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Sample records for vapor phase cigarette

  1. Glass fibers and vapor phase components of cigarette smoke as cofactors in experimental respiratory tract carcinogenesis

    SciTech Connect

    Feron, V.J.; Kuper, C.F.; Spit, B.J.; Reuzel, P.G.; Woutersen, R.A.

    1985-01-01

    Syrian golden hamsters were given intratracheal instillations of glass fibers with or without BP suspended in saline, once a fortnight for 52 weeks; the experiment was terminated at week 85. No tumors of the respiratory tract were observed in hamsters treated with glass fibers alone. There was no indication that glass fibers enhanced the development of respiratory tract tumors induced by BP. In another study Syrian golden hamsters were exposed to fresh air or to a mixture of 4 major vapor phase components of cigarette smoke, viz. isoprene (800----700 ppm), methyl chloride (1000----900 ppm), methyl nitrite (200----190 ppm) and acetaldehyde (1400----1200 ppm) for a period of at most 23 months. Some of the animals were also given repeated intratracheal instillations of BP or norharman in saline. Laryngeal tumors were found in 7/31 male and 6/32 female hamsters exposed only to the vapor mixture, whereas no laryngeal tumors occurred in controls. The tumor response of the larynx most probably has to be ascribed entirely to the action of acetaldehyde. Simultaneous treatment with norharman or BP did not affect the tumor response of the larynx. Acetaldehyde may occur in the vapor phase of cigarette smoke at levels up to 2000 ppm. Chronic inhalation exposure of rats to acetaldehyde at levels of 0 (controls), 750, 1500 or 3000----1000 ppm resulted in a high incidence of nasal carcinomas, both squamous cell carcinomas of the respiratory epithelium and adenocarcinomas of the olfactory epithelium. It was discussed that acetaldehyde may significantly contribute to the induction of bronchogenic cancer by cigarette smoke in man.

  2. Levels of selected carcinogens and toxicants in vapor from electronic cigarettes

    PubMed Central

    Lukasz, Goniewicz Maciej; Jakub, Knysak; Michal, Gawron; Leon, Kosmider; Andrzej, Sobczak; Jolanta, Kurek; Adam, Prokopowicz; Magdalena, Jablonska-Czapla; Czeslawa, Rosik-Dulewska; Christopher, Havel; Peyton, Jacob; Neal, Benowitz

    2014-01-01

    Significance Electronic cigarettes, also known as e-cigarettes, are devices designed to imitate regular cigarettes and deliver nicotine via inhalation without combusting tobacco. They are purported to deliver nicotine without other toxicants and to be safer alternative to regular cigarettes. However, little toxicity testing has been performed to evaluate the chemical nature of vapor generated from e-cigarettes. The aim of this study was to screen e-cigarette vapors for content of four groups of potentially toxic and carcinogenic compounds: carbonyls, volatile organic compounds, nitrosamines, and heavy metals. Materials and methods Vapors were generated from 12 brands of e-cigarettes and the reference product, the medicinal nicotine inhaler, in controlled conditions using a modified smoking machine. The selected toxic compounds were extracted from vapors into a solid or liquid phase and analyzed with chromatographic and spectroscopy methods. Results We found that the e-cigarette vapors contained some toxic substances. The levels of the toxicants were 9 to 450 times lower than in cigarette smoke and were, in many cases, comparable to trace amounts found in the reference product. Conclusions Our findings are consistent with the idea that substituting tobacco cigarettes with electronic cigarettes may substantially reduce exposure to selected tobacco-specific toxicants. E-cigarettes as a harm reduction strategy among smokers unwilling to quit warrants further study. PMID:23467656

  3. Automation of the in vitro micronucleus and chromosome aberration assay for the assessment of the genotoxicity of the particulate and gas-vapor phase of cigarette smoke.

    PubMed

    Roemer, Ewald; Zenzen, Volker; Conroy, Lynda L; Luedemann, Kathrin; Dempsey, Ruth; Schunck, Christian; Sticken, Edgar Trelles

    2015-01-01

    Total particulate matter (TPM) and the gas-vapor phase (GVP) of mainstream smoke from the Reference Cigarette 3R4F were assayed in the cytokinesis-block in vitro micronucleus (MN) assay and the in vitro chromosome aberration (CA) assay, both using V79-4 Chinese hamster lung fibroblasts exposed for up to 24?h. The Metafer image analysis platform was adapted resulting in a fully automated evaluation system of the MN assay for the detection, identification and reporting of cells with micronuclei together with the determination of the cytokinesis-block proliferation index (CBPI) to quantify the treatment-related cytotoxicity. In the CA assay, the same platform was used to identify, map and retrieve metaphases for a subsequent CA evaluation by a trained evaluator. In both the assays, TPM and GVP provoked a significant genotoxic effect: up to 6-fold more micronucleated target cells than in the negative control and up to 10-fold increases in aberrant metaphases. Data variability was lower in the automated version of the MN assay than in the non-automated. It can be estimated that two test substances that differ in their genotoxicity by approximately 30% can statistically be distinguished in the automated MN and CA assays. Time savings, based on man hours, due to the automation were approximately 70% in the MN and 25% in the CA assays. The turn-around time of the evaluation phase could be shortened by 35 and 50%, respectively. Although only cigarette smoke-derived test material has been applied, the technical improvements should be of value for other test substances. PMID:25986082

  4. Vapor phase pyrolysis

    NASA Technical Reports Server (NTRS)

    Steurer, Wolfgang

    1992-01-01

    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 dissociates into suboxides and free oxygen. Rapid cooling of the dissociated vapor to a discrete temperature causes condensation of the suboxides, while the oxygen remains essentially intact and can be collected downstream. The gas flow path and flow rate are maintained at an optimum level by control of the pressure differential between the vaporization region and the oxygen collection system with the aid of the environmental vacuum.

  5. Evaluation of E-Cigarette Liquid Vapor and Mainstream Cigarette Smoke after Direct Exposure of Primary Human Bronchial Epithelial Cells

    PubMed Central

    Scheffler, Stefanie; Dieken, Hauke; Krischenowski, Olaf; Frster, Christine; Branscheid, Detlev; Aufderheide, Michaela

    2015-01-01

    E-cigarettes are emerging products, often described as reduced-risk nicotine products or alternatives to combustible cigarettes. Many smokers switch to e-cigarettes to quit or significantly reduce smoking. However, no regulations for e-cigarettes are currently into force, so that the quality and safety of e-liquids is not necessarily guaranteed. We exposed primary human bronchial epithelial cells of two different donors to vapor of e-cigarette liquid with or without nicotine, vapor of the carrier substances propylene glycol and glycerol as well as to mainstream smoke of K3R4F research cigarettes. The exposure was done in a CULTEX RFS compact module, allowing the exposure of the cells at the air-liquid interface. 24 h post-exposure, cell viability and oxidative stress levels in the cells were analyzed. We found toxicological effects of e-cigarette vapor and the pure carrier substances, whereas the nicotine concentration did not have an effect on the cell viability. The viability of mainstream smoke cigarette exposed cells was 4.58 times lower and the oxidative stress levels 4.55 times higher than those of e-cigarette vapor exposed cells, depending on the donor. Our experimental setup delivered reproducible data and thus provides the opportunity for routine testing of e-cigarette liquids to ensure safety and quality for the user. PMID:25856554

  6. Evaluation of E-cigarette liquid vapor and mainstream cigarette smoke after direct exposure of primary human bronchial epithelial cells.

    PubMed

    Scheffler, Stefanie; Dieken, Hauke; Krischenowski, Olaf; Frster, Christine; Branscheid, Detlev; Aufderheide, Michaela

    2015-04-01

    E-cigarettes are emerging products, often described as "reduced-risk" nicotine products or alternatives to combustible cigarettes. Many smokers switch to e-cigarettes to quit or significantly reduce smoking. However, no regulations for e-cigarettes are currently into force, so that the quality and safety of e-liquids is not necessarily guaranteed. We exposed primary human bronchial epithelial cells of two different donors to vapor of e-cigarette liquid with or without nicotine, vapor of the carrier substances propylene glycol and glycerol as well as to mainstream smoke of K3R4F research cigarettes. The exposure was done in a CULTEX RFS compact module, allowing the exposure of the cells at the air-liquid interface. 24 h post-exposure, cell viability and oxidative stress levels in the cells were analyzed. We found toxicological effects of e-cigarette vapor and the pure carrier substances, whereas the nicotine concentration did not have an effect on the cell viability. The viability of mainstream smoke cigarette exposed cells was 4.5-8 times lower and the oxidative stress levels 4.5-5 times higher than those of e-cigarette vapor exposed cells, depending on the donor. Our experimental setup delivered reproducible data and thus provides the opportunity for routine testing of e-cigarette liquids to ensure safety and quality for the user. PMID:25856554

  7. Chemical hazards present in liquids and vapors of electronic cigarettes.

    PubMed

    Hutzler, Christoph; Paschke, Meike; Kruschinski, Svetlana; Henkler, Frank; Hahn, Jürgen; Luch, Andreas

    2014-07-01

    Electronic (e-)cigarettes have emerged in recent years as putative alternative to conventional tobacco cigarettes. These products do not contain typical carcinogens that are present in tobacco smoke, due to the lack of combustion. However, besides nicotine, hazards can also arise from other constituents of liquids, such as solvents, flavors, additives and contaminants. In this study, we have analyzed 28 liquids of seven manufacturers purchased in Germany. We confirm the presence of a wide range of flavors to enhance palatability. Although glycerol and propylene glycol were detected in all samples, these solvents had been replaced by ethylene glycol as dominant compound in five products. Ethylene glycol is associated with markedly enhanced toxicological hazards when compared to conventionally used glycerol and propylene glycol. Additional additives, such as coumarin and acetamide, that raise concerns for human health were detected in certain samples. Ten out of 28 products had been declared "free-of-nicotine" by the manufacturer. Among these ten, seven liquids were identified containing nicotine in the range of 0.1-15 µg/ml. This suggests that "carry over" of ingredients may occur during the production of cartridges. We have further analyzed the formation of carbonylic compounds in one widely distributed nicotine-free brand. Significant amounts of formaldehyde, acetaldehyde and propionaldehyde were only found at 150 °C by headspace GC-MS analysis. In addition, an enhanced formation of aldehydes was found in defined puff fractions, using an adopted machine smoking protocol. However, this effect was delayed and only observed during the last third of the smoking procedure. In the emissions of these fractions, which represent up to 40 % of total vapor volume, similar levels of formaldehyde were detected when compared to conventional tobacco cigarettes. By contrast, carbonylic compounds were hardly detectable in earlier collected fractions. Our data demonstrate the necessity of standardized machine smoking protocols to reliably address putative risks of e-cigarettes for consumers. PMID:24958024

  8. Vapor Phase Catalytic Ammonia Reduction

    NASA Technical Reports Server (NTRS)

    Flynn, Michael T.; Harper, Lynn D. (Technical Monitor)

    1994-01-01

    This paper discusses the development of a Vapor Phase Catalytic Ammonia Reduction (VPCAR) teststand and the results of an experimental program designed to evaluate the potential of the technology as a water purification process. In the experimental program the technology is evaluated based upon product water purity, water recovery rate, and power consumption. The experimental work demonstrates that the technology produces high purity product water and attains high water recovery rates at a relatively high specific power consumption. The experimental program was conducted in 3 phases. In phase I an Igepon(TM) soap and water mixture was used to evaluate the performance of an innovative Wiped-Film Rotating-Disk evaporator and associated demister. In phase II a phenol-water solution was used to evaluate the performance of the high temperature catalytic oxidation reactor. In phase III a urine analog was used to evaluate the performance of the combined distillation/oxidation functions of the processor.

  9. Infrared spectroscopy study of the influence of inhaled vapors/smoke produced by cigarettes of active smokers

    NASA Astrophysics Data System (ADS)

    Popa, Cristina

    2015-05-01

    While much is known about the effect of smoke and vapors on the composition of blood, little is known about their impact on the composition of breath. When tobacco from traditional cigarettes (T) is burned, it produces harmful smoke compared with the vapor produced when using electronic cigarettes (E). Using a noninvasive, safe, and rapid CO2 laser-photoacoustic method, this study aimed to examine the ethylene changes at different time intervals in the exhaled breath composition of E-cigarette smokers and T-cigarette smokers, before and after the consecutive exposures to cigarettes. Oxidative stress from exposure to tobacco smoke has a role in the pathogenic process, leading to chronic obstructive pulmonary disease. The evidence on the mechanisms by which T-smoking causes damage indicates that there is no risk-free level of exposure to tobacco smoke. The study revealed that the ethylene level (in the E-cigarette smoker's case) was found to be in smaller concentrations (compared with T-cigarette smoker's case) and that E-cigarettes may provide an alternative to T-cigarette smoking.

  10. Infrared spectroscopy study of the influence of inhaled vapors/smoke produced by cigarettes of active smokers.

    PubMed

    Popa, Cristina

    2015-05-01

    While much is known about the effect of smoke and vapors on the composition of blood, little is known about their impact on the composition of breath. When tobacco from traditional cigarettes (T) is burned, it produces harmful smoke compared with the vapor produced when using electronic cigarettes (E). Using a noninvasive, safe, and rapid CO2 laser-photoacoustic method, this study aimed to examine the ethylene changes at different time intervals in the exhaled breath composition of E-cigarette smokers and T-cigarette smokers, before and after the consecutive exposures to cigarettes. Oxidative stress from exposure to tobacco smoke has a role in the pathogenic process, leading to chronic obstructive pulmonary disease. The evidence on the mechanisms by which T-smoking causes damage indicates that there is no risk-free level of exposure to tobacco smoke. The study revealed that the ethylene level (in the E-cigarette smoker's case) was found to be in smaller concentrations (compared with T-cigarette smoker's case) and that E-cigarettes may provide an alternative to T-cigarette smoking. PMID:25347574

  11. Endothelial disruptive proinflammatory effects of nicotine and e-cigarette vapor exposures.

    PubMed

    Schweitzer, Kelly S; Chen, Steven X; Law, Sarah; Van Demark, Mary; Poirier, Christophe; Justice, Matthew J; Hubbard, Walter C; Kim, Elena S; Lai, Xianyin; Wang, Mu; Kranz, William D; Carroll, Clinton J; Ray, Bruce D; Bittman, Robert; Goodpaster, John; Petrache, Irina

    2015-07-15

    The increased use of inhaled nicotine via e-cigarettes has unknown risks to lung health. Having previously shown that cigarette smoke (CS) extract disrupts the lung microvasculature barrier function by endothelial cell activation and cytoskeletal rearrangement, we investigated the contribution of nicotine in CS or e-cigarettes (e-Cig) to lung endothelial injury. Primary lung microvascular endothelial cells were exposed to nicotine, e-Cig solution, or condensed e-Cig vapor (1-20 mM nicotine) or to nicotine-free CS extract or e-Cig solutions. Compared with nicotine-containing extract, nicotine free-CS extract (10-20%) caused significantly less endothelial permeability as measured with electric cell-substrate impedance sensing. Nicotine exposures triggered dose-dependent loss of endothelial barrier in cultured cell monolayers and rapidly increased lung inflammation and oxidative stress in mice. The endothelial barrier disruptive effects were associated with increased intracellular ceramides, p38 MAPK activation, and myosin light chain (MLC) phosphorylation, and was critically mediated by Rho-activated kinase via inhibition of MLC-phosphatase unit MYPT1. Although nicotine at sufficient concentrations to cause endothelial barrier loss did not trigger cell necrosis, it markedly inhibited cell proliferation. Augmentation of sphingosine-1-phosphate (S1P) signaling via S1P1 improved both endothelial cell proliferation and barrier function during nicotine exposures. Nicotine-independent effects of e-Cig solutions were noted, which may be attributable to acrolein, detected along with propylene glycol, glycerol, and nicotine by NMR, mass spectrometry, and gas chromatography, in both e-Cig solutions and vapor. These results suggest that soluble components of e-Cig, including nicotine, cause dose-dependent loss of lung endothelial barrier function, which is associated with oxidative stress and brisk inflammation. PMID:25979079

  12. Water vapor radiometry research and development phase

    NASA Technical Reports Server (NTRS)

    Resch, G. M.; Chavez, M. C.; Yamane, N. L.; Barbier, K. M.; Chandlee, R. C.

    1985-01-01

    This report describes the research and development phase for eight dual-channel water vapor radiometers constructed for the Crustal Dynamics Project at the Goddard Space Flight Center, Greenbelt, Maryland, and for the NASA Deep Space Network. These instruments were developed to demonstrate that the variable path delay imposed on microwave radio transmissions by atmospheric water vapor can be calibrated, particularly as this phenomenon affects very long baseline interferometry measurement systems. Water vapor radiometry technology can also be used in systems that involve moist air meteorology and propagation studies.

  13. An overview: Vapor phase corrosion inhibitors

    SciTech Connect

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

    2000-02-01

    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 techniques. Methods of application of the vapor phase inhibitors and their industrial uses also were presented.

  14. Progress in vapor phase lubrication technology

    SciTech Connect

    Placek, D.G. ); Freiheit, T. )

    1993-10-01

    Improving the efficiency of engine performance will require the design of systems with higher operating temperatures and pressures. These conditions will stress traditional lubricants beyond their current performance capabilities, and require the development of improved methods for friction and wear reduction. The most revolutionary approach to high-temperature lubrication is the concept of vapor phase delivery. An ashless organic compound can be vaporized by the heat of the operating engine or a carrier gas, and introduced into the ring zone of the cylinder. The vapor condenses or chemically binds with the piston ring or cylinder wall, and provides boundary lubrication. A minute amount of lubricant is constantly introduced in order to maintain a lubricating film. Each stroke of the piston shears off a portion of the lubricant layer, but condensing vapor continually replaces the surface film. Lubricant contributions to exhaust emissions are expected to be lower than those currently resulting from liquid lubricants. Vapor phase lubrication is an emerging concept that may be the key to the development of a commercial low heat rejection engine with improved energy efficiency and reduced emissions. The Department of Energy continues to fund research at a variety of industrial and academic institutions. Basic concepts and recent developments in the field of vapor phase lubrication will be reviewed.

  15. Phase-field crystal model with a vapor phase.

    PubMed

    Schwalbach, Edwin J; Warren, James A; Wu, Kuo-An; Voorhees, Peter W

    2013-08-01

    Phase-field crystal (PFC) models are able to resolve atomic length scale features of materials during temporal evolution over diffusive time scales. Traditional PFC models contain solid and liquid phases, however many important materials processing phenomena involve a vapor phase as well. In this work, we add a vapor phase to an existing PFC model and show realistic interfacial phenomena near the triple point temperature. For example, the PFC model exhibits density oscillations at liquid-vapor interfaces that compare favorably to data available for interfaces in metallic systems from both experiment and molecular-dynamics simulations. We also quantify the anisotropic solid-vapor surface energy for a two-dimensional PFC hexagonal crystal and find well-defined step energies from measurements on the faceted interfaces. Additionally, the strain field beneath a stepped interface is characterized and shown to qualitatively reproduce predictions from continuum models, simulations, and experimental data. Finally, we examine the dynamic case of step-flow growth of a crystal into a supersaturated vapor phase. The ability to model such a wide range of surface and bulk defects makes this PFC model a useful tool to study processing techniques such as chemical vapor deposition or vapor-liquid-solid growth of nanowires. PMID:24032965

  16. Adult Behavior in Male Mice Exposed to E-Cigarette Nicotine Vapors during Late Prenatal and Early Postnatal Life

    PubMed Central

    Smith, Dani; Aherrera, Angela; Lopez, Armando; Neptune, Enid; Winickoff, Jonathan P.; Klein, Jonathan D.; Chen, Gang; Lazarus, Philip; Collaco, Joseph M.; McGrath-Morrow, Sharon A.

    2015-01-01

    Nicotine exposure has been associated with an increased likelihood of developing attention deficit hyperactivity disorder (ADHD) in offspring of mothers who smoked during pregnancy. The goal of this study was to determine if exposure to E-cigarette nicotine vapors during late prenatal and early postnatal life altered behavior in adult mice. Methods Timed-pregnant C57BL/6J mice were exposed to 2.4% nicotine in propylene glycol (PG) or 0% nicotine /PG once a day from gestational day 15 until delivery. After delivery, offspring and mothers were exposed to E-cigarette vapors for an additional 14 days from postnatal day 2 through 16. Following their last exposure serum cotinine levels were measured in female juvenile mice. Male mice underwent behavioral testing at 14 weeks of age to assess sensorimotor, affective, and cognitive functional domains. Results Adult male mice exposed to 2.4% nicotine/PG E-cigarette vapors had significantly more head dips in the zero maze test and higher levels of rearing activity in the open field test compared to 0% nicotine/PG exposed mice and untreated controls. In the water maze test after reversal training, the 2.4% nicotine/PG mice spent more than 25% of time in the new location whereas the other groups did not. Conclusion Adult male mice exhibited increased levels of activity in the zero maze and open field tests when exposed to E-cigarette vapor containing nicotine during late prenatal and early postnatal life. These findings indicate that nicotine exposure from E-cigarettes may cause persistent behavioral changes when exposure occurs during a period of rapid brain growth. PMID:26372012

  17. Vapor-liquid phase separator permeability results

    NASA Technical Reports Server (NTRS)

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

    1981-01-01

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

  18. Vapor-liquid phase separator studies

    NASA Technical Reports Server (NTRS)

    Yuan, S. W. K.; Lee, J. M.; Kim, Y. I.; Hepler, W. A.; Frederking, T. H. K.

    1983-01-01

    Porous plugs serve as both entropy rejection devices and phase separation components separating the vapor phase on the downstream side from liquid Helium 2 upstream. The liquid upstream is the cryo-reservoir fluid needed for equipment cooling by means of Helium 2, i.e Helium-4 below its lambda temperature in near-saturated states. The topics outlined are characteristic lengths, transport equations and plug results.

  19. Liquid-phase compositions from vapor-phase analyses

    SciTech Connect

    Davis, W. Jr. ); Cochran, H.D. )

    1990-02-01

    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.

  20. A protocol for detecting and scavenging gas-phase free radicals in mainstream cigarette smoke.

    PubMed

    Yu, Long-Xi; Dzikovski, Boris G; Freed, Jack H

    2012-01-01

    Cigarette smoking is associated with human cancers. It has been reported that most of the lung cancer deaths are caused by cigarette smoking (5,6,7,12). Although tobacco tars and related products in the particle phase of cigarette smoke are major causes of carcinogenic and mutagenic related diseases, cigarette smoke contains significant amounts of free radicals that are also considered as an important group of carcinogens(9,10). Free radicals attack cell constituents by damaging protein structure, lipids and DNA sequences and increase the risks of developing various types of cancers. Inhaled radicals produce adducts that contribute to many of the negative health effects of tobacco smoke in the lung(3). Studies have been conducted to reduce free radicals in cigarette smoke to decrease risks of the smoking-induced damage. It has been reported that haemoglobin and heme-containing compounds could partially scavenge nitric oxide, reactive oxidants and carcinogenic volatile nitrosocompounds of cigarette smoke(4). A 'bio-filter' consisted of haemoglobin and activated carbon was used to scavenge the free radicals and to remove up to 90% of the free radicals from cigarette smoke(14). However, due to the cost-ineffectiveness, it has not been successfully commercialized. Another study showed good scavenging efficiency of shikonin, a component of Chinese herbal medicine(8). In the present study, we report a protocol for introducing common natural antioxidant extracts into the cigarette filter for scavenging gas phase free radicals in cigarette smoke and measurement of the scavenge effect on gas phase free radicals in mainstream cigarette smoke (MCS) using spin-trapping Electron Spin Resonance (ESR) Spectroscopy(1,2,14). We showed high scavenging capacity of lycopene and grape seed extract which could point to their future application in cigarette filters. An important advantage of these prospective scavengers is that they can be obtained in large quantities from byproducts of tomato or wine industry respectively(11,13). PMID:22230844

  1. Vapor-liquid phase separator studies

    NASA Technical Reports Server (NTRS)

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

    1985-01-01

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

  2. A Simple and Rapid Method for Standard Preparation of Gas Phase Extract of Cigarette Smoke

    PubMed Central

    Higashi, Tsunehito; Mai, Yosuke; Noya, Yoichi; Horinouchi, Takahiro; Terada, Koji; Hoshi, Akimasa; Nepal, Prabha; Harada, Takuya; Horiguchi, Mika; Hatate, Chizuru; Kuge, Yuji; Miwa, Soichi

    2014-01-01

    Cigarette smoke consists of tar and gas phase: the latter is toxicologically important because it can pass through lung alveolar epithelium to enter the circulation. Here we attempt to establish a standard method for preparation of gas phase extract of cigarette smoke (CSE). CSE was prepared by continuously sucking cigarette smoke through a Cambridge filter to remove tar, followed by bubbling it into phosphate-buffered saline (PBS). An increase in dry weight of the filter was defined as tar weight. Characteristically, concentrations of CSEs were represented as virtual tar concentrations, assuming that tar on the filter was dissolved in PBS. CSEs prepared from smaller numbers of cigarettes (original tar concentrations ?15 mg/ml) showed similar concentration-response curves for cytotoxicity versus virtual tar concentrations, but with CSEs from larger numbers (tar ?20 mg/ml), the curves were shifted rightward. Accordingly, the cytotoxic activity was detected in PBS of the second reservoir downstream of the first one with larger numbers of cigarettes. CSEs prepared from various cigarette brands showed comparable concentration-response curves for cytotoxicity. Two types of CSEs prepared by continuous and puff smoking protocols were similar regarding concentration-response curves for cytotoxicity, pharmacology of their cytotoxicity, and concentrations of cytotoxic compounds. These data show that concentrations of CSEs expressed by virtual tar concentrations can be a reference value to normalize their cytotoxicity, irrespective of numbers of combusted cigarettes, cigarette brands and smoking protocols, if original tar concentrations are ?15 mg/ml. PMID:25229830

  3. 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...

  4. Mechanistic study of organometallic vapor phase epitaxy

    SciTech Connect

    Stringfellow, G.B.

    1990-01-01

    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.

  5. Mechanistic study of organometallic vapor phase epitaxy

    SciTech Connect

    Stringfellow, G.B.

    1990-12-31

    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.

  6. Monitoring of vapor phase polycyclic aromatic hydrocarbons

    DOEpatents

    Vo-Dinh, Tuan; Hajaligol, Mohammad R.

    2004-06-01

    An apparatus for monitoring vapor phase polycyclic aromatic hydrocarbons in a high-temperature environment has an excitation source producing electromagnetic radiation, an optical path having an optical probe optically communicating the electromagnetic radiation received at a proximal end to a distal end, a spectrometer or polychromator, a detector, and a positioner coupled to the first optical path. The positioner can slidably move the distal end of the optical probe to maintain the distal end position with respect to an area of a material undergoing combustion. The emitted wavelength can be directed to a detector in a single optical probe 180.degree. backscattered configuration, in a dual optical probe 180.degree. backscattered configuration or in a dual optical probe 90.degree. side scattered configuration. The apparatus can be used to monitor an emitted wavelength of energy from a polycyclic aromatic hydrocarbon as it fluoresces in a high temperature environment.

  7. Dynamics of viscous coalescing droplets in a saturated vapor phase

    NASA Astrophysics Data System (ADS)

    Baroudi, Lina; Nagel, Sidney R.; Morris, Jeffrey F.; Lee, Taehun

    2015-12-01

    The dynamics of two liquid droplets coalescing in their saturated vapor phase are investigated by Lattice Boltzmann numerical simulations. Attention is paid to the effect of the vapor phase on the formation and growth dynamics of the liquid bridge in the viscous regime. We observe that the onset of the coalescence occurs earlier and the expansion of the bridge initially proceeds faster when the coalescence takes place in a saturated vapor compared to the coalescence in a non-condensable gas. We argue that the initially faster evolution of the coalescence in the saturated vapor is caused by the vapor transport through condensation during the early stages of the coalescence.

  8. Chiroptical Spectroscopy in the Vapor Phase

    NASA Astrophysics Data System (ADS)

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

    2011-06-01

    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. Mller, 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).

  9. DIFFERENTIAL IN VIVO EFFECTS OF WHOLE CIGARETTE SMOKE EXPOSURE VERSUS CIGARETTE SMOKE EXTRACT ON MOUSE CILIATED TRACHEAL EPITHELIUM

    Technology Transfer Automated Retrieval System (TEKTRAN)

    In this study we compared the affect of vapor phase cigarette smoke (CS) versus cigarette smoke extract (CSE) on the lungs and upper airway of C57BL/6 mice. We found that CSE treatment significantly increased neutrophil influx (P<0.001), baseline ciliary beat frequency (CBF) (P<0.05), and protein ki...

  10. Vapor-phase viscosity of phenol

    NASA Astrophysics Data System (ADS)

    Vogel, E.; Neumann, A.-K.

    1993-07-01

    New measurements of the vapor-phase viscosity of phenol were performed from 437 up to 624 K and for densities between 0.006 and 0.023 mol L-1 in an all-quartz oscillating-disk viscometer with small gaps. Thus, including our own measurements reported earlier, experimental data are available in the temperature range between 376 and 639 K and in the density range from 0.001 up to 0.023 mol L-1. The data were evaluated with a density series for the viscosity in which only a linear density contribution is included. The values of the second viscosity virial coefficient obtained for phenol as well as for benzene, toluene, and p-xylene were compared with results of the Rainwater-Friend theory and of the modified Enskog theory on the basis of the Lennard-Jones 12-6 potential. The agreement is reasonable, when the potential parameter ratios determined by Bich and Vogel are used. The influence of bound dimers seems to be already taken into account in the three-monomer contribution according to Hoffman and Curtiss.

  11. Vapor phase epitaxy of monocrystal tungsten coatings

    NASA Astrophysics Data System (ADS)

    Lv, Yanwei; Yu, Xiaodong; Wang, Fuchi; Tan, Chengwen; Yang, Qifa; Zheng, Jianping; Wang, Zhendong; Cai, Hongnian

    2014-02-01

    Monocrystal tungsten coatings were obtained by vapor phase epitaxy in a W-WClx-Cl system using Mo single-crystal substrate. The kinetics of the deposition process was studied in a wider temperature and pressure range. As the total pressure was 15.77 Pa, the surface kinetics controlled by the deposition process as the temperature was in the range of 1383-1503 K. When the deposition temperature was increased up to 1573 K, the control mechanism was mass transport limited. When the deposition temperature was maintained at 1673 K and the total pressure was 15.77-25.23 Pa, the deposition process was mass transport limited. When the total pressure was increased to 42.32 Pa, the control mechanism of the deposition process became surface kinetics limited. By basic treatment, namely, 'supply transport medium as required', a kinetics model predicting the tungsten coating growth rate was achieved. In the case of lower pressure for the surface kinetics-limited regime, the deposition rate was proportional to pressure. When the pressure was high, the deposition rate was proportional to the half power of pressure. As the pressure increased further, the deposition rate and pressure became kinetically irrelevant. The model predictions were in good agreement with the experimental growth rates, as further proven by the surface morphology analysis of the monocrystal tungsten coatings.

  12. The liquid to vapor phase transition in excited nuclei

    SciTech Connect

    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

    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.

  13. External fuel vaporization study, phase 1

    NASA Technical Reports Server (NTRS)

    Szetela, E. J.; Chiappetta, L.

    1980-01-01

    A conceptual design study was conducted to devise and evaluate techniques for the external vaporization of fuel for use in an aircraft gas turbine with characteristics similar to the Energy Efficient Engine (E(3)). Three vaporizer concepts were selected and they were analyzed from the standpoint of fuel thermal stability, integration of the vaporizer system into the aircraft engine, engine and vaporizer dynamic response, startup and altitude restart, engine performance, control requirements, safety, and maintenance. One of the concepts was found to improve the performance of the baseline E(3) engine without seriously compromising engine startup and power change response. Increased maintenance is required because of the need for frequent pyrolytic cleaning of the surfaces in contact with hot fuel.

  14. Nanoscale molecular device fabrication via solution and vapor phase deposition

    NASA Astrophysics Data System (ADS)

    Gergel-Hackett, Nadine

    This work describes the fabrication of molecular electronic devices using solution phase and vapor phase assembly methods. The project was motivated by the existing limits of molecular electronics including: a lack of reproducible nanoscale molecular test devices, limited device fabrication techniques that resulted in low yields, and molecular devices that lacked potential for integration with traditional CMOS components. To address these issues, I first designed and fabricated a nanoscale molecular test device using traditional solution phase assembly methods. This test device was shown to be effective and reproducible by characterizing molecules with well-established electrical behaviors. I then used this test device to investigate the electrical behavior of an oligo(phenylene ethynylene) molecule with a nitro sidegroup, known as the nitro molecule. This molecule exhibited interesting electrical behavior with the potential for use in memory and logic devices. In order to better understand the behavioral variations observed from the nitro molecule, I investigated the effect that different molecular environments had on its electrical behavior. Next, molecular device fabrication procedures were improved by developing a method of vapor phase assembly. For this vapor phase deposition, I modified an existing ultra-high vacuum molecular beam epitaxy chamber and developed procedures for purifying the organic molecules prior to assembly. Vapor phase deposition was used to assemble single monolayers of various conducting molecules on gold substrates and the monolayers were characterized to confirm that they were chemisorbed, dense, uncontaminated, and ordered. Nanowell test devices that were fabricated via vapor phase deposition showed the expected electrical characteristics - verifying the effectiveness of vapor phase assembly for molecular electronic device fabrication. I also used vapor phase deposition to assemble conducting molecules on silicon substrates. This switch from gold to silicon substrates helped to increase the potential for molecular devices to be integrated with traditional CMOS devices for hybrid circuits. Overall, vapor phase deposition was established as an effective reproducible molecular assembly method for fabricating molecular electronic devices with the potential for integration with traditional CMOS technology.

  15. BIOREMEDIATION OF MIXED VAPOR PHASE CONTAMINANTS FROM SOILS AND GROUNDWATER

    EPA Science Inventory

    Soil vapor phase contaminants commonly include combinations of chlorinated ethenes and petroleum hydrocarbons. Many chlorinated ethenes and petroleum hydrocarbons are readily degradable by a range of aerobic soil microorganisms, making the use of biological systems for degrading ...

  16. 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...

  17. Development of Vapor-Phase Catalytic Ammonia Removal System

    NASA Technical Reports Server (NTRS)

    Flynn, Michael; Fisher, John; Kiss, Mark; Borchers, Bruce; Tleimat, Badawi; Tleimat, Maher; Quinn, Gregory; Fort, James; Nalette, Tim; Baker, Gale; Genovese, Joseph

    2007-01-01

    A report describes recent accomplishments of a continuing effort to develop the vapor-phase catalytic ammonia removal (VPCAR) process for recycling wastewater for consumption by humans aboard a spacecraft in transit to Mars.

  18. Vapor core turbulence in annular two-phase flow

    SciTech Connect

    Trabold, T.A.; Kumar, R.

    1998-06-01

    This paper reports a new technique to measure vapor turbulence in two-phase flows using hot-film anemometry. Continuous vapor turbulence measurements along with local void fraction, droplet frequency, droplet velocity and droplet diameter were measured in a thin, vertical duct. By first eliminating the portion of the output voltage signal resulting from the interaction of dispersed liquid droplets with the HFA sensor, the discrete voltage samples associated with the vapor phase were separately analyzed. The data revealed that, over the range of liquid droplet sizes and concentrations encountered, the presence of the droplet field acts to enhance vapor turbulence. In addition, there is evidence that vapor turbulence is significantly influenced by the wall-bounded liquid film. The present results are qualitatively consistent with the limited data available in the open literature.

  19. Simultaneous Analysis of 22 Volatile Organic Compounds in Cigarette Smoke Using Gas Sampling Bags for High-Throughput Solid-Phase Microextraction

    PubMed Central

    Sampson, Maureen M.; Chambers, David M.; Pazo, Daniel Y.; Moliere, Fallon; Blount, Benjamin C.; Watson, Clifford H.

    2015-01-01

    Quantifying volatile organic compounds (VOCs) in cigarette smoke is necessary to establish smoke-related exposure estimates and evaluate emerging products and potential reduced-exposure products. In response to this need, we developed an automated, multi-VOC quantification method for machine-generated, mainstream cigarette smoke using solidphase microextraction gas chromatographymass spectrometry (SPME-GCMS). This method was developed to simultaneously quantify a broad range of smoke VOCs (i.e., carbonyls and volatiles, which historically have been measured by separate assays) for large exposure assessment studies. Our approach collects and maintains vapor-phase smoke in a gas sampling bag, where it is homogenized with isotopically labeled analogue internal standards and sampled using gas-phase SPME. High throughput is achieved by SPME automation using a CTC Analytics platform and custom bag tray. This method has successfully quantified 22 structurally diverse VOCs (e.g., benzene and associated monoaromatics, aldehydes and ketones, furans, acrylonitrile, 1,3-butadiene, vinyl chloride, and nitromethane) in the microgram range in mainstream smoke from 1R5F and 3R4F research cigarettes smoked under ISO (Cambridge Filter or FTC) and Intense (Health Canada or Canadian Intense) conditions. Our results are comparable to previous studies with few exceptions. Method accuracy was evaluated with third-party reference samples (?15% error). Short-term diffusion losses from the gas sampling bag were minimal, with a 10% decrease in absolute response after 24 h. For most analytes, research cigarette inter- and intrarun precisions were ?20% relative standard deviation (RSD). This method provides an accurate and robust means to quantify VOCs in cigarette smoke spanning a range of yields that is sufficient to characterize smoke exposure estimates. PMID:24933649

  20. Preliminary assessment of halogenated alkanes as vapor-phase tracers

    SciTech Connect

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

    1991-01-01

    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.

  1. External fuel vaporization study, phase 2

    NASA Technical Reports Server (NTRS)

    Szetela, E. J.; Chiappetta, L.

    1981-01-01

    An analytical study was conducted to evaluate the effect of variations in fuel properties on the design of an external fuel vaporizaton system. The fuel properties that were considered included thermal stability, critical temperature, enthalpy a critical conditions, volatility, and viscosity. The design parameters that were evaluated included vaporizer weight and the impact on engine requirement such as maintenance, transient response, performance, and altitude relight. The baseline fuel properties were those of Jet A. The variation in thermal stability was taken as the thermal stability variation for Experimental Referee Broad Specification (ERBS) fuel. The results of the analysis indicate that a change in thermal stability equivalent to that of ERBS would increase the vaporization system weight by 20 percent, decrease oprating time between cleaning by 40 percent and make altitude relight more difficult. An increase in fuel critical temperature of 39 K would require a 40 percent increase in vaporization system weight. The assumed increase in enthalpy and volatility would also increase vaporizer weight by 40 percent and make altitude relight extremely difficult. The variation in fuel viscosity would have a negligible effect on the design parameters.

  2. The interaction of the theophylline metastable phase with water vapor

    NASA Astrophysics Data System (ADS)

    Matvienko, A. A.; Boldyrev, V. V.; Sidel'Nikov, A. A.; Chizhik, S. A.

    2008-07-01

    The conditions of hydration of the stable and metastable theophylline phases were determined. Two-phase metastable phase/monohydrate and stable phase/monohydrate equilibrium pressures were measured at 25, 30, and 35C. The metastable phase began to react with water vapor at lower relative humidities than the stable phase. Processes that occurred with the metastable and stable theophylline phases over various water pressure ranges were considered. The metastable phase exhibited an unusual behavior at 25C and relative humidity 47%. At constant water vapor pressure and temperature, theophylline was initially hydrated and then lost water and again became anhydrous. Two consecutive processes occurred in the system, the formation of theophylline monohydrate from the metastable phase and its decomposition to the stable phase. The ratio between the rates of these processes determined the content of the monohydrate at the given time moment.

  3. Cigarettes and cigarette smoking.

    PubMed

    Burns, D M

    1991-12-01

    Tobacco use was widespread in the New World by the time of the first voyage of Columbus; however, it is only in the last century that the use of tobacco as cigarettes has been prevalent. The milder tobacco and more acidic smoke of cigarettes lead to the deeper inhalation of tobacco into the lung with resultant deposition and absorption of the addicting, toxic, and carcinogenic components of the smoke. More than 4000 individual constituents have been identified in cigarette smoke, and the relative concentrations of these constituents vary widely between brands of cigarettes. Tar yield, a measure of the total particulate matter of the smoke, varies markedly with the characteristics of the cigarette manufacture and with the pattern of inhalation. As a result, tar is not a good measure of the dose of toxic or carcinogenic agents received by the individual smoker. The particle size of cigarette smoke is in the range that will lead to deposition in the airways and alveoli of the lung, and many of the gas-phase constituents are absorbed across the alveolar capillary membrane. The irritant agents in the smoke cause acute and chronic changes in lung structure and function that may result in greater retention of carcinogens within the lung and increased vulnerability of the lung to the effects of these carcinogens. Carcinogens and other constituents of cigarette smoke are also absorbed into the blood and metabolized to active forms through microsomal enzyme systems induced by cigarette smoke. The cellular influx of neutrophils and alveolar macrophages that is part of the inflammatory response may be the precursor of the alveolar wall destruction that results in emphysema. The prevalence of smoking is not uniformly distributed across the population. Men began smoking in large numbers very early in the century, but women began to smoke in large number only at the time of the Second World War. Men born after 1930 have been less likely to take up smoking than their older counterparts. The prevalence of smoking is currently declining in both men and women. PMID:1747982

  4. Vapor Phase Deposition Using Plasma Spray-PVD

    NASA Astrophysics Data System (ADS)

    von Niessen, K.; Gindrat, M.; Refke, A.

    2010-01-01

    Plasma sprayphysical vapor deposition (PS-PVD) is a low pressure plasma spray technology to deposit coatings out of the vapor phase. PS-PVD is a part of the family of new hybrid processes recently developed by Sulzer Metco AG (Switzerland) on the basis of the well-established low pressure plasma spraying (LPPS) technology. Included in this new process family are plasma spraychemical vapor deposition (PS-CVD) and plasma spraythin film (PS-TF) processes. In comparison to conventional vacuum plasma spraying and LPPS, these new processes use a high energy plasma gun operated at a work pressure below 2 mbar. This leads to unconventional plasma jet characteristics which can be used to obtain specific and unique coatings. An important new feature of PS-PVD is the possibility to deposit a coating not only by melting the feed stock material which builds up a layer from liquid splats, but also by vaporizing the injected material. Therefore, the PS-PVD process fills the gap between the conventional PVD technologies and standard thermal spray processes. The possibility to vaporize feedstock material and to produce layers out of the vapor phase results in new and unique coating microstructures. The properties of such coatings are superior to those of thermal spray and EB-PVD coatings. This paper reports on the progress made at Sulzer Metco to develop functional coatings build up from vapor phase of oxide ceramics and metals.

  5. Third-harmonic generation in phase-matched Rb vapor.

    NASA Technical Reports Server (NTRS)

    Young, J. F.; Bjorklund, G. C.; Kung, A. H.; Miles, R. B.; Harris, S. E.

    1971-01-01

    The generation of 0.3547-micron radiation was performed by tripling 1.064-micron radiation in a phase-matched mixture of rubidium vapor and xenon. A third-harmonic nonlinear susceptibility in Rb vapor is confirmed. It is about 100,000 times greater than that of He. This large susceptibility is due to the large oscillator strengths and resonant enhancements resulting from Rb transitions in the near infrared, visible, and UV.

  6. Vapor-phase carbonylation of dimethoxymethane over H-Faujasite.

    PubMed

    Celik, Fuat E; Kim, Tae-Jin; Bell, Alexis T

    2009-01-01

    Carbonylation gets a phase lift: The usual liquid-phase, high-pressure processes for carbonylating formaldehydes are avoided in a novel vapor-phase reaction. Using an acid zeolite (Faujasite) at near-atmospheric pressure dimethoxymethane (DMM; the dimethyl acetal of formaldehyde; see scheme) is carbonylated to produce methyl methoxyacetate (MMAc). This approach provides a new route to ethylene glycol under mild conditions. PMID:19452505

  7. Toxicological assessment of kretek cigarettes: Part 1: background, assessment approach, and summary of findings.

    PubMed

    Roemer, E; Dempsey, R; Schorp, M K

    2014-12-01

    This publication introduces a series of six other publications describing the toxicological assessment of kretek cigarettes, i.e., cigarettes characterized primarily by the use of a significant amount of cloves as an ingredient added to the tobacco. This paper presents background information on kretek cigarettes, describes the general approach of the in vitro and in vivo toxicological assessment of mainstream smoke from kretek cigarettes, presents the methodology used, and summarizes the results of the assessment program. In summary, the smoke from kretek cigarettes gives rise to the typical cigarette smoke-related effects known from American-blended cigarettes, does not reveal any novel toxicity, and exhibits an unexpected distinct attenuation of pulmonary inflammation. Based on equal amounts of smoke total particulate matter (TPM), kretek cigarettes deliver less toxicants when compared to American-blended cigarettes; when assessed in vitro, the smoke from kretek cigarettes is less cytotoxic (gas/vapor phase) and less mutagenic (TPM). When assessed in vivo, kretek cigarette smoke shows lower toxicity in the respiratory tract. When based on an equal nicotine basis, several of the toxicity endpoints in kretek cigarettes become equivalent to American-blended cigarettes. The data do not indicate an increased hazard potential of kreteks compared to American-blended cigarettes. PMID:25498000

  8. 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

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

    2010-10-01

    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

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

    SciTech Connect

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

    1996-08-01

    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.

  10. Phase transformations during the growth of paracetamol crystals from the vapor phase

    NASA Astrophysics Data System (ADS)

    Belyaev, A. P.; Rubets, V. P.; Antipov, V. V.; Bordei, N. S.

    2014-07-01

    Phase transformations during the growth of paracetamol crystals from the vapor phase are studied by differential scanning calorimetry. It is found that the vapor-crystal phase transition is actually a superposition of two phase transitions: a first-order phase transition with variable density and a second-order phase transition with variable ordering. The latter, being a diffuse phase transition, results in the formation of a new, "pretransition," phase irreversibly spent in the course of the transition, which ends in the appearance of orthorhombic crystals. X-ray diffraction data and micrograph are presented.

  11. Fog Machines, Vapors, and Phase Diagrams

    ERIC Educational Resources Information Center

    Vitz, Ed

    2008-01-01

    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

  12. Fog Machines, Vapors, and Phase Diagrams

    ERIC Educational Resources Information Center

    Vitz, Ed

    2008-01-01

    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…

  13. The mouse lymphoma thymidine kinase assay for the assessment and comparison of the mutagenic activity of cigarette mainstream smoke particulate phase.

    PubMed

    Schramke, H; Meisgen, T J; Tewes, F J; Gomm, W; Roemer, E

    2006-10-29

    The mouse lymphoma thymidine kinase assay (MLA) has been optimized to quantitatively determine the in vitro mutagenicity of cigarette mainstream smoke particulate phase. To test whether the MLA is able to discriminate between different cigarette types, specially constructed cigarettes each containing a single tobacco type - Bright, Burley, or Oriental - were investigated. The mutagenic activity of the Burley cigarette was statistically significantly lower, up to approximately 40%, than that of the Bright and Oriental cigarettes. To determine the impact of two different sets of smoking conditions, American-blend cigarettes were smoked under US Federal Trade Commission/International Organisation for Standardisation conditions and under Massachusetts Department of Public Health (MDPH) conditions. Conventional cigarettes - eight from the US commercial market plus the Reference Cigarettes 1R4F and 2R4F - and an electrically heated cigarette smoking system (EHCSS) prototype were tested. There were no statistically significant differences between the two sets of smoking conditions on a per mg total particulate matter basis, although there was a consistent trend towards slightly lower mutagenic activity under MDPH conditions. The mutagenic activity of the EHCSS prototype was distinctly lower than that of the conventional cigarettes under both sets of smoking conditions. These results show that the MLA can be used to assess and compare the mutagenic activity of cigarette mainstream smoke particulate phase in the comprehensive toxicological assessment of cigarette smoke. PMID:16963170

  14. Quantitative Infrared Spectra of Vapor Phase Chemical Agents

    SciTech Connect

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

    2003-04-21

    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).

  15. Assessment of radionuclide vapor-phase transport in unsaturated tuff

    SciTech Connect

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

    1986-11-01

    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.

  16. Electronic Cigarettes

    MedlinePLUS

    ... New FDA Regulations 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 ...

  17. Bacterial chemotaxis along vapor-phase gradients of naphthalene.

    PubMed

    Hanzel, Joanna; Harms, Hauke; Wick, Lukas Y

    2010-12-15

    The role of bacterial growth and translocation for the bioremediation of organic contaminants in the vadose zone is poorly understood. Whereas air-filled pores restrict the mobility of bacteria, diffusion of volatile organic compounds in air is more efficient than in water. Past research, however, has focused on chemotactic swimming of bacteria along gradients of water-dissolved chemicals. In this study we tested if and to what extent Pseudomonas putida PpG7 (NAH7) chemotactically reacts to vapor-phase gradients forming above their swimming medium by the volatilization from a spot source of solid naphthalene. The development of an aqueous naphthalene gradient by air-water partitioning was largely suppressed by means of activated carbon in the agar. Surprisingly, strain PpG7 was repelled by vapor-phase naphthalene although the steady state gaseous concentrations were 50-100 times lower than the aqueous concentrations that result in positive chemotaxis of the same strain. It is thus assumed that the efficient gas-phase diffusion resulting in a steady, and possibly toxic, naphthalene flux to the cells controlled the chemotactic reaction rather than the concentration to which the cells were exposed. To our knowledge this is the first demonstration of apparent chemotactic behavior of bacteria in response to vapor-phase effector gradients. PMID:21080701

  18. Numerical Modelling of the Expansion Phase of Vapor Explosions

    NASA Astrophysics Data System (ADS)

    Hwang, Moonkyu

    When a cold liquid is brought into contact with a molten material with a temperature significantly higher than the liquid boiling point, an explosive interaction, involving sudden fragmentation of some of the molten material and rapid evaporation of the liquid, takes place. This phenomenon is referred to as a "vapor explosion" or "steam explosion". In the event of a core meltdown accident in a light water reactor, the molten fuel can interact with cooling water inside or outside the reactor vessel and cause a vapor explosion. The mechanical energy released during such an explosion can result in structural damage, and ultimately may lead to the release of radioactive material into the environment. Vapor explosions are extremely fast transients, involving a flow field consisting of at least three distinct phases, accompanied by thermal non-equilibrium and strong interfacial transfer processes. The objective of this research was to mechanistically model the expansion phase of a vapor explosion. A transient three-dimensional, three -fluid thermal hydraulic model was developed. Coolant liquid plus fragmented fuel particles, coolant vapor plus noncondensables and unfragmented fuel constitute the three fluids. Hydrodynamic and thermal interactions between the three phases were mechanistically treated, using flow regime-dependent models. The models were incorporated into a computer code, in which the conservation equations are cast in finite-difference form and are numerically solved using the point-relaxation method. The code was utilized in parametric and sensitivity calculations aimed at assessing the significance of interfacial transfer processes, and the effect of the premixture initial conditions on the phenomenology of the expansion phase of steam explosions. The initial conditions for the expansion phase were estimated by assuming that the propagation phase was a constant volume heat exchange process. Parametric results indicate that thermal and mechanical nonequilibrium are both significant. Various modelling assumptions relevant to the inter-phase transfer coefficients could change the predicted magnitude of the conversion ratio by up to a factor of two. The parametric results were extremely sensitive to the initial void fraction in the premixture prior to the propagation. The calculated conversion ratios varied by an order of magnitude as a result of varying the aforementioned initial void fraction.

  19. Supported complex catalysts for vapor-phase carbonylations

    SciTech Connect

    Bischoff, S.; Weigt, A.; Kant, M.; Schuelke, U.

    1996-10-01

    Supported mixed bidentate rhodium and iridium complexes derived from phosphonate-phosphanes have been studied in methanol carbonylation and in ethylene hydroformylation. The complexes showed higher activities than bis-phosphane complexes in homogeneous and vapor-phase methanol carbonylation. Hemilabile behavior of the mixed bidentate complexes may explain these findings. In contrast to strongly chelating ligands, phosphonate-phosphane ligands improved the selectivity of supported rhodium complexes in ethylene hydroformylation. Mixed zirconium phosphonate structures containing phosphane groups afforded excellent heterogeneous rhodium complex catalysts. The zirconium phosphonate-phosphane-rhodium catalysts were several times more active than rhodium on silica or rhodium on activated carbon, showed a superior stability, and produced butyraldehydes with up to 96% selectivity in the vapor-phase hydroformylation of propylene.

  20. Superfluid helium 2 liquid-vapor phase separation: Technology assessment

    NASA Technical Reports Server (NTRS)

    Lee, J. M.

    1984-01-01

    A literature survey of helium 2 liquid vapor phase separation is presented. Currently, two types of He 2 phase separators are being investigated: porous, sintered metal plugs and the active phase separator. The permeability K(P) shows consistency in porous plug geometric characterization. Both the heat and mass fluxes increase with K(P). Downstream pressure regulation to adjust for varying heat loads and both temperatures is possible. For large dynamic heat loads, the active phase separator shows a maximum heat rejection rate of up to 2 W and bath temperature stability of 0.1 mK. Porous plug phase separation performance should be investigated for application to SIRTF and, in particular, that plugs of from 10 to the minus ninth square centimeters to 10 to the minus eighth square centimeters in conjunction with downstream pressure regulation be studied.

  1. QCM Studies of Alcohols as Vapor Phase Lubricants for MEMS

    NASA Astrophysics Data System (ADS)

    Nemetz, Heather; Jones, Jon; Coffey, Tonya

    2006-11-01

    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).

  2. Metal Organic Vapor Phase Growth of Complex Semiconductor Alloys

    SciTech Connect

    Kuech, Thomas F.

    2010-07-22

    The metalorganic vapor phase epitaxy of semiconductor materials has been developed over the past three decades and has focused on the synthesis of semiconductors and alloys useful in the formation of optoelectronic and high speed electronic devices. These materials are currently binary semiconductors or alloys which have broad miscibility. The extension to alloy systems which are highly immiscible in bulk form requires modification to conventional growth systems preventing the nucleation and growth of multiple compositional phases. The general features of MOVPE as it relates to the growth of complex alloys is developed within the current framework of MOVPE technology.

  3. Vapor-phase biofiltration: Laboratory and field experience

    SciTech Connect

    Evans, P.J.; Bourbonais, K.A.; Peterson, L.E.; Lee, J.H.; Laakso, G.L.

    1995-12-31

    Application of vapor-phase bioreactors (VPBs) to petroleum hydrocarbons is complicated by the different mass transfer characteristics of aliphatics and aromatics. Laboratory- and pilot-scale VPB studies were conducted to evaluate treatment of soil vapor extraction (SVE) off-gas. A mixture of compost, perlite, and activated carbon was the selected medium based on pressure drop, microbial colonization, and adsorption properties. Two different pilot-scale reactors were built with a difference of 70:1 in scale. The smaller VPB`s maximum effective elimination capacity (EC) was determined to be 7.2 g m{sup {minus}3} h{sup {minus}1}; the larger unit`s EC was 70% to 80% of this value. Low EC values may be attributable to a combination of mass-transfer and kinetic limitations.

  4. Crystal growth from the vapor phase experiment MA-085

    NASA Technical Reports Server (NTRS)

    Wiedemeir, H.; Sadeek, H.; Klaessig, F. C.; Norek, M.

    1976-01-01

    Three vapor transport experiments on multicomponent systems were performed during the Apollo Soyuz mission to determine the effects of microgravity forces on crystal morphology and mass transport rates. The mixed systems used germanium selenide, tellurium, germanium tetraiodide (transport agent), germanium monosulfide, germanium tetrachloride (transport agent), and argon (inert atmosphere). The materials were enclosed in evacuated sealed ampoules of fused silica and were transported in a temperature gradient of the multipurpose electric furnace onboard the Apollo Soyuz spacecraft. Preliminary evaluation of 2 systems shows improved quality of space grown crystals in terms of growth morphology and bulk perfection. This conclusion is based on a direct comparison of space grown and ground based crystals by means of X-ray diffraction, microscopic, and chemical etching techniques. The observation of greater mass transport rates than predicted for a microgravity environment by existing vapor transport models indicates the existence of nongravity caused transport effects in a reactive solid/gas phase system.

  5. Vapors-liquid phase separator. [infrared telescope heat sink

    NASA Technical Reports Server (NTRS)

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

    1980-01-01

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

  6. Liquid to vapor phase transition in excited nuclei.

    PubMed

    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

    2002-01-28

    The thermal component of the 8 GeV/c pi+ Au data of the ISiS Collaboration is shown to follow the scaling predicted by Fisher's model when Coulomb energy is taken into account. Critical exponents tau and sigma, the critical point (p(c),rho(c),T(c)), surface energy coefficient c(0), enthalpy of evaporation DeltaH, and critical compressibility factor C(F)(c) are determined. For the first time, the experimental phase diagrams, (p,T) and (T,rho), describing the liquid vapor coexistence of finite neutral nuclear matter have been constructed. PMID:11801117

  7. Vapor Phase Filling of Single Wall Carbon Nanotubes with Cesium

    NASA Astrophysics Data System (ADS)

    Nemes, Norbert; Smith, Brian; Luzzi, David; Fischer, John

    2000-03-01

    Techniques for filling single wall carbon nanotubes (SWNTs) with alkali metals could enable the synthesis of a new family of functional materials. In this work, we investigate the filling of SWNTs with cesium using a vapor phase process. The method is a natural extension of the mechanism by which SWNTs are filled with C_60 molecules (B. W. Smith and D. E. Luzzi, submitted 1999). Observation by high resolution transmission electron microscopy (HRTEM) reveals the presence of cesium inside SWNTs. X-ray diffraction (XRD), electron spin resonance (ESR), and electronic transport measurements of this material are discussed.

  8. Modeling of Gallium Nitride Hydride Vapor Phase Epitaxy

    NASA Technical Reports Server (NTRS)

    Meyyappan, Meyya; Arnold, James O. (Technical Monitor)

    1997-01-01

    A reactor model for the hydride vapor phase epitaxy of GaN is presented. The governing flow, energy, and species conservation equations are solved in two dimensions to examine the growth characteristics as a function of process variables and reactor geometry. The growth rate varies with GaCl composition but independent of NH3 and H2 flow rates. A change in carrier gas for Ga source from H2 to N2 affects the growth rate and uniformity for a fixed reactor configuration. The model predictions are in general agreement with observed experimental behavior.

  9. Simultaneous Vapor Deposition and Phase Separation of Polymer Films

    NASA Astrophysics Data System (ADS)

    Tao, Ran; Anthamatten, Mitchell

    2012-02-01

    Initiated chemical vapor deposition (iCVD) is a solventless, free radical technique used predominately to deposit homogeneous films of linear and crosslinked polymers directly from gas phase feeds. The major goal of this research is to force and arrest phase separation of deposited species by co-depositing non-reactive molecules (porogens) with reactive monomers and crosslinkers. We introduce these species during iCVD to force and quench polymer induced phase separation (PIPS) during film growth as a step toward tunable pore-size, density, and morphology. Polymerization, crosslinking and PIPS are intended to occur simultaneously on the substrate, resulting in a vitrified microstructure. Cahn-Hilliard theory predicts that the length scale of phase separation depends on the polymer-porogen interaction energy, the polymerization rate and the species' mobility. A series of films were grown by varying deposition rate, porogen type, and reagent flowrates. Crosslinkers were introduced to limit the growth of phase separated domains and to provide mechanical support during porogen removal. To elucidate how phase separation competes with polymerization and film growth, deposited films were studied using a combination of electron microscopy, profilometry and spectroscopic techniques.

