEBA\\/FIRE ACE Observations  

Microsoft Academic Search

The parameterization of in-cloud water vapor pressure below 0°C is examined using in situ aircraft observations from Canadian National Research Council (NRC) Convair-580 flights during the Surface Heat Budget of the Arctic Ocean (SHEBA)\\/First International Satellite Cloud Climatology Project (ISCCP) Regional Experiment Arctic Cloud Experiment (FIRE ACE) campaign. The accuracy of in-cloud water vapor measurements is evaluated against the saturated

Qiang Fu; Shawn Hollars

2004-01-01

305

Evaluation of the potential effects of ingredients added to cigarettes. Part 3: In vitro genotoxicity and cytotoxicity  

Microsoft Academic Search

Cigarette mainstream smoke from blended cigarettes with and without the addition of ingredients was assayed for its cytotoxicity and genotoxicity. In total, 333 ingredients commonly used in cigarette manufacturing were assigned to three different groups. Each group of ingredients was added at a low and a high level to the test cigarettes. The mutagenicity of the particulate phase of the

E. Roemer; F. J. Tewes; T. J. Meisgen; D. J. Veltel; E. L. Carmines

2002-01-01

306

Molecular association of heteronuclear vibrating square-well dumbbells in liquid-vapor phase equilibrium  

NASA Astrophysics Data System (ADS)

Molecular aggregates are formed by heteronuclear vibrating square-well dumbbells. In a recent article [G. A. Chapela and J. Alejandre, J. Chem. Phys., 132(10), 104704 (2010)], it is shown that heteronuclear vibrating square-well dumbbells with a diameter ratio between particles of 1/2 and interacting potential ratio of 4 form micelles of different sizes and shapes which manifest themselves in both the liquid and vapor phases, up to and above the critical point. This means that micellization and phase separation are present simultaneously in this simple model. These systems present a maximum in the critical temperature when plotted against the potential well depth of the second particle ?2. In the same publication, it was speculated that the formation of micelles was responsible for the appearance of the maximum. A thorough study on this phenomena is presented here and it is found that there is a threshold on the size of the second particle and its corresponding depth of interaction potential, where the micelles are formed. If the diameter and well depth of the second particle are small enough for the first and deep enough for the second, micelles are formed. For ?2/?1 between 0.25 and 0.65 and V2/V1 larger than 5.7, micelles are formed up to and above the critical temperature. Outside these ranges micelles appear only at temperatures lower than the critical point. There is a strong temperature dependence on the formation and persistence of the aggregates. For the deepest wells and large enough second particles, a gel interconnected aggregate is obtained. In this work, the micelles are formed at temperatures as low as the triple point and as high as the critical point and, in some cases, persist well above it. The presence of these maxima in critical temperatures Tc when plotted against V2 as follows. At lower values of V2, an increase of Tc is obtained as is expected by the increase of the attractive volume as indicated by the principle of corresponding states. As V2 increases further, the formation of molecular aggregates produce a saturation effect of the deepening of the potential well by encapsulating the particles of the second kind inside the micelles, so the resulting Tc represents a new poly disperse system of molecular aggregates and not the original heteronuclear vibrating square-well dumbbells. The surface tension is also analyzed for these systems, and it is shown that decreases with increasing attraction due to the formation of molecular aggregates.

Chapela, Gustavo A.; de Río, Fernando; Alejandre, José

2011-06-01

307

Pyrolysis-Molecular Weight Chromatography-Vapor-Phase Infrared Spectrophotometry: A New On-Line System for Analysis of Polymers. I. Instrumentation.  

National Technical Information Service (NTIS)

An instrumental system consisting of a combination in series of a programmable pyrolyzer, a thermal conductivity detector, a mass chromatograph, and a fast-scan vapor-phase infrared spectrophotometer is described.

E. Kiran J. K. Gillham

1976-01-01

308

Monomolecular layers and thin films of silane coupling agents by vapor-phase adsorption on oxidized aluminum  

SciTech Connect

Thin films of tetraethoxysilane [TEOS], (3-bromopropyl)trimethoxysilane [BPS], trimethoxyvinylsilane [VS], and 3-(trimethoxysilyl) propyl methacrylate [TPM] on oxidized aluminum surfaces have been investigated by reflection-absorption FTIR spectroscopy, ellipsometry, contact angle, and quartz crystal microbalance (QCM) measurements. Gravimetric measurements with the QCM can reveal quantitative aspects of adsorption and film formation, even for films as thin as monolayers. Adsorption of these silane coupling agents from solution typically produces multilayer films. Vapor-phase adsorption of TEOS and TPM at room temperature results in monomolecular layers. The coupling agents VS and BPS require additional heating after the vapor-phase adsorption to initiate the hydrolysis and condensation reactions necessary for the surface attachment, which produces one to three layers. For vapor adsorbed films a packing density of 4-7 molecules/nm{sup 2} was found. The data strongly suggest that the organic moieties in several of these films have a preferential orientation on the surface; they can be viewed as two-dimensional, oligomeric siloxane networks with oriented organic chains. Subsequent heating of TPM films results in structural rearrangements; heating of TEOS results in complete condensation to SiO{sub 2} films. 43 refs., 6 figs., 4 tabs.

Kurth, D.G.; Bein, T. [Purdue Univ., West Lafayette, IN (United States)

1992-08-06

309

Liquid phase growth of bulk GaSe crystal implemented with the temperature difference method under controlled vapor pressure  

NASA Astrophysics Data System (ADS)

GaSe crystal has been expected as one of the promising nonlinear optical crystals for highly efficient terahertz (THz) wave generation. However there are several reasons why it is difficult to grow the bulk crystals with high quality. To overcome some difficulties, the temperature difference method under controlled vapor pressure (TDM-CVP) is applied for crystal growth. According to this method, stoichiometric composition can be controlled by the application of Se vapor during crystal growth. Crystal growth is carried out at a constant growth temperature without any mechanical disturbance or vibration. It is also noticed that lower temperature growth enables the reduction of point defect concentration in equilibrium. In this article, surface morphology is observed by an optical microscope using the Nomarski interference method. To identify polytypes of grown crystals, backscattered Raman spectra were measured. X-ray diffraction confirmed the polytypes and single crystalline phase. Infrared (?=1 ?m) and terahertz wave (1–3 THz) transmittance measurements were performed to calculate the absorption coefficient in these wavelength regions. From these results, it is shown that the grown crystals have shown ?-type single phase and the absorption coefficients of grown crystals have been improved according to the increase of applied Se vapor pressure during crystal growth.

Onai, Takahide; Nagai, Yuki; Dezaki, Hikari; Oyama, Yutaka

2013-10-01

310

The role of polymer formation during vapor phase lubrication of silicon.  

SciTech Connect

The lubrication of silicon surfaces with alcohol vapors has recently been demonstrated. With a sufficient concentration of pentanol vapor present, sliding of a silica ball on an oxidized silicon wafer can proceed with no measurable wear. The initial results of time-of-flight secondary ion mass spectrometry (ToF-SIMS) analysis of wear surfaces revealed a reaction product having thickness on the order of a monolayer, and with an ion spectrum that included fragments having molecular weights of 200 or more that occurred only inside the wear tracks. The parent alcohol molecule pentanol, has molecular weight of 88amu, suggesting that reactions of adsorbed alcohols on the wearing surfaces allowed polymerization of the alcohols to form higher molecular weight species. In addition to pin-on-disk studies, lubrication of silicon surfaces with pentanol vapors has also been demonstrated using MicroElectroMechanical Systems (MEMS) devices. Recent investigations of the reaction mechanisms of the alcohol molecules with the oxidized silicon surfaces have shown that wearless sliding requires a concentration of the alcohol vapor that is dependent upon the contact stress during sliding, with higher stress requiring a greater concentration of alcohol. Different vapor precursors including those with acid functionality, olefins, and methyl termination also produce polymeric reaction products, and can lubricate the silica surfaces. Doping the operating environment with oxygen was found to quench the formation of the polymeric reaction product, and demonstrates that polymer formation is not necessary for wearless sliding.

Dugger, Michael Thomas; Dirk, Shawn M.; Ohlhausen, James Anthony

2010-10-01

311

A new approach to produce porous silicon powder by chemical attack in phase vapor  

NASA Astrophysics Data System (ADS)

The aim of this work was to investigate a simple and effective method to produce porous silicon from a powder of silicon. The preparation of porous silicon (PS) was realized by exposing silicon powders to acid vapor attack issued from acid solutions containing a 48% of HF and 65% of HNO3. The bond configuration of powder silicon before and after attack with acid vapor was monitored by Fourier transmission infrared spectroscopy (FTIR) and it was found that the PS was produced due to the newly formed Si-H bond during acid vapor attack. From the photoluminescence spectroscopy, it was shown that powder silicon attacked with acid vapor can lead to an increase of photoluminescence (PL) intensity when they are excited by light compared to untreated powder silicon and can provide blue shifts in the PL spectrum by increasing exposing time. This behavior may be attributed to the reduction in the size of the silicon, indicating consequently the formation of PS powder. The experimental results suggest a possibility that the chemical attack with acid vapor of the powder silicon provides a relatively easy way to produce porous silicon.

Khalifa, Marouan; Atyaoui, Malek; Hajji, Messaoud; Ezzaouia, Hatem

2013-03-01

312

Vapor-phase activities of cinnamon, thyme, and oregano essential oils and key constituents against foodborne microorganisms.  

PubMed

The aim of the study presented here was to gain knowledge about the vapor-phase antimicrobial activity of selected essential oils and their major putatively active constituents against a range of foodborne bacterial and fungal strains. In a first step, the vapor-phase antimicrobial activities of three commercially available essential oils (EOs)-cinnamon (Cinnamomum zeylanicum), thyme (Thymus vulgaris), and oregano (Origanum vulgare)-were evaluated against a wide range of microorganisms, including Gram-negative bacteria (Escherichia coli, Yersinia enterocolitica, Pseudomonas aeruginosa, and Salmonella choleraesuis), Gram-positive bacteria (Listeria monocytogenes, Staphylococcus aureus, Bacillus cereus, and Enterococcus faecalis), molds (Penicillium islandicum and Aspergillus flavus), and a yeast (Candida albicans). The minimum inhibitory concentrations (MICs) were generally lower for oregano EO than for the thyme and cinnamon EOs, especially against the relatively resistant Gram-negative. The persistence of the EOs' antimicrobial activities over time was assessed, and changes in the composition of the atmosphere they generated over time were determined using single-drop microextraction (SDME) in combination with gas chromatography-mass spectrometry (GC-MS) and subsequent analysis of the data by principal component analysis (PCA). More relevant chemicals were selected. In addition, the vapor-phase activities of putatively key constituents of the oils were screened against representative Gram-positive (L. monocytogenes) and Gram-negative (S. choleraesuis) bacteria, a mold (A. flavus), and a yeast (C. albicans). Of the tested compounds, cinnamaldehyde, thymol, and carvacrol showed the strongest antimicrobial effectiveness, so their MICs, defined as the minimum vapor concentrations that completely inhibited detectable growth of the microorganisms, were calculated. To check for possible interactions between components present in the EOs, cinnamon EO was fortified with cinnamaldehyde and thyme EO with thymol, and then the antimicrobial activities of the fortified oils were compared to those of the respective unfortified EOs using fractional inhibitory concentration (FIC) indices and by plotting inhibition curves as functions of the vapor-phase concentrations. Synergistic effects were detected for cinnamaldehyde on A. flavus and for thymol on L. monocytogenes, S. choleraesuis, and A. flavus. In all other cases the fortification had additive effects, except for cinnamaldehyde's activity against S. choleraesuis, for which the effect was antagonistic. Finally, various microorganisms were found to cause slight changes over time to the atmospheres generated by all of the EOs (fortified and unfortified) except the fortified cinnamon EO. PMID:17488023

López, Patricia; Sanchez, Cristina; Batlle, Ramón; Nerín, Cristina

2007-05-08

313

Magnetism of cigarette ashes  

NASA Astrophysics Data System (ADS)

Mineral composition of cigarette ashes is well studied in the literature, but no reports are available about the magnetic fraction. Our study presents an investigation of the basic magnetic characteristics of ashes from several commercially available cigarette brands and a wood ash. Magnetic susceptibility, which is a concentration-dependent parameter in case of uniform mineralogy, shows that cigarette ashes contain relatively high amount of magnetic iron minerals, similar to that in wood ash from our study and other literature data. Magnetization data suggest that cigarette ashes contain some 0.1 wt% or lower quantity of magnetite, depending on the brand. Analyses of magnetic mineralogy imply that the main magnetic minerals in ashes from higher quality cigarette brands are magnetite and iron carbide cementite, while in ashes from lower quality brands without additives magnetic minerals are pure and substituted with foreign ions magnetite. Magnetic grain-size analysis shows that cigarette ashes contain significant amount of very fine, nano-meter sized magnetic particles, as well as coarser (up to several microns), magnetically stable grains. Thus, the magnetic study of cigarette ashes proved that these plant ashes possess non-negligible magnetic properties. The results could serve for better elucidation of mineralogy of cigarette ashes as a whole, as well as for future investigation on the presence of magnetic ultra fine particles in cigarette smoke, which may be inhaled in lungs during smoking.

Jordanova, Neli; Jordanova, Diana; Henry, Bernard; Le Goff, Maxime; Dimov, Dimo; Tsacheva, Tsenka

2006-06-01

314

Deep-Ultraviolet Light-Emitting Diodes Fabricated on AlN Substrates Prepared by Hydride Vapor Phase Epitaxy  

NASA Astrophysics Data System (ADS)

AlGaN-based deep-ultraviolet light-emitting diodes (DUV-LEDs) were fabricated on AlN substrates. The AlN substrates were prepared by growing thick hydride vapor phase epitaxy (HVPE)-AlN layers on bulk AlN substrates prepared by physical vapor transport (PVT). After growing an LED structure, the PVT-AlN substrates were removed by mechanical polishing. This process allowed the fabrication of DUV-LEDs on HVPE-AlN substrates with high crystalline quality and DUV optical transparency. The DUV-LEDs exhibited a single emission peaking at 268 nm through the HVPE-AlN substrates. The output power as high as 28 mW was obtained at an injection current of 250 mA.

Kinoshita, Toru; Hironaka, Keiichiro; Obata, Toshiyuki; Nagashima, Toru; Dalmau, Rafael; Schlesser, Raoul; Moody, Baxter; Xie, Jinqiao; Inoue, Shin-ichiro; Kumagai, Yoshinao; Koukitu, Akinori; Sitar, Zlatko

2012-12-01

315

Treatment of Produced Waters Using a Surfactant Modified Zeolite/Vapor Phase Bioreactor System  

SciTech Connect

This report summarizes work performed on this project from October 2004 through March 2005. In previous work, a surfactant modified zeolite (SMZ) was shown to be an effective system for removing BTEX contaminants from produced water. Additional work on this project demonstrated that a compost-based biofilter could biodegrade the BTEX contaminants found in the SMZ regeneration waste gas stream. However, it was also determined that the BTEX concentrations in the waste gas stream varied significantly during the regeneration period and the initial BTEX concentrations were too high for the biofilter to handle effectively. A series of experiments were conducted to determine the feasibility of using a passive adsorption column placed upstream of the biofilter to attenuate the peak gas-phase VOC concentrations delivered to the biofilter during the SMZ regeneration process. In preparation for the field test of the SMZ/VPB treatment system in New Mexico, a pilot-scale SMZ system was also designed and constructed during this reporting period. Finally, a cost and feasibility analysis was also completed. To investigate the merits of the passive buffering system during SMZ regeneration, two adsorbents, SMZ and granular activated carbon (GAC) were investigated in flow-through laboratory-scale columns to determine their capacity to handle steady and unsteady VOC feed conditions. When subjected to a toluene-contaminated air stream, the column containing SMZ reduced the peak inlet 1000 ppmv toluene concentration to 630 ppmv at a 10 second contact time. This level of buffering was insufficient to ensure complete removal in the downstream biofilter and the contact time was longer than desired. For this reason, using SMZ as a passive buffering system for the gas phase contaminants was not pursued further. In contrast to the SMZ results, GAC was found to be an effective adsorbent to handle the peak contaminant concentrations that occur early during the SMZ regeneration process. At a one second residence time, the GAC bed reduced peak contaminant concentrations by 97%. After the initial peak, the inlet VOC concentration in the SMZ regeneration gas stream drops exponentially with time. During this period, the contaminants on the GAC subsequently desorbed at a nearly steady rate over the next 45 hours resulting in a relatively steady effluent concentration of approximately 25 ppm{sub v}. This lower concentration is readily degradable by a downstream vapor phase biofilter (VPB) and the steady nature of the feed stream will prevent the biomass in the VPB from enduring starvation conditions between SMZ regeneration cycles. Repetitive sorption and desorption cycles that would be expected in the field were also investigated. It was determined that although the GAC initially lost some VOC sorption capacity, the adsorption and desorption profiles stabilized after approximately 6 cycles indicating that a GAC bed should be suitable for continuous operation. In preparation for the pilot field testing of the SMZ/VPB system, design, ''in-house'' construction and testing of the field system were completed during this project period. The design of the SMZ system for the pilot test was based on previous investigations by the PI's in Wyoming, 2002 and on analyses of the produced water at the field site in New Mexico. The field tests are scheduled for summer, 2005. A cost survey, feasibility of application and cost analyses were completed to investigate the long term effectiveness of the SMZ/VPB system as a method of treating produced water for re-use. Several factors were investigated, including: current costs to treat and dispose of produced water, end-use water quality requirements, and state and federal permitting requirements.

Soondong Kwon; Elaine B. Darby; Li-Jung Chen; Lynn E. Katz; Kerry A. Kinney; R. S. Bowman; E. J. Sullivan

2005-03-11

316

Hydrogen transport vapor phase epitaxy of CdTe on hybrid substrates for X-ray detector applications  

SciTech Connect

The growth of thick CdTe epitaxial layers by the hydrogen transport vapor phase epitaxy (H{sub 2}T-VPE) method is reported for the first time. The thermodynamics of the H{sub 2} transport method of CdTe is analyzed to determine the equilibrium partial pressures of the molecular species in the vapor and its supersaturation as a function of growth conditions. (100)-oriented CdTe epilayers are successfully grown by H{sub 2}T-VPE on hybrid ZnTe/GaAs(100) substrates prepared by metalorganic vapor phase epitaxy. Growth rates up to 10 {micro}m/h are obtained at temperatures {approximately}760 C and with the CdTe source temperature at 827 C. The achievement of even higher growth rates can be foreseen by using the present method under slightly different conditions; several hundreds micron thick CdTe layers can be thus grown by the H{sub 2}T-VPE. CdTe samples have mirror-like, nearly featureless surfaces. Also, CdTe epilayers have shown a medium-to-high resistivity at room temperature, possibly as a result of compensation by donor impurities diffusing from GaAs. Still the growth of highly resistive layers by in-situ chlorine doping during the H{sub 2}T-VPE growth is possible. In summary, H{sub 2}T-VPE is a potential alternative to traditional melt- and vapor-growth methods for the synthesis of detector-grade CdTe for application to the 1--100 keV x-ray energy range.

