Process Windows and Properties of Tungstenand Vanadium-Oxides Deposited by MSIP-PVD-Process

1998 ◽  
Vol 555 ◽  
Author(s):  
O. Knotek ◽  
E. Lugscheider ◽  
S. Bäarwulf ◽  
C. Barimani
Keyword(s):  
Gas Flow ◽  
Elevated Temperatures ◽  
Stable Process ◽  
Oxidation Stability ◽  
Solid Lubricants ◽  
Vanadium Oxides ◽  
Atmospheric Conditions ◽  
Flow Process ◽  
Process Failure ◽  
Oxide Phases

AbstractThe tungsten and vanadium oxides are well known to be usable as solid lubricants at elevated temperatures. Such metal-oxides are interesting for tribological insets at atmospheric conditions because of their “oxidation stability”. This paper reports about investigations made to find stable process windows for the deposition of tungsten and vanadium oxides in a reactive d.c. mode by the MSIP-PVD-process. One focus of the study is on the metal oxide-phases generated in the MSIP-process under various conditions and their mechanical and metallographic properties. Coatings were deposited, developed and analyzed by standard testing methods such as SEM, microhardness (nanoindentation), XRD and scratch testing to characterize the mechanical and structural properties. Stable process windows will be presented for the reactive mode as well as the influence of different process parameters to the microstructure and the material properties. It will be shown that it is possible to deposit vanadium-oxides despite contamination effects in wide ranges by adapting the gas-flow. Process failure was determined at 15 - 18 % oxygen partial pressure for reactively deposited tungsten oxides.

scholarly journals Modeling of the process of the extinguishing gas concentration changes in the protected compartment

2018 ◽  
Vol 247 ◽  
pp. 00041
Author(s):  
Przemysław Kubica ◽  
Sylwia Boroń
Keyword(s):  
Fire Safety ◽  
Retention Time ◽  
Gas Flow ◽  
Analytical Models ◽  
Correct Prediction ◽  
Atmospheric Conditions ◽  
Flow Process ◽  
Gas Concentration ◽  
Proposed Model ◽  
Concentration Changes

The article discusses the aspect of the fire safety of rooms protected by Fixed Gaseous Extinguishing System (FGE-system). On the basis of a literature study, including the analysis of design standards, it was claimed that analytical models of gas outflow from the compartment ignore some parameters that can affect the process of extinguishing gas concentration changes in time. Correct prediction of the gas flow process may affect the retention time value, which is an important determinant of the fire safety of rooms protected by FGE-system. The density of extinguishing gas was indicated as a parameter with a large potential for extending the retention time. It was noted that the density of gas depends on atmospheric conditions like temperature, pressure and humidity, which are omitted in the standard models. In the research part, the concentration distribution of nitrogen and nitrogen-argon mixtures were analyzed using three methods. Obtained experimental data were compared with analytical calculations using a standard model (model N) and a new proposed model extended by an impact of the atmospheric conditions (model PK). Model PK showed greater accuracy of determining the process of extinguishing gas concentration changes. The new proposed model might be a valuable tool for further analysis of gas flow through the room.

scholarly journals Temperature uniformity in the CERN CLOUD chamber

2017 ◽  
Vol 10 (12) ◽  
pp. 5075-5088 ◽  
Author(s):  
António Dias ◽  
Sebastian Ehrhart ◽  
Alexander Vogel ◽  
Christina Williamson ◽  
João Almeida ◽  
...  
Keyword(s):  
Steady State ◽  
Air Temperature ◽  
Elevated Temperatures ◽  
Trace Gases ◽  
Vertical Direction ◽  
Cloud Chamber ◽  
Temperature Uniformity ◽  
Atmospheric Conditions ◽  
Cloud Droplets ◽  
Experimental Conditions

Abstract. The CLOUD (Cosmics Leaving OUtdoor Droplets) experiment at CERN (European Council for Nuclear Research) investigates the nucleation and growth of aerosol particles under atmospheric conditions and their activation into cloud droplets. A key feature of the CLOUD experiment is precise control of the experimental parameters. Temperature uniformity and stability in the chamber are important since many of the processes under study are sensitive to temperature and also to contaminants that can be released from the stainless steel walls by upward temperature fluctuations. The air enclosed within the 26 m3 CLOUD chamber is equipped with several arrays (strings) of high precision, fast-response thermometers to measure its temperature. Here we present a study of the air temperature uniformity inside the CLOUD chamber under various experimental conditions. Measurements were performed under calibration conditions and run conditions, which are distinguished by the flow rate of fresh air and trace gases entering the chamber at 20 and up to 210 L min−1, respectively. During steady-state calibration runs between −70 and +20 °C, the air temperature uniformity is better than ±0.06 °C in the radial direction and ±0.1 °C in the vertical direction. Larger non-uniformities are present during experimental runs, depending on the temperature control of the make-up air and trace gases (since some trace gases require elevated temperatures until injection into the chamber). The temperature stability is ±0.04 °C over periods of several hours during either calibration or steady-state run conditions. During rapid adiabatic expansions to activate cloud droplets and ice particles, the chamber walls are up to 10 °C warmer than the enclosed air. This results in temperature differences of ±1.5 °C in the vertical direction and ±1 °C in the horizontal direction, while the air returns to its equilibrium temperature with a time constant of about 200 s.