  10. A load dampening system for vapor phase bioreactors

    SciTech Connect

    Al-Rayes, A.W.; Kinney, K.A.; Seibert, F.; Corsi, R.L.

    1999-07-01

    Vapor phase bioreactors have been used extensively to control odorous gases and are receiving increased attention as an efficient and cost-effective treatment method for volatile organic compound (VOC) emissions. However, an important issue related to bioreactors is their high sensitivity to shock loads and periods of process shutdown, which can significantly reduce treatment efficiency. The focus of this paper is the use of a novel closed absorption and humidification system to dampen dynamic loads of toluene, methyl tert butyl ether (MTBE), and acetone, and to reduce their detrimental effect on a downstream bioreactor. A model based on the mass transfer characteristics of target pollutants was developed and takes into account the closed water recirculation loop that minimizes fugitive emissions and simultaneously humidifies the influent gas stream. When water is used as the scrubbing liquid, model and experimental results indicate that the system effectively dampens hydrophilic compounds and segregates them from the hydrophobic compounds in the waste gas stream. The response of a vapor phase bioreactor to the pretreated stream has also been assessed and shows that the system works effectively with hydrophilic, but not hydrophobic, VOCs.

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

    PubMed

    Kida, Nori; Mochizuki, Yasushi; Taguchi, Fumiaki

    2007-01-01

    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

  12. Graphene oxide bound silica for solid-phase extraction of 14 polycyclic aromatic hydrocarbons in mainstream cigarette smoke.

    PubMed

    Shi, Rui; Yan, Lihong; Xu, Tongguang; Liu, Dongye; Zhu, Yongfa; Zhou, Jun

    2015-01-01

    Polycyclic aromatic hydrocarbons (PAHs) were considered as a source of carcinogenicity in mainstream cigarette smoke (MSS). Accurate quantification of these components was necessary for assessing public health risk. In our study, a solid-phase extraction (SPE) method using graphene oxide (GO) bound silica as adsorbent for purification of 14 PAHs in MSS was developed. During SPE process, large matrices interferences of MSS were adsorbed on SPE column. The result of FTIR spectra demonstrated that these matrices interferences were adsorbed on GO mainly through OH and CO groups. The concentrations of PAHs in MSS extract were determined by gas chromatography-mass spectrometry (GC-MS). The limit of detection (LOD) and limit of quantification (LOQ) of the developed method for 14 PAHs ranged from 0.05 to 0.36 ng/cig and 0.17 to 1.19 ng/cig, respectively. The accuracy of the measurement of 14 PAHs was from 73 to 116%. The relative standard deviations of intra- and inter-day analysis were less than 7.8% and 13.9%, respectively. Moreover, the developed method was successfully applied for analysis of real cigarette containing 1R5F reference cigarette and 12 top-selling commercial cigarettes in China. PMID:25512123

  13. Sex Differences and Menstrual Cycle Phase-Dependent Modulation of Craving for Cigarette: An fMRI Pilot Study

    PubMed Central

    Dinh-Williams, Laurence; Bourque, Josiane; Potvin, Stphane

    2014-01-01

    While overall more men than women smoke cigarettes, women and girls take less time to become dependent after initial use and have more difficulties quitting the habit. One of the factors contributing to these differences may be that women crave cigarettes more than men and that their desire to smoke is influenced by hormonal fluctuations across the menstrual cycle. Therefore, the purpose of the present study was twofold: (a) to examine potential sex/gender differences in functional neuroanatomy of craving and to (b) delineate neural correlates of cigarette cravings in women across their menstrual cycle. Fifteen tobacco-smoking men and 19 women underwent a functional MRI during presentation of neutral and smoking-related images, known to elicit craving. Women were tested twice: once during early follicular phase and once during midluteal phase of their menstrual cycle. The analysis did not reveal any significant sex differences in the cerebral activations associated with craving. Nevertheless, the pattern of activations in women varied across their menstrual cycle with significant activations in parts of the frontal, temporal, and parietal lobe, during follicular phase, and only limited activations in the right hippocampus during the luteal phase. PMID:25478563

  14. Evidence of Phase Separation during Vapor Deposition Polymerization

    NASA Astrophysics Data System (ADS)

    Tao, Ran; Anthamatten, Mitchell

    2013-03-01

    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.

  15. Vapor phase mediated cellular uptake of sub 5 nm nanoparticles

    NASA Astrophysics Data System (ADS)

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

    2012-04-01

    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.

  16. Melt-vapor phase transition in the lead-selenium system at atmospheric and low pressure

    NASA Astrophysics Data System (ADS)

    Volodin, V. N.; Burabaeva, N. M.; Trebukhov, S. A.

    2016-03-01

    The boiling temperature and the corresponding vapor phase composition in the existence domain of liquid solutions were calculated from the partial pressures of saturated vapor of the components and lead selenide over liquid melts in the lead-selenium system. The phase diagram was complemented with the liquid-vapor phase transition at atmospheric pressure and in vacuum of 100 Pa, which allowed us to judge the behavior of the components during the distillation separation.

  17. 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 ?g/L (25C). Vapor samples were drawn by vacuum into a six-port sampling valve and injected through a jet separator into an io...

  18. Vapor-phase molar Kerr constant values from solution measurements

    NASA Astrophysics Data System (ADS)

    Prezhdo, Victor; Olan, Karol; Prezhdo, Oleg; Zubkova, Valentina

    2015-01-01

    A method is proposed for determination of molar Kerr constants (mK) by extrapolation of the values measured in a series of selected solvents. The mK values of 19 organic compounds were calculated. Most of the compounds cannot be studied in the vapor phase. The discrete-continuum solvation model was applied to investigate the influence of solvent nature on solubility of the compounds under investigation. It is shown that universal interactions between the solvent and solute molecules, including the dispersive, inductive, and dipole-dipole interactions, dominate the solvation process. The optimum model of internal field was chosen to determine the Kerr constant. The values of mKgas measured experimentally coincide with the values of mK??= 0 ? that were obtained by extrapolation of mK?. Hence, this method can be applied to calculate the values of molar Kerr constants on the basis of measurements in solutions.

  19. Quantitative Infrared Spectra of Vapor Phase Chemical Agents

    SciTech Connect

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

    2003-08-01

    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 Beers 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).

  20. Quantitative infrared spectra of vapor phase chemical agents

    NASA Astrophysics Data System (ADS)

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

    2003-08-01

    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).

  1. A High Temperature Vapor Phase Lubrication Study Utilizing a Thioether Liquid Lubricant

    NASA Technical Reports Server (NTRS)

    Morales, Wilfredo; Graham, E. Earl; Galvin, Thomas

    1997-01-01

    Much of the experimental work on vapor phase lubrication has employed certain organo phosphorous compounds as the vapor phase lubricant. Graham and Klaus, for instance, used tricresyl phosphate (TCP) and tributyl phosphate to vapor phase lubricate a four-ball wear tester using M50 steel balls at 370 C. Makki and Graham were able to vapor phase lubricate a reciprocating pin on plate tribometer using 1018 steel at 280 C with TCP vapor. Although a few organo phosphorous compounds, such as TCP, have been successfully used as vapor phase lubricants in many laboratory experiments, many problems remain unsolved. Two areas of concern relate to the 'durability' of phosphate deposited films and to the ability of the lubricating system to "self-recover" when vapor phase lubricated with an organo phosphorous compound. Durability refers to the ability of the deposited film to provide effective lubrication, for a period of time, after the vapor flow to the lubricating surfaces has been interrupted. Vapor phase lubrication tests, conducted at Cleveland State University with their high temperature tribometer, revealed that when TCP vapor flow to the lubricating surfaces was interrupted the frictional coefficient of the system rapidly increased from a value less than 0.1 to a value of 0.3 which was selected as our failure point. Self-recovery means the ability of the vapor phase lubricant to reduce the frictional coefficient of the lubricating system back down to value less than 0.1 after startup of the interrupted vapor flow. Lubrication tests conducted at Cleveland State University revealed that the high temperature tribometer could not self-recover after startup of the interrupted TCP vapor flow.

  2. Sensitive and selective determination of polycyclic aromatic hydrocarbons in mainstream cigarette smoke using a graphene-coated solid-phase microextraction fiber prior to GC/MS.

    PubMed

    Wang, Xiaoyu; Wang, Yuan; Qin, Yaqiong; Ding, Li; Chen, Yi; Xie, Fuwei

    2015-08-01

    A simple method has been developed for the simultaneous determination of 16 polycyclic aromatic hydrocarbons (PAHs) in mainstream cigarette smoke. The procedure is based on employing a homemade graphene-coated solid-phase microextraction (SPME) fiber for extraction prior to GC/MS. In comparison to commercial 100-?m poly(dimethyl siloxane) (PDMS) fiber, the graphene-coated SPME fiber exhibits advantageous cleanup and preconcentration efficiencies. By collecting the particulate phase 5 cigarettes, the LODs and LOQs of 16 target PAHs were 0.02-0.07 and 0.07-0.22 ng/cigarette, respectively, and all of the linear correlation efficiencies were larger than 0.995. The validation results also indicate that the method has good repeatability (RSD between 4.2% and 9.5%) and accuracy (spiked recoveries between 80% and 110%). The developed method was applied to analyze two Kentucky reference cigarettes (1R5F and 3R4F) and six Chinese brands of cigarettes. In addition, the PAH concentrations in the particulate phase of the smoke from the 1R5F Kentucky cigarettes were in good agreement with recently reported results. Due to easy operation and good validation results, this SPME-GC/MS method may be an excellent alternative for trace analysis of PAHs in cigarette smoke. PMID:26048830

  3. Condensed-phase transitions in binary systems during dynamic vaporization experiments. Effusion and transpiration

    SciTech Connect

    Edwards, J.G.; Franzen, H.F.

    1995-03-30

    During a condensed-phase transition at equilibrium in a vaporization experiment, three phases are present. In this paper, equations relating vapor pressure, temperature, and compositions of the vapor and condensed phases are derived for systems undergoing such transitions. Previously observed unusual phenomena, such as vapor pressures that increase at constant temperature and vapor pressures that increase with decreasing temperature, are explained. It is shown that equilibrium condensed-phase transitions in the presence of the vapor are always hysteretic in the temperature; the transition occurs at a higher temperature in the increasing-temperature direction than in the decreasing-temperature direction. The particular cases of effusion and transpiration experiments are treated in detail. 31 refs., 5 figs.

  4. Liquid-vapor phase equilibrium in a tin-selenium system

    NASA Astrophysics Data System (ADS)

    Volodin, V. N.; Burabaeva, N. M.; Trebukhov, S. A.

    2014-12-01

    Based on the pressure of the saturated vapor and components over liquid alloys in a tin-selenium system, determined using the boiling points approach (isothermal variant), its boiling point and corresponding vapor phase composition are calculated in the region of liquid solutions. The phase diagram is supple-mented with the liquid-vapor phase transition under atmospheric pressure and in vacuums of 100 and 10 Pa with the boundaries of the region in which the regions of liquid and vapor coexist being determined.

  5. 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...

  6. Vapor phase elemental sulfur amendment for sequestering mercury in contaminated soil

    DOEpatents

    Looney, Brian B.; Denham, Miles E.; Jackson, Dennis G.

    2014-07-08

    The process of treating elemental mercury within the soil is provided by introducing into the soil a heated vapor phase of elemental sulfur. As the vapor phase of elemental sulfur cools, sulfur is precipitated within the soil and then reacts with any elemental mercury thereby producing a reaction product that is less hazardous than elemental mercury.

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

    SciTech Connect

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

    2002-11-14

    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.

  8. Vapor phase deposition of transition metal fluoride glasses

    NASA Astrophysics Data System (ADS)

    Boulard, Brigitte; Jacoboni, Charles

    1991-08-01

    Multicomponent fluoride glasses in the PbF2-ZnF2-GaF3 (PZG) vitreous ternary system have been prepared by vapor phase deposition. The thermal stability of the deposited glass was improved by adding stabilizing agents (AlF3, NaF, LiF, InF3). The thin films, deposited on different substrates (fluoride glass, fluoride single crystal, metal, and silica glass) have been characterized by x-ray diffraction. Differential scanning calorimetry (DSC) and secondary ion mass spectroscopy (SIMS). The quality of the film, adherence, and homogeneity was controlled by scanning electronic microscopy (SEM). The optical characteristics of the film and PZG glass are given: the visible-infrared (VIS-IR) window is 0.3-8 micrometers and the refractive index 1.59+/- 0.2 depends on the lead content. Mn2+ doped films (up to 3 mole % MnF2) are optically active: Mn2+ exhibits a broad luminescence band at 560-570 nm (orange). The achieved film thickness varies from 0.5 to 80 micrometers , and the refractive index gradient approaches the required geometry for planar waveguides (doping of the film with lanthanides is in progress).

  9. Liquid-vapor phase diagram of metals using EAM potential

    NASA Astrophysics Data System (ADS)

    Bhattacharya, Chandrani

    2013-02-01

    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.

  10. Non-aqueous phase liquid spreading during soil vapor extraction

    PubMed Central

    Kneafsey, Timothy J.; Hunt, James R.

    2010-01-01

    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. PMID:14734243

  11. Numerical Modeling of Liquid-Vapor Phase Change

    NASA Technical Reports Server (NTRS)

    Esmaeeli, Asghar; Arpaci, Vedat S.

    2001-01-01

    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, we used a single formula representation which incorporated jump conditions into the governing equations. The interfacial terms were distributed as singular terms using delta functions so that the governing equations would be the same as conventional conservation equations away from the interface and in the vicinity of the interface they would provide correct jump conditions. We used a fixed staggered grid to discretize these equations and an unstructured grid to explicitly track the front. While in two dimensions the front was simply a connection of small line segments, in three dimensions it was represented by a connection of small triangular elements. The equations were written in conservative forms and during the course of computations we used regriding to control the size of the elements of the unstructured grid. Moreover, we implemented a coalescence in two dimensions which allowed the merging of different fronts or two segments of the same front when they were sufficiently close. We used our code to study thermocapillary migration of bubbles, burst of bubbles at a free surface, buoyancy-driven interactions of bubbles, evaporation of drops, rapid evaporation of an interface, planar solidification of an undercooled melt, dendritic solidification, and a host of other problems cited in the reference.

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

    SciTech Connect

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

    1996-05-01

    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.

  13. Crystallization from a vapor phase in igneous rocks -- A conceptual model

    SciTech Connect

    Kleck, W.D. )

    1993-04-01

    Euhedral, late-stage crystals in pocket pegmatite and in vesicles of volcanic rocks are commonly cited as examples of crystallization from a vapor phase. If, however, crystallization takes place only from the cavity forming vapor, that vapor cannot contain sufficient material for the formation of the observed crystals. The approximate amount of H[sub 2]O vapor and percentage of dissolved silicate matter (1) for shallow pocket pegmatite is 0.5 g/cm[sup 3] and 0.3 percent; (2) for vesicles is 0.002 g/cm[sup 3] and [much lt]1 percent. These values show that the silicate matter dissolved in the vapor is insufficient for the formation of the observed crystals. No (or little) recharge of the vapor is an unstated assumption in most discussions of enclosed cavities. This, however, is not quite correct. For a simplified system, four phases will exist in equilibrium: (1) mineral grains growing from liquid, (2) late-stage, H[sub 2]O-enriched, silicate liquid, (3) vapor, (4) crystals growing from vapor. The total system (for transferal of silicate matter) is given. Little silicate matter is dissolved in the vapor at any one time, but it is replenished as the crystals grow. The vapor becomes a continuously resupplied reservoir of dissolved silicate matter; crystallization from the vapor continues until the silicate liquid is depleted.

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

    SciTech Connect

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

    1993-09-01

    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{sub x}Zr{sub 1-x}C{sub y} in hydrogen at 2500 to 3200 K. This model demonstrates that steady state corrosion of U{sub x}Zr{sub l-x}C{sub 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.

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

    PubMed

    Zu, Baiyi; Guo, Yanan; Dou, Xincun

    2013-11-21

    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

  16. Underwater vapor phase burning of aluminum particles and on aluminum ignition during steam explosions

    SciTech Connect

    Epstein, M.

    1991-09-01

    Recently reported experimental studies on aluminum-water steam explosions indicate that there may be a critical metal temperature at which the process changes over from a physical explosion to one which is very violent and involves the rapid liberation of chemical energy. In this report we examine the hypothesis that vapor-phase burning of aluminum is a necessary condition for the occurrence of such ``ignition-type`` steam explosions. An available two-phase stagnation flow film-boiling model is used to calculate the steam flux to the vaporizing aluminum surface. Combining this calculation with the notion that there is an upper limit to the magnitude of the metal vaporization rate at which the reaction regime must change from vapor phase to surface burning, leads to prediction of the critical metal surface temperature below which vapor phase burning is impossible. The critical temperature is predicted for both the aluminum-water pre-mixture configuration in which coarse drops of aluminum are falling freely through water and for the finely-fragmented aluminum drops in the wake of the pressure shock that ``triggers`` the explosion. Vapor phase burning is predicted to be possible during the pre-mixture phase but not very likely during the trigger phase of a steam explosion. The implications of these findings in terms of the validity of the hypothesis that ignition may begin with the vapor phase burning of aluminum is discussed. Recently postulated, alternative mechanisms of underwater aluminum ignition are also discussed.

  17. Underwater vapor phase burning of aluminum particles and on aluminum ignition during steam explosions

    SciTech Connect

    Epstein, M. )

    1991-09-01

    Recently reported experimental studies on aluminum-water steam explosions indicate that there may be a critical metal temperature at which the process changes over from a physical explosion to one which is very violent and involves the rapid liberation of chemical energy. In this report we examine the hypothesis that vapor-phase burning of aluminum is a necessary condition for the occurrence of such ignition-type'' steam explosions. An available two-phase stagnation flow film-boiling model is used to calculate the steam flux to the vaporizing aluminum surface. Combining this calculation with the notion that there is an upper limit to the magnitude of the metal vaporization rate at which the reaction regime must change from vapor phase to surface burning, leads to prediction of the critical metal surface temperature below which vapor phase burning is impossible. The critical temperature is predicted for both the aluminum-water pre-mixture configuration in which coarse drops of aluminum are falling freely through water and for the finely-fragmented aluminum drops in the wake of the pressure shock that triggers'' the explosion. Vapor phase burning is predicted to be possible during the pre-mixture phase but not very likely during the trigger phase of a steam explosion. The implications of these findings in terms of the validity of the hypothesis that ignition may begin with the vapor phase burning of aluminum is discussed. Recently postulated, alternative mechanisms of underwater aluminum ignition are also discussed.

  18. 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...

  19. Cigarette smoke extract increases albumin flux across pulmonary endothelium in vitro

    SciTech Connect

    Holden, W.E.; Maier, J.M.; Malinow, M.R.

    1989-01-01

    Cigarette smoking causes lung inflammation, and a characteristic of inflammation is an increase in vascular permeability. To determine if cigarette smoke could alter endothelial permeability, we studied flux of radiolabeled albumin across monolayers of porcine pulmonary artery endothelium grown in culture on microporous membranes. Extracts (in either dimethylsulfoxide or phosphate-buffered saline) of cigarette smoke in a range estimate of concentrations simulating cigarette smoke exposure to the lungs in vivo caused a dose-dependent increase in albumin flux that was dependent on extracellular divalent cations and associated with polymerization of cellular actin. The effect was reversible, independent of the surface of endothelial cells exposed (either luminal or abluminal), and due primarily to components of the vapor phase of smoke. The effects occurred without evidence of cell damage, but subtle morphological changes were produced by exposure to the smoke extracts. These findings suggest that cigarette smoke can alter permeability of the lung endothelium through effects on cytoskeletal elements.

  20. VAPOR-PHASE DECONTAMINATION OF APPLES CONTAINING ESCHERICHIA COLI

    Technology Transfer Automated Retrieval System (TEKTRAN)

    Improved methods of decontaminating apples containing human pathogens are required. In this investigation, application of gaseous antimicrobial agents was investigated. An apparatus, which transfers vapor from hot antimicrobial solutions to a treatment vessel, was evaluated with Golden Delicious app...

  1. Using vapor phase tomography to measure the spatial distribution of vapor concentrations and flux for vadose-zone VOC sources.

    PubMed

    Mainhagu, J; Morrison, C; Brusseau, M L

    2015-01-01

    A test was conducted at a chlorinated-solvent contaminated site in Tucson, AZ, to evaluate the effectiveness of vapor-phase tomography (VPT) for characterizing the distribution of volatile organic contaminants (VOC) in the vadose zone. A soil vapor extraction (SVE) system has been in operation at the site since 2007. Vapor concentration and vacuum pressure were measured at four different depths in each of the four monitoring wells surrounding the extraction well. The test provided a 3D characterization of local vapor concentrations under induced-gradient conditions. Permeability data obtained from analysis of borehole logs were used along with pressure and the vapor-concentration data to determine VOC mass flux within the test domain. A region of higher mass flux was identified in the deepest interval of the S-SW section of the domain, indicating the possible location of a zone with greater contaminant mass. These results are consistent with the TCE-concentration distribution obtained from sediment coring conducted at the site. In contrast, the results of a standard soil gas survey did not indicate the presence of a zone with greater contaminant mass. These results indicate that the VPT test provided a robust characterization of VOC concentration and flux distribution at the site. PMID:25835545

  2. Using vapor phase tomography to measure the spatial distribution of vapor concentrations and flux for vadose-zone VOC sources

    NASA Astrophysics Data System (ADS)

    Mainhagu, J.; Morrison, C.; Brusseau, M. L.

    2015-06-01

    A test was conducted at a chlorinated-solvent contaminated site in Tucson, AZ, to evaluate the effectiveness of vapor-phase tomography (VPT) for characterizing the distribution of volatile organic contaminants (VOC) in the vadose zone. A soil vapor extraction (SVE) system has been in operation at the site since 2007. Vapor concentration and vacuum pressure were measured at four different depths in each of the four monitoring wells surrounding the extraction well. The test provided a 3D characterization of local vapor concentrations under induced-gradient conditions. Permeability data obtained from analysis of borehole logs were used along with pressure and the vapor-concentration data to determine VOC mass flux within the test domain. A region of higher mass flux was identified in the deepest interval of the S-SW section of the domain, indicating the possible location of a zone with greater contaminant mass. These results are consistent with the TCE-concentration distribution obtained from sediment coring conducted at the site. In contrast, the results of a standard soil gas survey did not indicate the presence of a zone with greater contaminant mass. These results indicate that the VPT test provided a robust characterization of VOC concentration and flux distribution at the site.

  3. Sorption capacity of ground tires for vapor-phase volatile organic compounds

    SciTech Connect

    Kim, J.Y.; Park, J.K.; Edil, T.B.; Jhung, J.K.

    1996-12-31

    Batch sorption tests were conducted to determine the partition coefficient of volatile organic compounds (VOCs) by ground tires. The partition coefficient in the vapor phase was estimated by dividing the partition coefficient in the aqueous phase by Henry`s law constant. Under a diluted condition VOCs are sorbed onto ground tires noncompetitively regardless of the existence of other VOCs. Polar compounds such as methylene chloride were less sorbed onto ground tires than nonpolar compounds. The vapor-phase partition coefficient was found to have a logarithmic relationship with the saturation vapor concentration. VOCs emitted from waste-water treatment facilities can be effectively retarded by the ground tires.

  4. Comparative Study of Solution Phase and Vapor Phase Deposition of Aminosilanes on Silicon Dioxide Surfaces

    PubMed Central

    Yadav, Amrita R.; Sriram, Rashmi; Carter, Jared A.; Miller, Benjamin L.

    2014-01-01

    The uniformity of aminosilane layers typically used for the modification of hydroxyl bearing surfaces such as silicon dioxide is critical for a wide variety of applications, including biosensors. However, in spite of many studies that have been undertaken on surface silanization, there remains a paucity of easy-to-implement deposition methods reproducibly yielding smooth aminosilane monolayers. In this study, solution- and vapor-phase deposition methods for three aminoalkoxysilanes differing in the number of reactive groups (3-aminopropyl triethoxysilane (APTES), 3-aminopropyl methyl diethoxysilane (APMDES) and 3-aminopropyl dimethyl ethoxysilane (APDMES)) were assessed with the aim of identifying methods that yield highly uniform and reproducible silane layers that are resistant to minor procedural variations. Silane film quality was characterized based on measured thickness, hydrophilicity and surface roughness. Additionally, hydrolytic stability of the films was assessed via these thickness and contact angle values following desorption in water. We found that two simple solution-phase methods, an aqueous deposition of APTES and a toluene based deposition of APDMES, yielded high quality silane layers that exhibit comparable characteristics to those deposited via vapor-phase methods. PMID:24411379

  5. Vapor-phase preparation of gold nanocrystals by chloroauric acid pyrolysis.

    PubMed

    Chen, Yiqin; Tian, Xuezeng; Zeng, Wei; Zhu, Xupeng; Hu, Hailong; Duan, Huigao

    2015-02-01

    We report that gold nanocrystals can be prepared from vapor phase using chloroauric acid (HAuCl4) as the precursor. By tuning the vapor-phase deposition parameters, the size and space distribution of the gold nanocrystals can be well controlled on substrates. Systematic control experiments demonstrate that intermediate AuCl and AuCl3 products pyrolyzed from HAuCl4 play an essential role in this vapor-phase deposition process. Compared to conventional wet-chemical synthesis process, vapor-phase process enables direct deposition of gold nanoparticles on solid substrates with better coverage and uniformity, which may find applications in surface-enhanced Raman scattering and plasmon-enhanced photocatalysis. PMID:25463171

  6. Stand-off detection of vapor phase explosives by resonance enhanced Raman spectroscopy

    NASA Astrophysics Data System (ADS)

    Ehlerding, Anneli; Johansson, Ida; Wallin, Sara; stmark, Henric

    2010-10-01

    Stand-off measurements on nitromethane (NM), 2,4-DNT and 2,4,6-TNT in vapor phase using resonance Raman spectroscopy have been performed. The Raman cross sections for NM, DNT and TNT in vapor phase have been measured in the wavelength range 210-300 nm under laboratory conditions, in order to estimate how large resonance enhancement factors can be achieved for these explosives. The measurements show that the signal is greatly enhanced, up to 250.000 times for 2,4-DNT and 60.000 times for 2,4,6-TNT compared to the non-resonant signal at 532 nm. For NM the resonance enhancement enabled realistic outdoor measurements in vapor phase at 13 m distance. This all indicate a potential for resonance Raman spectroscopy as a stand-off technique for detection of vapor phase explosives.

  7. Epitaxial growth of phase-pure ?-Ga2O3 by halide vapor phase epitaxy

    NASA Astrophysics Data System (ADS)

    Oshima, Yuichi; Vllora, Encarnacin G.; Matsushita, Yoshitaka; Yamamoto, Satoshi; Shimamura, Kiyoshi

    2015-08-01

    Epitaxial growth of ?-Ga2O3 is demonstrated for the first time. The ?-Ga2O3 films are grown on GaN (0001), AlN (0001), and ?-Ga2O3 ( 2 01 ) by halide vapor phase epitaxy at 550 C using gallium chloride and O2 as precursors. X-ray ?-2? and pole figure measurements prove that phase-pure ?-Ga2O3 (0001) films are epitaxially grown on the three kinds of substrates, although some minor misoriented domains are observed. High temperature X-ray diffraction measurements reveal that the ?-Ga2O3 is thermally stable up to approximately 700 C. The optical bandgap of ?-Ga2O3 is determined for the first time to be 4.9 eV.

  8. Student Understanding of Liquid-Vapor Phase Equilibrium

    ERIC Educational Resources Information Center

    Boudreaux, Andrew; Campbell, Craig

    2012-01-01

    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

  9. Vapor Phase Detection Using Chemi-Resistor Sensor Arrays

    SciTech Connect

    Nathan S. Lewis

    1999-02-17

    This paper focuses on two main areas: understanding sensor response times so as to obtain improved time response in the field when needed for vapor tracking and classification, and improved theoretical understanding of the sensor response properties that generate the pattern on the array in response to a given analyte.

  10. Student Understanding of Liquid-Vapor Phase Equilibrium

    ERIC Educational Resources Information Center

    Boudreaux, Andrew; Campbell, Craig

    2012-01-01

    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…

  11. DETERMINING HOW VAPOR PHASE MTBE REACHES GROUND WATER

    EPA Science Inventory

    EPA Region 2 and ORD have funded a RARE project for FY 2005/2006 to evaluate the prospects that MTBE (and other fuel components) in vapors that escape from an underground storage tank (UST) can find its way to ground water produced by monitoring wells at a gasoline filling statio...

  12. A comparative assessment of cigarette smoke aerosols using an in vitro air-liquid interface cytotoxicity test.

    PubMed

    Thorne, David; Dalrymple, Annette; Dillon, Deborah; Duke, Martin; Meredith, Clive

    2015-10-01

    This study describes the evaluation of a modified air-liquid interface BALB/c 3T3 cytotoxicity method for the assessment of smoke aerosols in vitro. The functionality and applicability of this modified protocol was assessed by comparing the cytotoxicity profiles from eight different cigarettes. Three reference cigarettes, 1R5F, 3R4F and CORESTA Monitor 7 were used to put the data into perspective and five bespoke experimental products were manufactured, ensuring a balanced and controlled study. Manufactured cigarettes were matched for key variables such as nicotine delivery, puff number, pressure drop, ventilation, carbon monoxide, nicotine free dry particulate matter and blend, but significantly modified for vapor phase delivery, via the addition of two different types and quantities of adsorptive carbon. Specifically manufacturing products ensures comparisons can be made in a consistent manner and allows the research to ask targeted questions, without confounding product variables. The results demonstrate vapor-phase associated cytotoxic effects and clear differences between the products tested and their cytotoxic profiles. This study has further characterized the in vitro vapor phase biological response relationship and confirmed that the biological response is directly proportional to the amount of available vapor phase toxicants in cigarette smoke, when using a Vitrocell VC 10 exposure system. This study further supports and strengthens the use of aerosol based exposure options for the appropriate analysis of cigarette smoke induced responses in vitro and may be especially beneficial when comparing aerosols generated from alternative tobacco aerosol products. PMID:26339773

  13. A comparative assessment of cigarette smoke aerosols using an in vitro air–liquid interface cytotoxicity test

    PubMed Central

    Thorne, David; Dalrymple, Annette; Dillon, Deborah; Duke, Martin; Meredith, Clive

    2015-01-01

    Abstract This study describes the evaluation of a modified air-liquid interface BALB/c 3T3 cytotoxicity method for the assessment of smoke aerosols in vitro. The functionality and applicability of this modified protocol was assessed by comparing the cytotoxicity profiles from eight different cigarettes. Three reference cigarettes, 1R5F, 3R4F and CORESTA Monitor 7 were used to put the data into perspective and five bespoke experimental products were manufactured, ensuring a balanced and controlled study. Manufactured cigarettes were matched for key variables such as nicotine delivery, puff number, pressure drop, ventilation, carbon monoxide, nicotine free dry particulate matter and blend, but significantly modified for vapor phase delivery, via the addition of two different types and quantities of adsorptive carbon. Specifically manufacturing products ensures comparisons can be made in a consistent manner and allows the research to ask targeted questions, without confounding product variables. The results demonstrate vapor-phase associated cytotoxic effects and clear differences between the products tested and their cytotoxic profiles. This study has further characterized the in vitro vapor phase biological response relationship and confirmed that the biological response is directly proportional to the amount of available vapor phase toxicants in cigarette smoke, when using a Vitrocell® VC 10 exposure system. This study further supports and strengthens the use of aerosol based exposure options for the appropriate analysis of cigarette smoke induced responses in vitro and may be especially beneficial when comparing aerosols generated from alternative tobacco aerosol products. PMID:26339773

  14. Vapors produced by electronic cigarettes and e-juices with flavorings induce toxicity, oxidative stress, and inflammatory response in lung epithelial cells and in mouse lung.

    PubMed

    Lerner, Chad A; Sundar, Isaac K; Yao, Hongwei; Gerloff, Janice; Ossip, Deborah J; McIntosh, Scott; Robinson, Risa; Rahman, Irfan

    2015-01-01

    Oxidative stress and inflammatory response are the key events in the pathogenesis of chronic airway diseases. The consumption of electronic cigarettes (e-cigs) with a variety of e-liquids/e-juices is alarmingly increasing without the unrealized potential harmful health effects. We hypothesized that electronic nicotine delivery systems (ENDS)/e-cigs pose health concerns due to oxidative toxicity and inflammatory response in lung cells exposed to their aerosols. The aerosols produced by vaporizing ENDS e-liquids exhibit oxidant reactivity suggesting oxidants or reactive oxygen species (OX/ROS) may be inhaled directly into the lung during a "vaping" session. These OX/ROS are generated through activation of the heating element which is affected by heating element status (new versus used), and occurs during the process of e-liquid vaporization. Unvaporized e-liquids were oxidative in a manner dependent on flavor additives, while flavors containing sweet or fruit flavors were stronger oxidizers than tobacco flavors. In light of OX/ROS generated in ENDS e-liquids and aerosols, the effects of ENDS aerosols on tissues and cells of the lung were measured. Exposure of human airway epithelial cells (H292) in an air-liquid interface to ENDS aerosols from a popular device resulted in increased secretion of inflammatory cytokines, such as IL-6 and IL-8. Furthermore, human lung fibroblasts exhibited stress and morphological change in response to treatment with ENDS/e-liquids. These cells also secrete increased IL-8 in response to a cinnamon flavored e-liquid and are susceptible to loss of cell viability by ENDS e-liquids. Finally, exposure of wild type C57BL/6J mice to aerosols produced from a popular e-cig increase pro-inflammatory cytokines and diminished lung glutathione levels which are critical in maintaining cellular redox balance. Thus, exposure to e-cig aerosols/juices incurs measurable oxidative and inflammatory responses in lung cells and tissues that could lead to unrealized health consequences. PMID:25658421

  15. Vapors Produced by Electronic Cigarettes and E-Juices with Flavorings Induce Toxicity, Oxidative Stress, and Inflammatory Response in Lung Epithelial Cells and in Mouse Lung

    PubMed Central

    Lerner, Chad A.; Sundar, Isaac K.; Yao, Hongwei; Gerloff, Janice; Ossip, Deborah J.; McIntosh, Scott; Robinson, Risa; Rahman, Irfan

    2015-01-01

    Oxidative stress and inflammatory response are the key events in the pathogenesis of chronic airway diseases. The consumption of electronic cigarettes (e-cigs) with a variety of e-liquids/e-juices is alarmingly increasing without the unrealized potential harmful health effects. We hypothesized that electronic nicotine delivery systems (ENDS)/e-cigs pose health concerns due to oxidative toxicity and inflammatory response in lung cells exposed to their aerosols. The aerosols produced by vaporizing ENDS e-liquids exhibit oxidant reactivity suggesting oxidants or reactive oxygen species (OX/ROS) may be inhaled directly into the lung during a vaping session. These OX/ROS are generated through activation of the heating element which is affected by heating element status (new versus used), and occurs during the process of e-liquid vaporization. Unvaporized e-liquids were oxidative in a manner dependent on flavor additives, while flavors containing sweet or fruit flavors were stronger oxidizers than tobacco flavors. In light of OX/ROS generated in ENDS e-liquids and aerosols, the effects of ENDS aerosols on tissues and cells of the lung were measured. Exposure of human airway epithelial cells (H292) in an air-liquid interface to ENDS aerosols from a popular device resulted in increased secretion of inflammatory cytokines, such as IL-6 and IL-8. Furthermore, human lung fibroblasts exhibited stress and morphological change in response to treatment with ENDS/e-liquids. These cells also secrete increased IL-8 in response to a cinnamon flavored e-liquid and are susceptible to loss of cell viability by ENDS e-liquids. Finally, exposure of wild type C57BL/6J mice to aerosols produced from a popular e-cig increase pro-inflammatory cytokines and diminished lung glutathione levels which are critical in maintaining cellular redox balance. Thus, exposure to e-cig aerosols/juices incurs measurable oxidative and inflammatory responses in lung cells and tissues that could lead to unrealized health consequences. PMID:25658421

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

    NASA Astrophysics Data System (ADS)

    Caflisch, Robert G.; Walker, James S.

    1983-09-01

    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.

  17. Vapor-Phase Stoichiometry and Heat Treatment of CdTe Starting Material for Physical Vapor Transport

    NASA Technical Reports Server (NTRS)

    Su, Ching-Hua; Sha, Yi-Gao; Lehoczky, S. L.; Liu, Hao-Chieh; Fang, Rei; Brebrick, R. F.

    1998-01-01

    Six batches of CdTe, having total amounts of material from 99 to 203 g and gross mole fraction of Te, X(sub Te), 0.499954-0.500138, were synthesized from pure Cd and Te elements. The vapor-phase stoichiometry of the assynthesized CdTe batches was determined from the partial pressure of Te2, P(sub Te2) using an optical absorption technique. The measured vapor compositions at 870 C were Te-rich for all of the batches with partial pressure ratios of Cd to Te2, P(sub Cd)/P(sub Te2), ranging from 0.00742 to 1.92. After the heat treatment of baking under dynamic vacuum at 870 C for 8 min, the vapor-phase compositions moved toward that of the congruent sublimation, i.e. P(sub Cd)/P(sub Te2) = 2.0, with the measured P(sub Cd)/P(sub Te2) varying from 1.84 to 3.47. The partial pressure measurements on one of the heat-treated samples also showed that the sample remained close to the congruent sublimation condition over the temperature range 800-880 C.

  18. Vapor Phase Transport Synthesis of Zeolites from Sol-Gel Precursors

    SciTech Connect

    THOMA,STEVEN G.; NENOFF,TINA M.

    2000-07-14

    A study of zeolite crystallization from sol-gel precursors using the vapor phase transport synthesis method has been performed. Zeolites (ZSM-5, ZSM-48, Zeolite P, and Sodalite) were crystallized by contacting vapor phase organic or organic-water mixtures with dried sodium silicate and dried sodium alumino-silicate gels. For each precursor gel, a ternary phase system of vapor phase organic reactant molecules was explored. The vapor phase reactant mixtures ranged from pure ethylene diamene, triethylamine, or water, to an equimolar mixture of each. In addition, a series of gels with varied physical and chemical properties were crystallized using the same vapor phase solvent mixture for each gel. The precursor gels and the crystalline products were analyzed via Scanning Electron Microscopy, Electron Dispersive Spectroscopy, X-ray mapping, X-ray powder diffraction, nitrogen surface area, Fourier Transform Infrared Spectroscopy, and thermal analyses. The product phase and purity as a function of the solvent mixture, precursor gel structure, and precursor gel chemistry is discussed.

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

    SciTech Connect

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

    1996-01-09

    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.

  20. Infrared analysis of vapor phase deposited tricresylphosphate (TCP)

    NASA Technical Reports Server (NTRS)

    Morales, Wilfredo; Hanyaloglu, Bengi; Graham, Earl E.

    1994-01-01

    Infrared transmission was employed to study the formation of a lubricating film deposited on two different substrates at 700 C. The deposit was formed from tricresylphosphate vapors and collected onto a NaCl substrate and on an iron coated NaCl substrate. Analysis of the infrared data suggests that a metal phosphate is formed initially, followed by the formation of organophosphorus polymeric compounds.

  1. Concurrent Growth of Kirkendall Pores and Vapor-Solid-Solid Protuberances on Ni Wires During Mo Vapor-Phase Deposition

    NASA Astrophysics Data System (ADS)

    Wang, Cong; Dunand, David C.

    2014-12-01

    During vapor-phase deposition at 1273 K (1000 C), by pack cementation, of Mo onto 127- ?m-diameter Ni wires, two phenomena are observed to occur concurrently, leading to strong surface roughening: (i) the inward radial growth of Kirkendall pores below the wire surface and (ii) the outward growth from the wire surface of protuberances with sizes as large as 15 ?m. High-aspect-ratio Kirkendall pores as long as 21 ?m are created because of imbalanced interdiffusion between Mo and Ni. These pores in turn, by reducing the flow of Mo into the wires, may enhance the outward growth of Mo-rich protuberances, further roughening the wire surface. These protuberances have faceted tips as well as terraces and steps, indicating that their growth is governed by the vapor-solid-solid mechanism.

  2. Concurrent Growth of Kirkendall Pores and Vapor-Solid-Solid Protuberances on Ni Wires During Mo Vapor-Phase Deposition

    NASA Astrophysics Data System (ADS)

    Wang, Cong; Dunand, David C.

    2014-09-01

    During vapor-phase deposition at 1273 K (1000 C), by pack cementation, of Mo onto 127-?m-diameter Ni wires, two phenomena are observed to occur concurrently, leading to strong surface roughening: (i) the inward radial growth of Kirkendall pores below the wire surface and (ii) the outward growth from the wire surface of protuberances with sizes as large as 15 ?m. High-aspect-ratio Kirkendall pores as long as 21 ?m are created because of imbalanced interdiffusion between Mo and Ni. These pores in turn, by reducing the flow of Mo into the wires, may enhance the outward growth of Mo-rich protuberances, further roughening the wire surface. These protuberances have faceted tips as well as terraces and steps, indicating that their growth is governed by the vapor-solid-solid mechanism.

  3. Electronic Cigarette Use by College Students

    PubMed Central

    Sutfin, Erin L.; McCoy, Thomas P.; Morrell, Holly E. R.; Hoeppner, Bettina B.; Wolfson, Mark

    2013-01-01

    Background Electronic cigarettes, or ecigarettes, are battery operated devices that deliver nicotine via inhaled vapor. There is considerable controversy about the disease risk and toxicity of ecigarettes and empirical evidence on short- and long-term health effects is minimal. Limited data on e-cigarette use and correlates exist, and to our knowledge, no prevalence rates among U.S. college students have been reported. This study aimed to estimate the prevalence of ecigarette use and identify correlates of use among a large, multi-institution, random sample of college students. Methods 4,444 students from 8 colleges in North Carolina completed a Webbased survey in fall 2009. Results Ever use of ecigarettes was reported by 4.9% of students, with 1.5% reporting past month use. Correlates of ever use included male gender, Hispanic or Other race (compared to non-Hispanic Whites), Greek affiliation, conventional cigarette smoking and e-cigarette harm perceptions. Although e-cigarette use was more common among conventional cigarette smokers, 12% of ever e-cigarette users had never smoked a conventional cigarette. Among current cigarette smokers, e-cigarette use was negatively associated with lack of knowledge about e-cigarette harm, but was not associated with intentions to quit. Conclusions Although e-cigarette use was more common among conventional cigarette smokers, it was not exclusive to them. E-cigarette use was not associated with intentions to quit smoking among a sub-sample of conventional cigarette smokers. Unlike older, more established cigarette smokers, e-cigarette use by college students does not appear to be motivated by the desire to quit cigarette smoking. PMID:23746429

  4. Vapor-phase self-assembled monolayer for improved mold release in nanoimprint lithography.

    PubMed

    Jung, Gun-Young; Li, Zhiyong; Wu, Wei; Chen, Yong; Olynick, Deirdre L; Wang, Shih-Yuan; Tong, William M; Williams, R Stanley

    2005-02-15

    Resist adhesion to the mold is one of the challenges for nanoimprint lithography. The main approach to overcoming it is to apply a self-assembled monolayer of an organosilane release agent to the mold surface, either in the solution phase or vapor phase. We compared the atomic force microscopy, ellipsometry, reflection-absorption infrared spectroscopy, and contact angle results collected from substrates treated by two different application processes and found that the vapor-phase process was superior. The vapor-treated substrates had fewer aggregates of the silane molecules on the surface, because the lower density of the agent in the vapor phase was not conducive to aggregation formation, and received a superior coating of the releasing agent, because the vapor was more effective than the solution in penetrating into the nanoscale gaps of the mold. A pattern transfer of 20 parallel nanowires with a line width of 40 nm at 100 nm pitch-size was performed faithfully with the vapor-treated mold without any resist adhesion. PMID:15697253

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

    SciTech Connect

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

    1980-05-01

    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.

  6. Phase liquid-vapor equilibria and thermodynamic properties of solutions of n-propanol-aliphatic ketones

    NASA Astrophysics Data System (ADS)

    Suntsov, Yu. K.; Vlasov, M. V.; Chuikov, A. M.

    2015-06-01

    The boiling points of solutions of five binary systems are measured using the ebulliometric method in the pressure range of 4.4-101.3 kPa. Compositions of the equilibrium vapor phases of systems are calculated, based on the constructed pressure isotherms of saturated vapor. The values of excess Gibbs energy and the enthalpy and entropy of solutions are calculated from the data on the liquid-vapor equilibrium. The patterns of change in the phase equilibria and thermodynamic properties of the solutions are established, based on the composition and temperature of the systems. The liquid-vapor equilibrium of systems is described using the equations of Wilson and the NRTL (Non-Random Two-Liquid model).

  7. Vapor phase growth of free-standing palladium nanorods

    NASA Astrophysics Data System (ADS)

    Ma, Dai Liang; Chen, Hsuen Li

    2011-11-01

    Large-area free-standing palladium (Pd) nanorods were grown on sapphire substrate successfully by simply annealing Pd sheet in air at 1 atm. The Pd nanorod density was estimated to be about 110 6 cm -2 and the longest Pd nanorod grown at an angle on sapphire was over a few tens micrometers long. The Pd nanorods were found to grow preferentially along [111] and [110] directions from the transmission electron microscopy study. From the ample results of SEM images coupled with the kinetics data, we observed that Pd particles growth obeyed the classical ripening process during the initial short annealing time, and then followed a vapor-solid (VS) growth mode, leading to the formation of Pd nanorods in the later stage of annealing. The measured activation energy of Pd nanorods growth suggests that the Pd nanorods were formed by the surface diffusion of Pd adatoms coming from the Pd vapor. The use of present simple thermal annealing processes in the growth of free-standing Pd nanorods on large area substrate has potential for the future micro/nano-scale device fabrication.

  8. Oral cavity discrimination of vapor-phase long-chain 18-carbon fatty acids.

    PubMed

    Wajid, Naji A; Halpern, Bruce P

    2012-09-01

    Linoleic, oleic, and stearic fatty acids, presented vapor-phase retronasally, were discriminable from blanks and each other, but the same concentrations, oral-cavity-only (OCO), were not discriminable from blanks. It remained possible that higher concentrations might be discriminable OCO. To evaluate this, participants attempted to discriminate undiluted linoleic, oleic, or stearic acids, vapor-phase OCO, from blanks. For each fatty acid, participants received 5 stimulus delivery containers (SDCs) in 2 trials; 4 SDC held blanks, the fifth, a fatty acid. As a "positive control" in 2 trials, participants received vapor-phase OCO peppermint extract and blanks. For all trials, the task was to select the 1 different SDC. It was found that the 1 different SDC was selected in 24% of stearic, 32% of linoleic, 47% of oleic acid, and in 92% of peppermint trials; discriminations (the 1 different SDC selected in both trials) occurred in 0%, 16%, 26%, and 84% of pairs, respectively. Correct selections for oleic acid differed from chance, P = 0.0004, but not for linoleic acid, P = 0.125, or stearic acid, P = 0.345, Bonferroni corrected. Vapor-phase oleic acid can be an oral cavity trigeminal stimulus, linoleic acid might be (uncorrected P = 0.0384), but vapor-phase stearic acid cannot be. PMID:22459162

  9. Vapor-crystal phase transition in synthesis of paracetamol films by vacuum evaporation and condensation

    NASA Astrophysics Data System (ADS)

    Belyaev, A. P.; Rubets, V. P.; Antipov, V. V.; Bordei, N. S.; Zarembo, V. I.

    2014-03-01

    We report on the structural and technological investigations of the vapor-crystal phase transition during synthesis of paracetamol films of the monoclinic system by vacuum evaporation and condensation in the temperature range 220-320 K. The complex nature of the transformation accompanied by the formation of a gel-like phase is revealed. The results are interpreted using a model according to which the vapor-crystal phase transition is not a simple first-order phase transition, but is a nonlinear superposition of two phase transitions: a first-order transition with a change in density and a second-order phase transition with a change in ordering. Micrographs of the surface of the films are obtained at different phases of formation.

  10. Irritants in cigarette smoke plumes

    SciTech Connect

    Ayer, H.E.; Yeager, D.W.

    1982-11-01

    Concentrations of the irritants formaldehyde and acrolein in side stream cigarette smoke plumes are up to three orders of magnitude above occupational limits, readily accounting for eye and nasal irritation. ''Low-tar'' cigarettes appear at least as irritating as other cigarettes. More than half the irritant is associated with the particulate phase of the smoke, permitting deposition throughout the entire respiratory tract and raising the issue of whether formaldehyde in smoke is associated with bronchial cancer.

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

    SciTech Connect

    Kandoi, Shampa; Greeley, Jeff; Simonetti, Dante; Shabaker, John; Dumesic, James A.; Mavrikakis, Manos

    2010-08-12

    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 CH/OH and CC bonds. Additionally, reaction kinetics studies are carried out for the vapor phase reforming of ethylene glycol (C?H?O?) over Pt/Al?O? 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 CC bond scission in ethylene glycol occurs at an intermediate value of x (3 or 4) in C?HxO?. 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.

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

    SciTech Connect

    Kandoi, S.; Greeley, J.; Simonetti, D.; Shabaker, J.; Dumesic, J. A.; Mavrikakis, M.

    2011-01-01

    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.

  13. Reaction Kinetics of Ethylene Glycol Reforming over Platinum in the Vapor versus Aqueous Phases

    SciTech Connect

    Kandoi, Shampa; Greeley, Jeffrey P.; Simonetti, Dante A.; Shabaker, John; Dumesic, James A.; Mavrikakis, Manos

    2010-08-12

    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 (C2H6O2) over Pt/Al2O3 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 C2HxO2. 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.

  14. Heat and mass transfer in horizontal vapor phase epitaxy reactors

    NASA Astrophysics Data System (ADS)

    Chen, Kuan

    1984-12-01

    Heat and mass transfer processes were studied in a horizontal vapor epitaxy reactor with simultaneously developing velocity, temperature and concentration distributions. The susceptor placed in the reactor was either horizontal or slightly titled. An analytical solution was obtained using previous heat transfer results in entry length and fully developed duct flow, and the heat-mass transfer analogy for growth rate calculations. The mean concentration distributions along the susceptor are presented in dimensionless forms based on constant properties and laminar flow. The influences of axial temperature variation and wall cooling on the epitaxial growth rate distribution are examined in this study. Results of experimental studies of silicon growth from SiH 4 in hydrogen agree well with the analysis.

  15. Crystal growth from the vapor phase. Experiment MA-085

    NASA Technical Reports Server (NTRS)

    Wiedemeier, H.

    1977-01-01

    The positive effects of microgravity on crystal quality and the fundamental properties of the vapor transport reaction were established by analyzing the results of three transport experiments on multicomponent systems performed during the Apollo-Soyuz Test Project mission. The systems employed were GeSe0.99Te0.01-GeI4(A), GeS0.98Se0.02-GeCl4(B), and GeS-GeCl4-Ar (C). The crystallographic analysis is based on a direct comparison of space and ground-based (prototype) crystals employing X-ray diffraction, microprobe, microscopic, and chemical etching techniques. The results demonstrate a considerable improvement of the space-grown crystals in terms of chemical and crystalline homogeneity, surface morphology, and bulk perfection relative to ground specimens.

  16. A Preliminary Study on the Vapor/Mist Phase Lubrication of a Spur Gearbox

    NASA Technical Reports Server (NTRS)

    Morales, Wilfredo; Handschuh, Robert F.

    1999-01-01

    Organophosphates have been the primary compounds used in vapor/mist phase lubrication studies involving ferrous bearing material. Experimental results have indicated that the initial formation of an iron phosphate film on a rubbing ferrous surface, followed by the growth (by cationic diffusion) of a lubricious pyrophosphate-type coating over the iron phosphate, is the reason organophosphates work well as vapor/mist phase lubricants. Recent work, however, has shown that this mechanism leads to the depletion of surface iron atoms and to eventual lubrication failure. A new organophosphate formulation was developed which circumvents surface iron depletion. This formulation was tested by generating an iron phosphate coating on an aluminum surface. The new formulation was then used to vapor/mist phase lubricate a spur gearbox in a preliminary study.

  17. Use of electronic cigarettes (e-cigarettes) impairs indoor air quality and increases FeNO levels of e-cigarette consumers.

    PubMed

    Schober, Wolfgang; Szendrei, Katalin; Matzen, Wolfgang; Osiander-Fuchs, Helga; Heitmann, Dieter; Schettgen, Thomas; Jrres, Rudolf A; Fromme, Hermann

    2014-07-01

    Despite the recent popularity of e-cigarettes, to date only limited data is available on their safety for both users and secondhand smokers. The present study reports a comprehensive inner and outer exposure assessment of e-cigarette emissions in terms of particulate matter (PM), particle number concentrations (PNC), volatile organic compounds (VOC), polycyclic aromatic hydrocarbons (PAH), carbonyls, and metals. In six vaping sessions nine volunteers consumed e-cigarettes with and without nicotine in a thoroughly ventilated room for two hours. We analyzed the levels of e-cigarette pollutants in indoor air and monitored effects on FeNO release and urinary metabolite profile of the subjects. For comparison, the components of the e-cigarette solutions (liquids) were additionally analyzed. During the vaping sessions substantial amounts of 1,2-propanediol, glycerine and nicotine were found in the gas-phase, as well as high concentrations of PM2.5 (mean 197 ?g/m(3)). The concentration of putative carcinogenic PAH in indoor air increased by 20% to 147 ng/m(3), and aluminum showed a 2.4-fold increase. PNC ranged from 48,620 to 88,386 particles/cm(3) (median), with peaks at diameters 24-36 nm. FeNO increased in 7 of 9 individuals. The nicotine content of the liquids varied and was 1.2-fold higher than claimed by the manufacturer. Our data confirm that e-cigarettes are not emission-free and their pollutants could be of health concern for users and secondhand smokers. In particular, ultrafine particles formed from supersaturated 1,2-propanediol vapor can be deposited in the lung, and aerosolized nicotine seems capable of increasing the release of the inflammatory signaling molecule NO upon inhalation. In view of consumer safety, e-cigarettes and nicotine liquids should be officially regulated and labeled with appropriate warnings of potential health effects, particularly of toxicity risk in children. PMID:24373737

  18. MEMS Lubrication by In-Situ Tribochemical Reactions From the Vapor Phase.

    SciTech Connect

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

    2008-01-01

    Vapor Phase Lubrication (VPL) of silicon surfaces with pentanol has been demonstrated. Two potential show stoppers with respect to application of this approach to real MEMS devices have been investigated. Water vapor was found to reduce the effectiveness of VPL with alcohol for a given alcohol concentration, but the basic reaction mechanism observed in water-free environments is still active, and devices operated much longer in mixed alcohol and water vapor environments than with chemisorbed monolayer lubricants alone. Complex MEMS gear trains were successfully lubricated with alcohol vapors, resulting in a factor of 104 improvement in operating life without failure. Complex devices could be made to fail if operated at much higher frequencies than previously used, and there is some evidence that the observed failure is due to accumulation of reaction products at deeply buried interfaces. However, if hypothetical reaction mechanisms involving heated surfaces are valid, then the failures observed at high frequency may not be relevant to operation at normal frequencies. Therefore, this work demonstrates that VPL is a viable approach for complex MEMS devices in conventional packages. Further study of the VPL reaction mechanisms are recommended so that the vapor composition may be optimized for low friction and for different substrate materials with potential application to conventionally fabricated, metal alloy parts in weapons systems. Reaction kinetics should be studied to define effective lubrication regimes as a function of the partial pressure of the vapor phase constituent, interfacial shear rate, substrate composition, and temperature.

  19. Are E-cigarettes a safe and good alternative to cigarette smoking?

    PubMed

    Rom, Oren; Pecorelli, Alessandra; Valacchi, Giuseppe; Reznick, Abraham Z

    2015-03-01

    Electronic cigarettes (E-cigarettes) are devices that can vaporize a nicotine solution combined with liquid flavors instead of burning tobacco leaves. Since their emergence in 2004, E-cigarettes have become widely available, and their use has increased exponentially worldwide. E-cigarettes are aggressively advertised as a smoking cessation aid; as healthier, cheaper, and more socially acceptable than conventional cigarettes. In recent years, these claims have been evaluated in numerous studies. This review explores the development of the current E-cigarette and its market, prevalence of awareness, and use. The review also explores the beneficial and adverse effects of E-cigarettes in various aspects in accordance with recent research. The discussed aspects include smoking cessation or reduction and the health risks, social impact, and environmental consequences of E-cigarettes. PMID:25557889

  20. Effect of dimensionality on vapor-liquid phase transition

    SciTech Connect

    Singh, Sudhir Kumar

    2014-04-24

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

  1. Effect of vapor-phase glutaraldehyde crosslinking on electrospun starch fibers.

    PubMed

    Wang, Wenyu; Jin, Xin; Zhu, Yonghao; Zhu, Chengzhang; Yang, Jian; Wang, Hongjie; Lin, Tong

    2016-04-20

    In this work, we have proven that starch nanofibrous membranes with high tensile strength, water stability and non-cytotoxicity can be produced by electrospinning of starch solution and post-treatment with GTA in vapor phase. GTA vapor phase crosslinking plays a key role in forming water-stable nanofiber membrane and improving the mechanical properties. Comparing with non-crosslinked starch fibers, the crosslinked fibers are increased by nearly 10 times in tensile strength. The crosslinked starch fibrous membranes are non-cytotoxic. They may find applications in the fields of tissue engineering, pharmaceutical therapy and medical. PMID:26876862

  2. A public health strategy for e-cigarettes.

    PubMed

    Schneider, Sven; Diehl, Katharina

    2015-07-01

    The e-cigarette may present a new and significant Public Health problem: Studies published so far do not seem to indicate that e-cigarette use is just a passing trend. If e-cigarette use is less harmless than it is portrayed in many advertisements, Public Health would do well to start a serious discussion about a suitable prevention policy as soon as possible.The aim of this short paper is to discuss a range of measures designed to prevent e-cigarette consumption.Concretely, we suggest to monitor e-cigarette use, the e-cigarette industry and prevention policies, to implement a vapor-free policy, to develop help to quit e-cigarette use, to inform about the health risks of e-cigarette use, to establish regulations on e-cigarette advertising, promotion and sponsorship, and to introduce taxes on e-cigarettes. PMID:26014491

  3. Experimental studies on nucleation, nanoparticle's formation and polymerization from the vapor phase

    NASA Astrophysics Data System (ADS)

    Abdelsayed, Victor Maher

    This research is divided into three major parts. In part I, the critical supersaturations required for the homogeneous nucleation of 2,2,2-trifluorothanol (TFE) vapor have been measured over a temperature range (266-296 K) using an upward thermal diffusion cloud chamber (DCC). The measured supersaturations are in agreement with the predictions of both the classical and the scaled theory of nucleation. Moreover, the condensation of supersaturated TFE vapor on laser-vaporized magnesium nanoparticles has been studied under different experimental conditions, such as the supersaturation, the pressure and the electric field. In part II, the laser vaporization controlled condensation (LVCC) technique was used to prepare Au-Ag alloy nanoparticles in the vapor phase using designed targets of compressed Au and Ag micron-sized powder mixtures of selected composition. The results showed that the optical properties of these nanoparticles could be tuned depending on the alloy composition and the laser wavelength. Different intermetallic nanoparticles (FeAl and NiAl) from the vapor phase has also been prepared, using the same approach. In this work, the fraction of the charged particles generated during the laser vaporization process was used to prepare a new class of nanoparticle assemblies in the LVCC chamber under the influence of an electric field. The results showed that the electric field required to induce the formation of these nanoassemblies is material and field dependent. By coupling the LVCC chamber with the differential mobility analyzer, size-selected nanoparticles have been prepared in the vapor phase. The prepared nanoparticles were characterized by different techniques such as scanning electron microscopy (SEM), X-ray diffraction (XRD), transmission electron microscopy (TEM) and UV-visible spectroscopy. In part III, new methods were developed to prepare nanoparticle-polymer composites from the vapor phase. In the first method, the LVCC method was used to prepare a carbonaceous cross-linked resin, with different nanoparticles (Ni, Pt and FeAl) embedded inside. In the second method, free radical-thermally initiated polymerization was used to polymerize a monomer vapor of styrene on the surfaces of activated Ni nanoparticles.

