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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. An ex vivo approach to the differential parenchymal responses induced by cigarette whole smoke and its vapor phase.

    PubMed

    Lin, James Chi-Jen; Roy, Jean-Philippe; Verreault, Jules; Talbot, Sébastien; Côté, France; Couture, Réjean; Morin, André

    2012-03-11

    Using a rat lung slice model, this study compared the stress responses induced by cigarette whole smoke (WS) to that induced by the vapor phase (VP) of the smoke. Following a 3-day exposure, lung slices exposed to 4, 10 and 20% WS retained 85, 42 and 16% relative survival respectively in comparison to the air-exposed ones. Consistently, histological observations revealed concentration-related alveolar damages in the lung slices. Expression of 5 stress-response genes was examined following a single 30 min exposure to 4% WS or VP. WS exposure resulted in 4, 11 and 50-fold induction of IL-1β, kinin type I receptor (B₁R) and CYP1A1 genes, respectively, while CYP1B1 and TNF-α genes expression was found only two times higher in comparison to VP group. Since cigarette WS consists of particulate and vapor phases, these results highlight the preferential or synergistic role of the particulate phase in the induction of IL-1β, B₁R and CYP1A1 genes and that VP did not have comparable effects on expression of these genes. However, both phases fairly contributed to the induction of CYP1B1 and TNF-α genes. VP was the fraction responsible for the toxic effect since WS did not produce further toxicity. The 4% whole smoke deposited about 7.1 μg/cm² of total particulate matter (TPM) to the exposure chamber which may account for observed differential stress responses in the lung slices.

  3. 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

  4. 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.

  5. 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.

  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; Förster, Christine; Branscheid, Detlev; Aufderheide, Michaela

    2015-04-08

    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.

  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

  8. Comparison of cellular and transcriptomic effects between electronic cigarette vapor and cigarette smoke in human bronchial epithelial cells.

    PubMed

    Anthérieu, Sébastien; Garat, Anne; Beauval, Nicolas; Soyez, Mélissa; Allorge, Delphine; Garçon, Guillaume; Lo-Guidice, Jean-Marc

    2017-01-05

    The use of electronic cigarette (e-cig) can be considered as an alternative to smoking. However, due to a lack of thorough toxicological studies, absolute safety of these products cannot be guaranteed. The aim of this in vitro work was to investigate the potential toxicity of e-vapors generated by a smoking machine in human bronchial epithelial BEAS-2B cells cultured at air-liquid interface, in comparison to cigarette smoke (CS). Although CS decreased strongly cell viability from 48min exposure, e-vapors induced no cytotoxicity up to 288min exposure. Moreover, oxidative stress was evidenced only after exposure to CS, with a decrease secretion of GRO-ɑ from 8min and of IL-8 and MCP-1 after 48min exposure. Only a low increase of IL-6 secretion was measured in cells exposed to e-vapors. Finally, transcriptomic data of exposed cells indicated that a large number of genes were deregulated in response to CS, especially genes involved in important biological functions as oxidative stress and cell death, while e-vapors elicited very discrete modulation. These results strongly suggest a lower toxicity of e-vapors compared to CS in the BEAS-2B cell line and constitute a baseline for further experimental studies with a larger spectrum of e-liquids and e-cig models.

  9. E-Cigarette Vapor Induces an Apoptotic Response in Human Gingival Epithelial Cells Through the Caspase-3 Pathway.

    PubMed

    Rouabhia, Mahmoud; Park, Hyun Jin; Semlali, Abdelhabib; Zakrzewski, Andrew; Chmielewski, Witold; Chakir, Jamila

    2017-06-01

    Electronic cigarettes represent an increasingly significant proportion of today's consumable tobacco products. E-cigarettes contain several chemicals which may promote oral diseases. The aim of this study was to investigate the effect of e-cigarette vapor on human gingival epithelial cells. Results show that e-cigarette vapor altered the morphology of cells from small cuboidal form to large undefined shapes. Both single and multiple exposures to e-cigarette vapor led to a bulky morphology with large faint nuclei and an enlarged cytoplasm. E-cigarette vapor also increased L-lactate dehydrogenase (LDH) activity in the targeted cells. This activity was greater with repeated exposures. Furthermore, e-cigarette vapor increased apoptotic/necrotic epithelial cell percentages compared to that observed in the control. Epithelial cell apoptosis was confirmed by TUNEL assay showing that exposure to e-cigarette vapor increased apoptotic cell numbers, particularly after two and three exposures. This negative effect involved the caspase-3 pathway, the activity of which was greater with repeated exposure and which decreased following the use of caspase-3 inhibitor. The adverse effects of e-cigarette vapor on gingival epithelial cells may lead to dysregulated gingival cell function and result in oral disease. J. Cell. Physiol. 232: 1539-1547, 2017. © 2016 Wiley Periodicals, Inc.

  10. 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.

  11. Transcriptome sequencing reveals e-cigarette vapor and mainstream-smoke from tobacco cigarettes activate different gene expression profiles in human bronchial epithelial cells

    PubMed Central

    Shen, Yifei; Wolkowicz, Michael J.; Kotova, Tatyana; Fan, Lonjiang; Timko, Michael P.

    2016-01-01

    Electronic cigarettes (e-cigarettes) generate an aerosol vapor (e-vapor) thought to represent a less risky alternative to main stream smoke (MSS) of conventional tobacco cigarettes. RNA-seq analysis was used to examine the transcriptomes of differentiated human bronchial epithelial (HBE) cells exposed to air, MSS from 1R5F tobacco reference cigarettes, and e-vapor with and without added nicotine in an in vitro air-liquid interface model for cellular exposure. Our results indicate that while e-vapor does not elicit many of the cell toxicity responses observed in MSS-exposed HBE cells, e-vapor exposure is not benign, but elicits discrete transcriptomic signatures with and without added nicotine. Among the cellular pathways with the most significantly enriched gene expression following e-vapor exposure are the phospholipid and fatty acid triacylglycerol metabolism pathways. Our data suggest that alterations in cellular glycerophopholipid biosynthesis are an important consequences of e-vapor exposure. Moreover, the presence of nicotine in e-vapor elicits a cellular response distinct from e-vapor alone including alterations of cytochrome P450 function, retinoid metabolism, and nicotine catabolism. These studies establish a baseline for future analysis of e-vapor and e-vapor additives that will better inform the FDA and other governmental bodies in discussions of the risks and future regulation of these products. PMID:27041137

  12. Transcriptome sequencing reveals e-cigarette vapor and mainstream-smoke from tobacco cigarettes activate different gene expression profiles in human bronchial epithelial cells.

    PubMed

    Shen, Yifei; Wolkowicz, Michael J; Kotova, Tatyana; Fan, Lonjiang; Timko, Michael P

    2016-04-04

    Electronic cigarettes (e-cigarettes) generate an aerosol vapor (e-vapor) thought to represent a less risky alternative to main stream smoke (MSS) of conventional tobacco cigarettes. RNA-seq analysis was used to examine the transcriptomes of differentiated human bronchial epithelial (HBE) cells exposed to air, MSS from 1R5F tobacco reference cigarettes, and e-vapor with and without added nicotine in an in vitro air-liquid interface model for cellular exposure. Our results indicate that while e-vapor does not elicit many of the cell toxicity responses observed in MSS-exposed HBE cells, e-vapor exposure is not benign, but elicits discrete transcriptomic signatures with and without added nicotine. Among the cellular pathways with the most significantly enriched gene expression following e-vapor exposure are the phospholipid and fatty acid triacylglycerol metabolism pathways. Our data suggest that alterations in cellular glycerophopholipid biosynthesis are an important consequences of e-vapor exposure. Moreover, the presence of nicotine in e-vapor elicits a cellular response distinct from e-vapor alone including alterations of cytochrome P450 function, retinoid metabolism, and nicotine catabolism. These studies establish a baseline for future analysis of e-vapor and e-vapor additives that will better inform the FDA and other governmental bodies in discussions of the risks and future regulation of these products.

  13. Vapors-liquid phase separator

    NASA Astrophysics Data System (ADS)

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

    1980-10-01

    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.

  14. Vaporous Marketing: Uncovering Pervasive Electronic Cigarette Advertisements on Twitter

    PubMed Central

    Jones, Chris A.; Williams, Jake Ryland; Kurti, Allison N.; Norotsky, Mitchell Craig; Danforth, Christopher M.; Dodds, Peter Sheridan

    2016-01-01

    Background Twitter has become the “wild-west” of marketing and promotional strategies for advertisement agencies. Electronic cigarettes have been heavily marketed across Twitter feeds, offering discounts, “kid-friendly” flavors, algorithmically generated false testimonials, and free samples. Methods All electronic cigarette keyword related tweets from a 10% sample of Twitter spanning January 2012 through December 2014 (approximately 850,000 total tweets) were identified and categorized as Automated or Organic by combining a keyword classification and a machine trained Human Detection algorithm. A sentiment analysis using Hedonometrics was performed on Organic tweets to quantify the change in consumer sentiments over time. Commercialized tweets were topically categorized with key phrasal pattern matching. Results The overwhelming majority (80%) of tweets were classified as automated or promotional in nature. The majority of these tweets were coded as commercialized (83.65% in 2013), up to 33% of which offered discounts or free samples and appeared on over a billion twitter feeds as impressions. The positivity of Organic (human) classified tweets has decreased over time (5.84 in 2013 to 5.77 in 2014) due to a relative increase in the negative words ‘ban’, ‘tobacco’, ‘doesn’t’, ‘drug’, ‘against’, ‘poison’, ‘tax’ and a relative decrease in the positive words like ‘haha’, ‘good’, ‘cool’. Automated tweets are more positive than organic (6.17 versus 5.84) due to a relative increase in the marketing words like ‘best’, ‘win’, ‘buy’, ‘sale’, ‘health’, ‘discount’ and a relative decrease in negative words like ‘bad’, ‘hate’, ‘stupid’, ‘don’t’. Conclusions Due to the youth presence on Twitter and the clinical uncertainty of the long term health complications of electronic cigarette consumption, the protection of public health warrants scrutiny and potential regulation of social media

  15. Vapor phase heat transport systems

    NASA Astrophysics Data System (ADS)

    Hedstrom, J. C.; Neeper, D. A.

    1985-09-01

    Progress in theoretical and experimental investigations of various forms of a vapor transport system for solar space heating is described, which could also be applied to service water heating. The refrigerant is evaporated in a solar collector, which may be located on the external wall or roof of a building. The vapor is condensed in a passively discharged thermal storage unit located within the building. The condensed liquid can be returned to the collector either by a motor-driven pump or by a completely passive self-pumping mechanism in which the vapor pressure lifts the liquid from the condenser to the collector. The theoretical investigation analyzes this self-pumping scheme. Experiments in solar test cells compared the operation of both passive and active forms of the vapor system with the operation of a passive water wall. The vapor system operates as expected, with potential advantages over other passive systems in design flexibility and energy yield.

  16. 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.

  17. 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.

  18. 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.

  19. Carbonyl Compounds in Electronic Cigarette Vapors: Effects of Nicotine Solvent and Battery Output Voltage

    PubMed Central

    Kosmider, Leon; Sobczak, Andrzej; Fik, Maciej; Knysak, Jakub; Zaciera, Marzena; Kurek, Jolanta

    2014-01-01

    Introduction: Glycerin (VG) and propylene glycol (PG) are the most common nicotine solvents used in e-cigarettes (ECs). It has been shown that at high temperatures both VG and PG undergo decomposition to low molecular carbonyl compounds, including the carcinogens formaldehyde and acetaldehyde. The aim of this study was to evaluate how various product characteristics, including nicotine solvent and battery output voltage, affect the levels of carbonyls in EC vapor. Methods: Twelve carbonyl compounds were measured in vapors from 10 commercially available nicotine solutions and from 3 control solutions composed of pure glycerin, pure propylene glycol, or a mixture of both solvents (50:50). EC battery output voltage was gradually modified from 3.2 to 4.8V. Carbonyl compounds were determined using the HPLC/DAD method. Results: Formaldehyde and acetaldehyde were found in 8 of 13 samples. The amounts of formaldehyde and acetaldehyde in vapors from lower voltage EC were on average 13- and 807-fold lower than in tobacco smoke, respectively. The highest levels of carbonyls were observed in vapors generated from PG-based solutions. Increasing voltage from 3.2 to 4.8V resulted in a 4 to more than 200 times increase in formaldehyde, acetaldehyde, and acetone levels. The levels of formaldehyde in vapors from high-voltage device were in the range of levels reported in tobacco smoke. Conclusions: Vapors from EC contain toxic and carcinogenic carbonyl compounds. Both solvent and battery output voltage significantly affect levels of carbonyl compounds in EC vapors. High-voltage EC may expose users to high levels of carbonyl compounds. PMID:24832759

  20. Application of Thioether for Vapor Phase Lubrication

    NASA Technical Reports Server (NTRS)

    Graham, E. Earl

    1997-01-01

    The objective of these studies was to identify the optimal conditions for vapor phase lubrication using Thioether for both sliding and rolling wear. The important variable include; (1) The component materials including M50 steel, monel and silicon nitride. (2) The vapor concentration and flow rate. (3) The temperature in the range of 600 F to 1500 F. (4) The loads and rolling and/or sliding speeds.

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

    PubMed Central

    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

    2015-01-01

    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

  2. Up in Vapor: Exploring the Health Messages of E-Cigarette Advertisements.

    PubMed

    Willis, Erin; Haught, Matthew J; Morris Ii, David L

    2017-03-01

    Electronic cigarettes (e-cigarettes) have gained popularity in the United States, and marketers are using advertising to recruit new users to their products. Despite outright bans on traditional cigarette advertisements, e-cigarettes have no specific regulations. This study uses framing theory to explore the themes in e-cigarette advertisements. Also, practical implications are discussed.

  3. Phase-field crystal model with a vapor phase

    NASA Astrophysics Data System (ADS)

    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.

  4. 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.

  5. 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.

  6. Inhaled delivery of Δ(9)-tetrahydrocannabinol (THC) to rats by e-cigarette vapor technology.

    PubMed

    Nguyen, Jacques D; Aarde, Shawn M; Vandewater, Sophia A; Grant, Yanabel; Stouffer, David G; Parsons, Loren H; Cole, Maury; Taffe, Michael A

    2016-10-01

    Most human Δ(9)-tetrahydrocannabinol (THC) use is via inhalation, and yet few animal studies of inhalation exposure are available. Popularization of non-combusted methods for the inhalation of psychoactive drugs (Volcano(®), e-cigarettes) further stimulates a need for rodent models of this route of administration. This study was designed to develop and validate a rodent chamber suitable for controlled exposure to vaporized THC in a propylene glycol vehicle, using an e-cigarette delivery system adapted to standard size, sealed rat housing chambers. The in vivo efficacy of inhaled THC was validated using radiotelemetry to assess body temperature and locomotor responses, a tail-flick assay for nociception and plasma analysis to verify exposure levels. Hypothermic responses to inhaled THC in male rats depended on the duration of exposure and the concentration of THC in the vehicle. The temperature nadir was reached after ∼40 min of exposure, was of comparable magnitude (∼3 °Celsius) to that produced by 20 mg/kg THC, i.p. and resolved within 3 h (compared with a 6 h time course following i.p. THC). Female rats were more sensitive to hypothermic effects of 30 min of lower-dose THC inhalation. Male rat tail-flick latency was increased by THC vapor inhalation; this effect was blocked by SR141716 pretreatment. The plasma THC concentration after 30 min of inhalation was similar to that produced by 10 mg/kg THC i.p. This approach is flexible, robust and effective for use in laboratory rats and will be of increasing utility as users continue to adopt "vaping" for the administration of cannabis.

  7. 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.

  8. Vapor-phase heat-transport system

    NASA Astrophysics Data System (ADS)

    Hedstrom, J. C.

    1983-11-01

    A vapor-phase heat-transport system is being tested in one of the passive test cells at Los Alamos. The system consists of one selective-surface collector and a condenser inside a water storage tank. The refrigerant, R-11, can be returned to the collector by gravity or with a pump. Results from several operating configurations are presented, together with a comparison with other passive systems. A new self-pumping concept is presented.

  9. Vapor-phase heat-transport system

    NASA Astrophysics Data System (ADS)

    Hedstrom, J. C.

    A vapor-phase heat-transport system is being tested in one of the passive test cells at Los Alamos. The system consists of one selective-surface collector and a condenser inside a water storage tank. The refrigerant, R-11, can be returned to the collector by gravity or with a pump. Results from several operating configurations are presented, together with a comparison with other passive systems. A new self-pumping concept is presented.

  10. US Adults’ Perceptions of the Harmful Effects During Pregnancy of Using Electronic Vapor Products Versus Smoking Cigarettes, Styles Survey, 2015

    PubMed Central

    Tong, Van T.; Marynak, Kristy L.; King, Brian A.

    2016-01-01

    Introduction Research suggests aerosol from electronic vapor products (EVPs) has fewer harmful constituents than conventional cigarette smoke. Even so, EVPs and other nicotine-containing products are not safe to use during pregnancy. We examined perceptions among US adults regarding harm in using EVPs rather than smoking cigarettes during pregnancy. Methods Data came from the 2015 Styles Survey, an Internet panel survey of a sample of US adults aged 18 years or older (N = 4,127). Perceived harm was assessed by asking respondents whether using EVPs was less, equally, or more harmful for pregnant women than smoking cigarettes. Descriptive statistics were used to estimate perceived harm overall and by sociodemographic characteristics and tobacco-use status. Perceived harm was assessed among all adults, women of reproductive age (18–44 years, n = 820), and women of nonreproductive age (≥45 years, n = 1,398). Results Among all adults, 11.1% believed using EVPs during pregnancy was less harmful than smoking conventional cigarettes, 51.0% believed it was equally harmful, 11.6% believed it was more harmful, and 26.2% did not know. Prevalence of perception of less harm, by demographic category, was greatest among adults aged 18 to 24 years, men, non-Hispanic whites, adults with less than a high school diploma, current EVP users, and current cigarette smokers (P < .05). Prevalence of perception of less harm was greater among women of reproductive age (9.6%) than among those of nonreproductive age (7.9%) (P < .05). Conclusion US adults have varying levels of perceptions about the harms of EVP use versus cigarette smoking during pregnancy. Efforts are warranted to prevent nicotine exposure during pregnancy and to educate adults on the dangers of using any form of tobacco during pregnancy, including EVPs. PMID:28005528

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

    PubMed

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

    2012-01-02

    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

  12. Power production with two-phase expansion through vapor dome

    SciTech Connect

    Amend, W.E.; Toner, S.J.

    1984-08-07

    In a system wherein a fluid exhibits a regressive vapor dome in a T-S diagram, the following are provided: a two-phase nozzle receiving the fluid in pressurized and heated liquid state and expanding the received liquid into saturated or superheated vapor state, and apparatus receiving the saturated or superheated vapor to convert the kinetic energy thereof into power.

  13. 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.

  14. 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.

  15. 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.

  16. Smoke and Vapor: Exploring the Terminology Landscape among Electronic Cigarette Users

    PubMed Central

    Alexander, Jennifer P.; Coleman, Blair N.; Johnson, Sarah E.; Tessman, Greta K.; Tworek, Cindy; Dickinson, Denise M.

    2016-01-01

    Objective We explored the terminology of adult e-cigarette users in describing e-cigarette products and their use. We report how users discuss and differentiate these products and the language and culture surrounding them. Methods Focus groups (N = 12) were held in 5 locations in the United States between March and May, 2014. Participants (N = 99) included young adults or adults who were either exclusive or nonexclusive e-cigarette users. We gathered data on how users identify various types of e-cigarettes and how users understand and describe specific terms. Results Participants were familiar with the attributes of e-cigarettes in general but confused by the variety of products and unable to describe differences between product types. They were familiar with the term “vaping” even when they used “smoking” more frequently, and were clear that e-cigarettes do not produce traditional cigarette smoke. They had varied opinions about what to call regular users of e-cigarettes. Conclusions Findings highlight that conceptual clarity, including using specific and familiar terminology and product descriptions for users and nonusers alike, is challenging and crucial. It is important that surveillance efforts, policy development, messaging, and future research reflect the language understood and used by consumers to enable widespread comprehension. PMID:27430008

  17. A simple and rapid method for standard preparation of gas phase extract of cigarette smoke.

    PubMed

    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.

  18. Porous polymers by controlling phase separation during vapor deposition polymerization.

    PubMed

    Tao, Ran; Anthamatten, Mitchell

    2013-11-01

    A template-free method is described to fabricate continuous-phase, porous polymer films by simultaneous phase separation during vapor deposition polymerization. The technique involves concurrent polymerization, crosslinking, and phase separation of condensed species and reaction products. Deposited films form open-cell, macroporous structures consisting of crosslinked and glassy poly(glycidyl methacrylate). By limiting phase separation during vapor phase deposition, spatially dependent morphologies, such as layered morphologies, can be grown. Results show that combining vapor deposition polymerization with phase separation establishes morphological control, which may be applied to applications including cellular scaffolds, thin cushions and vibration dampers, and membranes for separations.

  19. Vapor-Phase Infrared Absorptivity Coefficient of HN1

    DTIC Science & Technology

    2013-08-01

    infrared spectrometer GC gas chromatography HD sulfur mustard HeNe helium–neon (laser) HgCdTe mercury–cadmium–telluride detector HN1, HN2, HN3...coefficient of the compound. 15. SUBJECT TERMS Vapor phase Saturator cell Infrared (IR) HN1 Vapor pressure Nitrogen mustard Vesicant...9 1 VAPOR-PHASE INFRARED ABSORPTIVITY COEFFICIENT OF HN1 1. INTRODUCTION The nitrogen mustards (HN1, HN2, and HN3) are similar to

  20. 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 π*←n absorption bands have been performed at vibronic resolution. The disparate nature of gas-phase and condensed-phase optical activity will be highlighted, with complementary ab initio calculations serving to elucidate the structural, chemical, and electronic origins of observed behavior. T. Müller, K. B. Wiberg, P. H. Vaccaro, J. R. Cheeseman, and M. J. Frisch, J. Opt. Soc. Am. B 19, 125 (2002) P. H. Vaccaro, ``Chapter 1.II.10: Optical Rotation and Intrinsic Optical Activity'' in Comprehensive Chiroptical Spectroscopy, N. Berova, P. L. Polavarapu, K. Nakanishi, and R. W. Woody, eds. (John Wiley and Sons, Inc

  1. 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.

  2. New Vapor/Mist Phase Lubricant Formulated

    NASA Technical Reports Server (NTRS)

    Morales, Wilfredo; Handschuh, Robert F.

    1999-01-01

    To meet the increased thermal stresses of future advanced aircraft engines, new lubricants will have to be developed to replace the currently used ester-based liquid lubricants. If a suitable conventional replacement cannot be found, a different lubrication method will have to be used. The conventional method circulates bulk lubricant (stored in a sump) through a lubricating system containing cooling and filtering elements. Solid lubricants have been studied as a replacement for bulk liquid lubricants, and have been found to provide reasonable lubrication for lightly loaded systems. Solid lubricants, however, have proved inadequate for highly loaded, high-speed applications. Vapor/mist phase lubrication (VMPL), on the other hand, may be a viable alternative. VMPL has been used successfully to lubricate high-temperature bearings or gears. It can be used as an emergency backup system or as the primary source of lubrication. With VMPL, minimal weight is added to the system and minimal debris is formed. It works over a wide temperature range.

  3. 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.

  4. Thermodynamic considerations of the vapor phase reactions in III–nitride metal organic vapor phase epitaxy

    NASA Astrophysics Data System (ADS)

    Sekiguchi, Kazuki; Shirakawa, Hiroki; Chokawa, Kenta; Araidai, Masaaki; Kangawa, Yoshihiro; Kakimoto, Koichi; Shiraishi, Kenji

    2017-04-01

    We analyzed the metal organic vapor phase epitaxial growth mechanism of the III–nitride semiconductors GaN, AlN, and InN by first-principles calculations and thermodynamic analyses. In these analyses, we investigated the decomposition processes of the group III source gases X(CH3)3 (X = Ga, Al, In) at finite temperatures and determined whether the (CH3)2GaNH2 adduct can be formed or not. The results of our calculations show that the (CH3)2GaNH2 adduct cannot be formed in the gas phase in GaN metal organic vapor phase epitaxy (MOVPE), whereas, in AlN MOVPE, the formation of the (CH3)2AlNH2 adduct in the gas phase is exclusive. In the case of GaN MOVPE, trimethylgallium (TMG, [Ga(CH3)3]) decomposition into Ga gas on the growth surface with the assistance of H2 carrier gas, instead of the formation of the (CH3)2GaNH2 adduct, occurs almost exclusively. Moreover, in the case of InN MOVPE, the formation of the (CH3)2InNH2 adduct does not occur and it is relatively easy to produce In gas even without H2 in the carrier gas.

  5. 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.

  6. 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...

  7. 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.

  8. 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.

  9. Hydride vapor phase epitaxy of aluminum nitride

    NASA Astrophysics Data System (ADS)

    Kamber, Derrick Shane

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

  10. 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.

  11. Vapor Phase Deposition Using Plasma Spray-PVD™

    NASA Astrophysics Data System (ADS)

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

    2010-01-01

    Plasma spray—physical 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 spray—chemical vapor deposition (PS-CVD) and plasma spray—thin 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.

  12. Toxicity of vapor phase petroleum contaminants to microbial degrader communities

    SciTech Connect

    Long, S.C.; Davey, C.A.

    1994-12-31

    Petroleum products constitute the largest quantity of synthetic organic chemical products produced in the US. They are comprised of mostly hydrocarbon constituents from many different chemical classes including alkenes, cycloalkanes, aromatic compounds, and polyaromatic hydrocarbons. Many petroleum constituents are classified as volatile organic compounds or VOCs. Petroleum products also constitute a major portion of environmental pollution. One emerging technology, with promise for applications to VOCs in subsurface soil environments, is bioventing coupled with soil vapor extraction. These technologies involve volatilization of contaminants into the soil gas phase by injection and withdrawal of air. This air movement causes enhancement of the aerobic microbial degradation of the mobilized vapors by the indigenous populations. This study investigated the effects of exposure of mixed, subsurface microbial communities to vapor phase petroleum constituents or vapors of petroleum mixtures. Soil slurries were prepared and plated onto mineral salts agar plates and exposed to vapor phase contaminants at equilibrium with pure product. Representative n-alkane, branched alkane, cycloalkane, and aromatic compounds were tested as well as petroleum product mixtures. Vapor exposure altered the numbers and morphologies of the colonies enumerated when compared to controls. However, even at high, equilibrium vapor concentrations, microbial degrader populations were not completely inhibited.

  13. A Standardized Method for the Preparation of a Gas Phase Extract of Cigarette Smoke.

    PubMed

    Higashi, Tsunehito; Mai, Yosuke; Mazaki, Yuichi; Horinouchi, Takahiro; Miwa, Soichi

    2016-01-01

    The gas phase of cigarette smoke is important from the viewpoint of human health, because it can pass through alveolar epithelium and enter the circulation. There is no standard method for the preparation of a gas phase extract of cigarette smoke (CSE), although CSE is widely used for research instead of whole cigarette smoke. We have established a standard method for the preparation of CSE. One cigarette per trial is continuously combusted under a reduced pressure generated by an aspiration pump with a velocity of 1.050 L/min: the main stream of the smoke is passed through a Cambridge filter to remove tar, and subsequently, bubbled through a glass ball filter (pore size, 20-30 µm) into 15 mL of phosphate-buffered saline (PBS). To express the concentration of CSE, a virtual tar concentration is introduced, which is calculated assuming that tar trapped on the Cambridge filter is dissolved in the PBS. CSEs prepared from smaller numbers of cigarettes (original virtual tar concentration≤15 mg/mL) show similar concentration-response curves for cytotoxicity versus virtual tar concentrations. CSEs prepared from various brands of cigarettes and by different smoking regimes (continuous and puff smoking) show similar cytotoxic potency if the virtual tar concentrations are the same. In conclusion, using the standardized method for CSE preparation in combination with the virtual tar concentration, it becomes possible to simply and rapidly prepare standard CSEs with defined concentrations from any brand of cigarettes, which are toxicologically equivalent to CSE prepared by puff smoking.

  14. Simultaneous analysis of 22 volatile organic compounds in cigarette smoke using gas sampling bags for high-throughput solid-phase microextraction.

    PubMed

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

    2014-07-15

    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 solid-phase microextraction gas chromatography-mass spectrometry (SPME-GC-MS). 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.

  15. 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.

  16. 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…

  17. 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).

  18. 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.

  19. Growth of manganese filled carbon nanofibers in the vapor phase

    NASA Astrophysics Data System (ADS)

    Ajayan, P. M.; Colliex, C.; Lambert, J. M.; Bernier, P.; Barbedette, L.; Tence, M.; Stephan, O.

    1994-03-01

    We report the vapor phase growth of partially filled graphitic fibers, 20-30 nm in diameter and up to a micron in length, during a manganese catalyzed carbon electric arc discharge. The fiber morphology resembles that of catalytic chemical vapor deposited carbon filaments but the inside hollow contains intermittent precipitates and continuous filling of Mn that at times occupy >50% of fiber lengths. Transmission electron microscopy and electron energy loss line spectra show that the fillings form as solid cores and may correspond to pure metal.

  20. Adiabatic nucleation in the liquid-vapor phase transition

    NASA Astrophysics Data System (ADS)

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

    2001-05-01

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

  1. Vapor-phase exchange of perchloroethene between soil and plants

    USGS Publications Warehouse

    Struckhoff, G.C.; Burken, J.G.; Schumacher, J.G.

    2005-01-01

    Tree core concentrations of tetrachloroethylene (perchloroethene, PCE) at the Riverfront Superfund Site in New Haven, MO, were found to mimic the profile of soil phase concentrations. The observed soil-tree core relationship was stronger than that of groundwater PCE to tree core concentrations at the same site. Earlier research has shown a direct, linear relationship between tree core and groundwater concentrations of chlorinated solvents and other organics. Laboratory-scale experiments were performed to elucidate this phenomenon, including determining partitioning coefficients of PCE between plant tissues and air and between plant tissues and water, measured to be 8.1 and 49 L/kg, respectively. The direct relationship of soil to tree core PCE concentrations was hypothesized to be caused by diffusion between tree roots and the soil vapor phase in the subsurface. The central findings of this research are discovering the importance of subsurface vapor-phase transfer for VOCs and uncovering a direct relationship between soil vapor-phase chlorinated solvents and uptake rates that impact contaminant translocation from the subsurface and transfer into the atmosphere. ?? 2005 American Chemical Society.

  2. 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

  3. High resolution absorption spectrum of dianilino in the vapor phase.

    PubMed

    Bayrakçeken, Fuat

    2009-01-01

    Photophysical and photochemical properties of diradical in the first excited state is recorded for the very first time with the IR, band structure for dianilino molecule at room temperature, in the vapor phase. In this experiment high resolution absorption spectra of anilino free radical, dianilino, aniline in the vapor phase and silicon dioxide in the solid state were recorded by flash photolysis technique photographically. Silicon dioxide absorption band between 250 and 255 nm were also observed for the reaction cell, because the cell and windows of the cell material were spectrosilica grade fused quartz. And this absorption band also used as wavelength calibration for all the photoproducts formed in the reaction cell during optical pumping.

  4. 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.

  5. nanocrystallites condensed in vapor-phase for photocatalyst applications

    NASA Astrophysics Data System (ADS)

    Yoshida, Takehito; Yagi, Nobuyasu; Nakagou, Riki; Sugimura, Akira; Umezu, Ikurou

    2014-10-01

    We have synthesized titanium dioxide (TiO2) nanocrystallites by pulsed laser ablation (PLA) in oxygen (O2) background gas for photocatalyst applications. Varying O2 background gas pressure or substrate target distance ( D TS), it was possible to change weight fraction of anatase phase in the anatase/rutile mixture from 0.2 to 1.0. Porosity of the deposited TiO2 films increased with increasing and D TS. Relation between the process parameters and the formed crystal phases was explained from the point of cooling process in vapor-phase. Furthermore, rapid thermal annealing (RTA) was performed as post-annealing, suppressing sintering of the nanocrystallites. Photocatalytic activities of the TiO2 nanocrystallites depended on the RTA temperature and following crystallinity restoring as well as the crystal phase: anatase or rutile.

  6. Knowledge about Chemicals in e-Cigarette Secondhand Vapor and Perceived Harms of Exposure among a National Sample of U.S. Adults.

    PubMed

    Tan, Andy S L; Mello, Susan; Sanders-Jackson, Ashley; Bigman, Cabral A

    2016-09-05

    Potentially harmful chemicals are detectable in e-cigarette secondhand vapor (hereafter SHV), contrary to advertising and marketing claims that it contains "only water vapor." We assessed public knowledge about the presence of chemicals in SHV and associations between knowledge and perceived harms of exposure to SHV. We conducted an online survey of a nationally representative sample of 1,449 U.S. adults (GfK's KnowledgePanel) from October to December 2013. Respondents were asked whether e-cigarette vapor contains only water vapor, contains tar, or contains formaldehyde (true/ false/ do not know). Responses to these three items were recoded (1 = incorrect, 2 = do not know, and 3 = correct) and averaged into a knowledge scale. They were also asked if they perceived breathing SHV to be harmful to one's health (two-item scale) and comparative harm of breathing SHV versus breathing secondhand smoke (SHS). Multiple regression analyses were weighted to the U.S. adult population and adjusted for potential confounders. Most respondents (58-75%) reported not knowing whether SHV contained only water vapor, if SHV contained tar, and if it contained formaldehyde. African-American respondents (vs. white) and current smokers (vs. nonsmokers) had lower levels of knowledge about chemicals in SHV. Adjusting for covariates, correct knowledge about chemicals in SHV was associated with higher perceived harms about SHV for one's health and perceived comparative harm of SHV versus SHS. These findings suggest a need to provide accurate information about the presence of chemicals in SHV (e.g., using product ingredient labels or public education).

  7. 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.

  8. Effect of charcoal-containing cigarette filters on gas phase volatile organic compounds in mainstream cigarette smoke.

    PubMed

    Polzin, G M; Zhang, L; Hearn, B A; Tavakoli, A D; Vaughan, C; Ding, Y S; Ashley, D L; Watson, C H

    2008-09-01

    Of the chemicals identified to date in mainstream cigarette smoke with known toxicological properties, the volatile organic compounds (VOCs) are considered the most hazardous group owing to their high abundance and toxicity. In this research we evaluate a recently introduced line of cigarettes that contain charcoal in their filters. The amount of charcoal in these filters ranged from 45 mg to 180 mg and were either dispersed among the filter material or contained in a small cavity in the filter segment. Charcoal has long been used for removing VOCs from both water and air. Our findings indicate that these cigarettes reduce machine generated mainstream smoke deliveries of a wide range of VOCs compared to a similar, non-charcoal filtered, cigarette. However, this reduction is dependent not only on the amount of charcoal present but also on the volume of smoke being drawn through the filter. While a brand with 45 mg charcoal reduces VOC delivery under ISO smoking conditions, charcoal saturation and breakthrough occur under more intense smoking conditions. Breakthrough is minimised for brands with the most charcoal. Overall, the brands with the most charcoal are effective at reducing VOC deliveries under even intense smoking conditions.

  9. 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.

  10. 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.

  11. Mechanism of phase transition, from vapor to solid: Transient liquid phase is between the two

    NASA Astrophysics Data System (ADS)

    Mahapatra, A. K.; Wang, Junyong; Zhang, Hongwei; Han, Min

    2016-08-01

    The mechanism of phase transition, from vapor to solid, is studied by producing non-stoichiometric ZnO and CdS nanoclusters (NCs) by low-energy cluster beam deposition technique, and examining their morphological and compositional evolution over a long span of time. It is concluded that the transition of vapor to solid goes through a transient liquid phase: coagulation of a large number of atomic clusters first forms liquid NCs which then solidify. The nature of the material and the experimental conditions determine crystallinity and shape of the NCs during the solidification process.

  12. 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.

  13. 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 ...

  14. Solvent Chemistry in the Electronic Cigarette Reaction Vessel

    PubMed Central

    Jensen, R. Paul; Strongin, Robert M.; Peyton, David H.

    2017-01-01

    Knowledge of the mechanism of formation, levels and toxicological profiles of the chemical products in the aerosols (i.e., vapor plus particulate phases) of e-cigarettes is needed in order to better inform basic research as well as the general public, regulators, and industry. To date, studies of e-cigarette emissions have mainly focused on chromatographic techniques for quantifying and comparing the levels of selected e-cigarette aerosol components to those found in traditional cigarettes. E-cigarettes heat and aerosolize the solvents propylene glycol (PG) and glycerol (GLY), thereby affording unique product profiles as compared to traditional cigarettes. The chemical literature strongly suggests that there should be more compounds produced by PG and GLY than have been reported in e-cigarette aerosols to date. Herein we report an extensive investigation of the products derived from vaporizing PG and GLY under mild, single puff conditions. This has led to the discovery of several new compounds produced under vaping conditions. Prior reports on e-cigarette toxin production have emphasized temperature as the primary variable in solvent degradation. In the current study, the molecular pathways leading to enhanced PG/GLY reactivity are described, along with the most impactful chemical conditions promoting byproduct production. PMID:28195231

  15. Solvent Chemistry in the Electronic Cigarette Reaction Vessel

    NASA Astrophysics Data System (ADS)

    Jensen, R. Paul; Strongin, Robert M.; Peyton, David H.

    2017-02-01

    Knowledge of the mechanism of formation, levels and toxicological profiles of the chemical products in the aerosols (i.e., vapor plus particulate phases) of e-cigarettes is needed in order to better inform basic research as well as the general public, regulators, and industry. To date, studies of e-cigarette emissions have mainly focused on chromatographic techniques for quantifying and comparing the levels of selected e-cigarette aerosol components to those found in traditional cigarettes. E-cigarettes heat and aerosolize the solvents propylene glycol (PG) and glycerol (GLY), thereby affording unique product profiles as compared to traditional cigarettes. The chemical literature strongly suggests that there should be more compounds produced by PG and GLY than have been reported in e-cigarette aerosols to date. Herein we report an extensive investigation of the products derived from vaporizing PG and GLY under mild, single puff conditions. This has led to the discovery of several new compounds produced under vaping conditions. Prior reports on e-cigarette toxin production have emphasized temperature as the primary variable in solvent degradation. In the current study, the molecular pathways leading to enhanced PG/GLY reactivity are described, along with the most impactful chemical conditions promoting byproduct production.