Lovergine, N.; Cannoletta, D.; Mancini, A.M. [Univ. di Lecce (Italy); Prete, P.; Cola, A.; Mazzer, M. [Ist. per lo Studio di Nuovi Materiali per l`Elettronica del CNR, Lecce (Italy)

1999-06-01

317

The intractable cigarette ‘filter problem’  

Microsoft Academic Search

BackgroundWhen lung cancer fears emerged in the 1950s, cigarette companies initiated a shift in cigarette design from unfiltered to filtered cigarettes. Both the ineffectiveness of cigarette filters and the tobacco industry's misleading marketing of the benefits of filtered cigarettes have been well documented. However, during the 1950s and 1960s, American cigarette companies spent millions of dollars to solve what the

Bradford Harris

2011-01-01

318

Metalorganic vapor phase epitaxy of II-VI compound semiconductors and diluted magnetic semiconductors  

NASA Astrophysics Data System (ADS)

II-VI compound semiconductors and diluted magnetic semiconductors (DMS) were grown in a vertical stagnation flow MOVPE reactor. The reactor was equipped with a split inlet configuration to inhibit parasitic, gas-phase prereactions. Films of ZnSe and ZnSSe were routinely deposited and characterized by standard techniques. Single-crystal line films were deposited at 666 K and 120 Torr with a growth rate of 4 m m/hr. The sources used for Zn, S, and Se were dimethylzinc triethylamine, hydrogen sulfide, and hydrogen selenide. ZnFeSe was grown for the first time in a MOVPE reactor using iron pentacarbonyl as the Fe source. The bandgap energy and surface roughness of the ZnFeSe films increased with x. ZnFeSe is a DMS with potential application in optical devices such as modulators, isolators, and switches. Doping of ZnSe was attempted using tertiary butylamine (tBNH2) as the doping source. Vapors of tBNH2 were transported to the reactor by flowing hydrogen through a liquid bubbler. Abnormal behavior of the devices constructed from the nitrogen doped ZnSe films was observed. Multilayer structures composed of alternating layers of Fe and ZnSe were investigated. The crystallinity of the structures was dependent on the initial layer. Fe films were deposited on GaAs (100) wafers at 573 K and 666 K. The films deposited at the lower temperature were more uniform. An effort to combine the techniques of evaporation and MOVPE was made. Transition metal elements for which liquid sources were not available were targeted for the purpose of creating novel DMS films. Clustering of the evaporating atoms and desorption of water from the reactor walls lead to the formation and deposition of powders. Experiments were performed to study the thickness uniformity in a multi-aperture reactor. ZnSe was deposited on Si (100) wafers. The resulting thickness variation was measured using the colored fringe patterns exhibited by the interference with light. Thickness uniformity was demonstrated over a 1 cm diameter area using a coaxial split inlet. Experiments indicated the use of a multi-aperture distributor could extend the uniformity over the entire 2" diameter wafer.

Peck, John Douglas, III

319

Organometallic Vapor Phase Epitaxy of Zinc Selenide: Growth and Doping Studies.  

NASA Astrophysics Data System (ADS)

ZnSe at present is the most promising material for the commercial fabrication of blue light emitting devices. The successful fabrication and performance of these blue light emitting devices depends primarily on the structural, optical and electrical properties of the materials used to fabricate them. This study involves the epitaxial growth of ZnSe by organometallic vapor phase epitaxy (OMVPE) and the structural, optical and electrical characterization of undoped and doped ZnSe. The growth of ZnSe was studied over a temperature range of 300^circC-575 ^circC. Very low growth rates were obtained for temperatures below 450^circ C using conventional OMVPE growth techniques. Photo -assisted OMVPE enabled low temperature growth between 300 ^circC-400^ circC. These layers were seen to exhibit superior structural and optical properties over those grown at higher temperatures. P-type doping studies were undertaken using arsine for arsenic doping of ZnSe and a novel precursor, phenylhydrazine (PhHz) for nitrogen doping of ZnSe. Arsenic doped layers did not exhibit p-type characteristics under conventional or photo-assisted growth techniques. Flow modulation growth techniques were also explored. A number of flow profiles of DMZn, DMSe and AsH_3 were used. The use of Cd-As adduct doping was also attempted. All layers were found to be semi-insulating, and As was seen to incorporate as a deep level impurity in ZnSe. Nitrogen (N) doped layers exhibited p-type characteristics only under low temperature photo-assisted growth. These layers were seen to contain N concentrations of more than 5 times 10^{18 } cm^{-3}. A net carrier concentration (N_{rm A}-N_{rm D}) of about 1 to 2 times 10 ^{15} cm^ {-3}, was obtained for layers with a net N concentration of 2.5 times 10 ^{18}/cm^3, using extremely low dopant partial pressures of 10 ^{-8} atm. The partial pressure ratio of PhHz/DMSe ~ 1 times 10^{-4} was used, demonstrating the effectiveness of the new dopant source. Low temperature growth kinetics with the above dopant source were also investigated. The effect of growth temperature and the PhHz flow rate on the growth rate is reported. A possible model for the incorporation of nitrogen is presented.

Akram, Salman

320

Metalorganic vapor-phase epitaxy of indium phosphide and related materials  

NASA Astrophysics Data System (ADS)

The surface chemistry of indium phosphide and related compound semiconductors during metalorganic vapor-phase epitaxy (MOVPE) has been investigated. In particular, the group V precursor chemistry, indium phosphide (001) atomic structure and the InP oxidation process have been examined. The properties of the semiconductors were studied using infrared spectroscopy, molecular cluster calculations, x-ray photoelectron spectroscopy, reflectance difference spectroscopy, x-ray diffraction, and photoluminescence spectroscopy. Indium phosphide, gallium arsenide phosphide, and aluminum indium phosphide have been deposited by MOVPE using tertiarybutylphosphine and tertiarybutylarsine. Minimum incorporation in InP was observed at 565°C and a V/III ratio of 32. In this case, the material contained a background carrier concentration of 2.7 x 1014 cm-3, and the Hall mobilities were 4,970 and 135,000 cm2/V·s at 300 and 77 K. The oxygen contamination in AlInP was found to be only 9.0 x 10 15 cm-3 for deposition at 650°C and a V/III ratio of 35. The relative distribution of arsenic to phosphorus in GaAs yP1-y was determined at temperatures between 525 and 575°C. The distribution coefficient [(NAs/ NP)film/(PTBAs /PTBP)gas] ranged from 25.4 to 8.4, and exhibited an Arrhenius relationship with an apparent activation energy of 1.2 eV. The surface structure of the indium phosphide (001)-(2 x 1) reconstruction has been clarified in this thesis. Infrared spectra collected during atomic deuterium titration of the (2 x 1) surface revealed a sharp P-H stretching mode at 2308 cm-1. Based on theoretical cluster calculations using density functional theory, this mode was due to a single hydrogen atom bonded to one end of a buckled phosphorus dimer. These results confirmed that the (2 x 1) structure was stabilized by hydrogen. Indium phosphide oxidation has been found to be an activated process and strongly structure sensitive. The In-rich (2 x 4) surface reacted with oxygen at 300 K and above. X-ray photoemission spectra revealed that the O 2 dissociatively chemisorbed onto the (2 x 4), inserting into the In-In dimer and In-P back bonds. By contrast, the P-rich (2 x 1) reconstruction did not absorb oxygen up to 5 x 105 L at 300 K. Above 455 K, oxygen reacted with the (2 x 1) inserting preferentially into the In-P back bonds and to a lesser extent into the phosphorus dimer bonds.

Chen, Gangyi

321

27 CFR 41.38 - Cigarettes.  

Code of Federal Regulations, 2013 CFR

...CIGARETTE PAPERS AND TUBES, AND PROCESSED TOBACCO Taxes Classification of Large Cigars and Cigarettes § 41.38 Cigarettes. For internal revenue tax purposes, small cigarettes are designated Class A and large cigarettes are...

2013-04-01

322

Vapor Phase Boric Acid Treatments for Cotton Batting To Meet U.S. Mattress Flammability Standard Ff 4-72  

Microsoft Academic Search

The U.S. Mattress Flammability Standard FF 4-72 imple mented in December 1973 requires that mattresses resist ignition by lighted cigarettes placed on the bare mattress surfaces at specified loca tions, as well as similar tests where the cigarettes are placed between two sheets. This standard, while implying flammability, really measures resist ance of cotton mattresses to the initiation of smoldering

Nestor B. Knoepfler; John P. Madacsi; Julius P. Neumeyer

1976-01-01

323

Smoker preference for "elastic cigarettes" in the Canadian cigarette market.  

PubMed

Elastic cigarettes are characterized by yields of constituents that increase proportionally faster than smoke volume as cigarettes are smoked more intensely. Elasticity may function to overcome physical limitations in increasing puff volume during nicotine-seeking behaviour. The purpose of this study was to determine if there are elastic cigarettes in the Canadian cigarette market and to determine smoker preference for elastic cigarettes. Elasticity was calculated for 115 brands in the Canadian filtered cigarette market for puff volumes of 44 and 56 ml. Puff volumes, nicotine and tar deliveries were obtained from earlier published documents. Sales data were used as a proxy for smoker preference. Ordinary least squares regression was used to determine the association of sales and elasticity in the Canadian cigarette market. The cigarette brands ranged from a mean elasticity value of 1.21 to 0.67. Of the 115 Canadian cigarette brands tested, 23 brands had a mean elasticity value significantly over 1.00, making them elastic. After adjusting for brand, the average elastic cigarette sold an average of 361 million cigarettes while an inelastic cigarette sold 89.5 million cigarettes (p<0.0001). The difference in sales between elastic and inelastic cigarettes was independent of tar yield and filter type. Elasticity was not associated with tar yield (p=0.2734). There are elastic cigarettes in the Canadian cigarette market and the results suggest a possible smoker preference for elastic cigarettes. Utilizing elasticity may be valuable in the development of future harm reduction strategies. PMID:16117842

Chaiton, Michael O; Collinshaw, Neil E; Callard, Aaron J

2005-01-01

324

Vapor-phase microprinting of multicolor phosphorescent organic light emitting device arrays.  

PubMed

Multicolor electrophosphorescent organic light-emitting diode (OLED) pixel patterning by organic vapor jet printing (OVJP) is demonstrated, showing that this technique is capable of rapidly generating high-definition full-color displays. The resolution limits, and means to achieve them are described using a combination of simulation and experimental approaches. PMID:23335090

McGraw, Gregory J; Forrest, Stephen R

2013-01-20

325

Development of novel adsorbents for the control of vapor- phase mercury emissions  

Microsoft Academic Search

Efficient sulfur-impregnated activated carbon-based (SIAC) sorbents for elemental mercury vapors were developed and evaluated in this study. The key parameters of the impregnation protocol included impregnation temperature and initial sulfur to carbon ratio (SCR). Gas constituents and temperature were the key process parameters studied for their impact on sorbent performance. Impregnation temperature is the major impregnation parameter that dominated the

Wei Liu

1998-01-01

326

Improving the energy efficiency of a vapor compression system using a phase change material  

Microsoft Academic Search

When heat transfer between an evaporator and the refrigerated area is unusually low (a typical example is by natural convection) and the vapor compression system is on\\/off regulated, adding a planar PCM to an existing evaporator allows to improve the global efficiency. In this paper, the case of a household refrigerator is simulated as an example. Compared to the classical

K. Azzouz; D. Leducq; J. Guilpart; D Gobin

327

Evaluation of Catalysts from Different Origin for Vapor Phase Upgrading in Biomass Pyrolysis  

SciTech Connect

Liquid fuels and chemicals from biomass resources arouse much interests in research and development. Fast pyrolysis of biomass has the potential to effectively change solid biomass materials into liquid products. However, bio-oil from traditional pyrolysis processes is difficult to apply in industry, because of its complicated composition, high oxygen content, low stability, etc. Upgrading or refining of the bio-oil should be performed for industrial application of biomass pyrolysis. Often, the process would be done in a separate reactor downstream of the pyrolysis process. In this paper, a laboratory scale micro test facility was constructed, wherein the pyrolysis of pine and catalytic upgrading of the resulting vapors were closely coupled in one reactor. The composition of vapor effluent was monitored with a molecular beam mass spectrometer (MBMS) for the online evaluation of the catalyst performance. Catalysts from different origin were tested and compared for the effectiveness of pyrolysis vapor upgrading, namely commercial zeolites, Ni based steam reforming catalyst, CaO, MgO, and several laboratory-made catalysts. The reaction temperature for catalytic upgrading varied between 400 and 600 centigrade, and the gaseous residence time ranged from 0.1 second to above 2 second, to simulate the conditions in industrial application. It is revealed that some catalysts are active in transform most of primary biomass pyrolysis vapors into hydrocarbons, resulting in nonoxygenated products, which is beneficial for downstream utilization. Others are not as effective, results in minor improvement compared with blank test results.

Zhang, X.; Mukarakate, C.; Zheng, Z.; Nimlos, M.

2012-01-01

328

Dry release for surface micromachining with HF vapor-phase etching  

Microsoft Academic Search

A new method for dry etching of silicon dioxide for surface micromachining is presented to obtain very compliant polysilicon microstructures with negligible stiction problem and to greatly simplify the overall releasing procedure as well. By etching the sacrificial silicon dioxide with hydrofluoric acid (HF) vapor instead of conventional aqueous HF solution, the need for subsequent rinsing and an elaborate drying

Yong-Il Lee; K.-H. Park; J. Lee; C.-S. Lee; H. J. Yoo; C.-J. Kim; Y.-S. Yoon

1997-01-01

329

Development of a polysilicon process based on chemical vapor deposition, phase 1  

Microsoft Academic Search

The development of a dichlorosilane-based reductive chemical vapor deposition process for the production of polycrystalline silicon is discussed. Experimental data indicate that the ease of ignition and explosion severity of dichlorosilane (DCS)\\/air mixtures is substantially attenuated if the DCS is diluted with hydrogen. Redesign of the process development unit to accommodate safety related information is described. Several different sources of

J. McCormick; K. Sharp; A. Arvidson; D. Sawyer

1981-01-01

330

Comparative study of electron energy deposition and yields in water in the liquid and vapor phases  

Microsoft Academic Search

Dual sets of Monte Carlo computations were made for electrons in water to assess differences due to the state of condensation. The GSF computer code was used for the vapor and the ORNL code for the liquid. The underlying physical differences specifically incorporated into the liquid code are discussed. At electron energies greater than or equal to 50 eV, ionization

J. E. Turner; H. G. Paretzke; R. N. Hamm; H. A. Wright; R. H. Ritchie

1982-01-01

331

Vapor phase detection of plastic explosives using a SAW resonator immunosensor array  

Microsoft Academic Search

We present the results of a series of experiments demonstrating on-the-spot detection of low vapor pressure plastic explosives containing nitro groups such as RDX, TNT, and their analogous substances, facilitated by the Transportation Security Administration (TSA) Lab. A set of antibody coated SAW resonators inside the flow cell detect the presence of the target molecules diffusing from the sample. Monoclonal

Sang-Hun Lee; D. D. Stubbs; W. D. Hunt; P. J. Edmonson

2005-01-01

332

A Fundamental Study of Vapor Generation from Nonaqeuous Phase Liquid Sources as a Function of Soil Moisture  

NASA Astrophysics Data System (ADS)

The intrusion of vapor phase contaminants from subsurface sources into occupied buildings represents a possible exposure pathway and threat to human health. To make informed risk-management decisions regarding this pathway, it is important to build a conceptual model of the physical and chemical processes that govern vapor intrusion, and specifically to understand the source of the contaminant vapors. One vapor source includes nonaqueous phase liquids (NAPLs) entrapped within the vadose zone. The generation of vapors in the vadose zone from these sources under transient conditions imparted by the heat and water flux boundary conditions at the land surface involves complex mass-transfer processes; partitioning occurs simultaneously between NAPL, air, water and soil phases. Advection and diffusion within the air and water phases also play a critical role. It is our contention that the mass transfer to the air phase is a strong function of the soil moisture conditions in the direct vicinity of the NAPL source. We hypothesize that NAPL sources located in zones of high water saturation will have lower effective mass transfer rates than NAPLs located in low saturation regions, due to the higher diffusion resistance in the aqueous phase. Several studies have investigated NAPL mass transfer under unsaturated conditions and variable soil moisture (Ho and Udell 1992; Wilkins et al. 1995; Yoon et al. 2002); however, to build on this knowledge base, laboratory experimentation is needed under controlled conditions that considers spatially and temporally variable airflow fields and soil moisture saturations that occur in source zones in response to rain events and other climatic phenomena. The fundamental knowledge needed to address field problems cannot be generated in field systems due to lack of control and geologic complexities that are hard to characterize, leading to the need to use intermediate scale test systems. To investigate this problem, experiments were first conducted in a small 2-D porous media tank (28cm x 13cm x 2.5cm) with differing source and soil moisture distributions. Airflow was generated through the tank and the concentrations of the volatile contaminant quantified, allowing estimation of the mass transfer behavior. A mechanistic model was developed simultaneously, and demonstrated that it could represent the data from the experiment. An upscaled experiment was conducted in a large porous media tank (4.9m x 1.2m x 6 cm), to determine if the model can capture the up-scaled system. This intermediate scale tank was subjected to infiltration events and has a complex airflow field more representative of field conditions. The results from the model and the experiment gave an improved understanding of processes that control vapor generation and a better conceptual model for this exposure pathway. This presentation will discuss the results of the intermediate scale tank experiment and associated modeling effort. Ho, C. K. and K. K. Udell (1992). J. Contam. Hydrol. 11(3-4): 291. Wilkins, M. D., L. M. Abriola, et al. (1995). Water Resour. Res. 31(9): 2159-2172. Yoon, H., J. H. Kim, et al. (2002). J. Contam. Hydrol. 54: 1-18.

Petri, B. G.; Illangasekare, T. H.; Sauck, C.; Sakaki, T.; Christ, J.

2011-12-01

333

Carbonaceous resin capsule for vapor-phase monitoring of volatile hydrocarbons in soil: partitioning and kinetic model verification.  