  4. Electronic cigarettes. Potential harms and benefits.

    PubMed

    Drummond, M Bradley; Upson, Dona

    2014-02-01

    Use of electronic cigarettes, devices that deliver a nicotine-containing vapor, has increased rapidly across the country and globally. Perceived and marketed as a "healthier alternative" to conventional cigarettes, few data exist regarding the safety of these devices and their efficacy in harm reduction and treatment of tobacco dependence; even less is known about their overall impact on population health. This review highlights the recent data regarding electronic cigarette toxicity, impact on lung function, and efficacy in smoking reduction and cessation. Studies show that the vapor generated from electronic cigarettes has variable amounts of nicotine and potential harmful toxins, albeit at levels lower than in conventional cigarettes. The long-term carcinogenic and lung function effects of electronic cigarettes are not known. Although some data demonstrate that electronic cigarettes may be effective in reducing conventional cigarette consumption, there are no data demonstrating the efficacy of electronic cigarettes as a tool to achieve cessation. Until robust longitudinal evaluations demonstrate the safety of electronic cigarettes and efficacy in treatment of tobacco dependence, their role as a harm reduction tool is unclear. PMID:24575993

  5. Liquid-phase dispersion during injection into vapor-dominated reservoirs

    SciTech Connect

    Pruess, K.

    1994-01-01

    The behavior of water injection plumes in vapor-dominated reservoirs is examined. Stressing the similarity to water infiltration in heterogeneous soils, we suggest that ever-present heterogeneities in individual fractures and fracture networks will cause a lateral broadening of descending injection plumes. The process of lateral spreading of liquid phase is viewed in analogy to transverse dispersion in miscible displacement. To account for the postulated ``phase dispersion`` the conventional two-phase immiscible flow theory is extended by adding a Fickian-type dispersive term. The validity of the proposed phase dispersion model is explored by means of simulations with detailed resolution of small-scale heterogeneity. We also present an illustrative application to injection into a depleted vapor zone. It is concluded that phase dispersion effects will broaden descending injection plumes, with important consequences for pressure support and potential water breakthrough at neighboring production wells.

  6. Liquid-phase dispersion during injection into vapor-dominated reservoirs

    SciTech Connect

    Pruess, Karsten

    1994-01-20

    The behavior of water injection plumes in vapor-dominated reservoirs is examined. Stressing the similarity to water infiltration in heterogeneous soils, we suggest that everpresent heterogeneities in individual fractures and fracture networks will cause a lateral broadening of descending injection plumes. The process of lateral spreading of liquid phase is viewed in analogy to transverse dispersion in miscible displacement. To account for the postulated phase dispersion the conventional two-phase immiscible flow theory is extended by adding a Fickian-type dispersive term. The validity of the proposed phase dispersion model is explored by means of simulations with detailed resolution of small-scale heterogeneity. We also present an illustrative application to injection into a depleted vapor zone. It is concluded that phase dispersion effects will broaden descending injection plumes, with important consequences for pressure support and potential water breakthrough at neighboring production wells.

  7. Condensed phase conversion and growth of nanorods and other materials instead of from vapor

    DOEpatents

    Geohegan, David B. (Knoxville, TN); Seals, Roland D. (Oak Ridge, TN); Puretzky, Alex A. (Knoxville, TN); Fan, Xudong (Oak Ridge, TN)

    2010-10-19

    Compositions, systems and methods are described for condensed phase conversion and growth of nanorods and other materials. A method includes providing a condensed phase matrix material; and activating the condensed phase matrix material to produce a plurality of nanorods by condensed phase conversion and growth from the condensed phase matrix material instead of from vapor. The compositions are very strong. The compositions and methods provide advantages because they allow (1) formation rates of nanostructures necessary for reasonable production rates, and (2) the near net shaped production of component structures.

  8. Comparison of environmental tobacco smoke (ETS) concentrations generated by an electrically heated cigarette smoking system and a conventional cigarette.

    PubMed

    Tricker, Anthony R; Schorp, Matthias K; Urban, Hans-Jrg; Leyden, Donald; Hagedorn, Heinz-Werner; Engl, Johannes; Urban, Michael; Riedel, Kirsten; Gilch, Gerhard; Janket, Dinamis; Scherer, Gerhard

    2009-01-01

    Smoking conventional lit-end cigarettes results in exposure of nonsmokers to potentially harmful cigarette smoke constituents present in environmental tobacco smoke (ETS) generated by sidestream smoke emissions and exhaled mainstream smoke. ETS constituent concentrations generated by a conventional lit-end cigarette and a newly developed electrically heated cigarette smoking system (EHCSS) that produces only mainstream smoke and no sidestream smoke emissions were investigated in simulated "office" and "hospitality" environments with different levels of baseline indoor air quality. Smoking the EHCSS (International Organisation for Standardization yields: 5 mg tar, 0.3 mg nicotine, and 0.6 mg carbon monoxide) in simulated indoor environments resulted in significant reductions in ETS constituent concentrations compared to when smoking a representative lit-end cigarette (Marlboro: 6 mg tar, 0.5 mg nicotine, and 7 mg carbon monoxide). In direct comparisons, 24 of 29 measured smoke constituents (83%) showed mean reductions of greater than 90%, and 5 smoke constituents (17%) showed mean reductions between 80% and 90%. Gas-vapor phase ETS markers (nicotine and 3-ethenylpyridine) were reduced by an average of 97% (range 94-99%). Total respirable suspended particles, determined by online particle measurements and as gravimetric respirable suspended particles, were reduced by 90% (range 82-100%). The mean and standard deviation of the reduction of all constituents was 94 +/- 4%, indicating that smoking the new EHCSS in simulated "office" and "hospitality" indoor environments resulted in substantial reductions of ETS constituents in indoor air. PMID:18951229

  9. Influence of solid-state characteristics on critical parameters of vapor-liquid phase transition

    NASA Astrophysics Data System (ADS)

    Khomkin, A. L.; Shumikhin, A. S.

    2015-11-01

    New method for calculation of critical point parameters and binodal of vapor-liquid (dielectric-metal) phase transition is suggested. Method is based on the hypothesis that cohesion, which determines the main properties of solid state, determines also the properties in vicinity of critical point. Comparison with known experimental data for rare gases and mercury shows satisfactory agreement with our calculations.

  10. VAPOR PHASE MERCURY SORPTION BY ORGANIC-SULFIDE COATED BIMETALLIC IRON-COPPER NANOPARTICLE AGGREGATES

    EPA Science Inventory

    Tetra sulfide silane coated iron-copper nano-particle aggregates are found to be potentially very high capacity sorbents for vapor phase mercury capture. High equilibrium capacities were obtained for the silane coated iron copper nano-aggregate sorbent at 70 oC and 120 oC. Even a...

  11. 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...

  12. EFFECT OF VAPOR-PHASE BIOREACTOR OPERATION ON BIOMASS ACCUMULATION, DISTRIBUTION, AND ACTIVITY. (R826168)

    EPA Science Inventory

    Excess biomass accumulation and activity loss in vapor-phase bioreactors (VPBs) can lead to unreliable long-term operation. In this study, temporal and spatial variations in biomass accumulation, distribution and activity in VPBs treating toluene-contaminated air were monitored o...

  13. 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. ...

  14. ORGANIC CHARACTERIZATION OF AEROSOLS AND VAPOR PHASE COMPOUNDS IN URBAN ATMOSPHERES

    EPA Science Inventory

    Organic pollutants in urban atmospheres were characterized by analyzing particulate and/or vapor-phase samples collected by EPA in St. Louis, Missouri; Miami, Florida; Denver, Colorado; Houston, Texas; and at the General Motors Test Track in Milford, Michigan. The particulate sam...

  15. Inhibition effects of vapor phase thymol and modified atmosphere against Salmonella spp. on raw shrimp

    Technology Transfer Automated Retrieval System (TEKTRAN)

    Salmonella contamination of shrimp is a food safety concern in the U.S. and other countries. Natural antimicrobial compounds (e.g. essential oils) in vapor phase and modified atmosphere (MA) technology can inhibit the growth potential of Salmonella spp. However, each strategy has its limitations, wh...

  16. Vapor phase growth of group 3, 4, and 5 compounds by HCl transport of elements

    NASA Technical Reports Server (NTRS)

    Tyagi, R. C.; Debnam, W. J., Jr.; Mcnear, M. F.; Crouch, R. K.; Breckenridge, R. A.

    1973-01-01

    Technique has been devised for vapor-phase epitaxial growth of group 3, 4, and 5 binary, ternary, or quaternary compounds by HCl transport of the constituent elements or dopants. Technique uses all the constituents of the alloy system in their elemental form. Transport of these elements by an HCl + H2 carrier gas facilitates their transport as subchlorides.

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

    NASA Astrophysics Data System (ADS)

    Kjellstrom, Ann H.; Sarholm, Lena M.

    2000-08-01

    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.

  18. A technique for eliminating white phosphorus deposits in vapor phase epitaxy systems

    NASA Technical Reports Server (NTRS)

    Wilt, D. M.; Hoffman, R. W.

    1993-01-01

    A technique of heating the exhaust lines is described whereby phosphorus in the exhaust portion of an organometallic vapor phase epitaxy reactor is encouraged to deposit in the red form rather than the pyrophoric white form. This technique is simple, effective, and does not hinder or limit the conditions under which the reactor may be operated.

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

    PubMed

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

    2002-10-01

    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

  20. Identification of stable cytotoxic factors in the gas phase extract of cigarette smoke and pharmacological characterization of their cytotoxicity.

    PubMed

    Noya, Yoichi; Seki, Koh-Ichi; Asano, Hiroshi; Mai, Yosuke; Horinouchi, Takahiro; Higashi, Tsunehito; Terada, Koji; Hatate, Chizuru; Hoshi, Akimasa; Nepal, Prabha; Horiguchi, Mika; Kuge, Yuji; Miwa, Soichi

    2013-12-01

    Smoking is a major risk factor for atherosclerotic vascular diseases, but the mechanism for its genesis is unknown. We have recently shown that the gas phase of cigarette smoke (nicotine- and tar-free cigarette smoke extract; CSE) likely to reach the systemic circulation contains stable substances which cause cytotoxicity like plasma membrane damage and cell death in cultured cells, and also that the plasma membrane damage is caused through sequential activation of protein kinase C (PKC) and NADPH oxidase (NOX) and the resulting generation of reactive oxygen species (PKC/NOX-dependent mechanism), whereas cell death is caused through PKC/NOX-dependent and -independent mechanisms. To identify these stable substances, the CSE was prepared by passing the main-stream smoke of 10 cigarettes through a Cambridge glass fiber filter, trapping of the smoke in a vessel cooled at -80C, and subsequent dissolution in 10ml of water. The CSE was fractionated into nine fractions using reversed-phase HPLC, and each fraction was screened for cytotoxicity in cultured cells, using propidium iodide uptake assay for cell membrane damage and MTS [3-(4,5-dimethylthiazol-2-yl)-5-(3-carboxymethoxyphenyl)-2-(4-sulfophenyl)-2H-tetrazolium] reduction assay for cell viability. The cytotoxicity was positive in two of the nine fractions (Fr2 and Fr5). After extraction of the active fractions into dichloromethane, GC/MS analysis identified 2-cyclopenten-1-one (CPO) in Fr5 but none in Fr2. After derivatization of the active fractions with O-(2,3,4,5,6-pentafluorobenzyl) hydroxylamine hydrochloride, GC/MS analysis identified acrolein, acetone and propionaldehyde in Fr2, and methyl vinyl ketone (MVK) in Fr5. After 4-h incubation, authentic acrolein and MVK induced concentration-dependent cytotoxicity with EC50 values of 75.98.2 and 47.08.0?M (meanSEM; n=3), respectively, whereas acetone, propionaldehyde and CPO were without effect. However, after 24-h incubation, CPO induced concentration-dependent cytotoxicity with an EC50 value of 264.016.9?M (n=3). The concentrations of acrolein, MVK and CPO in the CSE were 3368334, 2429123 and 392.931.8?M (n=4), respectively, which were higher than the cytotoxic concentrations. The cytotoxicity of acrolein and MVK consisted of plasma membrane damage and decreased cell viability: the plasma membrane damage was totally prevented by treatment with an inhibitor of PKC or NOX, whereas the decreased cell viability was only partially prevented by these inhibitors. The cytotoxicity of CPO consisted only of decreased cell viability, which was totally resistant to these inhibitors. These results show that acrolein and MVK are responsible for the acute cytotoxicity of the CSE through PKC/NOX-dependent and -independent mechanisms, whereas CPO is responsible for the delayed cytotoxicity of the CSE through a PKC/NOX-independent mechanism. PMID:23981515

  1. Plasma Spray-PVD: A New Thermal Spray Process to Deposit Out of the Vapor Phase

    NASA Astrophysics Data System (ADS)

    von Niessen, Konstantin; Gindrat, Malko

    2011-06-01

    Plasma spray-physical vapor deposition (PS-PVD) is a low pressure plasma spray technology recently developed by Sulzer Metco AG (Switzerland). Even though it is a thermal spray process, it can deposit coatings out of the vapor phase. The basis of PS-PVD is the low pressure plasma spraying (LPPS) technology that has been well established in industry for several years. In comparison to conventional vacuum plasma spraying (VPS) or low pressure plasma spraying (LPPS), the new proposed process uses a high energy plasma gun operated at a reduced work pressure of 0.1 kPa (1 mbar). Owing to the high energy plasma and further reduced work pressure, PS-PVD is able to deposit a coating not only by melting the feed stock material which builds up a layer from liquid splats but also by vaporizing the injected material. Therefore, the PS-PVD process fills the gap between the conventional physical vapor deposition (PVD) technologies and standard thermal spray processes. The possibility to vaporize feedstock material and to produce layers out of the vapor phase results in new and unique coating microstructures. The properties of such coatings are superior to those of thermal spray and electron beam-physical vapor deposition (EB-PVD) coatings. In contrast to EB-PVD, PS-PVD incorporates the vaporized coating material into a supersonic plasma plume. Owing to the forced gas stream of the plasma jet, complex shaped parts such as multi-airfoil turbine vanes can be coated with columnar thermal barrier coatings using PS-PVD. Even shadowed areas and areas which are not in the line of sight of the coating source can be coated homogeneously. This article reports on the progress made by Sulzer Metco in developing a thermal spray process to produce coatings out of the vapor phase. Columnar thermal barrier coatings made of Yttria-stabilized Zircona (YSZ) are optimized to serve in a turbine engine. This process includes not only preferable coating properties such as strain tolerance and erosion resistance but also the simultaneous coverage of multiple air foils.

  2. Six-phase soil heating for enhanced removal of contaminants during soil vapor extraction

    SciTech Connect

    Gauglitz, P.A.; Roberts, J.S.; Bergsman, T.M.

    1995-12-31

    Six-phase soil heating (SPSH) is a technique that uses low-frequency electricity to resistively heat soils as an enhancement to soil vapor extraction. This paper details a demonstration of SPSH at the US Department of Energy Savannah River Site. The method removed 99.7% (median) of perchloroethylene from the clay zone within the electrode array and accelerated the removal of volatile organic compounds as compared to vapor extraction alone. The implementation of SPSH to treat soil at the Rocky Flats plant is also summarized.

  3. Menthol Cigarettes

    MedlinePLUS

    ... Use Supplement to the Current Population Survey (TUS-CPS) 2006/07. 2008, National Cancer Institute and Centers ... 07): http://cancercontrol.cancer.gov/brp/tcrb/tus-cps/ . U.S. Department of Commerce Census Bureau, Menthol Cigarette ...

  4. Liquid-phase and vapor-phase dehydration of organic/water solutions

    DOEpatents

    Huang, Yu; Ly, Jennifer; Aldajani, Tiem; Baker, Richard W.

    2011-08-23

    Processes for dehydrating an organic/water solution by pervaporation or vapor separation using fluorinated membranes. The processes are particularly useful for treating mixtures containing light organic components, such as ethanol, isopropanol or acetic acid.

  5. New low toxicity, multi-metal active vapor phase corrosion inhibitors

    SciTech Connect

    Cole, D.E.; Dixon, B.G.; Koehan, F.L.

    1999-07-01

    Traditional vapor phase corrosion inhibitors (VCIs) were developed for short-term protection of steel articles. VCIs have been applied for protecting metallic structures between stages of manufacturing, between manufacturing and deployment, and in enclosed service environments. Some of the problems associated with this corrosion inhibiting application include: protecting dissimilar metallic structures, avoiding toxic materials such as nitrite salts and formaldehyde emitting compounds, an the need for longer duration corrosion protection. Several types of organic compounds were derivatized for temporary volatility and formulated to yield materials with sufficient ambient temperature vapor pressure for VCI application. The ability of these new VCIs to prevent vapor phase metallic corrosion was investigated by an accelerated hydrothermal exposure method. Metals investigated included an aluminum aircraft alloy, cold rolled steel, brass and a copper-nickel alloy. Potentiodynamic slow scan electrochemical analysis and SEM were also used to study the surface behavior and corrosion processes for metallic specimens treated with experimental and control VCIS. Several of the new compounds showed significant vapor phase corrosion inhibition on all four metal alloys.

  6. Resonant Acoustic Measurement of Vapor Phase Transport Phenomenon

    NASA Astrophysics Data System (ADS)

    Schuhmann, R. J.; Garrett, S. L.; Matson, J. V.

    2002-12-01

    A major impediment to accurate non steady-state diffusion measurements is the ability to accurately measure and track a rapidly changing gas concentration without disturbing the system. Non-destructive methods that do not interfere with system dynamics have been developed in the past. These methods, however, have tended to be cumbersome or inaccurate at low concentrations. A new experimental approach has been developed to measure gaseous diffusion in free air and through porous materials. The method combines the traditional non steady-state laboratory methodology with resonant acoustic gas analysis. A phase-locked-loop (PLL) resonance frequency tracker is combined with a thermally insulated copper resonator. A piston sealed with a metal bellows excites the fundamental standing wave resonance of the resonator. The PLL maintains a constant phase difference (typically 90) between the accelerometer mounted on the piston and a microphone near the piston to track the resonance frequency in real time. A capillary or glass bead filled core is fitted into an o-ring sealed opening at the end of the resonator opposite the bellows. The rate at which the tracer gas is replaced by air within the resonator is controlled by the diffusion coefficient of the gas in free air through the capillary (DA) or by the effective diffusion coefficient of the gas through the core (De). The mean molecular weight of the gas mixture in the resonator is directly determined six times each minute from the ratio of the absolute temperature to the square of the fundamental acoustic resonance frequency. Average system stability (temperature divided by frequency squared) is better than 350 ppm. DA values for a 0.3-inch diameter capillary were in excellent agreement with published values. De values for porous media samples (0.5 mm glass beads) of four different lengths (1 through 4 inches) using three different tracer gases (He, CH4, Kr) will be reported. Comments will be offered regarding tracer gas selection and device orientation and their effect on experimental results. [Work supported by the Office of Naval Research.

  7. Novel Process for Removal and Recovery of Vapor Phase Mercury

    SciTech Connect

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

    1998-03-09

    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.

  8. Phase-transition thresholds and vaporization phenomena for ultrasound phase-change nanoemulsions assessed via high speed optical microscopy

    PubMed Central

    Sheeran, Paul S.; Matsunaga, Terry O.; Dayton, Paul A.

    2015-01-01

    Ultrasonically activated phase-change contrast agents (PCCAs) based on perfluorocarbon droplets have been proposed for a variety of therapeutic and diagnostic clinical applications. When generated at the nanoscale, droplets may be small enough to exit the vascular space and then be induced to vaporize with high spatial and temporal specificity by externally-applied ultrasound. The use of acoustical techniques for optimizing ultrasound parameters for given applications can be a significant challenge for nanoscale PCCAs due to the contributions of larger outlier droplets. Similarly, optical techniques can be a challenge due to the sub-micron size of nanodroplet agents and resolution limits of optical microscopy. In this study, an optical method for determining activation thresholds of nanoscale emulsions based on the in vitro distribution of bubbles resulting from vaporization of PCCAs after single, short (<10 cycles) ultrasound pulses is evaluated. Through ultra-high-speed microscopy it is shown that the bubbles produced early in the pulse from vaporized droplets are strongly affected by subsequent cycles of the vaporization pulse, and these effects increase with pulse length. Results show that decafluorobutane nanoemulsions with peak diameters on the order of 200 nm can be optimally vaporized with short pulses using pressures amenable to clinical diagnostic ultrasound machines. PMID:23760161

  9. Phase-transition thresholds and vaporization phenomena for ultrasound phase-change nanoemulsions assessed via high-speed optical microscopy

    NASA Astrophysics Data System (ADS)

    Sheeran, Paul S.; Matsunaga, Terry O.; Dayton, Paul A.

    2013-07-01

    Ultrasonically activated phase-change contrast agents (PCCAs) based on perfluorocarbon droplets have been proposed for a variety of therapeutic and diagnostic clinical applications. When generated at the nanoscale, droplets may be small enough to exit the vascular space and then be induced to vaporize with high spatial and temporal specificity by externally-applied ultrasound. The use of acoustical techniques for optimizing ultrasound parameters for given applications can be a significant challenge for nanoscale PCCAs due to the contributions of larger outlier droplets. Similarly, optical techniques can be a challenge due to the sub-micron size of nanodroplet agents and resolution limits of optical microscopy. In this study, an optical method for determining activation thresholds of nanoscale emulsions based on the in vitro distribution of bubbles resulting from vaporization of PCCAs after single, short (<10 cycles) ultrasound pulses is evaluated. Through ultra-high-speed microscopy it is shown that the bubbles produced early in the pulse from vaporized droplets are strongly affected by subsequent cycles of the vaporization pulse, and these effects increase with pulse length. Results show that decafluorobutane nanoemulsions with peak diameters on the order of 200 nm can be optimally vaporized with short pulses using pressures amenable to clinical diagnostic ultrasound machines.

  10. An intercomparison of measurement systems for vapor and particulate phase concentrations of formic and acetic acids

    NASA Technical Reports Server (NTRS)

    Keene, William C.; Talbot, Robert W.; Andreae, Meinrat O.; Beecher, Kristene; Berresheim, Harold

    1989-01-01

    During June 1986, eight systems for measuring vapor phase and four for measuring particulate phase concentrations of formic acid (HCOOH) and acetic acid (CH3COOH) were intercompared in central Virginia. HCOOH and CH3COOH vapors were sampled by condensate, mist, Chromosorb 103 GC resin, NaOH-coated annular denuders, NaOH-impregnated quartz filters, K2CO3 and NaCO3-impregnated cellulose filters, and Nylasorb membranes. Atmospheric aerosol was collected on Teflon and Nuclepore filters using both hi-vol and lo-vol systems to measure particulate phase concentrations. Performances of the mist chamber and K2CO3-impregnated filter techniques were evaluated using zero air and ambient air spiked with HCOOH(g) and CH3COOH(g), and formaldehyde from permeation sources. The advantages and drawbacks of these methods are reported and discussed.

  11. Assessment of the Vapor Phase Catalytic Ammonia Removal (VPCAR) Technology at the MSFC ECLS Test Facility

    NASA Technical Reports Server (NTRS)

    Tomes, Kristin; Long, David; Carter, Layne; Flynn, Michael

    2007-01-01

    The Vapor Phase Catalytic Ammonia. Removal (VPCAR) technology has been previously discussed as a viable option for. the Exploration Water Recovery System. This technology integrates a phase change process with catalytic oxidation in the vapor phase to produce potable water from exploration mission wastewaters. A developmental prototype VPCAR was designed, built and tested under funding provided by a National Research. Announcement (NRA) project. The core technology, a Wiped Film Rotating Device (WFRD) was provided by Water Reuse Technologies under the NRA, whereas Hamilton Sundstrand Space Systems International performed the hardware integration and acceptance test. of the system. Personnel at the-Ames Research Center performed initial systems test of the VPCAR using ersatz solutions. To assess the viability of this hardware for Exploration. Life Support (ELS) applications, the hardware has been modified and tested at the MSFC ECLS Test facility. This paper summarizes the hardware modifications and test results and provides an assessment of this technology for the ELS application.

  12. Thermal Lattice Boltzmann Simulations for Vapor-Liquid Two-Phase Flows in Two Dimensions

    NASA Astrophysics Data System (ADS)

    Wei, Yikun; Qian, Yuehong

    2011-11-01

    A lattice Boltzmann model with double distribution functions is developed to simulate thermal vapor-liquid two-phase flows. In this model, the so-called mesoscopic inter-particle pseudo-potential for the single component multi-phase lattice Boltzmann model is used to simulate the fluid dynamics and the internal energy field is simulated by using a energy distribution function. Theoretical results for large-scale dynamics including the internal energy equation can be derived and numerical results for the coexistence curve of vapor-liquid systems are in good agreement with the theoretical predictions. It is shown from numerical simulations that the model has the ability to mimic phase transitions, bubbly flows and slugging flows. This research is support in part by the grant of Education Ministry of China IRT0844 and the grant of Shanghai CST 11XD1402300.

  13. An intercomparison of measurement systems for vapor and particulate phase concentrations of formic and acetic acids

    NASA Astrophysics Data System (ADS)

    Keene, William C.; Talbot, Robert W.; Andreae, Meinrat O.; Beecher, Kristene; Berresheim, Harold

    1989-05-01

    During June 1986, eight systems for measuring vapor phase and four for measuring particulate phase concentrations of formic acid (HCOOH) and acetic acid (CH3COOH) were intercompared in central Virginia. HCOOH and CH3COOH vapors were sampled by condensate, mist, Chromosorb 103 GC resin, NaOH-coated annular denuders, NaOH-impregnated quartz filters, K2CO3 and NaCO3-impregnated cellulose filters, and Nylasorb membranes. Atmospheric aerosol was collected on Teflon and Nuclepore filters using both hi-vol and lo-vol systems to measure particulate phase concentrations. Performances of the mist chamber and K2CO3-impregnated filter techniques were evaluated using zero air and ambient air spiked with HCOOH(g) and CH3COOH(g), and formaldehyde from permeation sources. The advantages and drawbacks of these methods are reported and discussed.

  14. Determination of toxic carbonyl compounds in cigarette smoke.

    PubMed

    Fujioka, Kazutoshi; Shibamoto, Takayuki

    2006-02-01

    Toxic carbonyl compounds, including formaldehyde, malonaldehyde, and glyoxal, formed in mainstream cigarette smoke were quantified by derivatization-solid phase extraction-gas chromatography methods. Cigarette smoke from 14 commercial brands and one reference (2R1F) was drawn into a separatory funnel containing aqueous phosphate-buffered saline. Reactive carbonyl compounds trapped in the buffer solution were derivatized into stable nitrogen containing compounds (pyrazoles for beta-dicarbonyl and alpha,beta-unsaturated aldehyde; quinoxalines for alpha-dicarbonyls; and thiazolidines for alkanals). After derivatives were recovered using C(18) solid phase extraction cartridges, they were analyzed quantitatively by a gas chromatograph with a nitrogen phosphorus detector. The total carbonyl compounds recovered from regular size cigarettes ranged from 1.92 mg/cigarette(-1) to 3.14 mg/cigarette(-1). The total carbonyl compounds recovered from a reference cigarette and a king size cigarette were 3.23 mg/cigarette(-1) and 3.39 mg/cigarette(-1), respectively. The general decreasing order of the carbonyl compounds yielded was acetaldehyde (1110-2101 microg/cigarette(-1)) > diacetyl (301-433 microg/cigarette(-1)), acrolein (238-468 microg/cigarette(-1)) > formaldehyde (87.0-243 microg/cigarette(-1)), propanal (87.0-176 microg/cigarette(-1)) > malonaldehyde (18.9-36.0 microg/cigarette(-1)), methylglyoxal (13.4-59.6 microg/cigarette(-1)) > glyoxal (1.93-6.98 microg/cigarette(-1)). PMID:16463255

  15. [E-Cigarettes Friend or Foe?].

    PubMed

    Russi, Erich W

    2015-07-01

    Not nicotine, but an abundant amount of toxic chemicals produced by the combustion of tobacco are the cause of well-known health problems. E-cigarette vapor contains no or only minimal quantities of potentially harmful substances. Hence it can be assumed that vaping in adults is much less harmful than smoking of cigarettes. Furthermore, no data exist that e-cigarettes will encourage youngsters to become cigarette smokers. E-cigarette vaping has the potential to reduce the daily number of cigarettes smoked or facilitates cessation of smoking in heavily nicotine-dependent smokers, who keep on smoking despite a structured smoking cessation program. Health professionals should be aware of this type of nicotine substitution, since the controversial discussion is often emotional and not evidence-based. PMID:26135724

  16. Molecular dynamics simulation of liquid-vapor phase equilibria in polar fluids

    NASA Astrophysics Data System (ADS)

    Eslami, Hossein; Dargahi, Ali; Behnejad, Hassan

    2009-04-01

    A new molecular dynamics simulation technique in the grand canonical ensemble [H. Eslami, F. Mller-Plathe, J. Comput. Chem. 28 (2007) 1763], has been employed to calculate the chemical potentials in the coexisting liquid and vapor phases of pure water, methanol, and acetonitrile. Calculating the chemical potentials in the liquid phase, a new method [J. Vrabec, H. Hasse, Mol. Phys. 100 (2002) 3375], has been employed to calculate the phase coexistence point. In this method just two independent simulations in the grand canonical ensemble are needed to be performed and the molecules are inserted into or deleted from the system in a dynamical way.

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

    NASA Astrophysics Data System (ADS)

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

    2013-03-01

    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.

  18. Vapor-phase molecular doping of graphene for high-performance transparent electrodes.

    PubMed

    Kim, Youngsoo; Ryu, Jaechul; Park, Myungjin; Kim, Eun Sun; Yoo, Je Min; Park, Jaesung; Kang, Jin Hyoun; Hong, Byung Hee

    2014-01-28

    Doping is an essential process to engineer the conductivity and work-function of graphene for higher performance optoelectronic devices, which includes substitutional atomic doping by reactive gases, electrical/electrochemical doping by gate bias, and chemical doping by acids or reducing/oxidizing agents. Among these, the chemical doping has been widely used due to its simple process and high doping strength. However, it also has an instability problem in that the molecular dopants tend to gradually evaporate from the surface of graphene, leading to substantial decrease in doping effect with time. In particular, the instability problem is more serious for n-doped graphene because of undesirable reaction between dopants and oxygen or water in air. Here we report a simple method to tune the electrical properties of CVD graphene through n-doping by vaporized molecules at 70 C, where the dopants in vapor phase are mildly adsorbed on graphene surface without direct contact with solution. To investigate the dependence on functional groups and molecular weights, we selected a series of ethylene amines as a model system, including ethylene diamine (EDA), diethylene triamine (DETA), and triethylene tetramine (TETA) with increasing number of amine groups showing different vapor pressures. We confirmed that the vapor-phase doping provides not only very high carrier concentration but also good long-term stability in air, which is particularly important for practical applications. PMID:24313602

  19. Comparison between Normal and HeII Two-phase Flows at High Vapor Velocities

    NASA Astrophysics Data System (ADS)

    Perraud, S.; Rousset, B.; Thibault, P.; van Weelderen, R.; Wolf, P. E.

    2006-04-01

    We present results on helium co-current two-phase flow experiments at high vapor velocity obtained with the use of the new CEA/SBT 400 W/1.8 K refrigerator. For vapor velocities larger than typically 4 m/s, a mist of droplets develops from the bulk liquid interface accompanied by an increase in heat transfer at the wall. Experiments were conducted in a 10 m long, 40 mm I.D. straight pipe, both in helium II and in helium I to compare these two situations. The respective roles of vapor density, vapor velocity and liquid level on atomization were systematically investigated. Light scattering experiments were performed to measure sizes, velocities and interfacial areas of droplets in a complete cross section. In-house-made heat transfer sensors located in the mist allowed us to deduce an upper value of the extra cooling power of the dispersed phase. The practical interest of atomized flow for cooling large cryogenic facilities is discussed by considering the balance between increase in heat transfer and pressure drops it induces.

  20. Dramatic vapor-phase modulation of the characteristics of graphene field-effect transistors.

    PubMed

    Worley, Barrett C; Kim, Seohee; Park, Saungeun; Rossky, Peter J; Akinwande, Deji; Dodabalapur, Ananth

    2015-07-28

    Here we report on dramatic and favorable changes to the operating characteristics in monolayer graphene field-effect transistors (FETs) exposed to vapor-phase, polar organic molecules in ambient. These changes include significant reduction of the Dirac voltage, accompanied by both an increase in electron and hole mobility, ?, and a decrease in residual carrier density, N0, to < 3 10(11) cm(-2). In contrast to graphene FET modulation with various liquid- and solid-phase dielectric media present in the literature, we attribute these changes to screening by polar vapor-phase molecules of fields induced by charged impurities and defects, n(imp), in or near the active layer. The magnitude of the changes produced in the graphene FET parameters scales remarkably well with the dipole moment of the delivered molecules. These effects are reversible, a unique advantage of working in the vapor phase. The changes observed upon polar molecule delivery are analogous to those produced by depositing and annealing fluoropolymer coatings on graphene that have been reported previously, and we attribute these changes to similar charge screening or neutralization phenomena. PMID:26107384

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

    USGS Publications Warehouse

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

    1978-01-01

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

  2. DrugFacts: Electronic Cigarettes (e-Cigarettes)

    MedlinePLUS

    ... Home » Publications » DrugFacts » Electronic Cigarettes (e-Cigarettes) DrugFacts: Electronic Cigarettes (e-Cigarettes) Email Facebook Twitter Revised August 2015 Electronic cigarettes (also called e-cigarettes or electronic nicotine ...

  3. In situ, subsurface monitoring of vapor-phase TCE using fiber optics

    SciTech Connect

    Rossabi, J.; Colston, B. Jr.; Brown, S.; Milanovich, F.; Lee, L.T. Jr.

    1993-03-05

    A vapor-phase, reagent-based, fiber optic trichloroethylene (TCE) sensor developed by Lawrence Livermore National Laboratory (LLNL) was demonstrated at the Savannah River Site (SRS) in two configurations. The first incorporated the sensor into a down-well instrument bounded by two inflatable packers capable of sealing an area for discrete depth analysis. The second involved an integration of the sensor into the probe tip of the Army Corps of Engineers Waterways Experiment Station (WES) cone penetrometry system. Discrete depth measurements of vapor-phase concentrations of TCE in the vadose zone were successfully made using both configurations. These measurements demonstrate the first successful in situ sensing (as opposed to sampling) of TCE at a field site.

  4. Biofiltration - an innovative approach to vapor phase treatment at the Silvex hazardous waste site in Florida

    SciTech Connect

    Hartsfield, B.

    1995-12-31

    Biofiltration is an emerging technology that is being used for vapor phase treatment at the Silvex hazardous waste site. Biofiltration works by directing the off-gas from the groundwater treatment system through a bed of soil, compost or other medium that supports the growth of bacteria. Contaminants are absorbed into the water present in the medium, and are subsequently degraded by the microorganisms. The biofiltration system at the Silvex hazardous waste site has been effective in removing contaminants from the off-gas. The biofiltration system has also been effective in minimizing the odor problem resulting from mercaptans in the off-gas. Biofiltration has been used for many years at wastewater and industrial plants to control odor and remove organic contaminants. This technology has only recently been used for hazardous waste site cleanups. The hazardous waste literature is now listing biofiltration as a vapor phase treatment technology, along with carbon, thermal oxidation and others.

  5. Selective vapor phase sensing of small molecules using biofunctionalized field effect transistors

    NASA Astrophysics Data System (ADS)

    Hagen, Joshua A.; Kim, Sang Nyon; Kelley-Loughnane, Nancy; Naik, Rajesh R.; Stone, Morley O.

    2011-05-01

    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 little to no selectivity. Addition of a biorecognition element retains the sensitivity of the device while adding selectivity. The DNA aptamer designed to bind the small molecule riboflavin was covalently integrated into the ZnO FET and detects the presence of 116 ppb of riboflavin in a nitrogen atmosphere by a change in current. The unfunctionalized ZnO FET shows no response to this same concentrations of riboflavin, showing that the aptamerbinding strategy may be a promising strategy for vapor phase sensing.

  6. Halide vapor phase epitaxy of twin-free ?-Ga2O3 on sapphire (0001) substrates

    NASA Astrophysics Data System (ADS)

    Oshima, Yuichi; Vllora, Encarnacin G.; Shimamura, Kiyoshi

    2015-05-01

    The halide vapor phase epitaxy of ?-Ga2O3 is demonstrated for the first time. The films are twin-free and heteroepitaxially grown on sapphire (0001) substrates using gallium chloride and oxygen as precursors. X-ray ?-2? and pole figure measurements reveal that the film is single-crystalline (0001) ?-Ga2O3 with no detectable formation of ?-Ga2O3. The optical bandgap is determined to be 5.16 eV based on the transmittance spectrum. The growth rate monotonically increases with the partial pressures of the raw material gases, reaching approximately 150 m/h, which is over two orders of magnitude larger than those of conventional vapor phase epitaxial growth techniques, such as mist CVD or MBE.

  7. Vapor Compression Hybrid Two-Phase Loop Technology for Lunar Surface Applications

    NASA Astrophysics Data System (ADS)

    Park, Chanwoo; Sunada, Eric

    2008-01-01

    NASA's vision for Space Exploration that would return humans to the Moon by 2020 in preparation for human explorations of Mars. This requires innovative technical advances. The lunar mission requires a temperature-lift (heat pump) technology to reject waste heat to hot lunar surface (heat sink) environments during lunar daytime. The lunar outpost and Lunar Surface Access Module (LSAM) to operate anywhere during the hot lunar daytime require a high performance and energy-efficient, yet reliable refrigeration technology. A vapor compressor-driven hybrid two-phase loop was developed for such high temperature-lift applications. The vapor compression loop used an advanced porous wick evaporator capable of gravity-insensitive capillary phase separation and excess liquid management to achieve high temperature-lift, large-area, isothermal and high heat flux cooling capability and efficient compression. The high temperature lift will allow the lunar surface systems use compact radiators by increased heat rejection temperature.

  8. The growth of vapor bubble and relaxation between two-phase bubble flow

    NASA Astrophysics Data System (ADS)

    Mohammadein, S. A.; Subba Reddy Gorla, Rama

    2002-10-01

    This paper presents the behavior of the bubble growth and relaxation between vapor and superheated liquid. The growth and thermal relaxation time between the two-phases are obtained for different levels of superheating. The heat transfer problem is solved numerically by using the extended Scriven model. Results are compared with those of Scriven theory and MOBY DICK experiment with reasonably good agreement for lower values of superheating.

  9. Sintering behavior of ultrafine silicon carbide powders obtained by vapor phase reaction

    NASA Technical Reports Server (NTRS)

    Okabe, Y.; Miyachi, K.; Hojo, J.; Kato, A.

    1984-01-01

    The sintering behavior of ultrafine SiC powder with average particle size of about 0.01-0.06 microns produced by a vapor phase reaction of the Me4Si-H2 system was studied at the temperature range of 1400-2050 deg. It was found that the homogeneous dispersion of C on SiC particles is important to remove the surface oxide layer effectively. B and C and inhibitive effect on SiC grain growth.

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

    NASA Technical Reports Server (NTRS)

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

    1984-01-01

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

  11. Radioiodination of interleukin 2 to high specific activities by the vapor-phase chloramine T method

    SciTech Connect

    Siekierka, J.J.; DeGudicibus, S.

    1988-08-01

    Recombinant human interleukin 2 (IL-2) was radioiodinated utilizing the vapor phase chloramine T method of iodination. The method is rapid, reproducible, and allows the efficient radioiodination of IL-2 to specific activities higher than those previously attained with full retention of biological activity. IL-2 radioiodinated by this method binds with high affinity to receptors present on phytohemagglutinin-stimulated peripheral blood lymphocytes and should be useful for the study of receptor structure and function.

  12. Transfer of amplitude and phase modulation to a different wavelength using coherently prepared sodium vapor

    SciTech Connect

    Bennink, Ryan S.; Marino, Alberto M.; Wong, Vincent; Boyd, Robert W.; Stroud, C. R. Jr.

    2005-08-15

    We present a scheme, based on coherent Raman scattering, to transfer the complete information content of an optical field from one spectral band to another with good efficiency, high fidelity, and large bandwidth. We demonstrate the transfer of both amplitude and phase modulation to new frequencies by scattering in a coherently prepared sodium vapor. The scattering process for this system has a bandwidth of at least tens of MHz and preserves the field envelope with a fidelity of 98%.

  13. Progress toward cascade cells made by OM-VPE. [organometallic vapor phase epitaxy

    NASA Technical Reports Server (NTRS)

    Borden, P. G.; Larue, R. A.; Ludowise, M. J.

    1982-01-01

    Organometallic Vapor Phase Epitaxy (COM-VPE) was used to make a sophisticated monolithic cascade cell, with a peak AMO efficiency of 16.6%, not corrected for 14% grid coverage. The cell has 9 epitaxial layers. The top cell is 1.35 microns thick with a 0.1 micron thich emitter. Both cells are heteroface n-p structures. The cascade cell uses metal interconnects. Details of growth and processing are described.

  14. Removal of Oxygen from Electronic Materials by Vapor-Phase Processes

    NASA Technical Reports Server (NTRS)

    Palosz, Witold

    1997-01-01

    Thermochemical analyses of equilibrium partial pressures over oxides with and without the presence of the respective element condensed phase, and hydrogen, chalcogens, hydrogen chalcogenides, and graphite are presented. Theoretical calculations are supplemented with experimental results on the rate of decomposition and/or sublimation/vaporization of the oxides under dynamic vacuum, and on the rate of reaction with hydrogen, graphite, and chalcogens. Procedures of removal of a number of oxides under different conditions are discussed.

  15. Vertical cavity surface emitting laser with 21% efficiency by metalorganic vapor phase epitaxy

    SciTech Connect

    Lear, K.L.; Schneider, R.P.; Choquette, K.D.; Kilcoyne, S.P.; Figiel, J.J.; Zolper, J.C. )

    1994-09-01

    Proton implanted, vertical cavity top-surface emitting lasers exhibit the highest single-mode and multi-mode output powers, highest power conversion efficiency, and lowest threshold voltage for such devices reported to date. These lasers use new mirror grading designs that are enabled by metalorganic vapor phase epitaxy's capabilities of alloy grading and carbon doping. The results validate this growth technology by exceeding the previous best results which were based on molecular beam epitaxy.

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

    PubMed

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

    2013-09-11

    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

  17. Metastable extension of the liquid-vapor phase equilibrium curve and surface tension.

    PubMed

    Baidakov, V G; Protsenko, S P; Kozlova, Z R; Chernykh, G G

    2007-06-01

    The method of molecular dynamics has been used to calculate the parameters of liquid-vapor phase equilibrium and the surface tension in a two-phase system of 4096 Lennard-Jones particles. Calculations have been made in a range from the triple point to near-critical temperature and also at temperatures below the triple point corresponding to the metastable equilibrium of a supercooled liquid and supersaturated vapor. To determine the surface tension, along with a mechanical approach a thermodynamic one has been used as well. The latter was based on calculation of the excess internal energy of an interfacial layer. It has been shown that in accuracy the thermodynamic approach is as good as the more sophisticated mechanical one. Low-temperature asymptotics of the phase-equilibrium curve and also of liquid and vapor spinodals have been considered in the Lennard-Jones and the van der Waals models. The behavior of the surface tension and the excess internal energy of an interfacial layer at T-->0 is discussed. PMID:17567206

  18. Optimum operating conditions of DIR-MCFC without vapor-phase carbonate pollution

    NASA Astrophysics Data System (ADS)

    Sugiura, Kimihiko; Daimon, Mayumi; Tanimoto, Kazumi

    In direct internal reforming-molten carbonate fuel cells (DIR-MCFC), deterioration of catalytic activity takes place in the anode channel due to both liquid-phase pollution and vapor-phase pollution. Although the liquid-phase pollution can be solved by installing protective barrier, an effective defense method and a reactivation method of vapor-phase polluted catalyst have not established yet. In order to study the reactivation method, the adhesion form of potassium compounds in the polluted catalyst under the various gas conditions was evaluated by using a thermogravimetric analyzer in which water vapor can feed. Additionally, the activity of the treated catalyst was also tested by a differential reactor. As a result, KOH changes to K 2CO 3 under a CO 2 concentration of 25% or more. KOH becomes a solid-phase from the liquid-phase when it is changed into K 2CO 3. Therefore, the catalyst can not be reactive because K 2CO 3 chokes pores of the catalyst. However, the activity of the polluted catalyst is revived to 80% of the initial activity by controlling the gas species concentration, especially CO 2. Moreover, the catalytic activity can be revived under a steam-carbon ratio of 2.0 or more. Based on the results obtained by these fundamental experiments, the reactivation methods of catalyst polluted are proposed as follows: (i) catalyst should be loaded more upstream in the anode; (ii) in order to reactivate the polluted catalyst, the DIR-MCFC should maintain a steam-carbon ratio of 2.0 or more; (iii) gas conditions to activate the catalyst should be applied regularly.

  19. Relative participation of the gas phase and total particulate matter in the imbalance in prostacyclin and thromboxane formation seen following chronic cigarette smoke exposure.

    PubMed

    Sherratt, A J; Culpepper, B T; Lubawy, W C

    1988-10-01

    Chronic exposure to cigarette smoke causes an imbalance in the ratio of PGI2 and TXA2 production and is believed to favor the development of atherosclerosis. Components of the particulate phase of smoke (especially nicotine) as well as the gas phase of smoke have been shown to adversely alter arachidonic acid metabolism. To determine the relative participation of nicotine, particulate and gas phases in eliciting an imbalance in TXA2 formation, male Sprague-Dawley rats were chronically exposed (7 days/wk/mo.) to freshly generated whole smoke or gas phase from University of Kentucky Reference cigarettes and allowed access to regular drinking water or to water supplemented with nicotine (10 micrograms/ml). COHb levels were monitored to confirm smoke or gas phase inhalation. All treatment groups had lower body weights than shams. No differences in body weights were observed between smoke (+/- oral nicotine) and gas phase (+/- oral nicotine) treatment groups but all were significantly lower than oral nicotine treated animals. Platelet TXA2 production was elevated in all treatment groups compared to shams. No differences in TXA2 production were observed between smoke (+/- oral nicotine), gas phase and oral nicotine treated animals. Animals receiving gas phase/oral nicotine exhibited significantly higher platelet TXA2 production compared to the other treatments. Constituents of the gas phase as well as the particulate phase of whole smoke were both shown to elevate platelet TXA2 formation. Components of the particulate matter appear to modulate the effects of nicotine and the gas phase in the perturbation of TXA2 production in the rat smoking model. PMID:3068679

  20. Synthesis of polymer nanoparticles via vapor phase deposition onto liquid substrates.

    PubMed

    Haller, Patrick D; Gupta, Malancha

    2014-12-01

    In this article, the growth of polymer nanoparticles formed at the liquid-vapor interface via vapor phase polymerization is studied. The particles grow by polymer aggregation, which is driven by the surface tension interaction between the liquid and polymer. It is demonstrated that the mechanism of particle growth is determined by whether polymer particles remain at the liquid-vapor interface or submerge into the liquid. The position of the particles depends on the interaction between the polymer and the liquid. For example, the deposition of poly(n-butyl acrylate) onto poly(dimethyl siloxane) and Krytox liquids leads to the formation of nanoparticles that remain at the liquid-vapor interface. The size of these particles increases as a function of deposition time. The deposition of poly(4-vinylpyridine) onto poly(dimethyl siloxane) and Krytox leads to the formation of nanoparticles that submerge into the liquid. The size of these particles does not significantly change with deposition time. Our study offers a new rapid, one-step synthetic approach for fabricating functional polymer nanoparticles for applications in catalysis, photonics, and drug delivery. PMID:25269429

  1. Modeling of liquid-vapor phase change using smoothed particle hydrodynamics

    NASA Astrophysics Data System (ADS)

    Das, A. K.; Das, P. K.

    2015-12-01

    A model has been proposed based on smoothed particle hydrodynamics to describe gas liquid phase change. Pseudo particles of zero mass are initially placed to locate the interface. Mass generated due to phase change is assigned to the pseudo particles and their positions are updated at intervals to track the mobility of the interface. The developed algorithm has been used to simulate vapor formation around solid spheres both in the absence of gravity and in the normal gravitational field. Finally, bubble growth over a hot horizontal surface due to boiling has been simulated. Simulated results showed good matching with the reported literature.

  2. The Similarity Relations Set on the Basis of Symmetrization of the Liquid-Vapor Phase Diagram.

    PubMed

    Apfelbaum, E M; Vorob'ev, V S

    2015-07-01

    An approach to symmetrize the liquid-vapor phase coexistence curve is proposed. It is based on the introduction of the lattice-like density x = ?1/(?1 + ?2), where ?1 and ?2 are the densities along the liquid-gas binodal. The global symmetrical phase diagram is created using experimental and simulation data for the real substances and models (noble gases, polyatomic molecules, organic substances and two metals, van der Waals system, Lennard-Jones system). The pressure and the temperature along the binodal are shown to satisfy some new similarity relations. PMID:26039358

  3. Laser-diode frequency control by resonant phase-conjugate reflection from an atomic vapor.

    PubMed

    Cyr, N; Breton, M; Têtu, M; Thériault, S

    1991-09-01

    We report our first results on the frequency control of an AlGaAs laser diode by resonant phase-conjugate reflection from an atomic rubidium vapor. When the electrical feedback technique is used, the Allan variance reaches a flicker floor such that sigma(y)(2)(tau) = 1.6 x 10(-19) tau(0) for tau > 1s. We also demonstrate that laser frequency locking can be achieved by using the phase-conjugate reflection directly as a resonant optical feedback. This approach leads to a self-controlled optical frequency standard at 780 nm. PMID:19776950

  4. Toxicological assessment of kretek cigarettes Part 6: the impact of ingredients added to kretek cigarettes on smoke chemistry and in vitro toxicity.

    PubMed

    Roemer, E; Dempsey, R; Hirter, J; Deger Evans, A; Weber, S; Ode, A; Wittke, S; Schorp, M K

    2014-12-01

    Mainstream smoke (MS) from experimental kretek cigarettes with three ingredient mixes at low (typical use level) and high (2.5 or 3 times that level) inclusion rates was compared to a control kretek cigarette of identical construction (cloves and humectants), but without the addition of ingredients. 350 ingredients, commonly used in various combinations and in a limited number in a given brand in the manufacture of marketed kretek cigarettes were assessed. The MS composition of the kretek cigarettes was characterized by a comprehensive set of analytes (55 smoke constituents). Furthermore, the smoke was assessed in vitro for its cytotoxicity in the Neutral Red Uptake assay (particle phase and gas/vapor phase separately) in mouse embryo BALB/c 3T3 cells, and for mutagenicity/genotoxicity in the Salmonella typhimurium reverse mutation assay and the mammalian cell mouse lymphoma TK assay in L5178Y cells, the latter with and without metabolic activation. There were some statistically significant differences in the yield of smoke constituents (increases as well as decreases, nearly all of them less than ± 20%) as a result of the addition of the ingredient mixes. However, the addition of the three different mixes of ingredients to the experimental kreteks did not change the in vitro cytotoxicity and mutagenicity/genotoxicity of the smoke, when compared to the control kretek cigarette. PMID:25496764

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

    PubMed Central

    2013-01-01

    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. PMID:23369269

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

    PubMed

    Karimi, Ali; Golbabaei, Farideh; Neghab, Masoud; Pourmand, Mohammad Reza; Nikpey, Ahmad; Mohammad, Kazem; Mehrnia, Momammad Reza

    2013-01-01

    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. PMID:23369269

  7. The mechanism of vapor phase hydration of calcium oxide: implications for CO2 capture.

    PubMed

    Kudłacz, Krzysztof; Rodriguez-Navarro, Carlos

    2014-10-21

    Lime-based sorbents are used for fuel- and flue-gas capture, thereby representing an economic and effective way to reduce CO2 emissions. Their use involves cyclic carbonation/calcination which results in a significant conversion reduction with increasing number of cycles. To reactivate spent CaO, vapor phase hydration is typically performed. However, little is known about the ultimate mechanism of such a hydration process. Here, we show that the vapor phase hydration of CaO formed after calcination of calcite (CaCO3) single crystals is a pseudomorphic, topotactic process, which progresses via an intermediate disordered phase prior to the final formation of oriented Ca(OH)2 nanocrystals. The strong structural control during this solid-state phase transition implies that the microstructural features of the CaO parent phase predetermine the final structural and physicochemical (reactivity and attrition) features of the product hydroxide. The higher molar volume of the product can create an impervious shell around unreacted CaO, thereby limiting the efficiency of the reactivation process. However, in the case of compact, sintered CaO structures, volume expansion cannot be accommodated in the reduced pore volume, and stress generation leads to pervasive cracking. This favors complete hydration but also detrimental attrition. Implications of these results in carbon capture and storage (CCS) are discussed. PMID:25233236

  8. Ordered organic thin films self-assembled from the vapor phase

    NASA Technical Reports Server (NTRS)

    Debe, M. K.

    1993-01-01

    Organic films self-assembled from a liquid phase, as in Langmuir-Blodgett or adsorption from solution, have received much attention in the past decade as techniques to achieve highly oriented-ordered polymeric thin films. Many organic compounds including some of the same fatty acids have been vapor deposited as well. However, organic pigments and dyes comprise a major class of important materials which have very low solubilities yet excellent thermal stabilities, making them ideally suited for film deposition from the vapor phase. Surprisingly, such molecular systems exhibit a significant propensity to self order, a high sensitivity to deposition parameters, and a range of microstructural forms that cannot be duplicated by the less energetic mechanisms associated with solution adsorption processes. Molecular solids such as heterocyclic polynuclear aromatics are excellent candidates for film formation by vacuum deposition means. Over the past decade, our work and that of others investigating a wide variety of perylene and phthalocyanine derivatives identified five deposition parameters that can significantly affect film morphology, physical microstructure, and type and extent of ordering developed in vacuum and vapor transport grown films. These parameters are substrate temperature, deposition rate, substrate chemistry and epitaxy, ambient gas convective flows, and post deposition annealing. Examples of how each of these conditions manifest themselves in the film structure and ordering, most frequently revealed by scanning electron microscopy, reflection absorption infrared spectroscopy (RAIR), and grazing incidence x-ray diffraction (GIX), are presented.

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

    NASA Astrophysics Data System (ADS)

    Gupta, Malancha

    2011-03-01

    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.

  10. Encapsulation of ionic liquids within polymer shells via vapor phase deposition.

    PubMed

    Bradley, Laura C; Gupta, Malancha

    2012-07-10

    We demonstrate the use of vapor phase deposition to completely encapsulate ionic liquid (IL) droplets within robust polymer shells. The IL droplets were first rolled into liquid marbles using poly(tetrafluoroethylene) (PTFE) particles because the marble structure facilitates polymerization onto the entire surface area of the IL. Polymer shells composed of 1H,1H,2H,2H-perfluorodecyl acrylate cross-linked with ethylene glycol diacrylate (P(PFDA-co-EGDA)) were found to be stronger than the respective homopolymers. Fourier transform infrared spectroscopy showed that the PTFE particles become incorporated into the polymer shells. The integration of the particles increased the rigidity of the polymer shells and enabled the pure IL to be recovered or replaced with other fluids. Our encapsulation technique can be used to form polymer shells onto dozens of droplets at once and can be extended to encapsulate any low vapor pressure liquid that is stable under vacuum conditions. PMID:22734891

  11. Fabrication of MEMS devices by using anhydrous HF gas-phase etching with alcoholic vapor

    NASA Astrophysics Data System (ADS)

    Ick Jang, Won; Auck Choi, Chang; Lee, Myung Lae; Jun, Chi Hoon; Kim, Youn Tae

    2002-05-01

    In silicon surface micromachining, anhydrous HF GPE process was verified as a very effective method for the dry release of microstructures. The developed gas-phase etching (GPE) process with anhydrous hydrogen fluoride (HF) gas and alcoholic vapor such as methanol, isopropyl alcohol (IPA) was characterized and its selective etching properties were discussed. The structural layers are P-doped multi-stacked polysilicon and silicon-on-insulator (SOI) substrates and sacrificial layers are tetraethylorthosilicate (TEOS), low-temperature oxide (LTO), plasma enhanced chemical vapor deposition (PECVD) oxide, phosphosilicate glass (PSG) and thermal oxides on silicon nitride or polysilicon substrates. We successfully fabricated and characterized micro electro mechanical system (MEMS) devices with no virtually process-induced stiction and no residues. The characteristics of the MEMS devices for microsensor and microactuator, microfluidic elements and optical MEMS application were evaluated by experiment.

  12. Comparison of the layer structure of vapor phase and leached SRL glass by use of AEM

    SciTech Connect

    Biwer, B.M.; Bates, J.K.; Abrajano, T.A. Jr.; Bradley, J.P.

    1990-12-31

    Test samples of 131 type glass that have been reacted for extended time periods in water vapor atmospheres of different relative humidities and in static leaching solution have been examined to characterize the reaction products. Analytical electron microscopy (AEM) was used to characterize the leached samples, and a complicated layer structure was revealed, consisting of phases that precipitate from solution and also form within the residual glass layer. The precipitated phases include birnes-site, saponite, and an iron species, while the intralayer phases include the U-Ti containing phase brannerite distributed within a matrix consisting of bands of an Fe rich montmorillonite clay. Comparison is made between samples leached at 40C for 4 years with those leached at 90C for 3-1/2 years. The samples reacted in water vapor were examined with scanning electron microscopy and show increasing reaction as both the relative humidity and time of reaction increases. These samples also contain a layered structure with reaction products on the glass surface.

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

    NASA Astrophysics Data System (ADS)

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

    2005-08-01

    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.

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

    SciTech Connect

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

    2001-07-03

    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.

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

    NASA Astrophysics Data System (ADS)

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

    2009-01-01

    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.

  16. Biodegradation of vapor-phase toluene in unsaturated porous media: Column experiments.

    PubMed

    Khan, Ali M; Wick, Lukas Y; Harms, Hauke; Thullner, Martin

    2016-04-01

    Biodegradation of organic chemicals in the vapor phase of soils and vertical flow filters has gained attention as promising approach to clean up volatile organic compounds (VOC). The drivers of VOC biodegradation in unsaturated systems however still remain poorly understood. Here, we analyzed the processes controlling aerobic VOC biodegradation in a laboratory setup mimicking the unsaturated zone above a shallow aquifer. The setup allowed for diffusive vapor-phase transport and biodegradation of three VOC: non-deuterated and deuterated toluene as two compounds of highly differing biodegradability but (nearly) identical physical and chemical properties, and MTBE as (at the applied experimental conditions) non-biodegradable tracer and internal control. Our results showed for toluene an effective microbial degradation within centimeter VOC transport distances despite high gas-phase diffusivity. Degradation rates were controlled by the reactivity of the compounds while oxic conditions were found everywhere in the system. This confirms hypotheses that vadose zone biodegradation rates can be extremely high and are able to prevent the outgassing of VOC to the atmosphere within a centimeter range if compound properties and site conditions allow for sufficiently high degradation rates. PMID:26774779

  17. The vapor phase dissociation of ammonium salts: Ammonium halides, ammonium rhodanide, ammonium nitrate, and ammonium bicarbonate

    NASA Astrophysics Data System (ADS)

    de Kruif, C. G.