  16. Solvent Chemistry in the Electronic Cigarette Reaction Vessel.

    PubMed

    Jensen, R Paul; Strongin, Robert M; Peyton, David H

    2017-02-14

    Knowledge of the mechanism of formation, levels and toxicological profiles of the chemical products in the aerosols (i.e., vapor plus particulate phases) of e-cigarettes is needed in order to better inform basic research as well as the general public, regulators, and industry. To date, studies of e-cigarette emissions have mainly focused on chromatographic techniques for quantifying and comparing the levels of selected e-cigarette aerosol components to those found in traditional cigarettes. E-cigarettes heat and aerosolize the solvents propylene glycol (PG) and glycerol (GLY), thereby affording unique product profiles as compared to traditional cigarettes. The chemical literature strongly suggests that there should be more compounds produced by PG and GLY than have been reported in e-cigarette aerosols to date. Herein we report an extensive investigation of the products derived from vaporizing PG and GLY under mild, single puff conditions. This has led to the discovery of several new compounds produced under vaping conditions. Prior reports on e-cigarette toxin production have emphasized temperature as the primary variable in solvent degradation. In the current study, the molecular pathways leading to enhanced PG/GLY reactivity are described, along with the most impactful chemical conditions promoting byproduct production.

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

  18. Microscopic Modeling of Tribochemical Processes Vapor-Phase Lubrication and Nanotribology in MEMS

    DTIC Science & Technology

    2003-05-01

    INJECTORS, NAVIER STOKES EQUATIONS , JET FLOW, ADHESIVES, FLUID FLOW, LIQUID JETS, MOLECULAR DYNAMICS....VAPOR PHASES, *LUBRICATION, *TRIBOLOGY, * NANOTECHNOLOGY , *MICROELECTROMECHANICAL SYSTEMS, SURFACE ROUGHNESS, ELECTROMECHANICAL DEVICES, NOZZLES

  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 Beer’s law, which allows for a rigorous calculation of uncertainty in the absorption coefficients. As part of an ongoing collaboration with the National Institute of Standards and Technology (NIST), cross-laboratory validation is a critical aspect of this work. In order to identify possible errors in the Dugway flow-through system, quantitative spectra of isopropyl alcohol from both NIST and Pacific Northwest National Laboratory (PNNL) are compared to similar data taken at Dugway proving Grounds (DPG).

  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. 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.

  3. 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.

  4. 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.

  5. 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.

  6. 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

  7. Reversible solvent vapor-mediated phase changes in nanocrystal superlattices.

    PubMed

    Goodfellow, Brian W; Korgel, Brian A

    2011-04-26

    Colloidal nanocrystals are being explored for use in a variety of applications, from solar cells to transistors to medical diagnostics and therapy. Ordered assemblies of nanocrystals, or superlattices, are one particularly interesting class of these materials, in which the nanocrystals serve as modular building blocks to construct nanostructures by self-assembly with spatial and temporal complexity and unique properties. From a fundamental perspective, the nanocrystals are simple molecular models that can be manipulated and studied to test statistical mechanical and thermodynamic models of crystallization and disorder. An article by Bian et al. in this issue of ACS Nano reports surprising new phase behavior in semiconductor nanocrystal superlattices: reversible transitions between non-close-packed body-centered cubic (bcc) and body-centered tetragonal (bct) structures, and close-packed face-centered cubic (fcc) structures, observed by real-time in situ grazing incidence small-angle X-ray scattering (GISAXS) measurements, upon solvent vapor exposure and increased interparticle separation. These studies offer new insight and raise new questions about superlattice structure and the forces that control self-assembly. Accompanying computer simulations show that ligand-ligand interactions are important. Furthermore, it appears that ligand-coated nanocrystals have more in common with soft microphase-separated materials, like diblock copolymers and surfactant assemblies, than previously realized.

  8. 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

    2015-01-02

    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.

  9. Using Vapor Phase Tomography to Measure the Spatial Distribution of Vapor Concentrations and Flux for Vadose-zone VOC Sources

    PubMed Central

    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 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 combined with 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

  10. Importance of extracting solvent vapor pressure in headspace liquid-phase microextraction.

    PubMed

    Yan, Xue; Yang, Cui; Ren, Chunyan; Li, Donghao

    2008-09-26

    Of the many parameters that affect the enrichment factors in headspace liquid-phase microextraction, in this study, we systematically investigated the influence of the vapor pressure of the extracting solvent. Seven extracting solvents with different vapor pressures were selected and tested. It was found that the vapor pressure of the extracting solvent dramatically affects the enrichment factor and the factor was increasing by decreasing the extracting solvent vapor pressure under given experimental conditions. The result was validated for volatile organic compounds such as polynuclear aromatic hydrocarbons, organochlorine pesticides and polychlorinated biphenyls.

  11. Metal-Organic Vapor Phase Epitaxial Reactor for the Deposition of Infrared Detector Materials

    DTIC Science & Technology

    2015-04-09

    2010 14-Mar-2013 Approved for Public Release; Distribution Unlimited Final Report: Metalorganic Vapor Phase Epitaxial Reactor for the Deposition of...ADDRESS (ES) U.S. Army Research Office P.O. Box 12211 Research Triangle Park, NC 27709-2211 Epitaxial reactor , MOCVD, Infrared Materials, CdTe and...Final Report: Metalorganic Vapor Phase Epitaxial Reactor for the Deposition of Infrared Detector Materials Report Title A fully automated

  12. A Level Set Method for vaporizing two-phase flows

    NASA Astrophysics Data System (ADS)

    Tanguy, Sébastien; Ménard, Thibaut; Berlemont, Alain

    2007-02-01

    Development and applications of numerical methods devoted to reactive interface simulations are presented. Emphasis is put on vaporization, where numerical difficulties arise in imposing accurate jump conditions for heat and mass transfers. We use both the Level Set Method and the Ghost Fluid Method to capture the interface motion accurately and to handle suitable jump conditions. A local vaporization mass flow rate per unit of surface area is defined and Stefan flow is involved in the process. Specific care has been devoted to the extension of discontinuous variables across the interface to populate ghost cells, in order to avoid parasitic currents and numerical diffusion across the interface. A projection method is set up to impose both the velocity field continuity and a divergence-free condition for the extended velocity field across the interface. The d2 law is verified in the numerical simulations of the vaporization of an isolated static drop. Results are then presented for a water droplet moving in air. Vapor mass fraction and temperature fields inside and outside the droplet are presented.

  13. 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...

  14. 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…

  15. E-cigarettes: promise or peril?

    PubMed

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

    2012-03-01

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

  16. Microwave-assisted fast vapor-phase transport synthesis of MnAPO-5 molecular sieves

    SciTech Connect

    Shao Hui; Yao Jianfeng; Ke Xuebin; Zhang Lixiong Xu Nanping

    2009-04-02

    MnAPO-5 was prepared by a microwave-assisted vapor-phase transport method at 180 deg. C in short times. The products were characterized by X-ray diffraction, scanning electron microscopy, Fourier transform infrared spectra, UV-vis spectroscopic measurement, NH{sub 3}-temperature-programmed desorption and esterification reaction. It was found that dry gels prepared with aluminum isopropoxide, phosphoric acid and manganese acetate could be transferred to MnAPO-5 in the vapors of triethylamine and water by the microwave-assisted vapor-phase transport method at 180 deg. C for less than 30 min. The crystallization time was greatly reduced by the microwave heating compared with the conventional heating. The resulting MnAPO-5 exhibited much smaller particle sizes, higher surface areas and slightly higher catalytic activity in the esterification of acetic acid and butyl alcohol than those prepared by the conventional vapor-phase transport method and hydrothermal synthesis.

  17. REDOX AND ELECTROPHILIC PROPERTIES OF VAPOR- AND PARTICLE-PHASE COMPONENTS OF AMBIENT AEROSOLS

    PubMed Central

    Eiguren-Fernandez, Arantzazu; Shinyashiki, Masaru; Schmitz, Debra A.; DiStefano, Emma; Hinds, William; Kumagai, Yoshito; Cho, Arthur K.; Froines, John R.

    2010-01-01

    Particulate matter (PM) has been the primary focus of studies aiming to understand the relationship between the chemical properties of ambient aerosols and adverse health effects. Size and chemical composition of PM have been linked to their oxidative capacity which has been postulated to promote or exacerbate pulmonary and cardiovascular diseases. But in the last few years, new studies have suggested that volatile and semivolatile components may also contribute to many adverse health effects. The objectives of this study were: i) assess for the first time the redox and electrophilic potential of vapor-phase components of ambient aerosols, and ii) evaluate the relative contributions of particle- and vapor-fractions to the hazard of a given aerosol. To achieve these objectives vapor- and particle-phase samples collected in Riverside (CA) were subjected to three chemical assays to determine their redox and electrophilic capacities. The results indicate that redox active components are mainly associated with the particle-phase, while electrophilic compounds are found primarily in the vapor-phase. Vapor-phase organic extracts were also capable of inducing the stress responding protein, heme-oxygenase-1 (HO-1), in RAW264.7 murine macrophages. These results demonstrate the importance of volatile components in the overall oxidative and electrophilic capacity of aerosols, and point out the need for inclusion of vapors in future health and risk assessment studies. PMID:20152964

  18. 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.

  19. 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.

  20. 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.

  1. Ultrafast dynamics of the acoustic vaporization of phase-change microdroplets.

    PubMed

    Shpak, Oleksandr; Kokhuis, Tom J A; Luan, Ying; Lohse, Detlef; de Jong, Nico; Fowlkes, Brian; Fabiilli, Mario; Versluis, Michel

    2013-08-01

    Acoustically sensitive emulsions are a promising tool for medical applications such as localized drug delivery. The physical mechanisms underlying the ultrasound-triggered nucleation and subsequent vaporization of these phase-change emulsions are largely unexplored. Here, the acoustic vaporization of individual micron-sized perfluoropentane (PFP) droplets is studied at a nanoseconds timescale. Highly diluted emulsions of PFP-in-water and oil-in-PFP-in-water droplets, ranging from 3.5 to 11 μm in radius, were prepared and the nucleation and growth of the vapor bubbles was imaged at frame rates of up to 20 Mfps. The droplet vaporization dynamics was observed to have three distinct regimes: (1) prior to nucleation, a regime of droplet deformation and oscillatory translations within the surrounding fluid along the propagation direction of the applied ultrasound; (2) a regime characterized by the rapid growth of a vapor bubble enhanced by ultrasound-driven rectified heat transfer; and (3) a final phase characterized by a relatively slow expansion, after ultrasound stops, that is fully dominated by heat transfer. A method to measure the moment of inception of the nucleation event with respect to the phase of the ultrasound wave is proposed. A simple physical model captures quantitatively all of the features of the subsequent vapor bubble growth.

  2. 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.

  3. 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

  4. Evaluation of Preservative Engine Oil Containing Vapor-Phase Corrosion Inhibitor and a Simplified Engine Preservation Technique

    DTIC Science & Technology

    1990-12-01

    AD-A240 100 EVALUATIONS OF PRESERVATIVE ENGINE OIL CONTAINING VAPOR-PHASE CORROSION INHIBITOR AND A SIMPLIFIED ENGINE PRESERVATION TECHNIQUE INTERIM...22060-5606 62786 AH20 123 11. TITLE (Include Security Classtfication) Evaluations of Preservative Engine Oil Containing Vapor-Phase Corrosion Inhibitor...the feasibility of adding a vapor-phase corrosion inhibitor (VCI) component to improve the preservation performance of MIL-L-21260 and (2) to evaluate

  5. 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

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

    SciTech Connect

    Robertson, G.H.; Doyle, L.R.; Pavlath, A.E.

    1983-12-01

    Fermentation of ethanol in a system whereby the biomass is used intensively (both to separate alcohol from water by vapor phase adsorption and to serve as the feedstock) is shown to be possible on theoretical grounds when the biomass is grain. The rationale for a vapor-phase adsorption process as an alternative to distillation is shown to be energetically valid above 84 wt % ethanol. The capacity of grain in new vapor-phase ambient adsorption processes was estimated experimentally with the finding that sufficient capacity exists for the intensive use but that the adsorption is dynamically controlled so that the grain form and particle size are important. Pretreatments such as explosive dehydration improve the transfer of water to the grain in adsorption with potential improvement in the efficiency of liquefaction and saccharification. At room temperature, these sorbents are not perfectly selective for water but adsorb ethanol which will be carried to the liquefaction, saccharification, and fermentation with the feedstock.

  7. 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.

  8. Monitoring laboratory-scale bioventing using synchronous scan fluorescence spectroscopy: analysis of the vapor phase.

    PubMed

    Bachman, J; Kanan, S M; Patterson, H H

    2001-01-01

    Bioventing is an improved method of soil remediation that is being used with increasing frequency. In this paper, we refine techniques to measure the progress of petroleum hydrocarbon decomposition by monitoring vapor phase composition with synchronous scan fluorescence spectroscopy (SSFS). Analysis of the vapor phase has advantages compared to standard extraction techniques that require extensive sample handling and clean up. For comparison, hydrocarbon contamination in the soil was measured by analysis of Soxhlet extractions with gas chromatography-mass spectrometry (GC-MS). Comparison of the GC-MS and SSFS data showed that changes in hydrocarbon composition measured in the vapor phase provide an accurate measure of decomposition reactions taking place in the soil.

  9. 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.

  10. Vaporization Behavior, Phase Equilibria, and Thermodynamic Stabilities of Nickel Phosphides.

    DTIC Science & Technology

    1984-10-04

    ABSTRACT (Continue an revwee side if neceeear and Identlly by block number) The equilibrium vaporization reactions, 12 Ni2P(s) = 2 Ni12P5 (s) + P2(g...and 6.8 Ni12P5 (s) = 32 Ni2.55P(s) + P2(g), have been studied by mass-loss effusion in the temperature range 1237-1401 K. The results were combined with...of atomization, 0 ~/R, respectively, in kilokelvins at 298.15 K: 1/4 Ni P(s), -5.94±0.5, 54.8; 1/3.55 Ni2 5 P(s), -6.65±0.5, 55.2; 1/17 Ni12P5 ( -6.73

  11. Evaluation of the genotoxic and cytotoxic potential of mainstream whole smoke and smoke condensate from a cigarette containing a novel carbon filter.

    PubMed

    Bombick, D W; Bombick, B R; Ayres, P H; Putnam, K; Avalos, J; Borgerding, M F; Doolittle, D J

    1997-09-01

    A novel carbon filter has been developed which primarily reduces the amount of certain vapor phase constituents of tobacco smoke with greater efficiency than the charcoal filters of cigarettes currently in the market. In vitro indicators of genotoxic and cytotoxic potential were used to compare the cigarette smoke condensate (particulate phase) or whole cigarette smoke (vapor phase and particulate phase) from cigarettes containing the novel carbon filter with smoke condensate or whole smoke from commercial or prototype cigarettes not containing the novel carbon filter. Ames bacterial mutagenicity, sister chromatid exchange (SCE) in Chinese hamster ovary (CHO) cells, and neutral red cytotoxicity assays in CHO cells were utilized to assess the genotoxic and cytotoxic potential of the cigarette smoke condensates. SCE and neutral red cytotoxicity assays were utilized to assess the genotoxic and cytotoxic potential of the whole smoke. As expected, the novel carbon filter did not significantly affect the genotoxic or cytotoxic activity of the smoke condensate, although we did observe that the use of low-nitrogen tobacco reduced the mutagenicity of the condensate in Salmonella typhimurium strain TA98. However, the whole smoke from cigarettes containing the novel carbon filter demonstrated significant reductions in genotoxic and cytotoxic potential compared to cigarettes without the novel carbon filter. The toxicity of the smoke was correlated (r = 0.7662 for cytotoxicity and r = 0.7562 for SCE induction) to the aggregate mass of several vapor phase components (acetone, acetaldehyde, acrolein, acrylonitrile, 1,3-butadiene, ammonia, NOx, HCN, benzene, isoprene, and formaldehyde) in the smoke of the cigarettes utilized in this study. In conclusion, this novel carbon filter, which significantly reduced the amount of carbonyls and other volatiles in mainstream cigarette smoke, resulted in significant reductions in the genotoxic and cytotoxic activity of the smoke as measured

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

    SciTech Connect

    Dugger, Michael Thomas; 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.

  13. Vapor-phase toxicity of butylbenzyl phthalate to three plant species: white mustard, chinese cabbage, and white clover.

    PubMed

    Gorsuch, J W; Staples, C A; Brown, D; Enste-Diefenbach, R

    2008-08-01

    During the manufacture of products containing butylbenzyl phthalate (BBP), low emissions to the air may occur. Due to potential exposure of terrestrial communities to BBP vapors, phytotoxicity tests were conducted using Chinese cabbage, white mustard, and white clover. No significant effects on shoot growth were observed at the higher BBP vapor-phase concentration tested, which measured 5.7 microg/m(3). The overall practicality of vapor-phase testing of chemicals with very low vapor pressures is reviewed. These study results suggest that environmental risk from exposure to BBP vapor is negligible for plants.

  14. Irradiation of fish fillets: Relation of vapor phase reactions to storage quality

    USGS Publications Warehouse

    Spinelli, J.; Dollar, A.M.; Wedemeyer, G.A.; Gallagher, E.C.

    1969-01-01

    Fish fillets irradiated under air, nitrogen, oxygen, or carbon dioxide atmospheres developed rancidlike flavors when they were stored at refrigerated temperatures. Packing and irradiating under vacuum or helium prevented development of off-flavors during storage.Significant quantities of nitrate and oxidizing substances were formed when oxygen, nitrogen, or air were present in the vapor or liquid phases contained in a Pyrex glass model system exposed to ionizing radiation supplied by a 60Co source. It was demonstrated that the delayed flavor changes that occur in stored fish fillets result from the reaction of vapor phase radiolysis products and the fish tissue substrates.

  15. 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.

  16. Improved thermodynamic analysis of gas reactions for compound semiconductor growth by vapor-phase epitaxy

    NASA Astrophysics Data System (ADS)

    Inatomi, Yuya; Kangawa, Yoshihiro; Kakimoto, Koichi; Koukitu, Akinori

    2017-03-01

    An improved thermodynamic analysis method for vapor-phase epitaxy is proposed. In the conventional method, the mass-balance constraint equations are expressed in terms of variations in partial pressure. Although the conventional method is appropriate for gas–solid reactions occurring near the growth surface, it is not suitable for gas reactions that involve changes in the number of gas molecules. We reconsider the constraint equations in order to predict the effect of gas reactions on semiconductor growth processes. To demonstrate the feasibility of the improved method, the growth process of group-III nitrides by metalorganic vapor-phase epitaxy has been investigated.

  17. 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.

  18. 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.

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

    DOEpatents

    Geohegan, David B.; Seals, Roland D.; Puretzky, Alex A.; Fan, Xudong

    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.

  20. Are Published Minimum Vapor Phase Spark Ignition Energy Data Valid?

    SciTech Connect

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

    2001-11-21

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

  1. Relative sensitivities of plasma lecithin:cholesterol acyltransferase, platelet-activating factor acetylhydrolase, and paraoxonase to in vitro gas-phase cigarette smoke exposure.

    PubMed

    Bielicki, J K; Knoff, L J; Tribble, D L; Forte, T M

    2001-03-01

    In order to identify potential atherogenic properties of gas-phase cigarette smoke, we utilized an in vitro exposure model to determine whether the activities of several putative anti-atherogenic enzymes associated with plasma lipoproteins were compromised. Exposure of heparinized human plasma to gas-phase cigarette smoke produced a dose-dependent reduction in the activity of platelet-activating factor acetylhydrolase (PAF-AH). Reductions of nearly 50% in PAF-AH activity were observed following exposure to gas-phase smoke from four cigarettes over an 8-h period. During this time of exposure, lecithin:cholesterol acyltransferase (LCAT) was rendered almost completely inactive (>80%). In contrast, paraoxonase was totally unaffected by cigarette smoke. Supplementation of plasma with 1 mM reduced glutathione was found to protect both PAF-AH and LCAT from cigarette smoke, suggesting that cysteine modifications may have contributed to the inhibition of these two enzymes. To evaluate this possibility, we blocked the free cysteine residues of these enzymes with the reversible thiol-modifying reagent dithiobisnitrobenzoic acid (DTNB). Reversal of the DTNB-cysteine adducts following cigarette smoke exposures revealed that LCAT, but not PAF-AH, was protected. Moreover, high doses (1.0-10 mM) of acrolein and 4-hydroxynonenal, reactive aldehydic species associated with cigarette smoke, completely inhibited plasma LCAT activity, whereas PAF-AH was resistant to such exposures. Taken together, these results indicate a divergence regarding the underlying mechanism of PAF-AH and LCAT inhibition upon exposure to gas-phase cigarette smoke. While LCAT was sensitive to exposure to volatile aldehydic products involving, in part, cysteine and/or active site modifications, the enzyme PAF-AH exhibited an apparent resistance. The latter suggests that the active site of PAF-AH is in a microenvironment that lacks free cysteine residues and/or is shielded from volatile aldehydic combustion

  2. Effect of vapor-phase mass transfer on aquifer restoration

    SciTech Connect

    Miller, C.T.; Staes, E.G.

    1992-02-01

    Volatile organic chemicals (VOC) are a frequent source of groundwater contamination in North Carolina and throughout the United States and other developed countries. The work is considered a subset of the general multiphase flow and transport problem: fluid flow and contaminant transport in the gas phase of the unsaturated zone. The specific purpose of the work was to investigate gas-phase (VOC) transport phenomena at the field scale to assess the relative importance of operative transport phenomena. A field research site was established at an active fire training area on Pope Air Force Base. Monitoring of groundwater flow and gas-phase contaminant distributions was accomplished as a function of three spatial dimensions and time. These distributions are reported and interpreted with respect to the current level of understanding of gas-phase transport phenomena. Consideration is given to advective transport, diffusive transport, interphase mass transfer, and multicomponent effects. Numerical modeling is used to evaluate expected steady-state contaminant distributions in the unsaturated zone and to assess relative time scales of operative transport processes. Reasonable agreement is achieved between model simulations and observed concentration distributions in the field, with a dominant vertical transport component shown in both predicted and observed contaminant distributions.

  3. Could charcoal filtration of cigarette smoke reduce smoking-induced disease? A review of the literature.

    PubMed

    Coggins, Christopher R E; Gaworski, Charles L

    2008-04-01

    A review of the published work with charcoal-filtered cigarettes indicates that there are reductions in the concentrations for many gas-vapor phase constituents found in mainstream smoke. However, charcoal filters provided no apparent capacity for reduction of smoke particulate phase components. The reductions in gas-vapor phase smoke chemistry analytes generally correspond with findings of reduced toxicological activity, principally related to a reduction in the cytotoxic action of the volatile smoke constituents. Results of a short-term clinical study show small reductions in the biomarkers of the gas-vapor phase smoke constituents in subjects smoking charcoal-filtered cigarettes, compared to subjects smoking non-charcoal filtered cigarettes. The very limited epidemiology data (a single study) fail to demonstrate a conclusive beneficial effect of charcoal-filtered cigarette products compared to non-charcoal filtered cigarette products. Review of the scientific literature is hindered due to the lack of documentation regarding the activity of the charcoal used in the filter, and the inconsistency in product designs used between the various different disciplines (chemistry, pre-clinical, clinical and epidemiology) that have conducted studies with charcoal filtered cigarettes. There do not appear to be any published studies using a combination of data from the different disciplines based on a consistently designed charcoal cigarette filter. Although the literature presently available would suggest that smoke filtration provided by current charcoal filter techniques alone may not be substantial enough to reduce smoking-related disease, the data are limited. Therefore, for the reduction of smoking-induced disease, it is difficult to come to a definitive conclusion regarding the potential health benefits of using charcoal as a smoke filtration technology.

  4. Hybrid vapor phase-solution phase growth techniques for improved CZT(S,Se) photovoltaic device performance

    DOEpatents

    Chang, Liang-Yi; Gershon, Talia S.; Haight, Richard A.; Lee, Yun Seog

    2016-12-27

    A hybrid vapor phase-solution phase CZT(S,Se) growth technique is provided. In one aspect, a method of forming a kesterite absorber material on a substrate includes the steps of: depositing a layer of a first kesterite material on the substrate using a vapor phase deposition process, wherein the first kesterite material includes Cu, Zn, Sn, and at least one of S and Se; annealing the first kesterite material to crystallize the first kesterite material; and depositing a layer of a second kesterite material on a side of the first kesterite material opposite the substrate using a solution phase deposition process, wherein the second kesterite material includes Cu, Zn, Sn, and at least one of S and Se, wherein the first kesterite material and the second kesterite material form a multi-layer stack of the absorber material on the substrate. A photovoltaic device and method of formation thereof are also provided.

  5. 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...

  6. 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...

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

    PubMed

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

    2013-12-01

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

  8. EFFECT OF DIRECTIONAL SWITCHING FREQUENCY ON TOLUENE DEGRADATION IN A VAPOR-PHASE BIOREACTOR. (R826168)

    EPA Science Inventory

    A potential method to improve biomass distribution and the stability of vapor-phase bioreactors is to operate them in a directionally switching mode such that the contaminant air stream direction is periodically reversed through the reactor. In this study, the effect of switching...

  9. 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. ...

  10. 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.

  11. 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...

  12. 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...

  13. 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.

  14. Metalorganic Vapor Phase Epitaxial Growth of (211)B CdTe on Nanopatterned (211)Si

    DTIC Science & Technology

    2012-05-15

    SUBJECT TERMS CdTe Epitaxy, Molecular Transfer Lithography, Dislocation Reduction Shashidhar Shintri*,1, , Sunil Rao2, , Charles Schaper3, , Witold...2012) / DOI 10.1002/pssc.201100653 Metalorganic vapor phase epitaxial growth of (211)B CdTe on nanopatterned (211)Si Shashidhar Shintri*,1, Sunil

  15. Scavenging of free radicals in gas-phase mainstream cigarette smoke by immobilized catalase at filter level.

    PubMed

    Lu, Xin; Hua, Zhaozhe; Du, Guocheng; Ma, Xiaolong; Cao, Jianhua; Yang, Zhanping; Chen, Jian

    2008-03-01

    Catalase is well known as capable of inducing the decomposition of H(2)O(2). In this study, a kind of immobilized catalase (entrapped in cross-linked chitosan beads) was dispersed in conventional acetate filter as an antioxidant additive. Quantitative estimation of the free radicals in mainstream cigarette smoke (MCS) was performed to address the effect of this modified filter. It was found that the levels of PBN adduct and NO(*)/NO(2)(*) associated with the gas-phase mainstream cigarette smoke (GPCS) were efficiently decreased by approximately 40% through catalase filtering. Besides, the modified filter was found to lower the MCS-induced adverse biological effects including lipid peroxidation and mutagenicity. This was proved to be substantially attributed to the catalase-dependent breakdown of NO(*), which was stimulated by some of peroxides (most probably being H(2)O(2)), the dismutation products of tar particulate matters (TPM). These results highlighted a promising approach to reduce the smoking-associated health risks to passive smokers. Moreover, the mechanisms of catalase filtering may be helpful for the development of appropriate immobilized enzyme systems to be applied for reducing health risks associated with gaseous pollutants.

  16. 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.

  17. 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

  18. Phase-transitional Fe3O4/perfluorohexane Microspheres for Magnetic Droplet Vaporization

    PubMed Central

    Wang, Ronghui; Zhou, Yang; Zhang, Ping; Chen, Yu; Gao, Wei; Xu, Jinshun; Chen, Hangrong; Cai, Xiaojun; Zhang, Kun; Li, Pan; Wang, Zhigang; Hu, Bing; Ying, Tao; Zheng, Yuanyi

    2017-01-01

    Activating droplets vaporization has become an attractive strategy for ultrasound imaging and physical therapy due to the significant increase in ultrasound backscatter signals and its ability to physically damage the tumor cells. However, the current two types of transitional droplets named after their activation methods have their respective limitations. To circumvent the limitations of these activation methods, here we report the concept of magnetic droplet vaporization (MDV) for stimuli-responsive cancer theranostics by a magnetic-responsive phase-transitional agent. This magnetic-sensitive phase-transitional agent—perfluorohexane (PFH)-loaded porous magnetic microspheres (PFH-PMMs), with high magnetic-thermal energy-transfer capability, could quickly respond to external alternating current (AC) magnetic fields to produce thermal energy and trigger the vaporization of the liquid PFH. We systematically demonstrated MDV both in vitro and in vivo. This novel trigger method with deep penetration can penetrate the air-filled viscera and trigger the vaporization of the phase-transitional agent without the need of pre-focusing lesion. This unique MDV strategy is expected to substantially broaden the biomedical applications of nanotechnology and promote the clinical treatment of tumors that are not responsive to chemical therapies. PMID:28382158

  19. 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.

  20. 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.

  1. Phase State and Saturation Vapor Pressure of Submicron Particles of meso-Erythritol at Ambient Conditions.

    PubMed

    Emanuelsson, Eva U; Tschiskale, Morten; Bilde, Merete

    2016-09-15

    meso-Erythritol is a sugar alcohol identified in atmospheric aerosol particles. In this work, evaporation of submicron-sized particles of meso-erythritol was studied in a TDMA system including a laminar flow tube under dry conditions at five temperatures (278-308 K) and ambient pressure. A complex behavior was observed and attributed to the formation of particles of three different phase states: (1) crystalline, (2) subcooled liquid or amorphous, and (3) mixed. With respect to saturation vapor pressure, the subcooled liquid and amorphous states are treated to be the same. The particle phase state was linked to initial particle size and flow tube temperature. Saturation vapor pressures of two phase states attributed to the crystalline and subcooled liquid state respectively are reported. Our results suggest a mass accommodation coefficient close to one for both states.

  2. 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.

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

    SciTech Connect

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

    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

  4. 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

  5. Development of a correlation for aqueous-vapor phase mass transfer in porous media

    NASA Astrophysics Data System (ADS)

    Szatkowski, Andrew; Imhoff, Paul T.; Miller, Cass T.

    1995-03-01

    In many situations vapor-phase extraction procedures (e.g., soil venting, air sparging, and bioventing) may be suitable methods for remediating porous media contaminated by volatile organic compounds. This has led to increased study of operative processes in these systems, including aqueous-vapor phase mass transfer. Past work has shown the importance of the flow regime on this process, but a quantitative estimate of mass-transfer coefficients is lacking, especially for systems not confounded by uncertainties involving interfacial area between the phases. An experimental investigation was conducted to isolate the resistance to aqueous-vapor phase mass transfer at the phase boundary, using an ideal porous medium system. Mass-transfer coefficients were measured for toluene for a wide range of Reynolds numbers. An empirical model was fit to the data in dimensionless form. The mass-transfer model was coupled with an available interfacial area model, yielding a dimensionless expression for the mass-transfer rate coefficient. This expression was used to compare results from this work to three other experimental studies reported in the literature. These comparisons showed that for experiments where infiltrating water flowed uniformly within the porous medium, the predicted mass-transfer coefficients were within a factor of 5 of the measured coefficients. Mass transfer was significantly slower than the rate predicted, using the results from this work, in experiments where infiltrating water flowed nonuniformly.

  6. Nucleation Chemical Physics: From Vapor Phase Clusters to Crystals in Solution

    SciTech Connect

    Kathmann, Shawn M.

    2007-08-03

    Both vapor-phase clusters and condensed-phase crystals are important in a wide variety of fundamental and applied problems in chemical physics. Favorable fluctuations in a supersaturated phase generate clusters of the new phase – exactly how one defines these new clusters as distinct from the mother phase represents a continuing challenge in molecular theories of nucleation. These incipient clusters can form homogeneously within the mother phase or heterogeneously on seeds, dust, impurities, ions, or others stability-inducing atomic/molecular structures (e.g., steps, edges, vacancies, etc.). Upon reaching a critical size the clusters may grow to macroscopic dimensions if enough nucleating material is present in surrounding environment or until relaxation processes dominate bringing the phase transformation to completion. This work was supported by the Chemical and Material Sciences Division, Office of Basic Energy Sciences, Department of Energy. The Pacific Northwest National Laboratory is operated by Battelle for the US Department of Energy.

  7. The Roles of Cigarette Smoking and the Lung in the Transitions Between Phases of Preclinical Rheumatoid Arthritis.

    PubMed

    Sparks, Jeffrey A; Karlson, Elizabeth W

    2016-03-01

    While the etiology of rheumatoid arthritis (RA) remains to be fully elucidated, recent research has advanced the understanding of RA pathogenesis to the point where clinical trials for RA prevention are underway. The current paradigm for RA pathogenesis is that individuals progress through distinct preclinical phases prior to the onset of clinically apparent RA. These preclinical RA phases consist of genetic risk, local inflammation, presence of RA-related autoantibodies, asymptomatic systemic inflammation, and early non-specific symptoms prior to clinical seropositive RA. Epidemiologic studies have been important in forming hypotheses related to the biology occurring in preclinical RA. Specifically, studies associating cigarette smoking with overall RA risk as well as transitions between phases of preclinical RA were vital in helping to establish the lung as a potential important initiating site in the pathogenesis of seropositive RA. Herein, we review the epidemiology associating smoking with transitions in preclinical phases of RA as well as the recent literature supporting the lung as a critical site in RA pathogenesis.

  8. 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.

  9. 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.

  10. 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; Jörres, 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 μg/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.

  11. Rapid determination of six carcinogenic primary aromatic amines in mainstream cigarette smoke by two-dimensional online solid phase extraction combined with liquid chromatography tandem mass spectrometry.

    PubMed

    Bie, Zhenying; Lu, Wei; Zhu, You; Chen, Yusong; Ren, Hubo; Ji, Lishun

    2017-01-27

    A fully automated, rapid, and reliable method for simultaneous determination of six carcinogenic primary aromatic amines (AAs), including o-toluidine (o-TOL), 2, 6-dimethylaniline (2, 6-DMA), o-anisidine (o-ASD), 1-naphthylamine (1-ANP), 2-naphthylamine (2-ANP), and 4-aminobiphenyl (4-ABP), in mainstream cigarette smoke was established. The proposed method was based on two-dimensional online solid phase extraction combined with liquid chromatography tandem mass spectrometry (SPE/LC-MS/MS). The particulate phase of the mainstream cigarette smoke was collected on a Cambridge filter pad and pretreated via ultrasonic extraction with 2% formic acid (FA), while the gas phase was trapped by 2% FA without pretreatment for determination. The two-dimensional online SPE comprised of two cartridges with different absorption characteristics was applied for sample pretreatment. Analysis was performed by liquid chromatography coupled with tandem mass spectrometry (LC-MS/MS) under multiple reaction monitoring mode. Each sample required about 0.5h for solid phase extraction and analysis. The limit of detections (LODs) for six AAs ranged from 0.04 to 0.58ng/cig and recoveries were within 84.5%-122.9%. The relative standard deviations of intra- and inter-day tests for 3R4F reference cigarette were less than 6% and 7%, respectively, while no more than 7% and 8% separately for a type of Virginia cigarette. The proposed method enabled minimum sample pretreatment, full automation, and high throughput with high selectivity, sensitivity, and accuracy. As a part of the validation procedure, fifteen brands of cigarettes were tested by the designed method.

  12. Influence of Geometry on a High Surface Area-Solid Phase Microextraction Sampler for Chemical Vapor Collection

    DTIC Science & Technology

    2007-06-04

    Title of Thesis: Influence of Geometry on a High Surface Area-Solid Phase Microextraction Sampler for Chemical Vapor Collection Name of...TITLE AND SUBTITLE Influence of Geometry on a High Surface Area-Solid Phase Microextraction Sampler for Chemical Vapor Collection 5a. CONTRACT...SUPPLEMENTARY NOTES 14. ABSTRACT The High Surface Area Solid Phase Microextraction (HSA-SPME) device is an internally heated sampling device designed for

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

    NASA Technical Reports Server (NTRS)

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

    1984-01-01

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

  14. 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.

  15. 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.

  16. 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.

  17. 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.

  18. 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.

  19. 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.

  20. Self-catalyzed GaAs nanowires on silicon by hydride vapor phase epitaxy

    NASA Astrophysics Data System (ADS)

    Dong, Zhenning; André, Yamina; Dubrovskii, Vladimir G.; Bougerol, Catherine; Leroux, Christine; Ramdani, Mohammed R.; Monier, Guillaume; Trassoudaine, Agnès; Castelluci, Dominique; Gil, Evelyne

    2017-03-01

    Gold-free GaAs nanowires on silicon substrates can pave the way for monolithic integration of photonic nanodevices with silicon electronic platforms. It is extensively documented that the self-catalyzed approach works well in molecular beam epitaxy but is much more difficult to implement in vapor phase epitaxies. Here, we report the first gallium-catalyzed hydride vapor phase epitaxy growth of long (more than 10 μm) GaAs nanowires on Si(111) substrates with a high integrated growth rate up to 60 μm h‑1 and pure zincblende crystal structure. The growth is achieved by combining a low temperature of 600 °C with high gaseous GaCl/As flow ratios to enable dechlorination and formation of gallium droplets. GaAs nanowires exhibit an interesting bottle-like shape with strongly tapered bases, followed by straight tops with radii as small as 5 nm. We present a model that explains the peculiar growth mechanism in which the gallium droplets nucleate and rapidly swell on the silicon surface but then are gradually consumed to reach a stationary size. Our results unravel the necessary conditions for obtaining gallium-catalyzed GaAs nanowires by vapor phase epitaxy techniques.

  1. 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.

  2. Self-catalyzed GaAs nanowires on silicon by hydride vapor phase epitaxy.

    PubMed

    Dong, Zhenning; André, Yamina; Dubrovskii, Vladimir G; Bougerol, Catherine; Leroux, Christine; Ramdani, Mohammed R; Monier, Guillaume; Trassoudaine, Agnès; Castelluci, Dominique; Gil, Evelyne

    2017-03-24

    Gold-free GaAs nanowires on silicon substrates can pave the way for monolithic integration of photonic nanodevices with silicon electronic platforms. It is extensively documented that the self-catalyzed approach works well in molecular beam epitaxy but is much more difficult to implement in vapor phase epitaxies. Here, we report the first gallium-catalyzed hydride vapor phase epitaxy growth of long (more than 10 μm) GaAs nanowires on Si(111) substrates with a high integrated growth rate up to 60 μm h(-1) and pure zincblende crystal structure. The growth is achieved by combining a low temperature of 600 °C with high gaseous GaCl/As flow ratios to enable dechlorination and formation of gallium droplets. GaAs nanowires exhibit an interesting bottle-like shape with strongly tapered bases, followed by straight tops with radii as small as 5 nm. We present a model that explains the peculiar growth mechanism in which the gallium droplets nucleate and rapidly swell on the silicon surface but then are gradually consumed to reach a stationary size. Our results unravel the necessary conditions for obtaining gallium-catalyzed GaAs nanowires by vapor phase epitaxy techniques.