PubMed

The resin capsule system (RCS) was tested as a means of providing data on the presence and forms of volatile hydrocarbons. Results indicated that resin capsules provided data showing sensitivity to soil variables (texture and moisture content) and time. The objectives of this paper are to evaluate the RCS methodology and to determine whether carbonaceous resin capsules provide results that can be described by fundamental chemical partitioning and kinetic principles. Findings revealed a significant relationship between quantities of benzene, toluene, ethylbenzene, and xylene adsorbed on the capsule and quantities partitioned into the vapor phase. Kinetic evaluation indicated that the vapor adsorption by the resin capsule is regulated by diffusion processes. No verification of rate-limiting processes was possible due to limitations imposed by the experimental design, but it appears that during early stages, adsorption rate was limited by vapor diffusion through the soil. The resin capsule data also reflected differences that would be expected due to properties of the organic liquids present. These results provide further evidence that the RCS could be developed to suggest direct in situ monitoring to reveal quantities and nature of organic substances in soils. PMID:23703586

Yang, Jae E; Skogley, Earl O; Ahmad, Mahtab; Lee, Sang Soo; Ok, Yong Sik

2013-05-24

334

Experimental study of arsenic speciation in vapor phase to 500°C: implications for As transport and fractionation in low-density crustal fluids and volcanic gases  

NASA Astrophysics Data System (ADS)

The stoichiometry and stability of arsenic gaseous complexes were determined in the system As-H 2O ± NaCl ± HCl ± H 2S at temperatures up to 500°C and pressures up to 600 bar, from both measurements of As (III) and As (V) vapor-liquid and vapor-solid partitioning, and X-ray absorption fine structure (XAFS) spectroscopic study of As (III)-bearing aqueous fluids. Vapor-aqueous solution partitioning for As (III) was measured from 250 to 450°C at the saturated vapor pressure of the system (P sat) with a special titanium reactor that allows in situ sampling of the vapor phase. The values of partition coefficients for arsenious acid (H 3AsO 3) between an aqueous solution (pure H 2O) and its saturated vapor (K = mAs vapor /mAs liquid) were found to be independent of As (III) solution concentrations (up to ˜1 to 2 mol As/kg) and equal to 0.012 ± 0.003, 0.063 ± 0.023, and 0.145 ± 0.020 at 250, 300, and 350°C, respectively. These results are interpreted by the formation, in the vapor phase, of As(OH) 3(gas), similar to the aqueous As hydroxide complex dominant in the liquid phase. Arsenic chloride or sulfide gaseous complexes were found to be negligible in the presence of HCl or H 2S (up to ˜0.5 mol/kg of vapor). XAFS spectroscopic measurements carried out on As (III)-H 2O (±NaCl) solutions up to 500°C demonstrate that the As(OH) 3 complex dominates As speciation both in dense H 2O-NaCl fluids and low-density supercritical vapor. Vapor-liquid partition coefficients for As (III) measured in the H 2O-NaCl system up to 450°C are consistent with the As speciation derived from these spectroscopic measurements and can be described by a simple relationship as a function of the vapor-to-liquid density ratio and temperature. Arsenic (III) partitioning between vapor and As-concentrated solutions (>2 mol As/kg) or As 2O 3 solid is consistent with the formation, in the vapor phase, of both As 4O 6 and As(OH) 3. Arsenic (V) (arsenic acid, H 3AsO 4) vapor-liquid partitioning at 350°C for dilute aqueous solution was interpreted by the formation of AsO(OH) 3 in the vapor phase. The results obtained were combined with the corresponding properties for the aqueous As(III) hydroxide species to generate As(OH) 3(gas) thermodynamic parameters. Equilibrium calculations carried out by using these data indicate that As(OH) 3(gas) is by far the most dominant As complex in both volcanic gases and boiling hydrothermal systems. This species is likely to be responsible for the preferential partition of arsenic into the vapor phase as observed in fluid inclusions from high-temperature (400 to 700°C) Au-Cu (-Sn, -W) magmatic-hydrothermal ore deposits. The results of this study imply that hydrolysis and hydration could be also important for other metals and metalloids in the H 2O-vapor phase. These processes should be taken into account to accurately model element fractionation and chemical equilibria during magma degassing and fluid boiling.

Pokrovski, Gleb S.; Zakirov, Ildar V.; Roux, Jacques; Testemale, Denis; Hazemann, Jean-Louis; Bychkov, Andrew Y. u.; Golikova, Galina V.

2002-10-01

335

Metalorganic vapor-phase epitaxial growth of HgCdTe device heterostructures on three-inch-diameter substrates  

Microsoft Academic Search

A new metal-organic vapor-phase epitaxial (MOVPE) reactor-cell design has been developed to grow on 3-in.-diameter substrates.\\u000a This was required to produce uniform, fully doped heterostructures needed for array producibility and wafer-scale processing\\u000a compatibility. The reactor has demonstrated epitaxial growth of HgCdTe (MCT) with good morphology onto both GaAs and GaAs\\u000a on Si wafers. The density of surface-growth defects, typical of

C. D. Maxey; J. P. Camplin; I. T. Guilfoy; J. Gardner; R. A. Lockett; C. L. Jones; P. Capper; M. Houlton; N. T. Gordon

2003-01-01

336

Numerical analysis of vapor-liquid two-phase system based on the Enskog-Vlasov equation  

NASA Astrophysics Data System (ADS)

In this study, equilibrium and nonequilibrium numerical simulations for vapor-liquid two-phase systems were performed by using the Enskog-Vlasov equation. The kinetic boundary condition (KBC) at the interface was investigated. The simulation results showed that at a low or slightly high liquid temperature, the velocity distribution of the KBC obtained by our simulation is anisotropic Gaussian; this result agrees qualitatively with the results of the MD simulation performed by Ishiyama et al. (PRL, 2005). Also, the nonequilibrium nature of KBC becomes larger with the increase of liquid temperature.

Kobayashi, Kazumichi; Ohashi, Kotaro; Watanabe, Masao

2012-11-01

337

Crystalline CrV 1? x P x O 4 catalysts for the vapor-phase oxidation of 3-picoline  

Microsoft Academic Search

The heterogeneously catalyzed vapor-phase oxidation of 3-picoline to nicotinic acid over a series of mixed oxides, CrV1?xPxO4, was investigated at 300–400°C. Characterizations of the catalysts were carried out using X-ray diffraction, FT-IR, TG-DTA, BET, NH3-TPD, TPR, and pyridine adsorption diffuse reflectance infrared Fourier-transform spectra (DRIFTS). The mixed oxides, CrV1?xPxO4 (x= 0–1.0), were precipitated by adjusting the pH from an aqueous

Zhaoxia Song; Toshiyuki Matsushita; Tetsuya Shishido; Katsuomi Takehira

2003-01-01

338

Vapor-Phase Epoxidation of Propene Using H 2 and O 2 over Au\\/Ti–MCM-48  

Microsoft Academic Search

Vapor-phase epoxidation of propene using H2 and O2 over homogeneously dispersed gold particles deposited by a deposition–precipitation (DP) method on the supports Ti–MCM-41 (hexagonal) and Ti–MCM-48 (cubic) is studied at a space velocity of 4000 h?1·cm?3\\/g(cat.) and at reaction temperature of 100 or 150°C. Influences of the various parameters investigated in the case of Ti–MCM-48 support are Si\\/Ti (30, 50,

B. S. Uphade; T. Akita; T. Nakamura; M. Haruta

2002-01-01

339

Characterization of InGaAs/GaAs(001) films grown by metalorganic vapor phase epitaxy using alternative sources  

NASA Astrophysics Data System (ADS)

Thin films of InxGa1-xAs (0vapor phase epitaxy using triisopropylindium, triisobutylgallium, and tertiarybutylarsine. The effect of the process conditions, temperature, and V/III ratio on the film quality was studied using high resolution x-ray diffraction, scanning tunneling microscopy, and Hall measurements. High quality films were grown at temperatures as low as 475 °C and at a V/III ratio of 100. However, under these conditions, a change in growth mode from step flow to two-dimensional nucleation was observed.

Han, B. K.; Li, L.; Kappers, M. J.; Hicks, R. F.; Yoon, H.; Goorsky, M. S.; Higa, K. T.

1998-02-01

340

A GaAs metalorganic vapor phase epitaxy growth process to reduce Ge outdiffusion from the Ge substrate  

SciTech Connect

A barrier based on GaAs for controlling the Ge out diffusion has been developed by metalorganic vapor phase epitaxy. It is based on a thin GaAs layer (50 nm) grown at a low temperature ({approx_equal}500 deg. C) on top of a predeposition layer, showing that GaAs prevents the Ge diffusing when it is grown at a low temperature. Additionally, two different predeposition monolayers have been compared, concluding that when the Ga is deposited first, the diffusions across the GaAs/Ge heterointerface decrease.

Galiana, B.; Rey-Stolle, I.; Algora, C. [Instituto de Energia Solar-UPM, ETSI de Telecomunicacion, Avda. Complutense s/n, Madrid 28040 (Spain); Volz, K.; Stolz, W. [Material Sciences Center (WZMW), Philipps University of Marburg, Marburg 35032 (Germany)

2008-04-14

341

Dislocation reduction of InAs nanofins prepared on Si substrate using metal-organic vapor-phase epitaxy  

PubMed Central

InAs nanofins were prepared on a nanopatterned Si (001) substrate by metal-organic vapor-phase epitaxy. The threading dislocations, stacked on the lowest-energy-facet plane {111}, move along the SiO2 walls, resulting in a dislocation reduction, as confirmed by transmission electron microscopy. The dislocations were trapped within a thin InAs epilayer. The obtained 90-nm-wide InAs nanofins with an almost etching-pit-free surface do not require complex intermediate-layer epitaxial growth processes and large thickness typically required for conventional epitaxial growth.

2012-01-01

342

Ammonia: A source of hydrogen dopant for InN layers grown by metal organic vapor phase epitaxy  

NASA Astrophysics Data System (ADS)

Thermal annealing of InN layers grown by metal organic vapor phase epitaxy (MOVPE) is investigated in nitrogen atmosphere for temperatures ranging from 400 to 550 °C and for heat treatment times up to 12 h. This treatment results in hydrogen outdiffusion, lowering significantly the residual n-type background doping. This mechanism is shown to be reversible through thermal annealing under ammonia atmosphere, responsible of hydrogen incorporation during growth. These results establish a MOVPE process allowing the obtention of InN samples, which exhibit similar electrical properties than molecular beam epitaxy grown samples: a key issue in view of future industrial production of InN based devices.

Ruffenach, S.; Moret, M.; Briot, O.; Gil, B.

2009-07-01

343

A GaAs metalorganic vapor phase epitaxy growth process to reduce Ge outdiffusion from the Ge substrate  

NASA Astrophysics Data System (ADS)

A barrier based on GaAs for controlling the Ge out diffusion has been developed by metalorganic vapor phase epitaxy. It is based on a thin GaAs layer (50 nm) grown at a low temperature (~500 °C) on top of a predeposition layer, showing that GaAs prevents the Ge diffusing when it is grown at a low temperature. Additionally, two different predeposition monolayers have been compared, concluding that when the Ga is deposited first, the diffusions across the GaAs/Ge heterointerface decrease.

Galiana, B.; Rey-Stolle, I.; Algora, C.; Volz, K.; Stolz, W.

2008-04-01

344

Bubbles in liquids with phase transition—part 2: on balance laws for mixture theories of disperse vapor bubbles in liquid with phase change  

NASA Astrophysics Data System (ADS)

We study averaging methods for the derivation of mixture equations for disperse vapor bubbles in liquids. The carrier liquid is modeled as a continuum, whereas simplified assumptions are made for the disperse bubble phase. An approach due to Petrov and Voinov is extended to derive mixture equations for the case that there is a phase transition between the carrier liquid and the vapor bubbles in water. We end up with a system of balance laws for a multi-phase mixture, which is completely in divergence form. Additional non-differential source terms describe the exchange of mass, momentum and energy between the phases. The sources depend explicitly on evolution laws for the total mass, the radius and the temperature of single bubbles. These evolution laws are derived in a prior article (Dreyer et al. in Cont Mech Thermodyn. doi: 10.1007/s00161-0225-6 , 2011) and are used to close the system. Finally, numerical examples are presented.

Dreyer, Wolfgang; Hantke, Maren; Warnecke, Gerald

2013-08-01

345

Threading dislocations in gallium nitride epilayers grown by metalorganic vapor phase epitaxy  

NASA Astrophysics Data System (ADS)

Gallium nitride (GaN) epitaxial layers were deposited by metalorganic vapor phase epitaxy on (0001) sapphire. A new approach involving silicon nitride (Si3N4) interlayers deposited on as-grown nucleation layers (NLs) was demonstrated for reducing the density of threading dislocations (TDs). By inserting the Si3N4 interlayer, the metamorphosis of the NL upon thermal annealing was significantly changed as compared to that without the Si3N4 interlayer. Surface roughening upon thermal annealing produced a small number of protrusions from the NLs breaking through the Si3N4 interlayer. Initial GaN overgrowth could then be confined to the exposed protrusions, ensuring a selective area growth mode similar to the epitaxial lateral overgrowth (ELOG) technique. This new technique is referred to as "in situ patterning ELOG". The TD density has been reduced by one to two orders of magnitude as compared to the two-step growth. The improvement of crystal quality was also confirmed by X-ray diffraction and photoluminescence measurements. A comprehensive investigation of morphology and microstructure evolution in GaN NLs and early stage GaN overgrowths was carried out in order to understand the mechanisms of generation and reduction of TDs. Annealed NLs in Si 3N4/GaN NL composites consist of discrete grains with very high density of basal plane stacking faults. The majority of edge dislocations (Burgers vector 1/3<11--20>) emerging from the exposed regions can be generated by reactions in which a Shockley partial dislocation bounding a stacking fault creates a perfect dislocation and another Shockley partial dislocation. These perfect dislocations can bend to form vertical dislocations (VDs) when vertical growth dominates then bend back to from horizontal dislocations (HDs) once lateral overgrowth dominates. Dislocation bending occurs as a result of glide and climb in the presence of stresses and point defects during the early stage of high temperature overgrowth. A significant portion of VDs with opposite Burgers vectors close on themselves by forming dislocation half-loops. During the initial 500nm overgrowth, most VDs are edge-type and bend to form HDs owing to strong stresses induced by enhanced lateral overgrowth. Most HDs terminate at micro-voids which formed near the interface during the early stage of overgrowth by a mechanism similar to ELOG. Wing-twist/tilt does not introduce subgram boundaries between initial growth patches due to early coalescence in this new technique. The screw component (Burgers vector component in <0001>) can be introduced in several ways: by direct propagation of dislocations that exist in NL grains, as a result of strain induced due to surface roughness or by coalescence of Frank partial dislocations in the basal planes.

Fang, Xiaolong

346

Vapor-liquid phase equilibria of water modelled by a Kim-Gordon potential  

SciTech Connect

Gibbs ensemble Monte Carlo simulations were carried out to investigate the properties of a frozen-electron-density (or Kim-Gordon, KG) model of water along the vapor-liquid coexistence curve. Because of its theoretical basis, such a KG model provides for seamless coupling to Kohn-Sham density functional theory for use in mixed quantum mechanics/molecular mechanics (QM/MM) implementations. The Gibbs ensemble simulations indicate rather limited transferability of such a simple KG model to other state points. Specifically, a KG model that was parameterized by Barker and Sprik to the properties of liquid water at 300 K, yields saturated vapor pressures and a critical temperature that are significantly under- and over-estimated, respectively.

Maerzke, K A; McGrath, M J; Kuo, I W; Tabacchi, G; Siepmann, J I; Mundy, C J

2009-03-16

347

Thin film solid-state lithium batteries prepared by consecutive vapor-phase processes  

Microsoft Academic Search

Thin-film solid-state lithium batteries of total thickness less than 20 microns were prepared. These thin lithium batteries were fabricated using a thin film of TiS2 prepared by chemical vapor deposition (CVD) as the cathode active material, a thin film of solid polymer prepared by plasma polymerization as the electrolyte, and a thin film of lithium deposited by thermal evaporation as

Zen-Ichiro Takehara; Zempachi Ogumi; Yoshiharu Uchimoto; Eishi Endo; Yoshinori Kanamori

1991-01-01

348

Models of Gas-phase and Surface Chemistry for Plasma Enhanced Chemical Vapor Deposition  

Microsoft Academic Search

Plasma enhanced chemical vapor deposition for inter-metal-layer gap-fill processes are increasingly important in semiconductor device manufacture, as the devices include increasing numbers of metal layers with decreasing linewidth and spacing. Optimization of these processes requires knowledge of the microscopic consequences of variations in reactor operating conditions. Topographical simulation can address the gap-fill performance of a depositing film, but the predictive

Ellen Meeks

1996-01-01

349

Phase Equilibria and Reactive Chemical Vapor Deposition (RCVD) of Ti 3 SiC 2  

Microsoft Academic Search

The present article addresses the issue of properly modelling the thermodynamic aspect of chemical reactions proceeding at\\u000a the solid\\/gas interface in a multi-component system. Attention is more especially paid to the formation of Ti3SiC2 by reactive chemical vapor deposition (RCVD) on a silicon carbide substrate heated at 1100 °C. A deposition diagram has been\\u000a calculated by Gibbs free energy minimization in

H. Fakih; S. Jacques; O. Dezellus; M. P. Berthet; F. Bosselet; M. Sacerdote-Peronnet; J. C. Viala

2008-01-01

350

Characterization of single-crystal diamond grown from the vapor phase on substrates of natural diamond  

SciTech Connect

The results of studies of single-crystal diamond layers with orientation (100) grown on substrates of IIa-type natural diamond by chemical-vapor deposition and of semiconductor diamond obtained subsequently by doping by implantation of boron ions are reported. Optimal conditions of postimplantation annealing of diamond that provide the hole mobility of 1150 cm{sup 2} V{sup -1} s{sup -1} (the highest mobility obtained so far for semiconductor diamond after ion implantation) are given.

Altukhov, A. A. [ITC UralAlmazInvest (Russian Federation); Vikharev, A. L.; Gorbachev, A. M. [Russian Academy of Sciences, Institute of Applied Physics (Russian Federation); Dukhnovsky, M. P.; Zemlyakov, V. E. [FSUE Istok (Russian Federation); Ziablyuk, K. N.; Mitenkin, A. V. [ITC UralAlmazInvest (Russian Federation); Muchnikov, A. B., E-mail: mabl@appl.sci-nnov.ru; Radishev, D. B. [Russian Academy of Sciences, Institute of Applied Physics (Russian Federation); Ratnikova, A. K.; Fedorov, Yu. Yu. [FSUE Istok (Russian Federation)

2011-03-15

351

Toward a Monte Carlo program for simulating vapor-liquid phase equilibria from first principles  

SciTech Connect

Efficient Monte Carlo algorithms are combined with the Quickstep energy routines of CP2K to develop a program that allows for Monte Carlo simulations in the canonical, isobaric-isothermal, and Gibbs ensembles using a first principles description of the physical system. Configurational-bias Monte Carlo techniques and pre-biasing using an inexpensive approximate potential are employed to increase the sampling efficiency and to reduce the frequency of expensive ab initio energy evaluations. The new Monte Carlo program has been validated through extensive comparison with molecular dynamics simulations using the programs CPMD and CP2K. Preliminary results for the vapor-liquid coexistence properties (T = 473 K) of water using the Becke-Lee-Yang-Parr exchange and correlation energy functionals, a triple-zeta valence basis set augmented with two sets of d-type or p-type polarization functions, and Goedecker-Teter-Hutter pseudopotentials are presented. The preliminary results indicate that this description of water leads to an underestimation of the saturated liquid density and heat of vaporization and, correspondingly, an overestimation of the saturated vapor pressure.

McGrath, M; Siepmann, J I; Kuo, I W; Mundy, C J; Vandevondele, J; Sprik, M; Hutter, J; Mohamed, F; Krack, M; Parrinello, M

2004-10-20

352

Cigarette tax avoidance and evasion  

Microsoft Academic Search

Variation in state cigarette taxes provides incentives for tax avoidance through smuggling, legal border crossing to low tax jurisdictions, or Internet purchasing. When taxes rise, tax paid sales of cigarettes will decline both because consumption will decrease and because tax avoidance will increase. The key innovation of this paper is to compare cigarette sales data to cigarette consumption data from

Mark Stehr

2005-01-01

353

Evaluation of preservative engine oil containing vapor-phase corrosion inhibitor and a simplified engine-preservation technique. Interim report, Jul 85Sep 90  

Microsoft Academic Search

The objectives of this project were: (1) to determine the feasibility of adding a vapor-phase corrosion inhibitor (VCI) component to improve the preservation performance of MIL-L-21260 and (2) to evaluate a less complicated engine preservation procedure. A simultaneous two-phase approach was conducted. Phase 1 involved the formulation and evaluation of experimental VCI oils, while Phase 2 was the evaluation of

1990-01-01

354

History of Bhutan's prohibition of cigarettes: Implications for neo-prohibitionists and their critics  

Microsoft Academic Search

BackgroundRecently, cigarette neo-prohibitionists have argued that a cigarette ban can be obtained from a de-facto phase-out of cigarettes based on a combination of effective anti-tobacco regulations and high taxes in conjunction with aggressive application of nicotine replacement therapies. The purpose of this study was to ascertain whether these claims were valid in Bhutan, which enacted a national cigarette sales prohibition

Michael S. Givel

2011-01-01

355

Vapor-phase and particulate-associated pesticides and PCB concentrations in eastern North Dakota air samples  

SciTech Connect

Vapor-phase and suspended particulate (<50 {mu}m) samples were collected on polyurethane foam (PUF) and quartz fiber filters in rural North Dakota to determine the air concentrations of pesticides in an area where agriculture is a primary source of semivolatile pollutants. Samples were collected at two sites from 1992 to 1994 that were at least 0.4 km from the nearest farmed fields and known application of pesticides, and analyzed for 22 different organochlorine, triazine, and acid herbicide pesticides. Fourteen pesticides were found above the detection limits (typically <1 pg/m{sup 3}). Concentrations of polychlorinated biphenyl (PCB) congeners were much lower (<50 pg/m{sup 3} in all cases) than many of the pesticides. These results demonstrate that pesticides are among the most prevalent chlorinated semivolatile pollutants present in rural North Dakota, that significant transport of pesticides occurs both in the vapor-phase and on suspended particulate matter, and that blown soil may be a significant mechanism for introducing pesticides into surface and ground waters. 32 refs., 2 figs., 4 tabs.