    1982-12-01

    Vapor pressures as a function of temperature of the ammonium salts are measured by means of a simultaneous torsion effusion and mass-loss effusion technique. From a theoretical analysis, which is given first, it is shown that the enthalpies of sublimation and the degree of dissociation b in the vapor phase are related to the measured quantities. The degree of dissociation appears to be a weak function of temperature and is evaluated by b(NH4F, 288.91 K)=0.97; b(NH4Cl, 352.02 K)=0.85; b(NH4Br, 380.06 K)=0.51; b(NH4I, 385.03 K)=0.39; b(NH4CNS, 313.78 K)=0.61; b(NH4NO3, 351.89 K)=0.66; b(NH4HCO3, 270.56)=0.85. It is assumed that NH4HCO3 dissociates into NH3, H2O, and CO2. At the given temperatures, total vapor pressure is 0.40 Pa.

  18. Vapor-phase hydrogen peroxide as a surface decontaminant and sterilant.

    PubMed Central

    Klapes, N A; Vesley, D

    1990-01-01

    The feasibility of utilizing vapor-phase hydrogen peroxide (VPHP) as a surface decontaminant and sterilant was evaluated in a centrifuge application. The prototype VPHP decontamination system, retrofitted into a Beckman L8-M ultracentrifuge, was designed to vaporize a 30% (wt/wt) solution of aqueous hydrogen peroxide continuously injecting and withdrawing VPHP in a deep-vacuum flow-through system. VPHP cycles of 4, 8, 16, and 32 min were examined for cidal activity against spores of Bacillus subtilis subsp. globigii and Bacillus stearothermophilus. Spore inocula (approximately 10(6)/coupon) were dried onto 0.5-in. (1.27-cm)-square stainless-steel coupons, and coupons were suspended in the centrifuge chamber, the space between the refrigeration can and the barrier ring (inner gap), and the space between the barrier ring and the vacuum ring (outer gap). At a chamber temperature of 4 degrees C, B. subtilis subsp. globigii spores were inactivated within 8 min, while inactivation of spores located in the outer gap at 27 degrees C required 32 min. The elevated temperature and high surface area/volume ratios in the outer gap may serve to decompose the gas more rapidly, thus reducing cidal efficacy. Of the two test spores, B. stearothermophilus was more resistant to VPHP. Nonetheless, VPHP was shown to possess significant sporicidal capability. For practical decontamination applications of the type described, VPHP shows promise as an effective and safer alternative to currently used ethylene oxide or formaldehyde vapors. PMID:2106287

  19. Vapor phase adsorption-desorption of 1,1,1-trichloroethane on dry soil

    SciTech Connect

    Dural, N.H.; Chen, C.H.

    1995-12-31

    Vapor phase adsorption of 1,1,1-trichloroethane (TCA) on dry soils was studied at 288, 293, and 298 K. Using a gravimetric adsorption apparatus adsorption/desorption isotherms of TCA were generated on two representing soil samples with different physical/chemical characteristics. Influence of temperature and soil properties were investigated. Isosteric heats of adsorption were calculated and heat curves were established. The experimental data were correlated by the Polanyi Potential, the BET, and the GAB models. Equilibrium isotherms of TCA on both soils were Type 2, characterizing vapor condensation to form multilayers, and they exhibited hysteresis upon desorption. A positive correlation between the soil`s specific surface area and its sorption capacity was observed. Clay content and pore size were also dominating factors. Thermal data showed that the adsorption of TCA vapor on soil was primarily due to physical forces and both samples exhibited energetically heterogeneous surfaces. Results followed the Potential Theory satisfactorily and led to a single temperature-independent characteristic curve for each soil-TCA pair. The BET equation gave accurate correlations for up to 40 % of the saturation pressure, while the GAB equation provided superior correlation of the data for the entire relative pressure range.

  20. Liquid-Vapor Phase Extraction of Gasoline for In Situ Amelioration of Contaminated Clayey Soil

    NASA Astrophysics Data System (ADS)

    Sharma, S.; Spencer, S.

    2008-12-01

    Liquid-vapor phase extraction (LVPE) of hydrocarbon is a recognized technique for rapid remediation of gasoline contaminated soils and waters. On site application of LVPE is, however, challenging in clayey soils. Four LVPE events were conducted during a 10-month period at a central Californian site that had been contaminated with gasoline due to leakage of underground storage tanks. The site was underlain by unconsolidated alluvial deposits and the soil profile consisted of layers of sandy clays and silty clays with low water table. The objectives of this study were to reduce floating product volume in well waters and to remove petroleum hydrocarbons within the vadose zone. Groundwater was extracted by lowering a stinger to the groundwater surface and applying vacuum. The stingers were able to extract down to 20 ft below ground surface. Vacuum was applied at 25 in of Hg pressure and the LVPE unit extracted soil vapor at the rate of 54 ft3/min. Samples were collected periodically from the extracted groundwater, treated groundwater, extracted soil vapor, and analyzed for gasoline and its constituents. The LVPE showed a moderate impact on the floating product found beneath the site. The volumes of floating product, although measurable, were reduced significantly after the extraction operations. High hydrocarbon concentrations in soil vapor at initial period of extraction events suggested that hydrocarbon vaporization followed a rapid kinetics. During first couple of extraction events, this surge was a followed by a quick decline in concentrations over time. The vaporization process appeared to have reached steady state after repetitive extraction activities. The LVPE system extracted about 288-336 (x1000) liters of groundwater and 88-358 kg of hydrocarbons during the events. In subsequent monitoring studies, significant concentrations of gasoline and its constituents were detected in the well waters. This suggested that the residual contaminant pool could replenish the mobile hydrocarbon pool despite removal operations. The radius of influence of LVPE remained within 10 ft in both saturated and unsaturated zones due to the clayey soil structure. The overall mass of petroleum hydrocarbons remaining in the vadose zone around the wells appeared to have diminished.

  1. Hydride vapor phase epitaxy of AlN using a high temperature hot-wall reactor

    NASA Astrophysics Data System (ADS)

    Baker, Troy; Mayo, Ashley; Veisi, Zeinab; Lu, Peng; Schmitt, Jason

    2014-10-01

    Aluminum nitride (AlN) was grown on c-plane sapphire substrates by hydride vapor phase epitaxy (HVPE). The experiments utilized a two zone inductively heated hot-wall reactor. The surface morphology, crystal quality, and growth rate were investigated as a function of growth temperature in the range of 1450-1575 °C. AlN templates grown to a thickness of 1 μm were optimized with double axis X-ray diffraction (XRD) rocking curve full width half maximums (FWHMs) of 135″ for the (002) and 513″ for the (102).

  2. Vapor phase growth technique of III-V compounds utilizing a preheating step

    NASA Technical Reports Server (NTRS)

    Olsen, Gregory Hammond (Inventor); Zamerowski, Thomas Joseph (Inventor); Buiocchi, Charles Joseph (Inventor)

    1978-01-01

    In the vapor phase epitaxy fabrication of semiconductor devices and in particular semiconductor lasers, the deposition body on which a particular layer of the laser is to be grown is preheated to a temperature about 40.degree. to 60.degree. C. lower than the temperature at which deposition occurs. It has been discovered that by preheating at this lower temperature there is reduced thermal decomposition at the deposition surface, especially for semiconductor materials such as indium gallium phosphide and gallium arsenide phosphide. A reduction in thermal decomposition reduces imperfections in the deposition body in the vicinity of the deposition surface, thereby providing a device with higher efficiency and longer lifetime.

  3. Spiral growth of InP by metalorganic vapor phase epitaxy

    NASA Astrophysics Data System (ADS)

    Hsu, C. C.; Xu, J. B.; Wilson, I. H.

    1994-09-01

    Spirals were observed on InP grown by metalorganic vapor phase epitaxy. Atomic force microscopy is the technique used. The growth took place on a vicinal surface and the growth mechanism is according to the classical Burton-Cabrera-Frank theory. Spirals originate from screw dislocations. Successive turns of steps are sent out by the dislocations. These steps are generally of monolayer height (0.29 nm) except close to the dislocation emergence points where they are submonolayers. It is predicted that spiral growth will become the dominant mechanism if the vicinal steps are eliminated.

  4. Simulation and testing of a vertical organometallic vapor phase epitaxy reactor

    NASA Astrophysics Data System (ADS)

    Sani, R. A.; Barmawi, M.; Mindara, J. Y.

    1998-02-01

    The purpose of the study is to design a single wafer vertical organo-metallic vapor phase epitaxy (OMVPE) reactor which gives a uniform deposition around the symmetry axis. The vertical reactor under the consideration consist of a diffuser and a system of coaxial cylinders to laminarize the flow which may lead to a uniform deposition without rotating the susceptor. The simulation shows that for a susceptor with a radius of 2.5 cm, a uniformity can be achieved in a region of a radius of 2 cm within 1% for certain operating condition. The result is compared with the experimental measurement of TiO2 deposition from TTIP.

  5. Performance Testing of the Vapor Phase Catalytic Ammonia Removal Engineering Development Unit

    NASA Technical Reports Server (NTRS)

    Flynn, Michael; Tleimat, Maher; Nalette, Tim; Quinn, Gregory

    2005-01-01

    This paper describes the results of performance testing of the Vapor Phase Catalytic Ammonia Removal (VPCAR) technology. The VPCAR technology is currently being developed by NASA as a Mars transit vehicle water recycling system. NASA has recently completed-a grant-to develop a next generation VPCAR system. This grant concluded with the shipment of the final deliverable to NASA on 8/31/03. This paper presents the results of mass, power, volume, and acoustic measurements for the delivered system. Product water purity analysis for a Mars transit mission and a simulated planetary base wastewater ersatz are also provided.

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

    SciTech Connect

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

    1999-09-30

    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 requirements are outlined and a range of appropriate response actions are presented. These solutions range from modification of bioreactor design and operation (e.g., step feed configuration and directionally switching operation) to the use of alternative types of microorganisms (e.g., fungi).

  7. Development of advanced zeolite catalysts for the vapor phase Beckmann rearrangement of cyclohexanone oxime

    NASA Astrophysics Data System (ADS)

    Dai, Lian-Xin; Iwaki, Yoshihide; Koyama, Katsuyuki; Tatsumi, Takashi

    1997-11-01

    The vapor phase Beckmann rearrangement of cyclohexanone oxime to ɛ-caprolactam catalyzed by various zeolites was studied. The catalytic performance was greatly affected by both the zeolite structure and diluent solvent. When 1-hexanol was used in place of benzene, the catalytic performance of all catalysts except silicalite-1 was greatly improved. In particular, the selectivity and stability of H-LTL and H-OFF-ERI zeolites remarkably increased; both catalysts exhibited ca. 100% oxime conversion and ɛ-caprolactam selectivity of >95% for 6 h.

  8. Triboluminescence and vapor-induced phase transitions in the solids of methyltriphenylphosphonium tetrahalomanganate(II) complexes.

    PubMed

    Balsamy, Sujitha; Natarajan, Palani; Vedalakshmi, Rathinavel; Muralidharan, Srinivasan

    2014-06-16

    Triboluminescence (TL) of the methyltriphenylphosphonium tetrahalomanganate(II) complexes such as bis(methyltriphenylphosphonium) tetrabromomanganate (PMBB) and bis(methyltriphenylphosphonium) dibromodichloromanganate (PMBC) was switched ON and OFF reversibly by vapors of aprotic and protic solvents, respectively, for the first time. Detailed analyses indicate that solids of the PMBB and the PMBC undergo phase transitions depending on the environment, which regulate the TL activity of these compounds. The combined results of luminescence, powder X-ray diffraction, differential scanning calorimetry, and electron paramagnetic resonance were used to demonstrate crystal dynamism as well as the TL emission of PMBB and PMBC. PMID:24899549

  9. Freestanding GaN Wafers by Hydride Vapor Phase Epitaxy Using Void-Assisted Separation Technology

    NASA Astrophysics Data System (ADS)

    Oshima, Y.; Yoshida, T.; Eri, T.; Watanabe, K.; Shibata, M.; Mishima, T.

    An outline is presented of the fabrication technique of freestanding GaN wafers by hydride vapor phase epitaxy using the void-assisted separation method and the properties of resulting crystals. A thick GaN layer of large area can be separated with excellent reproducibility from a base substrate by the application of thermal stress. This process is assisted by numerous voids formed near the interface between the thick GaN layer and the base substrate. By using this method, high-quality GaN wafers of large area with diameters of over 3 in. have been prepared.

  10. Synthesis of graphene nanoribbons from amyloid templates by gallium vapor-assisted solid-phase graphitization

    SciTech Connect

    Murakami, Katsuhisa Dong, Tianchen; Kajiwara, Yuya; Takahashi, Teppei; Fujita, Jun-ichi; Hiyama, Takaki; Takai, Eisuke; Ohashi, Gai; Shiraki, Kentaro

    2014-06-16

    Single- and double-layer graphene nanoribbons (GNRs) with widths of around 10 nm were synthesized directly onto an insulating substrate by solid-phase graphitization using a gallium vapor catalyst and carbon templates made of amyloid fibrils. Subsequent investigation revealed that the crystallinity, conductivity, and carrier mobility were all improved by increasing the temperature of synthesis. The carrier mobility of the GNR synthesized at 1050 °C was 0.83 cm{sup 2}/V s, which is lower than that of mechanically exfoliated graphene. This is considered to be most likely due to electron scattering by the defects and edges of the GNRs.

  11. Higher cigarette prices influence cigarette purchase patterns

    PubMed Central

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

    2005-01-01

    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. PMID:15791017

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

    SciTech Connect

    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

    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.

  13. Evaluation of solid-phase microextraction in detection of contraband drug vapors

    NASA Astrophysics Data System (ADS)

    Orzechowska, Grazyna E.; Poziomek, Edward J.; Tersol, Vangielynn; Homstead, Juliana

    1997-02-01

    Solid phase microextraction (SPME) has emerged as a rapid alternative to conventional sample extraction techniques. SPME can be used in solids, liquids, and sample headspace. Compounds are sorbed by a stationary phase coated on a fused silica fiber. The compounds are desorbed, and analyzed using gas chromatography (GC), and high performance liquid chromatography (HPLC). As a part of the present work we have found that SPME can also be used conveniently with ion mobility spectrometry (IMS). Cocaine and heroin vapors sorbed on a SPME fiber were detected using IMS. The use of SPME-GC or SPME-HPLC has been reported in analysis of urine samples containing cocaine and its metabolites. We are evaluating SPME-IMS, and SPME-GC systems for the detection of cocaine and heroin and their decomposition products in the headspace above surfaces. This is part of our research on the surface decomposition of contraband drugs for detection applications. This paper will give a variety of examples in the use of SPME in the detection of contraband drugs and their reaction/decomposition products in the vapor state. An example is the detection of cocaine in the headspace above cocaine HCl at room temperature.

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

    SciTech Connect

    Dadmun, Mark D; Algaier, Dana; Baskaran, Durairaj

    2011-01-01

    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.

  15. Feasibility Study of Vapor-Mist Phase Reaction Lubrication Using a Thioether Liquid

    NASA Technical Reports Server (NTRS)

    Morales, Wilfredo; Handschuh, Robert F.; Krantz, Timothy L.

    2007-01-01

    A primary technology barrier preventing the operation of gas turbine engines and aircraft gearboxes at higher temperatures is the inability of currently used liquid lubricants to survive at the desired operating conditions over an extended time period. Current state-of-the-art organic liquid lubricants rapidly degrade at temperatures above 300 C; hence, another form of lubrication is necessary. Vapor or mist phase reaction lubrication is a unique, alternative technology for high temperature lubrication. The majority of past studies have employed a liquid phosphate ester that was vaporized or misted, and delivered to bearings or gears where the phosphate ester reacted with the metal surfaces generating a solid lubricious film. This method resulted in acceptable operating temperatures suggesting some good lubrication properties, but the continuous reaction between the phosphate ester and the iron surfaces led to wear rates unacceptable for gas turbine engine or aircraft gearbox applications. In this study, an alternative non-phosphate liquid was used to mist phase lubricate a spur gearbox rig operating at 10,000 rpm under highly loaded conditions. After 21 million shaft revolutions of operation the gears exhibited only minor wear.

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

    NASA Astrophysics Data System (ADS)

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

    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.

  17. Thermodynamics of Si(OH)4 in the vapor phase of water: Henrys and vapor-liquid distribution constants, fugacity and cross virial coefficients

    NASA Astrophysics Data System (ADS)

    Plyasunov, Andrey V.

    2012-01-01

    The fugacity coefficients of Si(OH)4 are evaluated from solubilities of solid phases of SiO2 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 H2O-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 Henrys 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 H2O-SiO2 system at steam densities up to 200 kg m-3.

  18. Metal organic vapor phase epitaxy of hexagonal Ge-Sb-Te (GST)

    NASA Astrophysics Data System (ADS)

    Schuck, Martin; Rieß, Sally; Schreiber, Marcel; Mussler, Gregor; Grützmacher, Detlev; Hardtdegen, Hilde

    2015-06-01

    Epitaxial, hexagonal Ge-Sb-Te was grown on Si(111) substrates by Metal Organic Vapor Phase Epitaxy (MOVPE) using the precursor digermane. The effect of reactor pressure, growth temperature and in situ pre-treatment on morphology and Ge-Sb-Te composition was studied. The composition is sensitive to reactor pressure and growth temperature. Compositional control is achieved at a reactor pressure of 50 hPa. Substrate pre-treatment affects film coalescence. The use of hydrogen and a suitable precursor pre-treatment leads to enhanced surface coverage. X-ray diffraction reveals a trigonal structure with lattice parameters close to that reported for Ge1Sb2Te4 crystallizing in the R 3 bar m phase. The composition was confirmed by energy-dispersive X-ray spectroscopy.

  19. He II Liquid/Vapor Phase Separator for Large Dynamic Range Operation

    NASA Technical Reports Server (NTRS)

    Nakano, A.; Petrac, D.

    1995-01-01

    A phase separator, which separates helium vapor from liquid superfluid helium (He II), is an indispensable device for space cryogenics. The most recent approach to the Space Infrared Telescope Facility (SIRTF) uses a new design concept in which only the detector package is cold at launch, the remainder of the telescope being subsequently cooled to operating temperature on orbit. Therefore, a large dynamic operational range is required of the cryogen system. This is a report of initial laboratory test results with candidate porous plugs as phase separators. Mass flow rates and pressure and temperature differences across a porous plug were measured in this experiment. Relatively large mass flow rates were observed even at small pressure differences. In the high mass flow rate region, a hysteresis was observed with increases and decreases of the pressure difference. A linear theory is proposed and compared with experimental data to explain several phenomena observed in this system.

  20. On the existence of vapor-liquid phase transition in dusty plasmas

    SciTech Connect

    Kundu, M.; Sen, A.; Ganesh, R.; Avinash, K.

    2014-10-15

    The phenomenon of phase transition in a dusty-plasma system (DPS) has attracted some attention in the past. Earlier Farouki and Hamaguchi [J. Chem. Phys. 101, 9876 (1994)] have demonstrated the existence of a liquid to solid transition in DPS where the dust particles interact through a Yukawa potential. However, the question of the existence of a vapor-liquid (VL) transition in such a system remains unanswered and relatively unexplored so far. We have investigated this problem by performing extensive molecular dynamics simulations which show that the VL transition does not have a critical curve in the pressure versus volume diagram for a large range of the Yukawa screening parameter κ and the Coulomb coupling parameter Γ. Thus, the VL phase transition is found to be super-critical, meaning that this transition is continuous in the dusty plasma model given by Farouki and Hamaguchi. We provide an approximate analytic explanation of this finding by means of a simple model calculation.

  1. Flux-mediated epitaxy: general application in vapor phase epitaxy to single crystal quality of complex oxide films

    NASA Astrophysics Data System (ADS)

    Matsumoto, Y.; Takahashi, R.; Koinuma, H.

    2005-02-01

    We propose a general term flux-mediated epitaxy (FME) to single crystal quality of complex oxide thin films in vapor-phase epitaxy. The key is a flux, which is frequently used in a bulk process for lowering a process temperature and suppressing incongruent melt. The successful application of the flux to the bulk single crystal growth allows us to expect a similar benefit even in the case of vapor-phase epitaxy. In this paper, we discuss on the capability of this general concept 'FME' for controlling phases and crystallinity of the complex oxide films, showing some examples such as optical, ferromagnetic oxide and high- Tc superconductor.

  2. Vapor-phase synthesis of uniform silica spheres through two-stage hydrolysis of SiCl{sub 4}

    SciTech Connect

    Park, Hoey K.; Park, Kyun Y.

    2008-11-03

    We report, for the first time, a vapor-phase synthesis of nearly monodispersed silica spheres 250-300 nm in size through a two-stage hydrolysis of SiCl{sub 4}. In the first stage, SiCl{sub 4} vapor was partially hydrolyzed with water vapor in a batch reactor at 150 deg. C to form silicon oxychloride particles, nearly monodispersed and spherical. In the second stage, these oxychloride particles were converted into silica particles through further hydrolysis at 1000 deg. C in a tubular reactor, while the morphology and size after the first-stage reaction remained virtually unchanged.

  3. Stimulated topological condensation of 'vapor phase' photons and possible implications for space power technology

    SciTech Connect

    Dudziak, M.; Pitkaenen, M.

    1999-01-22

    A quantum topological network model that might allow for the production of energy through the employment of vacuum electromagnetic currents form is based upon foundational principles of topological geometrodynamics (TGD) (Pitkaenen, 1995a, 1995b). Such a production photon-factory would have the capability of drawing upon a seemingly inexhaustible supply of what in TGD formalism is a 'vapor phase' of photons. Particularly in the presence of Bose-Einstein condensate photons, it is theoretically possible to convert these 'vapor phase' photons into condensed photons that can then be harnessed and transformed into useful kinetic energy by more traditional means. TGD presents a view, similar to certain string models, of spacetimes as surfaces within an 8-dimensional space H that is a product of Minkowski space future lightcone M{sub +}{sup 4} and a complex projective space CP{sub 2}. TGD model allows for topological merging, akin to the condensation process in classical physics, of free elementary particle like 3-surfaces to the background surface of larger size. 'Topological evaporation' corresponds to the reverse of this process in which particles go 'outside' the classical spacetime. TGD predicts vacuum electromagnetic fields having as their source vacuum gauge currents instead of currents composed of elementary particles. The vacuum gauge currents generate coherent states of photons and for the lightlike vacuum currents the coherent state arises in a resonant-like manner. A presence of Bose-Einstein condensates of photons in a nearby spacetime sheet external to the coherent-state generator would allow for a transfer of photons from that sheet into a vapor phase. The capture of these photons into an electro-mechanical propulsion system may provide a source of energy which can be converted into a form useful for the propulsion and acceleration of a space craft. An emission of coherent light from a region not containing charged particles would be a clear indication of vacuum current presence. Whether this entire process, if it is feasible, could generate enough useful energy for spacecraft propulsion is a major open question. However, it does appear that in the least such a mechanism could provide for some type of quantum communication with storage of information in both phase and intensity of the coherent emf and with the vacuum currents acting as quantum antennae. An examination of certain models known as quantum cellular automata and networks (QCAM, CLAN) (Dudziak, 1993) and synchronized heterogeneous dynamical networks (SHDN) (Chinarov, 1998) may provide some further insight into how the suggested stimulated coherent production of photons might be initiated, controlled, and stabilized in an application for space travel or communication.

  4. APTS and rGO co-functionalized pyrenated fluorescent nanonets for representative vapor phase nitroaromatic explosive detection

    NASA Astrophysics Data System (ADS)

    Guo, Linjuan; Zu, Baiyi; Yang, Zheng; Cao, Hongyu; Zheng, Xuefang; Dou, Xincun

    2014-01-01

    For the first time, flexible PVP/pyrene/APTS/rGO fluorescent nanonets were designed and synthesized via a one-step electrospinning method to detect representative subsaturated nitroaromatic explosive vapor. The functional fluorescent nanonets, which were highly stable in air, showed an 81% quenching efficiency towards TNT vapor (~10 ppb) with an exposure time of 540 s at room temperature. The nice performance of the nanonets was ascribed to the synergistic effects induced by the specific adsorption properties of APTS, the fast charge transfer properties and the effective ?-? interaction with pyrene and TNT of rGO. Compared to the analogues of TNT, the PVP/pyrene/APTS/rGO nanonets showed notable selectivity towards TNT and DNT vapors. The explored functionalization method opens up brand new insight into sensitive and selective detection of vapor phase nitroaromatic explosives.For the first time, flexible PVP/pyrene/APTS/rGO fluorescent nanonets were designed and synthesized via a one-step electrospinning method to detect representative subsaturated nitroaromatic explosive vapor. The functional fluorescent nanonets, which were highly stable in air, showed an 81% quenching efficiency towards TNT vapor (~10 ppb) with an exposure time of 540 s at room temperature. The nice performance of the nanonets was ascribed to the synergistic effects induced by the specific adsorption properties of APTS, the fast charge transfer properties and the effective ?-? interaction with pyrene and TNT of rGO. Compared to the analogues of TNT, the PVP/pyrene/APTS/rGO nanonets showed notable selectivity towards TNT and DNT vapors. The explored functionalization method opens up brand new insight into sensitive and selective detection of vapor phase nitroaromatic explosives. Electronic supplementary information (ESI) available: Vapor pressure of TNT and its analogues, fluorescence quenching kinetics, fluorescence quenching efficiencies and additional SEM images. See DOI: 10.1039/c3nr04960d

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

    SciTech Connect

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

    1994-05-01

    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.

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

    SciTech Connect

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

    1994-12-31

    A thermal desorption/gas chromatography/mass spectrometry (TD/GC/MS) method has been evaluated for the determination of volatile organic compounds (VOCs) in vapor phase samples using Carbosieve S-III/Carbotrap/Carbotrap 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 in-house manufactured short-path desorber for transferring desorbate directly onto a cryofocusing loop for subsequent GC/MS analysis. Vapor phase standards generated from 26 compounds were used for method validation, including alkanes, alkyl alcohols, alkyl ketones, and alkyl nitriles, 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 traps in a 4 C refrigerator for 29 days. The only chromatographic artifact observed was a 5% conversion of isopropanol to acetone. The validated method has been successfully applied to the determination of VOCs collected from various emission sources in a diversified concentration range.

  7. Desalination of water by vapor-phase transport through hydrophobic nanopores

    NASA Astrophysics Data System (ADS)

    Lee, Jongho; Karnik, Rohit

    2010-08-01

    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.

  8. Evaluating the robustness of the enantioselective stationary phases on the Rosetta mission against space vacuum vaporization

    NASA Astrophysics Data System (ADS)

    Meierhenrich, Uwe J.; Cason, Julie R. L.; Szopa, Cyril; Sternberg, Robert; Raulin, François; Thiemann, Wolfram H.-P.; Goesmann, Fred

    2013-12-01

    The European Space Agency's Rosetta mission was launched in March 2004 in order to reach comet 67P/Churyumov-Gerasimenko by August 2014. The Cometary Sampling and Composition experiment (COSAC) onboard the Rosetta mission's lander "Philae" has been designed for the cometary in situ detection and quantification of organic molecules using gas chromatography coupled to mass spectrometry (GC-MS). The GC unit of COSAC is equipped with eight capillary columns that will each provide a specific stationary phase for molecular separation. Three of these stationary phases will be used to chromatographically resolve enantiomers, as they are composed of liquid polymers of polydimethylsiloxane (PDMS) to which chiral valine or cyclodextrin units are attached. Throughout the ten years of Rosetta's journey through space to reach comet 67P, these liquid stationary phases have been exposed to space vacuum, as the capillary columns within the COSAC unit were not sealed or filled with carrier gas. Long term exposures to space vacuum can cause damage to such liquid stationary phases as key monomers, volatiles, and chiral selectors can be vaporized and lost in transit. We have therefore exposed identical spare units of COSAC's chiral stationary phases over eight years to vacuum conditions mimicking those experienced in space and we have now investigated their resolution capabilities towards different enantiomers both before and after exposure to space vacuum environments. We have observed that enantiomeric resolution capabilities of these chiral liquid enantioselective stationary phases has not been affected by exposure to space vacuum conditions. Thus we conclude that the three chiral stationary phases of the COSAC experiment onboard the Rosetta mission lander "Philae" can be considered to have maintained their resolution capacities throughout their journey prior to cometary landing in November 2014.

  9. Vapor-deposited non-crystalline phase vs ordinary glasses and supercooled liquids: Subtle thermodynamic and kinetic differences

    SciTech Connect

    Bhattacharya, Deepanjan; Sadtchenko, Vlad

    2015-04-28

    Vapor deposition of molecules on a substrate often results in glassy materials of high kinetic stability and low enthalpy. The extraordinary properties of such glasses are attributed to high rates of surface diffusion during sample deposition, which makes it possible for constituents to find a configuration of much lower energy on a typical laboratory time scale. However, the exact nature of the resulting phase and the mechanism of its formation are not completely understood. Using fast scanning calorimetry technique, we show that out-of-equilibrium relaxation kinetics and possibly the enthalpy of vapor-deposited films of toluene and ethylbenzene, archetypical fragile glass formers, are distinct from those of ordinary supercooled phase even when the deposition takes place at temperatures above the ordinary glass softening transition temperatures. These observations along with the absolute enthalpy dependences on deposition temperatures support the conjecture that the vapor-deposition may result in formation of non-crystalline phase of unique structural, thermodynamic, and kinetic properties.

  10. ZnO Nanowires Synthesized by Vapor Phase Transport Deposition on Transparent Oxide Substrates

    PubMed Central

    2010-01-01

    Zinc oxide nanowires have been synthesized without using metal catalyst seed layers on fluorine-doped tin oxide (FTO) substrates by a modified vapor phase transport deposition process using a double-tube reactor. The unique reactor configuration creates a Zn-rich vapor environment that facilitates formation and growth of zinc oxide nanoparticles and wires (2080 nm in diameter, up to 6 ?m in length, density <40 nm apart) at substrate temperatures down to 300C. Electron microscopy and other characterization techniques show nanowires with distinct morphologies when grown under different conditions. The effect of reaction parameters including reaction time, temperature, and carrier gas flow rate on the size, morphology, crystalline structure, and density of ZnO nanowires has been investigated. The nanowires grown by this method have a diameter, length, and density appropriate for use in fabricating hybrid polymer/metal oxide nanostructure solar cells. For example, it is preferable to have nanowires no more than 40 nm apart to minimize exciton recombination in polymer solar cells. PMID:20676196

  11. Development of an acoustic wave based biosensor for vapor phase detection of small molecules

    NASA Astrophysics Data System (ADS)

    Stubbs, Desmond

    For centuries scientific ingenuity and innovation have been influenced by Mother Nature's perfect design. One of her more elusive designs is that of the sensory olfactory system, an array of highly sensitive receptors responsible for chemical vapor recognition. In the animal kingdom this ability is magnified among canines where ppt (parts per trillion) sensitivity values have been reported. Today, detection dogs are considered an essential part of the US drug and explosives detection schemes. However, growing concerns about their susceptibility to extraneous odors have inspired the development of highly sensitive analytical detection tools or biosensors known as "electronic noses". In general, biosensors are distinguished from chemical sensors in that they use an entity of biological origin (e.g. antibody, cell, enzyme) immobilized onto a surface as the chemically-sensitive film on the device. The colloquial view is that the term "biosensors" refers to devices which detect the presence of entities of biological origin, such as proteins or single-stranded DNA and that this detection must take place in a liquid. Our biosensor utilizes biomolecules, specifically IgG monoclonal antibodies, to achieve molecular recognition of relatively small molecules in the vapor phase.

  12. Vapor-phase biofilters make bid for VOC control in industrial applications

    SciTech Connect

    Stewart, W.C.; Thom, R.R.

    1996-09-01

    Biofiltration of contaminated air streams containing volatile organic compounds (VOCs) is a relatively new application of biotechnology in the waste management industry. The primary stimulus for development of vapor-phase biofiltration in Europe is its capability for efficient and reliable VOC destruction without forming hazardous by-products, coupled with low operating and life-cycle costs compared to conventional physical-chemical alternatives. The filters operate by passing the contaminated air stream through a bed of compost, peat, soil or other permeate material, which acts as an attachment site for rich microbial fauna. After the VOCs have been sorbed from the air stream while passing through the bed, the microorganisms use the sorbed organics as a food source, converting the pollutant into carbon dioxide and water vapor. As the organic pollutant is metabolized, the binding site to which it was attached again becomes available to strip additional VOC molecules from the incoming air stream. Thus, the biofilters reach a steady state, and sorption and biological destruction is followed by re-sorption of fresh volatile pollutants. Under proper conditions, this sequence of reactions occurs quite rapidly.

  13. Computational fluid dynamics-aided analysis of a hydride vapor phase epitaxy reactor

    NASA Astrophysics Data System (ADS)

    Schulte, Kevin L.; Simon, John; Roy, Abhra; Reedy, Robert C.; Young, David L.; Kuech, Thomas F.; Ptak, Aaron J.

    2016-01-01

    We report the development of a computational fluid dynamics (CFD) model of a dual chamber hydride vapor phase epitaxial (HVPE) growth reactor. Uniformity of reactant concentrations in the growth stream, transient reactor flows, and cross doping between the two growth chambers, all factors critical to the deposition of uniform, low defect semiconductor layers, were modeled. Simulation results were generated by solving the fundamental continuity, momentum and energy equations over a discretized reactor volume by a finite volume analysis with the aid of CFD-ACE+ commercial software. We demonstrated uniformity of the vapor composition within ±1% across the substrate, achieved due to specific features of the reactor design. Small compositional non-uniformity (±2% absolute) in In1-xGaxP layers grown in our reactor was correlated with calculated temperature non-uniformity across the substrate. Gas switching was modeled and the transient time predicted by the model was confirmed by measurement of doping transients in a sample grown in the reactor. Lastly the gas curtains that chemically isolate the reactor chambers were modeled and the results were compared to experimental data for cross doping between the chambers. As an example, we demonstrate, based on insight from the model, that our HVPE reactor is suitable for the deposition of GaAs PV devices. CFD modeling is a critical tool for the scale up of laboratory level processes to industrial levels.

  14. Heterocyclic aromatic amines and their contribution to the bacterial mutagenicity of the particulate phase of cigarette smoke.

    PubMed

    Roemer, Ewald; Meisgen, Thomas; Diekmann, Joerg; Conroy, Lynda; Stabbert, Regina

    2016-01-22

    Heterocyclic aromatic amines (HAAs) rank among the strongest known mutagens. Approximately 30 HAAs have been found in cooked foods (broiled, fried, and grilled) and several HAAs have been characterized as animal carcinogens. Nine HAAs have also been reported to be constituents of cigarette smoke (CS) raising concerns that HAAs might contribute significantly to the known carcinogenicity of CS. As HAAs are found predominantly in the total particulate matter (TPM) of CS, an improved method for the quantification of HAAs in TPM is reported allowing detection and quantification of 8 HAAs in a single run. The mutagenic potency of these HAAs and that of TPM from the reference cigarette 2R4F was determined in the Salmonella Reverse Mutation Assay (Ames assay) with tester strain TA98 and a metabolic activation system. The 8 HAAs, when applied together in the Ames assay, showed a clear sub-additive response. Likewise, the combination of HAAs and TPM, if at all, gave rise to a slight sub-additive response. In both cases, however, the sub-additive response in the Ames assay was observed at HAA doses that are far above the amounts found in CS. The contribution of the individual HAAs to the total mutagenic activity of TPM was calculated and experimentally confirmed to be approximately 1% of the total mutagenic activity. Thus, HAAs do not contribute significantly to the bacterial in vitro mutagenicity of CS TPM. PMID:26724587

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

    PubMed

    Peng, Hao; Ding, Guoliang; Hu, Haitao

    2011-01-01

    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 kWm-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

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

    PubMed Central

    2011-01-01

    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 μm 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

  17. Tank vapor sampling and analysis data package for tank 241-C-106 waste retrieval sluicing system process test phase III

    SciTech Connect

    LOCKREM, L.L.

    1999-08-13

    This data package presents sampling data and analytical results from the March 28, 1999, vapor sampling of Hanford Site single-shell tank 241-C-106 during active sluicing. Samples were obtained from the 296-C-006 ventilation system stack and ambient air at several locations. Characterization Project Operations (CPO) was responsible for the collection of all SUMMATM canister samples. The Special Analytical Support (SAS) vapor team was responsible for the collection of all triple sorbent trap (TST), sorbent tube train (STT), polyurethane foam (PUF), and particulate filter samples collected at the 296-C-006 stack. The SAS vapor team used the non-electrical vapor sampling (NEVS) system to collect samples of the air, gases, and vapors from the 296-C-006 stack. The SAS vapor team collected and analyzed these samples for Lockheed Martin Hanford Corporation (LMHC) and Tank Waste Remediation System (TWRS) in accordance with the sampling and analytical requirements specified in the Waste Retrieval Sluicing System Vapor Sampling and Analysis Plan (SAP) for Evaluation of Organic Emissions, Process Test Phase III, HNF-4212, Rev. 0-A, (LMHC, 1999). All samples were stored in a secured Radioactive Materials Area (RMA) until the samples were radiologically released and received by SAS for analysis. The Waste Sampling and Characterization Facility (WSCF) performed the radiological analyses. The samples were received on April 5, 1999.

  18. The Effect Of ZnO Addition On Co/C Catalyst For Vapor And Aqueous Phase Reforming Of Ethanol

    SciTech Connect

    Davidson, Stephen; Sun, Junming; Hong, Yongchun; Karim, Ayman M.; Datye, Abhaya K.; Wang, Yong

    2014-02-05

    The effect of ZnO addition on the oxidation behavior of Co along with catalytic performance in vapor and aqueous phase reforming of ethanol were investigated on Co supported on carbon black (XC-72R). Carbon was selected to minimize the support interactions. Effect of ZnO addition during both vapor and aqueous phase reforming were compared at 250 C. ZnO addition inhibited the reduction of cobalt oxides by H2 and created surface sites for H2O activation. During vapor phase reforming at 450 C the redox of cobalt, driven by steam oxidation and H2 reduction, trended to an equilibrium of Co0/Co2+. ZnO showed no significant effect on cobalt oxidation, inferred from the minor changes of C1 product yield. Surface sites created by ZnO addition enhanced water activation and oxidation of surface carbon species, increasing CO2 selectivity. At 250 C cobalt reduction was minimal, in situ XANES demonstrated that ZnO addition significantly facilitated oxidation of Co0 under vapor phase reforming conditions, demonstrated by lower C1 product yield. Sites introduced by ZnO addition improved the COx selectivity at 250 C. Both Co/C and Co-ZnO/C rapidly oxidized under aqueous phase reaction conditions at 250 C, showing negligible activity in aqueous phase reforming. This work suggests that ZnO affects the activation of H2O for Co catalysts in ethanol reforming.

  19. Vapor phase ketonization of acetic acid on ceria based metal oxides

    SciTech Connect

    Liu, Changjun; Karim, Ayman M.; Lebarbier, Vanessa MC; Mei, Donghai; Wang, Yong

    2013-12-01

    The activities of CeO2, Mn2O3-CeO2 and ZrO2-CeO2 were measured for acetic acid ketonization under reaction conditions relevant to pyrolysis vapor upgrading. We show that the catalyst ranking changed depending on the reaction conditions. Mn2O3-CeO2 was the most active catalyst at 350 oC, while ZrO2 - CeO2 was the most active catalyst at 450 oC. Under high CO2 and steam concentration in the reactants, Mn2O3-CeO2 was the most active catalyst at 350 and 450 °C. The binding energies of steam and CO2 with the active phase were calculated to provide the insight into the tolerance of Mn2O3-CeO2 to steam and CO2.

  20. Evidence for Family-Meakin dynamical scaling in island growth and coalescence during vapor phase deposition.

    PubMed

    Arslan, Leyla Colakerol; Sanborn, Christopher; Anzenberg, Eitan; Ludwig, Karl F

    2012-09-01

    Using real-time grazing-incidence small-angle x-ray scattering, we find that the processes of island formation and coalescence during the room-temperature vapor phase deposition of aluminum lead to dynamical scaling of the evolving surface morphology. The scaling is quantitatively consistent with the self-similarity predicted by the Family-Meakin model, which was developed to describe liquid droplet deposition, growth, and coalescence. The Family-Meakin model assumes only that atomic diffusion over the substrate between islands or droplets is negligible and that diffusion between impinging islands or droplets is sufficient to give complete coalescence. Therefore the dynamical scaling morphology evolution identified here may be common in the initial stages of those solid film growth processes which proceed by island formation and growth. PMID:23005305

  1. Synthesis, characterization of WS{sub 2} nanostructures by vapor phase deposition

    SciTech Connect

    Fan, Yinping; Li, Jun; Luo, Siwei; Tang, Chao; Zhong, Jianxin E-mail: jxzhong@xtu.edu.cn; Hao, Guolin E-mail: jxzhong@xtu.edu.cn

    2015-02-14

    Ultrathin two-dimensional WS{sub 2} nanostructures with various morphologies have been prepared on SiO{sub 2}/Si (300?nm) and sapphire substrates by vapor phase deposition method. Simultaneously, tungsten nanostructures have also been obtained during the growth process. The nanostructures and morphologies of as-prepared products were systematically characterized by employing atomic force microscopy, Raman spectroscopy as well as scanning electron spectroscopy. The electrostatic properties of WS{sub 2} nanostructures were investigated exhibiting uniform surface potential and charge distributions. We have also detected the photoluminescence properties of WS{sub 2} nanostructures, which are dependent on the thickness and nanostructures of synthesized WS{sub 2}. These results suggest that the optoelectronic properties of WS{sub 2} nanostructures can be effectively tuned by quantum confinement effect and nanostructures.

  2. A procedure for testing the effect of vapor phase corrosion inhibitors on combined multi metals

    SciTech Connect

    Kraemer, C.

    1997-08-01

    This study presents a quick and easy to implement Vapor Phase Corrosion Inhibitor (VCI) testing procedure which is capable of validating the protective effects of VCI foils in connection with various, electrically conductive, connected metals. Furthermore it may be used to demonstrate the effects of VCI for potential customers. The test procedure demonstrates various approaches as to how deficiencies in existing test procedures can be avoided with regards to the practice orientation--the temporary corrosion protection of machines. It also points out the lack of alignment of existing test procedures to meet the demands of new VCI recipes. The considerations made during the development of the test procedure are explained in this study with regards to their effects on the VCI protective influence.

  3. Origin of lattice bowing of freestanding GaN substrates grown by hydride vapor phase epitaxy

    NASA Astrophysics Data System (ADS)

    Yamane, Keisuke; Matsubara, Tohoru; Yamamoto, Takeshi; Okada, Narihito; Wakahara, Akihiro; Tadatomo, Kazuyuki

    2016-01-01

    This paper describes a mechanism to explain the lattice bowing of freestanding GaN substrates grown by hydride vapor phase epitaxy on sapphire substrates. The freestanding GaN substrates typically exhibit a concave shape. It is revealed that the radius of curvature and lattice constant of the top surface are almost the same as those of the bottom surface. This is indicative of the complete relaxation of the GaN lattice, even though the freestanding GaN substrate exhibited a curvature. It is shown that dislocations are present in a plane normal to the growth direction in addition to conventionally known threading dislocations; these are referred to as in-plane dislocations. Based on these results, it is proven quantitatively that the extra-half planes related to the in-plane dislocations are primarily responsible for the phenomenon of lattice bowing.

  4. An Assessment of the Technical Readiness of the Vapor Phase Catalytic Ammonia Removal Process (VPCAR) Technology

    NASA Technical Reports Server (NTRS)

    Flynn, Michael

    2000-01-01

    This poster provides an assessment of the technical readiness of the Vapor Phase Catalytic Ammonia Removal Process (VPCAR). The VPCAR technology is a fully regenerative water recycling technology designed specifically for applications such as a near term Mars exploration mission. The VPCAR technology is a highly integrated distillation/catalytic oxidation based water processor. It is designed to accept a combined wastewater stream (urine, condensate, and hygiene) and produces potable water in a single process step which requires -no regularly scheduled re-supply or maintenance for a 3 year mission. The technology is designed to be modular and to fit into a volume comparable to a single International Space Station Rack (when sized for a crew of 6). This poster provides a description of the VPCAR technology and a summary of the current performance of the technology. Also provided are the results of two separate NASA sponsored system trade studies which investigated the potential payback of further development of the VPCAR technology.

  5. Heterojunction Hybrid Devices from Vapor Phase Grown MoS2

    PubMed Central

    Yim, Chanyoung; O'Brien, Maria; McEvoy, Niall; Riazimehr, Sarah; Schäfer-Eberwein, Heiko; Bablich, Andreas; Pawar, Ravinder; Iannaccone, Giuseppe; Downing, Clive; Fiori, Gianluca; Lemme, Max C.; Duesberg, Georg S.

    2014-01-01

    We investigate a vertically-stacked hybrid photodiode consisting of a thin n-type molybdenum disulfide (MoS2) layer transferred onto p-type silicon. The fabrication is scalable as the MoS2 is grown by a controlled and tunable vapor phase sulfurization process. The obtained large-scale p-n heterojunction diodes exhibit notable photoconductivity which can be tuned by modifying the thickness of the MoS2 layer. The diodes have a broad spectral response due to direct and indirect band transitions of the nanoscale MoS2. Further, we observe a blue-shift of the spectral response into the visible range. The results are a significant step towards scalable fabrication of vertical devices from two-dimensional materials and constitute a new paradigm for materials engineering. PMID:24975741

  6. High-resolution discrete absorption spectrum of α-methallyl free radical in the vapor phase

    NASA Astrophysics Data System (ADS)

    Bayrakçeken, Fuat; Telatar, Ziya; Arı, Fikret; Tunçyürek, Lale; Karaaslan, İpek; Yaman, Ali

    2006-09-01

    The α-methallyl free radical is formed in the flash photolysis of 3-methylbut-1-ene, and cis-pent-2-ene in the vapor phase, and then subsequent reactions have been investigated by kinetic spectroscopy and gas-liquid chromatography. The photolysis flash was of short duration and it was possible to follow the kinetics of the radicals' decay, which occurred predominantly by bimolecular recombination. The measured rate constant for the α-methallyl recombination was (3.5 ± 0.3) × 10 10 mol -1 l s -1 at 295 ± 2 K. The absolute extinction coefficients of the α-methallyl radical are calculated from the optical densities of the absorption bands. Detailed analysis of related absorption bands and lifetime measurements in the original α-methallyl high-resolution discrete absorption spectrum image were also carried out by image processing techniques.

  7. Nonpolar GaN grown on Si by hydride vapor phase epitaxy using anodized Al nanomask

    NASA Astrophysics Data System (ADS)

    Polyakov, A. Y.; Markov, A. V.; Mezhennyi, M. V.; Govorkov, A. V.; Pavlov, V. F.; Smirnov, N. B.; Donskov, A. A.; D'yakonov, L. I.; Kozlova, Y. P.; Malakhov, S. S.; Yugova, T. G.; Osinsky, V. I.; Gorokh, G. G.; Lyahova, N. N.; Mityukhlyaev, V. B.; Pearton, S. J.

    2009-01-01

    GaN growth by the hydride vapor phase technique on (100) Si substrates masked by porous Al anodic oxide is described. The masks were prepared by vacuum deposition of Al with subsequent anodic oxidation in dilute sorrel acid. The grown GaN layer is nonpolar, with (1120) a-orientation and a full width at half maximum of the (1120) reflection below 500 arc sec and showing small anisotropy. This result is comparable with the results obtained for a-GaN growth using selective epitaxy or advanced buffer growth routines. Microcathodoluminescence spectra of the grown films confirm a low density of stacking faults. Possible growth mechanisms are discussed.

  8. Spectroscopic ellipsometry during metalorganic vapor phase epitaxy of InN

    NASA Astrophysics Data System (ADS)

    Schmidtling, T.; Drago, M.; Pohl, U. W.; Richter, W.

    2003-02-01

    Metalorganic vapor phase epitaxy of indium nitride (InN) on sapphire was studied and optimized in situ by spectroscopic ellipsometry. Layers with smooth surface morphology were obtained on low-temperature nucleation layers on nitrided sapphire substrates using trimethylindium and ammonia at high V/III ratios above 30 000. Ellipsometry reveals a growth regime for InN below 550C and best crystalline quality at 500C. Improvement of the crystalline quality is achieved at lower growth temperatures. This tendency is confirmed by X-ray diffraction while still some residual mosaicity of the layers can be observed. The appearance of pronounced E 1 and A 2 Raman modes, obeying the selection rules of hexagonal InN, confirms the good structural quality of the samples grown.

  9. Detection of condensed-phase explosives via laser-induced vaporization, photodissociation, and resonant excitation.

    PubMed

    Wynn, C M; Palmacci, S; Kunz, R R; Clow, K; Rothschild, M

    2008-11-01

    We investigate the remote detection of explosives via a technique that vaporizes and photodissociates the condensed-phase material and detects the resulting vibrationally excited NO fragments via laser-induced fluorescence. The technique utilizes a single 7 ns pulse of a tunable laser near 236.2 nm to perform these multiple processes. The resulting blue-shifted fluorescence (226 nm) is detected using a photomultiplier and narrowband filter that strongly block the scatter of the pump laser off the solid media while passing the shorter wavelength photons. Various nitro-bearing compounds, including 2,6-dinitrotoluene (DNT), 2,4,6-trinitrotoluene (TNT), pentaerythritol tetranitrate (PETN), and hexahydro-1,3,5-trinitro-1,3,5-triazine (RDX) were detected with a signal-to-noise of 25 dB. The effects of laser fluence, wavelength, and sample morphology were examined. PMID:19122718

  10. Growth of vertical-cavity surface emitting lasers by metalorganic vapor phase epitaxy

    SciTech Connect

    Hou, H.Q.; Hammons, B.E.; Crawford, M.H.; Lear, K.L.; Choquette, K.D.

    1996-10-01

    We present growth and characterization of visible and near-infrared vertical-cavity surface emitting lasers (VCSELs) grown by metalorganic vapor phase epitaxy. Discussions on the growth issue of VCSEL materials include growth rate and composition control using an {ital in}{ital situ} normal-incidence reflectometer, comprehensive p- and n-type doping study in AlGaAs by CCl{sub 4} and Si{sub 2}H{sub 6} over the entire composition range, and optimization of ultra-high material uniformity. We also demonstrate our recent achievements of all-AlGaAs VCSELs which include the first room-temperature continuous- wave demonstration of 700-nm red VCSELs and high-efficiency and low- threshold voltage 850-nm VCSELs.

  11. Study of near-critical states of liquid-vapor phase transition of magnesium

    NASA Astrophysics Data System (ADS)

    Emelyanov, A. N.; Shakhray, D. V.; Golyshev, A. A.

    2015-11-01

    Study of thermodynamic parameters of magnesium in the near-critical point region of the liquid-vapor phase transition and in the region of metal-nonmetal transition was carried out. Measurements of the electrical resistance of magnesium after shock compression and expansion into gas (helium) environment in the process of isobaric heating was carried out. Heating of the magnesium surface by heat transfer with hot helium was performed. The registered electrical resistance of expanded magnesium was about 104-105 times lower than the electrical resistance of the magnesium under normal condition at the density less than the density of the critical point. Thus, metal-nonmetal transition was found in magnesium.

  12. Hydride vapor phase GaN films with reduced density of residual electrons and deep traps

    SciTech Connect

    Polyakov, A. Y.; Smirnov, N. B.; Govorkov, A. V.; Yugova, T. G.; Cox, H.; Helava, H.; Makarov, Yu.; Usikov, A. S.

    2014-05-14

    Electrical properties and deep electron and hole traps spectra are compared for undoped n-GaN films grown by hydride vapor phase epitaxy (HVPE) in the regular process (standard HVPE samples) and in HVPE process optimized for decreasing the concentration of residual donor impurities (improved HVPE samples). It is shown that the residual donor density can be reduced by optimization from ?10{sup 17}?cm{sup ?3} to (25)??10{sup 14}?cm{sup ?3}. The density of deep hole traps and deep electron traps decreases with decreased donor density, so that the concentration of deep hole traps in the improved samples is reduced to ?5??10{sup 13}?cm{sup ?3} versus 2.9??10{sup 16}?cm{sup ?3} in the standard samples, with a similar decrease in the electron traps concentration.

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

    SciTech Connect

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

    1988-10-03

    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.

  14. A three-dimensional phase field model for nanowire growth by the vapor-liquid-solid mechanism

    NASA Astrophysics Data System (ADS)

    Wang, Yanming; Ryu, Seunghwa; McIntyre, Paul C.; Cai, Wei

    2014-07-01

    We present a three-dimensional multi-phase field model for catalyzed nanowire (NW) growth by the vapor-liquid-solid (VLS) mechanism. The equation of motion contains both a Ginzburg-Landau term for deposition and a diffusion (Cahn-Hilliard) term for interface relaxation without deposition. Direct deposition from vapor to solid, which competes with NW crystal growth through the molten catalyst droplet, is suppressed by assigning a very small kinetic coefficient at the solid-vapor interface. The thermodynamic self-consistency of the model is demonstrated by its ability to reproduce the equilibrium contact angles at the VLS junction. The incorporation of orientation dependent gradient energy leads to faceting of the solid-liquid and solid-vapor interfaces. The model successfully captures the curved shape of the NW base and the Gibbs-Thomson effect on growth velocity.

  15. APTS and rGO co-functionalized pyrenated fluorescent nanonets for representative vapor phase nitroaromatic explosive detection.

    PubMed

    Guo, Linjuan; Zu, Baiyi; Yang, Zheng; Cao, Hongyu; Zheng, Xuefang; Dou, Xincun

    2014-01-01

    For the first time, flexible PVP/pyrene/APTS/rGO fluorescent nanonets were designed and synthesized via a one-step electrospinning method to detect representative subsaturated nitroaromatic explosive vapor. The functional fluorescent nanonets, which were highly stable in air, showed an 81% quenching efficiency towards TNT vapor (?10 ppb) with an exposure time of 540 s at room temperature. The nice performance of the nanonets was ascribed to the synergistic effects induced by the specific adsorption properties of APTS, the fast charge transfer properties and the effective ?-? interaction with pyrene and TNT of rGO. Compared to the analogues of TNT, the PVP/pyrene/APTS/rGO nanonets showed notable selectivity towards TNT and DNT vapors. The explored functionalization method opens up brand new insight into sensitive and selective detection of vapor phase nitroaromatic explosives. PMID:24316887

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

    SciTech Connect

    Lynn E. Katz; Kerry A. Kinney; R. S. Bowman; E. J. Sullivan

    2004-03-11

    This report summarizes work of this project from October 2003 through March 2004. The major focus of the research was to further investigate BTEX removal from produced water, to quantify metal ion removal from produced water, and to evaluate a lab-scale vapor phase bioreactor (VPB) for BTEX destruction in off-gases produced during SMZ regeneration. Batch equilibrium sorption studies were conducted to evaluate the effect of semi-volatile organic compounds commonly found in produced water on the sorption of benzene, toluene, ethylbenzene, and xylene (BTEX) onto surfactant-modified zeolite (SMZ) and to examine selected metal ion sorption onto SMZ. The sorption of polar semi-volatile organic compounds and metals commonly found in produced water onto SMZ was also investigated. Batch experiments were performed in a synthetic saline solution that mimicked water from a produced water collection facility in Wyoming. Results indicated that increasing concentrations of semi-volatile organic compounds increased BTEX sorption. The sorption of phenol compounds could be described by linear isotherms, but the linear partitioning coefficients decreased with increasing pH, especially above the pKa's of the compounds. Linear correlations relating partitioning coefficients of phenol compounds with their respective solubilities and octanol-water partitioning coefficients were developed for data collected at pH 7.2. The sorption of chromate, selenate, and barium in synthetic produced water were also described by Langmuir isotherms. Experiments conducted with a lab-scale vapor phase bioreactor (VPB) packed with foam indicated that this system could achieve high BTEX removal efficiencies once the nutrient delivery system was optimized. The xylene isomers and benzene were found to require the greatest biofilter bed depth for removal. This result suggested that these VOCs would ultimately control the size of the biofilter required for the produced water application. The biofilter recovered rapidly from shutdowns showing that the system was resilient to discontinuous feed conditions therefore provided flexibility on the SMZ regeneration process.

  17. Vapor-phase epitaxy of gallium nitride by gallium arc discharge evaporation

    NASA Astrophysics Data System (ADS)

    Heikman, S.; Keller, S.; Mishra, U. K.

    2006-08-01

    Vapor-phase epitaxy of GaN was performed by combining ammonia with gallium evaporated into an inert gas stream by a DC arc discharge, and letting the mixture pass through a pair of heated graphite susceptors. Growth rates as high as 30 ?m/h were achieved. The growth on the top sample was specular in a large area, and was of high quality as characterized by atomic force microscopy and photoluminescence spectroscopy. The bottom sample had a high density of macroscopic defects, presumably caused by Ga droplets in the gas phase resulting from the arc evaporation process. The experimental growth rate was found to be less than {1}/{3} of values predicted in a computer flow dynamic model of the growth system, and Ga-NH 3 pre-reactions were implicated as the likely cause of the discrepancy. The growth efficiency, calculated to 2%, could arguably be improved by reducing the reactor growth pressure, and by changing the reactor geometry to avoid Ga condensation on walls. Potential advantages of the described growth technique are cheap source materials of high purity and low equipment costs. Furthermore, since no corrosive gasses were used, hardware corrosion and gas-phase impurities can be reduced.

  18. Electronic cigarettes: the road ahead.

    PubMed

    Besaratinia, Ahmad; Tommasi, Stella

    2014-09-01

    Electronic cigarettes (e-cig) are proliferating in the world's lucrative nicotine delivery market at an alarmingly fast pace. E-cig are aggressively marketed as an alternative to conventional tobacco cigarettes, although very little is known about the health consequences of e-cig use. Chemical analysis of e-cig vapor/liquid has shown that many toxicants and carcinogens present in cigarette smoke are also found, albeit generally in lower concentrations, in a wide range of e-cig products. Notwithstanding the presence of toxicants and carcinogens in e-cig products, the biological effects of exposure to these contaminants have not been determined in e-cig users. The ongoing research and future investigations on e-cig initiation, use, perceptions, dependence, and toxicity are expected to provide empirical evidence that can be used to inform the general public, scientific community, and regulatory authorities of the health risks/benefits associated with e-cig use. This information will help stimulate scientists in the field of tobacco research, as well as assist the regulatory agencies in making scientifically based decisions on the development and evaluation of regulations on tobacco products to protect the public's health. Finding the scientific underpinnings for the health risks/benefits of e-cig use can impact millions of people who are increasingly turning to e-cig as a replacement for or complement to conventional tobacco cigarettes. PMID:24952095

  19. A NEW VAPOR RECOVERY NOZZLE FOR AIR POLLUTION CONTROL - PHASE II

    EPA Science Inventory

    The vapor recovery nozzle is an air pollution control device which relates to Stage II emission control equipment designed to capture gasoline vapors during automobile refueling at service stations. The existing vapor recovery nozzles are difficult to handle, the bellows pr...