  3. 1 in 4 Teens Exposed to Secondhand E-Cig Vapors: Report

    MedlinePlus

    ... also much more likely to be around e-cigarettes To use the sharing features on this page, ... ve been exposed to potentially dangerous secondhand e-cigarette vapors, a federal government study shows. E-cigarette ...

  4. Blanket and Patterned Growth of CdTe on (211)Si Substrates by Metal-Organic Vapor Phase Epitaxy

    DTIC Science & Technology

    2012-05-15

    Vapor Deposition, Epitaxial Lateral Overgrowth, Selective Epitaxy, CdTe Ishwara B. Bhat*,1, , Sunil R. Rao1, , Shashidhar Shintri2, , Randolph N...growth of CdTe on (211)Si substrates by metal- organic vapor phase epitaxy Ishwara B. Bhat*,1, Sunil R. Rao1, Shashidhar Shintri2, and Randolph N

  5. 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.

  6. Plasma-enhanced chemical vapor deposition of β-tungsten, a metastable phase

    NASA Astrophysics Data System (ADS)

    Tang, C. C.; Hess, D. W.

    1984-09-01

    Plasma-enhanced chemical vapor deposition of a metastable phase of tungsten ( β-W) is performed using tungsten hexafluoride and hydrogen as source gases. At 350 °C, the as-deposited resistivity of these films is ˜50 μΩ cm. After heat treatments between 650 and 750 °C in forming gas, the resistivity drops below 11 μΩ cm. Concomitant with this resistivity change is a phase change to α-W, the equilibrium, body-centered-cubic form.

  7. Metal organic chemical vapor deposition of phase change Ge1Sb2Te4 nanowires.

    PubMed

    Longo, Massimo; Fallica, Roberto; Wiemer, Claudia; Salicio, Olivier; Fanciulli, Marco; Rotunno, Enzo; Lazzarini, Laura

    2012-03-14

    The self-assembly of Ge(1)Sb(2)Te(4) nanowires (NWs) for phase change memories application was achieved by metal organic chemical vapor deposition, catalyzed by Au nanoislands in a narrow range of temperatures and deposition pressures. In the optimized conditions of 400 °C, 50 mbar, the NWs are Ge(1)Sb(2)Te(4) single hexagonal crystals. Phase change memory switching was reversibly induced by nanosecond current pulses through metal-contacted NWs with threshold voltage of about 1.35 V.

  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-Jörg; 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.

  9. The relationship between water vapor absorption and desorption by phospholipids and bilayer phase transitions.

    PubMed

    Mansour, Heidi M; Zografi, George

    2007-02-01

    Water vapor absorption and desorption at 25 degrees C and phase transition temperatures of phospholipid bilayers were measured as a function of relative humidity (RH) to better understand how the patterns of water vapor absorption and desorption are linked to corresponding phase changes induced by the level of hydration. Comparisons were made of the dipalmitoyl and palmitoyloleyol esters of glycerol derivatized with phosphatidyl-choline, -glycerol, -ethanolamine and with phosphatidic acid. The results suggest that the extent of water vapor absorption and desorption at a given RH reflects the combined effects of water-polar group interaction and access of water to the polar region as controlled by intra- and interbilayer molecular packing and intermolecular attractive and repulsive interactions. The results further suggest that the extent of water vapor absorption and desorption over a range of relative humidities reflects the combined effects of the polar group's ability to interact with water, the access that water has to the polar groups as determined by molecular size and various intermolecular and intrabilayer forces of attraction and repulsion, and interbilayer interactions which influence the degree of order/disorder present in the overall solid-state structure. This behavior is also reflected in the changes observed in the various bilayer phase transition temperatures as a function of RH. Analyses of absorption isotherms suggests that after exceeding a critical RH, water initially interacting with these phospholipids most likely forms either stoichiometric or nonstoichiometric crystal hydrates, as with the disaturated derivatives, or hydrated mesophases, as with the gel states of the monounsaturated derivatives.

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

    SciTech Connect

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

    1990-04-01

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

  11. Vapor-phase synthesis of mesoporous SiO2-P2O5 thin films.

    PubMed

    Nishiyama, Norikazu; Kaihara, Junji; Nishiyama, Yuko; Egashira, Yasuyuki; Ueyama, Korekazu

    2007-04-24

    Mesoporous SiO2-P2O5 films were synthesized from the vapor phase onto a silicon substrate. First, a precursor solution of cetyltrimethylammonium bromide (C16TAB), H3PO4, ethanol, and water was deposited on a silicon substrate by a spin-coating method. Then, the C16TAB-H3PO4 composite film was treated with tetraethoxysilane (TEOS) vapor at 90-180 degrees C for 2.5 h. The H3PO4-C16TAB composite formed a hexagonal structure on the silicon substrate before vapor treatment. The TEOS molecules penetrated into the film without a phase transition. The periodic mesostructure of the SiO2-P2O5 films was retained after calcination. The calcined films showed a high proton conductivity of about 0.55 S/cm at room temperature. The molar ratio of P/Si in the SiO2-P2O5 film was as high as 0.43, a level that was not attained by a premixing sol-gel method. The high phosphate group content and the ordered periodic mesostructure contributed to the high proton conductivity.

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

    SciTech Connect

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

    1999-01-01

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

  13. 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.

  14. 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.

  15. Interfacial Phase Transitions at Solid-Fluid and Liquid-Vapor Interfaces

    NASA Astrophysics Data System (ADS)

    Cornelisse, P. M. W.; Peters, C. J.; de Swaan Arons, J.

    1998-11-01

    To study the interface between a solid surface and nitrogen vapor, the theory of Cahn was applied. The Peng-Robinson equation of state (PREOS) was incorporated in the theory of Cahn to model the thermodynamic functions of the fluid. In this study the wetting transition, as earlier reported by Cahn, was shown. In addition, wetting transitions occurring at a liquid-vapor interface of the three-phase LLV equilibrium of the binary mixtures hexane/water and benzene/water were examined. It was found that by making use of the gradient theory of van der Waals, in which the PREOS was incorporated, the transitions seem to be of third order. For the case where the PREOS was replaced by the Associated-Perturbed-Anisotropic-Chain-Theory, no wetting region was found. It was argued that, in principle, it should he possible to model first-order wetting transitions with the square gradient theory.

  16. Vapor-phase fabrication and properties of continuous-filament ceramic composites.

    PubMed

    Besmann, T M; Sheldon, B W; Lowden, R A; Stinton, D P

    1991-09-06

    The continuous-filament ceramic composite is becoming recognized as necessary for new, high-temperature structural applications. Yet because of the susceptibility of the filaments to damage from traditional methods for the preparation of ceramics, vapor-phase infiltration has become the fabrication method of choice. The chemical vapor infiltration methods for producing these composites are now being studied in earnest, with the complexity of filament weaves and deposition chemistry being merged with standard heat and mass-transport relationships. Two of the most influential effects on the mechanical properties of these materials are the adhesion and frictional force between the fibers and the matrix, which can be controlled by a tailored interface coating. A variety of materials are available for producing these composites including carbide, nitride, boride, and oxide filaments and matrices. Silicon carbide-based materials are by far the most advanced and are already being used in aerospace applications.

  17. Chirality-Controlled Growth of Single-Wall Carbon Nanotubes Using Vapor Phase Epitaxy: Mechanistic Understanding and Scalable Production

    DTIC Science & Technology

    2016-09-15

    period, that is, growth plus termination, we assume the average growth rate (R̅t) of a (n, m) SWCNT at time t follows exponential kinetics ?̅?...AFRL-AFOSR-VA-TR-2016-0319 Chirality-Controlled Growth of Single-Wall Carbon Nanotubes Using Vapor Phase Epitaxy: Mechanistic Understanding and...controlled growth of single-wall carbon nanotubes using vapor phase epitaxy: mechanistic understanding and scalable production FA9550-14-1-0115 Zhou

  18. Conversion of Laser Phase Noise to Amplitude Noise in a Resonant Atomic Vapor: The Role of Laser Linewidth

    DTIC Science & Technology

    2007-11-02

    fiber optic sensors ; atomic frequency standards, applied laser spectroscopy, laser chemistry, atmospheric propagation and beam control, LIDAR/LADAR...SMC-TR-99-11 AEROSPACE REPORT NO. TR-98(8555)-14 Conversion of Laser Phase Noise to Amplitude Noise in a Resonant Atomic Vapor: The Role of Laser ...1999 3. REPORT TYPE AND DATES COVERED 4. TITLE AND SUBTITLE Conversion of Laser Phase Noise to Amplitude Noise in a Resonant Atomic Vapor: The Role

  19. Morphology Evolution of High Efficiency Perovskite Solar Cells via Vapor Induced Intermediate Phases.

    PubMed

    Zuo, Lijian; Dong, Shiqi; De Marco, Nicholas; Hsieh, Yao-Tsung; Bae, Sang-Hoon; Sun, Pengyu; Yang, Yang

    2016-12-07

    Morphology is critical component to achieve high device performance hybrid perovskite solar cells. Here, we develop a vapor induced intermediate phase (VIP) strategy to manipulate the morphology of perovskite films. By exposing the perovskite precursor films to different saturated solvent vapor atmospheres, e.g., dimethylformamide and dimethylsufoxide, dramatic film morphological evolution occurs, associated with the formation of different intermediate phases. We observe that the crystallization kinetics is significantly altered due to the formation of these intermediate phases, yielding highly crystalline perovskite films with less defect states and high carrier lifetimes. The perovskite solar cells with the reconstructed films exhibits the highest power conversion efficiency (PCE) up to 19.2% under 1 sun AM 1.5G irradiance, which is among the highest planar heterojunction perovskite solar cells. Also, the perovskite solar cells with VIP processing shows less hysteresis behavior and a stabilized power output over 18%. Our work opens up a new direction for morphology control through intermediate phase formation, and paves the way toward further enhancing the device performances of perovskite solar cells.

  20. 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.

  1. Effect of filtration by activated charcoal on the toxicological activity of cigarette mainstream smoke from experimental cigarettes.

    PubMed

    Gaworski, Charles L; Schramke, Heike; Diekmann, Joerg; Meisgen, Thomas J; Tewes, Franz J; Veltel, Detlef J; Vanscheeuwijck, Patrick M; Rajendran, Narayanan; Muzzio, Miguel; Haussmann, Hans-Juergen

    2009-07-01

    Activated charcoal (AC) filtration reportedly decreases the yields of smoke vapor phase constituents including some identified as human carcinogens and respiratory irritants. Non-clinical studies including chemical smoke analysis, in vitro cytotoxicity and mutagenicity (bacterial and mammalian cells), and in vivo subchronic rat inhalation studies were carried out using machine smoking at ISO conditions with lit-end research cigarettes containing AC filters. The objective was to assess whether AC filter technology would alter the established toxicity profile of mainstream smoke by increasing or decreasing any known toxicological properties, or elicit new ones. The reduced yield of vapor phase irritants from AC filter cigarettes correlated with markedly decreased in vitro cytotoxicity and in vivo morphology of the nose and lower respiratory tract. Increased yields of particulate phase constituents (e.g. polycyclic aromatic hydrocarbons) in AC filtered smoke were noted in comparison to controls in some studies. The in vitro bacterial mutagenicity of AC filtered smoke particulate preparations was occasionally increased over control levels. Laryngeal epithelial thickness was increased in some rats inhaling AC filtered smoke in comparison to controls, an effect perhaps related to higher inspiratory flow. When tested under more intense Massachusetts Department of Public Health smoking conditions, AC filter associated reductions in vapor phase constituent yields were smaller than those seen with ISO conditions, but the effect on in vitro cytotoxicity remained.

  2. 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

  3. Comparative study of solution-phase and vapor-phase deposition of aminosilanes on silicon dioxide surfaces.

    PubMed

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

    2014-02-01

    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.

  4. Influence of gas phase equilibria on the chemical vapor deposition of graphene.

    PubMed

    Lewis, Amanda M; Derby, Brian; Kinloch, Ian A

    2013-04-23

    We have investigated the influence of gas phase chemistry on the chemical vapor deposition of graphene in a hot wall reactor. A new extended parameter space for graphene growth was defined through literature review and experimentation at low pressures (≥0.001 mbar). The deposited films were characterized by scanning electron microscopy, Raman spectroscopy, and dark field optical microscopy, with the latter showing promise as a rapid and nondestructive characterization technique for graphene films. The equilibrium gas compositions have been calculated across this parameter space. Correlations between the graphene films grown and prevalent species in the equilibrium gas phase revealed that deposition conditions associated with a high acetylene equilibrium concentration lead to good quality graphene deposition, and conditions that stabilize large hydrocarbon molecules in the gas phase result in films with multiple defects. The transition between lobed and hexagonal graphene islands was found to be linked to the concentration of the monatomic hydrogen radical, with low concentrations associated with hexagonal islands.

  5. E-cigarettes: a rapidly growing Internet phenomenon.

    PubMed

    Yamin, Cyrus K; Bitton, Asaf; Bates, David W

    2010-11-02

    Electronic cigarettes (e-cigarettes) aerosolize nicotine and produce a vapor that emulates that of cigarettes but purportedly has fewer traditional toxins than secondhand smoke. Although e-cigarettes are widely sold online and by retailers, new research suggests that they may contain unexpected toxins and may provide unreliable nicotine delivery. Many countries have already banned or strictly regulated e-cigarettes. Currently in the United States, e-cigarettes are exempt from regulation as drug-delivery devices. Meanwhile, the presence of e-cigarettes on the Internet, including in Web searches, virtual user communities, and online stores where people sell e-cigarettes on commission, is increasing rapidly. Physicians should be aware of the popularity, questionable efficacy claims, and safety concerns of e-cigarettes so that they may counsel patients against use and advocate for research to inform an evidence-based regulatory approach.

  6. New mechanism for autocatalytic decomposition of H2CO3 in the vapor phase.

    PubMed

    Ghoshal, Sourav; Hazra, Montu K

    2014-04-03

    In this article, we present high level ab initio calculations investigating the energetics of a new autocatalytic decomposition mechanism for carbonic acid (H2CO3) in the vapor phase. The calculation have been performed at the MP2 level of theory in conjunction with aug-cc-pVDZ, aug-cc-pVTZ, and 6-311++G(3df,3pd) basis sets as well as at the CCSD(T)/aug-cc-pVTZ level. The present study suggests that this new decomposition mechanism is effectively a near-barrierless process at room temperature and makes vapor phase of H2CO3 unstable even in the absence of water molecules. Our calculation at the MP2/aug-cc-pVTZ level predicts that the effective barrier, defined as the difference between the zero-point vibrational energy (ZPE) corrected energy of the transition state and the total energy of the isolated starting reactants in terms of bimolecular encounters, is nearly zero for the autocatalytic decomposition mechanism. The results at the CCSD(T)/aug-cc-pVTZ level of calculations suggest that the effective barrier, as defined above, is sensitive to some extent to the levels of calculations used, nevertheless, we find that the effective barrier height predicted at the CCSD(T)/aug-cc-pVTZ level is very small or in other words the autocatalytic decomposition mechanism presented in this work is a near-barrierless process as mentioned above. Thus, we suggest that this new autocatalytic decomposition mechanism has to be considered as the primary mechanism for the decomposition of carbonic acid, especially at its source, where the vapor phase concentration of H2CO3 molecules reaches its highest levels.

  7. 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

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

    NASA Astrophysics Data System (ADS)

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

    1990-01-01

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

  9. Direct calculation of liquid-vapor phase equilibria from transition matrix Monte Carlo simulation

    NASA Astrophysics Data System (ADS)

    Errington, Jeffrey R.

    2003-06-01

    An approach for directly determining the liquid-vapor phase equilibrium of a model system at any temperature along the coexistence line is described. The method relies on transition matrix Monte Carlo ideas developed by Fitzgerald, Picard, and Silver [Europhys. Lett. 46, 282 (1999)]. During a Monte Carlo simulation attempted transitions between states along the Markov chain are monitored as opposed to tracking the number of times the chain visits a given state as is done in conventional simulations. Data collection is highly efficient and very precise results are obtained. The method is implemented in both the grand canonical and isothermal-isobaric ensemble. The main result from a simulation conducted at a given temperature is a density probability distribution for a range of densities that includes both liquid and vapor states. Vapor pressures and coexisting densities are calculated in a straightforward manner from the probability distribution. The approach is demonstrated with the Lennard-Jones fluid. Coexistence properties are directly calculated at temperatures spanning from the triple point to the critical point.

  10. 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

  11. 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.

  12. Liquid-vapor transformations with surfactants. Phase-field model and Isogeometric Analysis

    NASA Astrophysics Data System (ADS)

    Bueno, Jesus; Gomez, Hector

    2016-09-01

    Surfactants are compounds that find energetically favorable to be located at the boundaries between fluids. They are able to modify the properties of those interfaces, for example, reducing surface tension. Here, we propose a new model for liquid-vapor flows with surfactants which captures the dynamics of the surfactant and accounts for phase transformations in the fluid. The aforementioned model is derived from a free energy functional by using a Coleman-Noll approach. The proposed theory emanates from the isothermal Navier-Stokes-Korteweg equations, which describe single-component two-phase flow and naturally allow for phase transformations. We believe that our model has significant potential to study the influence of surfactants in vaporization and condensation processes. From a numerical point of view, the proposed model poses significant challenges to existing discretization methods, including stiffness in space and time, internal and boundary layers as well as higher-order partial differential operators. To overcome these challenges we propose algorithms based on Isogeometric Analysis, which permit an accurate and efficient discretization. Finally, we illustrate the viability of the theoretical framework and the effectiveness of our algorithms by solving several numerical problems in two and three dimensions.

  13. 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).

  14. 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).

  15. 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.

  16. 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.

  17. 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.

  18. Selective growth of GaAs by organometallic vapor phase epitaxy at atmospheric pressure

    NASA Astrophysics Data System (ADS)

    Azoulay, R.; Dugrand, L.

    1991-01-01

    Complete selective epitaxy of GaAs by organometallic vapor phase epitaxy at atmospheric pressure was achieved by using TMG, AsH3, and AsCl3 as starting gases. Selectivity was observed at growth temperatures ranging from 650 to 750 °C. The blocking of polycrystal deposition on the mask, Si3N4, or W, is attributed to the adsorption of HCl on the mask, thus preventing the nucleation of GaAs. On the openings, the growth rate may be adjusted by controlling the TMG/AsCl3 ratio. When TMG/AsCl3<1, no growth occurs, but etching is observed.

  19. Investigation of fragmentation processes following core photoionization of organometallic molecules in the vapor phase

    NASA Astrophysics Data System (ADS)

    Nagaoka, Shin-ichi; Suzuki, Shinzo; Koyano, Inosuke

    1988-04-01

    Ionic fragmentation processes following ( n - 1)d core level photoionization of organometallic molecules have been studied in the vapor phase using synchrotron radiation. Results on tetramethyllead, tetramethyltin and tetramethylgermanium are reported. The threshold electron spectra and the photoionization efficiency curves of these molecules are presented and discussed. It is concluded that the ( n - 1)d 9 core-hole state of M(CH 3) 4 (M  Pb, Sn or Ge) is split into five sublevels owing to both the spin-orbi and the electrostatic perturbations by the methyl groups, and that the M + ions are predominantly produced following ( n - 1)d photoionization.

  20. Thermal injury patterns associated with electronic cigarettes

    PubMed Central

    Jiwani, Alisha Z; Williams, James F; Rizzo, Julie A; Chung, Kevin K; King, Booker T; Cancio, Leopoldo C

    2017-01-01

    E-cigarettes are typically lithium-ion battery-operated devices that simulate smoking by heating a nicotine-solution into a vapor that the user inhales. E-cigarette use is becoming rapidly popular as an alternative to traditional cigarette smoking. This report describes an emerging problem associated with e-cigarettes, consisting of 10 thermally injured patients seen at a single burn center over a 2-year period from 2014 to 2016. Our cohort was comprised mainly of young adults who sustained mixed partial and full thickness burns as a result of e-cigarette-related explosions. In many documented scenarios, a malfunctioning or over-heated battery is the cause. Our data support the need for increased awareness among healthcare providers and the general public of the potential harms of e-cigarette use, modification, storage, and charging. PMID:28123861

  1. [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.

  2. Phase transitions and criticality in small systems: vapor-liquid transition in nanoscale spherical cavities.

    PubMed

    Neimark, Alexander V; Vishnyakov, Aleksey

    2006-05-18

    Phase transformations in fluids confined to nanoscale pores, which demonstrate characteristic signatures of first-order phase transitions, have been extensively documented in experiments and molecular simulations. They are characterized by a pronounced hysteresis, which disappears above a certain temperature. A rigorous interpretation of these observations represents a fundamental problem from the point of view of statistical mechanics. Nanoscale systems are essentially small, finite volume systems, in which the concept of the thermodynamic limit is no longer valid, and the statistical ensembles are not equivalent. Here, we present a rigorous approach to the description and molecular simulations of phase transitions and criticality in small confined systems, as illustrated by the example of vapor-liquid transition (capillary condensation) in spherical cavities. The method is based on the analysis of the canonical ensemble isotherms, which can be generated by the gauge cell Monte Carlo simulation method. The method allows one to define the critical temperature of phase transition, conditions of phase equilibrium, limits of stability of metastable states, and nucleation barriers, which determine hysteretic phase transformations.

  3. Bubbles in liquids with phase transition. Part 1. On phase change of a single vapor bubble in liquid water

    NASA Astrophysics Data System (ADS)

    Dreyer, Wolfgang; Duderstadt, Frank; Hantke, Maren; Warnecke, Gerald

    2012-11-01

    In the forthcoming second part of this paper a system of balance laws for a multi-phase mixture with many dispersed bubbles in liquid is derived where phase transition is taken into account. The exchange terms for mass, momentum and energy explicitly depend on evolution laws for total mass, radius and temperature of single bubbles. Therefore in the current paper we consider a single bubble of vapor and inert gas surrounded by the corresponding liquid phase. The creation of bubbles, e.g. by nucleation is not taken into account. We study the behavior of this bubble due to condensation and evaporation at the interface. The aim is to find evolution laws for total mass, radius and temperature of the bubble, which should be as simple as possible but consider all relevant physical effects. Special attention is given to the effects of surface tension and heat production on the bubble dynamics as well as the propagation of acoustic elastic waves by including slight compressibility of the liquid phase. Separately we study the influence of the three phenomena heat conduction, elastic waves and phase transition on the evolution of the bubble. We find ordinary differential equations that describe the bubble dynamics. It turns out that the elastic waves in the liquid are of greatest importance to the dynamics of the bubble radius. The phase transition has a strong influence on the evolution of the temperature, in particular at the interface. Furthermore the phase transition leads to a drastic change of the water content in the bubble. It is shown that a rebounding bubble is only possible, if it contains in addition an inert gas. In Part 2 of the current paper the equations derived are sought in order to close the system of equations for multi-phase mixture balance laws for dispersed bubbles in liquids involving phase change.

  4. Impact of Liquid-Vapor to Liquid-Liquid-Vapor Phase Transitions on Asphaltene-Rich Nanoaggregate Behavior in Athabasca Vacuum Residue + Pentane Mixtures

    SciTech Connect

    Long, Bingwen; Chodakowski, Martin; Shaw, John M.

    2013-06-05

    The bulk phase behavior of heavy oil + alkane mixtures and the behavior of the asphaltenes that they contain are topics of importance for the design and optimization of processes for petroleum production, transport, and refining and for performing routine saturates, aromatics, resins, and asphaltenes (SARA) analyses. In prior studies, partial phase diagrams and phase behavior models for Athabasca vacuum residue (AVR) comprising 32 wt % pentane asphaltenes + n-alkanes were reported. For mixtures with pentane, observed phase behaviors included single-phase liquid as well as liquid–liquid, liquid–liquid–vapor, and liquid–liquid–liquid–vapor regions. Dispersed solids were detected under some conditions as well but not quantified. In this work, small-angle X-ray scattering (SAXS) is used to study nanostructured materials in liquid phases present in AVR + n-pentane mixtures from 50 to 170 °C at mixture bubble pressure. The investigation focuses on the impact of the transition from a single AVR-rich liquid to co-existing pentane-rich and AVR-rich liquids on the nanostructure and the nanostructures most resistant to aggregation as the pentane composition axis is approached. Background scattering subtraction was performed using global mixture composition. The robustness of this assumption with respect to values obtained for coefficients appearing in a two level Beaucage unified equation fit is demonstrated. The nanostructured material is shown to arise at two length scales from 1 to 100 wt % AVR. Smaller nanostructures possess mean radii less than 50 Å, while the larger nanostructures possess mean radii greater than 250 Å. The addition of pentane to the AVR causes an increasingly large fraction of the large and small nanostructures to grow in size. Only nanostructures resistant to aggregation remain in the pentane-rich phase as the 0 wt % AVR axis is approached. Step changes in aggregation identified from changes in average radius of gyration, scattering

  5. A Kinetic Model for GaAs Growth by Hydride Vapor Phase Epitaxy

    SciTech Connect

    Schulte, Kevin L.; Simon, John; Jain, Nikhil; Young, David L.; Ptak, Aaron J.

    2016-11-21

    Precise control of the growth of III-V materials by hydride vapor phase epitaxy (HVPE) is complicated by the fact that the growth rate depends on the concentrations of nearly all inputs to the reactor and also the reaction temperature. This behavior is in contrast to metalorganic vapor phase epitaxy (MOVPE), which in common practice operates in a mass transport limited regime where growth rate and alloy composition are controlled almost exclusively by flow of the Group III precursor. In HVPE, the growth rate and alloy compositions are very sensitive to temperature and reactant concentrations, which are strong functions of the reactor geometry. HVPE growth, particularly the growth of large area materials and devices, will benefit from the development of a growth model that can eventually be coupled with a computational fluid dynamics (CFD) model of a specific reactor geometry. In this work, we develop a growth rate law using a Langmuir-Hinshelwood (L-H) analysis, fitting unknown parameters to growth rate data from the literature that captures the relevant kinetic and thermodynamic phenomena of the HVPE process. We compare the L-H rate law to growth rate data from our custom HVPE reactor, and develop quantitative insight into reactor performance, demonstrating the utility of the growth model.

  6. 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.

  7. 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.

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

    USGS Publications Warehouse

    Cranor, W.L.; Alvarez, D.A.; Huckins, J.N.; Petty, J.D.

    2009-01-01

    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??m3??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??m3??g-1??d-1 with relative standard deviations of 8.4% and 8.6% respectively.

  9. 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.

  10. Phase degradation in BxGa1-xN films grown at low temperature by metalorganic vapor phase epitaxy

    NASA Astrophysics Data System (ADS)

    Gunning, Brendan P.; Moseley, Michael W.; Koleske, Daniel D.; Allerman, Andrew A.; Lee, Stephen R.

    2017-04-01

    Using metalorganic vapor phase epitaxy, a comprehensive study of BxGa1-xN growth on GaN and AlN templates is described. BGaN growth at high-temperature and high-pressure results in rough surfaces and poor boron incorporation efficiency, while growth at low-temperature and low-pressure (750-900 °C and 20 Torr) using nitrogen carrier gas results in improved surface morphology and boron incorporation up to 7.4% as determined by nuclear reaction analysis. However, further structural analysis by transmission electron microscopy and x-ray pole figures points to severe degradation of the high boron composition films, into a twinned cubic structure with a high density of stacking faults and little or no room temperature photoluminescence emission. Films with <1% triethylboron (TEB) flow show more intense, narrower x-ray diffraction peaks, near-band-edge photoluminescence emission at 362 nm, and primarily wurtzite-phase structure in the x-ray pole figures. For films with >1% TEB flow, the crystal structure becomes dominated by the cubic phase. Only when the TEB flow is zero (pure GaN), does the cubic phase entirely disappear from the x-ray pole figure, suggesting that under these growth conditions even very low boron compositions lead to mixed crystalline phases.

  11. Organic solvents vapor pressure and relative humidity effects on the phase transition rate of α and β forms of tegafur.

    PubMed

    Petkune, Sanita; Bobrovs, Raitis; Actiņš, Andris

    2012-01-01

    The objective of this work was to investigate the relative humidity (RH) and solvent vapor pressure effects on the phase transition dynamics between tegafur polymorphic forms that do not form hydrates and solvates. The commercially available α and β modifications of 5-fluoro-1-(tetrahydro-2-furyl)-uracil, known as the antitumor agent tegafur, were used as model materials for this study. While investigating the phase transitions of α and β tegafur under various partial pressures of methanol, n-propanol, n-butanol, and water vapor, it was determined that the phase transition rate increased in the presence of solvent vapors, even though no solvates were formed. By increasing the relative air humidity from 20% to 80%, the phase transition rate constant of α and β tegafur was increased about 60 times. After increasing the partial pressure of methanol, n-propanol, or n-butanol vapor, the phase transition rate constant did not change, but the extent of phase transformation was increased. In the homologous row of n-alcohols, the phase transition rate constant decreased with increasing carbon chain length. The dependence of phase transformation extent versus the RH corresponded to the polymolecular adsorption isotherm with a possible capillary condensation effect.

  12. 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.

  13. Mathematical modeling of planar and spherical vapor-liquid phase interfaces for multicomponent fluids

    NASA Astrophysics Data System (ADS)

    Celný, David; Vinš, Václav; Planková, Barbora; Hrubý, Jan

    2016-03-01

    Development of methods for accurate modeling of phase interfaces is important for understanding various natural processes and for applications in technology such as power production and carbon dioxide separation and storage. In particular, prediction of the course of the non-equilibrium phase transition processes requires knowledge of the properties of the strongly curved phase interfaces of microscopic droplets. In our work, we focus on the spherical vapor-liquid phase interfaces for binary mixtures. We developed a robust computational method to determine the density and concentration profiles. The fundamentals of our approach lie in the Cahn-Hilliard gradient theory, allowing to transcribe the functional formulation into a system of ordinary Euler-Langrange equations. This system is then split and modified into a shape suitable for iterative computation. For this task, we combine the Newton-Raphson and the shooting methods providing a good convergence speed. For the thermodynamic roperties, the PC-SAFT equation of state is used. We determine the density and concentration profiles for spherical phase interfaces at various saturation factors for the binary mixture of CO2 and C9H20. The computed concentration profiles allow to the determine the work of formation and other characteristics of the microscopic droplets.

  14. 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 π-π 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 π-π 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

  15. Smokers' and E-Cigarette Users' Perceptions about E-Cigarette Warning Statements.

    PubMed

    Wackowski, Olivia A; Hammond, David; O'Connor, Richard J; Strasser, Andrew A; Delnevo, Cristine D

    2016-06-30

    Cigarette warning labels are important sources of risk information, but warning research for other tobacco products is limited. This study aimed to gauge perceptions about warnings that may be used for e-cigarettes. We conducted six small focus groups in late 2014/early 2015 with adult current e-cigarette users and cigarette-only smokers. Participants rated and discussed their perceptions of six e-cigarette warning statements, and warnings in two existing Vuse and MarkTen e-cigarette ads. Participants were open to e-cigarette warnings and provided the strongest reactions to statements warning that e-liquid/e-vapor or e-cigarettes can be poisonous, contain toxins, or are "not a safe alternative to smoking". However, many also noted that these statements were exaggerated, potentially misleading, and could scare smokers away from reducing their harm by switching to e-cigarettes. Opinions on the Food and Drug Administration's proposed nicotine addiction warning and warnings that e-cigarettes had not been approved for smoking cessation or had unknown health effects were mixed. Participants perceived MarkTen's advertisement warning to be stronger and more noticeable than Vuse's. Care should be taken in developing e-cigarette warnings given their relative recentness and potential for harm reduction compared to other tobacco products. Additional research, including with varied audiences, would be instructive.

  16. Smokers’ and E-Cigarette Users’ Perceptions about E-Cigarette Warning Statements

    PubMed Central

    Wackowski, Olivia A.; Hammond, David; O’Connor, Richard J.; Strasser, Andrew A.; Delnevo, Cristine D.

    2016-01-01

    Cigarette warning labels are important sources of risk information, but warning research for other tobacco products is limited. This study aimed to gauge perceptions about warnings that may be used for e-cigarettes. We conducted six small focus groups in late 2014/early 2015 with adult current e-cigarette users and cigarette-only smokers. Participants rated and discussed their perceptions of six e-cigarette warning statements, and warnings in two existing Vuse and MarkTen e-cigarette ads. Participants were open to e-cigarette warnings and provided the strongest reactions to statements warning that e-liquid/e-vapor or e-cigarettes can be poisonous, contain toxins, or are “not a safe alternative to smoking”. However, many also noted that these statements were exaggerated, potentially misleading, and could scare smokers away from reducing their harm by switching to e-cigarettes. Opinions on the Food and Drug Administration’s proposed nicotine addiction warning and warnings that e-cigarettes had not been approved for smoking cessation or had unknown health effects were mixed. Participants perceived MarkTen’s advertisement warning to be stronger and more noticeable than Vuse’s. Care should be taken in developing e-cigarette warnings given their relative recentness and potential for harm reduction compared to other tobacco products. Additional research, including with varied audiences, would be instructive. PMID:27376310

  17. Aldehyde Detection in Electronic Cigarette Aerosols

    PubMed Central

    2017-01-01

    Acetaldehyde, acrolein, and formaldehyde are the principal toxic aldehydes present in cigarette smoke and contribute to the risk of cardiovascular disease and noncancerous pulmonary disease. The rapid growth of the use of electronic cigarettes (e-cigarettes) has raised concerns over emissions of these harmful aldehydes. This work determines emissions of these aldehydes in both free and bound (aldehyde–hemiacetal) forms and other carbonyls from the use of e-cigarettes. A novel silicon microreactor with a coating phase of 4-(2-aminooxyethyl)-morpholin-4-ium chloride (AMAH) was used to trap carbonyl compounds in the aerosols of e-cigarettes via oximation reactions. AMAH–aldehyde adducts were measured using gas chromatography–mass spectrometry. 1H nuclear magnetic resonance spectroscopy was used to analyze hemiacetals in the aerosols. These aldehydes were detected in the aerosols of all e-cigarettes. Newer-generation e-cigarette devices generated more aldehydes than the first-generation e-cigarettes because of higher battery power output. Formaldehyde–hemiacetal was detected in the aerosols generated from some e-liquids using the newer e-cigarette devices at a battery power output of 11.7 W and above. The emission of these aldehydes from all e-cigarettes, especially higher levels of aldehydes from the newer-generation e-cigarette devices, indicates the risk of using e-cigarettes. PMID:28393137

  18. 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.

  19. 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.

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

    PubMed

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

    2010-05-06

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

  1. 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.

  2. 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 (20–80 nm in diameter, up to 6 μm in length, density <40 nm apart) at substrate temperatures down to 300°C. 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

  3. Epitaxial integration of nanowires in microsystems by local micrometer-scale vapor-phase epitaxy.

    PubMed

    Mølhave, Kristian; Wacaser, Brent A; Petersen, Dirch Hjorth; Wagner, Jakob B; Samuelson, Lars; Bøggild, Peter

    2008-10-01

    Free-standing epitaxially grown nanowires provide a controlled growth system and an optimal interface to the underlying substrate for advanced optical, electrical, and mechanical nanowire device connections. Nanowires can be grown by vapor-phase epitaxy (VPE) methods such as chemical vapor deposition (CVD) or metal organic VPE (MOVPE). However, VPE of semiconducting nanowires is not compatible with several microfabrication processes due to the high synthesis temperatures and issues such as cross-contamination interfering with the intended microsystem or the VPE process. By selectively heating a small microfabricated heater, growth of nanowires can be achieved locally without heating the entire microsystem, thereby reducing the compatibility problems. The first demonstration of epitaxial growth of silicon nanowires by this method is presented and shows that the microsystem can be used for rapid optimization of VPE conditions. The important issue of the cross-contamination of other parts of the microsystem caused by the local growth of nanowires is also investigated by growth of GaN near previously grown silicon nanowires. The design of the cantilever heaters makes it possible to study the grown nanowires with a transmission electron microscope without sample preparation.

  4. 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.

  5. 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.

  6. Susceptibility of Klebsiella pneumoniae on coriander leaves to liquid- and vapor-phase ethanol.

    PubMed

    Krusong, Warawut; Pornpukdeewatana, Soisuda; Teerarak, Montinee

    2016-05-01

    The bio-control of ethanol on Klebsiella pneumoniae on fresh coriander leaves for significantly reducing consumer health risk was investigated. Washed and sterilized leaves of coriander were inoculated with K. pneumoniae cultured in Trypticase Soy broth. Susceptibility of the K. pneumoniae to liquid- and evaporated vapor-phase ethanol (EVE) was then examined in vitro Complete inhibition of K. pneumoniae was found with 18% (v/v) liquid ethanol. Exposure for 15 min to EVE (9.00 ± 0.8 mmol L(-1)) completely destroyed K. pneumoniae (4.04 ± 0.02 log CFU/ml) spread on Mueller Hilton agar at 30 ± 2°C. The effect of EVE with and without evaporated water vapor (EWV) on the susceptibility of K. pneumoniae on fresh coriander leaves was examined. While exposure to EVE affected the survival of K. pneumoniae, the degree of reduction depended on both the inoculation level and the EWV. Complete reduction of K. pneumoniae was achieved for the low inoculation level by EVE alone (37 ± 2% relative humidity; RH) but susceptibility was reduced with EWV (high RH; 80 ± 2%). Scanning electron microscope (SEM) images of inoculated coriander leaves confirm the effects of EVE in reducing levels of K. pneumoniae Exposure to EVE alone proved an effective bio-control for K. pneumoniae on fresh coriander leaves.

  7. Procedure 5 - Quality Assurance Requirements For Vapor Phase Mercury Continuous Emissions Monitoring Systems And Sorbent Trap Monitoring Systems Used For Compliance Determination At Stationary Sources

    EPA Pesticide Factsheets

    Promulgated quality assurance procedure 5 Quality Assurance Requirements For Vapor Phase Mercury Continuous Emissions Monitoring Systems And Sorbent Trap Monitoring Systems Used For Compliance Determination At Stationary Sources

  8. Procedure 5 Quality Assurance Requirements For Vapor Phase Mercury Continuous Emissions Monitoring Systems And Sorbent Trap Monitoring Systems Used For Compliance Determination At Stationary Sources

    EPA Pesticide Factsheets

    Promulgated quality assurance Procedure 5 Quality Assurance Requirements For Vapor Phase Mercury Continuous Emissions Monitoring Systems And Sorbent Trap Monitoring Systems Used For Compliance Determination At Stationary Sources

  9. CRYOCHEM, Thermodynamic Model for Cryogenic Chemical Systems: Solid-Vapor and Solid-Liquid-Vapor Phase Equilibria Toward Applications on Titan and Pluto

    NASA Astrophysics Data System (ADS)

    Tan, S. P.; Kargel, J. S.; Adidharma, H.; Marion, G. M.