Hawthorne, S.B.; Miller, D.J.; Louie, P.K.K. [Univ. of North Dakota, Grand Forks, ND (United States)] [and others

1996-05-01

356

Investigation of cracks in GaN films grown by combined hydride and metal organic vapor-phase epitaxial method  

PubMed Central

Cracks appeared in GaN epitaxial layers which were grown by a novel method combining metal organic vapor-phase epitaxy (MOCVD) and hydride vapor-phase epitaxy (HVPE) in one chamber. The origin of cracks in a 22-?m thick GaN film was fully investigated by high-resolution X-ray diffraction (XRD), micro-Raman spectra, and scanning electron microscopy (SEM). Many cracks under the surface were first observed by SEM after etching for 10 min. By investigating the cross section of the sample with high-resolution micro-Raman spectra, the distribution of the stress along the depth was determined. From the interface of the film/substrate to the top surface of the film, several turnings were found. A large compressive stress existed at the interface. The stress went down as the detecting area was moved up from the interface to the overlayer, and it was maintained at a large value for a long depth area. Then it went down again, and it finally increased near the top surface. The cross-section of the film was observed after cleaving and etching for 2 min. It was found that the crystal quality of the healed part was nearly the same as the uncracked region. This indicated that cracking occurred in the growth, when the tensile stress accumulated and reached the critical value. Moreover, the cracks would heal because of high lateral growth rate.

2011-01-01

357

Phase transitions in the liquid-vapor interface of dilute alloys of Bi in Ga: New experimental studies  

NASA Astrophysics Data System (ADS)

We report the results of measurements of x-ray reflectivity and grazing incidence x-ray diffraction from the liquid-vapor interfaces of four dilute alloys of Bi in Ga with mole fractions xBi=0.0032, 0.0023, 0.000 37, and 0.000 037. The monolayer coverage of the alloys with xBi=0.0023, and xBi=0.000 37 is about 0.85 and only very slightly temperature dependent. The monolayer coverage in the lowest-concentration alloy, with xBi=0.000 037, ranged from 0.82 at 29 °C to 0.58 at 110 °C. In none of these alloys, down to the lowest temperature used, 29 °C, can we find any evidence for crystallization of the Bi monolayer that segregates as the outermost stratum of the liquid-vapor interface. Drawing on theoretical arguments we propose that the transitions inferred from the second-harmonic generation and plasma generation studies of dilute Bi in Ga alloys are from the liquid state to the hexatic state of the Bi monolayer. The data for the alloy with xBi=0.000 037 suggest that near 80 °C there is a disordered phase-to-disordered phase transition.

Li, Dongxu; Jiang, Xu; Yang, Bin; Rice, Stuart A.

2005-06-01

358

Phase transitions in the liquid-vapor interface of dilute alloys of Bi in Ga: New experimental studies  

SciTech Connect

We report the results of measurements of x-ray reflectivity and grazing incidence x-ray diffraction from the liquid-vapor interfaces of four dilute alloys of Bi in Ga with mole fractions x{sub Bi} = 0.0032, 0.0023, 0.00037, and 0.000037. The monolayer coverage of the alloys with x{sub Bi} = 0.0023, and x{sub Bi} = 0.00037 is about 0.85 and only very slightly temperature dependent. The monolayer coverage in the lowest-concentration alloy, with x{sub Bi} = 0.000037, ranged from 0.82 at 29 C to 0.58 at 110 C. In none of these alloys, down to the lowest temperature used, 29 C, can we find any evidence for crystallization of the Bi monolayer that segregates as the outermost stratum of the liquid-vapor interface. Drawing on theoretical arguments we propose that the transitions inferred from the second-harmonic generation and plasma generation studies of dilute Bi in Ga alloys are from the liquid state to the hexatic state of the Bi monolayer. The data for the alloy with x{sub Bi} = 0.000037 suggest that near 80 C there is a disordered phase-to-disordered phase transition.

Li, Dongxu; Jiang, Xu; Yang, Bin; Rice, Stuart A. (UC)

2010-07-19

359

Detection of liquid–vapor–solid triple contact line in two-phase heat transfer phenomena using high-speed infrared thermometry  

Microsoft Academic Search

Heat transfer in complex physical situations such as nucleate boiling, quenching and dropwise condensation is strongly affected by the presence of a liquid–vapor–solid triple contact line, where intense energy transfer and phase change occur. A novel experimental technique for the detection of the liquid–vapor–solid line in these situations is presented. The technique is based on high-speed infrared (IR) thermometry through

Hyungdae Kim; Jacopo Buongiorno

2011-01-01

360

Synthesis of ultrafine particles of intermetallic compounds by the vapor-phase magnesium reduction of chloride mixtures: Part I. Titanium aluminides  

Microsoft Academic Search

A new chemical synthesis process for the preparation of intermetallic compounds has been developed. It involves the vapor-phase\\u000a reduction of mixtures of constituent metal chlorides by magnesium vapor to produce intermetallic compounds in the form of\\u000a fine powder. The advantages of the process include (a) the use of inexpensive raw materials, (b) low reaction temperatures,\\u000a and (c) products in the

H. Y. Sohn; S. Paldey

1998-01-01

361

Synthesis of ultrafine particles of intermetallic compounds by the vapor-phase magnesium reduction of chloride mixtures: Part II. Nickel aluminides  

Microsoft Academic Search

The new chemical synthesis process developed in this laboratory for the preparation of the fine powders of intermetallic compounds\\u000a by the vapor-phase reduction of mixtures of constituent metal chlorides by magnesium vapor, described in Part I for titanium\\u000a aluminides, was applied to the synthesis of nickel aluminide particles. NiAl, NiAl3, and Ni2Al3 were formed by reducing mixtures of NiCl2 and

H. Y. Sohn; S. Paldey

1998-01-01

362

Vapor-phase hydrothermal transformation of HTiOF3 intermediates into {001} faceted anatase single-crystalline nanosheets.  

PubMed

For the first time, a facile, one-pot hydrofluoric acid vapor-phase hydrothermal (HF-VPH) method is demonstrated to directly grow single-crystalline anatase TiO(2) nanosheets with 98.2% of exposed {001} faceted surfaces on the Ti substrate via a distinctive two-stage formation mechanism. The first stage produces a new intermediate crystal (orthorhombic HTiOF(3) ) that is transformed into anatase TiO(2) nanosheets during the second stage. The findings reveal that the HF-VPH reaction environment is unique and differs remarkably from that of liquid-phase hydrothermal processes. The uniqueness of the HF-VPH conditions can be readily used to effectively control the nanostructure growth. PMID:22903795

Liu, Porun; Wang, Yun; Zhang, Haimin; An, Taicheng; Yang, Huagui; Tang, Zhiyong; Cai, Weiping; Zhao, Huijun

2012-08-20

363

Chemical analysis of cigarette smoke particulate generated in the MSB-01 in vitro whole smoke exposure system.  

PubMed

Cigarette mainstream smoke (MS) is a dynamic aerosol consisting of a gas-vapor phase and a particulate phase. In recent years, novel in vitro whole smoke exposure systems have been developed to expose cells directly to whole MS. One such system is the Burghart Mimic Smoker-01 (MSB-01). Our previous data using the MSB-01 indicated that a 50 +/- 10% loss of particulate matter occurred prior to MS delivery into the exposure chamber. Additionally, a change in aerosol particle diameter was also measured, suggesting that the chemical composition of MS might be changing within the system. In this study, we have expanded on our previous work and compared the particulate phase chemical composition of undiluted and diluted MS generated by the instrument and that of the MS delivered into the exposure chamber. The average percent delivery of cigarette smoke condensate (CSC) detected for all the measured chemical constituents was 35 +/- 13% for undiluted MS and 23 +/- 8% for 1:1 diluted MS. The data also indicate that under our experimental conditions, incomplete mixing of the freshly generated MS occurs during its dilution by the system. Taken together, the data presented here show that significant chemical changes occur between the generation of MS by the system and its delivery into the exposure chamber. This indicates that due to the dynamic nature of cigarette smoke, it is important to characterize the exposure conditions in order to gain the best insight and accurately correlate exposure with biological endpoints. PMID:19772483

Scian, Mariano J; Oldham, Michael J; Miller, John H; Kane, David B; Edmiston, Jeffery S; McKinney, Willie J

2009-10-01

364

Vapor-Phase-Deposited Organosilane Coatings as "Hardening" Agents for High-Peak-Power Laser Optics  

SciTech Connect

Multilayer-dielectric (MLD) diffraction gratings are used in high-power laser systems to compress laser-energy pulses. The peak power deliverable on target for these short-pulse petawatt class systems is limited by the laser-damage resistance of the optical components in the system, especially the MLD gratings. Recent experiments in our laboratory have shown that vapor treatment of MLD gratings at room temperature with organosilanes such as hexamethyldisilazane (HMDS) produces an increase in their damage threshold as compared to uncoated MLD grating control samples.

Marshall, K.L.; Culakova, Z.; Ashe, B.; Giacofei, C.; Rigatti, A.L.; Kessler, T.J.; Schmid, A.W.; Oliver, J.B.; Kozlov, A.

2008-01-07

365

Development of a polysilicon process based on chemical vapor deposition, phase 1  

NASA Astrophysics Data System (ADS)

The goal of this program is to demonstrate that a dichlorosilane-based reductive chemical vapor deposition (CVD) process is capable of producing, at low cost, high quality polycrystalline silicon. Physical form and purity of this material will be consistent with LSA material requirements for use in the manufacture of high efficiency solar cells. Four polysilicon deposition runs were completed in an intermediate size reactor using dichlorosilane fed from 250 pound cylinders. Results from the intermediate size reactor are consistent with those obtained earlier with a small experimental reactor. Modifications of two intermediate size reactors were completed to interface with the dichlorosilane process demonstration unit (PDU).

Plahutnik, F.; Arvidson, A.; Sawyer, D.

1982-05-01

366

Preparation of Polypyrrole Film from Vapor Phase and Its Electrical Properties  

NASA Astrophysics Data System (ADS)

Polypyrrole film was prepared using iodine vapor. Spectroscopic measurements revealed that the polypyrrole film mainly consisted of a chain structure of pyrrole units, but that it contained some saturated pyrrolidine units, partially saturated units and hydroxyl groups. The maximum room temperature conductivity of the film was 10-1 S cm-1. The conductivity of the film in the temperature range from -150°C to 30°C obeyed the relation of \\ln??T-0.25. The thermopower of the film was positive. These electrical properties are similar to those of electrochemically prepared polypyrrole.

Asano, Mitsuharu; Inoue, Masumi; Takai, Yoshiaki; Mizutani, Teruyoshi; Ieda, Masayuki

1989-04-01

367

Membrane vapor enricher for Water For Injection (WFI) production, phase 1  

NASA Astrophysics Data System (ADS)

The U.S. Armed Forces have a logistical requirement for a continuous demand, high purity, Water For Injection (WFI) system to alleviate the logistical burden of transport and maintenance of large supplies of parenteral solutions. In this program, the feasibility of incorporating permeable membrane gas separation technology as the key element in the WFI production process has been evaluated. These high productivity, imperfection-free gas permeable membranes are highly selective to water vapor and are packaged in compact and lightweight hollow fiber module elements.

Gollan, Arye; Kleper, Myles H.

1987-12-01

368

Vapor-liquid phase equilibrium in systems with multiple chemical reactions  

Microsoft Academic Search

We introduce a new set of composition variables for treating phase equilibria in multicomponent, multi-reaction systems with or without inert components present. These variables provide a way of reducing the dimensionality of the problem and simplifying the analysis. We find that reactive azeotropes occur at points of equal transformed composition in each phase, but not equal mole fraction. Therefore, phase

Sophie Ung; Michael F. Doherty

1995-01-01

369

Mononuclear leukocyte DNA damage and oxidative stress: The association with smoking of hand-rolled and filter-cigarettes  

Microsoft Academic Search

Cigarette smoking is a major cause of human cancer at various sites, although its carcinogenic mechanisms still remain unestablished. Based on the use of a filter, cigarette smoke can be divided into a gas phase and a tar phase. Both contain different concentrations of oxidants, free radicals and tobacco-specific carcinogens. To explore the effects of both filtered and non-filtered cigarette

Abdurrahim Kocyigit; Sahbettin Selek; Hakim Celik; Murat Dikilitas

2011-01-01

370

Vapor-phase adsorption kinetics of 1-decene on hydrogenated Si(1 1 1)  

NASA Astrophysics Data System (ADS)

We have investigated in situ and in real time vapor-phase adsorption kinetics of 1-decene on hydrogenated Si(1 1 1), using attenuated total reflection Fourier transform infrared spectroscopy (ATR-FTIRS). The Si surface is hydrogenated in a NH4F solution. The p-polarized IR absorbance of Si H vibrational mode at 2083.7 cm-1 and its absence in s-polarized IR absorption spectrum support that the Si(1 1 1) surface is terminated mostly with monohydrides prior to 1-decene exposure. The 1-decene adsorption and simultaneous dehydrogenation result in a decane self-assembled monolayer (SAM). We have employed contact angle goniometry and angle-resolved X-ray photoelectron spectroscopy (AR-XPS) to characterize the decane SAM prepared at substrate temperatures ranging from 30 to 180 °C. Independent of the substrate temperature, the average sessile-drop water contact angle on decane SAM is 102 ± 2°, indicative of its hydrophobicity. The constant contact angle suggests that the decane coverage is approximately identical for all SAMs prepared in the above temperature range. The ratio of C(1s) to Si(2p) photoelectron intensities measured by AR-XPS and the integrated CH absorbance upon complete SAM formation measured using ATR-FTIRS further substantiate that the saturation surface coverage of decane is approximately equal for all SAMs. The thickness of the decane SAM and the tilt angle of the alkyl chain, calculated from the C(1s)/Si(2p) intensity ratio, are 13 ± 2 Å and 0 32° from the surface normal, respectively. This tilt angle agrees with 27° calculated from the dichroic ratio of polarized IR absorbance of C H stretching vibrational modes near 2900 cm-1. The polarization measurement additionally provides the twist angle of decane chains at 90°. The fractional surface coverage of decane and hydrogen, calculated from C H and Si H stretching vibrational modes, follow a 1st order Langmuir isotherm. The absolute saturation coverage of decane is approximately 4.2 × 1014 molecules/cm2. The isotherms indicate that the adsorption of 1-decene on hydrogenated Si(1 1 1) is a two-step process where fast adsorption precedes slow adsorption. At 80 °C, for instance, the empirical rate constant that governs the 1-decene adsorption is k2a?=(4.8±0.1)×10min for the fast adsorption step and k2b?=(1.2±0.1)×10min for the slow adsorption step. The rate constants measured at different substrate temperatures provide the apparent activation energy and pre-exponential factor for the rate-limiting step during fast adsorption: 1.7 ± 0.2 kcal/mol and 0.5 ± 0.1 min-1. The kinetics of decane SAM formation is well described by a chain reaction mechanism, in which alkene desorption is much faster than alkene adsorption and hydrogen abstraction by alkane radical. In this limit, the apparent activation energy for alkane formation is equal to the difference between the intrinsic barriers for hydrogen abstraction and desorption of the adsorbed alkane radical. As an approximation for 1-decene on Si(1 1 1), we have performed density functional theory calculations for the 1-hexene adsorption onto a model Si(1 0 0) surface and subsequent hydrogen abstraction by the secondary hexane radical to estimate kinetic parameters governing the steps in the chain mechanism. These calculations predict desorption and hydrogen abstraction barriers of 13.8 and 17.6 kcal/mol, respectively, which yield an effective activation energy of 3.8 kcal/mol, in good agreement with the experimentally determined value. The estimated values of the elementary rate constants further support the hypothesis that desorption is much faster than adsorption and hydrogen abstraction. The rate of alkane SAM formation is therefore determined by a kinetic competition between desorption and hydrogen abstraction. Assuming that the desorption-to-hydrogen-abstraction prefactor ratio ?-1/?2 is on the order of 103, the fractional surface coverage of Si dangling bonds (?) that initiate the 1-decene adsorption is 1 × 10-3, which translates to 7 × 1011 dangling bonds per cm2. Monitoring the decane SAM

Kosuri, Madhava R.; Gerung, Henry; Li, Qiming; Han, Sang M.; Herrera-Morales, Paulo E.; Weaver, Jason F.

2005-12-01

371

Cigarette Ads and Youth.  

ERIC Educational Resources Information Center

|Points out ways the tobacco industry markets products to youth, including paid advertisements, sponsorship of sporting events, music concerts, and magazines. Relates several focal points for smoking prevention, which include deglamorization of cigarette advertisements and making smoking socially undesirable. (LS)|

Carol, Julia

1988-01-01

372

QCM gas phase detection with ceramic materials--VOCs and oil vapors.  

PubMed

Titanate sol-gel layers imprinted with carbonic acids were used as sensitive layers on quartz crystal microbalance. These functionalized ceramics enable us detection of volatile organic compounds such as ethanol, n-propanol, n-butanol, n-hexane, n-heptane, n-/iso-octane, and n-decane. Variation of the precursors (i.e., tetrabutoxy titanium, tetrapropoxy titanium, tetraethoxy titanium) allows us to tune the sensitivity of the material by a factor of 7. Sensitivity as a function of precursors leads to selective inclusion of n-butanol vapors down to 1 ppm. The selectivity of materials is optimized to differentiate between isomers, e.g., n- and iso-octane. The results can be rationalized by correlating the sensor effects of hydrocarbons with the Wiener index. A mass-sensitive sensor based on titanate layer was also developed for monitoring emanation of degraded engine oil. Heating the sensor by a meander avoids vapor condensation. Thus, a continuously working oil quality sensor was designed. PMID:21301823

Latif, Usman; Rohrer, Andreas; Lieberzeit, Peter A; Dickert, Franz L

2011-02-08

373

Early specific free radical-related cytotoxicity of gas phase cigarette smoke and its paradoxical temporary inhibition by tar: An electron paramagnetic resonance study with the spin trap DEPMPO.  

