8 results
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2. Assessment of sediment deposition rates in a karst depression of a small catchment in Huanjiang, Guangxi, southwest China, using the cesium-137 technique.
- Author
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Li, H., Zhang, X., Wang, K., and Wen, A.
- Subjects
- *
SEDIMENTATION & deposition research , *KARST , *WATERSHEDS , *CESIUM & the environment , *SOIL erosion , *DESERTIFICATION - Abstract
Use of the fallout radionuclide cesium-137 (137Cs) as a tracer has been widely employed for assessment of soil losses and dating of deposited sediment; however, few studies have been conducted in karst environments using this technique. In this study, the 137Cs technique was employed to assess sediment deposition rates in a depression in a small catchment of southwest China. Information derived from the 137Cs measurement of sediment samples collected from a depression in a small catchment in southwest China was used to estimate the sediment deposition rate since 1963, and the rate of soil erosion in the study catchment was also discussed. The results presented in this paper indicated that the depression acted as a sink of soils being eroded from the upland slopes. The mean sediment deposition rate and specific sediment yield of the study depression since 1963 were estimated to be 0.37 cm y-1 (0.15 in yr-1) and 50.2 t km-2 y-1 (0.184 tn ac-1 yr-1), respectively. Analysis of the topographic characteristics of the catchment revealed that the rate of soil redistribution of the catchment was very close to the sediment deposition rate of the depression because no significant sediment accumulation occurred upstream of the depression and in the meantime, very few sediments drained out through the sinkhole with the runoff. Therefore, it was inferred that the rate of soil redistribution in the study area was 55.8 t km-2 y-1 (0.205 tn ac-1 yr-1). Overall, the results revealed that there was a low background rate of soil loss in the karst mountain area suffering from severe land desertification in Southwest China. Furthermore, the results illuminated the potential for use of the 137Cs technique to evaluate the sediment deposition and soil erosion rates in karst areas of southwest China, where limited information regarding soil erosion and sedimentation exists. [ABSTRACT FROM AUTHOR]
- Published
- 2010
- Full Text
- View/download PDF
3. Multiwalled carbon nanotube deposition profiles within a CVD reactor: An experimental study
- Author
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Kunadian, Illayathambi, Andrews, Rodney, Pinar Mengüç, M., and Qian, Dali
- Subjects
- *
CARBON nanotubes , *CHEMICAL vapor deposition , *CHEMICAL reactors , *TEMPERATURE effect , *GAS flow , *CRYSTAL growth - Abstract
Abstract: A number of proposed applications of carbon nanotube (CNT) arrays require that uniform deposition of well-aligned CNTs is achieved. The CNT deposition profiles inside a chemical vapor deposition (CVD) reactor are strongly dependant on the reaction temperatures, feed gas flow rates, carrier gas flow rates and reactor geometry. In addition, objects placed in the path of the flow of feed material could affect the deposition patterns. In this paper, an experimental study aimed at achieving better control of the deposition patterns of CNTs is presented. Multiwalled CNTs were grown on a long substrate by the catalytic CVD of a xylene/ferrocene solution. The deposition patterns on the substrate were examined for different furnace temperatures, xylene/ferrocene feed rates and carrier gas flow rates. Small objects representative of electronic devices were placed at different locations on the substrate and their effect on the deposition patterns was explored. The effect of changing the height and the gap distance between these objects was also studied. [Copyright &y& Elsevier]
- Published
- 2009
- Full Text
- View/download PDF
4. Simultaneous particle and vapor deposition in a laminar boundary layer
- Author
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Filippov, A.V.