    2014-12-01

    Until in-situ measurements can be made regularly on extraterrestrial bodies, thermodynamic models are the only tools to investigate the properties and behavior of chemical systems on those bodies. The resulting findings are often critical in describing physicochemical processes in the atmosphere, surface, and subsurface in planetary geochemistry and climate studies. The extremely cold conditions on Triton, Pluto and other Kuiper Belt Objects, and Titan introduce huge non-ideality that prevents conventional models from performing adequately. At such conditions, atmospheres as a whole—not components individually—are subject to phase equilibria with their equilibrium solid phases or liquid phases or both. A molecular-based thermodynamic model for cryogenic chemical systems, referred to as CRYOCHEM, the development of which is still in progress, was shown to reproduce the vertical composition profile of Titan's atmospheric methane measured by the Huygens probe (Tan et al., Icarus 2013, 222, 53). Recently, the model was also used to describe Titan's global circulation where the calculated composition of liquid in Ligeia Mare is consistent with the bathymetry and microwave absorption analysis of T91 Cassini fly-by data (Tan et al., 2014, submitted). Its capability to deal with equilibria involving solid phases has also been demonstrated (Tan et al., Fluid Phase Equilib. 2013, 360, 320). With all those previous works done, our attention is now shifting to the lower temperatures in Titan's tropopause and on Pluto's surface, where much technical development remains for CRYOCHEM to assure adequate performance at low temperatures. In these conditions, solid-vapor equilibrium (SVE) is the dominant phase behavior that determines the composition of the atmosphere and the existing ices. Another potential application is for the subsurface phase equilibrium, which also involves liquid, thus three-phase equilibrium: solid-liquid-vapor (SLV). This presentation will discuss the

  10. 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.

  11. Liquid-vapor phase equilibria and the thermodynamic properties of 2-methylpropanol- n-alkyl propanoate solutions

    NASA Astrophysics Data System (ADS)

    Suntsov, Yu. K.; Goryunov, V. A.; Chuikov, A. M.; Meshcheryakov, A. V.

    2016-08-01

    The boiling points of solutions of five binary systems are measured via ebulliometry in the pressure range of 2.05-103.3 kPa. Equilibrium vapor phase compositions, the values of the excess Gibbs energies, enthalpies, and entropies of solution of these systems are calculated. Patterns in the changes of phase equilibria and thermodynamic properties of solutions are established, depending on the compositions and temperatures of the systems. Liquid-vapor equilibria in the systems are described using the equations of Wilson and the NRTL (Non-Random Two-Liquid Model).

  12. Method for the Determination of Ammonia in Mainstream Cigarette Smoke Using Ion Chromatography

    PubMed Central

    Watson, Christina Vaughan; Feng, June; Valentin-Blasini, Liza; Stanelle, Rayman; Watson, Clifford H.

    2016-01-01

    Ammonia in mainstream smoke is present in both the particulate and vapor phases. The presence of ammonia in the cigarette filler material and smoke is of significance because of the potential role ammonia could have in raising the “smoke pH.” An increased smoke pH could shift a fraction of total nicotine to free-base nicotine, which is reportedly more rapidly absorbed by the smoker. Methods measuring ammonia in smoke typically employ acid filled impingers to trap the smoke. We developed a fast, reliable method to measure ammonia in mainstream smoke without the use of costly and time consuming impingers to examine differences in ammonia delivery. The method uses both a Cambridge filter pad and a Tedlar bag to capture particulate and vapor phases of the smoke. We quantified ammonia levels in the mainstream smoke of 50 cigarette brands from 5 manufacturers. Ammonia levels ranged from approximately 1μg to 23μg per cigarette for ISO smoking conditions and 38μg to 67μg per cigarette for Canadian intense smoking conditions and statistically significance differences were observed between brands and manufacturers. Our findings suggest that ammonia levels vary by brand and are higher under Canadian intense smoking conditions. PMID:27415766

  13. Improvements in the vapor-time profile analysis of explosive odorants using solid-phase microextraction.

    PubMed

    Young, Mimy; Schantz, Michele; MacCrehan, William

    2016-07-15

    A modified approach for characterization of the vapor-time profile of the headspace odors of explosives was developed using solid-phase microextraction (SPME) incorporating introduction of an externally-sampled internal standard (ESIS) followed by gas chromatography/mass spectrometry (GC/MS) analysis. With this new method, reproducibility of the measurements of 2-ethyl-1-hexanol and cyclohexanone were improved compared to previous work (Hoffman et al., 2009; Arthur and Pawliszyn, 1990) through the use of stable-isotope-labeled internal standards. Exposing the SPME fiber to the ESIS after sampling the target analyte proved to be advantageous, while still correcting for fiber variability and detector drift. For the analysis of high volatility compounds, incorporation of the ESIS using the SPME fiber in the retracted position minimized the subsequent competitive loss of the target analyte, allowing for much longer sampling times.

  14. Low oxygen and carbon incorporation in AIGaAs using tritertiarybutylaluminum in organometallic vapor phase epitaxy

    NASA Astrophysics Data System (ADS)

    Wang, C. A.; Salimand, S.; Jensen, K. F.; Jones, A. C.

    1996-05-01

    High-quality AIGaAs epilayers have been grown by low pressure organometallic vapor phase epitaxy with a new aluminum precursor tritertiarybutylaluminum (TTBAl). Layers grown at 650°C have a featureless mirror surface morphology and strong room temperature photoluminescence. Carbon was not detectable in chemical analysis by secondary ion mass spectroscopy, nor in low temperature (4K) photoluminescence spectra. Oxygen concentration in Al0.25Ga0.75As is as low as ˜2-3 × 1017 cm-3. Nominally undoped AIGaAs layers exhibit n-type conductiv-ity with electron concentrations at ˜ 1-1.5 × 1016 cm-3. A high degree of compo-sitional uniformity over 5 cm diam substrates (0.268 ±0.001) was obtained. These results indicate the potential for TTBA1 as an aluminum precursor for low temperature growth of Al-containing III-V alloys.

  15. 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.

  16. 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

  17. Preparation of graphene sponge by vapor phase reduction for oil and organic solvent removal

    NASA Astrophysics Data System (ADS)

    Wu, Ruihan; Yu, Baowei; Jin, Xinyan; Liu, Xiaoyang; Bai, Yitong; Chen, Lingyun; Ming, Zhu; Yang, Hua; Yang, Sheng-Tao; Luo, Jianbin

    2016-10-01

    Due to the porous structure and hydrophobicity, graphene sponge has huge adsorption capacity for oils and organic solvents. In this study, we reported that graphene sponge could be prepared by vapor phase reduction (denoted as VPRGS) for oil and organic solvent removal. Graphene oxide was lyophilized and reduced by steamy hydrazine hydrate to produce VPRGS. VPRGS had huge capacity for oils and organic solvents (72-224 g g-1). In particular, the adsorption capacity for crude oil reached 165 g g-1, suggesting that VPRGS could be applied in oil leakage remediation. VPRGS could treat pollutants both in pure liquid form and in the simulated sea water, where the hydrophobic nature of VPRGS allowed the floating of VPRGS on simulated sea water. VPRGS could be easily regenerated without obvious capacity loss up to 9 cycles. The implications to the applications of VPRGS in oil/water separation and water remediation are discussed.

  18. Single-crystal CdSe nanowires prepared via vapor-phase growth assisted with silicon.

    PubMed

    Wang, Z Y; Zhang, L D; Ye, C H; Fang, X S; Xiao, Z D; Kong, M G

    2005-12-01

    Hexagonal cadmium selenide (CdSe) nanowires, with diameter around 20 nm, were synthesized using a simple vapor-phase growth. Silicon (Si) powder acts as a source material assisting the synthesis, which is very important to the formation of the CdSe nanowires. We also suggest that self-catalysis at the Cd-terminated (0001) surface, together with the assistance action of Si, leads to the formation of wire-like structures to be formed. Meanwhile, the assistance of Si is responsible for the fineness and uniformity of the CdSe nanowires. The possible growth mechanism of the CdSe nanowires is proposed, and the optical property of the as-grown CdSe nanowires is characterized.

  19. Vapor Phase Ketonization of Acetic Acid on Ceria Based Metal Oxides

    SciTech Connect

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

    2013-06-27

    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. Vapor phase synthesis of TaS2 nanocrystals with iodine as transport agent

    NASA Astrophysics Data System (ADS)

    Jin, Gangtae; Kim, Chaeeun; Jo, Hyunjin; Kwon, Se-Hun; Jeong, Seong-Jun; Lee, Han-Bo-Ram; Ahn, Ji-Hoon

    2017-04-01

    TaS2 is a transition metal dichalcogenide material with a layered two-dimensional crystal structure and physically interesting behavior. 1T-TaS2 in particular exhibits a complex interaction between electron–electron and electron–lattice, as well as unique two-dimensional charge density wave characteristics with varying phase transitions depending on the temperature range. However, few reports exist on the synthesis of TaS2 crystals, and a relatively long time is required for the synthesis of TaS2 nanostructures. Here, we present an efficient method for 1T-TaS2 synthesis by chemical vapor deposition using iodine as a transport agent. We successfully synthesized 1T-TaS2 nanocrystals or thin films in a short processing time of a few hours, and their structural and chemical properties were characterized.

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

    PubMed

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

    2012-08-07

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

  2. Fabrication and characterization of dry conducting polymer actuator by vapor phase polymerization of polypyrrole.

    PubMed

    Ramasamy, Madeshwaran Sekkarapatti; Mahapatra, Sibdas Singha; Cho, Jae Whan

    2014-10-01

    A trilayered dry conducting polymer actuator was fabricated via application of a polypyrrole (PPy) coating on both sides of a solid polymer electrolyte film using vapor phase polymerization (VPP). The solid polymer electrolyte film was prepared by incorporation of different weight ratios of dodecylbenzene sulfonic acid sodium salt in poly(vinyl alcohol) (PVA) by solvent casting. The successful polymerization of PPy was confirmed by Fourier transform infrared spectroscopy; a uniform PPy coating on the solid polymer electrolyte film surface was also observed by scanning electron microscopy. The dry PVA/PPy actuator demonstrated good actuation behavior at a low applied voltage of 1-3 V. The actuator bending displacement was found to increase with an increase in the applied voltage. The VPP approach in this study provides a very effective method for achieving a uniform polymer coating in the fabrication of a dry conducting polymer actuator.

  3. The 2nd phase of the LEANDRE program: Water-vapor DIAL measurement

    NASA Technical Reports Server (NTRS)

    Quaglia, P.; Bruneau, D.; Pelon, J.

    1992-01-01

    As a follow-on of the backscattered lidar, a differential absorption lidar (LEANDRE 2) is now being developed as part of the LEANDRE program for airborne meteorological studies. The primary measurement objective of LEANDRE 2 is water vapor. Pressure and temperature measurements are aimed at a second stage. The goals are to obtain a horizontal resolution of a few hundred meters for a vertical resolution of less than a hundred meters, with an absolute accuracy of 10 percent for humidity measurement. As compatibility is an important feature between the 2 first phases of LEANDRE, most of the LEANDRE 1 sub-system will be used and adapted for LEANDRE 2. For example, detection electronics, central computer, detectors and telescope will be the same. However, important modifications have to be done on the laser source, and spectral control has to be added. Most of the work is thus devoted to those developments, and the status is presented here.

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

    NASA Astrophysics Data System (ADS)

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

    2012-02-01

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

  5. 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.

  6. Geometry of the vapor phase in explosive near-wall boiling-up

    NASA Astrophysics Data System (ADS)

    Pavlov, P. A.

    2016-07-01

    Methods for calculating the geometric characteristics of the vapor phase in explosive wall boiling-up processes on a metal wall are analyzed. A monotonic growth of superheat in the liquid above the equilibrium evaporation temperature is specified. We show that the choice of the model for bubble interaction has a profound influence on the geometric characteristics which define the value of the heat flux. Computer simulation was employed to obtain the dependence of dry area on time in two interaction models. We have found that, for a model with instantaneous bubble coalescence, the dry area can be evaluated by the Kolmogorov formula using a correction factor for the most probable triple interaction. An approximation of the distribution length of wetting line over the lifetime of wetting-line segments is obtained. The possibility of using the obtained data for calculation of rapid condensation is analyzed.

  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 (112¯0) a-orientation and a full width at half maximum of the (112¯0) 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. Vapor-phase staining of cyanoacrylate-fumed latent fingerprints using p-dimethylaminobenzaldehyde.

    PubMed

    Takatsu, Masahisa; Shimoda, Osamu; Teranishi, Hiroyoshi

    2012-03-01

    Contrasting or enhancing of cyanoacrylate ester-fumed latent fingerprints deposited on solvent-sensitive materials such as oil marker writings and rough surface materials such as unglazed earthenware is not easy by conventional dye solutions dipping or dye powder dusting. In this study, a new vapor-phase staining method using p-dimethylaminobenzaldehyde (DMAB) is proposed for staining such materials. DMAB has high volatility and selective absorbability to cyanoacrylate-fumed fingerprints, so that cyanoacrylate-treated samples can be easily stained by leaving them simply in a closed container along with DMAB crystals for 48-96 h at room temperature or in conjunction with the use of mild heating. The stained fingerprint could be excited by UV irradiation (365 nm), and the fluorescent fingerprint was photographed through a UV cut-off filter (420 nm). The new method achieved minimally destructive fluorescent staining for the solvent-sensitive samples and the rough surfaced samples.

  9. Vapor phase epitaxy of CdTe on sapphire substrates in dependence on the vapor-flow orientation

    NASA Astrophysics Data System (ADS)

    Muslimov, A. E.; Butashin, A. V.; Vlasov, V. P.; Kanevsky, V. M.

    2016-11-01

    The growth of cadmium telluride films on a structured (0001) sapphire surface oriented at an angle of 44° to the vapor-flow direction and normal to the steps formed along the 11overline 2 0 direction is studied. It is found that this geometry of the vapor source and a substrate (heated to a temperature of 300°C) provides the growth of single-crystal CdTe films if a step height on the substrate surface is more than 1 nm. The results are explained by the occurrence of a longitudinal component of the diffusion flux of CdTe molecules and atoms toward the steps from the inner side and their high density at the step edge from the outer side due to the presence of the Ehrlich-Schwoebel barrier, which ensures the efficient supply of material and minimum supersaturation necessary for the nucleation at the step edge and growth of oriented CdTe islands. The cadmium telluride films that are grown have the ( {110} )[ {1overline 1 0} ]CdTe| {( {0001} )} .[ {11overline 2 0} ]A{l_2}{O_3} orientation and a composition similar to stoichiometric CdTe.

  10. Referred Air Method 25E: Determination of a Vapor Phase Organic Concentration in Waste Samples

    EPA Pesticide Factsheets

    This method is applicable for determining the vapor pressure of waste. The headspace vapor of the sample is analyzed for carbon content by a headspace analyzer, which uses a flame ionization detector (FID).

  11. 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

  12. Vapor phase toxicity of marjoram oil compounds and their related monoterpenoids to Blattella germanica (Orthoptera: Blattellidae).

    PubMed

    Jang, Young-Su; Yang, Young-Cheol; Choi, Dal-Soon; Ahn, Young-Joon

    2005-10-05

    The toxicity of marjoram, Origanum majorana L., oil, 41 monoterpenoids, and 2 sesquiterpenoids against adult females of the German cockroach, Blattella germanica L., was examined using direct contact and vapor phase toxicity bioassays and compared with those of deltamethrin, dichlorvos, permethrin, and propoxur, four commonly used insecticides. In a filter-paper contact toxicity bioassay, the adulticidal activities of pulegone (0.06 mg/cm2), (+/-)-camphor (0.07 mg/cm2), and verbenone (0.07 mg/cm2) were comparable to that of permethrin (0.05 mg/cm2) but more pronounced than that of propoxur (0.18 mg/cm2), as judged by the 24-h LC50 values. These compounds were less effective than either deltamethrin (0.013 mg/cm2) or dichlorvos (0.007 mg/cm2). The toxicity of marjoram oil, thymol, alpha-terpineol, (-)-alpha-thujone, linalool, 1,8-cineole, (-)-camphor, and (+)-carvone, ranging from 0.08 to 0.18 mg/cm2, was higher than that of propoxur. In vapor phase toxicity tests, verbenone (11.48 mg/L air) was the most toxic compound followed by (-)-alpha-thujone (18.43 mg/L of air), thymol (18.76 mg/L of air), alpha-terpineol (21.89 mg/L of air), (+/-)-camphor (24.59 mg/L of air), linalool (26.20 mg/L of air), and marjoram oil (38.28 mg/L of air) on the basis of the 24-h LC50 values. Dichlorvos (0.07 mg/L of air) was the most potent fumigant. Structure-activity relationships indicate that structural characteristics, such as degrees of saturation and types of functional groups rather than types of carbon skeleton, and hydrophobicity and vapor pressure parameters appear to play a role in determining the monoterpenoid toxicities to adult B. germanica. Marjoram oil and the monoterpenoids described merit further study as potential fumigants or leads for the control of B. germanica.

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

    DTIC Science & Technology

    1990-04-01

    employed. The method relies on measurement of vapor concentrations of mixtures of solid samples with volatile organic compounds iv contained in gas-tight...of China, assisted with construction of the gravimetric adsorption apparatus employed in Section IV , calibration of the quartz spring, and the water...Constant ..... .............. .. 83 D. CONCLUSIONS .......... ....................... 85 IV TCE VAPOR SORPTION ONTO SOIL MINERALS AT III;! .. 87 VAPOR

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

    DOEpatents

    Kunnmann, Walter; Larese, John Z.

    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.

  15. 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),...

  16. 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...

  17. Vapor-phase catalytic oxidesulfurization (ODS) of organosulfur compounds over supported metal oxide catalysts

    NASA Astrophysics Data System (ADS)

    Choi, Sukwon

    Sulfur in transportation fuels remains a leading source of SOx emissions from vehicle engines and is a major source of air pollution. The very low levels of sulfur globally mandated for transportation fuels in the near future cannot be achieved by current practices of hydrodesulfurization (HDS) for sulfur removal, which operate under severe conditions (high T, P) and use valuable H2. Novel vapor-phase catalytic oxidesulfurization (ODS) processes of selectively oxidizing various organosulfur compounds (carbonyl sulfide, carbon disulfide, methanethiol, dimethyl sulfide (DMS), dimethyl disulfide (DMDS), thiophene, 2,5-dimenthylthiophene) typically found in various industrial streams (e.g., petroleum refining, pulp and paper) into valuable chemical intermediates (H 2CO, CO, H2, maleic anhydride and concentrated SO2) has been extensively studied. This research has primarily focused on establishing the fundamental kinetics and mechanisms of these selective oxidation reactions over well-defined supported metal oxide catalysts. The selective oxidation reactions of COS + O2 → CO + SO2; 2CS2 + 5O2 → 2CO + 4SO2; CH3SH + 2O 2 → H2CO + SO2 + H2O; C4 H4S + 3O2 → C4H2O 3 + H2O + SO2; were studied. Raman spectroscopy revealed that the supported metal oxide phases were 100% dispersed on the oxide substrate. All the catalysts were highly active and selective for the oxidesulfurization of carbonyl sulfide, carbon disulfide, methanethiol, and thiophene between 290--330°C, 230--270°C, 350--400°C, and 250--400°C, respectively and did not deactivate. The TOFs (turnover frequency, normalized activity per active catalytic site) for all ODS reactions over supported vanadia catalysts, only containing molecularly dispersed surface vanadia species, varied within one order of magnitude and revealed the V-O-Support bridging bond was involved in the critical rate-determining kinetic steps. The surface reaction mechanism for each reaction was revealed by in situ IR (infrared) and

  18. InGaAsP Solar Cells Grown by Hydride Vapor Phase Epitaxy

    SciTech Connect

    Jain, Nikhil; Simon, John; Schulte, Kevin L.; Dippo, Patricia; Young, Michelle; Young, David L.; Ptak, Aaron J.

    2016-11-21

    Hydride vapor phase epitaxy (HVPE) has recently reemerged as a low-cost, high-throughput alternative to metalorganic chemical vapor deposition (MOCVD) for the growth of high-efficiency III-V solar cells. Quaternary InGaAsP solar cells in the bandgap range of ~1.7-1.8 eV are promising top-cell candidates for integration in Ill-V/Si tandem cells with projected one-sun efficiencies exceeding 30%. In this work, we report on the development of lattice-matched InGaAsP solar cells grown on GaAs substrates via HVPE at very high growth rates of ~0.7 um/min. We demonstrate prototype 1.7 eV InGaAsP solar cells with an open-circuit voltage of 1.11 V. The short-circuit current is limited by the lack of a window layer in these early stage devices. The photo response of 1.7 InGaAsP solar cell with ~1.1 um thick base layer is found to be nearly insensitive to variation in p-type base doping concentration in the range from Na - 4x1016 to - 1x1017 cm-3, indicating an effective carrier collection length on the order of - 1.1 um or higher in our devices. These initial InGaAsP cell results are encouraging and highlight the viability of HVPE to produce mixed arsenide-phosphide solar cells grown lattice-matched on GaAs.

  19. 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

  20. Fabrication of polyimide shells by vapor phase deposition for use as ICF targets

    SciTech Connect

    Alfonso, E.L.; Tsai, F.Y.; Chen, S.H.; Gram, R.Q.; Harding, D.R.

    1999-03-01

    Hollow polyimide shells, for use as ICF targets, were fabricated by co-depositing monomer precursors from the vapor phase onto bounced spherical mandrels. The process involved two stages: first, the deposited monomers (pyromellitic dianhydride and 4,4{prime}-oxydianiline) reacted on the mandrel surface to form polyamic acid; second, the mandrel was heated to 300 C to imidize the polyamic acid and to decompose the mandrel. During this latter process the decomposed mandrel diffused through the thermally stable coating, leaving a polyimide shell. Depositions were performed under low ({approximately}10{sup {minus}3} Torr) and high ({approximately}10{sup {minus}6} Torr) vacuum. Also, flat witness films of polyimide deposited on Si wafers and NaCl allowed the mechanical properties and chemical composition of the film during the heating cycle to be measured. Polyimide shells with diameters ranging from 700 to 950 {micro}m and wall thicknesses ranging from 2 to 13 {micro}m were produced. The shell`s sphericity was greater than 99%. Burst and buckle pressure tests on these shells yielded the estimated mechanical strength properties. The elastic modulus and tensile strength were {approximately}15 GPa and {approximately}300 MPa, respectively. The permeability of D{sub 2} through polyamic acid at 25 C was 7.4 {times} 10{sup {minus}17} mol{center_dot}m/m{sup 2}{center_dot}Pa{center_dot}s and increased to 6.4 {times} 10{sup {minus}16} mol{center_dot}m/m{sup 2}{center_dot}Pa{center_dot}s at 25 C upon curing the shell to 150 C. The permeability of D{sub 2} at 25 C through vapor-deposited polyimide flat films was measured to be 240 times greater than through the as-deposited polyamic acid, and about 7 times greater than through commercially available solution-cast Kapton.

  1. Antibacterial effects of allspice, garlic, and oregano essential oils in tomato films determined by overlay and vapor-phase methods.

    PubMed

    Du, W-X; Olsen, C W; Avena-Bustillos, R J; McHugh, T H; Levin, C E; Mandrell, R; Friedman, Mendel

    2009-09-01

    Physical properties as well as antimicrobial activities against Escherichia coli O157:H7, Salmonella enterica, and Listeria monocytogenes of allspice, garlic, and oregano essential oils (EOs) in tomato puree film-forming solutions (TPFFS) formulated into edible films at 0.5% to 3% (w/w) concentrations were investigated in this study. Antimicrobial activities were determined by 2 independent methods: overlay of the film on top of the bacteria and vapor-phase diffusion of the antimicrobial from the film to the bacteria. The results indicate that the antimicrobial activities against the 3 pathogens were in the following order: oregano oil > allspice oil > garlic oil. Listeria monocytogenes was less resistant to EO vapors, while E. coli O157:H7 was more resistant to EOs as determined by both overlay and vapor-phase diffusion tests. The presence of plant EO antimicrobials reduced the viscosity of TPFFS at the higher shear rates, but did not affect water vapor permeability of films. EOs increased elongation and darkened the color of films. The results of the present study show that the 3 plant-derived EOs can be used to prepare tomato-based antimicrobial edible films with good physical properties for food applications by both direct contact and indirectly by vapors emanating from the films.

  2. Growth behavior of GaSb by metal organic vapor-phase epitaxy

    NASA Astrophysics Data System (ADS)

    Rathi, Manish K.; Hawkins, Brian E.; Kuech, Thomas F.

    2006-11-01

    The growth mechanisms of GaSb in a metal-organic vapor-phase epitaxy (MOVPE) system were studied for both trimethyl gallium (TMG)/trimethyl antimony (TMSb) and triethyl gallium (TEG)/TMSb growth chemistries. The effect of growth temperature and precursor mole fractions on GaSb growth rate was determined experimentally. Numerical analysis of the reactor and growth process was described in a combined chemical-thermal-fluid flow model. A Langmuir-Hinshelwood-type mechanism involving a surface reaction between adsorbed monomethyl gallium (MMG) and adsorbed monomethyl antimony (MMSb) or adsorbed Ga and adsorbed MMSb was proposed for the growth of GaSb by MOVPE using TMG or TEG and TMSb chemistries, respectively. The chemical model for TMG/TMSb chemistry included bounds on the surface chemistry derived for the range of V/III precursor ratio which were observed to lead to a second phase, i.e., elemental Ga or Sb, formation. Two growth regimes were observed for TMG/TMSb chemistry: above 575 °C the growth rate was mass transfer controlled whereas for lower temperatures it is kinetically limited. No such temperature dependence has been found for the TEG/TMSb chemistry over all experimental employed ranges of growth parameters.

  3. INTERNATIONAL CONFERENCE ON SEMICONDUCTOR INJECTION LASERS SELCO-87: Metal-organic vapor phase epitaxy of (GaAl)As for 0.85-μm laser diodes

    NASA Astrophysics Data System (ADS)

    Jacobs, K.; Bugge, F.; Butzke, G.; Lehmann, L.; Schimko, R.

    1988-11-01

    Metal-organic vapor phase epitaxy was used to grow stripe heterolaser diodes that were hitherto fabricated by liquid phase epitaxy. The main relationships between the growth parameters (partial input pressures, temperatures) and the properties of materials (thicknesses, solid-solution compositions, carrier densities) were investigated. The results were in full agreement with the mechanism of growth controlled by a vapor-phase diffusion. The results achieved routinely in the growth of GaAs are reported. It is shown that double heterostructure laser diodes fabricated by metal-organic vapor phase epitaxy compete favorably with those grown so far by liquid phase epitaxy, including their degradation and reliability.

  4. Vapor phase growth and photoluminescence of oriented-attachment Zn2GeO4 nanorods array

    NASA Astrophysics Data System (ADS)

    Tang, Haiping; Zhu, Xingda; He, Haiping

    2016-10-01

    We carry out one-step vapor phase growth of high quality Zn2GeO4 nanorods array to provide insights into the growth mechanism of such ternary oxide nanostructures. The morphology and microstructure of these nanorods are investigated carefully. Under certain conditions, the nanorods follow the oriented-attachment growth which is unusual in vapor-based growth. Each nanorod consists of many nanocrystals aligned along the [110] direction. The nanorods show strong deep ultraviolet absorption around 260 nm and broad longlife green luminescence around 490 nm.

  5. 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

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

    NASA Astrophysics Data System (ADS)

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

    2004-09-01

    Soil vapor extraction (SVE) is commonly used to remediate nonaqueous phase liquids (NAPLs) from the vadose zone. This paper aims to determine the effect of grain size heterogeneity on the removal of NAPL in porous media during SVE. Magnetic resonance imaging (MRI) was used to observe and quantify the amount and location of NAPL in flow-through columns filled with silica gel grains. MRI is unique because it is nondestructive, allowing three-dimensional images to be taken of the phases as a function of space and time. Columns were packed with silica gel in three ways: coarse grains (250-550 μm) only, fine grains (32-63 μm) only, and a core of fine grains surrounded by a shell of coarse grains. Columns saturated with water were drained under a constant suction head, contaminated with decane, and then drained to different decane saturations. Each column was then continuously purged with water-saturated nitrogen gas and images were taken intermittently. Results showed that at residual saturation, a sharp volatilization front moved through the columns filled with either coarse-grain or fine-grain silica gel. In the heterogeneous columns, the volatilization front in the core lagged just behind the shell because gas flow was greater through the shell and decane in the core diffused outward to the shell. When decane saturation in the core was above residual saturation, decane volatilization occurred near the inlet, the relative decane saturation throughout the core dropped uniformly, and decane in the core flowed in the liquid phase to the shell to replenish volatilized decane. These results indicate that NAPL trapped in low-permeability zones can flow to replenish areas where NAPL is lost due to SVE. However, when residual NAPL saturation is reached, NAPL flow no longer occurs and diffusion limits removal from low-permeability zones.

  7. Vapor Phase Dehydration of Glycerol to Acrolein Over SBA-15 Supported Vanadium Substituted Phosphomolybdic Acid Catalyst.

    PubMed

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

    2015-07-01

    Vapor phase dehydration of glycerol to acrolein was investigated over heteropolyacid (HPA) catalysts containing vanadium substituted phosphomolybdic acid (H4PMo11VO40) supported on mesoporous SBA-15. A series of HPA catalysts with HPA loadings varying from 10-50 wt% were prepared by impregnation method on SBA-15 support. The catalysts were characterized by X-ray diffraction, Raman spectroscopy, Fourier Transform infrared spectroscopy, temperature-programmed desorption of NH3, pyridine adsorbed FT-IR spectroscopy, scanning electron microscopy, pore size distribution and specific surface area measurements. The nature of acidic sites was examined by pyridine adsorbed FT-IR spectroscopy. XRD results suggest that the active phase containing HPA was highly dispersed at lower loadings on the support. FT-IR and Raman spectra results confirm that the presence of primary Keggin ion structure of HPA on the support and it was not affected during the preparation of catalysts. Pore size distribution results reveal that all the samples show unimodel pore size distribution with well depicted mesoporous structure. NH3-TPD results suggest that the acidity of catalysts increased with increase of HPA loading. The findings of acidity measurements by FT-IR spectra of pyridine adsorption reveals that the catalysts consist both the Brønsted and Lewis acidic sites and the amount of Brønsted acidic sites are increasing with HPA loading. SBA-15 supported vanadium substituted phosphomolybdic acid catalysts are found to be highly active during the dehydration reaction and exhibited 100% conversion of glycerol (10 wt% of glycerol) and the acrolein selectivity was appreciably changed with HPA active phase loading. The catalytic functionalities during glycerol dehydration are well correlated with surface acidity of the catalysts.

  8. [Summary of the existing knowledge about electronic cigarettes].

    PubMed

    Cselkó, Zsuzsa; Pénzes, Melinda

    2016-06-19

    The decreasing proportion of smokers due to smoking restrictions have led producers to invent and disseminate electronic cigarettes (e-cigarettes) worldwide as a new form of nicotine enjoyment. This review summarizes the existing knowledge about e-cigarettes based on publications of PubMed, and on reviews and research data published by national and international scientific institutions. Present knowledge about the composition of e-cigarettes confirms that they are harmful products since their vapor is equally detrimental to the health of users and bystanders. Their benefits in smoking cessation still have not been justified by adequate scientific evidence, however, it has been proven that e-cigarettes uphold nicotine addiction and may increase the risk of starting conventional cigarette use by youth. In order to ensure the results of tobacco control policy and to assist smoking cessation, the same regulations are to be applied to e-cigarettes as to conventional tobacco products.

  9. Bubbles in liquids with phase transition—part 2: on balance laws for mixture theories of disperse vapor bubbles in liquid with phase change

    NASA Astrophysics Data System (ADS)

    Dreyer, Wolfgang; Hantke, Maren; Warnecke, Gerald

    2014-07-01

    We study averaging methods for the derivation of mixture equations for disperse vapor bubbles in liquids. The carrier liquid is modeled as a continuum, whereas simplified assumptions are made for the disperse bubble phase. An approach due to Petrov and Voinov is extended to derive mixture equations for the case that there is a phase transition between the carrier liquid and the vapor bubbles in water. We end up with a system of balance laws for a multi-phase mixture, which is completely in divergence form. Additional non-differential source terms describe the exchange of mass, momentum and energy between the phases. The sources depend explicitly on evolution laws for the total mass, the radius and the temperature of single bubbles. These evolution laws are derived in a prior article (Dreyer et al. in Cont Mech Thermodyn. doi:10.1007/s00161-0225-6, 2011) and are used to close the system. Finally, numerical examples are presented.

  10. 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.

  11. 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 DST’s is given at the end of this report.

  12. Enhancing the adsorption of vapor-phase mercury chloride with an innovative composite sulfur-impregnated activated carbon.

    PubMed

    Ie, Iau-Ren; Chen, Wei-Chin; Yuan, Chung-Shin; Hung, Chung-Hsuang; Lin, Yuan-Chung; Tsai, Hsieh-Hung; Jen, Yi-Shiu

    2012-05-30

    Mercury chloride (HgCl(2)) is the major mercury derivate emitted from municipal solid waste incinerators, which has high risk to the environment and human health. This study investigated the adsorption of vapor-phase HgCl(2) with an innovative composite sulfurized activated carbon (AC), which was derived from the pyrolysis, activation, and sulfurization of waste tires. The composite sulfur-impregnation process impregnated activated carbon with aqueous-phase sodium sulfide (Na(2)S) and followed with vapor-phase elemental sulfur (S(0)). Thermogravimetric analysis (TGA) was applied to investigate the adsorptive capacity of vapor-phase HgCl(2) using the composite sulfurized AC. The operating parameters included the types of composite sulfurized AC, the adsorption temperature, and the influent HgCl(2) concentration. Experimental results indicated that the sulfur-impregnation process could increase the sulfur content of the sulfurized AC, but decreased its specific surface area. This study further revealed that the composite sulfurized AC impregnated with aqueous-phase Na(2)S and followed with vapor-phase S(0) (Na(2)S+S(0) AC) had much higher saturated adsorptive capacity of HgCl(2) than AC impregnated in the reverse sequence (S(0)+Na(2)S AC). A maximum saturated adsorptive capacity of HgCl(2) up to 5236 μg-HgCl(2)/g-C was observed for the composite Na(2)S+S(0) AC, which was approximately 2.00 and 3.17 times higher than those for the single Na(2)S and S(0) ACs, respectively.

  13. 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.

  14. 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.

  15. Flavoring Compounds Dominate Toxic Aldehyde Production during E-Cigarette Vaping.

    PubMed

    Khlystov, Andrey; Samburova, Vera

    2016-12-06

    The growing popularity of electronic cigarettes (e-cigarettes) raises concerns about the possibility of adverse health effects to primary users and people exposed to e-cigarette vapors. E-Cigarettes offer a very wide variety of flavors, which is one of the main factors that attract new, especially young, users. How flavoring compounds in e-cigarette liquids affect the chemical composition and toxicity of e-cigarette vapors is practically unknown. Although e-cigarettes are marketed as safer alternatives to traditional cigarettes, several studies have demonstrated formation of toxic aldehydes in e-cigarette vapors during vaping. So far, aldehyde formation has been attributed to thermal decomposition of the main components of e-cigarette e-liquids (propylene glycol and glycerol), while the role of flavoring compounds has been ignored. In this study, we have measured several toxic aldehydes produced by three popular brands of e-cigarettes with flavored and unflavored e-liquids. We show that, within the tested e-cigarette brands, thermal decomposition of flavoring compounds dominates formation of aldehydes during vaping, producing levels that exceed occupational safety standards. Production of aldehydes was found to be exponentially dependent on concentration of flavoring compounds. These findings stress the need for a further, thorough investigation of the effect of flavoring compounds on the toxicity of e-cigarettes.

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

    NASA Astrophysics Data System (ADS)

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

    2009-06-01

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

  17. 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.

  18. Good Biocompatibility and Sintering Properties of Zirconia Nanoparticles Synthesized via Vapor-phase Hydrolysis

    PubMed Central

    Wang, Jigang; Yin, Wenyan; He, Xiao; Wang, Qiang; Guo, Ming; Chen, Shaowei

    2016-01-01

    ZrO2 nanoparticles were synthesized by a vapor-phase hydrolysis process, and characterized in terms of crystalline structures, hardness and microstructures by X-ray diffraction, Vickers hardness test method, and atomic force microscopy (AFM) measurements. Moreover, in vitro cytotoxicity evaluation and hemolysis assay showed that the nanoparticles possessed good biocompatibility. Hardness investigations and AFM measurements indicated that both the sintering temperature and compression force played an important role in determining the physical behaviors (hardness, roughness and density) of flakes of the ZrO2 nanoparticles. When ZrO2 nanoparticles synthesized at 500 °C were pressed into flakes under 6 MPa and sintered at 1400 °C, the resulting flakes exhibited an optimal combination of hardness (534.58 gf·mm−2), roughness (0.07 μm) and density (4.41 g·cm−3). As the Vickers hardness value of human bones is of 315~535 gf·mm−2 and the density of adult femuris about 1.3~1.7 g·cm−3, the experimental results showed that the ZrO2 flakes were comparable to human bones with a higher density. As a result, the synthesized ZrO2 NPs may be useful for biomedical applications, especially for bone repair and replacement in future. PMID:27725744

  19. Bi-modal nanoheteroepitaxy of GaAs on Si by metal organic vapor phase epitaxy.

    PubMed

    Prieto, Ivan; Kozak, Roksolana; Skibitzki, Oliver; Rossell, Marta D; Zaumseil, Peter; Capellini, Giovanni; Gini, Emilio; Kunze, Karsten; Rojas Dasilva, Yadira Arroyo; Erni, Rolf; Schroeder, Thomas; Känel, Hans von

    2017-03-01

    Nano-heteroepitaxial growth of GaAs on Si(001) by metal organic vapor phase epitaxy was investigated to study emerging materials phenomena on the nano-scale of III-V/Si interaction. Arrays of Si nano-tips (NTs) embedded in a SiO2 matrix were used as substrates. The NTs had top Si openings of 50-90 nm serving as seeds for the selective growth of GaAs nano-crystals (NCs). The structural and morphological properties were investigated by high resolution scanning electron microscopy, atomic force microscopy, electron backscatter diffraction, x-ray diffraction, and high resolution scanning transmission electron microscopy. The GaAs growth led to epitaxial NCs featuring a bi-modal distribution of size and morphology. NCs of small size exhibited high structural quality and well-defined {111}-{100} faceting. Larger clusters had less regular shapes and contained twins. The present work shows that the growth of high quality GaAs NCs on Si NTs is feasible and can provide an alternate way to the integration of compound semiconductors with Si micro- and opto-electronics technology.