PubMed

Electron paramagnetic resonance (EPR) spin trapping studies demonstrated aqueous tar particulate matter (TPM) and gas phase cigarette smoke (GPCS) to behave as different sources of free radicals in cigarette smoke (CS) but their cytotoxic implications have been only assessed in CS due to its relevance to the natural smoking process. Using a sensitive spin trapping detection with 5-(diethoxyphosphoryl)-5-methyl-1-pyrroline-N-oxide (DEPMPO), this study compared the respective roles of CS- and GPCS-derived free radicals on smoke-induced cytotoxicity and lipid peroxidation of filtered and unfiltered, machine-smoked experimental and reference cigarettes yielding a wide range of TPM yields. In buffer bubbled with CS the DEPMPO/superoxide spin adduct was the major detected nitroxide. Use of appropriate control experiments with nitric oxide radical (NO*) or carbonyl sulfide, and a computer analysis of spin adduct diastereoisomery showed that the hydroxyl radical (HO*) adduct of DEPMPO seen in GPCS-bubbled was rather related to metal-catalyzed nucleophilic synthesis than to direct HO* trapping. Unexpectedly a protective effect of TPM on murine 3T3 fibroblasts was observed in early (<3h) free radical-, GPCS-induced cell death, and carbon filtering decreased free radical formation, toxicity and lipid peroxidation in three cell lines (including human epithelial lung cells) challenged with GPCS. These results highlight an acute, free radical-dependent, harmful mechanism specific to the GPCS phase, possibly involving NO* chemistry, whose physical or chemical control may be of great interest with the aim of reducing the toxicity of smoke. PMID:17083924

Culcasi, Marcel; Muller, Agnès; Mercier, Anne; Clément, Jean-Louis; Payet, Olivier; Rockenbauer, Antal; Marchand, Véronique; Pietri, Sylvia

2006-10-06

374

Bin-Resolved Microphysical Modeling of Water Vapor Isotopic Composition During Ice Nucleation and Growth in Mixed-Phase Clouds  

NASA Astrophysics Data System (ADS)

Because any phase change in water is accompanied by isotopic fractionation, ice nucleation and growth in mixed-phase and cirrus clouds should be accompanied by large isotopic changes, and isotopic composition can be a useful tracer for understanding microphysics in these contexts. However, detailed microphysical modeling that includes isotopologues of water has not previously been done. We present here initial studies with the BRIMM ("Bin-Resolved Isotopic Microphysical Model") model, developed at ETH Zurich, a bin-resolved model that incorporates isotopic accounting during evaporation and condensation. Explicit resolution of particle sizes is especially important for isotopic microphysics because particle sizes affect isotopic evolution: in particular, heating via the latent heat of condensation has strong effects on isotopic fractionation and can be misrepresented by a bulk microphysical model. We show here the range of isotopic evolution produced by changes in physical parameters and processes, focusing especially on latent heat effects in the Bergeron process, as water is transferred from liquid to solid particles through the vapor phase. These isotopic studies can form the foundations for interpretation of eventual in-situ measurements of isotopic compositions in cirrus and mixed-phase clouds.

Aho, S.; Weinhold, F.; Peter, T.; Moyer, E. J.

2011-12-01

375

Porous single-phase NiTi processed under Ca reducing vapor for use as a bone graft substitute.  

PubMed

Porous nickel-titanium alloys (NiTi, nitinol) have recently attracted attention in clinical surgery because they are a very interesting alternative to the more brittle and less machinable conventional porous Ca-based ceramics. The main remaining limitations come from the chemical homogeneity of the as-processed porous nickel-titanium alloys, which always contain undesired secondary Ti- and Ni-rich phases. These are known to weaken the NiTi products, to favor their cavitation corrosion and to decrease their biocompatibility. Elemental nickel must also be avoided because it could give rise to several adverse tissue reactions. Therefore, the synthesis of porous single-phase NiTi alloys by using a basic single-step sintering procedure is an important step towards the processing of safe implant materials. The sintering process used in this work is based on a vapor phase calciothermic reduction operating during the NiTi compound formation. The as-processed porous nickel-titanium microstructure is single-phase and shows a uniformly open pore distribution with porosity of about 53% and pore diameters in the range 20-100 microm. Furthermore, due to the process, fine CaO layers grow on the NiTi outer and inner surfaces, acting as possible promoting agents for the ingrowth of bone cells at the implantation site. PMID:16174525

Bertheville, Bernard

2005-09-19

376

Absolute integrated intensities of vapor-phase hydrogen peroxide (H202) in the mid-infrared at atmospheric pressure  

SciTech Connect

We report quantitative broadband infrared spectra of vapor-phase hydrogen peroxide (H2O2) with all spectra pressure broadened to atmospheric pressure. The spectra were generated by flowing a concentrated solution (83 weight%) of H2O2 into a gently heated disseminator and diluting with a flow of pure nitrogen carrier gas. The water vapor lines were subtracted from the resulting spectra to yield the spectrum of pure H2O2. Comparison with previous results for the ?6 band strength (including hot bands) compares favorably with the results of Klee et al. [(1999) J. Mol. Spectr. 195, 154] as well as HITRAN. The present results are 433 and 467 cm-2 atm-1 (±8% and ±3% at 298 and 323 K, respectively) for the band strength, matching well the Klee value (S = 467 cm-2 atm-1 at 296 K) for the integrated band. Other bands in the 520-7500 cm-1 interval and their potential for atmospheric monitoring are discussed.

Johnson, Timothy J.; Sams, Robert L.; Burton, Sarah D.; Blake, Thomas A.

2009-09-01

377

GaN Lateral Overgrowth by Hydride Vapor Phase Epitaxy through Nanometer-Size Channels Fabricated with Nanoimprint Lithography  

NASA Astrophysics Data System (ADS)

Epitaxial lateral overgrowth (ELO) has been used for reducing the dislocation density to grow high-quality GaN crystals. In conventional ELO, micrometer-size channels formed on a mask material such as SiO2, where GaN growth starts, are generally used. In the present study, ELO through nanometer-size (50--80 nm) channels is investigated to improve the dislocation reduction ability. Channels are fabricated using nanoimprint lithography and dry etching. We demonstrate for the first time successful hydride vapor phase epitaxy (HVPE)-based GaN ELO growth through nanochannels. In the growth interface, distinct facet structures appear and coalescence between neighboring facets proceeds. The surface of a 20-?m-thick GaN layer becomes flat by the valleys between facet structures being buried. The dislocation density is shown to decrease to approximately 5× 107 cm-2 for a 20-?m-thick GaN layer on sapphire. Photoluminescence measurements show a decay time of over 3 times longer than that of a conventional metalorganic chemical vapor deposition (MOCVD) template.

Usui, Akira; Matsueda, Toshiharu; Goto, Hiroki; Sunakawa, Haruo; Fujiyama, Yasuharu; Ishihara, Yujiro; Okada, Akiko; Shoji, Shuichi; Yamaguchi, Atsushi A.; Nishihara, Hiromi; Shinohara, Hidetoshi; Goto, Hiroshi; Mizuno, Jun

2013-08-01

378

Heme oxygenase-1 gene expression in human alveolar epithelial cells (A549) following exposure to whole cigarette smoke on a direct in vitro exposure system.  

PubMed

Many in vitro studies have employed cigarette smoke condensates or soluble smoke components to investigate the biological effects of cigarette smoke. However, neither of these methods evaluates the biological effects of fresh whole cigarette smoke. It is most desirable to conduct in vitro biological studies under conditions which accommodate the dynamic physicochemical character of fresh cigarette smoke. Previously we reported the development of a whole smoke exposure system to assess the biological effects of mainstream cigarette smoke. The exposure system design was based on a combination of the sedimentation procedure and the CULTEX cultivation technique, which includes a systemized air/liquid interface methodology and exposes the cells to fresh smoke at every puff. The aim of this study was to adopt the other biological endpoint to our whole smoke exposure system. We focused on heme oxygenase (HO)-1 mRNA gene expression, an enzyme which has recently been shown to be highly responsible for oxidative stress. In the present study, a dose-response relationship between the HO-1 mRNA expression based on the reverse transcription real-time PCR method and total exposure to cigarette smoke was observed. When a Cambridge filter pad was placed between the cigarette and exposure module, to ensure the cells were only exposed to the gas/vapor phase, the latter, as well as the whole smoke, induced HO-1 mRNA dose dependently. For the next step, acetate plain and charcoal filters with the same pressure drop were prepared to assess the potential ability of charcoal filters with regard to the vapor phase performance. The results revealed reduced HO-1 mRNA gene expression when a charcoal filter was used. Direct whole smoke exposure is a significant approach and may reflect the conditions of exposure essentially resulting from direct contact between cells and a dynamic mixture of gaseous and particulate constituents. We were able to adopt a gene expression assay for oxidative stress to the whole smoke exposure system, following the adaptation of cytotoxicity assays. This system, which includes several advantages involving the post-exposure washing of cells, by adding the exchanging medium and assuring the exposure of the particulate phase through the sedimentation method, may have potential for further investigations into the molecular basis of smoking-related lung disease. PMID:16704925

Fukano, Yasuo; Yoshimura, Hiroyuki; Yoshida, Takemi

2006-05-15

379

Development of a polysilicon process based on chemical vapor deposition, phase 1  

NASA Astrophysics Data System (ADS)

The development of a dichlorosilane-based reductive chemical vapor deposition process for the production of polycrystalline silicon is discussed. Experimental data indicate that the ease of ignition and explosion severity of dichlorosilane (DCS)/air mixtures is substantially attenuated if the DCS is diluted with hydrogen. Redesign of the process development unit to accommodate safety related information is described. Several different sources of trichlorosilane were used to generate a mixture of redistributed chlorosilanes via Dowex ion exchange resin. The unseparated mixtures were then fed to an experimental reactor in which silicon was deposited and the deposited silicon analyzed for electrically active impurities. At least one trichlorosilane source provided material of requisite purity. Silicon grown in the experimental reactor was converted to single crystal material and solar cells fabricated and tested.

McCormick, J.; Sharp, K.; Arvidson, A.; Sawyer, D.

1981-03-01

380

Development of a polysilicon process based on chemical vapor deposition (phase 1)  

NASA Astrophysics Data System (ADS)

A dichlorosilane-based reductive chemical vapor deposition (CVD) process demonstrated is capable of producing, at low cost, high quality polycrystalline silicon. Testing of decomposition reactor heat shields to insure that the shield provides adequate personnel protection assuming a worst case explosion was completed. Minor modifications to a production reactor heat shield provided adequate heat shield integrity. Construction of the redesigned PDU (Process Development Unit) to accommodate all safety related information proceeded on schedule. Structural steel work was completed as is the piping and instrumentation design work. Major pieces of process equipment were received and positioned in the support structure and all transfer piping and conduits to the PDU were installed. Construction was completed on a feed system for supplying DCS to an intermediate sized reactor. The feed system was successfully interfaced with a reactor equipped with a modified heat shield. Reactor checkout was completed.

McCormick, J.; Arvidson, A.; Sawyer, D.; Plahutnik, F.

1981-06-01

381

Magnetite whiskers and platelets in the ALH84001 Martian meteorite: evidence of vapor phase growth.  

PubMed

Nanometer-sized magnetite crystals associated with carbonates in fracture zones within Martian meteorite ALH84001 have been examined using analytical transmission electron microscopy. Some of the crystals exhibit distinctive morphologies: filamentary rods and ribbon, and platelets. The rods and ribbons are elongated along the crystallographic [100] and [111] directions. Some of the rods contain microstructural defects indicating that they grew by spiral growth about screw dislocations. Platelets are flattened along the [100] and [110] directions. These unique morphologies and microstructures constrain the growth conditions of magnetite. The whiskers and platelets most likely formed in the temperature range 500-800 degrees C by direct condensation from a vapor or precipitation from a supercritical fluid, and their properties are inconsistent with a biogenic origin. PMID:11541129

Bradley, J P; Harvey, R P; McSween, H Y

1996-01-01

382

27 CFR 40.352 - Cigarette tubes.  

Code of Federal Regulations, 2013 CFR

...AND PROCESSED TOBACCO Manufacture of Cigarette Papers and Tubes Taxes § 40.352 Cigarette tubes. Cigarette tubes are taxed...thereof, of the length of each as one cigarette tube. * Tax rate for less than 50 tubes is the...

2013-04-01

383

27 CFR 41.35 - Cigarette tubes.  

Code of Federal Regulations, 2013 CFR

...IMPORTATION OF TOBACCO PRODUCTS, CIGARETTE PAPERS AND TUBES, AND PROCESSED TOBACCO Taxes Tax Rates § 41.35 Cigarette tubes. Cigarette tubes...the length of each as one cigarette tube. * Tax rate for less than 50...

2013-04-01

384

Investigation of Growth Mechanism for InGaN by Metal--Organic Vapor Phase Epitaxy Using Computational Fluid Simulation  

NASA Astrophysics Data System (ADS)

We investigated the mechanism of metal--organic vapor phase epitaxy (MOVPE) growth for InGaN by comparing experimental and simulation results. The simulation results showed a similar trend to the experimental results. Therefore, the simulation system can be used to speculate on physical and chemical phenomena through the behavior of precursors. InGaN growth is largely affected by the amounts of both trimethylindium (TMIn) and NH3 supplied. This is because InN growth is dependent on the amount of NH2 physisorbed on a surface, which is generated by NH3. Moreover, the decomposition of crystallized InN and the desorption of these decomposed precursors of InN during growth cannot be ignored.

Deura, Momoko; Ichinohe, Fumitaka; Arai, Yu; Shiohama, Kenichi; Hirako, Akira; Ohkawa, Kazuhiro

2013-08-01

385

In situ X-ray reflectivity of indium supplied on GaN templates by metal organic vapor phase epitaxy  

NASA Astrophysics Data System (ADS)

The indium supplied on c-plane GaN templates using Metal organic vapor phase epitaxy was studied by in situ X-ray reflectivity (XRR) at 800 °C. The presence of liquid indium layers on the GaN (0001) surface was demonstrated using data-fitting of XRR measurements, ex situ atomic force microscope, auger electron spectroscopy, and cross-sectional scanning electron microscope. These measurements demonstrated that a liquid indium layer coexisted with indium droplets on top of the GaN (0001) surface at 800 °C. The liquid indium film thicknesses increased with increasing TMIn supply time and did not change during cooling from 800 °C to room temperature.

Ju, Guangxu; Fuchi, Shingo; Tabuchi, Masao; Takeda, Yoshikazu

2013-09-01

386

Vapor-phase reaction of acetophenone with methanol or dimethyl carbonate on magnesium oxide and magnesium phosphates  

SciTech Connect

The vapor-phase reaction of acetophenone with methanol on magnesium oxide, various magnesium phosphates, and combinations of the two types of catalysts was studied. The process was found to involve the Meerwein-Ponndorf-Verley reaction, aldol condensations, dehydrations, and hydrogenations. The presence of basic sites is indispensable for the reaction to develop; however, acid sites also play an active role. The selectivity for each reaction product depends on the particular catalyst used. The total conversion is maximal with the catalysts containing the largest populations of acid and basic sites. Also, catalysts with large numbers of acid sites exhibit an increased selectivity towards the corresponding alkenes. The use of dimethyl carbonate instead of methanol alters the reaction selectivity to an extent dependent on the particular catalyst and operating conditions. However, this also results in markedly decreased total conversion in some instances.

Aramendia, M.A.; Borau, V.; Jimenez, C.; Marinas, J.M.; Romero, F.J. [Univ. of Cordoba (Spain). Dept. of Organic Chemistry

1999-04-01

387

AlN Grown on a- and n-Plane Sapphire Substrates by Low-Pressure Hydride Vapor Phase Epitaxy  

NASA Astrophysics Data System (ADS)

We have studied the properties of AlN layers grown by low-pressure hydride vapor phase epitaxy (HVPE) on n-plane (11\\bar{2}3) sapphire substrates and compared them with those of AlN layers on a-plane (11\\bar{2}0) sapphire substrates. c-Plane AlN was grown on a-plane sapphire. In the case of AlN growth on n-plane sapphire, the c-axis of AlN was tilted by about 1.2° relative to the n-axis of sapphire, unlike AlN growth on a-plane sapphire. For AlN grown on a-plane sapphire, the in-plane epitaxial relationship between AlN and sapphire changed with nitridation temperature in the initial-stage of growth, but it remained constant for AlN grown on n-plane sapphire.

Goriki, Naoki; Miyake, Hideto; Hiramatsu, Kazumasa; Akiyama, Toru; Ito, Tomonori; Eryu, Osamu

2013-08-01

388

Strain effects in GaN epilayers grown on different substrates by metal organic vapor phase epitaxy  

NASA Astrophysics Data System (ADS)

For practical applications, it is important to control strain by carefully tuning growth conditions for stress modification. Strain can have a pronounced impact on device behavior and is caused by extrinsic thermal stress and a tunable intrinsic growth stress. The impact of strain on GaN epilayers was investigated by photoluminescence and high resolution x-ray diffraction (XRD). The GaN samples were grown by metal organic vapor phase epitaxy, on sapphire, 4H-SiC, freestanding GaN and Si (111) substrates. Both free and bound exciton transitions were observed at low temperature, and their energy shift was analyzed with respect to the strain values derived from XRD. We also characterized the valence band split and the GaN bandgap as a function of the strain at 4 K.

Zhang, L.; Cheng, K.; Degroote, S.; Leys, M.; Germain, M.; Borghs, G.

2010-10-01

389

Growth of high quality CdTe and ZnTe on Si substrates using organometallic vapor phase epitaxy  

NASA Astrophysics Data System (ADS)

Epitaxial (100) CdTe and ZnTe layers with high crystalline quality have been grown on Si substrates by atmospheric pressure organometallic vapor phase epitaxy (OMVPE). A thin Ge interfacial layer grown at low temperature was used as a buffer layer prior to ZnTe and CdTe growth. The layers were characterized by Nomarski optical microscopy and double crystal x-ray diffraction. Double crystal rocking curves with full width at half maximum of about 110 and 250 arc-sec have been obtained for a 7 ?m thick ZnTe layer and a 4 ?m thick CdTe layer, respectively. The results presented demonstrate a novel method of in-situ Si cleaning step without a high temperature deoxidation process to grow high quality CdTe and ZnTe on Si in a single OMVPE reactor.

Wang, Wen-Sheng; Bhat, Ishwara

1995-05-01

390

Growth of ZnSe{sub 1-x}S{sub x} solid solution crystals from vapor phase  

SciTech Connect

Partially faceted ZnSe{sub 1-x}S{sub x} solid solution crystals have been grown from a vapor phase in a closed stationary horizontal system. The growth has been performed in cylindrical quartz ampoules-{approx}10 mm in diameter and evacuated to a residual pressure of less than {approx}10{sup -3} Pa-at a temperature of 1050{sup o}C and a temperature drop between the source and growth zones of 10-16 deg. C. The crystal structure, optical absorption, and composition inhomogeneity along the ingot length have been investigated by X-ray diffractometry and optical spectroscopy in the wavelength range of 300-3000 nm. The solid-solution composition range corresponding to cubic polymorphs is determined. The concentration dependences of the lattice parameter and band gap are presented.

Barsukova, E. L., E-mail: barsukova@ifttp.bas-net.by; Postnova, L. I.; Levchenko, V. I. [Scientific-Practical Materials Research Center of the National Academy of Sciences of Belarus (Belarus)

2009-12-15

391

Postgrowth Annealing of CdTe Layers Grown on Si Substrates by Metalorganic Vapor-Phase Epitaxy  

NASA Astrophysics Data System (ADS)

Annealing conditions of CdTe layers grown on Si substrates by metalorganic vapor-phase epitaxy were studied. Typically, 3-?m-thick n-type (211) CdTe layers were annealed for 60 s in flowing hydrogen at atmospheric pressure by covering their surfaces with bulk CdTe wafers. At annealing temperatures above 700°C, improvement of crystal quality was confirmed from full-width at half-maximum values of double-crystal rocking-curve measurements and x-ray diffraction measurements. Photoluminescence measurements revealed no deterioration of electrical properties in the annealed n-CdTe layers. Furthermore, annealing at 900°C improved the performance of radiation detectors with structure of p-like CdTe/n-CdTe/n +-Si substrate.