  20. Gas-Phase Nucleation in GaAs Thin Film Preparation by Metal Organic Chemical Vapor Deposition

    NASA Astrophysics Data System (ADS)

    Okuyama, Kikuo; Huang, David D.; Seinfeld, John H.; Tani, Naoyuki; Matsui, Isao

    1992-01-01

    GaAs epitaxial film growth in the metal organic chemical vapor deposition (MOCVD) horizontal reactor was analyzed by a mathematical model, which takes into consideration of vapor phase hydrodynamic and kinetic phenomena including decomposition reactions of reactants, Ga or GaAs nucleation and subsequent particle growth. The position dependent changes in mass concentrations of Ga or GaAs monomers and homogeneously nucleated Ga or GaAs particles are predicted under various substrate temperatures. The appearance of particles in the gas phase is found to be enhanced under substrate temperature exceeding about 900 K. The conditions under which the growth of the thin film is governed by the diffusive deposition of metal organic vapor and Ga monomers are determined, and the effect of homogeneously nucleated particles on the growth of thin film has been clarified. The simulation results are in good agreement with the data of van de Ven et al [J. Cryst. Growth 76 (1986) 352].

  1. Method for the generation of variable density metal vapors which bypasses the liquidus phase

    DOEpatents

    Kunnmann, Walter (Stony Brook, NY); Larese, John Z. (Rocky Point, NY)

    2001-01-01

    The present invention provides a method for producing a metal vapor that includes the steps of combining a metal and graphite in a vessel to form a mixture; heating the mixture to a first temperature in an argon gas atmosphere to form a metal carbide; maintaining the first temperature for a period of time; heating the metal carbide to a second temperature to form a metal vapor; withdrawing the metal vapor and the argon gas from the vessel; and separating the metal vapor from the argon gas. Metal vapors made using this method can be used to produce uniform powders of the metal oxide that have narrow size distribution and high purity.

  2. Defect Analysis in III-V Semiconductor Thin Films Grown by Hydride Vapor Phase Epitaxy

    NASA Astrophysics Data System (ADS)

    Schulte, Kevin Louis

    Hydride vapor phase epitaxy (HVPE) is an epitaxial growth technique renowned for its ability to grow III-V semiconductors at high growth rates using lower cost reagents compared to metal-organic vapor phase epitaxy (MOVPE), the current industry standard. Recent interest in III-V photovoltaics has led to increased attention on HVPE. While the technique came to maturity in the 70s, much is unknown about how defects incorporate in HVPE-grown materials. Further understanding of how defects incorporate in III-V materials grown by HVPE is necessary to facilitate wider adoption of the technique. This information would inform strategies for minimizing and eliminating defects in HVPE materials, allowing for the formation of high performance devices. This investigation presents a study of multiple defects in III-V semiconductors grown by HVPE in the context of specific device applications, spanning point defects comprised of individual atoms to extended defects which propagate throughout the crystal. The incorporation of the arsenic anti-site defect, AsGa, intrinsic point defect was studied in high growth rate GaAs layers with potential photovoltaic applications. Relationships between growth conditions and incorporation of AsGa in GaAs epilayers were determined. The incorporation of AsGa depended strongly on the growth conditions employed, and a model was developed to predict the concentration of anti-site defects as a function of those growth conditions. Dislocations and anti-phase domain boundaries (APDBs), two types of extended defects, were investigated in the heteroepitaxial GaAs/Ge system. It was found that the use of 6 miscut substrates and specific growth temperatures led to elimination of APDBs. Dislocation densities were reduced through the use of high growth temperatures. The third and final application investigated was the growth of InxGa1-xAs metamorphic buffer layers (MBLs) by HVPE. The relationships between the growth conditions and the alloy composition were determined, and a model was developed to explain the observed behavior. Compositional grading strategies were explored and insight into the minimization of dislocations in these layers was developed. The dislocation microstructure was analyzed by TEM and related to the layer design, leading to the development of an atomic scale model for dislocation nucleation and propagation throughout the MBL layers.

  3. Shadow masked organometallic vapor phase epitaxy for advanced micro-optical structures

    NASA Astrophysics Data System (ADS)

    Peake, Gregory Merwin

    2000-12-01

    This thesis presents novel techniques and applications of nonplanar chemical vapor deposition (CVD) for optoelectronic materials and devices. Specifically, nonplanar organometallic vapor phase epitaxy (OMVPE) employing a shadow mask has been developed for the fabrication of integrated optoelectronic structures. Shadow masked OMVPE (SM-OMVPE) is currently the only technique known to produce thick, nonplanar layers of single crystal material without macroscopic faceting. By the use of SM-OMVPE, various microlenses, micromirrors and novel devices have been designed fabricated and tested. Shadow masked microlenses with record short focal lengths have been produced. High quality microlens arrays with accurate control of lens diameter, sagitta, focal length, astigmatism and position have been designed, fabricated and tested. The author has shown that precise three-dimensional control during crystal growth can be employed to construct useful optoelectronic structures in a reproducible manner. This work also presents novel techniques for the fabrication of shadow masks. A high aluminum- concentration spacer layer and chemical recipes for the removal of epitaxial shadow masks are reported. In addition, the first reusable shadow mask constructed by reactive ion etching has been utilized for the growth of shadow masked structures. Direct fusion wafer bonding of silicon shadow masks was first developed by the author and has proven to be a robust, clean and reliable technique for mask placement. The application of shadow masked growth to vertical cavity semiconductor lasers (VCSELs) was initiated in this work. Microlenses were designed for top-emitting VCSELs to provide focusing of the output beam and these designs are currently being fabricated at Sandia National Laboratories. Furthermore, by introducing curvature to the distributed Bragg reflector (DBR) mirrors, a high power single mode VCSEL has been designed. The author has grown the first concentrically-variable semiconductor Bragg reflector, the initial requirement for fabrication of this device.

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

    Technology Transfer Automated Retrieval System (TEKTRAN)

    Salmonella contamination of raw shrimp is a food safety concern in the U.S. and other countries. This research evaluated the 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),...

  5. An evaluation of the vapor phase catalytic ammonia removal process for use in a Mars transit vehicle.

    PubMed

    Flynn, M; Borchers, B

    1998-01-01

    This article describes the design specification of the Vapor Phase Catalytic Ammonia Removal (VPCAR) process and the relative benefits of its utilization in a Mars Transit Vehicle application. The VPCAR process is a wastewater treatment technology that combines distillation with high-temperature catalytic oxidation of volatile impurities such as ammonia and organic compounds. PMID:11871448

  6. 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...

  7. OM-VPE growth of Mg-doped GaAs. [OrganoMetallic-Vapor Phase Epitaxy

    NASA Technical Reports Server (NTRS)

    Lewis, C. R.; Dietze, W. T.; Ludowise, M. J.

    1982-01-01

    The epitaxial growth of Mg-doped GaAs by the organometallic vapor phase epitaxial process (OM-VPE) has been achieved for the first time. The doping is controllable over a wide range of input fluxes of bis (cyclopentadienyl) magnesium, (C5H5)2Mg, the organometallic precursor to Mg.

  8. Reduced exposure evaluation of an Electrically Heated Cigarette Smoking System. Part 2: Smoke chemistry and in vitro toxicological evaluation using smoking regimens reflecting human puffing behavior.

    PubMed

    Zenzen, Volker; Diekmann, Joerg; Gerstenberg, Birgit; Weber, Susanne; Wittke, Sandra; Schorp, Matthias K

    2012-11-01

    Chemical analysis of up to 49 harmful and potentially harmful constituents (HPHC) in mainstream smoke, in vitro cytotoxicity of the particulate and gas/vapor phase of mainstream smoke determined in the Neutral Red Uptake assay, and in vitro bacterial mutagenicity of the particulate phase determined in the Salmonella typhimurium Reverse Mutation (Ames) assay are reported for three Electrically Heated Cigarette Smoking System (EHCSS) series-K cigarettes, the University of Kentucky Reference Cigarette 2R4F, and a number of comparator commercial conventional lit-end cigarettes (CC) under ISO machine-smoking conditions and a total of 25 additional smoking regimens reflecting 'human puffing behavior' (HPB). The smoking machines were set to deliver nicotine yields for the EHCSS and comparator CC derived from the 10th percentile to the 90th percentile of nicotine uptake distributions in smokers determined in two clinical studies. Duplication of the smoking intensity 'per cigarette' on a smoking machine may provide an insight into product performance that is directly relevant to obtaining scientific evidence for reduced exposure substantiation based on mainstream cigarette smoke HPHC-to-nicotine regressions. The reported data support an overall evaluation of reduced exposure to HPHC and biological activity. PMID:22922180

  9. Phase Transition Enthalpy Measurements of Organic and Organometallic Compounds. Sublimation, Vaporization and Fusion Enthalpies From 1880 to 2010

    NASA Astrophysics Data System (ADS)

    Acree, William; Chickos, James S.

    2010-12-01

    A compendium of phase change enthalpies published within the period 1880-2010 is reported. Phase change enthalpies including fusion, vaporization, and sublimation are included for organic, organometallic, and a few inorganic compounds. This compendium is a combination of three previous series focusing on phase change enthalpies updated to 2009. Sufficient data are presently available for some compounds to permit thermodynamic cycles to be constructed, an important manner of evaluating the reliability of the measurements. Temperature adjustments of phase change enthalpies from the temperature of measurement to the standard reference temperature, T=298.15 K, are briefly discussed and a protocol for doing so is illustrated.

  10. m-Plane Homoepitaxy and Equilibrium Crystal Shapes of Gallium Nitride by Hydride Vapor Phase Epitaxy

    NASA Astrophysics Data System (ADS)

    Bryant, Benjamin Nathaniel

    Nonpolar and semipolar growth of GaN has been shown to offer a promising path for high performance devices. These non-basal plane orientations allow for minimization of the polarization effects seen in c-plane GaN which cause spatial separation of the electron and hole wavefunctions (Quantum Confined Stark Effect). Yet despite the advantages these planes present, there remains consistent problems in both their growth and the lack of substrates. This dissertation focuses on the growth of these nonpolar and semipolar planes, in particular the homoepitaxy of m-plane GaN. The equilibrium crystal shape of GaN and its stable facets were also investigated. It is hoped that with this work, progress is made towards low defect large area nonpolar and semipolar substrates and their improved vapor phase growth. Work was initially done on m-plane regrowth by hydride vapor phase epitaxy. Extended defect generation, in particular basal plane stacking faults (BPSF), and poor morphology control are consistent problems in m-plane growth. These issues have prevented the expansion and multiplication of m-plane GaN substrates. In this work the effects of carrier gas were investigated on m-plane regrowth. Hydrogen carrier gas was shown to create highly faceted 3D nucleation. These islands had exposed N-face facets which lead to BPSF generation. In contrast, nitrogen carrier gas lead to 2D growth and thus minimized BPSF generation. These stacking faults were then characterized by both reciprocal space mapping and cathodolumienscence where type I1 and I2 faults were observed in the regrown GaN. Further work was done in exploring the equilibrium crystal shapes of GaN under varying growth conditions. Selective area growth experiments were done on high quality bulk m-plane GaN substrates where GaN facets were exposed to show the stable polar, semipolar and nonpolar planes. From these facets the kinetic Wulff plots for GaN were constructed. This work highlights the stable growth conditions for nonpolar and semipolar GaN and leads to improved growth conditions. AlN growth by HVPE is also investigated in this dissertation with work being done on thick AlN growth on patterned sapphire substrates (PSS). These templates were made for the purpose of substrates for UV LEDs.

  11. Experimental studies of the vapor phase nucleation of refractory compounds. VI. The condensation of sodium.

    PubMed

    Martnez, Daniel M; Ferguson, Frank T; Heist, Richard H; Nuth, Joseph A

    2005-08-01

    In this paper we discuss the condensation of sodium vapor and the formation of a sodium aerosol as it occurs in a gas evaporation condensation chamber. A one-dimensional model describing the vapor transport to the vapor/aerosol interface was employed to determine the onset supersaturation, in which we assume the observed location of the interface is coincident with a nucleation rate maximum. We then present and discuss the resulting nucleation onset supersaturation data within the context of nucleation theory based on the liquid droplet model. Nucleation results appear to be consistent with a cesium vapor-to-liquid nucleation study performed in a thermal diffusion cloud chamber. PMID:16108655

  12. Molecular dynamics study of kinetic boundary condition at an interface between a polyatomic vapor and its condensed phase

    NASA Astrophysics Data System (ADS)

    Ishiyama, Tatsuya; Yano, Takeru; Fujikawa, Shigeo

    2004-12-01

    The kinetic boundary condition for the Boltzmann equation at an interface between a polyatomic vapor and its liquid phase is investigated by the numerical method of molecular dynamics, with particular emphasis on the functional form of the evaporation part of the boundary condition, including the evaporation coefficient. The present study is an extension of a previous one for argon [Ishiyama, Yano, and Fujikawa, Phys. Fluids 16, 2899 (2004)] to water and methanol, typical examples of polyatomic molecules. As in the previous study, molecular dynamics simulations of vapor-liquid equilibrium states and those of evaporation from liquid into a virtual vacuum are carried out for water and methanol. In spite of the formation of molecular clusters in the vapor phase and the presence of the preferential orientation of molecules at the interface, essentially the same results as in the previous study are obtained. When the bulk liquid temperature is relatively low, the evaporation part is the product of the half range Maxwellian for the translational velocity of molecules of saturated vapor at the temperature of the bulk liquid phase, the equilibrium distribution of rotational energy of molecules at the temperature, and the evaporation coefficient (or the condensation coefficient in the equilibrium state). The evaporation coefficients of water and methanol are determined without any ambiguity as decreasing functions of the temperature, and are found to approach unity with the decrease of the temperature.

  13. Solgel synthesis of MCM-41 silicas and selective vapor-phase modification of their surface

    SciTech Connect

    Roik, N.V. Belyakova, L.A.

    2013-11-15

    Silica particles with uniform hexagonal mesopore architecture were synthesized by template directed solgel condensation of tetraethoxysilane or mixture of tetraethoxysilane and (3-chloropropyl)triethoxysilane in a waterethanolammonia solution. Selective functionalization of exterior surface of parent materials was carried out by postsynthetic treatment of template-filled MCM-41 and Cl-MCM-41 with vapors of (3-chloropropyl)triethoxysilane and 1,2-ethylenediamine in vacuum. The chemical composition of obtained mesoporous silicas was estimated by IR spectroscopy and chemical analysis of surface products of reactions. Characteristics of porous structure of resulting materials were determined from the data of X-ray, low-temperature nitrogen ad-desorption and transmission electron microscopy measurements. Obtained results confirm invariability of highly ordered mesoporous structure of MCM-41 and Cl-MCM-41 after their selective postsynthetic modification in vapor phase. It was proved that proposed method of vapor-phase functionalization of template-filled starting materials is not accompanied by dissolution of the template and chemical modification of pores surface. This provides preferential localization of grafted functional groups onto the exterior surface of mesoporous silicas. - Graphical abstract: Solgel synthesis and postsynthetic chemical modification of template-filled MCM-41 and Cl-MCM-41 with (3-chloropropyl)triethoxysilane and 1,2-ethylenediamine in vapor phase. Display Omitted - Highlights: Synthesis of MCM-41 silica by template directed solgel condensation. Selective vapor-phase functionalization of template-filled silica particles. Preferential localization of grafted groups onto the exterior surface of mesoporous silicas.

  14. Calculating critical exponents of the phase-equilibrium curve for liquid-vapor aqueous solutions of aliphatic alcohols

    NASA Astrophysics Data System (ADS)

    Bazaev, E. A.; Bazaev, A. R.

    2013-06-01

    Based on previously obtained experimental data corresponding to the points of liquid-vapor phase transformations in aqueous solutions of aliphatic alcohols (methanol, ethanol, n-propanol), we plot the temperature dependence of the density of liquid and vapor phases along the curve of their coexistence and in the critical region. It is established that the power functions ? _{1,v} = ? _c (1 B_0 ? ^{? _0 } + B_1 ? ^{? _1 } B_2 ? ^{? _2 } ) and (? _1 - ? _v )/2? _c = B_0 ? ^{? _0 } + B_2 ? ^{? _2 } adequately describe the dependence of the lower density of solutions ? = (?l,p - ?c)/?c on reduced temperature ? = ( T c - T)/ T c, the alcohol concentration, and the number of carbon atoms (in a molecule of alcohol) in the two-phase region and in the vicinity of the critical point at critical index ?0 = 0.365 0.002 and B 0 = (2.471-2.803) 0.005.

  15. Effect of three-body interactions on the vapor-liquid phase equilibria of binary fluid mixtures.

    PubMed

    Wang, Liping; Sadus, Richard J

    2006-08-21

    Gibbs-Duhem Monte Carlo simulations are reported for the vapor-liquid phase coexistence of binary argon+krypton mixtures at different temperatures. The calculations employ accurate two-body potentials in addition to contributions from three-body dispersion interactions resulting from third-order triple-dipole interactions. A comparison is made with experiment that illustrates the role of three-body interactions on the phase envelope. In all cases the simulations represent genuine predictions with input parameters obtained independently from sources other than phase equilibria data. Two-body interactions alone are insufficient to adequately describe vapor-liquid coexistence. In contrast, the addition of three-body interactions results in very good agreement with experiment. In addition to the exact calculation of three-body interactions, calculations are reported with an approximate formula for three-body interactions, which also yields good results. PMID:16942347

  16. Low-Yield Cigarettes

    MedlinePLUS

    ... health consequences of smoking, cigarette manufacturers began heavily marketing cigarettes labeled "light," "low," and "mild" (or similar ... the implied promise of reduced toxicity underlying the marketing of such brands. 1,5,6 Information on ...

  17. Chemical Species in the Vapor Phase of Hanford Double-Shell Tanks: Potential Impacts on Waste Tank Corrosion Processes

    SciTech Connect

    Felmy, Andrew R.; Qafoku, Odeta; Arey, Bruce W.; Boomer, Kayle D.

    2010-09-22

    The presence of corrosive and inhibiting chemicals on the tank walls in the vapor space, arising from the waste supernatant, dictate the type and degree of corrosion that occurs there. An understanding of how waste chemicals are transported to the walls and the affect on vapor species from changing supernatant chemistry (e.g., pH, etc.), are basic to the evaluation of risks and impacts of waste changes on vapor space corrosion (VSC). In order to address these issues the expert panel workshop on double-shell tank (DST) vapor space corrosion testing (RPP-RPT-31129) participants made several recommendations on the future data and modeling needs in the area of DST corrosion. In particular, the drying of vapor phase condensates or supernatants can form salt or other deposits at the carbon steel interface resulting in a chemical composition at the near surface substantially different from that observed directly in the condensates or the supernatants. As a result, over the past three years chemical modeling and experimental studies have been performed on DST supernatants and condensates to predict the changes in chemical composition that might occur as condensates or supernatants equilibrate with the vapor space species and dry at the carbon steel surface. The experimental studies included research on both the chemical changes that occurred as the supernatants dried as well as research on how these chemical changes impact the corrosion of tank steels. The chemical modeling and associated experimental studies were performed at the Pacific Northwest National Laboratory (PNNL) and the research on tank steel corrosion at the Savannah River National Laboratory (SRNL). This report presents a summary of the research conducted at PNNL with special emphasis on the most recent studies conducted in FY10. An overall summary of the project results as well as their broader implications for vapor space corrosion of the DSTs is given at the end of this report.

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

    USGS Publications Warehouse

    Fournier, R.O.

    1976-01-01

    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.

  19. ZnO nanorod growth by plasma-enhanced vapor phase transport with different growth durations

    SciTech Connect

    Kim, Chang-Yong; Oh, Hee-bong; Ryu, Hyukhyun; Yun, Jondo; Lee, Won-Jae

    2014-09-01

    In this study, the structural properties of ZnO nanostructures grown by plasma-enhanced vapor phase transport (PEVPT) were investigated. Plasma-treated oxygen gas was used as the oxygen source for the ZnO growth. The structural properties of ZnO nanostructures grown for different durations were measured by scanning electron microscopy, x-ray diffraction, and transmission electron microscopy. The authors comprehensively analyzed the growth of the ZnO nanostructures with different growth durations both with and without the use of plasma-treated oxygen gas. It was found that PEVPT has a significant influence on the growth of the ZnO nanorods. PEVPT with plasma-treated oxygen gas facilitated the generation of nucleation sites, and the resulting ZnO nanorod structures were more vertical than those prepared by conventional VPT without plasma-treated oxygen gas. As a result, the ZnO nanostructures grown using PEVPT showed improved structural properties compared to those prepared by the conventional VPT method.

  20. Synthesis and in-situ characterization of superparamagnetic nanocomposites from vapor phase condensation

    SciTech Connect

    Zachariah, M.R.; McMillin, B.; Shull, R.D.; Biswas, P.

    1995-12-31

    Recent work on the magnetic characteristics of manometer scale materials has suggested that magnetically isolated manometer magnetic particles would show magnetic behavior different than those found in the bulk. We have investigated application of flame technology for the synthesis of this class of materials. A premixed methane/oxygen flame diluted with nitrogen has been used as the reacting environment in which iron carbonyl and hexamethyldisiloxane was added as the magnetic and non-magnetic precursor materials. The flame structure was adjusted to obtain an oxygen rich environment in which oxides of iron and silica would condense from the vapor. The results based on X-ray diffraction, electron microscopy, Mossbauer effect and magnetization have shown that: (1) Nanometer composite particles are formed containing 5-10 nm Fe{sub 2}O{sub 3}, encased in a silica particle whose diameter ranged from 30-100 nm depending on loading and flame temperature. (2) The iron oxide clusters are magnetically isolated and in some cases show superparamagnetic behavior. In this paper the effect of iron/silica ratio will be discussed along with particle morphology and size sensitivity to flame parameters. In-situ characterization using planar laser induced fluorescence and planar laser light scattering have been used, inconjunction with an image intensified CCD camera to map the temperature, particle field, and FeO and SiO gas phase concentrations.

  1. Vapor Phase Hydrogenation of Nitrobenzene to Aniline Over Carbon Supported Ruthenium Catalysts.

    PubMed

    Srikanth, Chakravartula S; Kumar, Vanama Pavan; Viswanadham, Balaga; Srikanth, Amirineni; Chary, Komandur V R

    2015-07-01

    A series of Ru/Carbon catalysts (0.5-6.0 wt%) were prepared by impregnation method. The catalysts were characterized by X-ray diffraction (XRD), transmission electron microscopy (TEM), temperature programmed reduction (TPR), X-ray photoelectron spectroscopy (XPS), CO-chemisorption, surface area and pore-size distribution measurements. The catalytic activities were evaluated for the vapor phase hydrogenation of nitrobenzene. The dispersion measured by CO-uptake values suggests that a decrease of dispersion is observed with increasing Ru loading on carbon support. These findings are well supported by the crystallite size measured from XRD measurements. XPS study reveals the formation of Ru0 after reduction at 573 K for 3 h. The catalysts exhibit high conversion/selectivity at 4.5 wt% Ru loading during hydrogenation reaction. The particle size measured from CO-chemisorption and TEM analysis are related to the TOF during the hydrogenation reaction. Ru/C catalysts are found to show higher conversion/selectivities during hydrogenation of nitrobenzene to aniline. PMID:26373150

  2. Epitaxial growth of three dimensionally structured III-V photonic crystal via hydride vapor phase epitaxy

    NASA Astrophysics Data System (ADS)

    Zheng, Qiye; Kim, Honggyu; Zhang, Runyu; Sardela, Mauro; Zuo, Jianmin; Balaji, Manavaimaran; Lourdudoss, Sebastian; Sun, Yan-Ting; Braun, Paul V.

    2015-12-01

    Three-dimensional (3D) photonic crystals are one class of materials where epitaxy, and the resultant attractive electronic properties, would enable new functionalities for optoelectronic devices. Here we utilize self-assembled colloidal templates to fabricate epitaxially grown single crystal 3D mesostructured GaxIn1-xP (GaInP) semiconductor photonic crystals using hydride vapor phase epitaxy (HVPE). The epitaxial relationship between the 3D GaInP and the substrate is preserved during the growth through the complex geometry of the template as confirmed by X-ray diffraction (XRD) and high resolution transmission electron microscopy. XRD reciprocal space mapping of the 3D epitaxial layer further demonstrates the film to be nearly fully relaxed with a negligible strain gradient. Fourier transform infrared spectroscopy reflection measurement indicates the optical properties of the photonic crystal which agree with finite difference time domain simulations. This work extends the scope of the very few known methods for the fabrication of epitaxial III-V 3D mesostructured materials to the well-developed HVPE technique.

  3. Carbon-Supported bimetallic Pd-Fe catalysts for vapor-phase hydrodeoxygenation of guaiacol

    SciTech Connect

    Sun, Junming; Karim, Ayman M.; Zhang, He; Kovarik, Libor; Li, Xiaohong S.; Hensley, Alyssa; McEwen, Jean-Sabin; Wang, Yong

    2013-10-01

    Abstract Carbon supported metal catalysts (Cu/C, Fe/C, Pd/C, Pt/C, PdFe/C and Ru/C) have been prepared, characterized and tested for vapor-phase hydrodeoxygenation (HDO) of guaiacol (GUA) at atmospheric pressure. Phenol was the major intermediate on all catalysts. Over the noble metal catalysts saturation of the aromatic ring was the major pathway observed at low temperature (250 °C), forming predominantly cyclohexanone and cyclohexanol. Substantial ring opening reaction was observed on Pt/C and Ru/C at higher reaction temperatures (e.g., 350 °C). Base metal catalysts, especially Fe/C, were found to exhibit high HDO activity without ring-saturation or ring-opening with the main products being benzene, phenol along with small amounts of cresol, toluene and trimethylbenzene (TMB). A substantial enhancement in HDO activity was observed on the PdFe/C catalysts. Compared with Fe/C, the yield to oxygen-free aromatic products (i.e., benzene/toluene/TMB) on PdFe/C increased by a factor of four at 350 °C, and by approximately a factor of two (83.2% versus 43.3%) at 450 °C. The enhanced activity of PdFe/C is attributed to the formation of PdFe alloy as evidenced by STEM, EDS and TPR.

  4. Acceptance Testing of the Vapor Phase Catalytic Ammonia Removal Engineering Development Unit

    NASA Technical Reports Server (NTRS)

    Flynn, Michael; Fisher, John; Kliss, Mark; Tleimat, Maher; Quinn, Gregory; Fort, James; Nalette, Tim; Baker, Gale

    2005-01-01

    This paper describes the results of acceptance testing of the Vapor Phase Catalytic Ammonia Removal (VPCAR) technology. The VPCAR technology is currently being developed by NASA as a Mars transit vehicle water recycling system. NASA has recently completed a grant to develop a next generation VPCAR system. This grant was peer reviewed and funded through the Advanced Life Support (ALS) National Research Announcement (NRA). The grant funded a contract with Water Reuse Technology Inc. to construct an engineering development unit. This contract concluded with the shipment of the final deliverable to NASA on 8/31/03. The objective of the acceptance testing was to characterize the performance of this new system. This paper presents the results of mass power, and volume measurements for the delivered system. In addition, product water purity analysis for a Mars transit mission and a planetary base wastewater ersatz are provided. Acoustic noise levels, interface specifications and system reliability results are also discussed. An assessment of the readiness of the technology for human testing and recommendations for future improvements are provided.

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

    NASA Astrophysics Data System (ADS)

    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

    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 30.180.1 meV in the freestanding Samsung wafer. The activation energy of O is found to be 33.200.1 meV. An unidentified third donor with an activation energy of 31.230.1 meV also was observed. Integrated absorption cross sections are found to be 8.510-14 cm for Si and 8.610-14 cm for O.

  6. Influence of plasma treatment time on plasma induced vapor phase grafting modification of PBO fiber surface

    NASA Astrophysics Data System (ADS)

    Song, B.; Meng, L. H.; Huang, Y. D.

    2012-05-01

    The surface of poly-p-phenylene benzobisthiazole (PBO) fibers was treated through oxygen plasma induced vapor phase grafting (PIVPG) method under various oxygen plasma pre-treatment time conditions. The surface chemical composition, surface morphologies and surface free energy of pristine and treated PBO fibers were studied using X-ray photoelectron spectroscopy, atomic force microscopy, scanning electron microscopy, and Cahn DCAA system. The mechanics property of these fibers was evaluated by tensile strength and interfacial shear strength (IFSS). It was found that the surface characteristics of treated PBO fibers occurred significant change compare with the pristine PBO fibers. After treatment, the polar functional groups were introduced on the fiber surface. Carbon concentration decreased; oxygen concentration and elemental ratio of oxygen to carbon increased. Acrylic acid can react with the activated PBO fibers surface, which led to the fiber surface roughness increased. The surface free energy increased from 41.4 mN/m to 62.8 mN/m when PBO fibers were plasma pre-treated for 10 min, while the IFSS of PBO fibers with epoxy resin increased from 36.6 MPa to 55.8 MPa. Therefore, PIVPG can be used to enhance the interfacial bond between PBO fibers and epoxy resin.

  7. Environmentally Compatible Vapor-Phase Corrosion Inhibitor for Space Shuttle Hardware

    NASA Technical Reports Server (NTRS)

    Novak, Howard L.; Hall, Phillip B.

    2003-01-01

    USA-SRB Element is responsible for the assembly and refurbishment of the non-motor components of the SRB as part of Space Shuttle. Thrust Vector Control (TVC) frames structurally support components of the TVC system located in the aft skirt of the SRB. TVC frames are exposed to the seacoast environment after refurbishment and, also, to seawater immersion after splashdown, and during tow-back to CCAFS-Hangar AF refurbishment facilities. During refurbishment operations it was found that numerous TVC frames were experiencing internal corrosion and coating failures, both from salt air and seawater intrusions. Inspectors using borescopes would visually examine the internal cavities of the complicated aluminum alloy welded tubular structure. It was very difficult for inspectors to examine cavity corners and tubing intersections and particularly, to determine the extent of the corrosion and coating anomalies. Physical access to TVC frame internal cavities for corrosion removal and coating repair was virtually impossible, and an improved method using a Liquid (water based) Vapor-phase Corrosion Inhibitor (LVCI) for preventing initiation of new corrosion, and mitigating and/or stopping existing corrosion growth was recommended in lieu of hazardous paint solvents and high VOC / solvent based corrosion inhibitors. In addition, the borescopic inspection method used to detect corrosion, and/or coating anomalies had severe limitations because of part geometry, and an improved non-destructive inspection (NDI) method using Neutron Radiography (N-Ray) was also recommended.

  8. Environmentally Compatible Vapor-Phase Corrosion Inhibitor for Space Shuttle Hardware

    NASA Technical Reports Server (NTRS)

    Novak, Howard L.; Hall, Phillip B.; Martin, David (Technical Monitor)

    2002-01-01

    USA-SRB Element is responsible for the assembly and refurbishment of the non-motor components of the SRB as part of Space Shuttle. Thrust Vector Control (TVC) frames structurally support components of the TVC system located in the aft skirt of the SRB (Solid Rocket Booster). TVC frames are exposed to the seacoast environment after refurbishment and, also, to seawater immersion after splashdown, and during tow-back to CCAFS-Hangar AF refurbishment facilities. During refurbishment operations it was found that numerous TVC frames were experiencing internal corrosion and coating failures, both from salt air and seawater intrusions. Inspectors using borescopes would visually examine the internal cavities of the complicated aluminum alloy welded tubular structure. It was very difficult for inspectors to examine cavity corners and tubing intersections and particularly. to determine the extent of the corrosion and coating anomalies. Physical access to TVC frame internal cavities for corrosion removal and coating repair was virtually impossible, and an improved method using a Liquid (water based) Vapor-phase Corrosion Inhibitor (LVCI) for preventing initiation of new corrosion, and mitigating and/or stopping existing corrosion growth was recommended in lieu of hazardous paint solvents and high VOC/solvent based corrosion inhibitors. In addition, the borescopic inspection method used to detect corrosion, and/or coating anomalies had severe limitations because of part geometry, and an improved non-destructive inspection (NDI) method using Neutron Radiography (N-Ray) was also recommended.

  9. GaAs [ital c](4[times]4) surface structure in organometallic vapor-phase epitaxy

    SciTech Connect

    Payne, A.P.; Fuoss, P.H. ); Kisker, D.W.; Stephenson, G.B. ); Brennan, S. )

    1994-05-15

    While GaAs(001) surface reconstructions have been studied extensively in the ultrahigh-vacuum environment associated with molecular-beam epitaxy (MBE), comparatively little is known of these structures in the chemically rich environment associated with organometallic vapor-phase epitaxy (OMVPE). This work presents a structural study of the [ital c](4[times]4) surface reconstruction stabilized in an arsenic-rich OMVPE environment. Measurements of the in-plane structure were performed [ital in] [ital situ] using grazing-incidence x-ray scattering with synchrotron radiation. Structural refinement confirms the presence of arsenic-arsenic dimers arranged with the [ital c](4[times]4) symmetry. In concurrence with similar studies performed in the MBE environment, it is found that the surface is a mixture of structural domains composed of two- and three-dimer variants of the [ital c](4[times]4) reconstruction. Atomic positions associated with these structures are presented. The size, aspect ratio, and orientation of the reconstructed regions are shown to be closely related to the atomic step geometry on the crystal surface.

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

    PubMed

    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

    2013-01-24

    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 β-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

  11. Vapor-phase-processed fluorinated self-assembled monolayer for organic thin-film transistors

    NASA Astrophysics Data System (ADS)

    Roh, Jeongkyun; Lee, Changhee; Kwak, Jeonghun; Jung, Byung Jun; Kim, Hyeok

    2015-09-01

    A vapor-phase-processed fluorinated silazane self-assembled monolayer (SAM), 1,3-bis(trifluoropropyl)-1,1,3,3-tetramethyldisilazane (FPDS), was introduced as a surface modifier for pentacene-based organic thin-film transistors (OTFTs). A remarkable improvement in the field effect mobility from 0.25 cm2/Vs (without SAM-treatment) to 0.42 cm2/Vs (with FPDS-treatment) was observed, which was attributed to the better pentacene growth on a hydrophobic surface. A significant reduction in the contact resistance was also observed by FPDS treatment due to the improved bulk conductivity and diminished charge trapping at the gate dielectric surface by the SAM treatment. In addition, FPDS treatment efficiently improved the bias stability of the OTFTs; the drain-to-source current degradation by the bias stress was greatly reduced from 80% to 50% by FPDS treatment, and the characteristic time for charge trapping of the FPDS treated OTFTs was approximately one order of magnitude larger than that of the OTFTs without SAM treatment.

  12. Deep hole traps in undoped n-GaN films grown by hydride vapor phase epitaxy

    NASA Astrophysics Data System (ADS)

    Lee, In-Hwan; Polyakov, A. Y.; Smirnov, N. B.; Govorkov, A. V.; Usikov, A. S.; Helava, H.; Makarov, Yu. N.; Pearton, S. J.

    2014-06-01

    Deep hole traps were studied in bulk free-standing GaN crystals and in thinner (10-20 ?m) GaN films prepared by hydride vapor phase epitaxy (HVPE) on sapphire. Six hole traps in different combinations were detected in these crystals, H1 (activation energy 0.92-0.94 eV), H2 (0.55 eV), H3 (0.65-0.7 eV), H4 (0.85-0.9 eV), H5 (1.1-1.2 eV), and H6 (0.95-1.05 eV). The dominant traps in all samples were the H5 and H6 traps that were attributed, respectively, to gallium vacancy complexes with oxygen (VGa-O) and substitutional carbon related centers. We associate the H5 hole traps with the red luminescence bands, the H4 hole traps with the green luminescence bands, and the H6 hole traps with the yellow luminescence bands often observed in HVPE GaN. These attributions are based on the low energy thresholds of the deep traps optical excitation spectra and the depth of the respective trap levels.

  13. Environmentally Compatible Vapor-Phase Corrosion Inhibitor for Space Shuttle Hardware

    NASA Technical Reports Server (NTRS)

    Novak, Howard L.; Hall, Phillip B.; McCool, Alex (Technical Monitor)

    2001-01-01

    USA-SRB Element is responsible for the assembly and refurbishment of the non-motor components of the SRB as part of Space Shuttle. Thrust Vector Control (TVC) frames structurally support components of the TVC system located in the aft skirt of the SRB. TVC frames are exposed to the seacoast environment after refurbishment and, also, to seawater immersion after splashdown, and during tow-back to CCAFS-Hangar AF refurbishment facilities. During refurbishment operations it was found that numerous TVC frames were experiencing internal corrosion and coating failures, both from salt air and seawater intrusions. Inspectors using borescopes would visually examine the internal cavities of the complicated aluminum alloy welded tubular structure. It was very difficult for inspectors to examine cavity corners and tubing intersections and particularly, to determine the extent of the corrosion and coating anomalies. Physical access to TVC frame internal cavities for corrosion removal and coating repair was virtually impossible, and an improved method using a Liquid (water based) Vapor-phase Corrosion Inhibitor (LVCI) for preventing initiation of new corrosion, and mitigating and/or stopping existing corrosion growth was recommended in lieu of hazardous paint solvents and high VOC/solvent based corrosion inhibitors. In addition, the borescopic inspection method used to detect corrosion, and/or coating anomalies had severe limitations because of part geometry, and an improved non-destructive inspection (NDI) method using Neutron Radiography (N-Ray) was also recommended.

  14. Hydride vapor phase epitaxy and characterization of high-quality ScN epilayers

    SciTech Connect

    Oshima, Yuichi Vllora, Encarnacin G.; Shimamura, Kiyoshi

    2014-04-21

    The heteroepitaxial growth of ScN films was investigated on various substrates by hydride vapor phase epitaxy (HVPE). Single crystalline mirror-like ScN(100) and ScN(110) layers were successfully deposited on r- and m-plane sapphire substrates, respectively. Homogeneous stoichiometric films (N/Sc ratio 1.01??0.10) up to 40??m in thickness were deposited. Their mosaicity drastically improved with increasing the film thickness. The band gap was determined by optical methods to be 2.06?eV. Impurity concentrations including H, C, O, Si, and Cl were investigated through energy dispersive X-ray spectrometry and secondary ion mass spectrometry. As a result, it was found that the presence of impurities was efficiently suppressed in comparison with that of HVPE-grown ScN films reported in the past, which was possible thanks to the home-designed corrosion-free HVPE reactor. Room-temperature Hall measurements indicated that the residual free electron concentrations ranged between 10{sup 18}10{sup 20}?cm{sup ?3}, which was markedly lower than the reported values. The carrier mobility increased monotonically with the decreasing in carrier concentration, achieving the largest value ever reported, 284?cm{sup 2}?V{sup ?1}?s{sup ?1} at n?=?3.7??10{sup 18}?cm{sup ?3}.

  15. Vapor Phase Synthesis of Organometal Halide Perovskite Nanowires for Tunable Room-Temperature Nanolasers.

    PubMed

    Xing, Jun; Liu, Xin Feng; Zhang, Qing; Ha, Son Tung; Yuan, Yan Wen; Shen, Chao; Sum, Tze Chien; Xiong, Qihua

    2015-07-01

    Semiconductor nanowires have received considerable attention in the past decade driven by both unprecedented physics derived from the quantum size effect and strong isotropy and advanced applications as potential building blocks for nanoscale electronics and optoelectronic devices. Recently, organic-inorganic hybrid perovskites have been shown to exhibit high optical absorption coefficient, optimal direct band gap, and long electron/hole diffusion lengths, leading to high-performance photovoltaic devices. Herein, we present the vapor phase synthesis free-standing CH3NH3PbI3, CH3NH3PbBr3, and CH3NH3PbIxCl3(-x) perovskite nanowires with high crystallinity. These rectangular cross-sectional perovskite nanowires have good optical properties and long electron hole diffusion length, which ensure adequate gain and efficient optical feedback. Indeed, we have demonstrated optical-pumped room-temperature CH3NH3PbI3 nanowire lasers with near-infrared wavelength of 777 nm, low threshold of 11 ?J/cm(2), and a quality factor as high as 405. Our research advocates the promise of optoelectronic devices based on organic-inorganic perovskite nanowires. PMID:26043362

  16. Pentacene/K12 solar cells formed by organic vapor phase deposition

    NASA Astrophysics Data System (ADS)

    Axmann, Sebastian; Brast, Michael; Pandey, Ajay Kumar; Burn, Paul; Meredith, Paul; Heuken, Michael; Vescan, Andrei; Kalisch, Holger

    2014-01-01

    This study reports on an organic solar cell structure utilizing K12 as a new low-temperature processable small-molecule acceptor material. Pentacene (PEN) and K12 were deposited onto indium tin oxide by means of organic vapor phase deposition (OVPD) as bilayer solar cells. The resulting solar cell was characterized electrically by current density-voltage (J-V) measurements and optically by photocurrent and reflectivity measurements. The J-V characteristic under AM 1.5 illumination indicates a short-circuit current of 0.45 mA/cm2 (Jsc), a fill factor of 38% (FF), and an open-circuit (Voc) voltage of 0.71 V. Current generation is found to predominantly occur in the K12 layer, although strong light absorption in the PEN layer is detected. We suggest that either a dipole shift between the layers or the fission of singlet excitons in the PEN layer leads to this observation. Although the efficiency of the device is low in combination with PEN, our experiment successfully demonstrates the use of K12 as a low-temperature acceptor material in OVPD processes.

  17. Cantilever Epitaxy of AlN using Hydride Vapor Phase Epitaxy

    NASA Astrophysics Data System (ADS)

    Newman, Scott A.; Kamber, Derrick S.; Wu, Yuan; Letts, Edward; Denbaars, Steven P.; Speck, James S.; Nakamura, Shuji

    2007-03-01

    AlN is an important material for AlGaN-based electronic and optoelectronic devices such as UV Light Emitting Diodes and High Electron Mobility Transistors. We have grown AlN films with reduced Threading Dislocation (TD) densities using Cantilever Epitaxy with the Hydride Vapor Phase Epitaxy growth method. Prior to growth, 6H-SiC substrates were processed using standard lithography and ICP etching to form periodic ridge/trench patterns. Ridges were oriented in the <1100 >SiC direction, and trenches were etched up to 12.6 μm deep. AlN was grown laterally from 2-4 μm wide ridges over 3-6 μm wide trenches and coalesced. Plan-view TEM analysis showed that TD densities in the wing regions were less than 8.3 x 10^6 cm-2 as compared to 3.9 x 10^9 in the seed regions. The TDs are predominantly edge-type with b =13<112 0 >. Most of these TDs originate from the AlN-SiC interfaces on the tops of the ridges and propagate vertically. A small number of inclined dislocations propagate into the wing region.

  18. AlN thin film grown on different substrates by hydride vapor phase epitaxy

    NASA Astrophysics Data System (ADS)

    Sun, M. S.; Zhang, J. C.; Huang, J.; Wang, J. F.; Xu, K.

    2016-02-01

    AlN thin films have been grown on GaN/sapphire templates, 6 H-SiC and sapphire by hydride vapor phase epitaxy. The influence of growth conditions and substrates on the crystal qualities and growth mode has been investigated by X-ray diffraction (XRD) and atomic force microscopy (AFM). The results showed that the low pressure was favorable for high-quality AlN thin film growth around 1000 °C. The full-width at half-maximum (FWHM) of (0002) XRD of 200-nm AlN thin film grown on GaN/sapphire, 6 H-SiC and sapphire are 220, 187 and 260 arc s, respectively. While the corresponding counterparts of (10-12) are 1300, 662 and 2650 arc s, respectively. Both suggested that low dislocation density in AlN grown on 6 H-SiC. The morphology of AlN thin film on sapphire showed islands without coalescence initially, and then changed to be coalescent with atomic steps at 1200 nm. However, those for samples on 6 H-SiC and GaN/sapphire showed smooth surface with clear atomic steps at thickness of 200 nm. The result indicated different growth modes of AlN on different substrates. It was believed that the different lattice mismatchs between AlN and substrates led to the different crystal qualities and growth modes.

  19. Vapor phase reactions in polymerization plasma for divinylsiloxane-bis-benzocyclobutene film deposition

    SciTech Connect

    Kinoshita, Keizo; Nakano, Akinori; Kawahara, Jun; Kunimi, Nobutaka; Hayashi, Yoshihiro; Kiso, Osamu; Saito, Naoaki; Nakamura, Keiji; Kikkawa, Takamaro

    2006-11-15

    Vapor phase reactions in plasma polymerization of divinylsiloxane-bis-benzocyclobutene (DVS-BCB) low-k film depositions on 300 mm wafers were studied using mass spectrometry, in situ Fourier transform infrared, and a surface wave probe. Polymerization via Diels-Alder cycloaddition reaction was identified by the detection of the benzocyclohexene group. Hydrogen addition and methyl group desorption were also detected in DVS-BCB monomer and related large molecules. The dielectric constant k of plasma polymerized DVS-BCB with a plasma source power range up to 250 W was close to {approx}2.7 of thermally polymerized DVS-BCB, and increased gradually over 250 W. The electron density at 250 W was about 1.5x10{sup 10} cm{sup -3}. The increase of the k value at higher power was explained by the decrease of both large molecular species via multistep dissociation and incorporation of silica components into the polymer. It was found that the reduction of electron density as well as precursor residence time is important for the plasma polymerization process to prevent the excess dissociation of the precursor.

  20. Radiation-induced defects in GaN bulk grown by halide vapor phase epitaxy

    SciTech Connect

    Duc, Tran Thien; Pozina, Galia; Son, Nguyen Tien; Janzn, Erik; Hemmingsson, Carl; Ohshima, Takeshi

    2014-09-08

    Defects induced by electron irradiation in thick free-standing GaN layers grown by halide vapor phase epitaxy were studied by deep level transient spectroscopy. In as-grown materials, six electron traps, labeled D2 (E{sub C}0.24?eV), D3 (E{sub C}0.60?eV), D4 (E{sub C}0.69?eV), D5 (E{sub C}0.96?eV), D7 (E{sub C}1.19?eV), and D8, were observed. After 2?MeV electron irradiation at a fluence of 1??10{sup 14?}cm{sup ?2}, three deep electron traps, labeled D1 (E{sub C}0.12?eV), D5I (E{sub C}0.89?eV), and D6 (E{sub C}1.14?eV), were detected. The trap D1 has previously been reported and considered as being related to the nitrogen vacancy. From the annealing behavior and a high introduction rate, the D5I and D6 centers are suggested to be related to primary intrinsic defects.

  1. Nanostructured microcantilevers with functionalized cyclodextrin receptor phases: self-assembled monolayers and vapor-deposited films.

    PubMed

    Tipple, Christopher A; Lavrik, Nickolay V; Culha, Mustafa; Headrick, Jeremy; Datskos, Panos; Sepaniak, Michael J

    2002-07-01

    It is shown that the performance of microcantilver-based chemical sensors in a liquid environment is affected by altering cantilever surface morphology and receptor phase type and thickness. Self-assembled monolayers of thiolated beta-cyclodextrin (HM-beta-CD) and thin films of vapor-deposited heptakis (2,3-O-diacetyl-6-O-tertbutyl-dimethylsilyl)-beta-cyclodextrin (HDATB-beta-CD) were studied on smooth and nanostructured (dealloyed) gold-coated microcantilever surfaces. The dealloyed surface contains nanometer-sized features that enhance the transduction of molecular recognition events into cantilever response, as well as increase film stability for thicker films. Improvements in the limits of detection of the compound 2,3-dihydroxynaphthalene as great as 2 orders of magnitude have been achieved by manipulating surface morphology and film thickness. The observed response factors for the analytes studied varied from 0.02-604 nm/ppm, as determined by cantilever deflection. In general, calibration plots for the analytes were linear up to several hundred nanometers in cantilever deflections. PMID:12141672

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

    NASA Astrophysics Data System (ADS)

    Meeks, Ellen

    1996-10-01

    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.

  3. Cigars, Cigarettes, and Adolescents

    ERIC Educational Resources Information Center

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

    2008-01-01

    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

  4. Field tests of a chemiresistor sensor for in-situ monitoring of vapor-phase contaminants

    NASA Astrophysics Data System (ADS)

    Ho, C.; McGrath, L.; Wright, J.

    2003-04-01

    An in-situ chemiresistor sensor has been developed that can detect volatile organic compounds in subsurface environmental applications. Several field tests were conducted in 2001 and 2002 to test the reliability, operation, and performance of the in-situ chemiresistor sensor system. The chemiresistor consists of a carbon-loaded polymer deposited onto a microfabricated circuit. The polymer swells reversibly in the presence of volatile organic compounds as vapor-phase molecules absorb into the polymer, causing a change in the electrical resistance of the circuit. The change in resistance can be calibrated to known concentrations of analytes, and arrays of chemiresistors can be used on a single chip to aid in discrimination. A waterproof housing was constructed to allow the chemiresistor to be used in a variety of media including air, soil, and water. The integrated unit, which can be buried in soils or emplaced in wells, is connected via cable to a surface-based solar-powered data logger. A cell-phone modem is used to automatically download the data from the data logger on a periodic basis. The field tests were performed at three locations: (1) Edwards Air Force Base, CA; (2) Nevada Test Site; and (3) Sandia's Chemical Waste Landfill near Albuquerque, NM. The objectives of the tests were to evaluate the ruggedness, longevity, operation, performance, and engineering requirements of these sensors in actual field settings. Results showed that the sensors could be operated continuously for long periods of time (greater than a year) using remote solar-powered data-logging stations with wireless telemetry. The sensor housing, which was constructed of 304 stainless steel, showed some signs of corrosion when placed in contaminated water for several months, but the overall integrity was maintained. The detection limits of the chemiresistors were generally found to be near 0.1% of the saturated vapor pressure of the target analyte in controlled laboratory conditions (e.g., ~100 ppmv for TCE), but fluctuations in environmental parameters and other interferences increased the detection limit by about an order of magnitude in the field tests. Sandia is a multiprogram laboratory operated by Sandia Corporation, a Lockheed Martin Company, for the United States Department of Energy under Contract DE-AC04-94AL85000.

  5. Polynuclear aromatic compounds and genotoxicity in particulate and vapor phases of ambient air: effect of traffic, season, and meteorological conditions

    SciTech Connect

    Tuominen, J.; Salomaa, S.; Pyysalo, H.; Skyttae, E.; Tikkanen, L.; Nurmeal, T.; Sorsa, M.; Pohjola, V.; Sauri, M.; Himberg, K.

    1984-10-01

    High-volume samples of ambient air were collected by glass-fiber filter (particulate) and XAD-2 resin (vapor) from three locations in Finland: two cities and a rural area. Samples were analyzed for polynuclear aromatic hydrocarbons (PAH) and selected other polynuclear compounds. Genotoxocity of the samples was assayed in the Ames Salmonella/microsome test and sister chromatid exchange assay before and after fractionation into four fractions of increasing polarity. The ratio of PAH in the vapor and particulate phases of the samples varied considerably with the season, and the scavenging effect of snow and rain was as well clearly demonstrated. The rural samples showed minimal or no genotoxic activity, whereas at the urban sites not only the particulate-phase but also the vapor-phase samples were mutagenic. The genotoxicity was mainly associated with the most polar fractions of both phases. Studies with the nitroreductase-deficient Salmonella strain TA98NR indicated, that in the urban air samples collected in winter, a considerable part of the mutagenicity detected in the Ames test was due to NO/sub 22/-substituted compounds. Traffic is suggested to be the major determinant for the genotoxic activity in the ambient air.

  6. Comparison of hole traps in n-GaN grown by hydride vapor phase epitaxy, metal organic chemical vapor deposition, and epitaxial lateral overgrowth

    NASA Astrophysics Data System (ADS)

    Polyakov, A. Y.; Lee, I.-H.; Smirnov, N. B.; Govorkov, A. V.; Kozhukhova, E. A.; Pearton, S. J.

    2011-06-01

    Optical deep level spectroscopy (ODLTS) and microcathodoluminescence (MCL) spectra were measured for a large group of n-GaN samples grown via metalorganic chemical vapor deposition (MOCVD), epitaxial lateral overgrowth (ELOG), or hydride vapor phase epitaxy (HVPE). In the MOCVD and ELOG samples, the ionization energy of dominant hole traps H1 was dependent on the excitation conditions and was 0.9 eV for high injection levels providing saturation of the ODLTS peak magnitude. The trap concentration increased with increasing Si donor concentration and correlated with the yellow band intensity in the MCL spectra. For the HVPE samples, the hole trap spectra were radically different from the MOCVD case: four hole trapsH2, H3, H4, and H5with activation energies of 0.55, 0.65, 0.85, and 1.2 eV, respectively, were detected. In the MCL spectra, a broad green band that peaked near 2.5 eV was observed in addition to the usual yellow luminescence near 2.3 eV. This green band was attributed to the transitions involving the H4 hole traps. Possible identities of the hole traps detected in the MOCVD/ELOG and HVPE samples are discussed.

  7. Vapor-phase interactions and diffusion of organic solvents in the unsaturated zone

    USGS Publications Warehouse

    Roy, W.R.; Griffin, R.A.

    1990-01-01

    This article presents an analysis of the interactions and static movement of 37 organic solvents as vapors through the unsaturated soil zone. The physicochemical interactions of the organic vapors with unsaturated soil materials were emphasized with focus on diffusive, and adsorptive interactions. Fick's Law and porous media diffusion coefficients for most of the solvent vapors were either compiled or estimated; coefficients were not available for some of the fluorinated solvents. The adsorption of some of the solvent vapors by silica was concluded to be due to hydrogen bond formation with surface silanol groups. Heats of adsorption data for different adsorbents were also compiled. There were very few data on the adsorption of these solvent vapors by soils, but it appears that the magnitude of adsorption of nonpolar solvents is reduced as the relative humidity of the vapor-solid system is increased. Consequently, the interaction of the vapors may then separated into two processes; (1) gas-water partitioning described by Henry's Law constants, and (2) solid-water adsorption coefficients which may be estimated from liquid-solid partition coefficients (Kd values). ?? 1990 Springer-Verlag New York Inc.

  8. Growth of bulk AlN crystals by vapor-phase epitaxy from atomic Al and NH3

    NASA Astrophysics Data System (ADS)

    Pogorel'skii, M. Yu.; Alekseev, A. N.; Pogorel'skii, Yu. V.; Shkurko, A. P.

    2015-09-01

    A new approach to obtaining bulk AlN single crystals by vapor-phase epitaxy has been tested. NH3 and Al vapor were used as growth reagents. The following ranges of growth parameters were admissible for the laboratory equipment (experimental growth installation): temperatures of 1050-1500C at ammonia flow rates of up to 50 sccm and pressures on the order of 10-5-10-4 bar, growth rates of up to 200 ?m h-1. At a temperature of 1450C, samples of strained bulk block AlN crystals with thicknesses of up to 200 ?m were obtained in the wurtzite phase in the [0001] direction on MBE templates based on sapphire substrates with a diameter of 2?.

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

    NASA Astrophysics Data System (ADS)

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

    2013-04-01

    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 {1100} facets and a sharp and flat (0001) N-face or c- face. The (0001) Ga-face or c+ face became faceted with {1011} planes emerging with reduced pressures and temperatures. Based on the stable facets, kinetic Wulff plots were constructed.

  10. Effectiveness of cigarette filter tips for reducing cadmium in relation to other mainstream smoke constituents

    SciTech Connect

    Bache, C.A.; Lisk, D.J.; Shane, B.S.; Hoffmann, D.; Adams, J.D.

    1987-01-01

    The effectiveness of filter tips for reducing cadmium, tar, nicotine, carbon monoxide and carbon dioxide in cigarettes was studied. The cigarettes were made from tobacco grown on municipal sewage sludge-amended soil and were therefore high in cadmium. When machine-smoked, filter tips did not result in a significant reduction of cadmium deposited on Cambridge filters. This may indicate that a considerable fraction of cadmium is present in the vapor phase of the smoke and therefore not reduced to the same extent as the tar by certain filters. Nicotine and carbon monoxide were reduced to a lesser extent than tar. This indicates that the filter tip has influenced the combustion of the tobacco column during smoking.

  11. Determination of nitroalkanes in mainstream cigarette smoke by heart-cutting multidimensional gas chromatography system coupled with mass spectrometry detection.

    PubMed

    Wang, Xiaoyu; Guo, Jizhao; Shang, Jingjing; Ding, Li; Zhao, Ge; Xie, Fuwei; Jia, Yunzhen; Qin, Yaqiong; Yu, Yongjie; Chen, Li; Zhang, Shusheng

    2015-12-11

    In this paper, heart-cutting two-dimensional GC/MS (GC-GC/MS) method in combination with a simple sample collection procedure was developed for the determination of 6 nitroalkanes in mainstream cigarette smoke. The method could remove large amounts of impurities on-line in the first polar column by heart-cuts and separate from the left interferences in a second mid-polar column. And the target compounds could be focused at the inlet of the second column by cryo-concentration. Compared to conventional GC/MS, GC-GC/MS achieved a lower noise level and sensitivity at least an order of magnitude higher. Furthermore, the GC-GC/MS method could avoid the false negative and false positive results that appeared in the compared conventional GC/MS analysis. By trapping the vapor phase of 20 cigarettes smoke, the LODs and LOQs of the nitroalkanes were 1.3 to 9.8 and 4.3 to 32.6ng/cigarette, respectively, and all linear correlation efficiencies were larger than 0.999. The validation results also indicate that the method has high accuracy (spiked recoveries between 84% and 102%) and good repeatability (RSD between 7.2% and 9.4%). The developed method was applied to analyze 1 Kentucky reference cigarette (3R4F) and 10 Chinese commercial brands of cigarettes. The research results indicated that nitromethane, nitroethane, 2-nitropropane and 1-nitro-n-pentane were detected in mainstream cigarette smoke, but 1-nitro-n-butane and 2-nitropropane, which were reported by one previous study, were not detected in all cigarette samples. PMID:26603996

  12. Advanced Life Support Water Recycling Technologies Case Studies: Vapor Phase Catalytic Ammonia Removal and Direct Osmotic Concentration

    NASA Technical Reports Server (NTRS)

    Flynn, Michael

    2004-01-01

    Design for microgravity has traditionally not been well integrated early on into the development of advanced life support (ALS) technologies. NASA currently has a many ALS technologies that are currently being developed to high technology readiness levels but have not been formally evaluated for microgravity compatibility. Two examples of such technologies are the Vapor Phase Catalytic Ammonia Removal Technology and the Direct Osmotic Concentration Technology. This presentation will cover the design of theses two systems and will identify potential microgravity issues.

  13. Vapor phase strengthening of nickel-based alloys for actively-cooled thermostructural panels

    NASA Astrophysics Data System (ADS)

    Perez-Bergquist, Sara Jane

    Actively cooled thermostructural panels for use in emerging hypersonic flight systems require the use of advanced materials able to support substantial loads at elevated temperatures. A major challenge in this advancing technology is identifying formable structural materials that are strong, tough and oxidation resistant. For thermostructural panels to be optimized for low mass with an appropriate combination of mechanical strength and cooling capacity, the panel is required to have a thin-walled geometry. Advanced, high strength cast Ni-based alloys have attractive properties, but the fabrication of sub-millimeter walls with conventional casting processes would be extremely challenging. The purpose of this study is to develop a new processing path that would result in a rectangular channeled panel made of a nickel-based precipitation strengthened alloy in a previously unobtainable thin-walled geometry suitable for active cooling. Beginning with thin sheets of Ni-based solid-solution alloys and subsequently strengthening the material by vapor phase aluminization combined with an annealing treatment, this objective is accomplished. This study includes selecting a wrought nickel-based alloy as the base substrate for panel fabrication, determining a goal gamma + gamma' microstructure, fabricating rectangular channeled panels, and testing the actively cooled panels at high temperature. Thermodynamic, yield strength, and panel geometry modeling was integrated to determine an optimized geometry and microstructure for the strengthened panel. Panels were fabricated with the optimized geometry and tested at high temperature with active cooling in both the as-fabricated and strengthened states. The strengthened panel was able to withstand a temperature 478°C higher than the as-fabricated panel indicating the increase in strengthening and temperature capability possible with this process.