  20. Electron spin resonance study of GaAs:Er,O grown by organometallic vapor phase epitaxy

    NASA Astrophysics Data System (ADS)

    Yoshida, Makoto; Hiraka, Kensaku; Ohta, Hitoshi; Fujiwara, Yasufumi; Koizumi, Atsushi; Takeda, Yoshikazu

    2004-10-01

    Electron spin resonance (ESR) measurements of GaAs:Er,O grown by organometallic vapor phase epitaxy have been performed at 9.49GHz from 4.5to13K. Several anisotropic ESR signals (A, B, C, and D) are observed, which is consistent with the previous reports. We reexamined the angular dependence and temperature dependence of the signals in detail. Our ESR results indicate that the direction of alignment of two oxygen atoms or two arsenic atoms for an Er-2O center deviates from the ⟨110⟩ direction in various ways, resulting in the various Er-2O centers. Our ESR results also indicate that the paramagnetic states of the Er centers in GaAs change to a singletlike nonmagnetic state below 8K. The ESR measurements under illumination have been performed to investigate the effect of photoexcitation of the host. This result indicates that the energy transfer efficiency from the host to the B center is especially large. We found that the luminescent Er-2O center B and another Er-2O center C considerably differ in the coupling with the lattice.

  1. 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.

  2. Good Biocompatibility and Sintering Properties of Zirconia Nanoparticles Synthesized via Vapor-phase Hydrolysis

    NASA Astrophysics Data System (ADS)

    Wang, Jigang; Yin, Wenyan; He, Xiao; Wang, Qiang; Guo, Ming; Chen, Shaowei

    2016-10-01

    ZrO2 nanoparticles were synthesized by a vapor-phase hydrolysis process, and characterized in terms of crystalline structures, hardness and microstructures by X-ray diffraction, Vickers hardness test method, and atomic force microscopy (AFM) measurements. Moreover, in vitro cytotoxicity evaluation and hemolysis assay showed that the nanoparticles possessed good biocompatibility. Hardness investigations and AFM measurements indicated that both the sintering temperature and compression force played an important role in determining the physical behaviors (hardness, roughness and density) of flakes of the ZrO2 nanoparticles. When ZrO2 nanoparticles synthesized at 500 °C were pressed into flakes under 6 MPa and sintered at 1400 °C, the resulting flakes exhibited an optimal combination of hardness (534.58 gf·mm‑2), roughness (0.07 μm) and density (4.41 g·cm‑3). As the Vickers hardness value of human bones is of 315~535 gf·mm‑2 and the density of adult femuris about 1.3~1.7 g·cm‑3, the experimental results showed that the ZrO2 flakes were comparable to human bones with a higher density. As a result, the synthesized ZrO2 NPs may be useful for biomedical applications, especially for bone repair and replacement in future.

  3. 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.

  4. Hydroxylation of phenol over MeAPO molecular sieves synthesized by vapor phase transport

    NASA Astrophysics Data System (ADS)

    Shao, Hui; Chen, Jingjing; Chen, Xia; Leng, Yixin; Zhong, Jing

    2016-07-01

    In this study, MeAPO-25 (Me = Fe, Cu, Mn) molecular sieves were first synthesized by a vapor phase transport method using tetramethyl guanidine as the template and applied to hydroxylation of phenol. The zeolites were characterized by XRD, SEM, FT-IR, and DR UV-Vis. As a result, MeAPO-21 and MeAPO-15 were synthesized by changing the Me/Al ratio. UV-Visible diffuse reflectance study suggested incorporation of heteroatoms into the framework and FT-IR study also supported these data. Effects of heteroatoms, contents of Me in MeAPO-25, reaction temperature, phenol/H2O2 mole ratios, reaction time and concentration of catalyst on the conversion of phenol, as well as on the selectivity were studied. FeAPO-25 exhibited a high catalytic activity at the mole ratio of FeO and Al2O3 equal to 0.1 in the synthesis gel, giving the phenol conversion of 88.75% and diphenols selectivity of 66.23% at 60°C within 3 h [ n(phenol)/ n(H2O2) = 0.75, m(FeAPO-25)/ m(phenol) = 7.5%]. Experimental results indicated that the FeAPO-25 molecular sieve was a fairly promising candidate for the application in hydroxylation of phenol.

  5. Optical waveguide loss minimized into gallium nitride based structures grown by metal organic vapor phase epitaxy

    NASA Astrophysics Data System (ADS)

    Stolz, A.; Cho, E.; Dogheche, E.; Androussi, Y.; Troadec, D.; Pavlidis, D.; Decoster, D.

    2011-04-01

    The waveguide properties are reported for wide bandgap gallium nitride (GaN) structures grown by metal organic vapor phase epitaxy on sapphire using a AlN/GaN short period-superlattice (SPS) buffer layer system. A detailed optical characterization of GaN structures has been performed using the prism coupling technique in order to evaluate its properties and, in particular, the refractive index dispersion and the propagation loss. In order to identify the structural defects in the samples, we performed transmission electron microscopy analysis. The results suggest that AlN/GaN SPS plays a role in acting as a barrier to the propagation of threading dislocations in the active GaN epilayer; above this defective region, the dislocations density is remarkably reduced. The waveguide losses were reduced to a value around 0.65dB/cm at 1.55 μm, corresponding to the best value reported so far for a GaN-based waveguide.

  6. 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.

  7. Bi-modal nanoheteroepitaxy of GaAs on Si by metal organic vapor phase epitaxy

    NASA Astrophysics Data System (ADS)

    Prieto, Ivan; Kozak, Roksolana; Skibitzki, Oliver; Rossell, Marta D.; Zaumseil, Peter; Capellini, Giovanni; Gini, Emilio; Kunze, Karsten; Arroyo Rojas Dasilva, Yadira; Erni, Rolf; Schroeder, Thomas; von Känel, Hans

    2017-03-01

    Nano-heteroepitaxial growth of GaAs on Si(001) by metal organic vapor phase epitaxy was investigated to study emerging materials phenomena on the nano-scale of III–V/Si interaction. Arrays of Si nano-tips (NTs) embedded in a SiO2 matrix were used as substrates. The NTs had top Si openings of 50–90 nm serving as seeds for the selective growth of GaAs nano-crystals (NCs). The structural and morphological properties were investigated by high resolution scanning electron microscopy, atomic force microscopy, electron backscatter diffraction, x-ray diffraction, and high resolution scanning transmission electron microscopy. The GaAs growth led to epitaxial NCs featuring a bi-modal distribution of size and morphology. NCs of small size exhibited high structural quality and well-defined {111}–{100} faceting. Larger clusters had less regular shapes and contained twins. The present work shows that the growth of high quality GaAs NCs on Si NTs is feasible and can provide an alternate way to the integration of compound semiconductors with Si micro- and opto-electronics technology.

  8. 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 Shari; Hensley, Alyssa J.; 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.

  9. 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.

  10. 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.

  11. 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.

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

    SciTech Connect

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

    2015-12-14

    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 Ga{sub x}In{sub 1−x}P (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.

  13. 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 (2–5) × 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.

  14. Vapor phase epitaxy growth of CdTe epilayers for RT x-ray detectors

    NASA Astrophysics Data System (ADS)

    Lovergine, Nico; Mancini, A. M.; Prete, P.; Cola, Adriano; Tapfer, Leander

    2000-11-01

    We report on the growth of thick CdTe layers on ZnTe/(100) GaAs hybrid substrates by the novel H2 transport vapor phase epitaxy (H2T-VPE) method. High crystalline quality (100)-oriented CdTe single crystal epilayers can be fabricated under atmospheric pressure and at growth temperatures (TD) in the 600 - 800 degree Celsius interval. Double crystal X-ray diffraction measurements performed on epilayers thicker than 30 micrometer show CdTe (400) peaks with FWHM < 59 arcsec. Samples grown under optimized conditions exhibit mirror-like surfaces. Nominally undoped epilayers grown < 650 degrees Celsius are p-type and low resistive, but they turn n-type above 650 degrees Celsius, as a result of donor (likely Ga) diffusion from the substrate. RT resistivities ((rho) ) approximately 106 (Omega) (DOT)cm are obtained for 675 degrees Celsius < TD < 700 degrees Celsius, but (rho) decreases for higher temperatures and thinner samples. Layers grown under these conditions show RT electron concentrations in the 1014 - 1011 cm-3 range. The detection capability of H2T-VPE grown CdTe is demonstrated by time- of-flight measurements performed at RT on Au/n-CdTe/n+- GaAs diode structures under reverse bias conditions. The present results show the potentials of H2T-VPE for the growth of detector-grade CdTe.

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

    SciTech Connect

    Duc, Tran Thien; Pozina, Galia; Son, Nguyen Tien; Janzén, 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.

  16. Design of gas inlets for the growth of gallium nitride by metalorganic vapor phase epitaxy

    NASA Astrophysics Data System (ADS)

    Theodoropoulos, C.; Mountziaris, T. J.; Moffat, H. K.; Han, J.

    2000-07-01

    The problem of gas inlet design for metalorganic vapor phase epitaxy (MOVPE) of group III nitrides from metal alkyls and ammonia is addressed. The focus is on GaN growth from trimethyl-gallium and ammonia. In traditional reactors with well-mixed inlet streams, parasitic gas-phase reactions between the two precursors may lead to the formation of stable adducts that can condense on cool inlet walls, thus reducing the film growth efficiency. Such reactions may also lead to the formation of particulates through gas-phase condensation reactions (e.g. during AlN growth). A fundamentally-based model was developed to describe the MOVPE of GaN and was used to study the effect of inlet design and reactor operating conditions on film thickness uniformity in vertical stagnation-flow and rotating-disk reactors. The model includes a description of gas-phase kinetics and a simple gas-surface reaction mechanism. The kinetic model was coupled to a two-dimensional transport model describing flow, heat and mass transfer in a vertical MOVPE reactor. Predictions of growth rate compare well to experimental observations from a vertical rotating-disk reactor, without any adjustable parameters. The model was also used to study the distribution of gaseous species in the reactor and their role in film growth. Finite element simulations using a massively parallel computer code (MPSalsa) indicate that the species responsible for film growth are Ga-alkyls and not their adducts with ammonia. Sensitivity analysis was also performed to assess the relative importance of each reaction in determining the growth rate. The model was subsequently employed in the design of axisymmetric, multi-aperture gas inlets feeding precursors into the reactor in an alternating (not well-mixed) fashion. Simulations were performed to study the effect of key design parameters, such as inlet velocities, susceptor rotating speed, inlet to susceptor distance as well as the number and distribution of inlets, on GaN film

  17. 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

  18. 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.

  19. Study of Pulse Laser Assisted Metalorganic Vapor Phase Epitaxy of InGaN with Large Indium Mole Fraction

    NASA Astrophysics Data System (ADS)

    Kangawa, Yoshihiro; Kawaguchi, Norihito; Hida, Ken-nosuke; Kumagai, Yoshinao; Koukitu, Akinori

    2004-08-01

    The indium composition of the InGaN film increases with decreasing growth temperature; however, the crystalline quality of the film is poor when it is grown at low temperatures. To form a high-quality InGaN film with a large indium mole fraction, Nd: YAG pulse laser assisted metalorganic vapor phase epitaxy (MOVPE) was carried out at low temperatures. The results suggest that film quality can be improved by pulse laser irradiation on the surface of the film.

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

    SciTech Connect

    Hou, Hong Q.; Coltrin, Michael E.; Choquette, Kent D.

    2001-01-01

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

  1. 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.

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

    PubMed

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

    2013-05-01

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

  3. Matrix Isolation Studies of Carbonic Acid—The Vapor Phase above the β-Polymorph

    PubMed Central

    2013-01-01

    Twenty years ago two different polymorphs of carbonic acid, α- and β-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 α-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 β-polymorph. Unlike α-H2CO3, β-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 β-H2CO3 adds a new aspect to the chemistry of carbonic acid in astrophysical environments, especially because there is a direct way of β-H2CO3 formation in space, but none for α-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 α-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 β-H2CO3, whereas they are not at the sublimation temperature of 210 K for α-H2CO3. PMID:23631554

  4. 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

  5. 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.

  6. Recent progress in GaInAsSb thermophotovoltaics grown by organometallic vapor phase epitaxy

    SciTech Connect

    Wang, C.A.; Choi, H.K.; Oakley, D.C.; Charache, G.W.

    1998-06-01

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

  7. 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

  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. Carbon monoxide kinetics following simulated cigarette smoking

    SciTech Connect

    Karnik, A.S.; Coin, E.J.

    1980-05-01

    Carbon monoxide kinetics were measured in the blood (% carboxyhemoglobin) and alveolar phase (ppM carbon monoxide) after simulated cigarette smoking. Cigarette smoking was siumlated using the same amount of carbon monoxide that 2R1F cigarettes manufactured by the Tobacco Research Institute would contain. Ten boluses of air containing carbon monoxide equivalent to smoking one cigarette were inhaled by six healthy nonsmoker volunteers. Carbon monoxide in the air phase was measured by an Ecolyzer and carboxyhemoglobin was measured by a CO-Oximeter. The mean rise in alveolar carbon monoxide immediately and 20 min after inhaling the last bolus was 3.3 and 3.1 ppM, respectively (p<.005). The mean rise in carboxyhemoglobin immediately and 20 min after inhalation of the last bolus was 0.8 and 0.5% respectively (P<.005). The changes in carboxyhemoglobin were found to be similar to changes that occur when one cigarette is actually smoked.

  10. Dynamics of chemical vapor sensing with MoS2 using 1T/2H phase contacts/channel

    NASA Astrophysics Data System (ADS)

    Friedman, Adam L.; Perkins, F. Keith; Hanbicki, Aubrey T.; Culbertson, James C.; Campbell, Paul M.

    2016-06-01

    Ultra-thin transition metal dichalcogenides (TMDs) films show remarkable potential for use in chemical vapor sensing devices. Electronic devices fabricated from TMD films are inexpensive, inherently flexible, low-power, amenable to industrial-scale processing because of emergent growth techniques, and have shown high sensitivity and selectivity to electron donor analyte molecules important for explosives and nerve gas detection. However, for devices reported to date, the conductance response to chemical vapors is dominated by Schottky contacts, to the detriment of the sensitivity, selectivity, recovery, and obscuring their intrinsic behavior. Here, we use contact engineering to transition the contacts in a MoS2 FET-based chemical vapor sensor to the 1T conducting phase, while leaving the channel in the 2H semiconducting state, and thus providing Ohmic contacts to the film. We demonstrate that the resultant sensors have much improved electrical characteristics, are more selective, and recover fully after chemical vapor exposure--all major enhancements to previously MoS2 sensor devices. We identify labile nitrogen-containing electron donors as the primary species that generate a response in MoS2, and we study the dynamics of the sensing reactions, identifying two possible qualitative models for the chemical sensing reaction.

  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. A Method to Use Modis Water Vapor Products For Correction of Atmospheric-Induced Phase in Interferogram

    NASA Astrophysics Data System (ADS)

    Keeratikasikorn, Chaiyapon; Trisirisatayawong, Itthi

    2011-01-01

    DInSAR is a major space-geodetic technique widely used in the study of earth surface deformation. A major source of phase errors in DInSAR technique is heterogeneous phase delay caused mainly by variation of water vapors in troposphere, which is a factor limiting applications of DInSAR mainly to arid areas. This paper presents study results of three methods to correct atmospheric phase errors in DInSAR interferograms formed by TerraSAR-X images. The first method is the use of wet delay derived directly from MODIS precipitable water vapor product. The second method employs ground-based meteorological data to calibrate MODIS PWV before computing phase delays. The third method improves the second method by estimating the expected MODIS PWV value at the time of the TerraSAR-X image acquisitions which over the Bangkok test area is 5 hour earlier than that of MODIS. The time-shifted linear fit model along with the IDW interpolation is used to estimate more realistic phase delays over entire imaging area. From the study of this tropical test area, this time-corrected method provides best results while the second method also achieves a significantly better result than those obtained from direct use of MODIS PWV data.

  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. 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

    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.

  15. Evaluation of the Antibacterial Potential of Liquid and Vapor Phase Phenolic Essential Oil Compounds against Oral Microorganisms.

    PubMed

    Wang, Tong-Hong; Hsia, Shih-Min; Wu, Chi-Hao; Ko, Shun-Yao; Chen, Michael Yuanchien; Shih, Yin-Hua; Shieh, Tzong-Ming; Chuang, Li-Chuan; Wu, Ching-Yi

    The aim of the present study was to determine the antibacterial activities of the phenolic essential oil (EO) compounds hinokitiol, carvacrol, thymol, and menthol against oral pathogens. Aggregatibacter actinomycetemcomitans, Streptococcus mutans, Methicillin-resistant Staphylococcus aureus (MRSA), and Escherichia. coli were used in this study. The minimum inhibitory concentrations (MICs), minimum bactericidal concentrations (MBCs), bacterial growth curves, temperature and pH stabilities, and synergistic effects of the liquid and vapor EO compounds were tested. The MIC/MBC of the EO compounds, ranging from the strongest to weakest, were hinokitiol (40-60 μg/mL/40-100 μg/mL), thymol (100-200 μg/mL/200-400 μg/mL), carvacrol (200-400 μg/mL/200-600 μg/mL), and menthol (500-more than 2500 μg/mL/1000-more than 2500 μg/mL). The antibacterial activities of the four EO phenolic compound based on the agar diffusion test and bacterial growth curves showed that the four EO phenolic compounds were stable under different temperatures for 24 h, but the thymol activity decreased when the temperature was higher than 80°C. The combination of liquid carvacrol with thymol did not show any synergistic effects. The activities of the vaporous carvacrol and thymol were inhibited by the presence of water. Continual violent shaking during culture enhanced the activity of menthol. Both liquid and vaporous hinokitiol were stable at different temperatures and pH conditions. The combination of vaporous hinokitiol with zinc oxide did not show synergistic effects. These results showed that the liquid and vapor phases of hinokitiol have strong anti-oral bacteria abilities. Hinokitiol has the potential to be applied in oral health care products, dental materials, and infection controls to exert antimicrobial activity.

  16. Evaluation of the Antibacterial Potential of Liquid and Vapor Phase Phenolic Essential Oil Compounds against Oral Microorganisms

    PubMed Central

    Wu, Chi-Hao; Ko, Shun-Yao; Chen, Michael Yuanchien; Shih, Yin-Hua; Shieh, Tzong-Ming; Chuang, Li-Chuan; Wu, Ching-Yi

    2016-01-01

    The aim of the present study was to determine the antibacterial activities of the phenolic essential oil (EO) compounds hinokitiol, carvacrol, thymol, and menthol against oral pathogens. Aggregatibacter actinomycetemcomitans, Streptococcus mutans, Methicillin-resistant Staphylococcus aureus (MRSA), and Escherichia. coli were used in this study. The minimum inhibitory concentrations (MICs), minimum bactericidal concentrations (MBCs), bacterial growth curves, temperature and pH stabilities, and synergistic effects of the liquid and vapor EO compounds were tested. The MIC/MBC of the EO compounds, ranging from the strongest to weakest, were hinokitiol (40–60 μg/mL/40-100 μg/mL), thymol (100–200 μg/mL/200-400 μg/mL), carvacrol (200–400 μg/mL/200-600 μg/mL), and menthol (500-more than 2500 μg/mL/1000-more than 2500 μg/mL). The antibacterial activities of the four EO phenolic compound based on the agar diffusion test and bacterial growth curves showed that the four EO phenolic compounds were stable under different temperatures for 24 h, but the thymol activity decreased when the temperature was higher than 80°C. The combination of liquid carvacrol with thymol did not show any synergistic effects. The activities of the vaporous carvacrol and thymol were inhibited by the presence of water. Continual violent shaking during culture enhanced the activity of menthol. Both liquid and vaporous hinokitiol were stable at different temperatures and pH conditions. The combination of vaporous hinokitiol with zinc oxide did not show synergistic effects. These results showed that the liquid and vapor phases of hinokitiol have strong anti-oral bacteria abilities. Hinokitiol has the potential to be applied in oral health care products, dental materials, and infection controls to exert antimicrobial activity. PMID:27681039

  17. 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

    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.

  18. Large-Scale Water-Vapor Two-Phase Flow Simulations in Advanced Light Water Reactor Cores

    SciTech Connect

    Hiroyuki, Yoshida; Kazuyuki, Takase; Hidesada, Tamai; Hajime, Akimoto; Yasuo, Ose

    2004-07-01

    Fluid flow characteristics in a fuel bundle of a reduced-moderation light water reactor (RMWR) with a tight-lattice core were analyzed numerically using a newly developed two-phase flow analysis code under the full bundle size condition. Conventional analysis methods such as subchannel codes need composition equations based on the experimental data. In case that there are no experimental data regarding to the thermal-hydraulics in the tight-lattice core, therefore, it is difficult to obtain high prediction accuracy on the thermal design of the RMWR. Then the large-scale direct numerical simulations with a super computer were chosen. The axial velocity distribution in a fuel bundle changed sharply around a spacer. Momentum transfer of vapor in a tight-lattice core is linear along the flow direction. The interface characteristics between water and vapor were clarified quantitatively. (authors)

  19. Spontaneous formation of GaN/AlN core-shell nanowires on sapphire by hydride vapor phase epitaxy

    NASA Astrophysics Data System (ADS)

    Trassoudaine, Agnès; Roche, Elissa; Bougerol, Catherine; André, Yamina; Avit, Geoffrey; Monier, Guillaume; Ramdani, Mohammed Réda; Gil, Evelyne; Castelluci, Dominique; Dubrovskii, Vladimir G.

    2016-11-01

    Spontaneous GaN/AlN core-shell nanowires with high crystal quality were synthesized on sapphire substrates by vapor-liquid-solid hydride vapor phase epitaxy (VLS-HVPE) without any voluntary aluminum source. Deposition of aluminum is difficult to achieve in this growth technique which uses metal-chloride gaseous precursors: the strong interaction between the AlCl gaseous molecules and the quartz reactor yields a huge parasitic nucleation on the walls of the reactor upstream the substrate. We open up an innovative method to produce GaN/AlN structures by HVPE, thanks to aluminum etching from the sapphire substrate followed by redeposition onto the sidewalls of the GaN core. The paper presents the structural characterization of GaN/AlN core-shell nanowires, speculates on the growth mechanism and discusses a model which describes this unexpected behavior.

  20. Metalorganic vapor-phase epitaxy of indium phosphide and related materials

    NASA Astrophysics Data System (ADS)

    Chen, Gangyi

    The surface chemistry of indium phosphide and related compound semiconductors during metalorganic vapor-phase epitaxy (MOVPE) has been investigated. In particular, the group V precursor chemistry, indium phosphide (001) atomic structure and the InP oxidation process have been examined. The properties of the semiconductors were studied using infrared spectroscopy, molecular cluster calculations, x-ray photoelectron spectroscopy, reflectance difference spectroscopy, x-ray diffraction, and photoluminescence spectroscopy. Indium phosphide, gallium arsenide phosphide, and aluminum indium phosphide have been deposited by MOVPE using tertiarybutylphosphine and tertiarybutylarsine. Minimum incorporation in InP was observed at 565°C and a V/III ratio of 32. In this case, the material contained a background carrier concentration of 2.7 x 1014 cm-3, and the Hall mobilities were 4,970 and 135,000 cm2/V·s at 300 and 77 K. The oxygen contamination in AlInP was found to be only 9.0 x 10 15 cm-3 for deposition at 650°C and a V/III ratio of 35. The relative distribution of arsenic to phosphorus in GaAs yP1-y was determined at temperatures between 525 and 575°C. The distribution coefficient [(NAs/ NP)film/(PTBAs /PTBP)gas] ranged from 25.4 to 8.4, and exhibited an Arrhenius relationship with an apparent activation energy of 1.2 eV. The surface structure of the indium phosphide (001)-(2 x 1) reconstruction has been clarified in this thesis. Infrared spectra collected during atomic deuterium titration of the (2 x 1) surface revealed a sharp P-H stretching mode at 2308 cm-1. Based on theoretical cluster calculations using density functional theory, this mode was due to a single hydrogen atom bonded to one end of a buckled phosphorus dimer. These results confirmed that the (2 x 1) structure was stabilized by hydrogen. Indium phosphide oxidation has been found to be an activated process and strongly structure sensitive. The In-rich (2 x 4) surface reacted with oxygen at 300 K and

  1. 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

  2. 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

  3. 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.

  4. 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.

  5. Interactions Between Organized, Surface-Confined Monolayers and Vapor- Phase Probe Molecules. 7. Comparison of Self-Assemblying Organomercaptan Monolayers Deposited on Gold from Liquid and Vapor Phases

    DTIC Science & Technology

    1993-11-23

    The matrix of 6 organic surfaces were studied by FTIR external reflectance spectroscopy (FTIR- ERS), ellipsometry, and cyclic voltammetry , which...SAMs. Data obtained using cyclic voltammetry and STM show that the barrier properties of SAMs depend on the ambient phase from which the SAM assemblies

  6. Inflammatory Response and Barrier Dysfunction by Different e-Cigarette Flavoring Chemicals Identified by Gas Chromatography–Mass Spectrometry in e-Liquids and e-Vapors on Human Lung Epithelial Cells and Fibroblasts

    PubMed Central

    Gerloff, Janice; Sundar, Isaac K.; Freter, Robert; Sekera, Emily R.; Friedman, Alan E.; Robinson, Risa; Pagano, Todd

    2017-01-01

    Abstract Recent studies suggest that electronic cigarette (e-cig) flavors can be harmful to lung tissue by imposing oxidative stress and inflammatory responses. The potential inflammatory response by lung epithelial cells and fibroblasts exposed to e-cig flavoring chemicals in addition to other risk-anticipated flavor enhancers inhaled by e-cig users is not known. The goal of this study was to evaluate the release of the proinflammatory cytokine (interleukin-8 [IL-8]) and epithelial barrier function in response to different e-cig flavoring chemicals identified in various e-cig e-liquid flavorings and vapors by chemical characterization using gas chromatography–mass spectrometry analysis. Flavorings, such as acetoin (butter), diacetyl, pentanedione, maltol (malt), ortho-vanillin (vanilla), coumarin, and cinnamaldehyde in comparison with tumor necrosis factor alpha (TNFα), were used in this study. Human bronchial epithelial cells (Beas2B), human mucoepidermoid carcinoma epithelial cells (H292), and human lung fibroblasts (HFL-1) were treated with each flavoring chemical for 24 hours. The cells and conditioned media were then collected and analyzed for toxicity (viability %), lung epithelial barrier function, and proinflammatory cytokine IL-8 release. Cell viability was not significantly affected by any of the flavoring chemicals tested at a concentration of 10 μM to 1 mM. Acetoin and diacetyl treatment induced IL-8 release in Beas2B cells. Acetoin- and pentanedione-treated HFL-1 cells produced a differential, but significant response for IL-8 release compared to controls and TNFα. Flavorings, such as ortho-vanillin and maltol, induced IL-8 release in Beas2B cells, but not in H292 cells. Of all the flavoring chemicals tested, acetoin and maltol were more potent inducers of IL-8 release than TNFα in Beas2B and HFL-1 cells. Flavoring chemicals rapidly impaired epithelial barrier function in human bronchial epithelial cells (16-HBE) as measured by electric cell

  7. 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.

  8. Vapor-phase growth of transparent zinc oxide ceramics with c -axis orientation

    SciTech Connect

    Noritake, F.; Yamamoto, N.; Horiguchi, Y. ); Fujitsu, S.; Koumoto, K. ); Yanagida, H. )

    1991-01-01

    Large transparent specimens of polycrystalline zinc oxide with c-axis orientation have been prepared by the vapor transport method. Optical transmittance is 80% to 90% at 800 nm. X-ray diffraction peaks from faces other than (001) are negligible.

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

    SciTech Connect

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

    2012-01-01

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

  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. Physics-based agent to simulant correlations for vapor phase mass transport.

    PubMed

    Willis, Matthew P; Varady, Mark J; Pearl, Thomas P; Fouse, Janet C; Riley, Patrick C; Mantooth, Brent A; Lalain, Teri A

    2013-12-15

    Chemical warfare agent simulants are often used as an agent surrogate to perform environmental testing, mitigating exposure hazards. This work specifically addresses the assessment of downwind agent vapor concentration resulting from an evaporating simulant droplet. A previously developed methodology was used to estimate the mass diffusivities of the chemical warfare agent simulants methyl salicylate, 2-chloroethyl ethyl sulfide, di-ethyl malonate, and chloroethyl phenyl sulfide. Along with the diffusivity of the chemical warfare agent bis(2-chloroethyl) sulfide, the simulant diffusivities were used in an advection-diffusion model to predict the vapor concentrations downwind from an evaporating droplet of each chemical at various wind velocities and temperatures. The results demonstrate that the simulant-to-agent concentration ratio and the corresponding vapor pressure ratio are equivalent under certain conditions. Specifically, the relationship is valid within ranges of measurement locations relative to the evaporating droplet and observation times. The valid ranges depend on the relative transport properties of the agent and simulant, and whether vapor transport is diffusion or advection dominant.

  12. Simultaneous analysis of nine aromatic amines in mainstream cigarette smoke using online solid-phase extraction combined with liquid chromatography-tandem mass spectrometry.

    PubMed

    Zhang, Jie; Bai, Ruoshi; Zhou, Zhaojuan; Liu, Xingyu; Zhou, Jun

    2017-04-01

    A fully automated analytical method was developed and validated by this present study. The method was based on two-dimensional (2D) online solid-phase extraction liquid chromatography-tandem mass spectrometry (SPE-LC-MS/MS) to determine nine aromatic amines (AAs) in mainstream smoke (MSS) simultaneously. As a part of validation process, AAs yields for 16 top-selling commercial cigarettes from China market were evaluated by the developed method under both Health Canada Intensive (HCI) and ISO machine smoking regimes. The gas phase of MSS was trapped by 25 mL 0.6 M hydrochloric acid solution, while the particulate phase was collected on a glass fiber filter. Then, the glass fiber pad was extracted with hydrochloric acid solution in an ultrasonic bath. The extract was analyzed with 2D online SPE-LC-MS/MS. In order to minimize the matrix effects of sample on each analyte, two cartridges with different extraction mechanisms were utilized to cleanup disturbances of different polarity, which were performed by the 2D SPE. A phenyl-hexyl analytical column was used to achieve a chromatographic separation. Under the optimized conditions, the isomers of p-toluidine, m-toluidine and o-toluidine, 3-aminobiphenyl and 4-aminobiphenyl, and 1-naphthylamine and 2-naphthylamine were baseline separated with good peak shapes for the first time. The limits of detection for nine AAs ranged from 0.03 to 0.24 ng cig(-1). The recovery of the measurement of nine AAs was from 84.82 to 118.47%. The intra-day and inter-day precisions of nine AAs were less than 10 and 16%, respectively. Compared with ISO machine smoking regime, the AAs yields in MSS were 1.17 to 3.41 times higher under HCI machine smoking regime. Graphical abstract New method using online SPE-LC/MS/MS for analysis of aromatic amines in mainstream cigarette smoke.

  13. Reversible Semiconducting-to-Metallic Phase Transition in Chemical Vapor Deposition Grown Monolayer WSe2 and Applications for Devices

    NASA Astrophysics Data System (ADS)

    Ma, Yuqiang; Liu, Bilu; Zhang, Anyi; Chen, Liang; Fathi, Mohammad; Shen, Chenfei; Abbas, Ahmad; Ge, Mingyuan; Mecklenburg, Matthew; Zhou, Chongwu; Usc Nanolab Team

    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 is highly resistive, thus degrading the performance of field effect transistors (FETs) fabricated with WSe2 as active channel materials. We applied a phase engineering 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 107 and mobilities up to 66 cm2/Vs for monolayer WSe2. PI name: Chongwu Zhou.

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

    NASA Astrophysics Data System (ADS)

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

    2011-12-01

    The intrusion of vapor phase contaminants from subsurface sources into occupied buildings represents a possible exposure pathway and threat to human health. To make informed risk-management decisions regarding this pathway, it is important to build a conceptual model of the physical and chemical processes that govern vapor intrusion, and specifically to understand the source of the contaminant vapors. One vapor source includes nonaqueous phase liquids (NAPLs) entrapped within the vadose zone. The generation of vapors in the vadose zone from these sources under transient conditions imparted by the heat and water flux boundary conditions at the land surface involves complex mass-transfer processes; partitioning occurs simultaneously between NAPL, air, water and soil phases. Advection and diffusion within the air and water phases also play a critical role. It is our contention that the mass transfer to the air phase is a strong function of the soil moisture conditions in the direct vicinity of the NAPL source. We hypothesize that NAPL sources located in zones of high water saturation will have lower effective mass transfer rates than NAPLs located in low saturation regions, due to the higher diffusion resistance in the aqueous phase. Several studies have investigated NAPL mass transfer under unsaturated conditions and variable soil moisture (Ho and Udell 1992; Wilkins et al. 1995; Yoon et al. 2002); however, to build on this knowledge base, laboratory experimentation is needed under controlled conditions that considers spatially and temporally variable airflow fields and soil moisture saturations that occur in source zones in response to rain events and other climatic phenomena. The fundamental knowledge needed to address field problems cannot be generated in field systems due to lack of control and geologic complexities that are hard to characterize, leading to the need to use intermediate scale test systems. To investigate this problem, experiments were first

  15. [Analysis of seven compounds in mainstream cigarette smoke by ultra performance liquid chromatography using a beta-cyclodextrin mobile phase additive].

    PubMed

    Li, Zhonghao; Tang, Gangling; Pang, Yongqiang; Jiang, Xingyi; Chen, Zaigen; Hu, Qingyuan

    2010-08-01

    A rapid method for the analysis of hydroquinone, resorcinol, catechol, phenol, p-cresol, m-cresol, and o-cresol in mainstream cigarette smoke by ultra performance liquid chromatography (UPLC) using a beta-cyclodextrin (beta-CD) mobile phase additive was developed. The seven major phenolic compounds in mainstream smoke were collected with YC/T 255-2008 standard method. The extract was filtrated with 0.22 microm filtration film and then subjected to UPLC analysis. The separation was performed on an ACQUITY UPLC BEH Shield RP18 column, and the mobile phase with 4 g/L beta-CD additive was used. The fluorescence detection condition was optimized. The analysis time was 10 mm for one sample. Comparing with the high performance liquid chromatography (HPLC) methods published, the p-cresol and m-cresol were completely separated. In addition, the effect of beta-CD on fluorescence enhancement for seven major phenolic compounds was significant. The linearity were good between the peak area and the concentration in the linear ranges of seven phenolic compounds, and the correlation coefficients were greater than 0.999 9. The limits of detection of the method were 4 - 14 ng/cig, and the recoveries were 95.5% - 103.5% with relative standard deviations (RSDs) less than 4%.

  16. 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.

  17. 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.

  18. Comment on vapor phase homogeneous nucleation of CH 3CN and the scaling law for onset supersaturation ratios

    NASA Astrophysics Data System (ADS)

    Hale, Barbara N.; Kelly, Brendan

    1992-01-01

    We point out that the scaling law for onset vapor phase nucleation, ln Sonset ≈ 0.53 [Ω( Tc/ T-1)] 3/2, with Ω = 1.77 (from CH 3CN surface tension data) predicts the temperature dependence and approximate magnitude of CH 3CN supersaturation ratio data, S. This is contrary to the conclusions of Wright, Caldwell and El-Shall who estimate too large a value (2.14) for Ω. We note that Ω, the excess molecular surface entropy/ k, is more reliably extracted from the temperature derivative of the surface tension data.

  19. 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.

  20. Advances in modeling semiconductor epitaxy: Contributions of growth orientation and surface reconstruction to InN metalorganic vapor phase epitaxy

    NASA Astrophysics Data System (ADS)

    Kusaba, Akira; Kangawa, Yoshihiro; Kempisty, Pawel; Shiraishi, Kenji; Kakimoto, Koichi; Koukitu, Akinori

    2016-12-01

    We propose a newly improved thermodynamic analysis method that incorporates surface energies. The new theoretical approach enables us to investigate the effects of the growth orientation and surface reconstruction. The obtained knowledge would be indispensable for examining the preferred growth conditions in terms of the contribution of the surface state. We applied the theoretical approach to study the growth processes of InN(0001) and (000\\bar{1}) by metalorganic vapor phase epitaxy. Calculation results reproduced the difference in optimum growth temperature. That is, we successfully developed a new theoretical approach that can predict growth processes on various growth surfaces.

  1. 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.

  2. Growth of low-threading-dislocation-density GaN on graphene by hydride vapor phase epitaxy

    NASA Astrophysics Data System (ADS)

    He, Shunyu; Xu, Yu; Qi, Lin; Li, Zongyao; Cao, Bing; Wang, Chinhua; Zhang, Jicai; Wang, Jianfeng; Xu, Ke

    2017-03-01

    Recently, gallium nitride (GaN) films grown on graphene have been widely studied. Here, we have grown low-threading-dislocation-density GaN films on graphene by hydride vapor phase epitaxy (HVPE). The full widths at half maximum (FWHMs) of X-ray rocking curves (XRCs) of the GaN films were 276 and 350 arcsec at the 0002 and 10\\bar{1}2 reflections, respectively. This shows that the threading dislocation densities are on the order of magnitude of 108 cm‑2, which is consistent with the results of cathodoluminescence (CL).

  3. 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.

  4. A flux induced crystal phase transition in the vapor-liquid-solid growth of indium-tin oxide nanowires.

    PubMed

    Meng, Gang; Yanagida, Takeshi; Yoshida, Hideto; Nagashima, Kazuki; Kanai, Masaki; Zhuge, Fuwei; He, Yong; Klamchuen, Annop; Rahong, Sakon; Fang, Xiaodong; Takeda, Seiji; Kawai, Tomoji

    2014-06-21

    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.

  5. 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

    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.

  6. 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.

  7. 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 ...

  8. 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.; Aldén, 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.

  9. Vapor phase tri-methyl-indium seeding system suitable for high temperature spectroscopy and thermometry.

    PubMed

    Whiddon, R; Zhou, B; Borggren, J; Aldén, 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.

  10. Vapor phase tri-methyl-indium seeding system suitable for high temperature spectroscopy and thermometry

    SciTech Connect

    Whiddon, R.; Zhou, B.; Borggren, J.; Aldén, M.; Li, Z. S.

    2015-09-15

    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{sup 2}S{sub 1/2} → 5{sup 2}P{sub 1/2} and 6{sup 2}S{sub 1/2} → 5{sup 2}P{sub 3/2} 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.