Yasuda, K.; Niraula, M.; Namba, S.; Kondo, T.; Muramatsu, S.; Yamashita, H.; Wajima, Y.; Agata, Y.

2013-08-01

392

Preparation of mesoporous nanofibers by vapor phase synthesis: control of mesopore structures with the aid of co-surfactants.  

PubMed

Mesoporous nanofibers (MSNFs) can be fabricated in the pores of anodic aluminum oxide (AAO) membrane using diverse methods. Among them vapor phase synthesis (VPS) provides several advantages over sol-gel or evaporation-induced self-assembly (EISA) based methods. One powerful advantage is that we can employ multiple surfactants as structural directing agents (SDAs) simultaneously. By adopting diverse pairs of SDAs, we can control the mesopore structures, i.e. pore size, surface area, and even the morphology of mesostructures. Here, we used F127 as a main SDA, which is relatively robust (thus, difficult to change the mesopore structures), and added a series of cationic co-surfactants to observe the systematical changes in their mesostructure with respect to the chain length of the co-surfactant. PMID:23723185

Min, Sa Hoon; Bae, Joonwon; Jang, Jyongsik; Lee, Kyung Jin

2013-05-30

393

Equilibrium States of Liquid, Solid, and Vapor and the Configurations for Copper, Tungsten, and Pores in Liquid-Phase Sintering  

NASA Astrophysics Data System (ADS)

The equilibrium state of the liquid-solid structure during liquid-phase sintering (LPS) is pondered with respect to minimum energy geometries. Besides the solid-liquid ratio, several interfacial energies determine the most stable geometric configuration. In this study, we rely on the attributes of the copper or nickel as the liquid, tungsten as the solid, and vapor to solve for terminal configurations that include liquid pools inside the solid grains. Surface evolution is enabled using a stepwise computer program[1] to rearrange and reshape small grain clusters reflective of LPS based on a preset combination of wetting and dihedral angles. The findings show how different interfacial energies, as a result of oxidation or impurity segregation, play a role in determining the final geometry. The specific concern is identification of situations in which a liquid is stable inside the solid, as observed in some LPS materials.

Fikes, Jonathan; Park, Seong Jin; German, Randall M.

2011-02-01

394

A Simple Growth Method to Produce a-Plane GaN Thick Films by Hydride Vapor Phase Epitaxy  

NASA Astrophysics Data System (ADS)

A-plane GaN was grown on r-plane sapphire using a two-step growth method by hydride vapor phase epitaxy (HVPE). In the first step, a-plane GaN formed triangular stripes along the m-direction ([\\bar{1}100] direction) at a low growth temperature. Then, increasing the growth temperature enhanced the lateral growth mode to coalesce a-plane GaN in the second step. There were triangular voids formed after growth. In this work, a new method was developed to produce the voids in the a-plane GaN film using the two-step growth method without optical lithography.

Wu, Yin-Hao; Lee, Chuo-Han; Chu, Chung-Ming; Yeh, Yen-Hsien; Chen, Chan-Lin; Lee, Wei-I

2013-08-01

395

Characterization of the Nonpolar GaN Substrate Obtained by Multistep Regrowth by Hydride Vapor Phase Epitaxy  

NASA Astrophysics Data System (ADS)

One of the most promising methods of obtaining nonpolar GaN substrates is regrowth of thick GaN crystals using hydride vapor phase epitaxy (HVPE). The multistep growth was performed along the c polar direction. After HVPE depositions, the crystal was sliced along (11\\bar{2}0) nonpolar planes. On such samples, we performed structural high-resolution X-ray characterization. The full width at half maximum of the X-ray rocking curves for the 11\\bar{2}0 reflection achieved 27 arcsec. The interfaces between each regrowth step were clearly visible in cathodoluminescence (CL), due to different concentrations of residual dopants before and after a regrowth step.

Teisseyre, Henryk; Domagala, Jaroslaw Zbigniew; Lucznik, Boleslaw; Reszka, Anna; Kowalski, Bogdan Jerzy; Bockowski, Michal; Kamler, Grzegorz; Grzegory, Izabella

2012-01-01

396

Structural evolution of GaN layers grown on (0 0 0 1) sapphire by hydride vapor phase epitaxy  

NASA Astrophysics Data System (ADS)

GaN was grown directly on (0 0 0 1) sapphire by a two-step process using hydride vapor phase epitaxy (HVPE). Nucleation layers deposited on sapphire at ˜450-500 °C consisted of localized epitaxial wurtzite GaN nano-crystals. In between and above the epitaxial nano-crystals were randomly oriented wurtzite GaN nano-crystals. GaN islands of various sizes and shapes were formed, after annealing between ˜900 and 1000 °C, through a decomposition-redeposition process. Preferential growth of GaN occurred on the islands that had an epitaxial relationship with sapphire during the subsequent high-temperature overgrowth. Threading dislocations were observed in isolated GaN islands that were formed after annealing.

Meng, F. Y.; Han, I.; McFelea, H.; Lindow, E.; Bertram, R.; Werkhoven, C.; Arena, C.; Mahajan, S.

2011-07-01

397

Enhanced quality thin film Cu(In,Ga)Se[sub 2] for semiconductor device applications by vapor-phase recrystallization  

DOEpatents

Enhanced quality thin films of Cu[sub w](In,Ga[sub y])Se[sub z] for semiconductor device applications are fabricated by initially forming a Cu-rich, phase-separated compound mixture comprising Cu(In,Ga):Cu[sub x]Se on a substrate to form a large-grain precursor and then converting the excess Cu[sub x]Se to Cu(In,Ga)Se[sub 2] by exposing it to an activity of In and/or Ga, either in vapor In and/or Ga form or in solid (In,Ga)[sub y]Se[sub z]. Alternatively, the conversion can be made by sequential deposition of In and/or Ga and Se onto the phase-separated precursor. The conversion process is preferably performed in the temperature range of about 300--600 C, where the Cu(In,Ga)Se[sub 2] remains solid, while the excess Cu[sub x]Se is in a liquid flux. The characteristic of the resulting Cu[sub w](In,Ga)[sub y]Se[sub z] can be controlled by the temperature. Higher temperatures, such as 500--600 C, result in a nearly stoichiometric Cu(In,Ga)Se[sub 2], whereas lower temperatures, such as 300--400 C, result in a more Cu-poor compound, such as the Cu[sub z](In,Ga)[sub 4]Se[sub 7] phase. 7 figs.

Tuttle, J.R.; Contreras, M.A.; Noufi, R.; Albin, D.S.

1994-10-18

398

Ultrasensitive ultraviolet-visible 20 fs absorption spectroscopy of low vapor pressure molecules in the gas phase.  

PubMed

We describe an ultrasensitive pump-probe spectrometer for transient absorption measurements in the gas phase and in solution. The tunable UV pump and the visible (450-740 nm) probe pulses are generated by two independently tunable noncollinear optical parametric amplifiers, providing a temporal resolution of 20 fs. A homebuilt low gain photodetector is used to accommodate strong probe pulses with a shot noise significantly lower than the overall measurement noise. A matched digitizing scheme for single shot analysis of the light pulses at kilohertz repetition rates that minimizes the electronic noise contributions to the transient absorption signal is developed. The data processing scheme is optimized to yield best suppression of the laser excess noise and thereby transient absorbance changes down to 1.1 x 10(-6) can be resolved. A collinear focusing geometry optimized for a 50 mm interaction length combined with a heatable gas cell allows us to perform measurements on substances with low vapor pressures, e.g., on medium sized molecules which are crystalline at room temperature. As an application example highlighting the capability of this instrument, we present the direct time-domain observation of the ultrafast excited state intramolecular proton transfer of 2-(2(')-hydroxyphenyl)benzothiazole in the gas phase. We are able to compare the resulting dynamics in the gas phase and in solution with a temporal precision of better than 5 fs. PMID:18248022

Schriever, C; Lochbrunner, S; Riedle, E; Nesbitt, D J

2008-01-01

399

The influence of equilibrium chemical reactions on vapor-liquid phase diagrams  

SciTech Connect

Phase diagrams for simultaneous chemical reaction and phase equilibrium are presented for ideal and non-ideal systems. It is shown that reactive-azeotropes can occur for ideal mixtures. The conditions for formation of reactive-azeotropes in constant volatility systems are derived. These conditions show that for such systems reactive-azeotropes can occur only when the volatiles of the reactants are either all higher or all lower than the volatilities of the products.

Barbosa, D.; Doherty, M.F.

1986-01-01

400

Vapor Detection  

NASA Astrophysics Data System (ADS)

This presentation will describe recent results in exploiting the vapor detection technology developed at Caltech that forms the basis for a low power, simple "electronic nose". Thin films of carbon black-organic polymer composites have been deposited across two metallic leads, with swelling-induced resistance changes of the films signaling the presence of vapors. To identify and classify vapors, arrays of such vapor sensing elements have been constructed. Each element contained a different organic polymer as the insulating phase. The differing gas-solid partition coefficients for the various polymers of the detector array produced a pattern of resistance changes that was used to classify vapors and vapor mixtures. The performance of this system towards DNT, the predominant signature in the vapor phase above land mines, has been evaluated in detail, with robust detection demonstrated in the laboratory in less than 5 s in air at DNT levels in the low ppb range. We will also discuss integration of the sensors, signal preprocessing, signal processing, and data analysis functions into a single, low power, low cost, "nose chip". In addition, we report advances in fluidic design that allow improvements in signal/noise through optimization of the detector film area and geometric optimization of the detector film volume as it interacts with the injected flow from the sampling analyte plug. An analytical expression derived for the signal/noise performance as a function of detector area implies that there is an optimum detector film volume which will produce the best signal/noise ratio for a given carbon black-polymer composite when exposed to a finite volume of sampled analyte. This prediction has been verified experimentally by exploring the response behavior of detectors having a variety of different geometric form factors. We also demonstrate that useful information can be obtained from the spatiotemporal response profile of an analyte moving at a controlled flow velocity across an array of chemically identical, but spatially nonequivalent, detector films. W also demonstrate the use of these design principles, incorporated with an analysis of the changes in detector signals in response to variations in analyte flow rate, to obtain useful information on the composition of analytes and analyte mixtures.

Lewis, Nathan

2003-04-01

401

Vapor-phase-deposited organosilane coatings as hardening agents for high-peak-power laser optics  

NASA Astrophysics Data System (ADS)

Multilayer-dielectric (MLD) diffraction gratings are used in high-power laser systems to compress laser-energy pulses. The peak power deliverable on target for these short-pulse petawatt class systems is limited by the laser-damage resistance of the optical components in the system, especially the MLD gratings. Recent experiments in our laboratory have shown that vapor treatment of MLD gratings at room temperature with organosilanes such as hexamethyldisilazane (HMDS) produces an increase in their damage threshold at 1054 nm (10-ps, 370- ?m spot size) as compared to uncoated MLD grating control samples. The 1-on-1 laser-damage threshold of an HMDS-treated grating increased by 4.5% as compared to the uncoated control sample, while the N-on-1 damage threshold of an MLD grating treated with tetramethyldisilazane increased by 16.5%. For an MLD grating treated with bis-(trifluoropropyl)tetramethyldisilazane, the N-on-1 and 1-on-1 damage thresholds increased by 4.8% and 5.3%, respectively. Such increases in laser-damage threshold are unprecedented and counterintuitive because it is widely believed that the presence of organic materials or coatings on the surfaces of optical substrates will inevitably lead to reduced laser-damage resistance.

Marshall, K. L.; Culakova, Z.; Ashe, B.; Giacofei, C.; Rigatti, A. L.; Kessler, T. J.; Schmid, A. W.; Oliver, J. B.; Kozlov, A.

2007-09-01

402

Cigarette smoking in asthma.  

PubMed

A survey was performed of smoking habits and respiratory symptoms of 106 asthmatic patients attending a hospital out-patient clinic. A quarter of the patients were currently smokers and a further quarter were ex-smokers. Less than a third of the smokers complained of symptoms of wheeze or dyspnoea after smoking. Asthmatic smokers had a much higher prevalence of chronic cough but their lung function appeared no lower than non-smokers. Ten asthmatic smokers were selected to contrast their acute bronchial response to smoking a currently marketed cigarette with that of ten asymptomatic smokers. Only four of ten asthmatic patients and two of ten asymptomatic smokers developed acute airway narrowing after smoking despite changes in venous blood nicotine levels which confirmed cigarette smoke inhalation. Many more asthmatic patients smoke than might be expected from the known instability of their airways. Our failure to show frequent and substantial airway reactivity to cigarette smoke in these patients suggests either that cigarette smoke may not be as acutely irritant as might be anticipated or that some asthmatic patients acquire tolerance to it. The effects of chronic cigarette consumption could be demonstrated even in this small sample which suggests that asthmatic patients should be advised to stop smoking, especially as many clinicians expect asthma and smoking to be a rare coincidence. PMID:7426367

Higenbottam, T W; Feyeraband, C; Clark, T J

1980-07-01

403

"Light" Cigarettes and Cancer Risk  

MedlinePLUS

... blends of tobacco. When analyzed by a smoking machine, the smoke from a so-called light cigarette ... the smoke from a regular cigarette. However, a machine cannot predict how much tar a smoker inhales. ...

404

Thermodynamic Properties of Nitrogen Including Liquid and Vapor Phases from 63K to 2000K with Pressures to 10,000 Bar.  

National Technical Information Service (NTIS)

Tables of thermodynamic properties of nitrogen are presented for the liquid and vapor phases for temperatures from the freezing line to 2000K and pressures to 10,000 bar. The tables include values of density, internal energy, enthalpy, entropy, isochoric ...

R. B. Stewart R. T. Jacobsen

1973-01-01

405

Gas-phase temperature measurement in the vaporizing spray of a gasoline direct-injection injector by use of pure rotational coherent anti-Stokes Raman scattering.  

PubMed

Pure rotational coherent anti-Stokes Raman spectroscopy is applied for quantitative gas-phase temperature measurements in the vaporizing spray of an automotive fuel injector. Interferences from elastically scattered stray light are greatly reduced by use of a polarization technique and spectral filtering in a double monochromator. The applicability of this technique to probing low-temperature sprays is successfully demonstrated. PMID:14759040

Beyrau, Frank; Bräuer, Andreas; Seeger, Thomas; Leipertz, Alfred

2004-02-01

406

Determination of the adsorptive capacity and adsorption isotherm of vapor-phase mercury chloride on powdered activated carbon using thermogravimetric analysis  

Microsoft Academic Search

This study investigated the use of thermogravimetric analysis (TGA) to determine the adsorptive capacity and adsorption isotherm of vapor-phase mercury chloride on powdered activated carbon (PAC). The technique is commonly applied to remove mercury-containing air pollutants from gas streams emitted from municipal solid waste incinerators. An alternative form of powdered activated carbon derived from a pyrolyzed tire char was prepared

Hsun-Yu Lin; Chung-Shin Yuan; Wei-Ching Chen; Chung-Hsuang Hung

2006-01-01

407

Manufacturing of high aspect-ratio p-n junctions using vapor phase doping for application in multi-Resurf devices  

Microsoft Academic Search

A new technique to manufacture vertical Resurf devices is presented, in which the alternating p-n junctions in the drift region are formed by a combination of trench etching and vapor phase doping (VPD). Scanning capacitance microscopy (SCM) was performed to investigate these deep p-n junctions, showing a uniform doping profile along the full depth of the devices. Electrical measurements on

C. Rochefort; R. van Dalen; N. Duhayon; W. Vandervorst

2002-01-01

408

Secondary phase formation and the microstructural evolution of surface layers during vapor phase alteration of the French SON 68 nuclear waste glass at 200{degrees}C  

SciTech Connect

The SON 68 inactive {open_quotes}R7T7{close_quotes} composition is the French reference glass for the LWR nuclear waste glass. Vapor phase alteration was used to accelerate the reaction progress of glass corrosion and to develop the characteristic suite of secondary, alteration phases. Extensive solid-state characterization (AEM/SEM/HRTEM) was completed on six inactive R7T7 waste glasses which were altered in the presence of saturated water vapor (200{degrees}C) for 91, 241, 908, 1000, 1013, and 1021 days. The AEM samples were examined in cross-section (lattice-fringe imaging, micro-diffraction, and quantitative thin-film EDS analysis). The glass monoliths were invariably covered with a thin altered rind. The layer became thicker with time: 0.5 {mu}m for 22 days; 4 {mu}m for 91 days; 6 {mu}m for 241 days; 10 {mu}m for 908 days; 26 {mu}m for 1013 days; and <35 {mu}m for 1021 days. The composite alteration layer of the SON 68 samples is at least four time less thick than that of the SRL 131 glass composition. Six distinctive zones, based on phase chemistry and microstructure, were distinguished within the well-developed surface layers. Numerous crystalline phases such as analcime, tobermorite, apatite, and weeksite were identified on the surfaces of the reacted glasses as precipitates. Two crystalline phases, Ag{sub 2}TeO{sub 3} and (Ca,Sr)Mo{sub 3}O{sub 9}(OH){sub 2}, were found within the inner zones of surface layers, and they must have nucleated in situ, indicating that Ag, Te, Sr, and Mo can be retained within the surface layer. The majority of the surface layer volume is composed of two morphologically and chemically different structures: one consists of well-crystallized fibrous smectite aggregates occurring along with cavities, the A-domain; and the other consists of poorly-crystallized regions containing needle-like smectite (montmorillonite) crystallites, a silica-rich amorphous matrix, and possibly ZrO{sub 2} particles, the B-domain.

Gong, W.L.; Ewing, R.C.; Wang, L.M. [Univ. of New Mexico, Albuquerque, NM (United States)] [and others

1995-12-31

409

Vapor-phase transport of explosives from buried sources in soils.  

PubMed

The fate and transport of explosives in the soil pore vapor spaces affects both the potential detection of buried ordnance by chemical sensors and vadose zone transport of explosives residues. The efficacy of chemical sensors and their potential usefulness for detecting buried unexploded ordnance (UXO) is difficult to determine without understanding how its chemical signatures are transported through soil. The objectives of this study were to quantify chemical signature transport through soils under various environmental conditions in unsaturated soils and to develop a model for the same. Flux chambers, large soil containers, and batch tests were used to determine explosives signature movement and process descriptors for model development. Low signatures were observed for explosives (2,4-dinitrotoluene, 2,6-dinitrotoluene, and 1,3-dinitrobenzene) under all environmental conditions. A diffusion model was used to describe the chemical transport mechanism in the soil pore air. The soil-air partition constant was treated as a fit parameter in the model owing to the uncertainty in its a priori estimation. The model predictions of the trends in experimental fluxes and the soil concentration were only marginal at best. It was concluded that better estimates of the partition constant are required for more accurate estimation of the chemical concentration at the soil-air interface. Chemical sensors will need to be very sensitive because of low signatures. However, this may result in many false alarms because of explosives residues not associated with UXO on firing ranges. Low explosives signatures also should result in insignificant air environmental exposures. PMID:15648390

Ravikrishna, Raghunathan; Valsaraj, Kalliat T; Price, Cynthia B; Brannon, James M; Hayes, Charolett A; Yost, Sally L

2004-12-01

410

Adding Water Vapor Radiometer Data to GPS Carrier-Phase Time Transfer.  