- Subjects
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VAPOR-plating , *HEAT exchangers , *POWER plants - Abstract
A number of industrial and technical applications involve simultaneous particle and vapor deposition from a hot gas onto cold surfaces. For example, deposition of particles and corrosive vapors reduces the lifetime of heat exchangers in power plants and in blades of gas turbines. On another hand, in the OVD (outside vapor deposition) process used in manufacturing optical fibers, a controlled deposition of silica particles and dopant vapors is necessary for obtaining products with prescribed characteristics. In the present paper, a detailed mathematical and numerical model of this process is developed for the flow region near a stagnation point of a two-dimensional body, such as a cylinder. Using an inverse scavenging factor as a small parameter, an analytical asymptotic solution is found for vapor distribution in a condensation layer adjacent to the surface. The results of numerical calculations are presented in the form of surface temperature dependencies of dimensionless deposition rates and profiles of physical parameters of the system at a wide range of surface/gas temperature ratios. [Copyright &y& Elsevier]
- Published
- 2003
- Full Text
- View/download PDF
5. Synthesis of Nanocomposite TiSiCN Coatings by Titanium Evaporation and Organosilicon Compound Activation in Hollow Cathode Arc Discharge
- Author
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Andrey Menshakov, Yulia Bruhanova, Andrey Kukharenko, and Ivan Zhidkov
- Subjects
DEPOSITION RATES ,PECVD ,GASES MIXTURE ,HEXAMETHYLDISILAZANE ,Filtration and Separation ,TITANIUM CARBIDE ,SILICON COMPOUNDS ,TITANIUM NITRIDE ,NANO-COMPOSITE COATING ,TiSiCN ,nanocomposite coatings ,PVD ,hollow cathode arc ,anodic evaporation ,Chemical Engineering (miscellaneous) ,CATHODES ,X RAY PHOTOELECTRON SPECTROSCOPY ,HOLLOW CATHODES ,ORGANOSILICON COMPOUNDS ,COATINGS ,VAPOR FLOWS ,ANODIC EVAPORATION ,Process Chemistry and Technology ,TISICN ,GAS MIXTURES ,PHYSICAL VAPOR DEPOSITION ,NANOCOMPOSITES ,ARC DISCHARGE ,HOLLOW CATHODE ARC ,EVAPORATION ,TITANIA ,NANOCOMPOSITE COATINGS - Abstract
TiSiCN coatings have been obtained by anode evaporation of titanium and the decomposi-tion of hexamethyldisilazane in an arc discharge, using a self-heated hollow cathode, at the pressure rate of 1 mTorr of the Ar+N2 gas mixture. The proposed method makes it possible to independently and widely change the amount of metal and precursor vapor flows, the pressure and composition of the vapor-gas mixture and the degree of ionic interaction on the surface of the growing coating within a single discharge system. The paper presents the method and the results of the effect of a current discharge (10–50 A), and the flux of precursor vapours (0–1 g/h), on deposition rates, compositions, and properties of TiSiCN coatings deposited by an advanced combined PVD+PECVD method. Dense homogeneous TiSiCN coatings up to 6 µm thick and up to 27.5 GPa in hardness were obtained at 7.5 µm/h. The composition of the obtained coatings has been studied by X-ray diffraction and X-ray photoelectron spectroscopy, and it has been shown that the presented methods can form nanocomposite coatings with nanocrystallites TiC, TiN, and TiCxN1−x 3–10 nm in the amorphous matrix based on SiCN. © 2022 by the authors. Licensee MDPI, Basel, Switzerland. Russian Science Foundation, RSF: 20-79-10059 Funding: This research was funded by Russian Science Fund, grant number 20-79-10059.
- Published
- 2022
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6. Mercury distribution in sediment profiles from lakes of the high pantanal, Mato Grosso State, Brazil
- Author
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De Lacerda, L. D., Salomons, W., Pfeiffer, W. C., and Bastos, W. R.