  11. Investigation of the Hazards Posed by Chemical Vapors Released in Marine Operations - Phase II.

    DTIC Science & Technology

    1983-04-01

    at San Antonio, Texas . 307 U.S. COAST GUARDf SOUTHWEST RESEARCH INSTITUTE, SAN ANTONIO, TEXAS , USA UNIVERSITY OF TEXAS SCHOOL OF PUBLIC HEALTH, HOUSTON... TEXAS , USA SUBJECT CONSENT FOR PARTICIPATION IN AN INVESTIGATION OF "HAZARDS POSED BY CHEMICAL VAPORS RELEASED IN MARINE OPERATIONS: TASK V...write to the following persons: Dr. Stanley M. Pier Mr. William J. Astleford 5326 Dora Street Southwest Research Institute Houston, Texas , 77005, USA

  12. 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.

  13. One-Step Synthesis of Cross-Linked Ionic Polymer Thin Films in Vapor Phase and Its Application to an Oil/Water Separation Membrane.

    PubMed

    Joo, Munkyu; Shin, Jihye; Kim, Jiyeon; You, Jae Bem; Yoo, Youngmin; Kwak, Moo Jin; Oh, Myung Seok; Im, Sung Gap

    2017-02-15

    In spite of the huge research interest, ionic polymers could not have been synthesized in the vapor phase because the monomers of ionic polymers contain nonvolatile ionic salts, preventing the monomers from vaporization. Here, we suggest a new, one-step synthetic pathway to form a series of cross-linked ionic polymers (CIPs) in the vapor phase via initiated chemical vapor deposition (iCVD). 2-(Dimethylamino)ethyl methacrylate (DMAEMA) and 4-vinylbenzyl chloride (VBC) monomers are introduced into the iCVD reactor in the vapor phase to form a copolymer film. Simultaneously in the course of the deposition process, the tertiary amine in DMAEMA and benzylic chloride in VBC undergo a Menshutkin nucleophilic substitution reaction to form an ionic ammonium-chloride complex, forming a highly cross-linked ionic copolymer film of p(DMAEMA-co-VBC). To the best of our knowledge, this is the first report on the synthesis of CIP films in the vapor phase. The newly developed CIP thin film is further applied to the surface modification of the membrane for oil/water separation. With the hydrophilic and underwater oleophobic membrane whose surface is modified with the CIP film, excellent separation efficiency (>99%) and unprecedentedly high permeation flux (average 2.32 × 10(5) L m(-2) h(-1)) are achieved.

  14. 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…

  15. Vapor-liquid phase behavior of the iodine-sulfur water-splitting process : LDRD final report for FY03.

    SciTech Connect

    Bradshaw, Robert W.; Larson, Richard S.; Lutz, Andrew E.

    2004-01-01

    This report summarizes the results of a one-year LDRD project that was undertaken to better understand the equilibrium behavior of the iodine-water-hydriodic acid system at elevated temperature and pressure. We attempted to extend the phase equilibrium database for this system in order to facilitate development of the iodine-sulfur water-splitting process to produce hydrogen to a commercial scale. The iodine-sulfur cycle for thermochemical splitting of water is recognized as the most efficient such process and is particularly well suited to coupling to a high-temperature source of process heat. This study intended to combine experimental measurements of vapor-liquid-liquid equilibrium and equation-of-state modeling of equilibrium solutions using Sandia's Chernkin software. Vapor-liquid equilibrium experiments were conducted to a limited extent. The Liquid Chernkin software that was developed as part of an earlier LDRD project was enhanced and applied to model the non-ideal behavior of the liquid phases.

  16. 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.

  17. Investigation of cracks in GaN films grown by combined hydride and metal organic vapor-phase epitaxial method

    NASA Astrophysics Data System (ADS)

    Liu, Jianming; Liu, Xianlin; Li, Chengming; Wei, Hongyuan; Guo, Yan; Jiao, Chunmei; Li, Zhiwei; Xu, Xiaoqing; Song, Huaping; Yang, Shaoyan; Zhu, Qinsen; Wang, Zhanguo; Yang, Anli; Yang, Tieying; Wang, Huanhua

    2011-12-01

    Cracks appeared in GaN epitaxial layers which were grown by a novel method combining metal organic vapor-phase epitaxy (MOCVD) and hydride vapor-phase epitaxy (HVPE) in one chamber. The origin of cracks in a 22-μm thick GaN film was fully investigated by high-resolution X-ray diffraction (XRD), micro-Raman spectra, and scanning electron microscopy (SEM). Many cracks under the surface were first observed by SEM after etching for 10 min. By investigating the cross section of the sample with high-resolution micro-Raman spectra, the distribution of the stress along the depth was determined. From the interface of the film/substrate to the top surface of the film, several turnings were found. A large compressive stress existed at the interface. The stress went down as the detecting area was moved up from the interface to the overlayer, and it was maintained at a large value for a long depth area. Then it went down again, and it finally increased near the top surface. The cross-section of the film was observed after cleaving and etching for 2 min. It was found that the crystal quality of the healed part was nearly the same as the uncracked region. This indicated that cracking occurred in the growth, when the tensile stress accumulated and reached the critical value. Moreover, the cracks would heal because of high lateral growth rate.

  18. Vapor-phase polymerization of poly(3, 4-ethylenedioxythiophene) nanofibers on carbon cloth as electrodes for flexible supercapacitors

    NASA Astrophysics Data System (ADS)

    Zhao, Xin; Dong, Mengyang; Zhang, Junxian; Li, Yingzhi; Zhang, Qinghua

    2016-09-01

    In this study, an evaporative vapor-phase polymerization approach was employed to fabricate vertically aligned poly(3, 4-ethylenedioxythiophene) (PEDOT) nanofibers on the surface of carbon cloth (CC). Optimized reaction conditions can obtain well distributed and uniform layers of high-aspect-ratio PEDOT nanofibers on CC. The hierarchical PEDOT/CC structure as a freestanding electrode exhibits good electrochemical properties. As a flexible symmetric supercapacitor, the PEDOT/CC hybrid electrode displays a specific areal capacitance of 201.4 mF cm-2 at 1 mA cm-2, good flexibility with a higher value (204.6 mF cm-2) in the bending state, and a good cycling stability of 92.4% after 1000 cycles. Moreover, the device shows a maximum energy density of 4.0 Wh kg-1 (with a power density of 3.2 kW kg-1) and a maximum power density of 4.2 kW kg-1 (with an energy density of 3.1 Wh kg-1). The results demonstrate that PEDOT may be a promising material for storage devices through a simple and efficient vapor-phase polymerization process with precisely controlled reaction conditions.

  19. Tri-halide vapor phase epitaxy of thick GaN using gaseous GaCl3 precursor

    NASA Astrophysics Data System (ADS)

    Murakami, Hisashi; Takekawa, Nao; Shiono, Anna; Thieu, Quang Tu; Togashi, Rie; Kumagai, Yoshinao; Matsumoto, Koh; Koukitu, Akinori

    2016-12-01

    Tri-halide vapor phase epitaxy (THVPE) of thick GaN using GaCl3 was investigated for fabricating low-cost, high-crystalline-quality GaN substrates instead of the conventional manufacturing method of GaCl-based hydride vapor phase epitaxy (HVPE). The growth rate and upper growth temperature limit of GaN using THVPE were found to be much higher than those obtained using conventional HVPE under the same growth conditions. Drastic reduction in the number of dark spots measured by cathodoluminescence at room temperature was observed for the high-temperature-grown GaN layer on the (000-1) GaN/sapphire template due to the enhancement of precursor migration on the growing surface. It was found that the incorporation of impurities such as O, C, and Cl can be reduced even on the N-polarity GaN by increasing the growth temperature. The possibility of enlargement of the crystal diameter by growing the N-polarity GaN layer using THVPE was also proposed.

  20. 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.

  1. 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

  2. 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.

  3. 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

    2012-12-07

    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.

  4. 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.

  5. 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.

  6. Vapor phase exsolution as a controlling factor in hydrogen isotope variation in granitic rocks: the Notch Peak granitic stock, Utah

    USGS Publications Warehouse

    Nabelek, P.I.; O'Neil, J.R.; Papike, J.J.

    1983-01-01

    The Notch Peak granitic stock, western Utah, is comprised of three concentric sequentially intruded rock types, from granite at the rim, to quartz monzonite I, to quartz monzonite II at the core. The ??18O values of whole rocks vary about an average of 9.4 (SMOW), irrespective of the rock type and position relative to contact, suggesting that the three magmas had the same parent. The whole rock ??D values in the stock range from -100 to -55. ??D values increase toward the cores of both quartz monzonite I and quartz monzonite II, resulting in concentric contours. The ??D contours of quartz monzonite II cross-cut those of quartz monzonite I, suggesting little isotopic interaction between these bodies and the absence of a late pervasive fluid phase. There is a positive correlation between ??D values and water content of the samples, where samples from each body define a distinct field. The positive correlation is explained by isotopic fractionation attendant on vapor exsolution from the crystallizing magma. An observed increase in ??D with the degree of chloritization, a trend opposite to that observed in systems where participation of meteoric water has been demonstrated, is the result of subsolidus interaction with the exsolved fluids. These results show that large variations in the hydrogen isotope ratios of a granitoid can arise by exsolution of a vapor phase from the melt on crystallization. In general, magmas with larger modal amount of primary hydrous phases will tend to have higher ??D values than those with small amounts of hydrous phases. Furthermore, the relatively high ??D values of chlorites at Notch Peak confirm the applicability of classical concepts of closed-system deuteric alteration to some granitoid bodies. Thus, meteoric water interaction need not be always invoked to explain hydrogen isotope variation and deuteric alteration in granitoids. ?? 1983.

  7. First principles Monte Carlo simulations of aggregation in the vapor phase of hydrogen fluoride

    SciTech Connect

    McGrath, Matthew J.; Ghogomu, Julius. N.; Mundy, Christopher J.; Kuo, I-F. Will; Siepmann, J. Ilja

    2010-01-01

    The aggregation of superheated hydrogen fluoride 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 Å3/molecule) and at three different temperatures (T = 310, 350, and 390 K). Aggregation-volume-bias and configurational-bias Monte Carlo approaches (along with pre-sampling with an approximate potential) were employed to increase the sampling efficiency of cluster formation and destruction.

  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. Membrane Vapor Enricher for Water for Injection (WFI) Production. Phase 1

    DTIC Science & Technology

    1987-12-15

    GROUP Is-UPO.~~.~ Gas Separation Membranes, ~ I~- ~ .-/I 23 01 Pervaporation Gas Separation, 23 105 Waer for lnip~tion 01’rV :.CiC L 1 F,:~ 19...MEMBRANE SEPARATION PROCESSES BACKGROUND 12 A. GENERAL 12 B. GAS SEPARATION BACKGROUND 12 C. PERVAPORATION 15 D. DIFFERENCES BETWEEN LIQUID AND GASEOUS...PRODUCTION 20 A. ORIGINAL CONCEPT 20 B. IMPROVED WFI SYSTEM CONCEPT BASED ON PERVAPORATION 20 C. ADVANTAGES OF THE MEMBRANE VAPOR ENRICHER APPROACHES TO WFI

  11. 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.

  12. Competing gas phase reactions during vapor transport deposition of ZnO nanowires

    NASA Astrophysics Data System (ADS)

    Driscoll, Eric; Range, Kevin; Tzolov, Marian

    2012-02-01

    We present results illuminating some of the major chemical processes in the vapor deposition of ZnO nanowires. The analysis of our deposition experiments indicates that carbon dioxide is a major oxidizing agent rather than carbon monoxide as previously thought. Additionally, we present evidence that carbon monoxide will etch zinc oxide at high temperatures. Zinc oxide nanowires have been prepared by using chemical vapor deposition on silicon (100) substrates with a 10-15nm layer of gold as a catalyst. Zinc oxide and graphite powders were heated to approximately 1000^oC in a tube furnace in a flow of argon. We have delivered oxygen gas specifically in the growth zone to facilitate the formation of high aspect ratio nanowire growth. Thermodynamics calculations were used to justify the growth and etching processes. Imaging of samples was performed with scanning electron microscopy. Chemical composition was determined by energy dispersive x-ray spectroscopy. Photoluminescence spectroscopy was used to characterize the emission properties of the zinc oxide samples.

  13. QCM gas phase detection with ceramic materials--VOCs and oil vapors.

    PubMed

    Latif, Usman; Rohrer, Andreas; Lieberzeit, Peter A; Dickert, Franz L

    2011-06-01

    Titanate sol-gel layers imprinted with carbonic acids were used as sensitive layers on quartz crystal microbalance. These functionalized ceramics enable us detection of volatile organic compounds such as ethanol, n-propanol, n-butanol, n-hexane, n-heptane, n-/iso-octane, and n-decane. Variation of the precursors (i.e., tetrabutoxy titanium, tetrapropoxy titanium, tetraethoxy titanium) allows us to tune the sensitivity of the material by a factor of 7. Sensitivity as a function of precursors leads to selective inclusion of n-butanol vapors down to 1 ppm. The selectivity of materials is optimized to differentiate between isomers, e.g., n- and iso-octane. The results can be rationalized by correlating the sensor effects of hydrocarbons with the Wiener index. A mass-sensitive sensor based on titanate layer was also developed for monitoring emanation of degraded engine oil. Heating the sensor by a meander avoids vapor condensation. Thus, a continuously working oil quality sensor was designed.

  14. Condensed phase conversion and growth of nanorods instead of from vapor

    SciTech Connect

    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.

  15. 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.

  16. Thin film solid-state lithium batteries prepared by convective vapor-phase processes

    SciTech Connect

    Takehara, Z.; Ogumi, Z.; Uchimoto, Y.; Endo, E. . Faculty of Engineering); Kanamori, Y. )

    1991-06-01

    Thin-film solid-state lithium batteries of total thickness less than 20 {mu}m were prepared. These thin lithium batteries were fabricated using a thin film of TiS{sub 2} prepared by chemical vapor deposition (CVD) as the cathode active material, a thin film of solid polymer prepared by plasma polymerization as the electrolyte, and a thin film of lithium deposited by thermal evaporation as the anode. The solid polymer electrolyte film was formed by complexation of plasma-polymerized tris (2-methoxyethoxy) vinylsilane with lithium perchlorate. Its room temperature conductivity was greater than 10{sup {minus}6} S cm{sup {minus}1} (10{sup 2} {Omega} cm{sup 2} resistance per unit area). The battery's discharge properties at room temperature and different current densities were examined. In this paper the effects of the interfaces between the solid polymer electrolyte and the electrodes on the battery's discharge performance are discussed.

  17. 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.

  18. A study on the epitaxial Bi2Se3 thin film grown by vapor phase epitaxy

    NASA Astrophysics Data System (ADS)

    Lin, Yen-Cheng; Chen, Yu-Sung; Lee, Chao-Chun; Wu, Jen-Kai; Lee, Hsin-Yen; Liang, Chi-Te; Chang, Yuan Huei

    2016-06-01

    We report the growth of high quality Bi2Se3 thin films on Al2O3 substrates by using chemical vapor deposition. From the atomic force microscope, x-ray diffraction and transmission electron microscope measurements we found that the films are of good crystalline quality, have two distinct domains and can be grown epitaxially on the Al2O3 substrate. Carrier concentration in the sample is found to be 1.1 × 1019 cm-3 between T = 2 K to T = 300 K, and electron mobility can reach 954 cm2/V s at T = 2 K. Weak anti-localization effect is observed in the low temperature magneto-transport measurement for the sample which indicates that the thin film has topological surface state.

  19. Vapor phase synthesis and characterization of bimetallic alloy and supported nanoparticle catalysts

    NASA Astrophysics Data System (ADS)

    Abdelsayed, V.; Saoud, K. M.; El-Shall, M. Samy

    2006-08-01

    The laser vaporization controlled condensation (LVCC) technique coupled with a differential mobility analyzer (DMA) is used to synthesize size-selected alloy nanoparticles and nanoparticle catalyst systems. The formation of Au-Ag alloy nanoparticles is concluded from the observation of only one plasmon band. The maximum of the plasmon absorption is found to vary linearly with the gold mole fraction. For the Au-Pd system, the XRD data confirms the formation of the alloy nanoparticles with no evidence of any of the pure components. The Au/CeO2 nanoparticle catalyst prepared by the LVCC method is a promising catalyst for low temperature CO oxidation due to its high activity and stability.

  20. 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.

  1. 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 μg/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

  2. 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.

  3. 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.

  4. A low phase noise microwave frequency synthesis for a high-performance cesium vapor cell atomic clock.

    PubMed

    François, 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.

  5. A low phase noise microwave frequency synthesis for a high-performance cesium vapor cell atomic clock

    NASA Astrophysics Data System (ADS)

    François, 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 rad2/Hz and -129 dB rad2/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.

  6. 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.

  7. Vapor pressures, gas-phase PVT properties, and second virial coefficients for 1,1,1-trifluoroethane

    SciTech Connect

    Zhang, H.L.; Sato, Haruki; Watanabe, Koichi

    1995-07-01

    The PVT properties of 1,1,1-trifluoroethane (R-143a) in the gas phase have been measured by a Burnett apparatus in the range of temperatures from 320 to 380 K and at pressures up to 6 MPa. The vapor pressures in the range of temperatures from 295 to 342 K have also been measured, and a vapor-pressure correlation has been developed. The critical pressure was determined to be (3.776 {+-} 0.005) MPa on the basis of the present measurements. The second virial coefficients have been determined along seven isotherms, and a truncated virial equation of state has also been developed to represent the temperature dependence of the second virial coefficients and the present Burnett PVT measurements. The experimental uncertainties of temperature, pressure, density, and second virial coefficient throughout the present study were estimated to be no more than {+-} 8 mK, {+-} 0.8 kPa, {+-} 0.12%, and {+-} 5%, respectively. The purity of the R-143a sample used was better than 99.95 mol %.

  8. Dispersibility of vapor phase oxygen and nitrogen functionalized multi-walled carbon nanotubes in various organic solvents

    PubMed Central

    Khazaee, Maryam; Xia, Wei; Lackner, Gerhard; Mendes, Rafael G.; Rümmeli, Mark; Muhler, Martin; Lupascu, Doru C.

    2016-01-01

    The synthesis and characterization of gas phase oxygen- and nitrogen-functionalized multi-walled carbon nanotubes (OMWCNTs and NMWCNTs) and the dispersibility of these tubes in organic solvents were investigated. Recently, carbon nanotubes have shown supreme capacity to effectively enhance the efficiency of organic solar cells (OSCs). A critical challenge is to individualize tubes from their bundles in order to provide homogenous nano-domains in the active layer of OSCs. OMWCNTs and NMWCNTs were synthesized via HNO3 vapor and NH3 treatments, respectively. Surface functional groups and the structure of the tubes were analyzed by temperature-programmed desorption, Fourier transform infrared spectroscopy, transmission electron microscopy, and Raman spectroscopy which confirmed the formation of functional groups on the tube surface and the enhancement of surface defects. Elemental analysis demonstrated that the oxygen and nitrogen content increased with increasing treatment time of the multi-walled carbon nanotube (MWCNT) in HNO3 vapor. According to ultra-violet visible spectroscopy, modification of the MWCNT increased the extinction coefficients of the tubes owing to enhanced compatibility of the functionalized tubes with organic matrices. PMID:27188622

  9. 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.

  10. Growth and characterization of GaAs, AlGaAs and their heterostructures by organometallic vapor phase epitaxy

    SciTech Connect

    Shealy, J.R.

    1983-01-01

    Organometallic Vapor Phase Epitaxy (OMVPE) is a cold wall vapor desposition technique using organometallic and/or hydride sources for the fabrication of a variety of epitaxial compound semiconductor alloys on suitable substrates. The use of the OMVPE process to produce high quality GaAs, AlGaAs, and their heterostructures on GaAs substrates using trimethygalium (TMG), trimethylalumium (TMA), and arsine is described. For GaAs epitaxial films, the unintentional residual donor sand acceptors have been identified using far-infrared photo-ionization data, and low temperature photoluminescence, respectively, and their concentrations have been evaluated using Hall data. For the growth of AlGaAs films, it was observed that poor quality films were obtained due to oxygen contamination of the layer during growth. A series of graded bandgap heterostructures and abrupt quantum well heterostructures were grown over a variety of growth conditions. Composition gradings were controlled over a full range of alloy compositions on distances as small as 500 - 1000 A, and a 40 A quantum well heterostructure was obtained at low growth temperatures (550/sup 0/C). Finally, results are presented on a few devices which incorporate metallurgical junctions and heterojunctions with the GaAs/AlGaAs system. These devices include a microwave vertical FET structure, graded bandgap solar cells, and light emitting diodes.

  11. Phase degradation in BxGa1–xN films grown at low temperature by metalorganic vapor phase epitaxy

    DOE PAGES

    Gunning, Brendan P.; Moseley, Michael W.; Koleske, Daniel D.; ...

    2016-11-01

    Using metalorganic vapor phase epitaxy, a comprehensive study of BxGa1-xN growth on GaN and AlN templates is described. BGaN growth at high-temperature and high-pressure results in rough surfaces and poor boron incorporation efficiency, while growth at low-temperature and low-pressure (750–900 °C and 20 Torr) using nitrogen carrier gas results in improved surface morphology and boron incorporation up to ~7.4% as determined by nuclear reaction analysis. However, further structural analysis by transmission electron microscopy and x-ray pole figures points to severe degradation of the high boron composition films, into a twinned cubic structure with a high density of stacking faults andmore » little or no room temperature photoluminescence emission. Films with <1% triethylboron (TEB) flow show more intense, narrower x-ray diffraction peaks, near-band-edge photoluminescence emission at ~362 nm, and primarily wurtzite-phase structure in the x-ray pole figures. For films with >1% TEB flow, the crystal structure becomes dominated by the cubic phase. As a result, only when the TEB flow is zero (pure GaN), does the cubic phase entirely disappear from the x-ray pole figure, suggesting that under these growth conditions even very low boron compositions lead to mixed crystalline phases.« less

  12. Phase degradation in BxGa1–xN films grown at low temperature by metalorganic vapor phase epitaxy

    SciTech Connect

    Gunning, Brendan P.; Moseley, Michael W.; Koleske, Daniel D.; Allerman, Andrew A.; Lee, Stephen R.

    2016-11-01

    Using metalorganic vapor phase epitaxy, a comprehensive study of BxGa1-xN growth on GaN and AlN templates is described. BGaN growth at high-temperature and high-pressure results in rough surfaces and poor boron incorporation efficiency, while growth at low-temperature and low-pressure (750–900 °C and 20 Torr) using nitrogen carrier gas results in improved surface morphology and boron incorporation up to ~7.4% as determined by nuclear reaction analysis. However, further structural analysis by transmission electron microscopy and x-ray pole figures points to severe degradation of the high boron composition films, into a twinned cubic structure with a high density of stacking faults and little or no room temperature photoluminescence emission. Films with <1% triethylboron (TEB) flow show more intense, narrower x-ray diffraction peaks, near-band-edge photoluminescence emission at ~362 nm, and primarily wurtzite-phase structure in the x-ray pole figures. For films with >1% TEB flow, the crystal structure becomes dominated by the cubic phase. As a result, only when the TEB flow is zero (pure GaN), does the cubic phase entirely disappear from the x-ray pole figure, suggesting that under these growth conditions even very low boron compositions lead to mixed crystalline phases.

  13. 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.

  14. 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 0.6 pg/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.

  15. Demonstration of a vapor-density monitoring system using UV radiation generated from waveguide quasi-phase-matched SHG waveguide devices

    NASA Astrophysics Data System (ADS)

    Galanti, Shirley A.; Berzins, Leon V.; Brown, J. B.; Tamosaitis, Robert S.; Bortz, Michael L.; Day, Timothy; Fejer, Martin M.; Wang, Weizhi

    1996-05-01

    Many industrial application require non-intrusive diagnostics for process monitoring and control. One example is the physical vapor deposition of titanium alloys. In this paper we present a system based on laser absorption spectroscopy for monitoring titanium vapor. Appropriate transitions for monitoring high rate vaporization of titanium require extension of available IR diode technology to the UV. The heart of this vapor density monitoring system is the 390 nm radiation generated from quasi-phase matched interactions within periodically poled waveguides. In this paper, key system components of a UV laser absorption spectroscopy based system specific for titanium density monitoring are described. Analysis is presented showing the minimum power levels necessary from the ultraviolet laser source. Performance data for prototype systems using second harmonic generation waveguide technology is presented. Application of this technology to other alloy density monitoring systems is discussed.

  16. 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.

  17. 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.

  18. On the formation of the SbGa heteroantisite in metalorganic vapor-phase epitaxial GaAs:Sb

    NASA Astrophysics Data System (ADS)

    Yakimova, R.; Omling, P.; Yang, B. H.; Samuelson, L.; Fornell, J.-O.; Ledebo, L.

    1991-09-01

    Metalorganic vapor-phase epitaxial growth of GaAs doped with isovalent Sb is reported. By increasing the trimethylantimony concentration during growth the total Sb concentration was varied between 1×1017-1×1019 cm-3. A new deep level defect with an activation energy of the thermal emission rates of Ec-0.54 eV is observed. The defect concentration increases with increasing As partial pressure and with increasing Sb doping. It is also found that the EL2 concentration decreases with increasing Sb doping. The new energy level is suggested to be the 0/+ transition of the SbGa heteroantisite defect. No photocapacitance quenching effect, reflecting a metastable state as seen for EL2(AsGa), is observed for SbGa.

  19. Single-monolayer quantum wells of GaInAs in InP grown by metalorganic vapor phase epitaxy

    NASA Astrophysics Data System (ADS)

    Seifert, W.; Fornell, J.-O.; Ledebo, L.; Pistol, M.-E.; Samuelson, L.

    1990-03-01

    GaInAs/InP quantum wells differing in thickness between 1 and 20 monolayers (1 monolayer≊2.93 Å) have been grown by low-pressure (50 mbar) metalorganic vapor phase epitaxy and investigated by 2 K photoluminescence. To our knowledge this is the first observation of the one monolayer quantum well. Well-resolved photoluminescence peaks were observed and were attributed to recombination of excitons bound to quantum wells of defined monolayer thickness. The growth rate could be adjusted to produce a one monolayer quantum well. Its photoluminescence peak was observed at 1.245 eV, corresponding to a quantum confinement shift of 434 meV. The full width at half maximum of this peak was only 8 meV.

  20. Well-ordered self-assembled monolayers created via vapor-phase reactions on a monolayer template.

    PubMed

    Ferguson, Melinda K; Low, Emily R; Morris, John R

    2004-04-13

    The reaction of vapor-phase alkyl isocyanates (O=C=N-(CH2)n-1CH3) with OH-terminated alkanethiol template monolayers on Au produces well-organized self-assembled monolayers, containing intrachain carbamate linkages (Au/S(CH2)16O(C=O)NH(CH2)n-1CH3, where n = 1-8, 11, and 12). X-ray photoelectron spectroscopy, contact angle goniometry, and reflection absorption infrared spectroscopy suggest that the template surface completely reacts with the isocyanates yielding a monolayer that contains an interchain hydrogen-bonded carbamate network. Spectroscopic data indicates that the alkyl underlayer remains well ordered following reaction with the isocyanates. The order of the overlayer and the hydrogen-bonding interactions between adjacent chains increase as a function of the alkyl isocyanate chain length, n. The overlayer appears to be well ordered for n > or = 5.

  1. Metalorganic vapor phase epitaxy of InN on GaN using tertiary-butylhydrazine as nitrogen source

    NASA Astrophysics Data System (ADS)

    Kremzow, Raimund; Pristovsek, Markus; Stellmach, Joachim; Savaş, Özgür; Kneissl, Michael

    2010-06-01

    The growth of InN on GaN/sapphire by metalorganic vapor-phase epitaxy (MOVPE) using tertiary-butylhydrazine (tBHy) was studied by varying temperature, V/III-ratio, growth time and carrier gas between nitrogen and hydrogen. The growth was characterized in-situ by spectroscopic ellipsometry and ex-situ by high resolution X-ray diffraction, atomic force microscopy and scanning electron microscopy. In contrast to ammonia, it was predicted that tBHy should allow InN growth for a much wider growth window and low V/III-ratios with growth temperatures below 600C. However, over a wide range of growth parameters only growth of metallic indium droplets was observed.

  2. In situ passivation of InP surface using H2S during metal organic vapor phase epitaxy

    NASA Astrophysics Data System (ADS)

    Lu, Hong-Liang; Terada, Yuki; Shimogaki, Yukihiro; Nakano, Yoshiaki; Sugiyama, Masakazu

    2009-10-01

    An in situ surface passivation of InP(100) using H2S during metal organic vapor phase epitaxy has been characterized by x-ray photoemission spectroscopy and photoluminescence. X-ray photoelectron spectra indicate that the H2S-treated InP at 300 °C is free of P and In oxides even after exposure to air. The enhancement of photoluminescence intensity confirms that H2S passivation of an InP epilayer can reduce the surface defects. It is shown that H2S treatment results in In-S bonds, which dominate the sulfur-passivated InP surface, effectively suppressing interface oxidation during the subsequent ultrathin Al2O3 dielectric film growth.

  3. Growth of thick GaN layers on laser-processed sapphire substrate by hydride vapor phase epitaxy

    NASA Astrophysics Data System (ADS)

    Koyama, Koji; Aida, Hideo; Kim, Seong-Woo; Ikejiri, Kenjiro; Doi, Toshiro; Yamazaki, Tsutomu

    2014-10-01

    A 600 μm thick GaN layer was successfully grown by hydride vapor phase epitaxy by replacing the standard sapphire substrate with that processed by a focused laser beam within the substrate. The effects of the laser processing on the curvature and cracking of the GaN layer were investigated. Microscopic observations of the interior of the thick GaN layer revealed that the laser-processed substrate suppressed the generation of microcracks in the GaN layer. In addition, the laser processing was also found to reduce the change in the curvature during the GaN layer growth in comparison to that on the standard substrate. It is shown that the overlapping microcracks observed in the GaN layer on the standard sapphire substrate lead to serious cracking after thick GaN layer growth.

  4. Preparation of Freestanding GaN Wafers by Hydride Vapor Phase Epitaxy with Void-Assisted Separation

    NASA Astrophysics Data System (ADS)

    Oshima, Yuichi; Eri, Takeshi; Shibata, Masatomo; Sunakawa, Haruo; Kobayashi, Kenji; Ichihashi, Toshinari; Usui, Akira

    2003-01-01

    We have developed a novel technique for preparing large-scale freestanding GaN wafers. Hydride vapor phase epitaxy (HVPE) growth of thick GaN layer was performed on a GaN template with a thin TiN film on the top. After the cooling process of the HVPE growth, the thick GaN layer was easily separated from the template by the assistance of many voids generated around the TiN film. As a result, a freestanding GaN wafer was obtained. The wafer obtained had a diameter of 45 mm, and a mirror-like surface. The-full-width-at-half-maximum (FWHM) of (0002) and (10\\bar{1}0) peaks in the X-ray rocking curve profile were 60 and 92 arcsec, respectively. The dislocation density was evaluated at 5× 106 cm-3 by etch pit density measurement.

  5. Organometallic Vapor-Phase Epitaxial Growth and Characterization of GaAs/Zn(S, Se) Multilayered Structures

    NASA Astrophysics Data System (ADS)

    Fujita, Shigeo; Murawala, Prakash A.; Maruo, Seiji; Tsuji, Osamu; Fujita, Shizuo

    1991-01-01

    We report growth conditions of lattice-matched dissimilar semiconductor multilayered structures of GaAs/Zn(S, Se) systems by organometallic vapor-phase epitaxy (OMVPE). Since the optimum growth temperature for GaAs is much higher than that of Zn(S, Se), we performed low-temperature growth (470°C) of GaAs by photo-assisted OMVPE. A smooth growth surface of GaAs on Zn(S, Se) was achieved by lattice-matching, sufficient preflow of triethylarsenic (TEAs) and a Zn-stabilized surface before starting the growth of GaAs; hence we succeeded in the fabrication of a ZnSSe/GaAs/ZnSSe double hetero (DH) structure and a superlattice. Thermal annealing of the DH structure showed no appreciable Zn diffusion into GaAs up to 650°C but showed thermal stability at the interface up to 550°C.

  6. 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.

  7. Highly resistive C-doped hydride vapor phase epitaxy-GaN grown on ammonothermally crystallized GaN seeds

    NASA Astrophysics Data System (ADS)

    Iwinska, Malgorzata; Piotrzkowski, Ryszard; Litwin-Staszewska, Elzbieta; Sochacki, Tomasz; Amilusik, Mikolaj; Fijalkowski, Michal; Lucznik, Boleslaw; Bockowski, Michal

    2017-01-01

    GaN crystals were grown by hydride vapor phase epitaxy (HVPE) and doped with C. The seeds were high-structural-quality ammonothermally crystallized GaN. The grown crystals were highly resistive at 296 K and of high structural quality. High-temperature Hall effect measurements revealed p-type conductivity and a deep acceptor level in the material with an activation energy of 1 eV. This is in good agreement with density functional theory calculations based on hybrid functionals as presented by the Van de Walle group. They obtained an ionization energy of 0.9 eV when C was substituted for N in GaN and acted as a deep acceptor.

  8. Deep-level transient spectroscopy studies of Ni- and Zn-diffused vapor-phase-epitaxy n-GaAs

    NASA Technical Reports Server (NTRS)

    Partin, D. L.; Chen, J. W.; Milnes, A. G.; Vassamillet, L. F.

    1979-01-01

    The paper presents deep-level transient spectroscopy studies of Ni- and Zn-diffused vapor-phase epitaxy n-GaAs. Nickel diffused into VPE n-GaAs reduces the hole diffusion length L sub p from 4.3 to 1.1 microns. Deep-level transient spectroscopy was used to identify energy levels in Ni-diffused GaAs; the as-grown VPE GaAs contains traces of these levels and an electron trap. Ni diffusion reduces the concentration of this level by an amount that matches the increase in concentration of each of the two Ni-related levels. A technique for measuring minority-carrier capture cross sections was developed, which indicates that L sub p in Ni-diffused VPE n-GaAs is controlled by the E sub c - 0.39 eV defect level.

  9. Heterogeneous equilibrium between the condensed phase and vapor of aprotonic solvents and electrolytes based on them II. Solvent mixtures

    NASA Astrophysics Data System (ADS)

    Gaidym, I. L.; Gurevich, I. G.; Shchitnikov, V. K.; Dubasova, V. S.; Tumanov, B. I.

    1982-06-01

    Experimental results for the saturated vapor pressure of mixtures of organic solvents with electrolytes based on them are given, together with thermodynamic characteristics of the vaporization process calculated on this basis.

  10. Solid- and vapor-phase antimicrobial activities of six essential oils: susceptibility of selected foodborne bacterial and fungal strains.

    PubMed

    López, P; Sánchez, C; Batlle, R; Nerín, 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

  11. A model for arsenic anti-site incorporation in GaAs grown by hydride vapor phase epitaxy

    NASA Astrophysics Data System (ADS)

    Schulte, K. L.; Kuech, T. F.

    2014-12-01

    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, AsGa 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 (TD) and gallium chloride partial pressures (PGaCl), 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, RG, was controlled by conditions near thermodynamic equilibrium. [EL2] fell below equilibrium levels when RG was controlled by surface kinetic processes, with the disparity increasing as RG 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 TD and/or low PGaCl, 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 TD and/or high PGaCl, 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 AsGa. 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.

  12. Plasma-Enhanced Chemical Vapor Deposition of Beta-Tungsten, a Metastable Phase,

    DTIC Science & Technology

    the resistivity drops below 11 micron omega cm. Concomitant with this resistivity change is a phase change to alpha-W, the equilibrium, body - centered - cubic form. Additional keywords: reprint; and Army research.

  13. Enhanced quality thin film Cu(In,Ga)Se.sub.2 for semiconductor device applications by vapor-phase recrystallization

    DOEpatents

    Tuttle, John R.; Contreras, Miguel A.; Noufi, Rommel; Albin, David S.

    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.

  14. 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.

  15. MW Spectroscopy Coupled with Ultrafast UV Laser Vaporization: Succinic Acid in the Gas Phase

    NASA Astrophysics Data System (ADS)

    Mendez, Estibaliz; Ecija, Patricia; Cocinero, Emilio J.; Castano, Fernando; Basterretxea, Francisco J.; Godfrey, Peter D.; McNaughton, Don; Jahn, Michaela K.; Nair, K. P. Rajappan; Grabow, Jens-Uwe

    2013-06-01

    Recent lab and field measurements have indicated critical roles of organic acids in enhancing new atmospheric aerosol formation. In order to understand the nucleation process, here we report an experimental and theoretical investigation of chemical structure of succinic acid. We have used the technique of Fourier Transform Microwave Spectroscopy (FTMW). Succinic acid was vaporized by UV ultrafast laser ablation to suppress thermal decomposition processes^a and seeded into an expanding stream of Ne forming a supersonic jet. The rotational spectrum detected the presence of a single most stable conformation in the cm- mm- wave regions for which accurate rotational and centrifugal distortion parameters have been determined. The study was extended to all monosubstituted isotopic species (^{13}C, ^{18}O, D(O)), which were positively identified, leading to an accurate determination of the effective and substitution structures of the molecule. The experimental study was supplemented by ab initio (MP2) and DFT (M06-2X and B3LYP) calculations. ^{a} E. J. Cocinero, A. Lesarri, P. écija, F. J. Basterretxea, J. U. Grabow, J. A. Fernández and F. Castaño, Angew. Chem. Int. Ed., 51, 3119-3124, 2012.

  16. The gas phase emitter effect of lanthanum within ceramic metal halide lamps and its dependence on the La vapor pressure and operating frequency

    SciTech Connect

    Ruhrmann, C.; Hoebing, T.; Bergner, A.; Groeger, S.; Awakowicz, P.; Mentel, J.; Denissen, C.; Suijker, J.

    2015-08-07

    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.

  17. 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.

  18. Oral Trauma and Tooth Avulsion Following Explosion of E-Cigarette.

    PubMed

    Rogér, James M; Abayon, Maricelle; Elad, Sharon; Kolokythas, Antonia

    2016-06-01

    Electronic cigarettes (E-cigarettes), or personal vaporizers, were introduced in 2003 and have been available in the United States since 2007. In addition to the health and safety concerns of the aerosol delivery of nicotine through E-cigarettes, during the past 8 years, reports of explosions and fires caused by the E-cigarette devices have led the US Fire Administration to evaluate the safety of these devices. These explosions have been observed frequently enough that the US Department of Transportation has recently banned E-cigarette devices in checked baggage aboard airplanes. This report contributes to existing knowledge about the hazards related to E-cigarettes by describing oral hard and soft tissue injuries from an E-cigarette explosion.

  19. 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

    2015-10-07

    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.

  20. Collector phase transitions during vapor-solid-solid nucleation of GaN nanowires.

    PubMed

    Chèze, Caroline; Geelhaar, Lutz; Trampert, Achim; Brandt, Oliver; Riechert, Henning

    2010-09-08

    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.