National Technical Information Service (NTIS)

The analysis of GPS carrier-phase time transfer 'GPSCPTT' data often requires that the zenith troposphere delay 'ZTD' be estimated at each site as a function of time. This is because the index of refraction of the troposphere varies rapidly. Both the ZTD ...

C. Hackman J. Levine

2004-01-01

411

HCl\\/H sub 2 O solid-phase vapor pressures and HCl solubility in ice  

Microsoft Academic Search

A study of the HCl\\/HâO binary system at low temperatures is presented, and applications to the polar stratosphere are discussed. A phase diagram constructed for low HCl partial pressures includes the tri- and hexahydrates as well as solid solutions of HCl in ice. Results of two experiments strongly suggest that the solubility of HCl in ice is low, less than

D. R. Hanson; K. Mauersberger

1990-01-01

412

Solar?powered soil vapor extraction for removal of dense nonaqueous phase organics from soil  

Microsoft Academic Search

Both surface and groundwater are threatened by buried waste at a number of sites because of subsurface plumes containing dense non?aqueous phase liquids (DNAPLs), hazardous metals, and radionuclides. In this work, a novel process is explored which represents an enhancement to thermal extraction methods as well as a mobile system that is suitable for remediation of remote sites. Solar radiation

Takashi Nakamura; Constance L. Senior; Elizabeth G. Burns; Milton D. Bell

2000-01-01

413

ADVERTISING MEDIA AND CIGARETTE DEMAND  

Microsoft Academic Search

ABSTRACTUsing state?level panel data for the USA spanning three decades, this research estimates the demand for cigarettes. The main contribution lies in studying the effects of cigarette advertising disaggregated across five qualitatively different groups. Results show cigarette demand to be near unit elastic, the income effects to be generally insignificant and border price effects and habit effects to be significant.

Rajeev K. Goel

2011-01-01

414

Cigarette Smoking and Dyspnea Perception  

Microsoft Academic Search

Cigarette smoking has been implicated as an important risk factor for the development of respiratory symptoms in adults. The relationship of dyspnea with cigarette smoking has been examined in smokers and ex-smokers and the beneficial effects of smoking cessation have been demonstrated. Recent studies reported that in subjects who smoke cigarettes the risk of developing respiratory symptoms is higher in

Elisabetta Rosi; Giorgio Scano

2004-01-01

415

Simultaneous quantification of jasmonic acid and salicylic acid in plants by vapor-phase extraction and gas chromatography-chemical ionization-mass spectrometry  

Microsoft Academic Search

Jasmonic acid and salicylic acid represent important signaling compounds in plant defensive responses against other organisms. Here, we present a new method for the easy, sensitive, and reproducible quantification of both compounds by vapor-phase extraction and gas chromatography-positive ion chemical ionization-mass spectrometry. The method is based on a one-step extraction, phase partitioning, methylation with HCl\\/methanol, and collection of methylated and,

Juergen Engelberth; Eric A Schmelz; Hans T Alborn; Yasmin J Cardoza; Juan Huang; James H Tumlinson

2003-01-01

416

Use of dissolved and vapor-phase gases to investigate methanogenic degradation of petroleum hydrocarbon contamination in the subsurface  

NASA Astrophysics Data System (ADS)

At many sites contaminated with petroleum hydrocarbons, methanogenesis is a significant degradation pathway. Techniques to estimate CH4 production, consumption, and transport processes are needed to understand the geochemical system, provide a complete carbon mass balance, and quantify the hydrocarbon degradation rate. Dissolved and vapor-phase gas data collected at a petroleum hydrocarbon contaminated site near Bemidji, Minnesota, demonstrate that naturally occurring nonreactive or relatively inert gases such as Ar and N2 can be effectively used to better understand and quantify physical and chemical processes related to methanogenic activity in the subsurface. In the vadose zone, regions of Ar and N2 depletion and enrichment are indicative of methanogenic and methanotrophic zones, and concentration gradients between the regions suggest that reaction-induced advection can be an important gas transport process. In the saturated zone, dissolved Ar and N2 concentrations are used to quantify degassing driven by methanogenesis and also suggest that attenuation of methane along the flow path, into the downgradient aquifer, is largely controlled by physical processes. Slight but discernable preferential depletion of N2 over Ar, in both the saturated and unsaturated zones near the free-phase oil, suggests reactivity of N2 and is consistent with other evidence indicating that nitrogen fixation by microbial activity is taking place at this site.

Amos, Richard T.; Mayer, K. Ulrich; Bekins, Barbara A.; Delin, Geoffrey N.; Williams, Randi L.

2005-02-01

417

Treatment of Produced Waters Using a Surfactant Modified Zeolite/Vapor Phase Bioreactor System  

SciTech Connect

This report summarizes work performed on this project from April 2004 through September 2004. Our previous work demonstrated that a polyurethane foam biofilter could successfully biodegrade the BTEX contaminants found in the SMZ regeneration waste gas stream. However, establishing the biomass on the polyurethane foam packing was relatively time consuming and daily recirculation of a concentrated nutrient solution was required for efficient operation of the foam biofilter. To simplify the start up and operating requirements of the biofilter system, a simple, compost-based biofilter was investigated for its ability to treat the BTEX contaminants generated during the SMZ regeneration process. The investigation of the compost biofilter was divided into three experimental phases that spanned 180 days of biofilter operation. During Phase 1, the biofilter was continuously supplied a BTEX-contaminated waste gas stream. During Phase 2, a series of periodic shutdown tests were conducted to assess how the biofilter responded when the BTEX feed was discontinued for periods ranging from 1 day to 2.8 days. The Phase 3 experiments focused on determining how the biofilter would handle periodic spikes in inlet BTEX concentration as would be expected when it is coupled with an SMZ column. Results from the continuous feed (Phase 1) experiments demonstrated that the compost biofilter could maintain BTEX removals of greater than 98% within two weeks of startup. Results of the shutdown experiments indicated that benzene removal was the most sensitive to interruptions in the BTEX feed. Nevertheless, the BTEX removal efficiency exceeded 95% within 6 hours of reestablishing the BTEX feed to the biofilter. When the biofilter was subjected to periodic spikes in BTEX concentration (Phase 3), it was found that the total BTEX removal efficiency stabilized at approximately 75% despite the fact that the biofilter was only fed BTEX contaminants 8 hours per day. Finally, the effects of nutrient supply and EBCT on compost biofilter performance were also investigated. The bioreactor maintained greater than 95% removal efficiency for over 40 days without an additional supply of nutrients when a 10X concentrated HCMM was mixed with the compost packing at the beginning of the experiments. Results also suggest that an EBCT greater than 30 seconds is required to maintain high BTEX removal efficiencies in the compost biofilter system.

Lynn E. Katz; Kerry A. Kinney; R. S. Bowman; E. J. Sullivan

2004-09-11

418

19 CFR 11.2a - Release from Customs custody without payment of tax on cigars, cigarettes and cigarette papers...  

Code of Federal Regulations, 2013 CFR

...without payment of tax on cigars, cigarettes and cigarette papers...without payment of tax on cigars, cigarettes and cigarette papers...cigarettes, and cigarette papers and tubes...applicable internal revenue tax upon...

2013-04-01

419

Enhanced reflection via phase compensation from anomalous dispersion in atomic vapor  

SciTech Connect

The phase compensation mechanism induced by anomalous dispersion in the reflection process of four-wave mixing (or reflection from a grating) in a three-level system is investigated, where the four wave vectors do not match in vacuum. An efficiency of the reflected signal of as high as 43% from a hot atomic cell of Cs is observed. The maximum reflection occurs when the frequency of the probe beam (and consequently the frequency of the reflected signal) is slightly red detuned from the transition frequency, which is attributed to the phase compensation from the steep anomalous dispersion accompanied with a strong probe absorption. The dependences of the efficiency on the angle between the coupling and probe lights, on the intensity of the coupling, field and on atomic density are studied. A theoretical model is presented and it is in good agreement with the experimental results.

Zhang Junxiang; Zhou Haitao [State Key Laboratory of Quantum Optics and Quantum Optics Devices, Institute of Opto-Electronics, Shanxi University, Taiyuan 030006 (China); Wang Dawei [Beijing Computational Science Research Center, Beijing 100084 (China); Zhu Shiyao [State Key Laboratory of Quantum Optics and Quantum Optics Devices, Institute of Opto-Electronics, Shanxi University, Taiyuan 030006 (China); Beijing Computational Science Research Center, Beijing 100084 (China); Department of Physics, Hong Kong Baptist University (Hong Kong)

2011-05-15

420

Metalorganic vapor phase epitaxy of II-VI compound semiconductors and diluted magnetic semiconductors  

Microsoft Academic Search

II-VI compound semiconductors and diluted magnetic semiconductors (DMS) were grown in a vertical stagnation flow MOVPE reactor. The reactor was equipped with a split inlet configuration to inhibit parasitic, gas-phase prereactions. Films of ZnSe and ZnSSe were routinely deposited and characterized by standard techniques. Single-crystal line films were deposited at 666 K and 120 Torr with a growth rate of

John Douglas Peck III

1999-01-01

421

Development of novel adsorbents for the control of vapor- phase mercury emissions  

NASA Astrophysics Data System (ADS)

Efficient sulfur-impregnated activated carbon-based (SIAC) sorbents for elemental mercury vapors were developed and evaluated in this study. The key parameters of the impregnation protocol included impregnation temperature and initial sulfur to carbon ratio (SCR). Gas constituents and temperature were the key process parameters studied for their impact on sorbent performance. Impregnation temperature is the major impregnation parameter that dominated the performance of SIACs. Performance deteriorated quickly as the impregnation temperature was lowered below 400°C. Higher impregnation temperatures facilitated the presence of more active short-chain S molecules, larger adsorbent surface area, greater fraction of meso-pores, and stronger sulfur-carbon bonding. SCR showed moderate impact on mercury uptake with a 50% decrease in sorbent capacity from highest SCR (4:1) to lowest SCR (1:2). Impact of gas constituents was investigated individually. CO2 (5 and 15%) behaved as inert gas and did not change the performance of SIAC. Also, trace amount of SO2 (300 ppm) and NO (500 ppm) did not alter its performance. Thermogravimetric Analysis showed that micro-structure of SIAC was unchanged after contacting trace pollutants. Low O2 concentration (3%) did not change the performance of SIAC, while high O2 concentration (6% and 9%) increased its capacity by 16% and 30%, respectively. It is postulated that SIAC catalyzed the formation of HgO in the presence of high O2 concentrations. High moisture concentration (10%) decreased SIAC's capacity by 25% while low moisture concentration (5%) showed no impact. It was assumed that water blocked the entrances to the active sites of carbon. H2 formation and hydrogen bonding could have also retarded mercury-sulfur reaction. SIAC's performance was negligible at 250 or 400°C due to the exothermic nature of Hg and S reaction, while its capacity at 140°C increased by 14% as smaller sorbent particle size (170 x 230) was used instead of 60 x 80. The fate of spent SIAC was assessed using a modified toxicity characteristics leaching procedure (TCLP). Mercury concentration in all leachates was below the TCLP limit (0.2 mg/L), and no mercury loss was found from SIAC. It is suggested that SIAC can be treated as non- hazardous wastes.

Liu, Wei

422

A new analytical methodology for a fast evaluation of semi-volatile polycyclic aromatic hydrocarbons in the vapor phase downstream of a diesel engine particulate filter.  

PubMed

A new sampling method was developed to collect vapor-phase polycyclic aromatic compounds (PAHs) downstream of a diesel engine equipped with a diesel particulate filter (DPF). This configuration allowed us to collect separately the particulate phase, which was trapped inside the DPF, and the vapor phase, which was sampled downstream of the DPF. PAHs, which were not predominantly absorbed into the poor organic fraction of the diesel soot, but were rather physically sorbed on high energetic adsorption sites, should be extracted using very drastic extraction conditions Microwave-assisted extraction using solvent mixtures composed of pyridine and diethylamine were used to desorb particulate PAHs, and the total PAH amounts corresponded to a very low value, i.e., 8 ?g g?¹ or 0.24 ?g km?¹, with a predominance of low weight PAHs. For collection of the vapor phase, gas bubbling in an aqueous medium was preferred to conventional methods, e.g., trapping on solid sorbents, for several reasons: aqueous trapping allowed us to use a solid phase enrichment process (SPE) that permitted PAH sampling at the sub-picogram levels. Consequently, low volume sampling was possible even if the sampling duration was very short (20 min). Additionally, the amount of time saved for the analysis was considerable when coupling SPE to the analytical system (liquid chromatography with fluorimetric detection). Solvent consumption for the overall sampling and analytical processes was also drastically reduced. Experiments on a diesel engine showed that vapor phase samples collected downstream of the DPF contained all of the 15 target priority PAHs, even the heaviest ones. The total vapor-phase PAH amount was 6.88 ?g N m?³ or 10.02 ?g km?¹, which showed that the gaseous fraction contains more PAHs than the particulate fraction. Partitioning coefficients (K(p)) were estimated showing the predominance in the vapor phase of all the PAHs. However, the DPF technology effects a considerable decrease in the total PAH emission when compared to non-equipped diesel vehicles. PMID:21227441

Portet-Koltalo, F; Preterre, D; Dionnet, F

2010-12-23

423

Correlation-enhanced phase-sensitive Raman scattering in atomic vapors  

NASA Astrophysics Data System (ADS)

We theoretically propose a method to enhance Raman scattering by injecting a seeded light field which is correlated with the initially prepared atomic spin wave. Such a light-atom correlation leads to an interference in the Raman scattering. The interference is sensitive to the relative phase between the seeded light field and initially prepared atomic spin wave. For constructive interference, the Raman scattering is greatly enhanced. Such an enhanced Raman scattering may find applications in quantum information, nonlinear optics, and optical metrology due to its simplicity.

Yuan, Chun-Hua; Chen, L. Q.; Ou, Z. Y.; Zhang, Weiping

2013-05-01

424

Advertising and Cigarette Consumption  

Microsoft Academic Search

The authors examine two questions that are relevant to current policy issues: (1) is there a positive response of aggregate demand to advertising? (2) what is the reaction of consumers to government health warnings and media policy? The results support the hypothesis that advertising increases aggregate demand for cigarettes. However, the advent of health warnings and media policies seems to

Khosrow Doroodian; Barry J. Seldon

1991-01-01

425

Sample introduction with graphite furnace electrothermal vaporization into an inductively coupled plasma: effects of streaming conditions and gaseous phase additives  

Microsoft Academic Search

A laboratory-made graphite furnace electrothermal vaporizer (GF-ETV) was applied with two alternative versions of the exit part. In one of the versions the vapor streams upward through the transverse hole of the longitudinally heated tube (upward streaming: UPS), while with the other version the vapor streams toward one of the ends of the tube (end-on streaming: ENS). Volatile (Cd, Zn)

Tibor Kántor

2000-01-01

426

Advertising media and cigarette demand.  

PubMed

Using state-level panel data for the USA spanning three decades, this research estimates the demand for cigarettes. The main contribution lies in studying the effects of cigarette advertising disaggregated across five qualitatively different groups. Results show cigarette demand to be near unit elastic, the income effects to be generally insignificant and border price effects and habit effects to be significant. Regarding advertising effects, aggregate cigarette advertising has a negative effect on smoking. Important differences across advertising media emerge when cigarette advertising is disaggregated. The effects of public entertainment and Internet cigarette advertising are stronger than those of other media. Anti-smoking messages accompanying print cigarette advertising seem relatively more effective. Implications for smoking control policy are discussed. PMID:22167909

Goel, Rajeev K

2011-01-01

427

Preparation of a Freestanding AlN Substrate from a Thick AlN Layer Grown by Hydride Vapor Phase Epitaxy on a Bulk AlN Substrate Prepared by Physical Vapor Transport  

NASA Astrophysics Data System (ADS)

The structural and optical quality of a freestanding AlN substrate prepared from a thick AlN layer grown by hydride vapor phase epitaxy (HVPE) on a bulk (0001)AlN substrate prepared by physical vapor transport (PVT) were investigated. The prepared HVPE-AlN substrate was crack- and stress-free. High-resolution X-ray diffraction ?-rocking curves of symmetric (0002) and skew-symmetric (10\\bar{1}1) reflections had small full widths at half maximum (FWHMs) of 31 and 32 arcsec, respectively. Deep-ultraviolet optical transparency of the HVPE-AlN substrate was higher than that of the PVT-AlN substrate, which was related to lower concentrations of C, O impurities, and Al vacancy.

Kumagai, Yoshinao; Kubota, Yuki; Nagashima, Toru; Kinoshita, Toru; Dalmau, Rafael; Schlesser, Raoul; Moody, Baxter; Xie, Jinqiao; Murakami, Hisashi; Koukitu, Akinori; Sitar, Zlatko

2012-05-01

428

Catalyst-assisted hydride vapor phase epitaxy of GaN nanowires: exceptional length and constant rod-like shape capability.  

PubMed

The hydride vapor phase epitaxy (HVPE) process exhibits unexpected properties when growing GaN semiconductor nanowires (NWs). With respect to the classical well-known methods such as metal organic vapor phase epitaxy and molecular beam epitaxy, this near-equilibrium process based on hot wall reactor technology enables the synthesis of nanowires with a constant cylinder shape over unusual length. Catalyst-assisted HVPE shows a record short time process (less than 20 min) coupled to very low precursor consumption. NWs are grown at a fast solidification rate (50 ?m h(-1)), facilitated by the high decomposition frequency of the chloride molecules involved in the HVPE process as element III precursors. In this work growth temperature and V/III ratio were investigated to determine the growth mechanism which led to such long NWs. Analysis based on the Ni-Ga phase diagram and the growth kinetics of near-equilibrium HVPE is proposed. PMID:22983695

Lekhal, K; Avit, G; André, Y; Trassoudaine, A; Gil, E; Varenne, C; Bougerol, C; Monier, G; Castelluci, D

2012-09-14

429

Liquid-vapor phase diagram and surface properties in oppositely charged colloids represented by a mixture of attractive and repulsive Yukawa potentials.  

PubMed

The liquid-vapor phase diagrams of equal size diameter ? binary mixtures of screened potentials have been reported for several ranges of interaction using Monte Carlo simulation methods [J. B. Caballero, A. M. Puertas, A. Fern?andez-Barbero, F. J. de las Nieves, J. M. Romero-Enrique, and L. F. Rull, J. Chem. Phys. 124, 054909 (2006); A. Fortini, A.-P. Hynninen, and M. Dijkstra, J. Chem. Phys. 125, 094502 (2006)]. Both works report controversial results about the stability of the phase diagram with the inverse Debye screening length ?. Caballero found stability for values of ?? up to 20 while Fortini reported stability for ?? up to 20 while Fortini reported stability for ?? ? 4. In this work a spinodal decomposition process where the liquid and vapor phases coexist through an interface in a slab geometry is used to obtain the phase equilibrium and surface properties using a discontinuous molecular dynamics simulations for mixtures of equal size particles carrying opposite charge and interacting with a mixture of attractive and repulsive Yukawa potentials at different values of ??. An crude estimation of the triple point temperatures is also reported. The isothermal-isobaric method was also used to determine the phase stability using one phase simulations. We found that liquid-vapor coexistence is stable for values of ?? > 20 and that the critical temperatures have a maximum value at around ?? = 10, in agreement with Caballero et al. calculations. There also exists a controversy about the liquid-vapor envelope stability of the pure component attractive Yukawa model which is also discussed in the text. In addition, details about the equivalence between continuous and discontinuous molecular dynamics simulations are given, in the Appendix, for Yukawa and Lennard-Jones potentials. PMID:23406133

Chapela, Gustavo A; del Río, Fernando; Alejandre, José

2013-02-01

430

19 CFR 159.5 - Cigars, cigarettes, and cigarette papers and tubes.  

Code of Federal Regulations, 2013 CFR

... LIQUIDATION OF DUTIES General Provisions § 159.5 Cigars, cigarettes, and cigarette papers and tubes. The internal revenue taxes imposed on cigars, cigarettes, and cigarette papers and tubes under section 5701 or 7652,...