- Published
- 1991
- Full Text
- View/download PDF
7. Elaboration of nitride thin films by reactive sputtering
- Author
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Arnaud Tricoteaux, Nicolas Horny, Pierre Yves Jouan, Laboratoire des Matériaux Céramiques et Procédés Associés - EA 2443 (LMCPA), and Université de Valenciennes et du Hainaut-Cambrésis (UVHC)-INSA Institut National des Sciences Appliquées Hauts-de-France (INSA Hauts-De-France)
- Subjects
Materials science ,DC reactive magnetron sputtering ,taxas de deposição ,02 engineering and technology ,Substrate (electronics) ,Nitride ,01 natural sciences ,chemistry.chemical_compound ,Geochemistry and Petrology ,Sputtering ,nitreto de alumínio ,0103 physical sciences ,aluminium nitride ,General Materials Science ,vaporização em ambiente magnetron reativo DC ,Texture (crystalline) ,Thin film ,Composite material ,Waste Management and Disposal ,010302 applied physics ,Aluminium nitride ,Geology ,Biasing ,deposition rates ,021001 nanoscience & nanotechnology ,Amorphous solid ,chemistry ,[PHYS.COND.CM-MS]Physics [physics]/Condensed Matter [cond-mat]/Materials Science [cond-mat.mtrl-sci] ,Economic Geology ,0210 nano-technology - Abstract
International audience; The aim of this paper is first a better understanding of DC reactive magnetron sputtering and its implications, such as the hysteresis effect and the process instability. In a second part, this article is devoted to an example of specific application: Aluminium Nitride. AlN thin films have been deposited by reactive triode sputtering. We have studied the effect of the nitrogen contents in the discharge and the RF bias voltage on the growth of AlN films on Si(100) deposited by triode sputtering. Stoichiometry and crystal orientation of AlN films have been characterized by means of Fourier-transform infrared spectroscopy, X-ray diffraction and secondary electron microscopy. Dense and transparent AlN layers were obtained at high deposition rates. These films have a (002) orientation whatever the nitrogen content in the discharge, but the best crystallised ones are obtained at low value (10%). A linear relationship was observed between the AlN lattice parameter "c" (perpendicular to the substrate surface) and the in-plane compressive stress. Applying an RF bias to the substrate leads to a (100) texture, and films become amorphous. Moreover, the film's compressive stress increases up to a value of 8GPa before decreasing slowly as the bias voltage increases.; O objetivo desse artigo, em um primeiro momento, é uma melhor compreensão da vaporização em um ambiente magnetron reativo DC e as suas conseqüências, tais como o efeito da histeresis e o processo de instabilidade. A segunda parte desse trabalho está dedicada a um estudo de caso: o nitreto de alumínio. Filmes finos de nitreto de alumínio foram depositados por vaporização triodo reativa. Estudamos o efeito dos teores de nitrogênio, na descarga, e da voltagem RF(bias), no crescimento dos filmes de AlN em Si(100) depositados por vaporização triodo. A estequiometria e a orientação cristalina dos filmes de AlN foram caracterizadas por espectroscopia infravermelha em transformada de Fourier, difração de raios X e microscopia de elétrons secundários. Camadas densas e transparentes de AlN foram obtidas em altas taxas de deposição. Independentemente do conteúdo em nitrogênio na descarga, os filmes têm uma orientação (002), mas, para um teor de 10%, obteve-se a melhor cristalização.Uma relação linear foi observada entre o parâmetro de rede c (perpendicular à superfície do substrato) do AlN e as tensões compressivas planas.A aplicação de um "bias" RF ao substrato leva a uma textura (100) e os filmes tornam-se amorfos. Além disso, a tensão compressiva aumenta atingindo valores de até 8Gpa antes de diminuírem lentamente na medida em que o "bias" aumenta.
- Published
- 2006
8. Effects of land use and climate changes on small reservoir siltation in the agricultural belt of European Russia
- Author
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Belyaev V., Golosov V., Markelov M., Ivanova N., Shamshurina E., and Evrard O.
- Subjects
European Russia ,Climate changes ,Siltation ,Agricultural land ,Deposition rates ,Small reservoirs ,Soil erosion ,Microstratigraphy ,Sediment delivery - Abstract
Small reservoirs of agriculture-dominated areas experience severely increased sediment input caused by soil erosion on cultivated slopes, also accompanied at some locations by gully erosion. This causes rapid decrease of the reservoir water storage and shortened periods of functioning. In this paper we discuss several examples of the 137Cs-based short-term siltation chronology of small reservoirs located in different landscape zones within the agricultural belt of European Russia. From two to four time marks could have been established in 137Cs depth distribution curves constructed from detailed depth-incremental sampling of reservoir infill sediment, allowing reconstruction of sediment microstratigraphy and deposition rates. In combination with other independent information sources this provides insight on the relative importance of recent land use changes and climatic variability in controlling sediment delivery within small agriculture-dominated fluvial systems. In combination with sediment redistribution studies, it has become possible to construct closed sediment budgets for catchments of several reservoirs and make a quantitative assessment of sediment delivery variability. Such information is important for appropriate design and management of small agricultural reservoirs in Russia. Copyright © 2013 IAHS Press.
- Published
- 2013
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