  1. 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

  2. MBMS studies of gas-phase kinetics in diamond chemical vapor deposition

    SciTech Connect

    Fox, C.A.; McMaster, M.C.; Tung, D.M.

    1995-03-01

    A molecular beam mass spectrometer system (MBMS) has been used to determine the near-surface gaseous composition involved in the low pressure chemical vapor deposition of diamond. With this system, radical and stable species can be detected with a sensitivity better than 10 ppm. Threshold ionization techniques have been employed to distinguish between radical species in the deposition environment from radical species generated by parent molecule cracking. An extensive calibration procedure was used to enable the quantitative determination of H-atom and CH{sub 3} radical mole fractions. Using the MBMS system, the gaseous composition involved in LPCVD of diamond has been measured for a wide variety of deposition conditions, including hot-filament gas activation, microwave-plasma gas activation, and a variety of precursor feed mixtures (ex: CH{sub 4}/H{sub 2}, C{sub 2}H{sub 2}/H{sub 2}). For microwave-plasma activation (MPCVD), the radical concentrations (H-atom and CH{sub 3} radicals) are independent of the identity of the precursor feed gas provided the input carbon mole fraction is constant. However, in hot-filament diamond deposition (HFCVD), the atomic hydrogen concentration decreased by an order of magnitude as the mole fraction of carbon in the precursor mixture is increased to .07; this sharp reduction has been attributed to filament poisoning of the catalytic tungsten surface via hydrocarbon deposition. Additionally, the authors find that the H-atom concentration is independent of the substrate temperature for both hot-filament and microwave plasma deposition; radial H-atom diffusion is invoked to explain this observation.

  3. 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.

  4. 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).

  5. 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.

  6. 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

  7. Liquid-vapor phase relations in the Si-O system: A calorically constrained van der Waals-type model

    NASA Astrophysics Data System (ADS)

    Connolly, James A. D.

    2016-09-01

    This work explores the use of several van der Waals (vW)-type equations of state (EoS) for predicting vaporous phase relations and speciation in the Si-O system, with emphasis on the azeotropic boiling curve of SiO2-rich liquid. Comparison with the observed Rb and Hg boiling curves demonstrates that prediction accuracy is improved if the a-parameter of the EoS, which characterizes vW forces, is constrained by ambient pressure heat capacities. All EoS considered accurately reproduce metal boiling curve trajectories, but absent knowledge of the true critical compressibility factor, critical temperatures remain uncertain by ~500 K. The EoS plausibly represent the termination of the azeotropic boiling curve of silica-rich liquid by a critical point across which the dominant Si oxidation state changes abruptly from the tetravalent state characteristic of the liquid to the divalent state characteristic of the vapor. The azeotropic composition diverges from silica toward metal-rich compositions with increasing temperature. Consequently, silica boiling is divariant and atmospheric loss after a giant impact would enrich residual silicate liquids in reduced silicon. Two major sources of uncertainty in the boiling curve prediction are the heat capacity of silica liquid, which may decay during depolymerization from the near-Dulong-Petit limit heat capacity of the ionic liquid to value characteristic of the molecular liquid, and the unknown liquid affinity of silicon monoxide. Extremal scenarios for these uncertainties yield critical temperatures and compositions of 5200-6200 K and Si1.1O2-Si1.4O2. The lowest critical temperatures are marginally consistent with shock experiments and are therefore considered more probable.

  8. Molecular simulation of water vapor-liquid phase interfaces using TIP4P/2005 model

    NASA Astrophysics Data System (ADS)

    Planková, Barbora; Vinš, Václav; Hrubý, Jan; Duška, Michal; Němec, Tomáš; Celný, 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.

  9. 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.

  10. A variational approach to the liquid-vapor phase transition for hardcore ions in the bulk and in nanopores

    NASA Astrophysics Data System (ADS)

    Loubet, Bastien; Manghi, Manoel; Palmeri, John

    2016-07-01

    We employ a field-theoretical variational approach to study the behavior of ionic solutions in the grand canonical ensemble. To describe properly the hardcore interactions between ions, we use a cutoff in Fourier space for the electrostatic contribution of the grand potential and the Carnahan-Starling equation of state with a modified chemical potential for the pressure one. We first calibrate our method by comparing its predictions at room temperature with Monte Carlo results for excess chemical potential and energy. We then validate our approach in the bulk phase by describing the classical "ionic liquid-vapor" phase transition induced by ionic correlations at low temperature, before applying it to electrolytes at room temperature confined to nanopores embedded in a low dielectric medium and coupled to an external reservoir of ions. The ionic concentration in the nanopore is then correctly described from very low bulk concentrations, where dielectric exclusion shifts the transition up to room temperature for sufficiently tight nanopores, to high concentrations where hardcore interactions dominate which, as expected, modify only slightly this ionic "capillary evaporation."

  11. 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.

  12. A variational approach to the liquid-vapor phase transition for hardcore ions in the bulk and in nanopores.

    PubMed

    Loubet, Bastien; Manghi, Manoel; Palmeri, John

    2016-07-28

    We employ a field-theoretical variational approach to study the behavior of ionic solutions in the grand canonical ensemble. To describe properly the hardcore interactions between ions, we use a cutoff in Fourier space for the electrostatic contribution of the grand potential and the Carnahan-Starling equation of state with a modified chemical potential for the pressure one. We first calibrate our method by comparing its predictions at room temperature with Monte Carlo results for excess chemical potential and energy. We then validate our approach in the bulk phase by describing the classical "ionic liquid-vapor" phase transition induced by ionic correlations at low temperature, before applying it to electrolytes at room temperature confined to nanopores embedded in a low dielectric medium and coupled to an external reservoir of ions. The ionic concentration in the nanopore is then correctly described from very low bulk concentrations, where dielectric exclusion shifts the transition up to room temperature for sufficiently tight nanopores, to high concentrations where hardcore interactions dominate which, as expected, modify only slightly this ionic "capillary evaporation."

  13. 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.

  14. 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.

  15. Properties of phase-pure InSe films prepared by metalorganic chemical vapor deposition with a single-source precursor

    NASA Astrophysics Data System (ADS)

    Choi, In-Hwan; Yu, Peter Y.

    2003-04-01

    Phase-pure InSe thin films have been prepared by a low-pressure metalorganic chemical vapor deposition technique using a single-source precursor: [(Me)2In(μ-SeMe)]2. These films have been characterized by x-ray diffraction and scanning electron microscopy and found to be single-phased and polycrystalline with a hexagonal lattice. The optical properties of the films have been studied via absorption, photoluminescence, and Raman spectroscopies.

  16. E-Cigarettes

    MedlinePlus

    ... that are known to be harmful. Scientists are studying the health effects of using e-cigarettes. New information is coming in, but they don't have the answers yet. Although FDA is working to regulate e-cigarettes, currently they are not ...

  17. 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

  18. 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.

  19. 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.

  20. Ending the cigarette pandemic.

    PubMed

    Richmond, J B

    1983-12-01

    1 year after the issuance of the original Surgeon General's report, Congress passed the Federal Cigarette Labeling Advertising Act, requiring all cigarette packages distributed in the US to carry a Surgeon General's warning that smoking may be hazardous to health. Congress pased the Public Health Cigarette Smoking Act in 1969. This banned cigarette advertising from radio and television. The Surgeon General published the most comprehensive volume on smoking ever issued in the US in 1979, the 15th anniversary of the 1st report. The data on cigarette smoking's adverse effects on health were overwhelming, and the press recognized this. No longer able to rely on journalists to cast doubt on the reliability of the data, the industry changed its strategy by attempting to portray smoking as a civil rights issue. The tobacco industry began to pour millions of dollars into campaigns to prevent the passage of municipal, state, and federal legislation that would ban cigarette advertising or restrict smoking in public places and at the work site. "Healthy People," the Surgeon General's 1st report on health promotion and disease prevention, emphasized the necessary future direction of medicine: prevention. Efforts to end the cigarette pandemic will need to focus on the following in the future: an end to the victimization of women; a greater focus on adolescents; more effective strategies for smoking cessation; more attention to clean indoor air rights; abandonment of recommendations to switch to low-tar, low-nicotine cigarettes; and revelation of chemical additives in cigarettes. The epidemiologists have now documented the devastating nature of the health problems attributable to cigarette smoking, but the minimal budgetary allocations to fight smoking testify to the lack of political will on the part of government.

  1. 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

  2. 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.

  3. 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.

  4. Structures and properties of poly(3-alkylthiophene) thin-films fabricated though vapor-phase polymerization.

    PubMed

    Back, Ji-Woong; Song, Eun-Ah; Lee, Keum-Joo; Lee, Youn-Kyung; Hwang, Chae-Ryong; Jo, Sang-Hyun; Jung, Woo-Gwang; Kim, Jin-Yeol

    2012-02-01

    Organic semiconducting polymer thin-films of 3-hexylthiophene, 3-octylthiophene, 3-decylthiophene, containing highly oriented crystal were fabricated by gas-phase polymerization using the CVD technique. These poly(3-alkylthiophene) films had a crystallinity up to 80%, and possessed a Hall mobility up to 10 cm2/Vs. The degree of crystalinity and the mobility values increased as the alkyl chain length increased. The crystal structure of the polymers was composed of stacked layers constructed by a side-by-side arrangement of alkyl chains and in-plane pi-pi stacking. These thin films are capable of being applied to organic electronics as the active materials used in thin-film transistors and organic photovoltaic cells.

  5. Chemical analysis of cigarette smoke particulate generated in the MSB-01 in vitro whole smoke exposure system.

    PubMed

    Scian, Mariano J; Oldham, Michael J; Miller, John H; Kane, David B; Edmiston, Jeffery S; McKinney, Willie J

    2009-10-01

    Cigarette mainstream smoke (MS) is a dynamic aerosol consisting of a gas-vapor phase and a particulate phase. In recent years, novel in vitro whole smoke exposure systems have been developed to expose cells directly to whole MS. One such system is the Burghart Mimic Smoker-01 (MSB-01). Our previous data using the MSB-01 indicated that a 50 +/- 10% loss of particulate matter occurred prior to MS delivery into the exposure chamber. Additionally, a change in aerosol particle diameter was also measured, suggesting that the chemical composition of MS might be changing within the system. In this study, we have expanded on our previous work and compared the particulate phase chemical composition of undiluted and diluted MS generated by the instrument and that of the MS delivered into the exposure chamber. The average percent delivery of cigarette smoke condensate (CSC) detected for all the measured chemical constituents was 35 +/- 13% for undiluted MS and 23 +/- 8% for 1:1 diluted MS. The data also indicate that under our experimental conditions, incomplete mixing of the freshly generated MS occurs during its dilution by the system. Taken together, the data presented here show that significant chemical changes occur between the generation of MS by the system and its delivery into the exposure chamber. This indicates that due to the dynamic nature of cigarette smoke, it is important to characterize the exposure conditions in order to gain the best insight and accurately correlate exposure with biological endpoints.

  6. E-cigarettes: methodological and ideological issues and research priorities.

    PubMed

    Etter, Jean-François

    2015-02-16

    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.

  7. A semi-empirical model for the complete orientation dependence of the growth rate for vapor phase epitaxy - Chloride VPE of GaAs

    NASA Technical Reports Server (NTRS)

    Seidel-Salinas, L. K.; Jones, S. H.; Duva, J. M.

    1992-01-01

    A semi-empirical model has been developed to determine the complete crystallographic orientation dependence of the growth rate for vapor phase epitaxy (VPE). Previous researchers have been able to determine this dependence for a limited range of orientations; however, our model yields relative growth rate information for any orientation. This model for diamond and zincblende structure materials is based on experimental growth rate data, gas phase diffusion, and surface reactions. Data for GaAs chloride VPE is used to illustrate the model. The resulting growth rate polar diagrams are used in conjunction with Wulff constructions to simulate epitaxial layer shapes as grown on patterned substrates. In general, this model can be applied to a variety of materials and vapor phase epitaxy systems.

  8. Liquid-vapor flow regime transitions for use in design of heat transfer loops in spacecraft: An investigation of two-phase flow in zero gravity conditions

    NASA Astrophysics Data System (ADS)

    Lovell, T. W.

    1985-05-01

    The behavior of viscous (or low velocity) two-phase vapor-liquid flow under zero gravity was simulated in the laboratory by using two immiscible fluids of equal density flowing together in a one inch diameter glass tube. The fluids used were Polypropylene Glycol (PPG) which simulated the liquid phase and water which simulated the vapor phase. Various tests were conducted varying flow rates and entrance conditions. Four existing flow regime models were analyzed, modeled on a computer, and extrapolated to predict zero-gravity conditions. The flow regimes were the Horizontal Dukler-Taitel, Vertical Dukler-Taitel, Vertical Weisman and Horizontal Weisman. None of these models when extrapolated to zero-g conditions agreed well with the lab data, and some of the observed flow regimes were not predicted at all.

  9. 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.

  10. Theoretical study of vapor-liquid homogeneous nucleation using stability analysis of a macroscopic phase.

    PubMed

    Carreón-Calderón, Bernardo

    2012-10-14

    Stability analysis is generally used to verify that the solution to phase equilibrium calculations corresponds to a stable state (minimum of the free energy). In this work, tangent plane distance analysis for stability of macroscopic mixtures is also used for analyzing the nucleation process, reconciling thus this analysis with classical nucleation theories. In the context of the revised nucleation theory, the driving force and the nucleation work are expressed as a function of the Lagrange multiplier corresponding to the mole fraction constraint from the minimization problem of stability analysis. Using a van der Waals fluid applied to a ternary mixture, Lagrange multiplier properties are illustrated. In particular, it is shown how the Lagrange multiplier value is equal to one on the binodal and spinodal curves at the same time as the driving force of nucleation vanishes on these curves. Finally, it is shown that, on the spinodal curve, the nucleation work from the revised and generalized nucleation theories are characterized by two different local minima from stability analysis, irrespective of any interfacial tension models.

  11. Liquid-vapor phase diagram and surface properties in oppositely charged colloids represented by a mixture of attractive and repulsive Yukawa potentials.

    PubMed

    Chapela, Gustavo A; del Río, Fernando; Alejandre, José

    2013-02-07

    The liquid-vapor phase diagrams of equal size diameter σ binary mixtures of screened potentials have been reported for several ranges of interaction using Monte Carlo simulation methods [J. B. Caballero, A. M. Puertas, A. Ferńandez-Barbero, F. J. de las Nieves, J. M. Romero-Enrique, and L. F. Rull, J. Chem. Phys. 124, 054909 (2006); A. Fortini, A.-P. Hynninen, and M. Dijkstra, J. Chem. Phys. 125, 094502 (2006)]. Both works report controversial results about the stability of the phase diagram with the inverse Debye screening length κ. Caballero found stability for values of κσ up to 20 while Fortini reported stability for κσ up to 20 while Fortini reported stability for κσ ≤ 4. In this work a spinodal decomposition process where the liquid and vapor phases coexist through an interface in a slab geometry is used to obtain the phase equilibrium and surface properties using a discontinuous molecular dynamics simulations for mixtures of equal size particles carrying opposite charge and interacting with a mixture of attractive and repulsive Yukawa potentials at different values of κσ. An crude estimation of the triple point temperatures is also reported. The isothermal-isobaric method was also used to determine the phase stability using one phase simulations. We found that liquid-vapor coexistence is stable for values of κσ > 20 and that the critical temperatures have a maximum value at around κσ = 10, in agreement with Caballero et al. calculations. There also exists a controversy about the liquid-vapor envelope stability of the pure component attractive Yukawa model which is also discussed in the text. In addition, details about the equivalence between continuous and discontinuous molecular dynamics simulations are given, in the Appendix, for Yukawa and Lennard-Jones potentials.

  12. Liquid-vapor phase diagram and surface properties in oppositely charged colloids represented by a mixture of attractive and repulsive Yukawa potentials

    NASA Astrophysics Data System (ADS)

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

    2013-02-01

    The liquid-vapor phase diagrams of equal size diameter σ binary mixtures of screened potentials have been reported for several ranges of interaction using Monte Carlo simulation methods [J. B. Caballero, A. M. Puertas, A. Ferńandez-Barbero, F. J. de las Nieves, J. M. Romero-Enrique, and L. F. Rull, J. Chem. Phys. 124, 054909 (2006), 10.1063/1.2159481; A. Fortini, A.-P. Hynninen, and M. Dijkstra, J. Chem. Phys. 125, 094502 (2006), 10.1063/1.2335453]. Both works report controversial results about the stability of the phase diagram with the inverse Debye screening length κ. Caballero found stability for values of κσ up to 20 while Fortini reported stability for κσ up to 20 while Fortini reported stability for κσ ⩽ 4. In this work a spinodal decomposition process where the liquid and vapor phases coexist through an interface in a slab geometry is used to obtain the phase equilibrium and surface properties using a discontinuous molecular dynamics simulations for mixtures of equal size particles carrying opposite charge and interacting with a mixture of attractive and repulsive Yukawa potentials at different values of κσ. An crude estimation of the triple point temperatures is also reported. The isothermal-isobaric method was also used to determine the phase stability using one phase simulations. We found that liquid-vapor coexistence is stable for values of κσ > 20 and that the critical temperatures have a maximum value at around κσ = 10, in agreement with Caballero et al. calculations. There also exists a controversy about the liquid-vapor envelope stability of the pure component attractive Yukawa model which is also discussed in the text. In addition, details about the equivalence between continuous and discontinuous molecular dynamics simulations are given, in the Appendix, for Yukawa and Lennard-Jones potentials.

  13. Phase Transition Enthalpy Measurements of Organic and Organometallic Compounds and Ionic Liquids. Sublimation, Vaporization, and Fusion Enthalpies from 1880 to 2015. Part 2. C11-C192

    NASA Astrophysics Data System (ADS)

    Acree, William; Chickos, James S.

    2017-03-01

    The second part of this compendium concludes with a collection of phase change enthalpies of organic molecules inclusive of C11-C192 reported over the period 1880-2015. Also included are phase change enthalpies including fusion, vaporization, and sublimation enthalpies for organometallic, ionic liquids, and a few inorganic compounds. Paper I of this compendium, published separately, includes organic compounds from C1 to C10 and describes a group additivity method for evaluating solid, liquid, and gas phase heat capacities as well as temperature adjustments of phase changes. Paper II of this compendium also includes an updated version of a group additivity method for evaluating total phase change entropies which together with the fusion temperature can be useful in estimating total phase change enthalpies. Other uses include application in identifying potential substances that either form liquid or plastic crystals or exhibit additional phase changes such as undetected solid-solid transitions or behave anisotropically in the liquid state.

  14. Controlled Vapor Phase Growth of Single Crystalline, Two-Dimensional GaSe Crystals with High Photoresponse

    PubMed Central

    Li, Xufan; Lin, Ming-Wei; Puretzky, Alexander A.; Idrobo, Juan C.; Ma, Cheng; Chi, Miaofang; Yoon, Mina; Rouleau, Christopher M.; Kravchenko, Ivan I.; Geohegan, David B.; Xiao, Kai

    2014-01-01

    Compared with their bulk counterparts, atomically thin two-dimensional (2D) crystals exhibit new physical properties, and have the potential to enable next-generation electronic and optoelectronic devices. However, controlled synthesis of large uniform monolayer and multi-layer 2D crystals is still challenging. Here, we report the controlled synthesis of 2D GaSe crystals on SiO2/Si substrates using a vapor phase deposition method. For the first time, uniform, large (up to ~60 μm in lateral size), single-crystalline, triangular monolayer GaSe crystals were obtained and their structure and orientation were characterized from atomic scale to micrometer scale. The size, density, shape, thickness, and uniformity of the 2D GaSe crystals were shown to be controllable by growth duration, growth region, growth temperature, and argon carrier gas flow rate. The theoretical modeling of the electronic structure and Raman spectroscopy demonstrate a direct-to-indirect bandgap transition and progressive confinement-induced bandgap shifts for 2D GaSe crystals. The 2D GaSe crystals show p-type semiconductor characteristics and high photoresponsivity (~1.7 A/W under white light illumination) comparable to exfoliated GaSe nanosheets. These 2D GaSe crystals are potentially useful for next-generation electronic and optoelectronic devices such as photodetectors and field-effect transistors. PMID:24975226

  15. Dependence of polarity inversion on V/III ratio in -c-GaN growth by oxide vapor phase epitaxy

    NASA Astrophysics Data System (ADS)

    Taniyama, Yuki; Yamaguchi, Yohei; Takatsu, Hiroaki; Sumi, Tomoaki; Kitamoto, Akira; Imade, Mamoru; Yoshimura, Masashi; Isemura, Masashi; Mori, Yusuke

    2016-05-01

    One of the issues in bulk c-GaN growth is the decrease in the diameter of crystals with an increase in thickness owing to the appearance of inclined \\{ 10\\bar{1}1\\} and \\{ 10\\bar{1}2\\} facets. In this study, we performed -c-GaN growth by oxide vapor phase epitaxy (OVPE). As a result, truncated-inverted-pyramidal crystals were successfully grown on dot-patterned -c-GaN substrates. The diameter of the top surface of crystals was larger than that of windows. We further investigated the dependence of the ratio of inversion-domain area to growth area (R ID) on growth temperature, V/III ratio, and growth rate. The remained results revealed that R ID decreased with increasing growth temperature and V/III ratio, and kept constant for growth rate. Additionally, an epitaxial layer on -c-GaN substrates with a growth rate of 12.4 µm/h and an R ID as low as 3.8% was obtained under an NH3 partial pressure (P NH3) of 83 kPa at 1200 °C.

  16. Low-temperature emission in dilute GaAsN alloys grown by metalorganic vapor phase epitaxy

    NASA Astrophysics Data System (ADS)

    Bentoumi, G.; Yaïche, Z.; Leonelli, R.; Beaudry, J.-N.; Desjardins, P.; Masut, R. A.

    2008-03-01

    We have investigated the optical emission from GaAs1-xNx epilayers with 4.3×10-4vapor phase epitaxy using dimethylhydrazine as the nitrogen precursor. We find that the incorporation of nitrogen in GaAs generates deep radiative centers at around 250meV below the GaAsN band gap. The defects associated with these centers can be eliminated through an optimization of the growth temperature and reactor pressure, and by postgrowth annealing at 700°C. We also find that, contrary to what was suggested by Makimoto et al. [Appl. Phys. Lett. 70, 2984 (1997)], the near-gap emission located close to 25meV below the gap is not related to a free-to-bound transition even in the samples with the lowest nitrogen content. Rather, we associate this emission to excitons bound to overlapping nitrogen clusters.

  17. Vapor-phase toxicity of Derris scandens Benth.-derived constituents against four stored-product pests.

    PubMed

    Hymavathi, Atmakur; Devanand, Peta; Suresh Babu, Katragadda; Sreelatha, Thonthula; Pathipati, Usha Rani; Madhusudana Rao, Janaswamy

    2011-03-09

    The vapor-phase toxicity of Derris scandens Benth.-derived constituents was evaluated against four stored-product pests ( Callosobruchus chinensis L., Sitophilus oryzae L., Rhyzopertha dominica L., and Tribolium castaneum H.) using fumigation bioassays and compared to those of commonly used insecticides. The structures of all constituents of were characterized by spectroscopic analyses [nuclear magnetic resonance (NMR) and mass spectrometry]. The sensitivity of the test insect to compounds varied with exposure time, concentration, and insect species. Over 100% mortality after 24 h was achieved with the compounds osajin (2), scandinone (5), sphaerobioside (8), and genistein (9) against all of the test insects, while laxifolin (3) and lupalbigenin (4) showed 100% mortality after 72 h against T. csataneum and R. dominica . Scandenone (1), scandenin A (6), and scandenin (7) were less effective. Among the insects, C. chinensis , S. oryzae , and R. dominica were more susceptible to the treatments, whereas T. castaneum was less susceptible. The results of fumigation tests indicated that compounds from D. scandens whole plant extract are potential candidates to control stored-product pests.

  18. Selective-area growth of GaN microrods on strain-induced templates by hydride vapor phase epitaxy

    NASA Astrophysics Data System (ADS)

    Lekhal, Kaddour; Bae, Si-Young; Lee, Ho-Jun; Mitsunari, Tadashi; Tamura, Akira; Deki, Manato; Honda, Yoshio; Amano, Hiroshi

    2016-05-01

    In this paper, we discuss the influence of parameters such as type of carrier gas and NH3/HCl flow ratio on the growth of vertical GaN microstructures by selective-area growth (SAG) hydride vapor phase epitaxy (HVPE). On various strain-induced templates such as GaN/sapphire, GaN/Si, and AlN/Si, regular arrays of Ga-polar GaN microrods were properly achieved by adjusting the growth parameters. The photoluminescence and micro-Raman measurements reveal not only the crystal quality of the GaN microrods but also strain distribution. These results will give insight into the control of the morphology of GaN microrods in terms of the strain induced from templates in SAG-HVPE. The precisely controlled arrays of GaN microrods can be used for next-generation light-emitting diodes (LEDs) by realizing InGaN/GaN multi-quantum wells (MQWs) with a radial structure.

  19. Metalorganic chemical vapor phase epitaxy of narrow-band distributed Bragg reflectors realized by GaN:Ge modulation doping

    NASA Astrophysics Data System (ADS)

    Berger, Christoph; Lesnik, Andreas; Zettler, Thomas; Schmidt, Gordon; Veit, Peter; Dadgar, Armin; Bläsing, Jürgen; Christen, Jürgen; Strittmatter, André

    2016-04-01

    We report on metalorganic vapor phase epitaxy (MOVPE) of distributed Bragg reflectors (DBR) applying a periodic modulation of the GaN doping concentration only. The doping modulation changes the refractive index of GaN via the Burstein-Moss-effect. MOVPE growth of highly doped GaN:Ge and modulation of the dopant concentration by at least two orders of magnitude within few nanometers is required to achieve a refractive index contrast of 2-3%. Such modulation characteristic is achieved despite the presence of Ge memory effects and incorporation delay. We realized DBRs with up to 100 layer pairs by combining GaN:Ge with a nominal doping concentration of 1.6×1020 cm-3 as low-refractive index material with unintentionally doped GaN as high-refractive index layer. Scanning transmission electron microscope images reveal DBR structures with abrupt interfaces and homogenous layer thicknesses in lateral and vertical direction. Reflectance measurements of DBRs designed for the blue and near UV-spectral region show a narrow stopband with a maximum reflectivity of 85% at 418 nm and even 95% at 370 nm. InGaN/GaN multi-quantum well structures grown on top of such DBRs exhibit narrow emission spectra with linewidths below 3 nm and significantly increased emission intensity.

  20. Impact of thermal annealing on bulk InGaAsSbN materials grown by metalorganic vapor phase epitaxy

    SciTech Connect

    Kim, T. W.; Mawst, L. J.; Kim, K.; Lee, J. J.; Kuech, T. F.; Wells, N. P.; LaLumondiere, S. D.; Sin, Y.; Lotshaw, W. T.; Moss, S. C.

    2014-02-03

    Two different thermal annealing techniques (rapid thermal annealing (RTA) and in-situ post-growth annealing in the metalorganic vapor phase epitaxy (MOVPE) chamber) were employed to investigate their impact on the optical characteristics of double-heterostructures (DH) of InGaAsSbN/GaAs and on the performance of single-junction solar cell structures, all grown by MOVPE. We find that an optimized RTA procedure leads to a similar improvement in the photoluminescence (PL) intensity compared with material employing a multi-step optimized anneal within the MOVPE reactor. Time-resolved photoluminescence techniques at low temperature (LT) and room temperature (RT) were performed to characterize the carrier dynamics in bulk InGaAsSbN layers. Room temperature carrier lifetimes were found to be similar for both annealing methods, although the LT-PL (16 K) measurements of the MOVPE-annealed sample found longer lifetimes than the RTA-annealed sample (680 ps vs. 260 ps) for the PL measurement energy of 1.24 eV. InGaAsSbN-based single junction solar cells processed with the optimized RTA procedure exhibited an enhancement of the electrical performance, such as improvements in open circuit voltage, short circuit current, fill factor, and efficiency over solar cells subjected to the in-situ MOVPE annealing technique.

  1. Defects responsible for lifetime degradation in electron irradiated n-GaN grown by hydride vapor phase epitaxy

    NASA Astrophysics Data System (ADS)

    Lee, In-Hwan; Polyakov, A. Y.; Yakimov, E. B.; Smirnov, N. B.; Shchemerov, I. V.; Tarelkin, S. A.; Didenko, S. I.; Tapero, K. I.; Zinovyev, R. A.; Pearton, S. J.

    2017-03-01

    The effects of room temperature 6 MeV electron irradiation on the donor concentration, deep trap spectra, and diffusion lengths of nonequilibrium charge carriers were studied for undoped n-GaN grown by hydride vapor phase epitaxy. Changes in these parameters begin at a threshold electron fluence of 5 × 1015 cm-2. The diffusion lengths after this fluence decrease by a factor of 3, accompanied by a drastic increase in the density of deep electron traps with the level near Ec - 1 eV. There is a strong correlation between the changes in the density of these traps and the diffusion length of irradiated n-GaN, indicating that these centers control the lifetime in radiation damaged n-GaN. This is in sharp contrast to the starting material, where the lifetimes are controlled by other deep electron traps at Ec - 0.56 eV. The concentration of the latter is not strongly affected by high energy electron irradiation.

  2. Controlled Vapor Phase Growth of Single Crystalline, Two-Dimensional GaSe Crystals with High Photoresponse

    SciTech Connect

    Li, Xufan; Lin, Ming-Wei; Zhang, Huidong; Puretzky, Alexander A; Idrobo Tapia, Juan C; Ma, Cheng; Chi, Miaofang; Yoon, Mina; Rouleau, Christopher M; Kravchenko, Ivan I; Geohegan, David B; Xiao, Kai

    2014-01-01

    Abstract Compared with their bulk counterparts, atomically thin two-dimensional (2D) crystals exhibit new physical properties, and have the potential to enable next-generation electronic and optoelectronic devices. However, controlled synthesis of large uniform monolayer and multi-layer 2D crystals is still challenging. Here, we report the controlled synthesis of 2D GaSe crystals on SiO2/Si substrates using a vapor phase deposition method. For the first time, uniform, large (up to ~60 m in lateral size), single-crystalline, triangular monolayer GaSe crystals were obtained and their atomic resolution structure were characterized. The size, density, shape, thickness, and uniformity of the 2D GaSe crystals were shown to be controllable by growth duration, growth region, growth temperature, and argon carrier gas flow rate. The theoretical modeling of the electronic structure and Raman spectroscopy demonstrate a direct-to-indirect bandgap transition and progressive confinement-induced bandgap shifts for 2D GaSe crystals. The 2D GaSe crystals show p-type semiconductor characteristics and high photoresponsivity (~1.7 A/W under white light illumination) comparable to exfoliated GaSe nanosheets. These 2D GaSe crystals are potentially useful for next-generation electronic and optoelectronic devices such as photodetectors and field-effect transistors.

  3. Controlled vapor phase growth of single crystalline, two-dimensional GaSe crystals with high photoresponse.

    PubMed

    Li, Xufan; Lin, Ming-Wei; Puretzky, Alexander A; Idrobo, Juan C; Ma, Cheng; Chi, Miaofang; Yoon, Mina; Rouleau, Christopher M; Kravchenko, Ivan I; Geohegan, David B; Xiao, Kai

    2014-06-30

    Compared with their bulk counterparts, atomically thin two-dimensional (2D) crystals exhibit new physical properties, and have the potential to enable next-generation electronic and optoelectronic devices. However, controlled synthesis of large uniform monolayer and multi-layer 2D crystals is still challenging. Here, we report the controlled synthesis of 2D GaSe crystals on SiO2/Si substrates using a vapor phase deposition method. For the first time, uniform, large (up to ~60 μm in lateral size), single-crystalline, triangular monolayer GaSe crystals were obtained and their structure and orientation were characterized from atomic scale to micrometer scale. The size, density, shape, thickness, and uniformity of the 2D GaSe crystals were shown to be controllable by growth duration, growth region, growth temperature, and argon carrier gas flow rate. The theoretical modeling of the electronic structure and Raman spectroscopy demonstrate a direct-to-indirect bandgap transition and progressive confinement-induced bandgap shifts for 2D GaSe crystals. The 2D GaSe crystals show p-type semiconductor characteristics and high photoresponsivity (~1.7 A/W under white light illumination) comparable to exfoliated GaSe nanosheets. These 2D GaSe crystals are potentially useful for next-generation electronic and optoelectronic devices such as photodetectors and field-effect transistors.

  4. Single-step metal-organic vapor-phase diffusion for low-dark-current planar-type avalanche photodiodes

    NASA Astrophysics Data System (ADS)

    Jun, Dong-Hwan; Jeong, Hae Yong; Kim, Youngjo; Shin, Chan-Soo; Park, Kyung Ho; Park, Won-Kyu; Kim, Min-Su; Kim, Sangin; Han, Sang Wook; Moon, Sung

    2016-10-01

    In this paper, a p-type diffusion process based literally on single-step metal-organic vapor-phase diffusion (MOVPD) employing diethyl zinc as the diffusion source in combination with the recessetching technique is developed to improve the dark-current characteristics of planar-type avalanche photodiodes (APDs). The developed single-step MOVPD process exhibits on excellent linear relationship between the diffusion depth and the square root of the diffusion time, which mainly results from maintaining constant source diffusion. The single-step MOVPD process without any additional thermal activation process achieves a surface doping concentration of 1.9 × 1018 cm -3, which is sufficient to form ohmic contact. The measured diffusion profiles of the APDs clearly reveal the presence of a two-dimensional diffusion front formed by the recess-etched and guard-ring regions. The impact of this p-type diffusion process on the performance of the APD devices has also been demonstrated by exhibiting improved dark-current characteristics for the fabricated APDs.

  5. High rate growth of In2O3 at 1000 °C by halide vapor phase epitaxy

    NASA Astrophysics Data System (ADS)

    Togashi, Rie; Numata, Shiyu; Hayashida, Mayuko; Suga, Takayuki; Goto, Ken; Kuramata, Akito; Yamakoshi, Shigenobu; Paskov, Plamen; Monemar, Bo; Kumagai, Yoshinao

    2016-12-01

    In this work, the first-ever growth of cubic-In2O3 at 1000 °C by halide vapor phase epitaxy (HVPE) was achieved, using gaseous InCl and O2 as precursors in a N2 flow. The growth rates of In2O3 layers on (001) β-Ga2O3 and (0001) sapphire substrates were 4.1 and 5.1 µm/h, respectively, even at the high growth temperature applied, which are approximately half the growth rate of β-Ga2O3 homoepitaxially grown by HVPE at 1000 °C. Theoretical thermodynamic analyses were also conducted, and results confirmed the growth of In2O3 at temperatures above 1000 °C by HVPE. The as-grown In2O3 layers were light yellow-green in color. The In2O3 layers grown on the (001) β-Ga2O3 and (0001) sapphire substrates exhibited an optical absorption edge at about 370 nm, in addition to n-type conductivity with electron concentrations of 2.7 × 1018 and 1.7 × 1018 cm-3, and electron mobilities of 16.2 and 22.7 cm2 V-1 s-1, respectively.

  6. Determination of methyl mercury by aqueous phase Eehylation, followed by gas chromatographic separation with cold vapor atomic fluorescence detection

    USGS Publications Warehouse

    De Wild, John F.; Olsen, Mark L.; Olund, Shane D.

    2002-01-01

    A recent national sampling of streams in the United States revealed low methyl mercury concentrations in surface waters. The resulting median and mean concentrations, calculated from 104 samples, were 0.06 nanograms per liter (ng/L) and 0.15 ng/L, respectively. This level of methyl mercury in surface water in the United States has created a need for analytical techniques capable of detecting sub-nanogram per liter concentrations. In an attempt to create a U.S. Geological Survey approved method, the Wisconsin District Mercury Laboratory has adapted a distillation/ethylation/ gas-phase separation method with cold vapor atomic fluorescence spectroscopy detection for the determination of methyl mercury in filtered and unfiltered waters. This method is described in this report. Based on multiple analyses of surface water and ground-water samples, a method detection limit of 0.04 ng/L was established. Precision and accuracy were evaluated for the method using both spiked and unspiked ground-water and surface-water samples. The percent relative standard deviations ranged from 10.2 to 15.6 for all analyses at all concentrations. Average recoveries obtained for the spiked matrices ranged from 88.8 to 117 percent. The precision and accuracy ranges are within the acceptable method-performance limits. Considering the demonstrated detection limit, precision, and accuracy, the method is an effective means to quantify methyl mercury in waters at or below environmentally relevant concentrations

  7. Growth of GaN epitaxial films on polycrystalline diamond by metal-organic vapor phase epitaxy

    NASA Astrophysics Data System (ADS)

    Jiang, Quanzhong; Allsopp, Duncan W. E.; Bowen, Chris R.

    2017-04-01

    Heat extraction is often essential in ensuring efficient performance of semiconductor devices and requires minimising the thermal resistance between the functional semiconductor layers and any heat sink. This paper reports the epitaxial growth of N-polar GaN films on polycrystalline diamond substrates of high thermal conductivity with metal-organic vapor phase epitaxy, by using a Si x C layer formed during deposition of polycrystalline diamond on a silicon substrate. The Si x C layer acts to provide the necessary structure ordering information for the formation of a single crystal GaN film at the wafer scale. It is shown that a three-dimensional island (3D) growth process removes hexagonal defects that are induced by the non-single crystal nature of the Si x C layer. It is also shown that intensive 3D growth and the introduction of a convex curvature of the substrate can be deployed to reduce tensile stress in the GaN epitaxy to enable the growth of a crack-free layer up to a thickness of 1.1µm. The twist and tilt can be as low as 0.65° and 0.39° respectively, values broadly comparable with GaN grown on Si substrates with a similar structure.

  8. Ar{sup +}-irradiation-induced damage in hydride vapor-phase epitaxy GaN films

    SciTech Connect

    Nakano, Yoshitaka Ogawa, Daisuke; Nakamura, Keiji; Kawakami, Retsuo; Niibe, Masahito

    2015-07-15

    The authors have investigated the electrical characteristics of hydride vapor-phase epitaxy GaN films exposed to Ar{sup +} irradiation, employing Schottky barrier diodes. The Ar{sup +} irradiation tends to largely increase the effective carrier concentration in the near surface region of GaN up to ∼25 nm, due to the generation of donor-type N vacancy defects, compared to the original value before the irradiation. More interestingly, acceptor-type deep-level defects are found to be formed at ∼2.1, ∼2.9, and ∼3.2 eV below the conduction band in the subsequently deeper region, in which Ga vacancies introduced by the Ar{sup +} irradiation are considered to be in-diffused and immediately combined with hydrogen. These N vacancies and hydrogenated Ga vacancies formed are dominantly responsible for changing the depth profiles of the effective carrier concentration via the carrier generation, the carrier trapping, and/or carrier compensation.