  14. Matrix Isolation Studies of Carbonic AcidThe Vapor Phase above the ?-Polymorph

    PubMed Central

    2013-01-01

    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 (C2v and Cs). In contrast to the earlier study on ?-H2CO3, we do not find evidence for centrosymmetric (C2h) 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

  15. Mw Spectroscopy Coupled with Ultrafast UV Laser Vaporization: {RIBOSE} Found in the Gas Phase

    NASA Astrophysics Data System (ADS)

    Cocinero, Emilio J.; Ecija, Patricia; Basterretxea, Francisco J.; Fernandez, Jose A.; Castano, Fernando; Lesarri, Alberto; Grabow, Jens-Uwe

    2012-06-01

    Sugars are aldoses or ketoses with multiple hydroxy groups which have been elusive to spectroscopic studies. Here we report a rotational study of the aldopentose ribose. According to any standard textbook aldopentoses can exhibit either linear forms, cyclic five-membered (furanose) structures or six-membered (pyranose) rings, occurring either as ?- or ?- anomers depending on the orientation of the hydroxy group at C-1 (anomeric carbon). ?-Furanose is predominant in ribonucleosides, RNA, ATP and other biochemically relevant derivatives, but is ?-furanose the native form also of free ribose? Recent condensed-phase X-ray and older NMR studies delivered conflicting results. In order to solve this question we conducted a microwave study on D-ribose that, owing to ultrafast UV laser vaporization, has become the first C-5 sugar observed with rotational resolution. The spectrum revealed six conformations of free ribose, preferentially adopting ?-pyranose chairs as well as higher-energy ?-pyranose forms. The method also allowed for unambiguous distinction between different orientations of the hydroxy groups, which stabilize the structures by cooperative hydrogen-bond networks. No evidence was observed of the ?-/?-furanoses or linear forms found in the biochemical derivatives. i) D. iak, L. B. McCusker, G. Zandomeneghi, B. H. Meier, D. Blser, R. Boese, W. B. Schweizer, R. Gylmour and J. D. Dunitz Angew. Chem. Int. Ed. 49, 4503, 2010. ii) W. Saenger Angew. Chem. Int. Ed. 49, 6487, 2010. i) M. Rudrum, and D. F. Shaw, J. Chem. Soc. 52, 1965. ii) R. U. Lemieux and J. D. Stevens Can. J. Chem. 44, 249, 1966. iii) E. Breitmaier and U. Hollstein Org. Magn. Reson. 8, 573, 1976. E. J. Cocinero, A. Lesarri, P. cija, F. J. Basterretxea, J. U. Grabow, J. A. Fernndez and F. Castao Angew. Chem. Int. Ed. in press: DOI: 10.1002/anie.201107973, 2012.

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

    NASA Astrophysics Data System (ADS)

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

    2011-07-01

    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 ( [1 0 1 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 11010 to 3108 cm-2 and the stacking fault density is reduced from 1106 to 4104 cm-1. Threading dislocations (TDs) are observed in the ELO mask openings with screw and mixed characters which have Burgers vectors b?={1}/{3}[1 1 2 0] and b?={1}/{3}[1 1 2 3] respectively. In the ELO areas, three kind of dislocations are observed: screw dislocations with b?={1}/{3}[1 1 2 0], edge dislocations with b?={1}/{3}[2 1 1 0] and partial dislocations (PDs) with b?={1}/{3}[1 0 1 0] and b?={1}/{6}[2 0 2 3]. Basal stacking faults (BSFs) of the type I1 ( R?={1}/{6}[2 0 2 3]) and I2 ( R?={1}/{3}[1 0 1 0]), and prismatic stacking faults (PSFs) with a R?={1}/{2}[1 1 0 1] are also observed. Cathodoluminescence, spectra and imaging, has shown that TDs are non-radiative recombination centers contrary to BSFs.

  17. Investigation of vapor-phase lubrication in a gas turbine engine

    SciTech Connect

    Van Treuren, K.W.; Barlow, D.N.; Heiser, W.H.; Wagner, M.J.; Forster, N.H.

    1998-04-01

    The liquid oil lubrication system of current aircraft jet engines accounts for approximately 10--15% of the total weight of the engine. It has long been a goal of the aircraft gas turbine industry to reduce this weight. Vapor-Phase Lubrication (VPL) is a promising technology to eliminate liquid oil lubrication. The current investigation resulted in the first gas turbine to operate in the absence of conventional liquid lubrication. A phosphate ester, commercially known as DURAD 620B, was chosen for the test. Extensive research at Wright Laboratory demonstrated that this lubricant could reliably lubricate rolling element bearings in the gas turbine engine environment. The Allison T63 engine was selected as the test vehicle because of its small size and bearing configuration. Specifically, VPL was evaluated in the number eight bearing because it is located in a relatively hot environment, in line with the combustor discharge, and it can be isolated from the other bearings and the liquid lubrication system. The bearing was fully instrumented and its performance with standard oil lubrication was documented. Results of this baseline study were used to develop a thermodynamic model to predict the bearing temperature with VPL. The engine was then operated at a ground idle condition with VPL with the lubricant misted into the No. 8 bearing at 13 ml/h. The bearing temperature stabilized at 283 C within 10 minutes. Engine operation was continued successfully for a total of one hour. No abnormal wear of the rolling contact surfaces was found when the bearing was later examined. Bearing temperatures after engine shutdown indicated the bearing had reached thermodynamic equilibrium with its surroundings during the test.

  18. TREATMENT OF PRODUCED WATERS USING A SURFACTANT MODIFIED ZEOLITE/VAPOR PHASE BIOREACTOR SYSTEM

    SciTech Connect

    Lynn E. Katz; Kerry A. Kinney; R.S. Bowman; E.J. Sullivan

    2003-04-01

    Co-produced water from the oil and gas industry accounts for a significant waste stream in the United States. It is by some estimates the largest single waste stream in the country, aside from nonhazardous industrial wastes. Characteristics of produced water include high total dissolved solids content, dissolved organic constituents such as benzene and toluene, an oil and grease component, and chemicals added during the oil-production process. While most of the produced water is disposed via reinjection, some of them must be treated to remove organic constituents before the water is discharged. Current treatment options are successful in reducing the organic content; however, they cannot always meet the levels of current or proposed regulations for discharged water. Therefore, an efficient, cost-effective treatment technology is needed. Surfactant-modified zeolite (SMZ) has been used successfully to treat contaminated ground water for organic and inorganic constituents. In addition, the low cost of natural zeolites makes their use attractive in water-treatment applications. Our previous DOE research work (DE-AC26-99BC15221) demonstrated that SMZ could successfully remove BTEX compounds from the produced water. In addition, SMZ could be regenerated through a simple air sparging process. The primary goal of this project is to develop a robust SMZ/VPB treatment system to efficiently remove the organic constituents from produced water in a cost-effective manner. This report summarizes work of this project from October 2002 to March 2003. In this starting stage of this study, we have continued our investigation of SMZ regeneration from our previous DOE project. Two saturation/stripping cycles have been completed for SMZ columns saturated with BTEX compounds. Preliminary results suggest that BTEX sorption actually increases with the number of saturation/regeneration cycles. Furthermore, the experimental vapor phase bioreactors for this project have been designed and are currently being assembled to treat the off-gas from the SMZ regeneration process.

  19. Solid-State, Dye-Labeled DNA Detects Volatile Compounds in the Vapor Phase

    PubMed Central

    White, Joel; Truesdell, Kathleen; Williams, Lloyd B; AtKisson, Mary S; Kauer, John S

    2008-01-01

    This paper demonstrates a previously unreported property of deoxyribonucleic acid—the ability of dye-labeled, solid-state DNA dried onto a surface to detect odors delivered in the vapor phase by changes in fluorescence. This property is useful for engineering systems to detect volatiles and provides a way for artificial sensors to emulate the way cross-reactive olfactory receptors respond to and encode single odorous compounds and mixtures. Recent studies show that the vertebrate olfactory receptor repertoire arises from an unusually large gene family and that the receptor types that have been tested so far show variable breadths of response. In designing biomimetic artificial noses, the challenge has been to generate a similarly large sensor repertoire that can be manufactured with exact chemical precision and reproducibility and that has the requisite combinatorial complexity to detect odors in the real world. Here we describe an approach for generating and screening large, diverse libraries of defined sensors using single-stranded, fluorescent dye–labeled DNA that has been dried onto a substrate and pulsed with brief exposures to different odors. These new solid-state DNA-based sensors are sensitive and show differential, sequence-dependent responses. Furthermore, we show that large DNA-based sensor libraries can be rapidly screened for odor response diversity using standard high-throughput microarray methods. These observations describe new properties of DNA and provide a generalized approach for producing explicitly tailored sensor arrays that can be rationally chosen for the detection of target volatiles with different chemical structures that include biologically derived odors, toxic chemicals, and explosives. PMID:18215112

  20. Polycrystalline indium phosphide on silicon by indium assisted growth in hydride vapor phase epitaxy

    SciTech Connect

    Metaferia, Wondwosen; Sun, Yan-Ting Lourdudoss, Sebastian; Pietralunga, Silvia M.; Zani, Maurizio; Tagliaferri, Alberto

    2014-07-21

    Polycrystalline InP was grown on Si(001) and Si(111) substrates by using indium (In) metal as a starting material in hydride vapor phase epitaxy (HVPE) reactor. In metal was deposited on silicon substrates by thermal evaporation technique. The deposited In resulted in islands of different size and was found to be polycrystalline in nature. Different growth experiments of growing InP were performed, and the growth mechanism was investigated. Atomic force microscopy and scanning electron microscopy for morphological investigation, Scanning Auger microscopy for surface and compositional analyses, powder X-ray diffraction for crystallinity, and micro photoluminescence for optical quality assessment were conducted. It is shown that the growth starts first by phosphidisation of the In islands to InP followed by subsequent selective deposition of InP in HVPE regardless of the Si substrate orientation. Polycrystalline InP of large grain size is achieved and the growth rate as high as 21 μm/h is obtained on both substrates. Sulfur doping of the polycrystalline InP was investigated by growing alternating layers of sulfur doped and unintentionally doped InP for equal interval of time. These layers could be delineated by stain etching showing that enough amount of sulfur can be incorporated. Grains of large lateral dimension up to 3 μm polycrystalline InP on Si with good morphological and optical quality is obtained. The process is generic and it can also be applied for the growth of other polycrystalline III–V semiconductor layers on low cost and flexible substrates for solar cell applications.

  1. Characterization of vapor phase mercury released from concrete processing with baghouse filter dust added cement.

    PubMed

    Wang, Jun; Hayes, Josh; Wu, Chang-Yu; Townsend, Timothy; Schert, John; Vinson, Tim; Deliz, Katherine; Bonzongo, Jean-Claude

    2014-02-18

    The fate of mercury (Hg) in cement processing and products has drawn intense attention due to its contribution to the ambient emission inventory. Feeding Hg-loaded coal fly ash to the cement kiln introduces additional Hg into the kiln's baghouse filter dust (BFD), and the practice of replacing 5% of cement with the Hg-loaded BFD by cement plants has recently raised environmental and occupational health concerns. The objective of this study was to determine Hg concentration and speciation in BFD as well as to investigate the release of vapor phase Hg from storing and processing BFD-added cement. The results showed that Hg content in the BFD from different seasons ranged from 0.91-1.44 mg/kg (ppm), with 62-73% as soluble inorganic Hg, while Hg in the other concrete constituents were 1-3 orders of magnitude lower than the BFD. Up to 21% of Hg loss was observed in the time-series study while storing the BFD in the open environment by the end of the seventh day. Real-time monitoring in the bench system indicated that high temperature and moisture can facilitate Hg release at the early stage. Ontario Hydro (OH) traps showed that total Hg emission from BFD is dictated by the air exchange surface area. In the bench simulation of concrete processing, only 0.4-0.5% of Hg escaped from mixing and curing BFD-added cement. A follow-up headspace study did not detect Hg release in the following 7 days. In summary, replacing 5% of cement with the BFD investigated in this study has minimal occupational health concerns for concrete workers, and proper storing and mixing of BFD with cement can minimize Hg emission burden for the cement plant. PMID:24444016

  2. Planarization and Processing of Metamorphic Buffer Layers Grown by Hydride Vapor-Phase Epitaxy

    NASA Astrophysics Data System (ADS)

    Zutter, Brian T.; Schulte, Kevin L.; Kim, Tae Wan; Mawst, Luke J.; Kuech, T. F.; Foran, Brendan; Sin, Yongkun

    2014-04-01

    Hydride vapor-phase epitaxy (HVPE) is a high-growth-rate, cost-effective means to grow epitaxial semiconductor material. Thick HVPE-based metamorphic buffer layers (MBLs) can serve as "pseudosubstrates" with controllable lattice parameter. In our structures, the indium content in In x Ga1- x As is gradually increased from zero to the final composition corresponding to the desired lattice constant, and then a thick (˜10 μm) constant-composition capping layer is grown. This thick capping layer promotes maximum strain relaxation while permitting use of polishing procedures to achieve surface planarity. Lattice-mismatched growth of MBLs invariably results in rough, cross-hatched surface morphology exhibiting up to 200 nm peak-to-valley roughness. This roughness can be eliminated by chemical mechanical planarization, thus creating a suitable surface for subsequent regrowth. Polishing of In x Ga1- x As is complicated by the sensitivity of the surface layer to the polishing parameters, particularly the applied pressure. Polishing at high applied pressure (12 psi) results in the formation of circular asperities hundreds of nanometers high and tens of microns in diameter. When lower applied pressure (4 psi) was used, the cross-hatching height of MBLs was lowered from 200 nm to <10 nm over a 350 μm lateral scale. The successfully planarized In0.20Ga0.80As MBLs were used as a substrate for a superlattice (SL) structure such as that used in quantum cascade lasers. Use of planarization before regrowth of the SL resulted in a reduction of the high-resolution x-ray diffraction peak full-width at half-maximum from 389″ to 159″.

  3. NOVEL CERAMIC-ORGANIC VAPOR PERMEATION MEMBRANES FOR VOC REMOVAL - PHASE II

    EPA Science Inventory

    Vapor permeation with highly permeable and organic-selective membranes is becoming an increasingly popular technique for preventing VOC emissions that are generated by a variety of stationary sources, including solvent and surface coating operations, gasoline storage operat...

  4. NOVEL CERAMIC-ORGANIC VAPOR PERMEATION MEMBRANES FOR VOC REMOVAL - PHASE I

    EPA Science Inventory

    Vapor permeation holds much promise for becoming a highly efficient means of preventing VOC emissions that are now generated by a variety of stationary sources, including solvent and surface coating operations, gasoline storage operations, and printing operations. A limitation of...

  5. VAPOR PHASE MERCURY SORPTION BY ORGANIC SULFIDE MODIFIED BIMETALLIC IRON-COPPER NANOPARTICLE AGGREGATES

    EPA Science Inventory

    Novel organic sulfide modified bimetallic iron-copper nanoparticle aggregate sorbent materials have been synthesized for removing elemental mercury from vapor streams at elevated temperatures (120-140 C). Silane based (disulfide silane and tetrasulfide silane) and alkyl sulfide ...

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

    PubMed

    Raabe, Gabriele; Sadus, Richard J

    2007-01-28

    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

  7. An Experimental Visualization and Image Analysis of Electrohydrodynamically Induced Vapor-Phase Silicon Oil Flow under DC Corona Discharge

    NASA Astrophysics Data System (ADS)

    Ohyama, Ryu-Ichiro; Fukumoto, Masaru

    A DC corona discharge induced electrohydrodynamic (EHD) flow phenomenon for a multi-phase fluid containing a vapor-phase dielectric liquid in the fresh air was investigated. The experimental electrode system was a simple arrangement of needle-plate electrodes for the corona discharges and high-resistivity silicon oil was used as the vapor-phase liquid enclosure. The qualitative observation of EHD flow patterns was conducted by an optical processing on computer tomography and the time-series of discharge current pulse generations at corona discharge electrode were measured simultaneously. These experimental results were analyzed in relationship between the EHD flow motions and the current pulse generations in synchronization. The current pulses and the EHD flow motions from the corona discharge electrode presented a continuous mode similar to the ionic wind in the fresh air and an intermittent mode. In the intermittent mode, the observed EHD flow motion was synchronized with the separated discharge pulse generations. From these experimental results, it was expected that the existence of silicon oil vapor trapped charges gave an occasion to the intermittent generations of the discharge pulses and the secondary EHD flow.

  8. An Evaluation of the Vapor Phase Catalytic Ammonia Removal Process for Use in a Mars Transit Vehicle

    NASA Technical Reports Server (NTRS)

    Flynn, Michael; Borchers, Bruce

    1998-01-01

    An experimental program has been developed to evaluate the potential of the Vapor Phase Catalytic Ammonia Reduction (VPCAR) technology for use as a Mars Transit Vehicle water purification system. Design modifications which will be required to ensure proper operation of the VPCAR system in reduced gravity are also evaluated. The VPCAR system is an integrated wastewater treatment technology that combines a distillation process with high temperature catalytic oxidation. The distillation portion of the system utilizes a vapor compression distillation process to provide an energy efficient phase change separation. This portion of the system removes any inorganic salts and large molecular weight, organic contaminates, i.e., non-volatile, from the product water stream and concentrates these contaminates into a byproduct stream. To oxidize the volatile organic compounds and ammonia, a vapor phase, high temperature catalytic oxidizer is used. This catalytic system converts these compounds along with the aqueous product into CO2, H2O, and N2O. A secondary catalytic bed can then be used to reduce the N2O to nitrogen and oxygen (although not evaluated in this study). This paper describes the design specification of the VPCAR process, the relative benefits of its utilization in a Mars Transit Vehicle, and the design modification which will be required to ensure its proper operation in reduced gravity. In addition, the results of an experimental evaluation of the processors is presented. This evaluation presents the processors performance based upon product water purity, water recovery rates, and power.

  9. Vapor phase synthesis of compound semiconductors, from thin films to nanoparticles

    NASA Astrophysics Data System (ADS)

    Sarigiannis, Demetrius

    A counterflow jet reactor was developed to study the gas-phase decomposition kinetics of organometallics used in the vapor phase synthesis of compound semiconductors. The reactor minimized wall effects by generating a reaction zone near the stagnation point of two vertically opposed counterflowing jets. Smoke tracing experiments were used to confirm the stability of the flow field and validate the proposed heat, mass and flow models of the counterflow jet reactor. Transport experiments using ethyl acetate confirmed the overall mass balance for the system and verified the ability of the model to predict concentrations at various points in the reactor under different flow conditions. Preliminary kinetic experiments were performed with ethyl acetate and indicated a need to redesign the reactor. The counterflow jet reactor was adapted for the synthesis of ZnSe nanoparticles. Hydrogen selenide was introduced through one jet and dimethylzinc-triethylamine through the other. The two precursors reacted in a region near the stagnation zone and polycrystalline particles of zinc selenide were reproducibly synthesized at room temperature and collected for analysis. Raman spectroscopy confirmed that the particles were crystalline zinc selenide, Morphological analysis using SEM clearly showed the presence of aggregates of particles, 40 to 60 nanometers in diameter. Analysis by TEM showed that the particles were polycrystalline in nature and composed of smaller single crystalline nanocrystallites, five to ten nanometers in diameter. The particles in the aggregate had the appearance of being sintered together. To prevent this sintering, a split inlet lower jet was designed to introduce dimethylzinc through the inner tube and a surface passivator through the outer one. This passivating agent appeared to prevent the particles from agglomerating. An existing MOVPE reactor for II-VI thin film growth was modified to grow III-V semiconductors. A novel new heater was designed and built around an easily replaceable, economical, 650-watt, tungsten-halogen lamp. The heater was successfully tested to temperatures up to 1500F. The deposition reactor was successfully tested by growing a thin film of GaP on GaAs <100>. The film surface was imperfect but the experiments proved that the reactor was ready for service.

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

    PubMed

    Chapela, Gustavo A; de Ro, Fernando; Alejandre, Jos

    2011-06-14

    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 ?(2)/?(1) 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 T(c) when plotted against ?(2) as follows. At lower values of ?(2), an increase of T(c) is obtained as is expected by the increase of the attractive volume as indicated by the principle of corresponding states. As ?(2) 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 T(c) 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. PMID:21682505

  11. Influence of mass diffusion on the stability of thermophoretic growth of a solid from the vapor phase

    NASA Technical Reports Server (NTRS)

    Castillo, J. L.; Garcia-Ybarra, P. L.; Rosner, D. E.

    1991-01-01

    The stability of solid planar growth from a binary vapor phase with a condensing species dilute in a carrier gas is examined when the ratio of depositing to carrier species molecular mass is large and the main diffusive transport mechanism is thermal diffusion. It is shown that a deformation of the solid-gas interface induces a deformation of the gas phase isotherms that increases the thermal gradients and thereby the local mass deposition rate at the crests and reduces them at the valleys. The initial surface deformation is enhanced by the modified deposition rates in the absence of appreciable Fick/Brownian diffusion and interfacial energy effects.

  12. Adolescent Males’ Awareness of and Willingness to Try Electronic Cigarettes

    PubMed Central

    Pepper, Jessica K.; Reiter, Paul L.; McRee, Annie-Laurie; Cameron, Linda D.; Gilkey, Melissa B.; Brewer, Noel T.

    2012-01-01

    Purpose Electronic cigarettes (e-cigarettes) are a new type of device that delivers vaporized nicotine without the tobacco combustion of regular cigarettes. We sought to understand awareness of and willingness to try e-cigarettes among adolescent males, a group that is at risk for smoking initiation and may use e-cigarettes as a “gateway” to smoking. Methods A national sample of 11–19-year-old males (n =228) completed an online survey in November 2011. We recruited participants through their parents, who were members of a panel of U.S. households constructed using random-digit dialing and addressed-based sampling. Results Only two participants (< 1%) had previously tried e-cigarettes. Among those who had not tried e-cigarettes, most (67%) had heard of them. Awareness was higher among older and non- Hispanic adolescents. Nearly 1 in 5 (18%) participants were willing to try either a plain or flavored e-cigarette, but willingness to try plain versus flavored varieties did not differ. Smokers were more willing to try any e-cigarette than nonsmokers (74% vs. 13%; OR 10.25, 95% CI 2.88, 36.46). Nonsmokers who had more negative beliefs about the typical smoker were less willing to try e-cigarettes (OR .58, 95% CI .43, .79). Conclusions Most adolescent males were aware of e-cigarettes, and a substantial minority were willing to try them. Given that even experimentation with e-cigarettes could lead to nicotine dependence and subsequent use of other tobacco products, regulatory and behavioral interventions are needed to prevent “gateway” use by adolescent nonsmokers. Campaigns promoting negative images of smokers or FDA bans on sales to youth may help deter use. PMID:23332477

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

    SciTech Connect

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

    2010-10-01

    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.

  14. Perceived efficacy of e-cigarettes versus nicotine replacement therapy among successful e-cigarette users: a qualitative approach

    PubMed Central

    2013-01-01

    Background Nicotine is widely recognized as an addictive psychoactive drug. Since most smokers are bio-behaviorally addicted, quitting can be very difficult and is often accompanied by withdrawal symptoms. Research indicates that nicotine replacement therapy (NRT) can double quit rates. However, the success rate for quitting remains low. E-cigarettes (electronic cigarettes) are battery-powered nicotine delivery devices used to inhale doses of vaporized nicotine from a handheld device similar in shape to a cigarette without the harmful chemicals present in tobacco products. Anecdotal evidence strongly suggests that e-cigarettes may be effective in helping smokers quit and preventing relapse, but there have been few published qualitative studies, especially among successful e-cigarette users, to support this evidence. Methods Qualitative design using focus groups (N?=?11); 9 men and 2 women. Focus groups were conducted by posing open-ended questions relating to the use of e-cigarettes, comparison of effectiveness between NRTs and e-cigarettes, barriers to quitting, and reasons for choosing e-cigarettes over other methods. Results Five themes emerged that describe users perceptions of why e-cigarettes are efficacious in quitting smoking: 1) bio-behavioral feedback, 2) social benefits, 3) hobby elements, 4) personal identity, and 5) distinction between smoking cessation and nicotine cessation. Additionally, subjects reported their experiences with NRTs compared with e-cigarettes, citing negative side effects of NRTs and their ineffectiveness at preventing relapse. Conclusion These findings suggest tobacco control practitioners must pay increased attention to the importance of the behavioral and social components of smoking addiction. By addressing these components in addition to nicotine dependence, e-cigarettes appear to help some tobacco smokers transition to a less harmful replacement tool, thereby maintaining cigarette abstinence. PMID:23497603

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

    SciTech Connect

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

    2005-03-11

    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.

  16. Magmatic Vapor Phase Transport of Copper in Reduced Porphyry Copper-Gold Deposits: Evidence From PIXE Microanalysis of Fluid Inclusions

    NASA Astrophysics Data System (ADS)

    Rowins, S. M.; Yeats, C. J.; Ryan, C. G.

    2002-05-01

    Nondestructive proton-induced X-ray emission (PIXE) studies of magmatic fluid inclusions in granite-related Sn-W deposits [1] reveal that copper transport out of reduced felsic magmas is favored by low-salinity vapor and not co-existing high-salinity liquid (halite-saturated brine). Copper transport by magmatic vapor also has been documented in oxidized porphyry Cu-Au deposits, but the magnitude of Cu partitioning into the vapor compared to the brine generally is less pronounced than in the reduced magmatic Sn-W systems [2]. Consideration of these microanalytical data leads to the hypothesis that Cu and, by inference, Au in the recently established "reduced porphyry copper-gold" (RPCG) subclass should partition preferentially into vapor and not high-salinity liquid exsolving directly from fluid-saturated magmas [3-4]. To test this hypothesis, PIXE microanalysis of primary fluid inclusions in quartz-sulfide (pyrite, pyrrhotite & chalcopyrite) veins from two RPCG deposits was undertaken using the CSIRO-GEMOC nuclear microprobe. PIXE microanalysis for the ~30 Ma San Anton deposit (Mexico) was done on halite-saturated aqueous brine (<10 vol.% vapor) and co-existing low-salinity aqueous vapor (<20 vol.% liquid) inclusions. Results indicate that vapor inclusions have higher concentrations of Cu (typically 1000's of ppm; max. 7277 ppm) compared to brine inclusions (typically 100's of ppm). Brine inclusions also are much higher in Cl (Na), K, Ca, Mn, Zn, and Fe. Only Pb concentrations approach those in the vapor. Metal ratios such as Cu/Fe and Cu/Zn are 2 to 167 times higher in the vapor compared with the brine inclusions. Cu/Pb ratios are 2 to 15 times higher in the vapor than in the brine. PIXE microanalysis for the ~617 Ma 17 Mile Hill deposit (W. Australia) was done on halite-saturated "aqueous" inclusions, which contain a small (<10 vol.%) bubble of carbonic fluid, and adjacent "carbonic" inclusions, which have a thin rim of aqueous liquid (<10 vol.%) wetting the walls of the inclusion [3,5]. Results indicate that carbonic inclusions possess higher concentrations of Cu (47 to 2387 ppm; mean 453 ppm) compared to aqueous inclusions (5 to 190 ppm; mean 50 ppm). The aqueous inclusions also are much higher in Cl (Na), K, Ca, and Mn, but have similar abundances of Fe, Zn, and Pb. The metal ratios Cu/Fe, Cu/Zn, and Cu/Pb are 2 to 22 times higher in the carbonic inclusions than in the aqueous inclusions. Interpretation of these 17 Mile Hill PIXE data, however, requires some caution because carbonic and aqueous inclusions in a different grain of quartz from the same vein have similarly low concentrations of Cu (38 to 928 ppm), Fe (152 to 1168 ppm), Zn (26 to 162 ppm) and Pb (121 to 914 ppm). For these inclusions, the preferential partitioning of metals apparently has not occurred. These first PIXE data for deposits of the new RPCG subclass demonstrate the greater potential of these systems, compared to the classically oxidized porphyry Cu-Au systems, to transport Cu and probably precious metals in a magmatic aqueous vapor phase. These PIXE data also support the possibility that Cu partitions preferentially into an immiscible CO2-rich magmatic fluid. References: [1] Heinrich, C.A. et al. (1992) Econ. Geol., 87, 1566-1583. [2] Heinrich, C.A. et al. (1999) Geology, 27, 755-758. [3] Rowins, S.M. (2000) Geology, 28, 491-494. [4] Rowins, S.M. (2000) The Gangue, GAC-MDD Newsletter, 67, 1-7 (www.gac.ca). [5] Rowins, S.M. et al. (1993) Geol. Soc. Australia Abs., 34, 68-70.

  17. TREATMENT OF PRODUCED WATERS USING A SURFACTANT MODIFIED ZEOLITE/VAPOR PHASE BIOREATOR SYSTEM

    SciTech Connect

    LYNN E. KATZ; KERRY A. KINNEY; R.S. BOWMAN; E.J. SULLIVAN

    2003-10-01

    Co-produced water from the oil and gas industry is by some estimates the largest single waste stream in the country, aside from nonhazardous industrial wastes. Characteristics of produced water include high total dissolved solids content, dissolved organic constituents such as benzene and toluene, an oil and grease component, and chemicals added during the oil-production process. While most of the produced water is disposed via reinjection, some of them must be treated to remove organic constituents before the water is discharged. An efficient, cost-effective treatment technology is needed to remove these constituents. Surfactant-modified zeolite (SMZ) has been used successfully to treat contaminated ground water for organic and inorganic constituents. In addition, the low cost of natural zeolites makes their use attractive in water-treatment applications. Our previous DOE research work (DE-AC26-99BC15221) demonstrated that SMZ could successfully remove BTEX compounds from the produced water. In addition, SMZ could be regenerated through a simple air sparging process. The primary goal of this project is to develop a robust SMZ/VPB treatment system to efficiently remove the organic constituents from produced water in a cost-effective manner. This report summarizes work of this project from March 2003 through September 2003. We have continued our investigation of SMZ regeneration from our previous DOE project. Ten saturation/stripping cycles have been completed for SMZ columns saturated with BTEX compounds. The results suggest that BTEX sorption capacity is not lost after ten saturation/regeneration cycles. The composition of produced water from a site operated by Crystal Solutions Ltd. in Wyoming has been characterized and was used to identify key semi-volatile components. Isotherms with selected semi-volatile components have been initiated and preliminary results have been obtained. The experimental vapor phase bioreactors for this project have been designed and assembled to treat the off-gas from the SMZ regeneration process. These columns will be used both in the laboratory and in the proposed field testing to be conducted next year. Innocula for the columns that degrade all of the BTEX columns have been developed.

  18. Treatment of Produced Water Using a Surfactant Modified Zeolite/Vapor Phase Bioreactor System

    SciTech Connect

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

    2006-01-31

    Co-produced water from the oil and gas industry accounts for a significant waste stream in the United States. Produced waters typically contain a high total dissolved solids content, dissolved organic constituents such as benzene and toluene, an oil and grease component as well as chemicals added during the oil-production process. It has been estimated that a total of 14 billion barrels of produced water were generated in 2002 from onshore operations (Veil, 2004). Although much of this produced water is disposed via reinjection, environmental and cost considerations can make surface discharge of this water a more practical means of disposal. In addition, reinjection is not always a feasible option because of geographic, economic, or regulatory considerations. In these situations, it may be desirable, and often necessary from a regulatory viewpoint, to treat produced water before discharge. It may also be feasible to treat waters that slightly exceed regulatory limits for re-use in arid or drought-prone areas, rather than losing them to reinjection. A previous project conducted under DOE Contract DE-AC26-99BC15221 demonstrated that surfactant modified zeolite (SMZ) represents a potential treatment technology for produced water containing BTEX. Laboratory and field experiments suggest that: (1) sorption of benzene, toluene, ethylbenzene and xylenes (BTEX) to SMZ follows linear isotherms in which sorption increases with increasing solute hydrophobicity; (2) the presence of high salt concentrations substantially increases the capacity of the SMZ for BTEX; (3) competitive sorption among the BTEX compounds is negligible; and, (4) complete recovery of the SMZ sorption capacity for BTEX can be achieved by air sparging the SMZ. This report summarizes research for a follow on project to optimize the regeneration process for multiple sorption/regeneration cycles, and to develop and incorporate a vapor phase bioreactor (VPB) system for treatment of the off-gas generated during air sparging. To this end, we conducted batch and column laboratory SMZ and VPB experiments with synthetic and actual produced waters. Based on the results of the laboratory testing, a pilot scale study was designed and conducted to evaluate the combined SMZ/VPB process. An economic and regulatory feasibility analysis was also completed as part of the current study to assess the viability of the process for various water re-use options.

  19. Kinetics of vapor-phase hydrogenation of furfural on a copper-chromium catalyst

    SciTech Connect

    Borts, M.S.; Gil'chenok, N.D.; Gurevich, G.S.; Ignat'ev, V.M.

    1986-08-01

    This paper studies the principal kinetic relationships of hydrogenation of furfural to furfuryl alcohol, which must be known for development of the industrial process. Prelininary experiments showed that at linear velocities of the vapor-gas stream (calculated for the free cross section of the reactor) above 0.26 matsec and with an average catalyst particle size less than 0.30 mm neither external nor internal diffusio resistance has any effect. In all the subsequent experiments a 0.20-0.25-mm catalyst fraction was used at a linear vapor-gas velocity of 0.50 m/sec, when the reaction proceeded with kinetic control.

  20. Theoretical approaches and experimental evidence for liquid-vapor phase transitions in nuclei

    SciTech Connect

    Moretto, L.G.; Elliott, J.B.; Phair, L.; Wozniak, G.J.; Mader, C.M.; Chappars, A.

    2001-01-01

    The leptodermous approximation is applied to nuclear systems for T > 0. The introduction of surface corrections leads to anomalous caloric curves and to negative heat capacities in the liquid-gas coexistence region. Clusterization in the vapor is described by associating surface energy to clusters according to Fisher's formula. The three-dimensional Ising model, a leptodermous system par excellence, does obey rigorously Fisher's scaling up to the critical point. Multifragmentation data from several experiments including the ISiS and EOS Collaborations, as well as compound nucleus fragment emission at much lower energy follow the same scaling, thus providing the strongest evidence yet of liquid-vapor coexistence.

  1. Integrated natural-gas-engine cooling jacket vapor-compressor program. Annual progress report (phase 2), January-December 1987

    SciTech Connect

    DiBella, F.A.; Becker, F.

    1988-01-01

    A unique, alternative cogeneration system was designed that will provide an industrial or commercial energy user with high-pressure steam and electricity directly from a packaged cogeneration system. The Integrated Gas Engine Vapor Compression System concept includes an engine-generator set and a steam screw compressor that are mechanically integrated with the engine. The gas-fueled engine is ebulliently cooled, thus allowing its water jacket heat to be recovered in the form of low-pressure steam. This steam is then compressed by the steam compressor to a higher pressure, and when combined with the high-pressure steam generated in the engine's exhaust gas boiler it provides the end user with a more useable thermal energy source. Phase 1B of this project was completed in 1986 and consisted primarily of the procurement of equipment and the final design and assembly of a prototype integrated gas-engine vapor-compression system.

  2. Reversible Semiconducting-to-Metallic Phase Transition in Chemical Vapor Deposition Grown Monolayer WSe2 and Applications for Devices.

    PubMed

    Ma, Yuqiang; Liu, Bilu; Zhang, Anyi; Chen, Liang; Fathi, Mohammad; Shen, Chenfei; Abbas, Ahmad N; Ge, Mingyuan; Mecklenburg, Matthew; Zhou, Chongwu

    2015-07-28

    Two-dimensional (2D) semiconducting monolayer transition metal dichalcogenides (TMDCs) have stimulated lots of interest because they are direct bandgap materials that have reasonably good mobility values. However, contact between most metals and semiconducting TMDCs like 2H phase WSe2 are highly resistive, thus degrading the performance of field effect transistors (FETs) fabricated with WSe2 as active channel materials. Recently, a phase engineering concept of 2D MoS2 materials was developed, with improved device performance. Here, we applied this method to chemical vapor deposition (CVD) grown monolayer 2H-WSe2 and demonstrated semiconducting-to-metallic phase transition in atomically thin WSe2. We have also shown that metallic phase WSe2 can be converted back to semiconducting phase, demonstrating the reversibility of this phase transition. In addition, we fabricated FETs based on these CVD-grown WSe2 flakes with phase-engineered metallic 1T-WSe2 as contact regions and intact semiconducting 2H-WSe2 as active channel materials. The device performance is substantially improved with metallic phase source/drain electrodes, showing on/off current ratios of 10(7) and mobilities up to 66 cm(2)/Vs for monolayer WSe2. These results further suggest that phase engineering can be a generic strategy to improve device performance for many kinds of 2D TMDC materials. PMID:26125321

  3. Columnar jointing in vapor-phase-altered, non-welded Cerro Galán Ignimbrite, Paycuqui, Argentina

    USGS Publications Warehouse

    Wright, Heather M.; Lesti, Chiara; Cas, Ray A.F.; Porreca, Massimiliano; Viramonte, Jose G.; Folkes, Christopher B.; Giordano, Guido

    2011-01-01

    Columnar jointing is thought to occur primarily in lavas and welded pyroclastic flow deposits. However, the non-welded Cerro Galán Ignimbrite at Paycuqui, Argentina, contains well-developed columnar joints that are instead due to high-temperature vapor-phase alteration of the deposit, where devitrification and vapor-phase crystallization have increased the density and cohesion of the upper half of the section. Thermal remanent magnetization analyses of entrained lithic clasts indicate high emplacement temperatures, above 630°C, but the lack of welding textures indicates temperatures below the glass transition temperature. In order to remain below the glass transition at 630°C, the minimum cooling rate prior to deposition was 3.0 × 10−3–8.5 × 10−2°C/min (depending on the experimental data used for comparison). Alternatively, if the deposit was emplaced above the glass transition temperature, conductive cooling alone was insufficient to prevent welding. Crack patterns (average, 4.5 sides to each polygon) and column diameters (average, 75 cm) are consistent with relatively rapid cooling, where advective heat loss due to vapor fluxing increases cooling over simple conductive heat transfer. The presence of regularly spaced, complex radiating joint patterns is consistent with fumarolic gas rise, where volatiles originated in the valley-confined drainage system below. Joint spacing is a proxy for cooling rates and is controlled by depositional thickness/valley width. We suggest that the formation of joints in high-temperature, non-welded deposits is aided by the presence of underlying external water, where vapor transfer causes crystallization in pore spaces, densifies the deposit, and helps prevent welding.

  4. Comparison of the layer structure of vapor phase and leached SRL glass by use of AEM [analytical electron microscopy

    SciTech Connect

    Biwer, B.M.; Bates, J.K.; Abrajano, T.A. Jr.; Bradley, J.P.

    1989-12-31

    Test samples of 131 type glass that have been reacted for extended time periods in water vapor atmospheres of different relative humidities and in static leaching solution have been examined to characterize the reaction products. Analytical electron microscopy (AEM) was used to characterize the leached samples, and a complicated layer structure was revealed, consisting of phases that precipitate from solution and also form within the residual glass layer. The precipitated phases include birnes-site, saponite, and an iron species, while the intralayer phases include the U-Ti containing phase brannerite distributed within a matrix consisting of bands of an Fe rich montmorillonite clay. Comparison is made between samples leached at 40{degrees}C for 4 years with those leached at 90{degrees}C for 3-1/2 years. The samples reacted in water vapor were examined with scanning electron microscopy and show increasing reaction as both the relative humidity and time of reaction increases. These samples also contain a layered structure with reaction products on the glass surface. 15 refs., 5 figs.

  5. Determination of nicotine, tar, volatile organic compounds and carbonyls in mainstream cigarette smoke using a glass filter and a sorbent cartridge followed by the two-phase/one-pot elution method with carbon disulfide and methanol.

    PubMed

    Uchiyama, Shigehisa; Hayashida, Hideki; Izu, Rina; Inaba, Yohei; Nakagome, Hideki; Kunugita, Naoki

    2015-12-24

    We have developed a new analytical method for the determination of nicotine, tar, volatile organic compounds and carbonyls in main-stream cigarette smoke using a sorbent cartridge packed with Carboxen 572 (CX-572) and a Cambridge filter pad (CFP) followed by the two-phase/one-pot elution method. A CX-572 cartridge is installed between the intake of the CFP and the pump of the smoking machine. Gaseous compounds collected with the CX-572 cartridge and total particulate matter (TPM) collected with the CFP are coeluted simultaneously in the same vial and then analyzed by high-performance liquid chromatography (HPLC), gas chromatography-mass spectrometry (GC/MS) and gas chromatograph-thermal conductivity detector (GC/TCD). Carbonyl compounds are determined by adding derivatizing reagent (2,4-dinitrophenylhydrazine, DNPH) to the eluate followed by HPLC analysis. VOCs and nicotine are determined by GC/MS, and water is determined by GC/TCD. The same sample eluate solution is used for HPLC, GC/MS and GC/TCD analyses. As a result of measuring main-stream cigarette smoke generated from reference cigarettes, almost all carbonyl compounds and VOCs except formaldehyde were passed through a CFP and trapped in a CX-572 cartridge. 100% of nicotine, tar and TPM were trapped in a CFP. 50% of water and 53% of formaldehyde were trapped in a CFP. The one-pot data is almost equal to the sums of CFP (particulate matter) and CX-572 (gaseous compounds) data. The two-phase/one-pot elution method can simultaneously measure nicotine, tar, volatile organic compounds and carbonyl compounds in cigarette smoke with simple operation and small amounts of reagents. PMID:26653840

  6. Fully automated analysis of four tobacco-specific N-nitrosamines in mainstream cigarette smoke using two-dimensional online solid phase extraction combined with liquid chromatography-tandem mass spectrometry.

    PubMed

    Zhang, Jie; Bai, Ruoshi; Yi, Xiaoli; Yang, Zhendong; Liu, Xingyu; Zhou, Jun; Liang, Wei

    2016-01-01

    A fully automated method for the detection of four tobacco-specific nitrosamines (TSNAs) in mainstream cigarette smoke (MSS) has been developed. The new developed method is based on two-dimensional online solid-phase extraction-liquid chromatography-tandem mass spectrometry (SPE/LC-MS/MS). The two dimensional SPE was performed in the method utilizing two cartridges with different extraction mechanisms to cleanup disturbances of different polarity to minimize sample matrix effects on each analyte. Chromatographic separation was achieved using a UPLC C18 reversed phase analytical column. Under the optimum online SPE/LC-MS/MS conditions, N'-nitrosonornicotine (NNN), N'-nitrosoanatabine (NAT), N'-nitrosoanabasine (NAB), and 4-(methylnitrosamino)-1-(3-pyridyl)-1-butanone (NNK) were baseline separated with good peak shapes. This method appears to be the most sensitive method yet reported for determination of TSNAs in mainstream cigarette smoke. The limits of quantification for NNN, NNK, NAT and NAB reached the levels of 6.0, 1.0, 3.0 and 0.6pg/cig, respectively, which were well below the lowest levels of TSNAs in MSS of current commercial cigarettes. The accuracy of the measurement of four TSNAs was from 92.8 to 107.3%. The relative standard deviations of intra-and inter-day analysis were less than 5.4% and 7.5%, respectively. The main advantages of the method developed are fairly high sensitivity, selectivity and accuracy of results, minimum sample pre-treatment, full automation, and high throughput. As a part of the validation procedure, the developed method was applied to evaluate TSNAs yields for 27 top-selling commercial cigarettes in China. PMID:26695255

  7. Computational studies of the metalorganic vapor phase epitaxy (MOVPE) of III-V compound semiconductors

    NASA Astrophysics Data System (ADS)

    Theodoropoulos, Constantinos

    Although Metalorganic Vapor Phase Epitaxy (MOVPE) has emerged as the most versatile and cost-effective technique for the growth of virtually any compound semiconductor it is still hampered by the lack of ample kinetic information and by excessive experimental trial and error. Detailed reaction-transport models can help in gaining the necessary physicochemical insight and can lead to optimal reactor designs, producing uniform films and abrupt heterojunctions. Furthermore, accurate, low-order dynamic models of MOVPE are essential tools for the development of closed-loop control strategies. A kinetic model of the MOVPE of InP from trimethyl-indium and phosphine---including gas-phase and surface reactions---was constructed and coupled to a 2-dimensional transport model of the flow, heat and mass transfer in horizontal reactors. Unknown rate parameters were estimated by comparing predicted growth rates with experimental ones. A reduced kinetic mechanism able to accurately predict growth rates, with lower computational cost was extracted through sensitivity analysis and was used in parametric studies of the effects of operating conditions on film growth rates. The Low-Pressure MOVPE of GaAs from triethyl-gallium and arsine---a precursor combination that produces GaAs films with very low carbon contamination---was also studied. A kinetic model based on reported decomposition mechanisms was developed and coupled to a transport model of an experimental reactor. Finite Element (FEM) simulations were performed to estimate rate parameters of the growth reactions and to investigate the effects of surface chemistry and susceptor temperatures on film growth and uniformity. Robustness issues of reaction-transport models were addressed. The MOVPE of GaAs from trimethyl-gallium (TMG) and arsine was considered with the objective to construct reactor-independent models. A kinetic mechanism was extracted from reported kinetic studies and the frequency factor of the growth reaction was adjusted to match experimental observations from a rotating-disk (RD) reactor. The model was able to reproduce reported growth rates and uniformities from a horizontal reactor in 2- and 3-D FEM simulations, without further adjustments. A reaction-transport model of the MOVPE of GaN from TMG and ammonia in stagnation-flow and RD reactors was developed and employed in the design of axisymmetric gas inlets which feed precursors separately into the reactor to eliminate parasitic pre-reactions. FEM simulations were performed to identify designs that can lead to the growth of uniform films over large area substrates. Finally, a systematic method for order reduction of dynamic MOVPE models was demonstrated. Transients arise in MOVPE due to precursor switching during the growth of heterostructures. The Proper Orthogonal Decomposition (POD) method was employed to obtain accurate reduced models from full-scale FEM dynamic simulations of TMG dispersion in a horizontal MOVPE reactor. Reduced models can be coupled with in-situ probes of the growth and used for on-line, model-based feedback control, which is an essential step towards the realization of a Virtual MOVPE reactor.

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

    PubMed

    McGraw, Gregory J; Forrest, Stephen R

    2013-03-20

    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

  9. Development of vapor phase hydrogen peroxide sterilization process for spacecraft applications

    NASA Technical Reports Server (NTRS)

    Rohatgi, N.; Schubert, W.; Knight, J.; Quigley, M.; Forsberg, G.; Ganapathi, G.; Yarbrough, C.; Koukol, R.

    2001-01-01

    This paper will present test data and discussion on the work we are conducting at JPL to address the following issues: 1) efficacy of sterilization process; 2) diffusion of hydrogen peroxide under sterilization process conditions into hard to reach places; 3) materials and components compatibility with the sterilization process and 4) development of methodology to protect sensitive components from hydrogen peroxide vapor.

  10. VAPOR PHASE MERCURY SORPTION BY ORGANIC SULFIDE MODIFIED BIMETALLIC IRON-COPPER NANOPARTICLE AGGREGATES

    EPA Science Inventory

    Novel organic sulfide modified bimetallic iron-copper nanoparticle aggregate sorbent materials have been synthesized for removing elemental mercury from vapor streams at elevated temperatures (120-140 °C). Silane based (disulfide silane and tetrasulfide silane) and alkyl sulfide ...

  11. Effect of the vapor phase on the salinity of halite-bearing aqueous fluid inclusions estimated from the halite dissolution temperature

    NASA Astrophysics Data System (ADS)

    Steele-MacInnis, Matthew; Bodnar, Robert J.

    2013-08-01

    Salinities of aqueous fluid inclusions are commonly determined by measuring the temperatures of dissolution of solid phases (daughter minerals) during heating. The vapor bubble is, in most cases, considered to have no mass and to have no effect on the bulk salinity, owing to the low density of the vapor. In the present study we test the assumption that the vapor bubble can be ignored when estimating salinity based on the halite dissolution temperature. The errors in bulk salinity that result from neglecting the vapor bubble are generally less than 1.5 wt.% NaCl, and errors of this magnitude occur only when there is a large difference between the halite dissolution temperature and the vapor disappearance temperature (e.g., halite dissolution at 450 C and vapor bubble disappearance at 800 C) or, stated differently, when the vapor bubble occupies a significant volume fraction of the inclusion at the temperature of halite disappearance. In most cases errors are less than 0.5 wt.% NaCl. Salinity estimated based on Tm,H can be adjusted to account for the contribution of H2O from the vapor phase, using an empirical relationship describing the proportion of liquid in the inclusion at Tm,H as a function of the difference between Th,LV and Tm,H.

  12. Characterization of particulate and vapor phase polycyclic aromatic hydrocarbons in indoor and outdoor air of primary schools

    NASA Astrophysics Data System (ADS)

    Krugly, Edvinas; Martuzevicius, Dainius; Sidaraviciute, Ruta; Ciuzas, Darius; Prasauskas, Tadas; Kauneliene, Violeta; Stasiulaitiene, Inga; Kliucininkas, Linas

    2014-01-01

    The indoor air of schools is considered as one of the most important factors affecting the health of children. The aim of the presented research was to characterize polycyclic aromatic hydrocarbons (PAHs) in indoor and outdoor air of schools. The sampling campaign was conducted during the heating season of 2011/2012. Five primary schools from various urban settings in the city of Kaunas, Lithuania. 150 daily samples of particulate and vapor phases were collected during the sampling period. The ultrasonic extractions followed by the gas chromatography and mass spectroscopy (GS/MS) analyses were used for the determination of PAHs. The concentration of total PAHs in the PM2.5 fraction ranged from 20.3 to 131.1 ng m-3, while total suspended particles (TSP) fraction contained from 19.9 to 80.3 ng m-3 of total PAHs. The vapor phase concentration of PAHs ranged from 67.2 to 372.5 ng m-3. The most abundant PAH in both phases was naphthalene. In order to define sources of indoor and outdoor PAHs several source apportionment methods were applied. The analysis revealed that emissions from motor vehicles and fuel burning for heating purposes were the major sources of PAHs in the city of Kaunas.

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

    PubMed

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

    2013-12-01

    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

  14. Defect Structures of AlN on Sapphire (0001) Grown by Metalorganic Vapor-Phase Epitaxy with Different Preflow Sources

    NASA Astrophysics Data System (ADS)

    Kawaguchi, Kenichi; Kuramata, Akito

    2005-11-01

    Two types of AlN defect structures directly grown on sapphire (0001) by metalorganic vapor-phase epitaxy with different initial growth sequences were studied. One was a domain structure with arrays of threading edge dislocations aligned along the [1-210] direction, observed in AlN with NH3 preflow. The other was threading dislocations with screw components located randomly, observed in AlN with TMA preflow. It was also confirmed that threading dislocations caused the surface depression of AlN. A model for the formation of domain structures based on the geometrical aspects and dislocation types is proposed.

  15. A New Surface Modification Method to Prevent the Release-Stiction of Micromechanical Structures during HF Vapor-Phase Etching

    NASA Astrophysics Data System (ADS)

    Yang, Woo Seok; Kang, Sung Weon; Lee, Jaewoo; Jung, Sung Hae; Kim, Yoon Tae

    2004-09-01

    A novel release process without stiction problem is a major concern in surface micromachining technology to fabricate microelectromechanical systems (MEMS) devices. HF vapor-phase etching (VPE) has been focused as a promising dry process to remove sacrificial SiO2 layer, but still has limitation due to water condensation. We have first demonstrated the effectiveness of a new surface modification method using strongly hydrophilic materials (i.e., Ti, Al2O3) in preventing the release-stiction during HF VPE process. The role of hydrophilic surface layer is proposed to suppress the water bridging causing a attractive capillary force between micromechanical and stationary structures.

  16. A GaAs metalorganic vapor phase epitaxy growth process to reduce Ge outdiffusion from the Ge substrate

    SciTech Connect

    Galiana, B.; Rey-Stolle, I.; Algora, C.

    2008-04-14

    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.

  17. Photoresponse properties of large-area MoS2 atomic layer synthesized by vapor phase deposition

    NASA Astrophysics Data System (ADS)

    Luo, Siwei; Qi, Xiang; Ren, Long; Hao, Guolin; Fan, Yinping; Liu, Yundan; Han, Weijia; Zang, Chen; Li, Jun; Zhong, Jianxin

    2014-10-01

    Photoresponse properties of a large area MoS2 atomic layer synthesized by vapor phase deposition method without any catalyst are studied. Scanning electron microscopy, atomic force microscopy, Raman spectrum, and photoluminescence spectrum characterizations confirm that the two-dimensional microstructures of MoS2 atomic layer are of high quality. Photoelectrical results indicate that the as-prepared MoS2 devices have an excellent sensitivity and a good reproducibility as a photodetector, which is proposed to be ascribed to the potential-assisted charge separation mechanism.

  18. Photoresponse properties of large-area MoS{sub 2} atomic layer synthesized by vapor phase deposition

    SciTech Connect

    Luo, Siwei; Qi, Xiang E-mail: jxzhong@xtu.edu.cn; Ren, Long; Hao, Guolin; Fan, Yinping; Liu, Yundan; Han, Weijia; Zang, Chen; Li, Jun; Zhong, Jianxin E-mail: jxzhong@xtu.edu.cn

    2014-10-28

    Photoresponse properties of a large area MoS{sub 2} atomic layer synthesized by vapor phase deposition method without any catalyst are studied. Scanning electron microscopy, atomic force microscopy, Raman spectrum, and photoluminescence spectrum characterizations confirm that the two-dimensional microstructures of MoS{sub 2} atomic layer are of high quality. Photoelectrical results indicate that the as-prepared MoS{sub 2} devices have an excellent sensitivity and a good reproducibility as a photodetector, which is proposed to be ascribed to the potential-assisted charge separation mechanism.

  19. Identification of vapor-phase chemical warfare agent simulants and rocket fuels using laser-induced breakdown spectroscopy

    SciTech Connect

    Stearns, Jaime A.; McElman, Sarah E.; Dodd, James A.

    2010-05-01

    Application of laser-induced breakdown spectroscopy (LIBS) to the identification of security threats is a growing area of research. This work presents LIBS spectra of vapor-phase chemical warfare agent simulants and typical rocket fuels. A large dataset of spectra was acquired using a variety of gas mixtures and background pressures and processed using partial least squares analysis. The five compounds studied were identified with a 99% success rate by the best method. The temporal behavior of the emission lines as a function of chamber pressure and gas mixture was also investigated, revealing some interesting trends that merit further study.

  20. Measurement of two-phase refrigerant liquid-vapor mass flow rate. Part 1: Venturi and void fraction meters

    SciTech Connect

    Abdul-Razzak, A.; Shoukri, M.; Chang, J.S.

    1995-12-31

    The use of a venturi meter for the measurement of refrigerant liquid-vapor mass flow rate in a horizontal pipe is presented. Various models that utilize the output of the venturi flowmeter and the measured void fraction and/or quality to calculate the two-phase mass flow rate were examined. It was found that the applicability of the various models is dependent on the quality range. When the quality is less than 50%, the use of the momentum density model provides the best accuracy. For higher qualities, the use of the homogeneous equilibrium model is recommended.

  1. Dislocation reduction of InAs nanofins prepared on Si substrate using metal-organic vapor-phase epitaxy

    PubMed Central

    2012-01-01

    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. PMID:23176442

  2. Threading dislocations in gallium nitride epilayers grown by metalorganic vapor phase epitaxy

    NASA Astrophysics Data System (ADS)

    Fang, Xiaolong

    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.

  3. The Layou Tuff, Dominica: an Example of an Ignimbrite Showing Extensive Vapor-Phase Crystallization

    NASA Astrophysics Data System (ADS)

    Tinnin, B.; Smith, A. L.; Fryxell, J. E.; Daly, G.

    2006-12-01

    The island of Dominica, located in the central part of the Lesser Antilles island arc, has witnessed, probably in the last 100,000 years, three large-volume Plinian eruptions. One of these from the Morne Trois Pitons center generated extensive ignimbrites (>62 km2) that extend as two tongues NE and NW from the Morne Trois Pitons caldera (now infilled by a dome complex). Preliminary studies on the NW fan, which filled the valley of the paleo-Layou River and reached the west coast near its mouth, shows that this ignimbrite sequence may be subdivided into an unlithified and a lithified facies. The former occurs in distal exposures along the edge of the ignimbrite, whereas the latter is dominant in the central valley-fill locations. The Layou ignimbrite in its most distal exposure overlies a thick sequence of fluviatile conglomerates. At this location the initial deposit is a pumiceous lapilli fall unit, 18 cm thick. Lithic clast sizes in this unit appear to be consistent with an eruption column height of 20-25 km. This deposit is followed by a thin ash-rich fall layer rich in accretionary lapilli (up to 8 mm in diameter), suggesting magma-water interaction. Overlying these fall deposits are at least 3 ignimbrite flow units. These unlithified units have a maximum thickness of over 20 m. Within the Layou valley the ignimbrites become thicker (reaching a maximum of 180 m in the upper Layou valley) and are lithified through out their exposed thickness. A 17 m section through these lithified deposits a few kilometers inland from the unlithified deposits described above suggest, based on density variations, that the maximum zone of lithification occurs 5 m above the lowest exposure of the section (i.e. approximately 15 m above the unlithified base of the deposit). Pumices in these lithified deposits do not appear to show any flattening or preferred orientation; rather the changes in density appear to be related to a decrease in the porosity of the matrix as a consequence of vapor-phase crystallization. Grain size studies on the unlithified facies suggest the Layou ignimbrite has lost more than 40% of its vitric material from the finer size fractions (< 1 mm). Whole rock array calculations suggest this vitric loss was caused by high gas flow through the deposit. These gases, which were probably dominantly heated groundwater would, according to recent experiments on the effect of water on welding, have coated the shards with sublimates. This would have inhibited sintering so that adhesion between clasts would have been principally by precipitation of sublimates in pore spaces, thus producing a sillar rather than a welded tuff. Thick lithified sequences are also associated with the other two ignimbrite sequences on Dominica and a comparison will be made between the Layou ignimbrite and these sequences as well as other non-lithified ignimbrites to better define the conditions of ignimbrite deposition and lithification in a wet tropical environment.

  4. Vapor-liquid phase equilibria of water modelled by a Kim-Gordon potential

    SciTech Connect

    Maerzke, K A; McGrath, M J; Kuo, I W; Tabacchi, G; Siepmann, J I; Mundy, C J

    2009-03-16

    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.

  5. Characterization of single-crystal diamond grown from the vapor phase on substrates of natural diamond

    SciTech Connect

    Altukhov, A. A.; Vikharev, A. L.; Gorbachev, A. M.; Dukhnovsky, M. P.; Zemlyakov, V. E.; Ziablyuk, K. N.; Mitenkin, A. V.; Muchnikov, A. B. Radishev, D. B.; Ratnikova, A. K.; Fedorov, Yu. Yu.