2013-04-01

431

Patterning and overgrowth of nanostructure quantum well wire arrays by LP-MOVPE (low pressure Metalorganic Vapor Phase Epitaxy)  

SciTech Connect

Nanometer scale GaAs Quantum Well Wire (QWW) arrays with lateral dimensions in the range of 10--70 nm and a period of 200 nm have been fabricated in the GaAs/AlGaAs system using x-ray nanolithography patterning and overgrowth by a low pressure Metalorganic Vapor Phase Epitaxy (LP-MOVPE) technique. The QWW structures were either fabricated by post-growth patterning of a thin GaAs film on a AlGaAs-coated substrate followed by AlGaAs deposition, or by continuous in-situ deposition of a GaAs/AlGaAs QWW structure on a prepatterned GaAs substrate. Although cross-sectional transmission electron microscopy showed no structural defects in either QWW fabrication process, photoluminescence (PL) was only observed in the in-situ-deposited structures. Strong polarization dependence of the PL peak with respect to wire orientation has been confirmed and evidence of lateral confinement was observed. 17 refs., 4 figs.

Karam, N.H.; Mastrovito, A.; Haven, V. (Spire Corp., Bedford, MA (USA)); Ismail, K. (International Business Machines Corp., Yorktown Heights, NY (USA). Thomas J. Watson Research Center); Pennycook, S. (Oak Ridge National Lab., TN (USA)); Smith, H.I. (Massachusetts Inst. of Tech., Cambridge, MA (USA). Dept. of Electrical Engineering and Computer Science)

1990-06-01

432

Catalyst Temperature Dependence of NH3 Decomposition for InN Grown by Metal Organic Vapor Phase Epitaxy  

NASA Astrophysics Data System (ADS)

In this paper, we report an independent catalyst heating system on the Pt-catalyst metal organic vapor phase epitaxy (MOVPE) for Indium nitride (InN) growth, and the dependence of the NH3 decomposition rate on the Pt catalyst temperature (RT to 1000 °C) using a quadrupole mass spectrometer (Q-MS). When the catalyst temperature is increased above the growth temperature of InN, the NH3 decomposition rate is enhanced. The grain size of InN becomes larger and the full width at half maximum (FWHM) of the X-ray rocking curve (XRC) was drastically decreased. The increase of N atoms results in the incorporation of nitrogen into the InN layer and thus improves the crystal quality of InN. However, active H increases sharply when the catalyst heater temperature is over about 850 °C. Therefore, a great improvement in the crystal quality of InN film is expected by optimizing the growth condition including a catalyst temperature not exceeding 850 °C.

Sugita, Kenichi; Hironaga, Daizo; Mihara, Akihiro; Hashimoto, Akihiro; Yamamoto, Akio

2013-08-01

433

Vapor-phase toxicity of Derris scandens Benth.-derived constituents against four stored-product pests.  

PubMed

The vapor-phase toxicity of Derris scandens Benth.-derived constituents was evaluated against four stored-product pests ( Callosobruchus chinensis L., Sitophilus oryzae L., Rhyzopertha dominica L., and Tribolium castaneum H.) using fumigation bioassays and compared to those of commonly used insecticides. The structures of all constituents of were characterized by spectroscopic analyses [nuclear magnetic resonance (NMR) and mass spectrometry]. The sensitivity of the test insect to compounds varied with exposure time, concentration, and insect species. Over 100% mortality after 24 h was achieved with the compounds osajin (2), scandinone (5), sphaerobioside (8), and genistein (9) against all of the test insects, while laxifolin (3) and lupalbigenin (4) showed 100% mortality after 72 h against T. csataneum and R. dominica . Scandenone (1), scandenin A (6), and scandenin (7) were less effective. Among the insects, C. chinensis , S. oryzae , and R. dominica were more susceptible to the treatments, whereas T. castaneum was less susceptible. The results of fumigation tests indicated that compounds from D. scandens whole plant extract are potential candidates to control stored-product pests. PMID:21314138

Hymavathi, Atmakur; Devanand, Peta; Suresh Babu, Katragadda; Sreelatha, Thonthula; Pathipati, Usha Rani; Madhusudana Rao, Janaswamy

2011-02-11

434

Automation for monitoring of the refractive index profile of vapor-phase-deposited soot preforms for optical fiber  

SciTech Connect

The vapor-phase axial deposition process is currently one of the most advantageous methods to produce preforms for optical fibers, due to its high efficiency and reduced production cost. However, this method has great difficulty in determining the refractive index profile, since it is influenced by too many process parameters. In this work, an automation system to determine the refractive index profile by monitoring the preform deposition surface profile during the soot preform deposition stage is presented. Based on a previous study that showed a strong correlation between these two profiles, an automation system was developed in LABVIEW to monitor the deposition surface profile during the preform deposition stage in order to estimate the preform germanium doping profile and refractive index profile, as well as a theoretical study to develop this system in order to minimize the performance impairment. As a result, not only preforms with a predetermined index profile were produced but also a reduction in production cost was obtained by decreasing the number of preform rejects.

Santos, J.S. dos; Ono, E.; Suzuki, C.K. [Laboratory of Integrated Quartz Cycle (LIQC), Faculty of Mechanical Engineering, Department of Materials Engineering, State University of Campinas, P.O. Box 6122, 13083-970, Campinas-Sao Paulo (Brazil)

2006-05-15

435

Metal-organic vapor phase epitaxy of crystallographically oriented MnP magnetic nanoclusters embedded in GaP(001)  

NASA Astrophysics Data System (ADS)

Hybrid ferromagnetic-semiconductor GaP:MnP thin films were grown at 650 °C by metal-organic vapor phase epitaxy on GaP(001) using trimethylgallium, tertiarybutylphosphine, and methyl cyclopentadienyl manganese tricarbonyl (MCTMn). Overall Mn concentrations in the hybrid films, determined by Rutherford backscattering spectrometry, were found to be nearly proportional to the MCTMn precursor gas flow rate and ranged from 2 to 3.5 at. %. Cross-sectional transmission electron microscopy (TEM) analyses revealed the presence of a homogeneous distribution of 15-30 nm wide nanoclusters in a dislocation-free GaP matrix that is fully coherent with the substrate. The nanocluster facets are predominantly aligned along the (220) planes of the GaP matrix and selected-area electron diffraction patterns in TEM indicate that the nanoclusters are coherent (or semicoherent) with the single-crystal GaP matrix. The Mn:P composition ratio in the nanoclusters was determined to be 1.00+/-0.05 from parallel electron energy loss spectroscopy analyses. Increasing the MCTMn flow rate during film growth resulted in an increased concentration of MnP nanoclusters in the epilayer while their dimensions remained virtually unchanged. Magnetometric characterization indicates a ferromagnetic order, with a Curie temperature of about 294 K, originating from the MnP clusters.

Lambert-Milot, S.; Lacroix, C.; Ménard, D.; Masut, R. A.; Desjardins, P.; Garcia-Hernandez, M.; de Andres, A.

2008-10-01

436

Laser induced fluorescence monitoring of the transport of small organic molecules in an organic vapor phase deposition system  

NASA Astrophysics Data System (ADS)

Laser-induced fluorescence is employed for the accurate and real-time in-situ monitoring of the concentration of organic molecules in an organic vapor phase deposition (OVPD) chamber. We investigate the transport dynamics of organic species in a hot N2 carrier gas from the evaporation source to the substrate. Based on the time-dependent concentration of organic molecules obtained from their fluorescence intensity near the substrate, we find that carrier gas transport is accurately described by Poiseuille flow. The interplay between convective and diffusive forces gives rise to dispersion of organic molecules in the carrier gas, resulting in the development of plug flow as described by Taylor-Aris theory. Retention of molecules in chamber dead volumes delays transport and introduces tailing of the concentration transients. Our study indicates how OVPD system design and operating conditions can be optimized to limit the duration of transport transients, ultimately leading to precise control over the growth of complex multilayer thin film structures.

Rolin, Cedric; Vartanian, Garen; Forrest, Stephen R.

2012-12-01

437

Crystal growth via metal-organic vapor phase epitaxy of quantum-cascade-laser structures composed of multiple alloy compositions  

NASA Astrophysics Data System (ADS)

Metal-organic vapor phase epitaxy (MOVPE) is suitable for the growth of superlattice (SL) structures composed of multiple alloy compositions. By taking advantage of this flexibility of MOVPE, we have demonstrated the crystal growth of varying-layer-composition, 4.8 ?m-emitting, tapered active-region quantum cascade lasers (TA-QCLs), for which the barriers in the active region gradually increase in height from the injection barrier to the exit barrier, resulting, in turn, in a dramatic suppression of carrier leakage. One stage of the TA-QCL structure consists of seven different alloy compositions. The composition and growth rate of each layer are calibrated by using high-resolution X-ray-diffraction rocking curves. Very narrow mid-infrared absorption peaks (˜30 meV full width at half-maximum) have been achieved, at room temperature, from 20 periods of In0.6Ga0.4As/Al0.56In0.44As SL structures, at the designed wavelength. Transmission-electron-microscope analysis of the QCL structure confirms extremely accurate thickness control and layer uniformity for layers as thin as 1 nm.

Shin, Jae Cheol; Mawst, Luke J.; Botez, Dan

2012-10-01

438

Development of a modified medium pressure microwave vapor-phase digestion method for difficult to digest organic samples.  

PubMed

A previously developed microwave heated vapor-phase digestion method for biological samples was modified to enable digestion of difficult to digest organic samples. Organic samples containing ca. 100 mg of organic carbon were digested using volume calibrated quartz inserts inside second generation type medium pressure microwave vessels. As digestion reagents, 98% sulfuric acid, 70% nitric acid and 30% hydrogen peroxide were used. The accuracy of the method was tested with six certified reference materials. Elements Ca, Fe, K, Na, Mg, P and Zn were determined from NIST-SRM 8433 corn bran. Elements Al, Fe, Cd, Cu, and Zn were determined from NRCC DOLT-2 dogfish liver. The element Cd was determined from IRMM-VDA Cd in polyethylene No. 001-004 reference materials. These elements were determined from digested samples by ICP-OES. The results were close or within certified limits. The modified method could digest nearly all the materials tested, including the above mentioned reference materials, 2-nitrobenzoic acid (2-NBA), 4-NBA and copper(II) phthalosyanine-3, 4',4',4'-tetrasulfonic acid tetrasodium salt (CPS). The method could not digest 3-NBA. PMID:12625563

Eilola, K; Perämäki, P

2003-02-01

439

Metal--Organic Vapor Phase Epitaxy Growth of Embedded Gallium Nitride Nanocolumn for Reduction in Dislocation Density  

NASA Astrophysics Data System (ADS)

The use of nanocolumn crystals is thought to be effective in producing a low-dislocation-density GaN layers. In this paper, we propose a metal--organic vapor phase epitaxial (MOVPE) growth method for producing uniform GaN nanocolumns using deep through-holes in a thick SiO2 selective growth mask. A SiO2 film with a thickness of 500 nm was deposited by sputtering on an AlN buffer layer/SiC substrate. A nanoimprinting technique was applied to produce dot openings. Then, dry etching with CF4 gas was carried out to form deep through-holes in the SiO2 film. In the second MOVPE growth, individual GaN nanocolumns coalesced into a planarized GaN layer, after thinning the SiO2 mask to 100 nm. A cathode-luminescence image of the GaN layer on a GaN nanocolumn template shows a low dislocation density of 1.3× 108 cm-2, while that of a GaN layer directly grown on an AlN buffer layer shows a dislocation density of 9.4× 108 cm-2.

Umeda, Shinya; Kato, Takahiro; Kitano, Tsukasa; Kondo, Toshiyuki; Matsubara, Hiroyuki; Kamiyama, Satoshi; Takeuchi, Tetsuya; Iwaya, Motoaki; Akasaki, Isamu

2013-08-01

440

Formation of magnetic nanocolumns during vapor phase deposition of a metal-polymer nanocomposite: Experiments and kinetic Monte Carlo simulations  

NASA Astrophysics Data System (ADS)

Metal-polymer nanocomposites have been investigated extensively during the last years due to their interesting functional applications. They are often produced by vapor phase deposition which generally leads to the self-organized formation of spherical metallic nanoparticles in an organic matrix, while nanocolumns are only obtained under very specific conditions. Experiments [Greve et al. Appl. Phys. Lett. 88, 123103 (2006)] have shown that co-evaporation of the metallic and organic components in a simple single-step process can give rise to the formation of ultrahigh-density Fe-Ni-Co nanocolumnar structures embedded in a fluoropolymer matrix. Here we present a kinetic Monte Carlo approach which is based on a new model involving the depression of the melting point on the nanoscale and a critical nanoparticle size required for solidification. In addition we present new experimental results on the formation of Fe-Ni-Co nanocolumns in a Teflon AF matrix via co-evaporation down to a deposition temperature of -70 °C and also report the magnetic properties of the nanocolumns. The simulations provide a detailed understanding of the transition from spherical cluster growth to formation of elongated structures and are in good agreement with the experiments.

Rosenthal, L.; Greve, H.; Zaporojtchenko, V.; Strunskus, T.; Faupel, F.; Bonitz, M.

2013-07-01

441

Characteristics of GaSb and GaInSb layers grown by metalorganic vapor phase epitaxy  

SciTech Connect

GaInSb and GaSb layers have been grown on GaSb and GaAs substrates using metalorganic vapor phase epitaxy (MOVPE) with trimethylgallium, trimethylindium and trimethylantimony as the sources. As grown layers are p type with the carrier concentration in the mid 10{sup 16} cm{sup {minus}3} range. N type layers are grown using diethyltellurium as the Te source. Incorporation of Te in high concentration showed compensation and secondary ion mass spectrometry (SIMS) result showed that only 2.5% of Te are active when 2 {times} 10{sup 19} cm{sup {minus}3} of Te was incorporated. The carrier concentration measured in n type samples increases as the temperature is lowered. This is explained by the presence of second band close to the conduction band minima. Silane which is a common n type dopant in GaAs and other III-V systems is shown to behave like p type in GaInSb. P-n junction structures have been grown on GaSb substrates to fabricate TPV cells.

Ehsani, H.; Bhat, I.; Hitchcock, C.; Borrego, J.; Gutmann, R. [Rensselaer Polytechnic Inst., Troy, NY (United States)

1995-07-01

442

Nanotribology of a Vapor Phase Lubricant: A Quartz Crystal Microbalance Study of Tricresylphosphate (TCP) Reactive Films on Iron and Chrome  

NASA Astrophysics Data System (ADS)

Vapor phase lubrication is receiving increased attention as a high temperature lubrication technique. We show how a quartz crystal microbalance (QCM) under ultra-high vacuum can be used to characterize reactions and film formation of tricresylphosphate (TCP) on both chromium and iron surfaces. The effect of oxygen on film formation was also studied. Shifts in QCM resonant frequency and amplitude are functions of the elastic and viscous character of the chemically reacted films. At both room temperature and elevated temperatures, TCP reacts to a greater extent on iron surfaces than on chromium surfaces. At 300oC, the extreme frequency and amplitude shifts seen for oxygen and TCP on iron are interpreted as the formation of a viscoelastic ‘polymer-solid matrix’ on the iron surface, to which we ascribe its tribological benefits. The absence of significant frequency and amplitude shifts for chromium indicates its lack of reactivity. These findings corroborate TCP’s known ability to lubricate iron, but not chrome.

Jaye, Cherno; Abdelmaksoud, Mohammed; Bender, Jonathan; Krim, Jacqueline

2002-03-01

443

Remediation of nonaqueous phase liquid polluted sites using surfactant-enhanced air sparging and soil vapor extraction.  

PubMed

A two-dimensional laboratory sand tank was installed to study the remediation efficiency of surfactant-enhanced air sparging (-SEAS) coupled with soil vapor extraction (SVE) in nonaqueous phase liquid (NAPL) polluted sites. During initial stages of remediation, it was more reasonable to use conventional air sparging coupled with SVE. When most free NAPLs were removed and contaminant removal rate was maintained at a relatively low level, surfactant was added to the groundwater. During enhanced remediation, lower interfacial tension caused residual NAPLs in the porous media to slightly migrate, making the downstream contaminant concentration somewhat higher. The polluted area, however, was not more enlarged than before. The decrease in surface tension resulted in increased air saturation in the groundwater and the extent of the air influence zone. After 310 hours, 78.7% of the initial chlorobenzene mass had volatilized, 3.3% had migrated out of the sand profile, 17.5% was in the vadose zone, and 0.5% remained in the groundwater, thus revealing that SEAS/SVE can effectively improve the remediation of NAPL polluted sites. PMID:23472329

Qin, Chuan-Yu; Zhao, Yong-Sheng; Su, Yan; Zheng, Wei

2013-02-01

444

Record high-aspect-ratio GaAs nano-grating lines grown by Hydride Vapor Phase Epitaxy (HVPE)  

NASA Astrophysics Data System (ADS)

Nanometric-width GaAs grating lines showing high aspect (height/width) ratio of up to 30, without roughness or shape deviation are reported. They were obtained by HVPE, capitalizing on the near-equilibrium nature of this epitaxial technique. HVPE rapid decomposition of GaCl growth precursors leads to immediate reactivity of the growth reaction to an increase or decrease of the supersaturation of the vapor phase. HVPE growth is also governed by surface kinetics: the morphologies are controlled by the intrinsic growth anisotropy of the crystals. By manipulating surface kinetics and exploiting the fast reactivity of the system, it is demonstrated that HVPE allows to benefit from an enhanced growth anisotropy favoring vertical growth of nanometer-scale grating lines. Unique high-aspect ratios are obtained in one-step short growth time (20 min), capitalizing upon the main advantage of the bottom-up approach: the structures are defined by their crystalline properties with no scattering defects as typically introduced by techniques involving dry etching. The role of surface kinetics and mass transport at the nanometer scale is discussed.

Gil, E.; André, Y.; Ramdani, M. R.; Fontaine, C.; Trassoudaine, A.; Castelluci, D.

2013-10-01

445

Electron Transport in a High Mobility Free-Standing GaN Substrate Grown by Hydride Vapor Phase Epitaxy  

NASA Astrophysics Data System (ADS)

We studied electron transport properties in a high quality free-standing GaN grown by hydride vapor phase epitaxy. The GaN, with a thickness of more than 200 ?m, was lifted off the sapphire substrate and mechanically polished. At room temperature the carrier density is 1.3x10^16cm-3 and the Hall mobility is 1200 cm^2/V-s, which is the highest reported electron mobility for GaN with a wurtzite structure. Transport properties are studied using a van der Pauw geometry in a temperature range of 20 to 300 K and in magnetic fields up to 8 Tesla. Electron mobility is found to increase at lower temperatures with a peak mobility of 7400 cm^2/V-s at 48 K. The carrier density decreases exponentially at temperatures below 80 K with an activation energy of 28 meV. The electron transport measurements were used to examine the contributions of different scattering mechanisms. Numerical solution of the Boltzmann transport equation was carried out, including non-parabolic conduction bands and wavefunction admixture, along with lattice scattering and ionized-impurity scattering. LO and TO phonon energies were determined by Raman spectroscopy.