  9. Vapor-Phase-Gating-Induced Ultrasensitive Ion Detection in Graphene and Single-Walled Carbon Nanotube Networks.

    PubMed

    Hao, Ji; Li, Bo; Jung, Hyun Young; Liu, Fangze; Hong, Sanghyun; Jung, Yung Joon; Kar, Swastik

    2017-04-10

    Designing ultrasensitive detectors often requires complex architectures, high-voltage operations, and sophisticated low-noise measurements. In this work, it is shown that simple low-bias two-terminal DC-conductance values of graphene and single-walled carbon nanotubes are extremely sensitive to ionized gas molecules. Incident ions form an electrode-free, dielectric- or electrolyte-free, bias-free vapor-phase top-gate that can efficiently modulate carrier densities up to ≈0.6 × 10(13) cm(-2) . Surprisingly, the resulting current changes are several orders of magnitude larger than that expected from conventional electrostatic gating, suggesting the possible role of a current-gain inducing mechanism similar to those seen in photodetectors. These miniature detectors demonstrate charge-current amplification factor values exceeding 10(8) A C(-1) in vacuum with undiminished responses in open air, and clearly distinguish between positive and negative ions sources. At extremely low rates of ion incidence, detector currents show stepwise changes with time, and calculations suggest that these stepwise changes can result from arrival of individual ions. These sensitive ion detectors are used to demonstrate a proof-of-concept low-cost, amplifier-free, light-emitting-diode-based low-power ion-indicator.

  10. Vapor-phase atomic-controllable growth of amorphous Li2S for high-performance lithium-sulfur batteries.

    PubMed

    Meng, Xiangbo; Comstock, David J; Fister, Timothy T; Elam, Jeffrey W

    2014-10-28

    Lithium-sulfur (Li-S) batteries hold great promise to meet the formidable energy storage requirements of future electrical vehicles but are prohibited from practical implementation by their severe capacity fading and the risks imposed by Li metal anodes. Nanoscale Li(2)S offers the possibility to overcome these challenges, but no synthetic technique exists for fine-tailoring Li(2)S at the nanoscale. Herein we report a vapor-phase atomic layer deposition (ALD) method for the atomic-scale-controllable synthesis of Li(2)S. Besides a comprehensive investigation of the ALD Li(2)S growth mechanism, we further describe the high performance of the resulting amorphous Li(2)S nanofilms as cathodes in Li-S batteries, achieving a stable capacity of ∼ 800 mA · h/g, nearly 100% Coulombic efficiency, and excellent rate capability. Nanoscale Li(2)S holds great potential for both bulk-type and thin-film high-energy Li-S batteries.

  11. Mechanism of arsenic incorporation and electrical properties in CdTe layers grown by metalorganic vapor phase epitaxy

    NASA Astrophysics Data System (ADS)

    Ekawa, Mitsuru; Yasuda, Kazuhito; Ferid, Touati; Saji, Manabu; Tanaka, Akikazu

    1992-03-01

    The As doping mechanism in (100) CdTe layers grown on (100) GaAs by atmospheric-pressure metalorganic vapor phase epitaxy was studied. Triethylarsine (TEAs) was used as a dopant source. The source materials used were dimethylcadmium (DMCd) and diethyltelluride (DETe). The As incorporation was enhanced by decreasing the DETe flow rate under a fixed DMCd flow condition, and by lowering the growth temperature. Assuming 100% activation of As, the As incorporation efficiency was estimated to be about 0.1%. The As incorporation was dominated by the sticking rate of the As species onto the Cd species. The hole concentration was controlled from 2×1015 to 3×1016 cm-3 in proportion to the TEAs flow rate below 1×10-7 mol/min. Those doped layers showed hole mobilities as high as 75 cm2/V s. Low-temperature photoluminescence (PL) studies revealed that a neutral-acceptor bound-exciton at 1.5901 eV is due to a substitutional As acceptor on the Te site. The As ionization energy was about 90 meV from the PL and electrical measurements.

  12. Nanopipe formation as a result of boron impurity segregation in gallium nitride grown by halogen-free vapor phase epitaxy

    NASA Astrophysics Data System (ADS)

    Kimura, Taishi; Aoki, Yuko; Horibuchi, Kayo; Nakamura, Daisuke

    2016-12-01

    The work reported herein demonstrated that nanopipes can be formed via a surfactant effect, in which boron impurities preferentially migrate to semipolar and nonpolar facets. Approximately 3 μm-thick GaN layers were grown using halogen-free vapor phase epitaxy. All layers grown in pyrolytic boron nitride (pBN) crucibles were found to contain a high density of nanopipes in the range of 1010 to 1011 cm-2. The structural properties of these nanopipes were analyzed by X-ray rocking curve measurements, transmission electron microscopy, and three-dimensional atom probe (3DAP) tomography. The resulting 3DAP maps showed nanopipe-sized regions of boron segregation, and these nanopipes were not associated with the presence of dislocations. A mechanism for nanopipe formation was developed based on the role of boron as a surfactant and considering energy minima. A drastic reduction in the nanopipe density was achieved upon replacing the pBN crucibles with tantalum carbide-coated carbon crucibles. Consequently, we have confirmed that nanopipes can be formed solely due to surface energy changes induced by boron impurity surface segregation. For this reason, these results also indicate that nanopipes should be formed by other surfactant impurities such as Mg and Si.

  13. All metalorganic chemical vapor phase epitaxy of p/n-GaN tunnel junction for blue light emitting diode applications

    NASA Astrophysics Data System (ADS)

    Neugebauer, S.; Hoffmann, M. P.; Witte, H.; Bläsing, J.; Dadgar, A.; Strittmatter, A.; Niermann, T.; Narodovitch, M.; Lehmann, M.

    2017-03-01

    We report on III-Nitride blue light emitting diodes (LEDs) comprising a GaN-based tunnel junction (TJ) all realized by metalorganic vapor phase epitaxy in a single growth process. The TJ grown atop the LED structures consists of a Mg-doped GaN layer and subsequently grown highly Ge-doped GaN. Long thermal annealing of 60 min at 800 °C is important to reduce the series resistance of the LEDs due to blockage of acceptor-passivating hydrogen diffusion through the n-type doped top layer. Secondary ion mass spectroscopy measurements reveal Mg-incorporation into the topmost GaN:Ge layer, implying a non-abrupt p-n tunnel junction and increased depletion width. Still, significantly improved lateral current spreading as compared to conventional semi-transparent Ni/Au p-contact metallization and consequently a more homogeneous electroluminescence distribution across 1 × 1 mm2 LED structures is achieved. Direct estimation of the depletion width is obtained from electron holography experiments, which allows for a discussion of the possible tunneling mechanism.

  14. In situ spectroscopic studies on vapor phase catalytic decomposition of dimethyl oxalate.

    PubMed

    Hegde, Shweta; Tharpa, Kalsang; Akuri, Satyanarayana Reddy; K, Rakesh; Kumar, Ajay; Deshpande, Raj; Nair, Sreejit A

    2017-03-15

    Dimethyl Oxalate (DMO) has recently gained prominence as a valuable intermediate for the production of compounds of commercial importance. The stability of DMO is poor and hence this can result in the decomposition of DMO under reaction conditions. The mechanism of DMO decomposition is however not reported and more so on catalytic surfaces. Insights into the mechanism of decomposition would help in designing catalysts for its effective molecular transformation. It is well known that DMO is sensitive to moisture, which can also be a factor contributing to its decomposition. The present work reports the results of decomposition of DMO on various catalytic materials. The materials studied consist of acidic (γ-Al2O3), basic (MgO), weakly acidic (ZnAl2O4) and neutral surfaces such as α-Al2O3 and mesoporous precipitated SiO2. Infrared spectroscopy is used to identify the nature of adsorption of the molecule on the various surfaces. The spectroscopy study is done at a temperature of 200 °C, which is the onset of gas phase decomposition of DMO. The results indicate that the stability of DMO is lower than the corresponding acid, i.e. oxalic acid. It is also one of the products of decomposition. Spectroscopic data suggest that DMO decomposition is related to surface acidity and the extent of decomposition depends on the number of surface hydroxyl groups. Decomposition was also observed on α-Al2O3, which was attributed to the residual surface hydroxyl groups. DMO decomposition to oxalic acid was not observed on the basic surface (MgO).

  15. 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

    2015-11-20

    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.

  16. 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

  17. Vapor-phase testing of the memory-effects in benzene- and toluene-imprinted polymers conditioned at elevated temperature.

    PubMed

    Azenha, Manuel; Schillinger, Eric; Sanmartin, Esther; Regueiras, M Teresa; Silva, Fernando; Sellergren, Börje

    2013-11-13

    The preparation of polymers imprinted with common aromatic solvents such as benzene and toluene is an under-exploited subject of research. The present study was aimed at the understanding of whether true solvent memory effects can be achieved by molecular imprinting, as well as if they are stable at elevated temperature. A set of copolymers, comprising low and high cross-linking levels, was prepared from four different combinations of functional monomer and cross-linker, namely methacrylic acid (MAA)/ethylene glycol dimethacrylate (EGDMA), methyl methacrylate (MMA)/EGDMA, MAA/divinyl benzene (DVB) and MMA/DVB. Each possible combination was prepared separately in benzene, toluene and acetonitrile. The obtained materials were applied as coatings onto nickel-titanium (Ni-Ti) alloy wires which were incorporated into solid-phase microextraction devices and finally tested for their ability to competitively adsorb vapors from the headspace of an aqueous solution containing a few volatile organic compounds. Porosity analysis showed that, regardless of the solvent used, only a high cross-linking level permitted the preparation of mesoporous copolymers (BJH radius typically in the range 13-15 nm), a requirement for providing accessibility to the targeted nanoscale-imprinted cavities. A noticeable exception was, however, observed for the MMA/DVB copolymers which exhibited much diminished BJH radius. The porosity data correlated well with the extraction profiles found, which suggested the presence of benzene-imprinted sites in all the highly cross-linked copolymers prepared in benzene, except for the MMA/DVB copolymers. Concerning the effect of an elevated conditioning temperature on the memory-effects created by the imprinting process, the results were clearly indicative that the tested copolymers, including the more robust highly cross-linked ones, are not suitable for high temperature applications such as solid-phase microextraction coupled to gas chromatography.

  18. Electronic cigarettes induce DNA strand breaks and cell death independently of nicotine in cell lines

    PubMed Central

    Yu, Vicky; Rahimy, Mehran; Korrapati, Avinaash; Xuan, Yinan; Zou, Angela E.; Krishnan, Aswini R.; Tsui, Tzuhan; Aguilera, Joseph A.; Advani, Sunil; Crotty Alexander, Laura E.; Brumund, Kevin T.; Wang-Rodriguez, Jessica

    2016-01-01

    Objectives Evaluate the cytotoxicity and genotoxicity of short- and long-term e-cigarette vapor exposure on a panel of normal epithelial and head and neck squamous cell carcinoma (HNSCC) cell lines. Materials and Methods HaCaT, UMSCC10B, and HN30 were treated with nicotine-containing and nicotine-free vapor extract from two popular e-cigarette brands for periods ranging from 48 hours to 8 weeks. Cytotoxicity was assessed using Annexin V flow cytometric analysis, trypan blue exclusion, and clonogenic assays. Genotoxicity in the form of DNA strand breaks was quantified using the neutral comet assay and γ-H2AX immunostaining. Results E-cigarette-exposed cells showed significantly reduced cell viability and clonogenic survival, along with increased rates of apoptosis and necrosis, regardless of e-cigarette vapor nicotine content. They also exhibited significantly increased comet tail length and accumulation of γ-H2AX foci, demonstrating increased DNA strand breaks. Conclusion E-cigarette vapor, both with and without nicotine, is cytotoxic to epithelial cell lines and is a DNA strand break-inducing agent. Further assessment of the potential carcinogenic effects of e-cigarette vapor is urgently needed. PMID:26547127

  19. Heme oxygenase-1 gene expression in human alveolar epithelial cells (A549) following exposure to whole cigarette smoke on a direct in vitro exposure system.

    PubMed

    Fukano, Yasuo; Yoshimura, Hiroyuki; Yoshida, Takemi

    2006-07-01

    Many in vitro studies have employed cigarette smoke condensates or soluble smoke components to investigate the biological effects of cigarette smoke. However, neither of these methods evaluates the biological effects of fresh whole cigarette smoke. It is most desirable to conduct in vitro biological studies under conditions which accommodate the dynamic physicochemical character of fresh cigarette smoke. Previously we reported the development of a whole smoke exposure system to assess the biological effects of mainstream cigarette smoke. The exposure system design was based on a combination of the sedimentation procedure and the CULTEX cultivation technique, which includes a systemized air/liquid interface methodology and exposes the cells to fresh smoke at every puff. The aim of this study was to adopt the other biological endpoint to our whole smoke exposure system. We focused on heme oxygenase (HO)-1 mRNA gene expression, an enzyme which has recently been shown to be highly responsible for oxidative stress. In the present study, a dose-response relationship between the HO-1 mRNA expression based on the reverse transcription real-time PCR method and total exposure to cigarette smoke was observed. When a Cambridge filter pad was placed between the cigarette and exposure module, to ensure the cells were only exposed to the gas/vapor phase, the latter, as well as the whole smoke, induced HO-1 mRNA dose dependently. For the next step, acetate plain and charcoal filters with the same pressure drop were prepared to assess the potential ability of charcoal filters with regard to the vapor phase performance. The results revealed reduced HO-1 mRNA gene expression when a charcoal filter was used. Direct whole smoke exposure is a significant approach and may reflect the conditions of exposure essentially resulting from direct contact between cells and a dynamic mixture of gaseous and particulate constituents. We were able to adopt a gene expression assay for oxidative

  20. Hot wire chemical vapor deposition chemistry in the gas phase and on the catalyst surface with organosilicon compounds.

    PubMed

    Shi, Yujun

    2015-02-17

    CONSPECTUS: Hot wire chemical vapor deposition (HWCVD), also referred to as catalytic CVD (Cat-CVD), has been used to produce Si-containing thin films, nanomaterials, and functional polymer coatings that have found wide applications in microelectronic and photovoltaic devices, in automobiles, and in biotechnology. The success of HWCVD is largely due to its various advantages, including high deposition rate, low substrate temperatures, lack of plasma-induced damage, and large-area uniformity. Film growth in HWCVD is induced by reactive species generated from primary decomposition on the metal wire or from secondary reactions in the gas phase. In order to achieve a rational and efficient optimization of the process, it is essential to identify the reactive species and to understand the chemical kinetics that govern the production of these precursor species for film growth. In this Account, we report recent progress in unraveling the complex gas-phase reaction chemistry in the HWCVD growth of silicon carbide thin films using organosilicon compounds as single-source precursors. We have demonstrated that laser ionization mass spectrometry is a powerful diagnostic tool for studying the gas-phase reaction chemistry when combined with the methods of isotope labeling and chemical trapping. The four methyl-substituted silane molecules, belonging to open-chain alkylsilanes, dissociatively adsorb on W and Ta filaments to produce methyl radical and H2 molecule. Under the typical deposition pressures, with increasing number of methyl substitution, the dominant chemistry occurring in the gas phase switches from silylene/silene reactions to free-radical short chain reactions. This change in dominant reaction intermediates from silylene/silene to methyl radicals explains the observation from thin film deposition that silicon carbide films become more C-rich with a decreasing number of Si-H bonds in the four precursor molecules. In the case of cyclic monosilacyclobutanes, we have

  1. Structural properties of phase-change InSbTe thin films grown at a low temperature by metalorganic chemical vapor deposition.

    PubMed

    Ahn, Jun-Ku; Park, Kyoung-Woo; Hur, Sung-Gi; Kim, Chung-Soo; Lee, Jeong-Yong; Yoon, Soon-Gil

    2011-01-01

    The feasibility of new InSbTe (IST) chalcogenide materials at the deposition temperatures of 225 and 250 degrees C using metalorganic chemical vapor deposition (MOCVD) for phase-change random access memory (PRAM) applications was investigated. Samples grown at 225 degrees C consisted of the main InTe phase, including a small amount of Sb. On the other hand, samples grown at 250 degrees C included the crystalline phases of InSb and InSbTe. MOCVD-IST materials are powerful candidates for highly-integrated PRAM applications.

  2. Thermodynamic Properties of Nitrogen Including Liquid and Vapor Phases from 63K to 2000K with Pressures to 10,000 Bar

    NASA Technical Reports Server (NTRS)

    Jacobsen, Richard T.; Stewart, Richard B.

    1973-01-01

    Tables of thermodynamic properties of nitrogen are presented for the liquid and vapor phases for temperatures from the freezing line to 2000K and pressures to 10,000 bar. The tables include values of density, internal energy, enthalpy, entropy, isochoric heat capacity, isobaric heat capacity velocity of sound, the isotherm derivative, and the isochor derivative. The thermodynamic property tables are based on an equation of state, P=P (p,T), which accurately represents liquid and gaseous nitrogen for the range of pressures and temperatures covered by the tables. Comparisons of property values calculated from the equation of state with measured values for P-p-T, heat capacity, enthalpy, latent heat, and velocity of sound are included to illustrate the agreement between the experimental data and the tables of properties presented here. The coefficients of the equation of state were determined by a weighted least squares fit to selected P-p-T data and, simultaneously, to isochoric heat capacity data determined by corresponding states analysis from oxygen data, and to data which define the phase equilibrium criteria for the saturated liquid and the saturated vapor. The vapor pressure equation, melting curve equation, and an equation to represent the ideal gas heat capacity are also presented. Estimates of the accuracy of the equation of state, the vapor pressure equation, and the ideal gas heat capacity equation are given. The equation of state, derivatives of the equation, and the integral functions for calculating derived thermodynamic properties are included.

  3. Cadmium exposure from smoking cigarettes: variations with time and country where purchased.

    PubMed

    Elinder, C G; Kjellström, T; Lind, B; Linnman, L; Piscator, M; Sundstedt, K

    1983-10-01

    Cadmium has been determined in 26 brands of cigarettes purchased in eight different countries throughout the world and in 16 different samples of cigarettes produced in Sweden between 1918 and 1968. In addition the amount of cadmium released from smoking one cigarette to the particulate phase collected from a smoking simulation machine, corresponding to the amount actually inhaled by a smoker, has been determined. The cadmium concentration in different brands of cigarettes ranged from 0.19 to 3.0 micrograms Cd/g dry wt, with a general tendency toward lower values in cigarettes from developing countries. No systematic change in the cadmium concentration of cigarettes with time could be revealed. The amount of cadmium inhaled from smoking one cigarette containing about 1.7 microgram Cd was estimated to be 0.14 to 0.19 microgram, corresponding to about 10% of the total cadmium content in the cigarette.

  4. Transition between the 1 x 1 and ({radical}3 x 2{radical}3)R30{degree} surface structures of GaN in the vapor-phase environment

    SciTech Connect

    Munkholm, A.; Thompson, C.; Stephenson, G. B.; Eastman, J. A.; Auciello, O.; Fini, P.; Speck, J. S.; DenBaars, S. P.

    2000-01-12

    Out-of-plane structures of the GaN(0001) surface in the metal-organic chemical vapor deposition (MOCVD) environment have been determined using in situ grazing-incidence X-ray scattering. The authors measured 11{bar 2}{ell} crystal truncation rod intensities at a variety of temperatures and ammonia partial pressures on both sides of the 1 x 1 to ({radical}3 x 2{radical}3)R30{degree} surface phase transition. The out-of-plane structure of the ({radical}3 x 2{radical}3)R30{degree} phase appears to be nearly independent of temperature below the transition, while the structure of the 1 x 1 phase changes increase rapidly as the phase transition is approached from above. A model for the structure of the 1 x 1 phase with a partially-occupied top Ga layer agrees well with the data. The observed temperature dependence is consistent with a simple model of the equilibrium between the vapor phase and the surface coverage of Ga and N. In addition, the authors present results on the kinetics of reconstruction domain coarsening following a quench into the ({radical}3 x 2{radical}3)R30{degree} phase field.

  5. GaAs Solar Cells Grown by Hydride Vapor-Phase Epitaxy and the Development of GaInP Cladding Layers

    SciTech Connect

    Simon, John; Schulte, Kevin L.; Young, David L.; Haegel, Nancy M.; Ptak, Aaron J.

    2016-01-01

    The high cost of high-efficiency III-V photovoltaic devices currently limits them to niche markets. Hydride vapor-phase epitaxy (HVPE) growth of III-V materials recently reemerged as a low-cost, high-throughput alternative to conventional metal- organic vapor-phase epitaxy (MOVPE) growth of high-efficiency solar cells. Previously, we demonstrated unpassivated HVPEgrown GaAs p-n junctions with good quantum efficiency and high open-circuit voltage (Voc). In this work, we demonstrate the growth of GaInPby HVPE for use as a high-quality surface passivation layer to GaAs solar cells. Solar cells grown with GaInP window layers show significantly improved quantum efficiency compared with unpassivated cells, increasing the short-circuit current (JSC) of these low-cost devices. These results show the potential of low-cost HVPE for the growth of high-quality III-V devices.

  6. Characterization of vacancy-type defects in heteroepitaxial GaN grown by low-energy plasma-enhanced vapor phase epitaxy

    NASA Astrophysics Data System (ADS)

    Calloni, A.; Ferragut, R.; Dupasquier, A.; von Känel, H.; Guiller, A.; Rutz, A.; Ravelli, L.; Egger, W.

    2012-07-01

    The defect concentration in thin GaN layers was estimated by means of positron annihilation spectroscopy. Positron lifetime and Doppler broadening of the annihilation radiation were used. A comparative study of GaN films grown with different techniques was performed. Specific attention has been given to the new low energy plasma enhanced vapor phase epitaxy (LEPEVPE) growth technique. A very high Ga vacancy density (1019 cm-3) was found in a thin GaN layer directly grown by LEPEVPE on a sapphire substrate. However, when a GaN substrate (commercial sample grown by Metal Organic Vapor Phase Epitaxy) is used as a template for LEPEVPE deposition, the vacancy density of the film is low (about 1016 cm-3). This fact provides evidences that the LEPEVPE technique is able to produce high quality GaN layers.

  7. 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.

  8. Position-controlled III-V compound semiconductor nanowire solar cells by selective-area metal-organic vapor phase epitaxy.

    PubMed

    Fukui, Takashi; Yoshimura, Masatoshi; Nakai, Eiji; Tomioka, Katsuhiro

    2012-01-01

    We demonstrate position-controlled III-V semiconductor nanowires (NWs) by using selective-area metal-organic vapor phase epitaxy and their application to solar cells. Efficiency of 4.23% is achieved for InP core-shell NW solar cells. We form a 'flexible NW array' without a substrate, which has the advantage of saving natural resources over conventional thin film photovoltaic devices. Four junction NW solar cells with over 50% efficiency are proposed and discussed.

  9. Macroscopic modeling of heat and water vapor transfer with phase change in dry snow based on an upscaling method: Influence of air convection

    NASA Astrophysics Data System (ADS)

    Calonne, N.; Geindreau, C.; Flin, F.

    2015-12-01

    At the microscopic scale, i.e., pore scale, dry snow metamorphism is mainly driven by the heat and water vapor transfer and the sublimation-deposition process at the ice-air interface. Up to now, the description of these phenomena at the macroscopic scale, i.e., snow layer scale, in the snowpack models has been proposed in a phenomenological way. Here we used an upscaling method, namely, the homogenization of multiple-scale expansions, to derive theoretically the macroscopic equivalent modeling of heat and vapor transfer through a snow layer from the physics at the pore scale. The physical phenomena under consideration are steady state air flow, heat transfer by conduction and convection, water vapor transfer by diffusion and convection, and phase change (sublimation and deposition). We derived three different macroscopic models depending on the intensity of the air flow considered at the pore scale, i.e., on the order of magnitude of the pore Reynolds number and the Péclet numbers: (A) pure diffusion, (B) diffusion and moderate convection (Darcy's law), and (C) strong convection (nonlinear flow). The formulation of the models includes the exact expression of the macroscopic properties (effective thermal conductivity, effective vapor diffusion coefficient, and intrinsic permeability) and of the macroscopic source terms of heat and vapor arising from the phase change at the pore scale. Such definitions can be used to compute macroscopic snow properties from 3-D descriptions of snow microstructures. Finally, we illustrated the precision and the robustness of the proposed macroscopic models through 2-D numerical simulations.

  10. Vapor-Phase Deposition and Modification of Metal-Organic Frameworks: State-of-the-Art and Future Directions.

    PubMed

    Stassen, Ivo; De Vos, Dirk; Ameloot, Rob

    2016-10-04

    Materials processing, and thin-film deposition in particular, is decisive in the implementation of functional materials in industry and real-world applications. Vapor processing of materials plays a central role in manufacturing, especially in electronics. Metal-organic frameworks (MOFs) are a class of nanoporous crystalline materials on the brink of breakthrough in many application areas. Vapor deposition of MOF thin films will facilitate their implementation in micro- and nanofabrication research and industries. In addition, vapor-solid modification can be used for postsynthetic tailoring of MOF properties. In this context, we review the recent progress in vapor processing of MOFs, summarize the underpinning chemistry and principles, and highlight promising directions for future research.

  11. Development of high-bandgap AlGaInP solar cells grown by organometallic vapor-phase epitaxy

    DOE PAGES

    Perl, Emmett E.; Simon, John; Geisz, John F.; ...

    2016-03-29

    AlGaInP solar cells with bandgaps between 1.9 and 2.2 eV are investigated for use in next-generation multijunction photovoltaic devices. This quaternary alloy is of great importance to the development of III-V solar cells with five or more junctions and for cells optimized for operation at elevated temperatures because of the high bandgaps required in these designs. In this work, we explore the conditions for the organometallic vapor-phase epitaxy growth of AlGaInP and study their effects on cell performance. Initial efforts focused on developing ~2.0-eV AlGaInP solar cells with a nominal aluminum composition of 12%. Under the direct spectrum at 1000more » W/m2 (AM1.5D), the best of these samples had an open-circuit voltage of 1.59 V, a bandgap-voltage offset of 440 mV, a fill factor of 88.0%, and an efficiency of 14.8%. We then varied the aluminum composition of the alloy from 0% to 24% and were able to tune the bandgap of the AlGaInP layers from ~1.9 to ~2.2 eV. Furthermore, while the samples with a higher aluminum composition exhibited a reduced quantum efficiency and increased bandgap-voltage offset, the bandgap-voltage offset remained at 500 mV or less, up to a bandgap of ~2.1 eV.« less

  12. Development of high-bandgap AlGaInP solar cells grown by organometallic vapor-phase epitaxy

    SciTech Connect

    Perl, Emmett E.; Simon, John; Geisz, John F.; Olavarria, Waldo; Young, Michelle; Duda, Anna; Friedman, Daniel J.; Steiner, Myles A.

    2016-03-29

    AlGaInP solar cells with bandgaps between 1.9 and 2.2 eV are investigated for use in next-generation multijunction photovoltaic devices. This quaternary alloy is of great importance to the development of III-V solar cells with five or more junctions and for cells optimized for operation at elevated temperatures because of the high bandgaps required in these designs. In this work, we explore the conditions for the organometallic vapor-phase epitaxy growth of AlGaInP and study their effects on cell performance. Initial efforts focused on developing ~2.0-eV AlGaInP solar cells with a nominal aluminum composition of 12%. Under the direct spectrum at 1000 W/m2 (AM1.5D), the best of these samples had an open-circuit voltage of 1.59 V, a bandgap-voltage offset of 440 mV, a fill factor of 88.0%, and an efficiency of 14.8%. We then varied the aluminum composition of the alloy from 0% to 24% and were able to tune the bandgap of the AlGaInP layers from ~1.9 to ~2.2 eV. Furthermore, while the samples with a higher aluminum composition exhibited a reduced quantum efficiency and increased bandgap-voltage offset, the bandgap-voltage offset remained at 500 mV or less, up to a bandgap of ~2.1 eV.

  13. Room temperature operating InAsSb-based photovoltaic infrared sensors grown by metalorganic vapor phase epitaxy

    NASA Astrophysics Data System (ADS)

    Hasegawa, Ryosuke; Yoshikawa, Akira; Morishita, Tomohiro; Moriyasu, Yoshitaka; Nagase, Kazuhiro; Kuze, Naohiro

    2017-04-01

    We have developed InAsxSb1-x-based photovoltaic infrared sensors (PVS) for room temperature operation by metalorganic vapor phase epitaxy (MOVPE). To obtain high performance, we improved the crystallinity of the InAs0.12Sb0.88 absorber layer and utilized a Ga0.33In0.67Sb electron barrier layer. An investigation of InAs0.12Sb0.88 growth conditions using a high-quality InSb buffer layer showed that we were able to obtain the smallest full-width at half-maximum (FWHM) of the X-ray diffraction omega rocking curve, 560 arcsec, for a growth temperature of 520°C for a 1 μm thick layer. Moreover, we successfully grew a Ga0.33In0.67Sb barrier layer coherently on an InAs0.12Sb0.88 absorber layer, which is the first report of GayIn1-ySb growth on Sb-rich InAsxSb1-x. An InAsxSb1-x PVS with a responsivity at wavelengths of 8-12 μm was obtained, and estimated detectivity peak at room temperature was approximately 7×107 cm Hz1/2 W-1, which is 1.3 times higher than without a Ga0.33In0.67Sb electron barrier. These results demonstrate that our InAsxSb1-x PVS is a promising device for the 8-12 μm wavelength range at room temperature.

  14. Direct Growth of a-Plane GaN on r-Plane Sapphire Substrate by Metalorganic Vapor Phase Epitaxy

    NASA Astrophysics Data System (ADS)

    Araki, Masahiro; Mochimizo, Noriaki; Hoshino, Katsuyuki; Tadatomo, Kazuyuki

    2007-02-01

    We have investigated the direct growth of nonpolar a-plane GaN layers on an r-plane sapphire substrate by metalorganic vapor-phase epitaxy (MOVPE). A high-density nucleation of GaN islands was obtained on the r-plane sapphire substrate at the initial stage of the high-temperature growth without a buffer layer, which resulted in a two-dimensional (2D) growth mode. We studied the effects of V/III ratio growth conditions on the surface morphology and growth features of an a-plane GaN layer. The results showed that a high density of pits with an inverse-pyramidal shape were formed at a high V/III ratio, whereas a relatively low density of pits were formed at a low V/III ratio due to the increase in the rate of lateral growth along the c-axis direction. We successfully grew a-plane GaN layers with a flat and pit-free surface using the “two-step growth method”. The method consisted of growing a first layer at a high V/III ratio and growing a second layer at a low V/III ratio. We found that the first layer plays an important role in GaN layer growth. The formation of a void-free GaN layer with sidewall facets in the first step leads to a flat and pit-free layer grown at a high rate of lateral growth along the c-axis direction in the second step.

  15. The growth and properties of In-doped metalorganic vapor phase epitaxy interdiffused multilayer process (HGCd)Te

    NASA Astrophysics Data System (ADS)

    Gough, J. S.; Houlton, M. R.; Irvine, S. J. C.; Shaw, N.; Young, M. L.; Astles, M. G.

    1991-10-01

    Indium doping of Hg1-xCdxTe layers grown by metalorganic vapor phase epitaxy using the interdiffused multilayer process has been investigated using trimethyl indium as the dopant source. The epitaxial growth was performed onto 2° off <100> CdTeSe substrates at ˜350 °C using dimethyl cadmium (DMCd) and di-isopropyl telluride as the alkyl sources. Doping in the range 1017-2×1018 cm-3 was achieved. By comparing Hall effect measurements of carrier concentration with secondary ion mass spectrometry analyses of the In concentrations in the layers, it was found that the In was only 30% active in the as-grown layers but ˜100% active after Hg-rich isothermal annealing at 250 °C for 48 h. At In concentrations greater than 2×1018 cm-3, the carrier concentration levels off, probably due to the solubility limit of In being reached. The annealed doped layers show slightly higher carrier mobilities than as-grown layers for the same carrier concentration. An apparent shift of the absorption edge to shorter wavelength with increasing donor concentration is thought to be due to the Moss-Burstein effect rather than a change in alloy composition x. A singificant ``memory'' effect has been found with trimethyl In which persists for several runs and is probably due to strong adsorption onto the stainless steel surfaces in the growth system. This can be overcome by vacuum baking of the pipework. The growth of a heterostructure using In doping has shown that there is no serious diffusion problem with In under the growth conditions used.

  16. Quasi-heteroepitaxial growth of β-Ga2O3 on off-angled sapphire (0 0 0 1) substrates by halide vapor phase epitaxy

    NASA Astrophysics Data System (ADS)

    Oshima, Yuichi; Vίllora, Encarnaciόn G.; Shimamura, Kiyoshi

    2015-01-01

    We demonstrate the high-speed growth of β-Ga2O3 quasi-heteroepilayers on off-angled sapphire (0 0 0 1) substrates by halide vapor phase epitaxy (HVPE). (2 bar 0 1) oriented β-Ga2O3 layers were successfully grown using GaCl and O2 as source gases. The growth rate monotonically increased with increasing the partial pressures of the source gases, reaching over 250 μm/h. This rate is over two orders of magnitude larger than those of conventional vapor phase epitaxial growth techniques such as molecular beam epitaxy or metalorganic vapor phase epitaxy. X-ray pole figure measurements indicated the presence of six in-plane rotational domains, in accordance with the substrate symmetry, plus some minor (3 1 0) domains. By the use of off-angled substrates and thick layer overgrowth, one of the in-plane orientations was strongly favored and the (3 1 0) residuals effectively suppressed, so that quasi-heteroepitaxial growth was achieved. Therefore, these results indicate the high-potential of the HVPE technique for the growth of thick and thin β-Ga2O3 layers for the cost-effective production of β-Ga2O3 based devices.

  17. Molecular Simulations of the Vapor-Liquid Phase Interfaces of Pure Water Modeled with the SPC/E and the TIP4P/2005 Molecular Models

    NASA Astrophysics Data System (ADS)

    Vinš, Václav; Celný, David; Planková, Barbora; Němec, Tomáš; Duška, Michal; Hrubý, Jan

    2016-03-01

    In our previous study [Planková et al., EPJWeb. Conf. 92, 02071 (2015)], several molecular simulations of vapor-liquid phase interfaces for pure water were performed using the DL_POLY Classic software. The TIP4P/2005 molecular model was successfully used for the modeling of the density profile and the thickness of phase interfaces together with the temperature dependence of the surface tension. In the current study, the extended simple point charge (SPC/E) model for water was employed for the investigation of vapor-liquid phase interfaces over a wide temperature range from 250 K to 600 K. The TIP4P/2005 model was also used with the temperature step of 25 K to obtain more consistent data compared to our previous study. Results of the new simulations are in a good agreement with most of the literature data. TIP4P/2005 provides better results for the saturated liquid density with its maximum close to 275 K, while SPC/E predicts slightly better saturated vapor density. Both models give qualitatively correct representation for the surface tension of water. The maximum absolute deviation from the IAPWS standard for the surface tension of ordinary water is 10.4 mN · m-1 and 4.1 mN · m-1 over the temperature range from 275 K to 600 K in case of SPC/E and TIP4P/2005, respectively.

  18. Modification and calibration of a passive air sampler for monitoring vapor and particulate phase brominated flame retardants in indoor air: application to car interiors.

    PubMed

    Abdallah, Mohamed Abou-Elwafa; Harrad, Stuart

    2010-04-15

    A passive air sampler was modified to monitor both vapor and particulate phase brominated flame retardants (BFRs) in indoor air using polyurethane foam disks and glass fiber filters (GFF). Significant correlation (p < 0.01) was observed between passive (ng day(-1)) and active sampler (ng m(-3)) derived BFR concentrations in an office microenvironment (r = 0.94 and 0.89 for vapor and particulate phase BFRs, respectively). A calibration experiment was performed where concentrations of target BFRs were obtained for an office using a low volume active sampler operated over a 50 day period alongside passive samplers. The passive uptake rates of each studied BFR ranged between (0.558-1.509 ng day(-1)) and (0.448-0.579 ng day(-1)) for vapor and particulate phases, respectively. The passive entrapment of particles by the GFF was investigated using environmental scanning electron microscopy which revealed gravitational deposition of particles as the main mechanism involved. The developed sampler was applied to monitor BFR concentrations in 21 cars. Average concentrations of SigmaHBCDs, TBBP-A, and Sigmatetra-deca BDEs were 400, 3, and 2200 pg m(-3) in cabins and 400, 1, and 1600 pg m(-3) in trunks. No significant differences (p < 0.05) were observed between levels of SigmaHBCDs and Sigmatrito hexa- BDEs in cabins and trunks. However, TBBP-A, BDE-209, and SigmaPBDEs concentrations were significantly higher in vehicle cabins.

  19. New phase equilibrium analyzer for determination of the vapor-liquid equilibrium of carbon dioxide and permanent gas mixtures for carbon capture and storage.

    PubMed

    Ke, Jie; Parrott, Andrew J; Sanchez-Vicente, Yolanda; Fields, Peter; Wilson, Richard; Drage, Trevor C; Poliakoff, Martyn; George, Michael W

    2014-08-01

    A high-pressure, phase equilibrium analyzer incorporating a fiber-optic reflectometer is described. The analyzer has been designed for measuring the vapor-liquid equilibrium data of multi-component mixtures of carbon dioxide and permanent gases, providing a novel tool to acquire of a large number of phase equilibrium data for the development of the new carbon capture and storage technologies. We demonstrate that the analyzer is suitable for determining both the bubble- and dew-point lines at temperature from 253 K and pressure up to 25 MPa using pure CO2 and two binary mixtures of CO2 + N2 and CO2 + H2.

  20. New phase equilibrium analyzer for determination of the vapor-liquid equilibrium of carbon dioxide and permanent gas mixtures for carbon capture and storage

    NASA Astrophysics Data System (ADS)

    Ke, Jie; Parrott, Andrew J.; Sanchez-Vicente, Yolanda; Fields, Peter; Wilson, Richard; Drage, Trevor C.; Poliakoff, Martyn; George, Michael W.

    2014-08-01

    A high-pressure, phase equilibrium analyzer incorporating a fiber-optic reflectometer is described. The analyzer has been designed for measuring the vapor-liquid equilibrium data of multi-component mixtures of carbon dioxide and permanent gases, providing a novel tool to acquire of a large number of phase equilibrium data for the development of the new carbon capture and storage technologies. We demonstrate that the analyzer is suitable for determining both the bubble- and dew-point lines at temperature from 253 K and pressure up to 25 MPa using pure CO2 and two binary mixtures of CO2 + N2 and CO2 + H2.