    2011-03-15

    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.

  6. Vapor phase tri-methyl-indium seeding system suitable for high temperature spectroscopy and thermometry.

    PubMed

    Whiddon, R; Zhou, B; Borggren, J; Aldn, M; Li, Z S

    2015-09-01

    Tri-methyl-indium (TMI) is used as an indium transport molecule to introduce indium atoms to reactive hot gas flows/combustion environments for spectroscopic diagnostics. A seeding system was constructed to allow the addition of an inert TMI laden carrier gas into an air/fuel mixture burning consequently on a burner. The amount of the seeded TMI in the carrier gas can be readily varied by controlling the vapor pressure through the temperature of the container. The seeding process was calibrated using the fluorescent emission intensity from the indium 6(2)S1/2 ? 5(2)P1/2 and 6(2)S1/2 ? 5(2)P3/2 transitions as a function of the calculated TMI seeding concentration over a range of 2-45 ppm. The response was found to be linear over the range 3-22.5 ppm; at concentrations above 25 ppm there is a loss of linearity attributable to self-absorption or loss of saturation of TMI vapor pressure in the carrier gas flow. When TMI was introduced into a post-combustion environment via an inert carrier gas, molecular transition from InH and InOH radicals were observed in the flame emission spectrum. Combined laser-induced fluorescence and absorption spectroscopy were applied to detect indium atoms in the TMI seeded flame and the measured atomic indium concentration was found to be at the ppm level. This method of seeding organometallic vapor like TMI to a reactive gas flow demonstrates the feasibility for quantitative spectroscopic investigations that may be applicable in various fields, e.g., chemical vapor deposition applications or temperature measurement in flames with two-line atomic fluorescence. PMID:26429429

  7. Vapor phase tri-methyl-indium seeding system suitable for high temperature spectroscopy and thermometry

    NASA Astrophysics Data System (ADS)

    Whiddon, R.; Zhou, B.; Borggren, J.; Aldn, M.; Li, Z. S.

    2015-09-01

    Tri-methyl-indium (TMI) is used as an indium transport molecule to introduce indium atoms to reactive hot gas flows/combustion environments for spectroscopic diagnostics. A seeding system was constructed to allow the addition of an inert TMI laden carrier gas into an air/fuel mixture burning consequently on a burner. The amount of the seeded TMI in the carrier gas can be readily varied by controlling the vapor pressure through the temperature of the container. The seeding process was calibrated using the fluorescent emission intensity from the indium 62S1/2 ? 52P1/2 and 62S1/2 ? 52P3/2 transitions as a function of the calculated TMI seeding concentration over a range of 2-45 ppm. The response was found to be linear over the range 3-22.5 ppm; at concentrations above 25 ppm there is a loss of linearity attributable to self-absorption or loss of saturation of TMI vapor pressure in the carrier gas flow. When TMI was introduced into a post-combustion environment via an inert carrier gas, molecular transition from InH and InOH radicals were observed in the flame emission spectrum. Combined laser-induced fluorescence and absorption spectroscopy were applied to detect indium atoms in the TMI seeded flame and the measured atomic indium concentration was found to be at the ppm level. This method of seeding organometallic vapor like TMI to a reactive gas flow demonstrates the feasibility for quantitative spectroscopic investigations that may be applicable in various fields, e.g., chemical vapor deposition applications or temperature measurement in flames with two-line atomic fluorescence.

  8. Vapor-phase transport in the near-drift environment at Yucca Mountain

    NASA Astrophysics Data System (ADS)

    Salve, Rohit; Kneafsey, Timothy J.

    2005-01-01

    A key issue regarding the performance of the potential high-level radioactive waste repository at Yucca Mountain, Nevada, is the likelihood of precipitation percolating a vertical distance of ˜300 m through fractured unsaturated rock into drifts containing waste packages. Water enhances waste package corrosion and is required for transport of released radionuclides. To evaluate the propensity for seepage into tunnels at Yucca Mountain, a 5-m-diameter, 2.7-km-long tunnel, commonly referred to as the Cross Drift (CD), was excavated in 1998, branching off from the main Exploratory Studies Facility tunnel. Sections of this tunnel have been isolated from ventilation for extended periods over the last 4 years. We present continuous measurements of relative humidity and temperature and periodic observations of liquid water in the CD over two periods. During this observation duration the terminal section of the drift was partitioned into four sections by bulkheads, and ventilation to these sections was minimized to a few days. We compare these observations to results from analytical and numerical models to investigate processes associated with the movement of water vapor between the tunnel bore and the surrounding fractured rock formation. Observations from this effort indicate that fractures can be primary paths for unsaturated zone vapor flow in the immediate vicinity of emplacement drifts. Observations, measurements, and analysis indicate the need for a model that includes fracture-dominated vapor transport as a significant contributor to total water flow into the drifts.

  9. Vapor-phase transport in the near-drift environment at Yucca Mountain

    NASA Astrophysics Data System (ADS)

    Salve, Rohit; Kneafsey, Timothy J.

    2005-01-01

    A key issue regarding the performance of the potential high-level radioactive waste repository at Yucca Mountain, Nevada, is the likelihood of precipitation percolating a vertical distance of ~300 m through fractured unsaturated rock into drifts containing waste packages. Water enhances waste package corrosion and is required for transport of released radionuclides. To evaluate the propensity for seepage into tunnels at Yucca Mountain, a 5-m-diameter, 2.7-km-long tunnel, commonly referred to as the Cross Drift (CD), was excavated in 1998, branching off from the main Exploratory Studies Facility tunnel. Sections of this tunnel have been isolated from ventilation for extended periods over the last 4 years. We present continuous measurements of relative humidity and temperature and periodic observations of liquid water in the CD over two periods. During this observation duration the terminal section of the drift was partitioned into four sections by bulkheads, and ventilation to these sections was minimized to a few days. We compare these observations to results from analytical and numerical models to investigate processes associated with the movement of water vapor between the tunnel bore and the surrounding fractured rock formation. Observations from this effort indicate that fractures can be primary paths for unsaturated zone vapor flow in the immediate vicinity of emplacement drifts. Observations, measurements, and analysis indicate the need for a model that includes fracture-dominated vapor transport as a significant contributor to total water flow into the drifts.

  10. TNX Area Phase II Soil Vapor Extraction Test Treatability Study Report

    SciTech Connect

    Noonkester, Jay

    2000-11-01

    The Savannah River Technology Center (SRTC), at the Savannah River Site (SRS), operates a pilot scale testing facility in the TNX Area. Research conducted in the TNX Area generated wastewater that was disposed of in earthen basins until 1988. As a result of these operations, shallow groundwater and sediments beneath the TNX Area are contaminated with both dissolved and residual chlorinated volatile organic compounds (CVOCs) such as trichloroethylene (TCE), carbon tetrachloride, and perchloroethylene (PCE). In 1996, the SRS initiated an Interim Remedial Action to capture and contain the dissolved contamination that was greater that 500 {micro}g/L TCE (WSRC, 1999). The Interim Remedial Action included the installation of a recovery well network and air stripper, and a vertical recirculation well. The objective of the recovery well network and air stripper is to provide hydraulic containment of the contaminated groundwater and provide a mechanism for the treatment of purge water generated during monitoring of the Interim Remedial Action. A vertical recirculation well, TVR1A, was installed to test the in-well vapor stripping (IVS) technology. Results from the test indicated that the IVS technology was not effective in the TNX Area. A single well soil vapor extraction test was conducted during June of 1997 using well TVR1A and the existing vacuum extraction unit that was installed for the in-well vapor stripping test. The objective of the SVE test at TNX was to collect preliminary information for the design of a SVE system to remediate residual CVOCs in the sediments.

  11. Toward a Monte Carlo program for simulating vapor-liquid phase equilibria from first principles

    SciTech Connect

    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

    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.

  12. Suppression of metastable-phase inclusion in N-polar (0001{sup ¯}) InGaN/GaN multiple quantum wells grown by metalorganic vapor phase epitaxy

    SciTech Connect

    Shojiki, Kanako Iwabuchi, Takuya; Kuboya, Shigeyuki; Choi, Jung-Hun; Tanikawa, Tomoyuki; Hanada, Takashi; Katayama, Ryuji; Matsuoka, Takashi; Usami, Noritaka

    2015-06-01

    The metastable zincblende (ZB) phase in N-polar (0001{sup ¯}) (−c-plane) InGaN/GaN multiple quantum wells (MQWs) grown by metalorganic vapor phase epitaxy is elucidated by the electron backscatter diffraction measurements. From the comparison between the −c-plane and Ga-polar (0001) (+c-plane), the −c-plane MQWs were found to be suffered from the severe ZB-phase inclusion, while ZB-inclusion is negligible in the +c-plane MQWs grown under the same growth conditions. The ZB-phase inclusion is a hurdle for fabricating the −c-plane light-emitting diodes because the islands with a triangular shape appeared on a surface in the ZB-phase domains. To improve the purity of stable wurtzite (WZ)-phase, the optimum conditions were investigated. The ZB-phase is dramatically eliminated with decreasing the V/III ratio and increasing the growth temperature. To obtain much-higher-quality MQWs, the thinner InGaN wells and the hydrogen introduction during GaN barriers growth were tried. Consequently, MQWs with almost pure WZ phase and with atomically smooth surface have been demonstrated.

  13. Suppression of metastable-phase inclusion in N-polar (000 1 ¯) InGaN/GaN multiple quantum wells grown by metalorganic vapor phase epitaxy

    NASA Astrophysics Data System (ADS)

    Shojiki, Kanako; Choi, Jung-Hun; Iwabuchi, Takuya; Usami, Noritaka; Tanikawa, Tomoyuki; Kuboya, Shigeyuki; Hanada, Takashi; Katayama, Ryuji; Matsuoka, Takashi

    2015-06-01

    The metastable zincblende (ZB) phase in N-polar (000 1 ¯) (-c-plane) InGaN/GaN multiple quantum wells (MQWs) grown by metalorganic vapor phase epitaxy is elucidated by the electron backscatter diffraction measurements. From the comparison between the -c-plane and Ga-polar (0001 ) (+c-plane), the -c-plane MQWs were found to be suffered from the severe ZB-phase inclusion, while ZB-inclusion is negligible in the +c-plane MQWs grown under the same growth conditions. The ZB-phase inclusion is a hurdle for fabricating the -c-plane light-emitting diodes because the islands with a triangular shape appeared on a surface in the ZB-phase domains. To improve the purity of stable wurtzite (WZ)-phase, the optimum conditions were investigated. The ZB-phase is dramatically eliminated with decreasing the V/III ratio and increasing the growth temperature. To obtain much-higher-quality MQWs, the thinner InGaN wells and the hydrogen introduction during GaN barriers growth were tried. Consequently, MQWs with almost pure WZ phase and with atomically smooth surface have been demonstrated.

  14. A vapor phase hydrothermal modification method converting a honeycomb structured hybrid film into photoactive TiO2 film.

    PubMed

    Zhao, Huijun; Shen, Yanming; Zhang, Shanqing; Zhang, Haimin

    2009-09-15

    Transforming an organic/inorganic hybrid material into a pure inorganic material without losing its original structure is of interest for a range of applications. In this work, a simple and effective vapor phase hydrothermal method was developed to transform a 3D honeycomb structured PS/TTIP hybrid film into a photoactive TiO2 film without dismantling the originally templated 3D structure. The method utilizes the vapor phase hydrothermal process to create titania network/clusters with sufficient mechanical strength via the formation of Ti-oxo bridges. The organic components of the sample can be removed by means of pyrolysis while perfectly maintaining the original 3D honeycomb structure. The resultant film can be directly used for photocatalysis applications and could be further modified for other applications. In principle, this method can be used to preserve 3D structures of other organic/inorganic hybrid films during their conversion to pure inorganic films via a pyrolysis process, if mechanically strong networks can be formed as a result of hydrolysis reactions. The ability to preserve the preferred 3D structure during the subsequent conversion processes enables realization of the full benefit of unique architectures created by a templating method. PMID:19496571

  15. Environmentally friendly method to grow wide-bandgap semiconductor aluminum nitride crystals: Elementary source vapor phase epitaxy

    NASA Astrophysics Data System (ADS)

    Wu, Peitsen; Funato, Mitsuru; Kawakami, Yoichi

    2015-11-01

    Aluminum nitride (AlN) has attracted increasing interest as an optoelectronic material in the deep ultraviolet spectral range due to its wide bandgap of 6.0?eV (207?nm wavelength) at room temperature. Because AlN bulk single crystals are ideal device substrates for such applications, the crystal growth of bulky AlN has been extensively studied. Two growth methods seem especially promising: hydride vapor phase epitaxy (HVPE) and sublimation. However, the former requires hazardous gases such as hydrochloric acid and ammonia, while the latter needs extremely high growth temperatures around 2000?C. Herein we propose a novel vapor-phase-epitaxy-based growth method for AlN that does not use toxic materials; the source precursors are elementary aluminum and nitrogen gas. To prepare our AlN, we constructed a new growth apparatus, which realizes growth of AlN single crystals at a rate of ~18 ?m/h at 1550?C using argon as the source transfer via the simple reaction Al?+?1/2N2 ? AlN. This growth rate is comparable to that by HVPE, and the growth temperature is much lower than that in sublimation. Thus, this study opens up a novel route to achieve environmentally friendly growth of AlN.

  16. Environmentally friendly method to grow wide-bandgap semiconductor aluminum nitride crystals: Elementary source vapor phase epitaxy.

    PubMed

    Wu, PeiTsen; Funato, Mitsuru; Kawakami, Yoichi

    2015-01-01

    Aluminum nitride (AlN) has attracted increasing interest as an optoelectronic material in the deep ultraviolet spectral range due to its wide bandgap of 6.0?eV (207?nm wavelength) at room temperature. Because AlN bulk single crystals are ideal device substrates for such applications, the crystal growth of bulky AlN has been extensively studied. Two growth methods seem especially promising: hydride vapor phase epitaxy (HVPE) and sublimation. However, the former requires hazardous gases such as hydrochloric acid and ammonia, while the latter needs extremely high growth temperatures around 2000?C. Herein we propose a novel vapor-phase-epitaxy-based growth method for AlN that does not use toxic materials; the source precursors are elementary aluminum and nitrogen gas. To prepare our AlN, we constructed a new growth apparatus, which realizes growth of AlN single crystals at a rate of ~18 ?m/h at 1550?C using argon as the source transfer via the simple reaction Al?+?1/2N2 ? AlN. This growth rate is comparable to that by HVPE, and the growth temperature is much lower than that in sublimation. Thus, this study opens up a novel route to achieve environmentally friendly growth of AlN. PMID:26616203

  17. Environmentally friendly method to grow wide-bandgap semiconductor aluminum nitride crystals: Elementary source vapor phase epitaxy

    PubMed Central

    Wu, PeiTsen; Funato, Mitsuru; Kawakami, Yoichi

    2015-01-01

    Aluminum nitride (AlN) has attracted increasing interest as an optoelectronic material in the deep ultraviolet spectral range due to its wide bandgap of 6.0 eV (207 nm wavelength) at room temperature. Because AlN bulk single crystals are ideal device substrates for such applications, the crystal growth of bulky AlN has been extensively studied. Two growth methods seem especially promising: hydride vapor phase epitaxy (HVPE) and sublimation. However, the former requires hazardous gases such as hydrochloric acid and ammonia, while the latter needs extremely high growth temperatures around 2000 °C. Herein we propose a novel vapor-phase-epitaxy-based growth method for AlN that does not use toxic materials; the source precursors are elementary aluminum and nitrogen gas. To prepare our AlN, we constructed a new growth apparatus, which realizes growth of AlN single crystals at a rate of ~18 μm/h at 1550 °C using argon as the source transfer via the simple reaction Al + 1/2N2 → AlN. This growth rate is comparable to that by HVPE, and the growth temperature is much lower than that in sublimation. Thus, this study opens up a novel route to achieve environmentally friendly growth of AlN. PMID:26616203

  18. Structural and morphological characteristics of planar (1120) a-plane gallium nitride grown by hydride vapor phase epitaxy

    NASA Astrophysics Data System (ADS)

    Haskell, B. A.; Wu, F.; Matsuda, S.; Craven, M. D.; Fini, P. T.; DenBaars, S. P.; Speck, J. S.; Nakamura, Shuji

    2003-08-01

    This letter discusses the structural and morphological characteristics of planar, nonpolar (1120) a-plane GaN films grown on (1102) r-plane sapphire by hydride vapor phase epitaxy. Specular films with thicknesses over 50 ?m were grown, eliminating the severely faceted surfaces that have previously been observed for hydride vapor phase epitaxy-grown a-plane films. Internal cracks and crack healing, similar to that in c-plane GaN films, were observed. Atomic force microscopy revealed nanometer-scale pitting and steps on the film surfaces, with rms roughness of 2 nm. X-ray diffraction confirmed the films are solely a-plane oriented with on-axis (1120) and 30 off-axis (1010) rocking curve peak widths of 1040 and 3000 arcsec, respectively. Transmission electron microscopy revealed a typical basal plane stacking fault density of 4105cm-1. The dislocation content of the films consisted of predominately edge component (bedge=[0001]) threading dislocations with a density of 21010 cm-2, and mixed-character Shockley partial dislocations (b=1/3<1100>) with a density of 7109 cm-2.

  19. Vapor-phase and particulate-associated pesticides and PCB concentrations in eastern North Dakota air samples

    SciTech Connect

    Hawthorne, S.B.; Miller, D.J.; Louie, P.K.K.

    1996-05-01

    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.

  20. Vapor-phase hydrothermal transformation of HTiOF3 intermediates into {001} faceted anatase single-crystalline nanosheets.

    PubMed

    Liu, Porun; Wang, Yun; Zhang, Haimin; An, Taicheng; Yang, Huagui; Tang, Zhiyong; Cai, Weiping; Zhao, Huijun

    2012-12-01

    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

  1. Significance of vapor phase chemical reactions on CVD rates predicted by chemically frozen and local thermochemical equilibrium boundary layer theories

    NASA Technical Reports Server (NTRS)

    Gokoglu, Suleyman A.

    1988-01-01

    This paper investigates the role played by vapor-phase chemical reactions on CVD rates by comparing the results of two extreme theories developed to predict CVD mass transport rates in the absence of interfacial kinetic barrier: one based on chemically frozen boundary layer and the other based on local thermochemical equilibrium. Both theories consider laminar convective-diffusion boundary layers at high Reynolds numbers and include thermal (Soret) diffusion and variable property effects. As an example, Na2SO4 deposition was studied. It was found that gas phase reactions have no important role on Na2SO4 deposition rates and on the predictions of the theories. The implications of the predictions of the two theories to other CVD systems are discussed.

  2. Double-Polarity Selective Area Growth of GaN Metal Organic Vapor Phase Epitaxy by Using Carbon Mask Layers

    NASA Astrophysics Data System (ADS)

    Fujita, Yohei; Takano, Yasushi; Inoue, Yoku; Sumiya, Masatomo; Fuke, Shunro; Nakano, Takayuki

    2013-08-01

    For nonlinear optical applications using gallium nitride (GaN), periodic inversion of crystallographic orientation (polarity) is required for quasi-phase matching. We developed a novel procedure for designing polarity patterns in GaN using metal organic vapor phase epitaxy (MOVPE), and we used this to fabricate periodic polarity-inverted GaN films. By using a carbon mask for the formation of the selective area, substrate nitriding and mask removal of the selective area were carried out in the GaN epitaxial growth process. In this report, double-polarity selective area growth (DP-SAG) was realized by optimizing the nitriding and mask removal conditions. The interface of the Ga-polarity/N-polarity region became sharp by controlling the V/III ratio at 4700.

  3. Surface acoustic waves in semi-insulating Fe-doped GaN films grown by hydride vapor phase epitaxy

    NASA Astrophysics Data System (ADS)

    Fan, Yingmin; Liu, Zhenghui; Xu, Gengzhao; Zhong, Haijian; Huang, Zengli; Zhang, Yumin; Wang, Jianfeng; Xu, Ke

    2014-08-01

    The propagation properties of surface acoustic waves (SAWs) in semi-insulating Fe-doped GaN films grown on sapphire substrates by hydride vapor phase epitaxy are investigated. Compared with native n-type GaN, Fe-doped GaN exhibits a higher electromechanical coupling coefficient due to its high electrical resistivity. In addition, guided longitudinal leaky surface acoustic wave (LLSAW) was observed experimentally with a very high phase velocity (about 7890 m/s), and this mode was verified by numerical simulations. The small propagation attenuation of LLSAW along liquid/solid interfaces was demonstrated in glycerol solutions, which implies the potential applications in high-frequency chemical sensing.

  4. Detection of nitroaromatics in the solid, solution, and vapor phases using silicon quantum dot sensors.

    PubMed

    Nguyen, An; Gonzalez, Christina M; Sinelnikov, Regina; Newman, W; Sun, Sarah; Lockwood, Ross; Veinot, Jonathan G C; Meldrum, Al

    2016-03-11

    Silicon quantum dots (Si-QDs) represent a well-known QD fluorophore that can emit throughout the visible spectrum depending on the interface structure and surface functional group. Detection of nitroaromatic compounds by monitoring the luminescence response of the sensor material (typically fluorescent polymers) currently forms the basis of new explosives sensing technologies. Freestanding silicon QDs may represent a benign alternative with a high degree of chemical and physical versatility. Here, we investigate dodecyl and amine-terminated Si-QD luminescence response to the presence of nitrobenzene and dinitrotoluene (DNT) in various solid, solution, and vapor forms. For dinitrotoluene vapor the 3σ detection limit was 6 ppb for monomer-terminated QDs. For nitroaromatics dissolved in toluene the detection limit was on the order of 400 nM, corresponding to ∼100 pg of material distributed over ∼1 cm(2) on the sensor surface. Solid traces of nitroaromatics were also easily detectable via a simple 'touch test'. The samples showed minimal interference effects from common contaminants such as water, ethanol, and acetonitrile. The sensor can be as simple and inexpensive as a small circle of filter paper dipped into a QD solution, with a single vial of QDs able to make hundreds of these sensors. Additionally, a trial fiber-optic sensor device was tested by applying the QDs to one end of a 2 × 2 fiber coupler and exposing them to controlled DNT vapor. Finally, the quenching mechanism was explored via luminescence dynamics measurements and is different for blue (amine) and red (dodecyl) fluorescent silicon QDs. PMID:26863492

  5. Detection of nitroaromatics in the solid, solution, and vapor phases using silicon quantum dot sensors

    NASA Astrophysics Data System (ADS)

    Nguyen, An; Gonzalez, Christina M.; Sinelnikov, Regina; Newman, W.; Sun, Sarah; Lockwood, Ross; Veinot, Jonathan G. C.; Meldrum, Al

    2016-03-01

    Silicon quantum dots (Si-QDs) represent a well-known QD fluorophore that can emit throughout the visible spectrum depending on the interface structure and surface functional group. Detection of nitroaromatic compounds by monitoring the luminescence response of the sensor material (typically fluorescent polymers) currently forms the basis of new explosives sensing technologies. Freestanding silicon QDs may represent a benign alternative with a high degree of chemical and physical versatility. Here, we investigate dodecyl and amine-terminated Si-QD luminescence response to the presence of nitrobenzene and dinitrotoluene (DNT) in various solid, solution, and vapor forms. For dinitrotoluene vapor the 3σ detection limit was 6 ppb for monomer-terminated QDs. For nitroaromatics dissolved in toluene the detection limit was on the order of 400 nM, corresponding to ∼100 pg of material distributed over ∼1 cm2 on the sensor surface. Solid traces of nitroaromatics were also easily detectable via a simple ‘touch test’. The samples showed minimal interference effects from common contaminants such as water, ethanol, and acetonitrile. The sensor can be as simple and inexpensive as a small circle of filter paper dipped into a QD solution, with a single vial of QDs able to make hundreds of these sensors. Additionally, a trial fiber-optic sensor device was tested by applying the QDs to one end of a 2 × 2 fiber coupler and exposing them to controlled DNT vapor. Finally, the quenching mechanism was explored via luminescence dynamics measurements and is different for blue (amine) and red (dodecyl) fluorescent silicon QDs.

  6. Real-Time Optical Monitoring and Simulations of Gas Phase Kinetics in InN Vapor Phase Epitaxy at High Pressure

    NASA Technical Reports Server (NTRS)

    Dietz, Nikolaus; Woods, Vincent; McCall, Sonya D.; Bachmann, Klaus J.

    2003-01-01

    Understanding the kinetics of nucleation and coalescence of heteroepitaxial thin films is a crucial step in controlling a chemical vapor deposition process, since it defines the perfection of the heteroepitaxial film both in terms of extended defect formation and chemical integrity of the interface. The initial nucleation process also defines the film quality during the later stages of film growth. The growth of emerging new materials heterostructures such as InN or In-rich Ga(x)In(1-x)N require deposition methods operating at higher vapor densities due to the high thermal decomposition pressure in these materials. High nitrogen pressure has been demonstrated to suppress thermal decomposition of InN, but has not been applied yet in chemical vapor deposition or etching experiments. Because of the difficulty with maintaining stochiometry at elevated temperature, current knowledge regarding thermodynamic data for InN, e.g., its melting point, temperature-dependent heat capacity, heat and entropy of formation are known with far less accuracy than for InP, InAs and InSb. Also, no information exists regarding the partial pressures of nitrogen and phosphorus along the liquidus surfaces of mixed-anion alloys of InN, of which the InN(x)P(1-x) system is the most interesting option. A miscibility gap is expected for InN(x)P(1-x) pseudobinary solidus compositions, but its extent is not established at this point by experimental studies under near equilibrium conditions. The extension of chemical vapor deposition to elevated pressure is also necessary for retaining stoichiometric single phase surface composition for materials that are characterized by large thermal decomposition pressures at optimum processing temperatures.

  7. Vapor-Phase-Deposited Organosilane Coatings as "Hardening" Agents for High-Peak-Power Laser Optics

    SciTech Connect

    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

    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.

  8. Laboratory studies of silicon vapor deposition, phase A. [feasibility of producing thin films for photovoltaic applications

    NASA Technical Reports Server (NTRS)

    Frost, R. T.; Racette, G. W.; Stockhoff, E. H.

    1977-01-01

    A system is described capable of carrying out silicon vapor deposition experiments in the low 10 to the minus 10th power torr vacuum range. The system was assembled and tested for use in a program aimed at exploration of vacuum heteroepitaxy of silicon on several substrates of potential interest for photovoltaic applications. An experiment is described in which a silicon layer 2.5 microns thick was deposited on a pyrolytically cleaned tungsten substrate held at a temperature of 400 C. Using a resistance heated silicon source, thicker layers can be deposited in periods of hours by utilizing closer source to substrate distances.

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

    NASA Technical Reports Server (NTRS)

    Plahutnik, F.; Arvidson, A.; Sawyer, D.

    1982-01-01

    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).

  10. First Principles Monte Carlo Simulations of Aggregation in the Vapor Phase of Hydrogen Fluoride

    SciTech Connect

    McGrath, M. J.; Ghogomu, Julius N.; Mundy, Christopher J.; Kuo, I-F W.; Siepmann, J. I.

    2010-07-01

    The aggregation of superheated hydrogen ?uoride vapor is explored through the use of Monte Carlo simulations employing Kohn-Sham density functional theory with the exchange/correlation functional of Becke-Lee-Yang-Parr to describe the molecular interactions. Simulations were carried out in the canonical ensemble for a system consisting of ten molecules at constant density (2700 ?A3 /molecule) and at three di?erent temperatures (T = 310, 350, and 390 K). Aggregation-volume-bias and con?gurational-bias Monte Carlo approaches (along with pre-sampling with an approximate potential) were employed to increase the sampling e?ciency of cluster formation and destruction.

  11. Children, Cigarettes and E-cigarettes

    MedlinePLUS Videos and Cool Tools

    ... can help keep your family healthy. Related MedlinePlus Health Topics E-Cigarettes Smoking and Youth About MedlinePlus ... Rockville Pike, Bethesda, MD 20894 U.S. Department of Health and Human Services National Institutes of Health Page ...

  12. Vapor Phase Infrared Spectroscopy and Ab Initio Fundamental Anharmonic Frequencies of Ammonia Borane

    SciTech Connect

    Sams, R. L.; Xantheas, Sotiris S.; Blake, Thomas A.

    2012-03-29

    Infrared absorption spectra of ammonia borane vapor have been recorded between 3600 and 600 cm-1. Of the eleven infrared active modes, seven of the vibrational modes of NH3 11BH3 have been observed and four of the vibrational modes of NH3 10BH3 were observed. The spectra were recorded with sufficient resolution to observe the rotational structure of the bands, which allowed for preliminary least squares fitting of the band origins and rotational constants. First principals electronic structure calculations were performed to obtain anharmonic band origins and their intensities. The band assignments are discussed in relation to other spectroscopic techniques that have been used to study this molecule. A semi empirical estimate of the vapor pressure of ammonia borane at room temperature (22 °C) was made and found to be ~ 1 × 10-4 Torr. The assignment of the measured modes was aided by the calculated anharmonic frequencies and their infrared intensities. The combination of the CCSD(T) harmonic frequencies with the B3LYP anharmonicities, obtained from second order vibrational perturbation theory, was found to produce an overall best agreement with the measured band origins.

  13. Vapor-liquid phase equilibria of water modelled by a Kim-Gordon potential

    SciTech Connect

    Maerzke, Katie A.; McGrath, M. J.; Kuo, I-F W.; Tabacchi, Gloria; Siepmann, Joern I.; Mundy, Christopher J.

    2009-09-07

    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 overestimated, respectively. We present a comprehensive density functional theory study to asses the accuracy of two popular exchange correlation functionals on the structure and density of liquid water at ambient conditions This work was supported by the US Department of Energy Office of Basic Energy Science Chemical Sciences Program. Battelle operates Pacific Northwest National Laboratory for the US Department of Energy.

  14. Investigation by microarray analysis of effects of cigarette design characteristics on gene expression in human lung mucoepidermoid cancer cells NCI-H292 exposed to cigarette smoke.

    PubMed

    Sekine, Takashi; Sakaguchi, Chikako; Fukano, Yasuo

    2015-02-01

    The effects of tobacco leaf types and the presence or absence of charcoal in the cigarette filters on gene expression were investigated using cigarette prototypes made of either flue-cured (FC) leaf or burley (BLY) leaf and Kentucky Reference 2R4F as a representative blend cigarette with cellulose acetate filters or charcoal filters. NCI-H292, human lung mucoepidermoid carcinoma cell line, was exposed to the total particulate matter (TPM) and gas/vapor phase (GVP) from each prototype for 8h and then the changes in gene expression from microarray data were analyzed. A number of genes associated with oxidative stress, inflammation, DNA damage and xenobiotic response were modified by the two fractions, TPM and GVP, from the three prototypes with cellulose acetate filters. Both TPM and GVP fractions strongly enhanced the gene expression of HMOX1, which is encoding the limiting enzyme in heme degradation and a key regulator of oxidative stress and inflammatory process. Comparing the effects of TPM and GVP fraction, TPM strongly activated Nrf2 pathway-mediated anti-oxidative stress reaction, whereas GVP caused notable DNA damage response. In comparison of FC and BLY, TPM from FC more strongly induced the expression of histone family proteins than that from BLY. GVP from FC markedly induced gene expression associated with HSP70-mediated inflammation relative to that from BLY. Charcoal included in the filter strongly reduced the effects of GVP from each cigarette on gene expression. However, charcoal did not modified the effects of TPM. As a whole, charcoal is a useful material for reducing the biological effects of GVP. PMID:25497788

  15. A flux induced crystal phase transition in the vapor-liquid-solid growth of indium-tin oxide nanowires

    NASA Astrophysics Data System (ADS)

    Meng, Gang; Yanagida, Takeshi; Yoshida, Hideto; Nagashima, Kazuki; Kanai, Masaki; Zhuge, Fuwei; He, Yong; Klamchuen, Annop; Rahong, Sakon; Fang, Xiaodong; Takeda, Seiji; Kawai, Tomoji

    2014-05-01

    Single crystalline metal oxide nanowires formed via a vapor-liquid-solid (VLS) route provide a platform not only for studying fundamental nanoscale properties but also for exploring novel device applications. Although the crystal phase variation of metal oxides, which exhibits a variety of physical properties, is an interesting feature compared with conventional semiconductors, it has been difficult to control the crystal phase of metal oxides during the VLS nanowire growth. Here we show that a material flux critically determines the crystal phase of indium-tin oxide nanowires grown via the VLS route, although thermodynamical parameters, such as temperature and pressure, were previously believed to determine the crystal phase. The crystal phases of indium-tin oxide nanowires varied from the rutile structures (SnO2), the metastable fluorite structures (InxSnyO3.5) and the bixbyite structures (Sn-doped In2O3) when only the material flux was varied within an order of magnitude. This trend can be interpreted in terms of the material flux dependence of crystal phases (rutile SnO2 and bixbyite In2O3) on the critical nucleation at the liquid-solid (LS) interface. Thus, precisely controlling the material flux, which has been underestimated for VLS nanowire growths, allows us to design the crystal phase and properties in the VLS nanowire growth of multicomponent metal oxides.Single crystalline metal oxide nanowires formed via a vapor-liquid-solid (VLS) route provide a platform not only for studying fundamental nanoscale properties but also for exploring novel device applications. Although the crystal phase variation of metal oxides, which exhibits a variety of physical properties, is an interesting feature compared with conventional semiconductors, it has been difficult to control the crystal phase of metal oxides during the VLS nanowire growth. Here we show that a material flux critically determines the crystal phase of indium-tin oxide nanowires grown via the VLS route, although thermodynamical parameters, such as temperature and pressure, were previously believed to determine the crystal phase. The crystal phases of indium-tin oxide nanowires varied from the rutile structures (SnO2), the metastable fluorite structures (InxSnyO3.5) and the bixbyite structures (Sn-doped In2O3) when only the material flux was varied within an order of magnitude. This trend can be interpreted in terms of the material flux dependence of crystal phases (rutile SnO2 and bixbyite In2O3) on the critical nucleation at the liquid-solid (LS) interface. Thus, precisely controlling the material flux, which has been underestimated for VLS nanowire growths, allows us to design the crystal phase and properties in the VLS nanowire growth of multicomponent metal oxides. Electronic supplementary information (ESI) available: STEM mapping of In and Sn in an ISO nanowire (Fig. S1) and homogeneity of a fluorite ISO phase at the full length of a nanowire (Fig. S2). See DOI: 10.1039/c4nr01016g

  16. Condensed phase conversion and growth of nanorods instead of from vapor

    DOEpatents

    Geohegan, David B.; Seals, Roland D.; Puretzky, Alex A.; Fan, Xudong

    2005-08-02

    Compositions, systems and methods are described for condensed phase conversion and growth of nanorods and other materials. A method includes providing a condensed phase matrix material; and activating the condensed phase matrix material to produce a plurality of nanorods by condensed phase conversion and growth from the condensed chase matrix material instead of from vacor. The compositions are very strong. The compositions and methods provide advantages because they allow (1) formation rates of nanostructures necessary for reasonable production rates, and (2) the near net shaped production of component structures.

  17. Application of the Vapor-phase Multi-stage CMD Test to Characterize Contaminant Mass Discharge Associated with Volatile Organic Contaminant Sources in the Vadose Zone

    NASA Astrophysics Data System (ADS)

    Brusseau, M. L.; Mainhagu, J.; Morrison, C. N.; Carroll, K. C.

    2014-12-01

    Vapor-phase multi-stage contaminant mass discharge (CMD) tests were conducted at two field sites to measure mass discharge associated with contaminant sources located in the vadose zone. A CMD of 32 g/d was obtained for a site at which soil vapor extraction (SVE) has been in operation for approximately 6 years. The behavior exhibited for the vapor extractions conducted at this site suggests that there is unlikely to be a significant mass of non-vapor-phase contaminant (e.g., DNAPL, sorbed phase) present in the advective domains, and that most remaining mass is likely located in poorly accessible domains. Given the conditions for this site, this remaining mass is hypothesized to be associated with the low-permeability (and higher water saturation) region in the vicinity of the saturated zone and capillary fringe. This is supported by the results of a sediment-coring effort conducted prior to the CMD test. A CMD of 270 g/d was obtained for a site for which there were no prior SVE operations. The behavior exhibited for the vapor extractions conducted at this site suggest that non-vapor-phase contaminant mass (e.g., DNAPL) may be present in the advective domains. This is consistent with the results of prior characterization activities conducted at the site. Hence, the asymptotic conditions observed for this site most likely derive from a combination of rate-limited mass transfer from DNAPL (and sorbed) phases present in the advective domain as well as mass residing in lower-permeability ("non-advective") regions. The CMD values obtained from the tests were used in conjunction with a recently developed vapor-discharge tool to evaluate the impact of the measured CMDs on groundwater quality.

  18. 27 CFR 40.351 - Cigarette papers.

    Code of Federal Regulations, 2014 CFR

    2014-04-01

    ... OF THE TREASURY (CONTINUED) TOBACCO MANUFACTURE OF TOBACCO PRODUCTS, CIGARETTE PAPERS AND TUBES, AND PROCESSED TOBACCO Manufacture of Cigarette Papers and Tubes Taxes 40.351 Cigarette papers....

  19. Toxicological assessment of kretek cigarettes Part 4: mechanistic investigations, smoke chemistry and in vitro toxicity.

    PubMed

    Roemer, E; Dempsey, R; Lawless-Pyne, J; Lukman, S; Evans, A Deger; Trelles-Sticken, E; Wittke, S; Schorp, M K

    2014-12-01

    The smoke chemistry and in vitro toxicity of mainstream smoke (MS) was investigated in American-blended cigarettes with or without the addition of 2.5%, 5% or 10% eugenol to the tobacco and in Indonesian-blended cigarettes with and without the addition of cloves, cloves extracted with hot ethanol, and extracted cloves replenished with eugenol or clove oil. The addition of eugenol reduced the concentration of nearly all toxicants measured in MS as well as the in vitro cytotoxicity of the gas/vapor phase. Reductions were also seen in bacterial mutagenicity of the total particulate matter (TPM) assessed by the Ames Assay. The addition of extracted cloves led to increases and decreases of toxicant concentrations in MS. Replenishment with eugenol or clove oil decreased the toxicant concentrations; with most smoke constituent concentrations reduced below the concentration found in tobacco-only cigarettes. Cytotoxicity of the TPM was not affected by the clove preparations. However, GVP cytotoxicity was reduced (untreated cloves showing the highest reductions). Mutagenicity of TPM was decreased by the clove preparations. Mechanisms for the reductions, (up to 40%), are most likely due to dilution effects by eugenol, changed burning characteristics of the tobacco, and free radical scavenging by eugenol. PMID:25455230

  20. Metalorganic vapor phase epitaxy of ternary rhombohedral (Bi1-xSbx) 2 Se3 solid solutions

    NASA Astrophysics Data System (ADS)

    Kuznetsov, P. I.; Yakushcheva, G. G.; Shchamkhalova, B. S.; Luzanov, V. A.; Temiryazev, A. G.; Jitov, V. A.

    2016-01-01

    We studied the metalorganic vapor phase epitaxy (MOVPE) of (Bi1-xSbx) 2Se3 solid solution films with a different Sb content on (001) Al2O3 substrates with thin ZnSe buffer layer in the range of temperatures 250-480 C. As-grown films were studied by atom force and scanning electron microscopy (AFM and SEM), Raman spectroscopy and X-ray diffractometry (XRD) techniques. To determine the elemental composition of the grown films, we used an energy dispersive spectrometer (EDS). The dependencies of the crystal structure of films on the growth temperature and Sb content (0 ? x ? 1) were explored. At different growth temperatures we obtained the following bismuth compounds: the films grown at the temperature of 370 C or lower consist of the pure Bi phase, whereas we got the Bi4Se3 phase at 380 C, the phase BiSe at 430 C and Bi2Se3 at the temperature of 460 C or above. We found out that at the temperature of 480 C the single-phase films of (Bi1-xSbx) 2Se3 with rhombohedral and orthorhombic lattices are realized when x is less than 0.25 and greater than 0.935, respectively. For 0.25 < x < 0.935 the grown films are composites of rhombohedral and orthorhombic phases. At the temperature of 440 C we obtained films consisting of three rhombohedral phases (Bi1-xSbx) 4Se3, (Bi1-xSbx) Se and Bi. The room temperature transport properties of rhombohedral samples were characterized using the Van der Pauw technique.

  1. Development of a polysilicon process based on chemical vapor deposition (phase 1)

    NASA Astrophysics Data System (ADS)

    McCormick, J.; Arvidson, A.; Sawyer, D.; Plahutnik, F.

    1981-06-01

    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.

  2. Tailoring the Composition of Bio-oil by Vapor-Phase Removal of Organic Acids.

    PubMed

    Zhang, Jing; Choi, Yong S; Shanks, Brent H

    2015-12-01

    Selective removal of organic acids from biomass pyrolysis vapors was demonstrated. A broad adsorbent range was tested with CaCO3 showing the best selectivity. Extensive material characterization demonstrated that the acid removal occurred through monolayer adsorption on CaCO3 . Adsorbent regeneration was achieved by in situ heat treatment of the postreaction adsorbent where the adsorbed acid was converted into a ketone. The mitigation of the loss of other products was achieved by using surface modified CaCO3 materials, resulting in a significant improvement in the selectivity toward organic acid removal. The surface modification appeared to lead to formation of a metal-carboxylate intermediate consisting of both acetate and carbonate groups. Acetate group on the CaCO3 surface resulted in the suppression of side reactions. Generally, a higher acid removal was accompanied with a greater loss of other compounds, which could be tuned by using CaCO3 with different surface modification. PMID:26610070

  3. Magnetite whiskers and platelets in the ALH84001 Martian meteorite: evidence of vapor phase growth.

    PubMed

    Bradley, J P; Harvey, R P; McSween, H Y

    1996-01-01

    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

  4. Development of a polysilicon process based on chemical vapor deposition (phase 1)

    NASA Technical Reports Server (NTRS)

    Mccormick, J.; Arvidson, A.; Sawyer, D.; Plahutnik, F.

    1981-01-01

    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.

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

    NASA Technical Reports Server (NTRS)

    Mccormick, J.; Sharp, K.; Arvidson, A.; Sawyer, D.

    1981-01-01

    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.

  6. A Gas Lift Bioreactor for Removal of Contaminants from the Vapor Phase

    PubMed Central

    Ensley, B. D.; Kurisko, P. R.

    1994-01-01

    The cometabolic degradation of trichloroethylene (TCE) as a vapor by two aromatic-metabolizing pseudomonads was evaluated in an airlift reactor. These microorganisms were able to degrade 90 to 95% of TCE in air at concentrations at the reactor inlet of 300 to 4,000 ?g/liter. Although exposure of the cells to high inlet concentrations of TCE (4 mg/liter) caused a decline in enzyme-specific activity and TCE removal efficiency, this loss in activity could be prevented or delayed by increasing the rate of cosubstrate addition. Under the appropriate operating conditions, the microorganisms were able to degrade even high concentrations of TCE and activity of the cells in the reactor could be maintained for periods of at least 2 weeks. PMID:16349158

  7. Vacuum distillation/vapor filtration water recovery, phases 1 and 2

    NASA Technical Reports Server (NTRS)

    Honegger, R. J.; Remus, G. A.; Krug, E. K.

    1973-01-01

    The research is reported on the development of an evaporator for vacuum distillation/vapor filtration VD/VF water reclamation system for use on manned space flights. The design, fabrication, and tests of a six-man evaporator are described. It is concluded that: (1) A condenser with an internal rotating impeller and coolant surfaces directly opposite the condensing surfaces is an effective condenser. (2) The VD/VF evaporator, catalyst unit and condenser function satisfactorily based on thermal, mechanical and recovery performance during a 145-hour evaluation test. (3) The quality of recovered water, as measured by analyses for total organic carbon, pH, conductivity, turbidity, and viable bacteria density was within established limits for potability.

  8. Glutathionylation and Reduction of Methacrolein in Tomato Plants Account for Its Absorption from the Vapor Phase.

    PubMed

    Muramoto, Shoko; Matsubara, Yayoi; Mwenda, Cynthia Mugo; Koeduka, Takao; Sakami, Takuya; Tani, Akira; Matsui, Kenji

    2015-11-01

    A large portion of the volatile organic compounds emitted by plants are oxygenated to yield reactive carbonyl species, which have a big impact on atmospheric chemistry. Deposition to vegetation driven by the absorption of reactive carbonyl species into plants plays a major role in cleansing the atmosphere, but the mechanisms supporting this absorption have been little examined. Here, we performed model experiments using methacrolein (MACR), one of the major reactive carbonyl species formed from isoprene, and tomato (Solanum lycopersicum) plants. Tomato shoots enclosed in a jar with MACR vapor efficiently absorbed MACR. The absorption efficiency was much higher than expected from the gas/liquid partition coefficient of MACR, indicating that MACR was likely metabolized in leaf tissues. Isobutyraldehyde, isobutyl alcohol, and methallyl alcohol (MAA) were detected in the headspace and inside tomato tissues treated with MACR vapor, suggesting that MACR was enzymatically reduced. Glutathione (GSH) conjugates of MACR (MACR-GSH) and MAA (MAA-GSH) were also detected. MACR-GSH was essentially formed through spontaneous conjugation between endogenous GSH and exogenous MACR, and reduction of MACR-GSH to MAA-GSH was likely catalyzed by an NADPH-dependent enzyme in tomato leaves. Glutathionylation was the metabolic pathway most responsible for the absorption of MACR, but when the amount of MACR exceeded the available GSH, MACR that accumulated reduced photosynthetic capacity. In an experiment simulating the natural environment using gas flow, MACR-GSH and MAA-GSH accumulation accounted for 30% to 40% of the MACR supplied. These results suggest that MACR metabolism, especially spontaneous glutathionylation, is an essential factor supporting MACR absorption from the atmosphere by tomato plants. PMID:26169680

  9. A low phase noise microwave frequency synthesis for a high-performance cesium vapor cell atomic clock

    SciTech Connect

    François, B.; Boudot, R.; Calosso, C. E.; Danet, J. M.

    2014-09-15

    We report the development, absolute phase noise, and residual phase noise characterization of a 9.192 GHz microwave frequency synthesis chain devoted to be used as a local oscillator in a high-performance cesium vapor cell atomic clock based on coherent population trapping (CPT). It is based on frequency multiplication of an ultra-low phase noise 100 MHz oven-controlled quartz crystal oscillator using a nonlinear transmission line-based chain. Absolute phase noise performances of the 9.192 GHz output signal are measured to be −42, −100, −117 dB rad{sup 2}/Hz and −129 dB rad{sup 2}/Hz at 1 Hz, 100 Hz, 1 kHz, and 10 kHz offset frequencies, respectively. Compared to current results obtained in a state-of-the-art CPT-based frequency standard developed at LNE-SYRTE, this represents an improvement of 8 dB and 10 dB at f = 166 Hz and f = 10 kHz, respectively. With such performances, the expected Dick effect contribution to the atomic clock short term frequency stability is reported at a level of 6.2 × 10{sup −14} at 1 s integration time, that is a factor 3 higher than the atomic clock shot noise limit. Main limitations are pointed out.

  10. A low phase noise microwave frequency synthesis for a high-performance cesium vapor cell atomic clock.

    PubMed

    Franois, B; Calosso, C E; Danet, J M; Boudot, R

    2014-09-01

    We report the development, absolute phase noise, and residual phase noise characterization of a 9.192?GHz microwave frequency synthesis chain devoted to be used as a local oscillator in a high-performance cesium vapor cell atomic clock based on coherent population trapping (CPT). It is based on frequency multiplication of an ultra-low phase noise 100 MHz oven-controlled quartz crystal oscillator using a nonlinear transmission line-based chain. Absolute phase noise performances of the 9.192?GHz output signal are measured to be -42, -100, -117 dB?rad(2)/Hz and -129 dB?rad(2)/Hz at 1 Hz, 100 Hz, 1 kHz, and 10 kHz offset frequencies, respectively. Compared to current results obtained in a state-of-the-art CPT-based frequency standard developed at LNE-SYRTE, this represents an improvement of 8 dB and 10 dB at f = 166 Hz and f = 10 kHz, respectively. With such performances, the expected Dick effect contribution to the atomic clock short term frequency stability is reported at a level of 6.2 10(-14) at 1 s integration time, that is a factor 3 higher than the atomic clock shot noise limit. Main limitations are pointed out. PMID:25273756

  11. E-Cigarettes

    MedlinePLUS

    ... them, or whether they do help people quit smoking. However we do know about some dangers of e-cigarettes: They contain nicotine, which is addictive They contain other potentially harmful chemicals There is ...

  12. Cigarette Ads and Youth.

    ERIC Educational Resources Information Center

    Carol, Julia

    1988-01-01

    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)

  13. Analyzing Cigarette Smoke.

    ERIC Educational Resources Information Center

    Jaffe, Dan; Griffin, Dale; Ricker, Janet

    1997-01-01

    Details an activity in which students use their natural inquisitiveness about their personal environment to investigate the composition of cigarette smoke. Includes techniques for measuring tar and carbon monoxide content. (DDR)

  14. An Examination of Electronic Cigarette Content on Social Media: Analysis of E-Cigarette Flavor Content on Reddit.

    PubMed

    Wang, Lei; Zhan, Yongcheng; Li, Qiudan; Zeng, Daniel D; Leischow, Scott J; Okamoto, Janet

    2015-11-01

    In recent years, the emerging electronic cigarette (e-cigarette) marketplace has shown great development prospects all over the world. Reddit, one of the most popular forums in the world, has a very large user group and thus great influence. This study aims to gain a systematic understanding of e-cigarette flavors based on data collected from Reddit. Flavor popularity, mixing, characteristics, trends, and brands are analyzed. Fruit flavors were mentioned the most (n = 15,720) among all the posts and were among the most popular flavors (n = 2902) used in mixed blends. Strawberry and vanilla flavors were the most popular for e-juice mixing. The number of posts discussing e-cigarette flavors has increased sharply since 2014. Mt. Baker Vapor and Hangen were the most popular brands discussed among users. Information posted on Reddit about e-cigarette flavors reflected consumers' interest in a variety of flavors. Our findings suggest that Reddit could be used for data mining and analysis of e-cigarette-related content. Understanding how e-cigarette consumers' view and utilize flavors within their vaping experience and how producers and marketers use social media to promote flavors and sell products could provide valuable information for regulatory decision-makers. PMID:26610541

  15. An Examination of Electronic Cigarette Content on Social Media: Analysis of E-Cigarette Flavor Content on Reddit

    PubMed Central

    Wang, Lei; Zhan, Yongcheng; Li, Qiudan; Zeng, Daniel D.; Leischow, Scott J.; Okamoto, Janet

    2015-01-01

    In recent years, the emerging electronic cigarette (e-cigarette) marketplace has shown great development prospects all over the world. Reddit, one of the most popular forums in the world, has a very large user group and thus great influence. This study aims to gain a systematic understanding of e-cigarette flavors based on data collected from Reddit. Flavor popularity, mixing, characteristics, trends, and brands are analyzed. Fruit flavors were mentioned the most (n = 15,720) among all the posts and were among the most popular flavors (n = 2902) used in mixed blends. Strawberry and vanilla flavors were the most popular for e-juice mixing. The number of posts discussing e-cigarette flavors has increased sharply since 2014. Mt. Baker Vapor and Hangen were the most popular brands discussed among users. Information posted on Reddit about e-cigarette flavors reflected consumers’ interest in a variety of flavors. Our findings suggest that Reddit could be used for data mining and analysis of e-cigarette-related content. Understanding how e-cigarette consumers’ view and utilize flavors within their vaping experience and how producers and marketers use social media to promote flavors and sell products could provide valuable information for regulatory decision-makers. PMID:26610541

  16. E-cigarettes: methodological and ideological issues and research priorities.

    PubMed

    Etter, Jean-Franois

    2015-01-01

    Cigarette combustion, rather than either tobacco or nicotine, is the cause of a public health disaster. Fortunately, several new technologies that vaporize nicotine or tobacco, and may make cigarettes obsolete, have recently appeared. Research priorities include the effects of vaporizers on smoking cessation and initiation, their safety and toxicity, use by non-smokers, dual use of vaporizers and cigarettes, passive vaping, renormalization of smoking, and the development of messages that effectively communicate the continuum of risk for tobacco and nicotine products. A major difficulty is that we are chasing a moving target. New products constantly appear, and research results are often obsolete by the time they are published. Vaporizers do not need to be safe, only safer than cigarettes. However, harm reduction principles are often misunderstood or rejected. In the context of a fierce ideological debate, and major investments by the tobacco industry, it is crucial that independent researchers provide regulators and the public with evidence-based guidance. The methodological and ideological hurdles on this path are discussed in this commentary. PMID:25856794

  17. Hospitalized Smokers’ Expectancies for Electronic Cigarettes versus Tobacco Cigarettes

    PubMed Central

    Hendricks, Peter S.; Cases, Mallory G.; Thorne, Christopher B.; Cheong, JeeWon; Harrington, Kathleen F.; Kohler, Connie L.; Bailey, William C.

    2016-01-01

    Introduction To compare hospitalized smokers’ expectancies for electronic cigarettes (e-cigarettes) against their expectancies for tobacco cigarettes and evaluate relationships between e-cigarette expectancies and intention to use e-cigarettes. Methods Analysis of baseline data from a one-year longitudinal observational study. The setting was a tertiary care academic center hospital in the Southeastern U.S. Participants were 958 hospitalized tobacco cigarette smokers. A questionnaire of e-cigarette expectancies based on the Brief Smoking Consequences Questionnaire-Adult (BSCQ-A) was developed and administered along with the original, tobacco-specific, BSCQ-A. Intention to use e-cigarettes was assessed with a single 10-point Likert scale item. Results Participants reported significantly weaker expectancies for e-cigarettes relative to tobacco cigarettes on all 10 BSCQ-A scales. Participants held sizably weaker expectancies for the health risks of e-cigarettes (p < .001, Cohen's d = −2.07) as well as the ability of e-cigarettes to relieve negative affect (p < .001, Cohen's d = −1.01), satisfy the desire for nicotine (p < .001, Cohen's d = −.83), and taste pleasant (p < .001, Cohen's d = −.73). Among the strongest predictors of intention to use e-cigarettes were greater expectancies that e-cigarettes taste pleasant (p < .001, adjusted β = .34), relieve negative affect (p < .001, adjusted β = .32), and satisfy the desire for nicotine (p < .001, adjusted β = .31). Conclusions Hospitalizedtobacco smokers expect fewer negative and positive outcomes from e-cigarettes versus tobacco cigarettes. This suggests that e-cigarettes might be viable though imperfect substitutes for tobacco cigarettes. PMID:25452052

  18. Defect reduction of SiNx embedded m-plane GaN grown by hydride vapor phase epitaxy

    NASA Astrophysics Data System (ADS)

    Woo, Seohwi; Kim, Minho; So, Byeongchan; Yoo, Geunho; Jang, Jongjin; Lee, Kyuseung; Nam, Okhyun

    2014-12-01

    Nonpolar (1 0 -1 0) m-plane GaN has been grown on m-plane sapphire substrates by hydride vapor phase epitaxy (HVPE). We studied the defect reduction of m-GaN with embedded SiNx interlayers deposited by ex-situ metal organic chemical vapor deposition (MOCVD). The full-width at half-maximum values of the X-ray rocking curves for m-GaN with embedded SiNx along [1 1 -2 0]GaN and [0 0 0 1]GaN were reduced to 528 and 1427 arcs, respectively, as compared with the respective values of 947 and 3170 arcs, of m-GaN without SiNx. Cross-section transmission electron microscopy revealed that the basal stacking fault density was decreased by approximately one order to 5104 cm-1 due to the defect blocking of the embedded SiNx. As a result, the near band edge emission intensities of the room-temperature and low-temperature photoluminescence showed approximately two-fold and four-fold improvement, respectively.

  19. Absolute integrated intensities of vapor-phase hydrogen peroxide (H202) in the mid-infrared at atmospheric pressure

    SciTech Connect

    Johnson, Timothy J.; Sams, Robert L.; Burton, Sarah D.; Blake, Thomas A.

    2009-09-01

    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.

  20. Metal-boride phase formation on tungsten carbide (WC-Co) during microwave plasma chemical vapor deposition

    NASA Astrophysics Data System (ADS)

    Johnston, Jamin M.; Catledge, Shane A.

    2016-02-01

    Strengthening of cemented tungsten carbide by boriding is used to improve the wear resistance and lifetime of carbide tools; however, many conventional boriding techniques render the bulk carbide too brittle for extreme conditions, such as hard rock drilling. This research explored the variation in metal-boride phase formation during the microwave plasma enhanced chemical vapor deposition process at surface temperatures from 700 to 1100 °C. We showed several well-adhered metal-boride surface layers consisting of WCoB, CoB and/or W2CoB2 with average hardness from 23 to 27 GPa and average elastic modulus of 600-730 GPa. The metal-boride interlayer was shown to be an effective diffusion barrier against elemental cobalt; migration of elemental cobalt to the surface of the interlayer was significantly reduced. A combination of glancing angle X-ray diffraction, electron dispersive spectroscopy, nanoindentation and scratch testing was used to evaluate the surface composition and material properties. An evaluation of the material properties shows that plasma enhanced chemical vapor deposited borides formed at substrate temperatures of 800 °C, 850 °C, 900 °C and 1000 °C strengthen the material by increasing the hardness and elastic modulus of cemented tungsten carbide. Additionally, these boride surface layers may offer potential for adhesion of ultra-hard carbon coatings.

  1. The Validation of Vapor Phase Hydrogen Peroxide Microbial Reduction for Planetary Protection and a Proposed Vacuum Process Specification

    NASA Technical Reports Server (NTRS)

    Chung, Shirley; Barengoltz, Jack; Kern, Roger; Koukol, Robert; Cash, Howard

    2006-01-01

    The Jet Propulsion Laboratory, in conjunction with the NASA Planetary Protection Officer, has selected the vapor phase hydrogen peroxide sterilization process for continued development as a NASA approved sterilization technique for spacecraft subsystems and systems. The goal is to include this technique, with an appropriate specification, in NPR 8020.12C as a low temperature complementary technique to the dry heat sterilization process.To meet microbial reduction requirements for all Mars in-situ life detection and sample return missions, various planetary spacecraft subsystems will have to be exposed to a qualified sterilization process. This process could be the elevated temperature dry heat sterilization process (115 C for 40 hours) which was used to sterilize the Viking lander spacecraft. However, with utilization of such elements as highly sophisticated electronics and sensors in modern spacecraft, this process presents significant materials challenges and is thus an undesirable bioburden reduction method to design engineers. The objective of this work is to introduce vapor hydrogen peroxide (VHP) as an alternative to dry heat microbial reduction to meet planetary protection requirements.The VHP process is widely used by the medical industry to sterilize surgical instruments and biomedical devices, but high doses of VHP may degrade the performance of flight hardware, or compromise material properties. Our goal for this study was to determine the minimum VHP process conditions to achieve microbial reduction levels acceptable for planetary protection.

  2. Vapor liquid solid-hydride vapor phase epitaxy (VLS-HVPE) growth of ultra-long defect-free GaAs nanowires: Ab initio simulations supporting center nucleation

    NASA Astrophysics Data System (ADS)

    Andr, Yamina; Lekhal, Kaddour; Hoggan, Philip; Avit, Geoffrey; Cadiz, Fabian; Rowe, Alistair; Paget, Daniel; Petit, Elodie; Leroux, Christine; Trassoudaine, Agns; Rda Ramdani, M.; Monier, Guillaume; Colas, David; Ajib, Rabih; Castelluci, Dominique; Gil, Evelyne

    2014-05-01

    High aspect ratio, rod-like and single crystal phase GaAs nanowires (NWs) were grown by gold catalyst-assisted hydride vapor phase epitaxy (HVPE). High resolution transmission electron microscopy and micro-Raman spectroscopy revealed polytypism-free zinc blende (ZB) NWs over lengths of several tens of micrometers for a mean diameter of 50 nm. Micro-photoluminescence studies of individual NWs showed linewidths smaller than those reported elsewhere which is consistent with the crystalline quality of the NWs. HVPE makes use of chloride growth precursors GaCl of which high decomposition frequency after adsorption onto the liquid droplet catalysts, favors a direct and rapid introduction of the Ga atoms from the vapor phase into the droplets. High influxes of Ga and As species then yield high axial growth rate of more than 100 ?m/h. The diffusion of the Ga atoms in the liquid droplet towards the interface between the liquid and the solid nanowire was investigated by using density functional theory calculations. The diffusion coefficient of Ga atoms was estimated to be 3 10-9 m2/s. The fast diffusion of Ga in the droplet favors nucleation at the liquid-solid line interface at the center of the NW. This is further evidence, provided by an alternative epitaxial method with respect to metal-organic vapor phase epitaxy and molecular beam epitaxy, of the current assumption which states that this type of nucleation should always lead to the formation of the ZB cubic phase.

  3. Tribochemical polymerization of adsorbed n-pentanol on SiO2 during rubbing: when does it occur and is it responsible for effective vapor phase lubrication?

    PubMed

    Barnette, Anna L; Asay, David B; Ohlhausen, James A; Dugger, Michael T; Kim, Seong H

    2010-11-01

    The origin and role of tribochemical reaction products formed while sliding silicon oxide surfaces in the presence of adsorbed alcohol molecules in equilibrium with the vapor phase were studied. Wear and friction coefficient studies with varying contact loads and n-pentanol vapor environments were used to determine under what operating conditions the tribochemical reaction species was produced. Imaging time-of-flight secondary ion mass spectrometry and microinfrared spectroscopy found that hydrocarbon species with a molecular weight higher than the starting vapor molecules are produced when there is wear of the SiO(2) surface. When the n-pentanol vapor lubrication is effective and the silicon oxide surface does not wear, then the tribochemical polymerization products are negligible. These results imply that the tribochemical polymerization is associated with the substrate wear process occurring due to insufficient adsorbate supply or high mechanical load. The tribochemical reactions do not seem to be the primary lubrication mechanism for vapor phase lubrication of SiO(2) surfaces with alcohol, although they may lubricate the substrate momentarily upon failure of the alcohol vapor delivery to the sliding contact. PMID:20735117

  4. Amorphous and crystalline aerosol particles interacting with water vapor - Part 1: Microstructure, phase transitions, hygroscopic growth and kinetic limitations

    NASA Astrophysics Data System (ADS)

    Mikhailov, E.; Vlasenko, S.; Martin, S. T.; Koop, T.; Pöschl, U.

    2009-03-01

    Interactions with water are crucial for the properties, transformation and climate effects of atmospheric aerosols. Here we outline characteristic features and differences in the interaction of amorphous and crystalline aerosol particles with water vapor. Using a hygroscopicity tandem differential mobility analyzer (H-TDMA), we performed hydration, dehydration and cyclic hydration&dehydration experiments with aerosol particles composed of levoglucosan, oxalic acid and ammonium sulfate (diameters ~100-200 nm, relative uncertainties <0.4%, relative humidities <5% to 95% at 298 K). The measurements and accompanying Köhler model calculations provide new insights into particle microstructure, surface adsorption, bulk absorption, phase transitions and hygroscopic growth. The results of these and related investigations lead to the following main conclusions: 1. Many organic substances (including carboxylic acids, carbohydrates and proteins) tend to form amorphous rather than crystalline phases upon drying of aqueous solution droplets. Depending on viscosity and microstructure, the amorphous phases can be classified as glasses, rubbers, gels or viscous liquids. 2. Amorphous organic substances tend to absorb water vapor and undergo gradual deliquescence and hygroscopic growth at much lower relative humidity than their crystalline counterparts. 3. In the course of hydration and dehydration, certain organic substances can form rubber- or gel-like structures (supra-molecular networks) and undergo stepwise transitions between swollen and collapsed network structures. 4. Organic gels or (semi-)solid amorphous shells (glassy, rubbery, ultra-viscous) with low molecular diffusivity can kinetically limit the uptake and release of water by submicron aerosol particles on (multi-)second time scales, which may influence the hygroscopic growth and activation of aerosol particles as cloud condensation nuclei (CCN) and ice nuclei (IN). 5. The shape and porosity of amorphous and crystalline particles formed upon dehydration of aqueous solution droplets depend on chemical composition and drying conditions. The apparent volume void fractions of particles with highly porous structures can range up to ~50% or more (xerogels, aerogels). Void fractions as well as residual water in dried aerosol particles that are not water-free (due to kinetic limitations of drying or stable hydrate formation) should be taken into account in Köhler model calculations of hygroscopic growth and CCN activation. 6. For efficient description of water uptake and phase transitions of amorphous and crystalline organic and inorganic aerosol particles and particle components, we propose not to limit the terms deliquescence and efflorescence to equilibrium phase transitions of crystalline substances interacting with water vapor. Instead we propose the following generalized definitions: Deliquescence is the transformation of a (semi-)solid substance into a liquid aqueous solution, whereby water is absorbed from the gas phase ("liquefaction upon humidification/hydration"). Efflorescence is the transformation of a substance from a liquid aqueous solution into a (semi-)solid phase, whereby water is evaporated ("solidification upon drying/dehydration"). According to these definitions, individual components as well as entire aerosol particles can undergo gradual or prompt, partial or full deliquescence or efflorescence.

  5. The influence of equilibrium chemical reactions on vapor-liquid phase diagrams

    SciTech Connect

    Barbosa, D.; Doherty, M.F.

    1986-01-01

    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.

  6. Time-resolved cathodoluminescence assessment of deep-level transitions in hydride-vapor-phase-epitaxy GaN

    NASA Astrophysics Data System (ADS)

    Daz-Guerra, C.; Piqueras, J.; Cavallini, A.

    2003-03-01

    The temporal behavior of deep-level luminescence emissions in undoped hydride-vapor-phase-epitaxy GaN layers of different thicknesses has been investigated by time-resolved cathodoluminescence (TRCL). The complex nature of the yellow luminescence is revealed in the TRCL spectra by the presence of two bands peaked at 2.22 and 2.03 eV. A red band with a decay time of 700 ?s, centered at about 1.85 eV, dominates spectra recorded for long delay times. Exponential transients with associated decay times of hundreds of ?s were measured at 87 K for all the deep-level emissions found in the layers.

  7. High-quality InAs/GaAs quantum dots grown by low-pressure metalorganic vapor-phase epitaxy

    NASA Astrophysics Data System (ADS)

    Sagnes, I.; Prvot, I.; Patriarche, G.; Le Roux, G.; Gayral, B.; Lema??tre, A.; Grard, J. M.

    1998-12-01

    We report on the fabrication, at high growth temperature (685C) of low-pressure metalorganic vapor-phase epitaxy InAs quantum dots (QDs) with GaAs barriers. The 2D-3D transition of the growth mode was observed by both high-resolution X-ray diffraction spectroscopy and photoluminescence (PL) measurement. The QDs observed by TEM show a density distribution 410 7 cm -2. This density distribution is also confirmed from the analysis of PL measurements on square mesas (4040-11 ?m 2). Furthermore, we show that these QD arrays have been inserted in an AlAs/GaAs planar cavity on which we have measured a record cavity quality factor of 11?900 at 965 nm.

  8. Influence of Preparation Methods of Nano Au/MCM-41 Catalysts for Vapor Phase Oxidation of Benzyl Alcohol.

    PubMed

    Kumar, Ashish; Kumar, Vanama Pavan; Vishwanathan, Venkataraman; Chary, V R

    2015-12-01

    The Au/MCM-41 nano catalysts were synthesized from four different methods, viz., homogeneous deposition-precipitation, micro-emulsion, impregnation and polyol and their catalytic activities were tested for the vapor phase oxidation of benzyl alcohol to benzaldehyde. The physico-chemical properties of the catalysts were investigated by XRD, TEM, BET surface area, PSD, CO-chemisorption and XPS techniques. The effect of preparation methods, nature of the metal, support and the metal-support interaction in Au/MCM-41 catalysts were studied for the title reaction. The Au/MCM-41 catalysts synthesized from HDP method has shown higher and better catalytic activity as compared to the catalysts prepared by other methods. PMID:26682438

  9. Metalorganic vapor phase epitaxy of GaAs on Si using II a-flouride buffer layers

    NASA Astrophysics Data System (ADS)

    Tiwari, A. N.; Freundlich, A.; Beaumont, B.; Blunier, S.; Zogg, H.; Teodoropol, S.; Vri, C.

    1992-11-01

    Metalorganic vapor phase epitaxy has been used for the first time to grow epitaxial GaAs layers on (111) and (100) oriented Si either using CaF 2 or stacked (Ca,Sr)F 2/CaF 2 as a buffer. The GaAs layers show sharp and well resolved electron channeling patterns. The Rutherford backscattering (RBS) ion channeling minimum yield is 5% for (111) orientation and 6% for (100) orientation. The GaAs(111) layers are untwinned. The strain in the GaAs layer has been measured with RBS and X-ray diffraction and it is found that the thermal mismatch-induced strain in the GaAs layer is considerably lower than in similar GaAs films grown without flouride buffer.

  10. Testing of Performance of a Scroll Pump in Support of Improved Vapor Phase Catalytic Ammonia Removal (VPCAR) Mass Reduction

    NASA Technical Reports Server (NTRS)

    Nahra, Henry K.; Kraft, Thomas G.; Yee, Glenda F.; Jankovsky, Amy L.; Flynn, Michael

    2006-01-01

    This paper describes the results of ground testing of a scroll pump with a potential of being a substitute for the current vacuum pump of the Vapor Phase Catalytic Ammonia Reduction (VPCAR). Assessments of the pressure-time, pump-down time, pump power and the pump noise were made for three configurations of the pump the first of which was without the gas ballast, the second with the gas ballast installed but not operating and the third with the gas ballast operating. The tested scroll pump exhibited optimum characteristics given its mass and power requirements. The pump down time required to reach a pressure of 50 Torr ranged from 60 minutes without the ballast to about 120 minutes with the gas ballast operational. The noise emission and the pump power were assessed in this paper as well.

  11. Indium migration paths in V-defects of InAlN grown by metal-organic vapor phase epitaxy

    NASA Astrophysics Data System (ADS)

    Kehagias, Th.; Dimitrakopulos, G. P.; Kioseoglou, J.; Kirmse, H.; Giesen, C.; Heuken, M.; Georgakilas, A.; Neumann, W.; Karakostas, Th.; Komninou, Ph.

    2009-08-01

    InAlN thin films grown on GaN/Al2O3 (0001) templates by metal-organic vapor phase epitaxy were studied by transmission electron microscopy techniques. V-defects in the form of hexagonal inverted pyramids with {1011} sidewalls were observed on the films' surfaces linked to the termination of threading dislocations. Their origin is explained by the different surface atom mobility of In and Al and the built-in strain relaxation. Indium segregation in the films is influenced by the formation of V-defects, the edges and the apexes of which function as paths of migrating indium atoms diffusing along nanopipes formed at the open-core threading dislocations.

  12. Comparative Study on the Electronic Properties of p-Xylene Polymers Prepared by Plasma-Polymerization and Vapor Phase Pyrolysis

    NASA Astrophysics Data System (ADS)

    Takai, Yoshiaki; Mizutani, Teruyoshi; Ieda, Masayuki

    1987-06-01

    High-field conduction and photoconduction were investigated on thin polymer films prepared from p-xylene by two different polymerization processes: plasma-polymerization and vapor phase polymerization of p-xylylene bi-radicals. These processes gave amorphous and semicrystalline polymer films, respectively. The physical and chemical differences between these polymers are discussed in terms of their electronic properties. The results show that plasma-polymerization under a low discharge power at a high frequency (13.56 MHz) resulted in polymer films. Their electronic properties, determined by the short-range molecular order, were similar to those of semicrystalline poly-p-xylylene, while the properties determined by the long-range order, such as charge transport, were not.

  13. Nucleation and growth of Ag nanoparticles on amorphous carbon surface from vapor phase formed by vacuum evaporation

    NASA Astrophysics Data System (ADS)

    Gromov, Dmitry G.; Pavlova, Lydia M.; Savitsky, Andrey I.; Trifonov, Alexey Yu.

    2015-03-01

    We present the results of experimental study of Ag nanoparticle arrays on thin film of amorphous carbon. The arrays were formed by means of vapor phase deposition on non-heated substrate. The investigation was carried out using TEM technique. It has been found that the size of the particles and their surface density significantly depend on the amount of condensing substance. In particular, increasing the portion of evaporating Ag material from 5.1 to 47.5 mg results in drastic reduction of surface density of the particles from ~8,000 to ~40 m-2, whereas the predominant particle size changes from ~7 to ~60 nm. We present phenomenological description of the process: directed flow of silver atoms to growing Ag particles takes place during condensation.

  14. Thick GaN layers grown by hydride vapor-phase epitaxy: hetero- versus homo-epitaxy

    NASA Astrophysics Data System (ADS)

    Hageman, P. R.; Kirilyuk, V.; Corbeek, W. H. M.; Weyher, J. L.; Lucznik, B.; Bockowski, M.; Porowski, S.; Mller, S.

    2003-08-01

    In this paper, an overview will be given of the growth of thick GaN layers by hydride vapor-phase epitaxy. Two different kinds of substrates were used, that is MOCVD-grown GaN templates on sapphire and GaN single crystals. The layers grown on sapphire-based substrates suffer from the problem of cracking and pit formation. Although the morphology is not mirror-like, the optical and electrical quality of the material is excellent as demonstrated by photoluminescence and Hall-Van der Pauw measurements. The layers grown on Ga-polar GaN single crystals have almost perfect morphologies with only a very low density of pits. For the N-polar substrates the morphology is very rough, exhibiting the same features as are observed for the N-face MOCVD-grown GaN layers, both on sapphire and on N-face GaN single crystals.

  15. ZnO/Cu(InGa)Se.sub.2 solar cells prepared by vapor phase Zn doping

    DOEpatents

    Ramanathan, Kannan; Hasoon, Falah S.; Asher, Sarah E.; Dolan, James; Keane, James C.

    2007-02-20

    A process for making a thin film ZnO/Cu(InGa)Se.sub.2 solar cell without depositing a buffer layer and by Zn doping from a vapor phase, comprising: depositing Cu(InGa)Se.sub.2 layer on a metal back contact deposited on a glass substrate; heating the Cu(InGa)Se.sub.2 layer on the metal back contact on the glass substrate to a temperature range between about 100.degree. C. to about 250.degree. C.; subjecting the heated layer of Cu(InGa)Se.sub.2 to an evaporant species from a Zn compound; and sputter depositing ZnO on the Zn compound evaporant species treated layer of Cu(InGa)Se.sub.2.

  16. In situ reflectance monitoring of InP/InGaAsP films grown by metalorganic vapor phase epitaxy

    NASA Astrophysics Data System (ADS)

    Lum, R. M.; McDonald, M. L.; Bean, J. C.; Vandenberg, J.; Pernell, T. L.; Chu, S. N. G.; Robertson, A.; Karp, A.

    1996-08-01

    We report the use of in situ reflectance spectroscopy for real-time monitoring of the metalorganic vapor phase epitaxy (MOVPE) growth of InGaAsP films. In situ optical measurements have not been previously reported for this materials system because of its strong absorption in the spectral range of commonly available detectors (λ<1100 nm). To acquire reflectance data beyond the absorption regions of these films we used a grating spectrometer with a Si/PbS dual detector having a wavelength range of 400-2500 nm. Measurements were made during growth of InP/InGaAs/InP double heterostructures and 1.3 μm InGaAsP MQW laser device structures. The multiwavelength reflectance data enabled extraction of the film optical constants, determination of deposition rates to better than 1%, and provided nanometer scale thickness sensitivity for MQW samples.

  17. Solid- and vapor-phase antimicrobial activities of six essential oils: susceptibility of selected foodborne bacterial and fungal strains.

    PubMed

    Lpez, P; Snchez, C; Batlle, R; Nern, C

    2005-08-24

    The antimicrobial activity of essential oils (EOs) of cinnamon (Cinnamon zeylanicum), clove (Syzygium aromaticum), basil (Ocimum basillicum), rosemary (Rosmarinus officinalis), dill (Anethum graveolens), and ginger (Zingiber officinalis) was evaluated over a range of concentrations in two types of contact tests (solid and vapor diffusion). The EOs were tested against an array of four Gram-positive bacteria (Staphylococcus aureus, Bacillus cereus, Enterococcus faecalis, and Listeria monocytogenes), four Gram-negative bacteria (Escherichia coli, Yersinia enterocolitica, Salmonella choleraesuis, and Pseudomonas aeruginosa), and three fungi (a yeast, Candida albicans, and two molds, Penicillium islandicum and Aspergillus flavus). The rationale for this work was to test the possibility of creating a protective atmosphere by using natural compounds that could extend the shelf life of packaged foodstuffs while minimizing organoleptic alterations. In the solid diffusion tests, cinnamon and clove gave the strongest (and very similar) inhibition, followed by basil and rosemary, with dill and ginger giving the weakest inhibition. The fungi were the most sensitive microorganisms, followed by the Gram-positive bacterial strains. The Gram-negative strain P. aeruginosa was the least inhibited. The composition of the atmosphere generated by the EOs, and their minimum inhibitory concentrations (MICs), were determined using a disk volatilization method, in which no inhibition from rosemary or basil was observed. Cinnamon and clove, once again, gave similar results for every microorganism. As a general rule, MIC (fungi) < MIC (bacteria) with no clear differences between Gram-positive or -negative strains except for P. aeruginosa, which was not inhibited by any of the EOs in the vapor phase. The atmosphere generated from the EOs was analyzed by means of solid-phase microextraction combined with gas chromatography-ion trap mass spectrometry. Differences among the volatiles in the EOs, which may be responsible for the differences in their antimicrobial performances, were found. PMID:16104824

  18. Atmospheric mercury in the vapor phase, and in fine and coarse particulate matter at Perch River, New York

    NASA Astrophysics Data System (ADS)

    Ames, Michael; Gullu, Gulen; Olmez, Ilhan

    Daily samples of size segregated atmospheric particulate matter ( da < 2.5 ?m, and 2.5 ?m < da < 10 ?m), and vapor-phase mercury have been collected at five locations in upstate New York over a period of two years. Atmospheric concentrations were determined for mercury and, in the particulate matter, for up to 38 other elements by Instrumental Neutron Activation Analysis (INAA). At the Perch River sampling site, the average vapor-phase mercury concentration was 2.4 ng m -3 with a seasonal pattern of higher winter and lower summer concentrations observed over both years of sampling. The average fine and coarse particulate concentrations were 0.058 and 0.025 ng m -3, respectively. Concentrations for the particulate concentrations followed a log-normal frequency distribution with the most frequently occurring value for fine particulates being 0.012 ng m -3 and for coarse particulates 0.009 ng m -3. Episodic high concentrations of both fine and coarse particulate mercury indicate the impact of specific s ources. No correlation was found among the three different types of samples on either an overall or daily basis. By applying factor analysis (FA) to the data and using known marker species for specific types of emissions, the sources of the particulate mercury were identified and their contributions estimated. Fine particulate mercury concentrations were primarily associated with regional sources in the midwestern U.S.A., with copper smelting, and with the combined influence of aluminum and precious metals processing. Coarse particulate mercury concentrations were principally related to local aluminum processing facilities. The source identification results of the FA were confirmed by examining back-projected, mixed-layer wind trajectories. From February 1993 through the end of the particulate sampling in September 1993 fine particulate mercury concentrations declined significantly possibly due to the installation of particulate controls at one or more of the copper smelters.

  19. Toxicological assessment of kretek cigarettes: Part 2: kretek and American-blended cigarettes, smoke chemistry and in vitro toxicity.

    PubMed

    Piadé, J-J; Roemer, E; Dempsey, R; Hornig, G; Deger Evans, A; Völkel, H; Schramke, H; Trelles-Sticken, E; Wittke, S; Weber, S; Schorp, M K

    2014-12-01

    Two commercial kretek cigarettes typical for the Indonesian market and a reference kretek cigarette were compared to the American-blended reference cigarette 2R4F by smoke chemistry characterization and in vitro cytotoxicity and mutagenicity assessments. Despite the widely diverse designs and deliveries of the selected kretek cigarettes, their smoke composition and in vitro toxicity data present a consistent pattern when data were normalized to total particulate matter (TPM) deliveries. This confirms the applicability of the studies' conclusions to a wide range of kretek cigarette products. After normalization to TPM delivery, nicotine smoke yields of kretek cigarettes were 29-46% lower than that of the 2R4F. The yields of other nitrogenous compounds were also much lower, less than would be expected from the mere substitution of one third of the tobacco filler by clove material. Yields of light molecular weight pyrolytic compounds, notably aldehydes and hydrocarbons, were reduced, while yields of polycyclic aromatic hydrocarbons were unchanged and phenol yield was increased. The normalized in vitro toxicity was lowered accordingly, reflecting the yield reductions in gas-phase cytotoxic compounds and some particulate-phase mutagenic compounds. These results do not support a higher toxicity of the smoke of kretek cigarettes compared to American-blended cigarettes. PMID:25497993

  20. Vapor phase growth of titania whiskers by hydrolysis of titanium flouride

    NASA Astrophysics Data System (ADS)

    Oota, Toshitaka; Yamai, Iwao; Yokoyama, Mitsunori

    1984-04-01

    The chemical vapor deposition of TiO 2 crystals from the system TiF 4-H 2O was studied at elevated temperatures. When Na 2TiF 6 was used as a TiF 4 source, rutile-type TiO 2 needles grew to 30 mm in length in a comparatively short time over the melt in a platinum crucible in air. The needles were mostly skeletal or twinned intergrowths of acicular crystals. Rutile gradually changed to Na 2Ti 6O 13 by the reaction with NaF and moisture in the air. The formation of Na 2Ti 6O 13 was inhibited by addition of TiO 2 to the raw material. The rutile whiskers were grown under controlled conditions by means of a flow method from the system Na 2TiF 6-TiO 2-H 2O. The needles or whiskers were found to grow preferentially in the [001] direction.

  1. Metalorganic vapor phase epitaxy growth of ternary tetradymite Bi2Te3-xSex compounds

    NASA Astrophysics Data System (ADS)

    Kuznetsov, P. I.; Yakushcheva, G. G.; Luzanov, V. A.; Temiryazev, A. G.; Shchamkhalova, B. S.; Jitov, V. A.; Sizov, V. E.

    2015-01-01

    We report on a metal organic vapor epitaxy (MOVPE) of Bi2Te3-xSex films over the entire range of compositions (0 ? x ? 3) for the first time. The films were grown on Al2O3(0001) substrates at 465 C using trimethylbismuth (Bi2Me3), diethyltellurium (Et2Te) and diisopropylselenium (iPro2Se) as metalorganic sources. To realize the 2D growth mode and to grow films with flat surfaces and high crystalline quality, a thin ZnTe buffer layer was used. As-grown films were studied using optical and AFM microscopy techniques and X-ray diffraction. It was found that under steady growth conditions the composition of Bi2Te3-xSex films strongly depends on the film thickness. But a high rate of interdiffusion of chalcogens at the growth temperature rapidly leads to a homogeneous composition of the film in the growth direction. Dependence of the intensity of X-ray reflection (0012) on the composition of Bi2Te3-xSex films x has extremes near x=1 (Bi2Te2 Se) and x=2 (Bi2Se2 Te). The AFM micrographs and profiles show large (above 2 ?m) triangle-shaped atomically flat terraces with step height of a quintuple layer (0.90 nm) of the tetradymite-type compounds. The electronic properties of the grown films have been characterized via four probe magnetotransport measurements.

  2. Enhanced quality thin film Cu(In,Ga)Se.sub.2 for semiconductor device applications by vapor-phase recrystallization

    DOEpatents

    Tuttle, John R. (Denver, CO); Contreras, Miguel A. (Golden, CO); Noufi, Rommel (Golden, CO); Albin, David S. (Denver, CO)

    1994-01-01

    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.degree.-600.degree. 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.degree.-600.degree. C., result in a nearly stoichiometric Cu(In,Ga)Se.sub.2, whereas lower temperatures, such as 300.degree.-400.degree. C., result in a more Cu-poor compound, such as the Cu.sub.z (In,Ga).sub.4 Se.sub.7 phase.

  3. Enhanced quality thin film Cu(In,Ga)Se[sub 2] for semiconductor device applications by vapor-phase recrystallization

    DOEpatents

    Tuttle, J.R.; Contreras, M.A.; Noufi, R.; Albin, D.S.

    1994-10-18

    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.

  4. Comment on "Tunable generation and adsorption of energetic compounds in the vapor phase at trace levels: A tool for testing and developing sensitive and selective substrates for explosive detection"

    SciTech Connect

    Grate, Jay W.; Ewing, Robert G.; Atkinson, David A.

    2013-02-13

    The evaluation of developed technologies and research on new detection approaches require the ability to generate explosive vapors in the gas phase. In this correspondence, the authors comment on a technical note describing a vaopr generator, discuss safety issues associated with explosives for vapor generators, and provide a concise review of vapor generators for explosive compounds. Approaches to measuring or monitoring the output of a vapor generators are also discussed.

  5. Vapor-phase metalation by atomic layer deposition in a metal-organic framework.

    PubMed

    Mondloch, Joseph E; Bury, Wojciech; Fairen-Jimenez, David; Kwon, Stephanie; DeMarco, Erica J; Weston, Mitchell H; Sarjeant, Amy A; Nguyen, SonBinh T; Stair, Peter C; Snurr, Randall Q; Farha, Omar K; Hupp, Joseph T

    2013-07-17

    Metal-organic frameworks (MOFs) have received attention for a myriad of potential applications including catalysis, gas storage, and gas separation. Coordinatively unsaturated metal ions often enable key functional behavior of these materials. Most commonly, MOFs have been metalated from the condensed phase (i.e., from solution). Here we introduce a new synthetic strategy capable of metallating MOFs from the gas phase: atomic layer deposition (ALD). Key to enabling metalation by ALD In MOFs (AIM) was the synthesis of NU-1000, a new, thermally stable, Zr-based MOF with spatially oriented -OH groups and large 1D mesopores and apertures. PMID:23829224

  6. Collector phase transitions during vapor-solid-solid nucleation of GaN nanowires.

    PubMed

    Chze, Caroline; Geelhaar, Lutz; Trampert, Achim; Brandt, Oliver; Riechert, Henning

    2010-09-01

    We investigate the nucleation of Ni-induced GaN nanowires by in situ and ex situ experiments. Three nucleation stages are evidenced. In the first two stages, different crystal structures of the Ni collectors are identified. Real-time monitoring of the Ga desorption allows the amount of Ga incorporated in the collectors to be quantified. A transition of their crystal structure prior to nanowire growth is found to be in agreement with the thermodynamically stable phase sequence of the relevant phase diagrams. PMID:20715843

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

    SciTech Connect

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

    1983-12-15

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

  8. The gas phase emitter effect of lanthanum within ceramic metal halide lamps and its dependence on the La vapor pressure and operating frequency

    NASA Astrophysics Data System (ADS)

    Ruhrmann, C.; Hoebing, T.; Bergner, A.; Groeger, S.; Denissen, C.; Suijker, J.; Awakowicz, P.; Mentel, J.

    2015-08-01

    The gas phase emitter effect increases the lamp lifetime by lowering the work function and, with it, the temperature of the tungsten electrodes of metal halide lamps especially for lamps in ceramic vessels due to their high rare earth pressures. It is generated by a monolayer on the electrode surface of electropositive atoms of certain emitter elements, which are inserted into the lamp bulb by metal iodide salts. They are vaporized, dissociated, ionized, and deposited by an emitter ion current onto the electrode surface within the cathodic phase of lamp operation with a switched-dc or ac-current. The gas phase emitter effect of La and the influence of Na on the emitter effect of La are studied by spatially and phase-resolved pyrometric measurements of the electrode tip temperature, La atom, and ion densities by optical emission spectroscopy as well as optical broadband absorption spectroscopy and arc attachment images by short time photography. An addition of Na to the lamp filling increases the La vapor pressure within the lamp considerably, resulting in an improved gas phase emitter effect of La. Furthermore, the La vapor pressure is raised by a heating of the cold spot. In this way, conditions depending on the La vapor pressure and operating frequency are identified, at which the temperature of the electrodes becomes a minimum.

  9. Vapor-phase transport of explosives from buried sources in soils.

    PubMed

    Ravikrishna, Raghunathan; Valsaraj, Kalliat T; Price, Cynthia B; Brannon, James M; Hayes, Charolett A; Yost, Sally L

    2004-12-01

    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

  10. Membrane vapor recovery systems; Phase 1, Final report, 29 September 1990--29 April 1991

    SciTech Connect

    1991-01-01

    This report describes the work performed at Membrane Technology and Research, Inc. (MTR). The period covered is from September 29, 1990 to April 29, 1991, representing Phase 1 of the project. The overall objective of the project is the design, construct and demonstrate in the field a 50 scfm condensation/membrane separation system able to recover volatile organic compounds from effluent air streams. In the first phase of the program, a number of the high-pressure membranes modules to be installed in the system were constructed and evaluated. The results were satisfactory and no further module development work is required. The Field Demonstration Unit has also been designed. All of the major components have been selected and costed. The system can be constructed within the proposed budget. As a result of a visit to the host demonstration site (Great Lakes Chemical (GLC), El Dorado, Arkansas Plant), the Phase 2 program has been modified to include construction of small, high-pressure Field Module Evaluation Unit to be installed at GLC during the Phase 2 program. The host site engineers are prepared to install and monitor this unit. This additional work can be accomplished within the current budget and will provide valuable data prior to installation of the large Field Demonstration Unit. 18 figs., 8 tabs.

  11. NOVEL PROCESS FOR REMOVAL AND RECOVERY OF VAPOR-PHASE MERCURY

    SciTech Connect

    Craig S. Turchi

    2000-09-29

    The goal of this project is to investigate the use of a regenerable sorbent for removing and recovering mercury from the flue gas of coal-fired power plants. The process is based on the sorption of mercury by noble metals and the thermal regeneration of the sorbent, recovering the desorbed mercury in a small volume for recycling or disposal. The project was carried out in two phases, covering five years. Phase I ran from September 1995 through September 1997 and involved development and testing of sorbent materials and field tests at a pilot coal-combustor. Phase II began in January 1998 and ended September 2000. Phase II culminated with pilot-scale testing at a coal-fired power plant. The use of regenerable sorbents holds the promise of capturing mercury in a small volume, suitable for either stable disposal or recycling. Unlike single-use injected sorbents such as activated carbon, there is no impact on the quality of the fly ash. During Phase II, tests were run with a 20-acfm pilot unit on coal-combustion flue gas at a 100 lb/hr pilot combustor and a utility boiler for four months and six months respectively. These studies, and subsequent laboratory comparisons, indicated that the sorbent capacity and life were detrimentally affected by the flue gas constituents. Sorbent capacity dropped by a factor of 20 to 35 during operations in flue gas versus air. Thus, a sorbent designed to last 24 hours between recycling lasted less than one hour. The effect resulted from an interaction between SO{sub 2} and either NO{sub 2} or HCl. When SO{sub 2} was combined with either of these two gases, total breakthrough was seen within one hour in flue gas. This behavior is similar to that reported by others with carbon adsorbents (Miller et al., 1998).

  12. A smart device for label-free and real-time detection of gene point mutations based on the high dark phase contrast of vapor condensation.

    PubMed

    Zhang, Junqi; Fu, Rongxin; Xie, Liping; Li, Qi; Zhou, Wenhan; Wang, Ruliang; Ye, Jiancheng; Wang, Dong; Xue, Ning; Lin, Xue; Lu, Ying; Huang, Guoliang

    2015-10-01

    A smart device for label-free and real-time detection of gene point mutation-related diseases was developed based on the high dark phase contrast of vapor condensation. The main components of the device included a Peltier cooler and a mini PC board for image processing. Heat from the hot side of the Peltier cooler causes the fluid in a copper chamber to evaporate, and the vapor condenses on the surface of a microarray chip placed on the cold side of the cooler. The high dark phase contrast of vapor condensation relative to the analytes on the microarray chip was explored. Combined with rolling circle amplification, the device visualizes less-to-more hydrophilic transitions caused by gene trapping and DNA amplification. A lung cancer gene point mutation was analysed, proving the high selectivity and multiplex analysis capability of this low-cost device. PMID:26266399

  13. 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

    Gong, W.L.; Ewing, R.C.; Wang, L.M.

    1995-12-31

    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.

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

    SciTech Connect

    Lynn E. Katz; Kerry A. Kinney; R. S. Bowman; E. J. Sullivan

    2004-09-11

    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.

  15. Dioxins in cigarette smoke.

    PubMed

    Muto, H; Takizawa, Y

    1989-01-01

    Dioxins in cigarettes, smoke, and ash were determined using gas chromatography/mass spectrometry. The total concentration of polychlorinated dibenzo-p-dioxins (PCDDs) in cigarette smoke was approximately 5.0 micrograms/m3 at the maximum level, whereas various congeners from tetra-octa-chlorodibenzo-p-dioxin (-CDD) were detected. Particullary, the total concentration of hepta-CDD congeners was the highest among these congeners. Mass fragmentograms of various PCDD congeners were similar to those in flue gas samples collected from a municipal waste incinerator. The PCDD congeners that were not present in the cigarettes were found in the smoke samples. The 2,3,7,8-TCDD toxic equivalent value--an index for effects on humans--for total PCDDs in smoke was 1.81 ng/m3 using the toxic factor of the United States Environment Protection Agency. Daily intake of PCDDs by smoking 20 cigarettes was estimated to be approximately 4.3 pg.kg body weight/day. This value was close to that of the ADIs: 1-5 pg.kg body weight/day reported in several countries. A heretofore unrecognized health risk was represented by the presence of PCDDs in cigarette smoke. PMID:2751353

  16. Dioxins in cigarette smoke

    SciTech Connect

    Muto, H.; Takizawa, Y.

    1989-05-01

    Dioxins in cigarettes, smoke, and ash were determined using gas chromatography/mass spectrometry. The total concentration of polychlorinated dibenzo-p-dioxins (PCDDs) in cigarette smoke was approximately 5.0 micrograms/m3 at the maximum level, whereas various congeners from tetra-octa-chlorodibenzo-p-dioxin (-CDD) were detected. Particullary, the total concentration of hepta-CDD congeners was the highest among these congeners. Mass fragmentograms of various PCDD congeners were similar to those in flue gas samples collected from a municipal waste incinerator. The PCDD congeners that were not present in the cigarettes were found in the smoke samples. The 2,3,7,8-TCDD toxic equivalent value--an index for effects on humans--for total PCDDs in smoke was 1.81 ng/m3 using the toxic factor of the United States Environment Protection Agency. Daily intake of PCDDs by smoking 20 cigarettes was estimated to be approximately 4.3 pg.kg body weight/day. This value was close to that of the ADIs: 1-5 pg.kg body weight/day reported in several countries. A heretofore unrecognized health risk was represented by the presence of PCDDs in cigarette smoke.

  17. Molecular simulation of water vapor-liquid phase interfaces using TIP4P/2005 model

    NASA Astrophysics Data System (ADS)

    Plankov, Barbora; Vin, Vclav; Hrub, Jan; Duka, Michal; N?mec, Tom; Celn, David

    2015-05-01

    Molecular dynamics simulations for water were run using the TIP4P/2005 model for temperatures ranging from 250 K to 600 K. The density profile, the surface tension and the thickness of the phase interface were calculated as preliminary results. The surface tension values matched nicely with the IAPWS correlation over wide range of temperatures. As a partial result, DL_POLY Classis was successfully used for tests of the new computing cluster in our institute.

  18. A study of the liquid-vapor phase change of mercury based on irreversible thermodynamics.

    NASA Technical Reports Server (NTRS)

    Adt, R. R., Jr.; Hatsopoulos, G. N.; Bornhorst, W. J.

    1972-01-01

    The object of this work is to determine the transport coefficients which appear in linear irreversible-thermodynamic rate equations of a phase change. An experiment which involves the steady-state evaporation of mercury was performed to measure the principal transport coefficient appearing in the mass-rate equation and the coupling transport coefficient appearing in both the mass-rate equation and the energy-rate equation. The principal transport coefficient sigma, usually termed the 'condensation' or 'evaporation' coefficient, is found to be approximately 0.9, which is higher than that measured previously in condensation-of-mercury experiments. The experimental value of the coupling coefficient K does not agree with the value predicted from Schrage's kinetic analysis of the phase change. A modified kinetic analysis in which the Onsager reciprocal law and the conservation laws are invoked is presented which removes this discrepancy but which shows that the use of Schrage's equation for predicting mass rates of phase change is a good approximation.

  19. Membrane vapor recovery systems. Phase 2, Progress report, 1 October 1991--29 September 1992

    SciTech Connect

    Baker, R.W.; Davidson, J.E.; Helm, V.D.; Hofmann, T.R.; Kamaruddin, H.D.; Kaschemekat, J.; Olsen, R.P.; Rose, M.E.; Wijmans, J.G.

    1992-12-31

    This report describes Phase II of a project to design, construct, and demonstrate in the membrane separation system able to recover volatile organic compounds field a condensation/membrane separation system able to recover volatile organic compounds from effluent air streams. In the first phase of the program, a number of the high-pressure membrane modules to be installed in the system were constructed and evaluated, and the Field Demonstration Unit was designed. In the second phase, the Field Demonstration System was constructed and operated at MTR`s laboratories with perchloroethylene, trichlorotrifluoroethane, and hexane, representative of chlorinated hydrocarbons, chlorofluorocarbons and fuel hydrocarbons, respectively. VOC removal from the feed stram was between 80% and 99.8%. Removal increased with increasing VOC content and with decreasing VOC volatility. A Module Field Evaluation Unit was also constructed for testing at the El Dorado plant of Great Lakes Chemical Corporation. The system, consisting of one membrane module housing containing one module insert, is installed on the pressurized vent from a condenser.

  20. E-Cigarettes (For Teens)

    MedlinePLUS

    ... nicotine — a highly addictive drug — into your body. Electronic cigarettes are battery-powered smoking devices often designed ... an unhealthy dose of nicotine and other chemicals. Electronic cigarettes started out being marketed to smokers as ...

  1. E-Cigarettes (For Parents)

    MedlinePLUS

    ... nicotine a highly addictive drug into the body. Electronic cigarettes are battery-powered smoking devices often designed ... an unhealthy dose of nicotine and other chemicals. Electronic cigarettes started out being marketed to smokers as ...

  2. E-Cigarettes (For Teens)

    MedlinePLUS

    ... nicotine a highly addictive drug into your body. Electronic cigarettes are battery-powered smoking devices often designed ... an unhealthy dose of nicotine and other chemicals. Electronic cigarettes started out being marketed to smokers as ...

  3. Cardiology Patient Page: Electronic Cigarettes

    MedlinePLUS

    ... al). 1 E-cigarettes are aggressively advertised on television, on the radio, on the Internet, and in ... to the same restrictions (including being prohibited on television and radio) as cigarette advertising, and the use ...

  4. E-Cigarettes: The Facts

    MedlinePLUS

    ... involve children. Fourth Section, Left graph: Advertising and Sales of e-cigarettes are rising rapidly with significant ... on e-cigarette advertising. Fourth Section, Right graph: Sales have experienced exponential growth in just five years. ...

  5. Vapor-Phase Transport in the Near-Drift Environment at Yucca Mountain

    NASA Astrophysics Data System (ADS)

    Salve, R.; Kneafsey, T. J.

    2003-12-01

    Yucca Mountain, located 160 km north of Las Vegas, Nevada, is currently being assessed as a potential site for disposal of spent nuclear fuel and high-level radioactive waste. A key issue regarding repository performance is the likelihood of precipitation percolating a vertical distance of ~300 m through unsaturated rock into drifts containing the waste packages. The amount of water that flows into drifts is thought to control the corrosion rates of waste packages, and the mobilization and transport of radionuclides. Subsequently, much effort has been directed towards estimating seepage from the near-drift environment into underground openings. While no naturally occurring seepage has been observed in the excavated tunnels and cavities at Yucca Mountain, numerical studies show that seepage can occur at steady-state percolation fluxes of tens of millimeters per year. However, under current conditions, the potential for seepage to occur naturally is greatly reduced, because of increased evaporation in the drifts resulting from ventilation. This presentation includes observations made over a period of four years along the terminal 944 m of a 2.7 km long tunnel within Yucca Mountain, commonly referred to as the Enhanced Characterization of the Repository Block which was initially excavated to study seepage into unventilated drifts. This initial objective was expanded to include an evaluation of the near-drift microclimates after large sections of the nonventilated drift were observed to be damp, or coated with beads of water, or even occasionally puddled. Observations from this effort indicate that fractures in the unsaturated zone can be primary paths for vapor flow in the immediate vicinity of emplacement drifts which is contrary to conceptual models of liquid traveling through fractures before seeping into the drifts. This work was supported by the Director, Office of Civilian Radioactive Waste Management, U.S. Department of Energy, through Memorandum Purchase Order EA9013MC5X between Bechtel SAIC Company, LLC, and the Ernest Orlando Lawrence Berkeley National Laboratory (Berkeley Lab). The support is provided to Berkeley Lab through the U.S. Department of Energy Contract No. DE-AC03-76SF00098.

  6. Vapor-phase synthesis of a solid precursor for {alpha}-alumina through a catalytic decomposition of aluminum triisopropoxide

    SciTech Connect

    Nguyen, Tu Quang; Park, Kyun Young; Jung, Kyeong Youl; Cho, Sung Baek

    2011-12-15

    Highlights: Black-Right-Pointing-Pointer A new solid precursor for {alpha}-alumina was prepared at about 200 Degree-Sign C from aluminum tri-isopropoxide vapor. Black-Right-Pointing-Pointer The obtained precursor was calcined at 1200 Degree-Sign C to form {alpha}-alumina particles, 75 nm in surface area equivalent diameter. Black-Right-Pointing-Pointer The weight loss of the precursor upon calcination was 24%, lower than that of Al(OH){sub 3}, a conventional alumina precursor. -- Abstract: A new solid precursor, hydrous aluminum oxide, for {alpha}-alumina nanoparticles was prepared by thermal decomposition of aluminum triisopropoxide (ATI) vapor in a 500 mL batch reactor at 170-250 Degree-Sign C with HCl as catalyst. The conversion of ATI increased with increasing temperature and catalyst content; it was nearly complete at 250 Degree-Sign C with the catalyst at 10 mol% of the ATI. The obtained precursor particles were amorphous, spherical and loosely agglomerated. The primary particle size is in the range 50-150 nm. The ignition loss of the precursor was 24%, considerably lower than 35% of Al(OH){sub 3}, the popular precursor for alumina particles. Upon calcination of the precursor at 1200 Degree-Sign C in the air with a heating rate of 10 Degree-Sign C/min and a holding time of 2 h, the phase was completely transformed into {alpha}. The spherical particles composing the precursor turned worm-like by the calcination probably due to sintering between neighboring particles. The surface area equivalent diameter of the resulting {alpha}-alumina was 75 nm.

  7. Photoreflectance analysis of annealed vanadium-doped GaAs thin films grown by metalorganic vapor phase epitaxy

    NASA Astrophysics Data System (ADS)

    Fitouri, H.; Bilel, C.; Zaied, I.; Bchetnia, A.; Rebey, A.; El Jani, B.

    2015-09-01

    In this study, we investigate the optical properties of annealed vanadium-doped GaAs films grown on GaAs substrates by metalorganic vapor phase epitaxy. The temperature dependence of the photoreflectance (PR) of as-grown GaAs:V films has been studied. We used the fit with Third-Derivative Functional Form model to evaluate the physical parameters. The temperature dependence of band gap and spin-orbit energies can be described by the Bose-Einstein statistical expression. The PR spectra of the samples are measured after thermal annealing in order to check any improvement in the optical quality of the material. The PR signal amplitude of GaAs:V samples decreased after thermal annealing. Degradation of the PR signal for annealing temperature at about 850 C is observed revealing a poor quality of the layer surface states and an important density of the recombination centers. The lock-in phase analysis of PR spectra allows to determine the time constant for GaAs:V sample before and after thermal annealing.

  8. Controlling the group II composition in CdZnTe alloys grown by organometallic vapor phase epitaxy: a kinetic model

    NASA Astrophysics Data System (ADS)

    Kappers, Menno J.; McDaniel, Anthony H.; Hicks, Robert F.

    1996-03-01

    The organometallic vapor phase epitaxy (OMVPE) of CdTe and ZnTe has been examined in a hot-wall, laminar-flow reactor. It was found that cadmium and zinc are produced in excess on the film surface during OMVPE. The excess group II elements sublime off the surface and are deposited downstream on the cold reactor walls. Based on these and other results, a kinetic model has been derived for CdZnTe OMVPE. The elementary reactions included in this model are the adsorption of the organometallic precursors, the desorption of the alkyl ligands, film growth, and the desorption of Zn and Cd metal. The predictions of the model have been compared to the Zn segregation data reported in the literature. This analysis reveals that the distribution of the group II elements between phases is relatively insensitive to the process conditions, i.e. temperature and {VI}/{II} ratio. However, it is strongly influenced by the intrinsic kinetic parameters, i.e. the difference in the Zn and Cd sublimation energies and the relative sticking probabilities of the organometallic precursors.

  9. Riemannian geometry study of vapor-liquid phase equilibria and supercritical behavior of the Lennard-Jones fluid.

    PubMed

    May, Helge-Otmar; Mausbach, Peter

    2012-03-01

    The behavior of thermodynamic response functions and the thermodynamic scalar curvature in the supercritical region have been studied for a Lennard-Jones fluid based on a revised modified Benedict-Webb-Rubin equation of state. Response function extrema are sometimes used to estimate the Widom line, which is characterized by the maxima of the correlation lengths. We calculated the Widom line for the Lennard-Jones fluid without using any response function extrema. Since the volume of the correlation length is proportional to the Riemannian thermodynamic scalar curvature, the locus of the Widom line follows the slope of maximum curvature. We show that the slope of the Widom line follows the slope of the isobaric heat capacity maximum only in the close vicinity of the critical point and that, therefore, the use of response function extrema in this context is problematic. Furthermore, we constructed the vapor-liquid coexistence line for the Lennard-Jones fluid using the fact that the correlation length, and therefore the thermodynamic scalar curvature, must be equal in the two coexisting phases. We compared the resulting phase envelope with those from simulation data where multiple histogram reweighting was used and found striking agreement between the two methods. PMID:22587083

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

    USGS Publications Warehouse

    Amos, R.T.; Mayer, K.U.; Bekins, B.A.; Delin, G.N.; Williams, R.L.

    2005-01-01

    [1] 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. Copyright 2005 by the American Geophysical Union.

  11. SIMULTANEOUS QUANTIFICATION OF JASMONIC ACID AND SALICYLIC ACID IN PLANTS BY VAPOR PHASE EXTRACTION AND GAS CHROMATOGRAPHY-CHEMICAL IONIZATION-MASS SPECTROMETRY

    Technology Transfer Automated Retrieval System (TEKTRAN)

    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 chemic...

  12. Effect of Mo Dispersion Size and Water Vapor on Oxidation of Two-Phase Directionally Solidified NiAl-9Mo In-Situ Composites

    SciTech Connect

    Brady, Michael P; Bei, Hongbin; Meisner, Roberta Ann; Lance, Michael J; Tortorelli, Peter F

    2014-01-01

    Oxidation of two-phase NiAl-9Mo eutectics with 3 different growth rates/2nd phase Mo dispersion sizes were investigated at 900 C in air and air with 10% water vapor. Good oxidation resistance via alumina formation was observed in dry air, with Mo volatilization loss minimized by fine submicron Mo dispersions. However, extensive Mo volatilization and in-place internal oxidation of prior Mo phase regions was observed in wet air oxidation. Ramifications of this phenomenon for the development of multi-phase high-temperature alloys are discussed

  13. Development of a water recovery subsystem based on Vapor Phase Catalytic Ammonia Removal (VPCAR)

    NASA Technical Reports Server (NTRS)

    Budininkas, P.; Rasouli, F.; Wydeven, T.

    1986-01-01

    An integrated engineering breadboard subsystem for the recovery of potable water from untreated urine was designed, fabricated and tested. It was fabricated from commercially available components without emphasis on weight, volume and power requirement optimization. Optimizing these parameters would make this process competitive with other spacecraft water recovery systems. Unlike other phase change systems, this process is based on the catalytic oxidation at elevated temperatures of ammonia and volatile hydrocarbons to innocuous products; therefore, no urine pretreatment is required. The testing program consisted of parametric tests, one month of daily tests, and a continuous run of 165 hours. The recovered water is low in ammonia, hydrocarbons and conductivity and requires only adjustment of its pH to meet drinking water standards.

  14. Arctic Gas Phase Water Vapor Measurements from the NASA DC-8 During SOLVE

    NASA Technical Reports Server (NTRS)

    Podolske, James; Sachse, Glen; Hipskind, R. Stephen (Technical Monitor)

    2000-01-01

    The NASA Langley / Ames Diode Laser Hygrometer (DLH) was flown aboard the NASA DC-8 during all three arctic deployments of the SOLVE campaign. The DLH measures gas phase H2O in the freestream air between the fuselage and the outer right engine cowling, essentially free from aircraft perturbations. It uses wavelength-modulated near-IR laser radiation at about 1.4 microns to detect the H2O absorption. Calibration is based on short path experiments in the laboratory using a NIST-traceable dewpoint hygrometer with carefully conditioned air at dewpoints between - 10 and + 10 degrees C. The theory of operation of the DLH instrument will be presented, along with a description of the calibration methodology. A simple climatology of H2O observations from SOLVE will be presented.

  15. A model for arsenic anti-site incorporation in GaAs grown by hydride vapor phase epitaxy

    SciTech Connect

    Schulte, K. L.; Kuech, T. F.

    2014-12-28

    GaAs growth by hydride vapor phase epitaxy (HVPE) has regained interest as a potential route to low cost, high efficiency thin film photovoltaics. In order to attain the highest efficiencies, deep level defect incorporation in these materials must be understood and controlled. The arsenic anti-site defect, As{sub Ga} or EL2, is the predominant deep level defect in HVPE-grown GaAs. In the present study, the relationships between HVPE growth conditions and incorporation of EL2 in GaAs epilayers were determined. Epitaxial n-GaAs layers were grown under a wide range of deposition temperatures (T{sub D}) and gallium chloride partial pressures (P{sub GaCl}), and the EL2 concentration, [EL2], was determined by deep level transient spectroscopy. [EL2] agreed with equilibrium thermodynamic predictions in layers grown under conditions in which the growth rate, R{sub G}, was controlled by conditions near thermodynamic equilibrium. [EL2] fell below equilibrium levels when R{sub G} was controlled by surface kinetic processes, with the disparity increasing as R{sub G} decreased. The surface chemical composition during growth was determined to have a strong influence on EL2 incorporation. Under thermodynamically limited growth conditions, e.g., high T{sub D} and/or low P{sub GaCl}, the surface vacancy concentration was high and the bulk crystal was close to equilibrium with the vapor phase. Under kinetically limited growth conditions, e.g., low T{sub D} and/or high P{sub GaCl}, the surface attained a high GaCl coverage, blocking As adsorption. This competitive adsorption process reduced the growth rate and also limited the amount of arsenic that incorporated as As{sub Ga}. A defect incorporation model which accounted for the surface concentration of arsenic as a function of the growth conditions, was developed. This model was used to identify optimal growth parameters for the growth of thin films for photovoltaics, conditions in which a high growth rate and low [EL2] could be attained.

  16. Vapor liquid solid-hydride vapor phase epitaxy (VLS-HVPE) growth of ultra-long defect-free GaAs nanowires: Ab initio simulations supporting center nucleation

    SciTech Connect

    André, Yamina Lekhal, Kaddour; Hoggan, Philip; Avit, Geoffrey; Réda Ramdani, M.; Monier, Guillaume; Colas, David; Ajib, Rabih; Castelluci, Dominique; Gil, Evelyne; Cadiz, Fabian; Rowe, Alistair; Paget, Daniel; Petit, Elodie; Leroux, Christine; Trassoudaine, Agnès

    2014-05-21

    High aspect ratio, rod-like and single crystal phase GaAs nanowires (NWs) were grown by gold catalyst-assisted hydride vapor phase epitaxy (HVPE). High resolution transmission electron microscopy and micro-Raman spectroscopy revealed polytypism-free zinc blende (ZB) NWs over lengths of several tens of micrometers for a mean diameter of 50 nm. Micro-photoluminescence studies of individual NWs showed linewidths smaller than those reported elsewhere which is consistent with the crystalline quality of the NWs. HVPE makes use of chloride growth precursors GaCl of which high decomposition frequency after adsorption onto the liquid droplet catalysts, favors a direct and rapid introduction of the Ga atoms from the vapor phase into the droplets. High influxes of Ga and As species then yield high axial growth rate of more than 100 μm/h. The diffusion of the Ga atoms in the liquid droplet towards the interface between the liquid and the solid nanowire was investigated by using density functional theory calculations. The diffusion coefficient of Ga atoms was estimated to be 3 × 10{sup −9} m{sup 2}/s. The fast diffusion of Ga in the droplet favors nucleation at the liquid-solid line interface at the center of the NW. This is further evidence, provided by an alternative epitaxial method with respect to metal-organic vapor phase epitaxy and molecular beam epitaxy, of the current assumption which states that this type of nucleation should always lead to the formation of the ZB cubic phase.

  17. Organic Vapor Phase Deposition (OVPD) for efficient OLED manufacturing: the specific advantages and possibilities of carrier-gas enhanced vapor phase deposition for the manufacturing of organic thin film devices

    NASA Astrophysics Data System (ADS)

    Kreis, Juergen; Schwambera, Markus; Keiper, Dietmar; Gersdorff, Markus; Long, Michael; Heuken, Michael

    2012-09-01

    Being introduced more than 20 years ago, OLEDs have seen a strong push in particular in the last two years, mostly driven by key players in the flat panel display industry. The majority of OLEDs manufactured today are deposited by vacuum thermal evaporation (VTE). Whilst this approach enables the making of high-performance devices scaling up of this approach has met new challenges when substrate dimensions are exceeding the "proof-of-principle" dimensions of pilot lines. Total production costs are increasingly moving into the focus of consideration. With Organic Vapor Phase Deposition (OVPD), AIXTRON has commercialized the principle of utilizing inert carriergas for the transport and controlled condensation of small molecules. While the original concept had been proposed by Prof. Steven Forrest at Princeton University, AIXTRON added its expertise in scaling gas phase processes to make this technology applicable for high-throughput production. Combining the basic concept of OVPD with AIXTRON's comprehensive expertise in utilizing close coupled showerheads and the underlying scaling rules, the disruptive approach offers a number of significant advantages: 1) decoupling of evaporation source and deposition system: additional freedom and independent optimization of source design and deposition area; 2) Utilization of carrier-gas for a more efficient evaporation, potentially increasing process windows; 3) Close-coupled showerhead approach realizes high material utilization with homogeneity; 4) Control of deposition rates by carrier-gas flow instead of the evaporation temperature enables precise rates control, co-deposition of various materials at changing rates. This paper will discuss the most significant differences compared to VTE and explain how the approach addresses requirements for efficient scaling as well as enabling advanced structure designs.

  18. Simultaneous imaging of fuel vapor mass fraction and gas-phase temperature inside gasoline sprays using two-line excitation tracer planar laser-induced fluorescence.

    PubMed

    Zigan, Lars; Trost, Johannes; Leipertz, Alfred

    2016-02-20

    This paper reports for the first time, to the best of our knowledge, on the simultaneous imaging of the gas-phase temperature and fuel vapor mass fraction distribution in a direct-injection spark-ignition (DISI) spray under engine-relevant conditions using tracer planar laser-induced fluorescence (TPLIF). For measurements in the spray, the fluorescence tracer 3-pentanone is added to the nonfluorescent surrogate fuel iso-octane, which is excited quasi-simultaneously by two different excimer lasers for two-line excitation LIF. The gas-phase temperature of the mixture of fuel vapor and surrounding gas and the fuel vapor mass fraction can be calculated from the two LIF signals. The measurements are conducted in a high-temperature, high-pressure injection chamber. The fluorescence calibration of the tracer was executed in a flow cell and extended significantly compared to the existing database. A detailed error analysis for both calibration and measurement is provided. Simultaneous single-shot gas-phase temperature and fuel vapor mass fraction fields are processed for the assessment of cyclic spray fluctuations. PMID:26906600

  19. Graphical Interface for the Study of Gas-Phase Reaction Kinetics: Cyclopentene Vapor Pyrolysis

    NASA Astrophysics Data System (ADS)

    Marcotte, Ronald E.; Wilson, Lenore D.

    2001-06-01

    The undergraduate laboratory experiment on the pyrolysis of gaseous cyclopentene has been modernized to improve safety, speed, and precision and to better reflect the current practice of physical chemistry. It now utilizes virtual instrument techniques to create a graphical computer interface for the collection and display of experimental data. An electronic pressure gauge has replaced the mercury manometer formerly needed in proximity to the 500 C pyrolysis oven. Students have much better real-time information available to them and no longer require multiple lab periods to get rate constants and acceptable Arrhenius parameters. The time saved on manual data collection is used to give the students a tour of the computer interfacing hardware and software and a hands-on introduction to gas-phase reagent preparation using a research-grade high-vacuum system. This includes loading the sample, degassing it by the freeze-pump-thaw technique, handling liquid nitrogen and working through the logic necessary for each reconfiguration of the diffusion pump section and the submanifolds.

  20. Resonant acoustic measurement of vapor phase transport phenomenon in porous media

    NASA Astrophysics Data System (ADS)

    Schuhmann, Richard; Garrett, Steven

    2002-05-01

    Diffusion of gases through porous media is commonly described using Fick's law and is characterized by a gas diffusion coefficient modified by a media-specific tortuosity parameter. A phase-locked-loop resonance frequency tracker [J. Acoust. Soc. Am. 108, 2520 (2000)] has been upgraded with an insulated copper resonator and a bellows-sealed piston instrumented with an accelerometer. Average system stability (temperature divided by frequency squared) is about 180 ppm. Glass-bead-filled cores of different lengths are fitted into an o-ring sealed opening at the top of the resonator. The rate at which the tracer gas is replaced by air within the resonator is controlled by the core's diffusion constant. Mean molecular weight of the gas mixture in the resonator is determined in real time from the ratio of the absolute temperature to the square of the fundamental acoustic resonance frequency. Molecular weight of the gas mixture is determined approximately six times per minute. Changes in the gas mixture concentration are exponential in time (within 0.1%) over nearly two decades in concentration. We will report diffusion constants for two different sizes of glass beads, in samples of five different lengths, using two different tracer gases, to establish the validity of this approach. [Work supported by ONR.