Tribological Behavior of Ni-Based Self-Lubricating Composites at Elevated Temperatures

2015 ◽  
pp. 72-106
Author(s):  
Jianliang Li ◽  
Dangsheng Xiong ◽  
Yongkun Qin ◽  
Rajnesh Tyagi
Keyword(s):  
High Temperature ◽  
Friction And Wear ◽  
Solid Lubricant ◽  
Elevated Temperatures ◽  
Wear Behavior ◽  
Composite Coatings ◽  
Solid Lubricants ◽  
Friction And Wear Behavior ◽  
Nickel Base ◽  
Self Lubricating Composites

This chapter illustrates the effect of the addition of solid lubricants on the high temperature friction and wear behavior of Ni-based composites. Ni-based composites containing solid lubricant particles both in nano and micrometer range have been fabricated through powder metallurgy route. In order to explore the possible synergetic action of a combination of low and high temperature solid lubricant, nano or micro powders of two or more solid lubricants were added in the composites. This chapter introduces the fabrication of the Ni-based self-lubricating composites containing graphite and/or MoS2, Ag and/or rare earth, Ag and/or hBN as solid lubricants and their friction and wear behavior at room and elevated temperatures. The chapter also includes information on some lubricating composite coatings such as electro-deposited nickel-base coating containing graphite, MoS2, or BN and graphene and their tribological characteristics.

scholarly journals Impact of Heterogeneity on the Transient Gas Flow Process in Tight Rock

Energies ◽  
2019 ◽  
Vol 12 (18) ◽  
pp. 3559 ◽  
Author(s):  
Jia ◽  
Tsau ◽  
Barati ◽  
Zhang
Keyword(s):  
History Matching ◽  
Gas Flow ◽  
Preferential Flow ◽  
Early Stage ◽  
Ideal Gas ◽  
Flow Path ◽  
Flow Process ◽  
The Core ◽  
Porosity And Permeability ◽  
Preferential Flow Path

There exits a great challenge to evaluate the flow properties of tight porous media even at the core scale. A pulse-decay experiment is routinely used to measure the petrophysical properties of tight cores including permeability and porosity. In this study, 5 sets of pulse-decay experiments are performed on a tight heterogeneous core by flowing nitrogen in the forward and backward directions under different pressures under pore pressures approximately from 100 psi to 300 psi. Permeability values from history matching are from about 300 nD to 600 nD which shows a good linear relationship with the inverse of pore pressure. A preferential flow path is found even when the microcrack is absent. The preferential path causes different porosity values using differential initial upstream and downstream pressure. In addition, the porosity values calculated based on the forward and backward flow directions are also different, and the values are about 1.0% and 2.3%, respectively, which is the primary novelty of this study. The core heterogeneity effect significantly affects the very early stage of pressure responses in both the upstream and downstream but the permeability values are very close in the late-stage experiment. We proposed that that there are two reasons for the preferential flow path: the Joule–Thomson effect for non-ideal gas and the core heterogeneity effect. Based on the finding of this study, we suggest that very early pressure response in a pulse-decay experiment should be closely examined to identify the preferential flow path, and failure to identify the preferential flow path leads to significant porosity and permeability underestimation.

Phenomenological Modeling of Combustion in Pre-Chamber and the Pilot Flame for Natural Gas Engines

2019 ◽  
Author(s):  
Long Liu ◽  
Xia Wen ◽  
Qian Xiong ◽  
Xiuzhen Ma
Keyword(s):  
Natural Gas ◽  
Combustion Chamber ◽  
Alternative Fuels ◽  
Gas Flow ◽  
Combustion Process ◽  
Clean Energy ◽  
Combustion Model ◽  
Flame Surface ◽  
Flow Process ◽  
Natural Gas Engines

Abstract With energy shortages and increasing environmental problems, natural gas, as a clean energy, has the advantages of cheap price and large reserves and has become one of the main alternative fuels for marine diesel engines. For large bore natural gas engines, pre-chamber spark plug ignition can be used to increase engine efficiency. The engine mainly relies on the flame ejected from the pre-chamber to ignite the mixture of natural gas and air in the main combustion chamber. The ignition flame in the main combustion chamber is the main factor affecting the combustion process. Although the pre-chamber natural gas engines have been extensively studied, the characteristics of combustion in the pre-chamber and the development of ignition flame in the main combustion chamber have not been fully understood. In this study, a two-zone phenomenological combustion model of pre-chamber spark-ignition natural gas engines is established based on the exchange of mass and energy of the gas flow process in the pre-chamber and the main combustion chamber. The basic characteristics of the developed model are: a spherical flame surface is used to describe the combustion state in the pre-chamber, and according to the turbulent jet theory, the influence of turbulence on the state of the pilot flame is considered based on the Reynolds number. According to the phenomenological model, the time when the flame starts to be injected from the pre-chamber to the main combustion chamber, and the parameters such as the length of the pilot flame are analyzed. The model was verified by experimental data, and the results showed that the calculated values were in good agreement with the experimental values. It provides an effective tool for mastering the law of flame development and supporting the optimization of combustion efficiency.

scholarly journals Tribological characteristics of high strength low alloy steel under various environmental conditions

2020 ◽  
Vol 34 (07n09) ◽  
pp. 2040044
Author(s):  
Mun Ki Bae ◽  
Ho Gi Lim ◽  
Yeong Min Park ◽  
Seock Sam Kim ◽  
Tae Gyu Kim
Keyword(s):  
Alloy Steel ◽  
Environmental Conditions ◽  
Gas Flow ◽  
Wear Test ◽  
High Strength ◽  
Atmospheric Conditions ◽  
Low Alloy Steel ◽  
Gun Barrel ◽  
The Coefficient Of Friction ◽  
Ar Gas

High strength low alloy steel has excellent heat resistance and high strength. As it is commonly used as gun barrel material, a long service life and superior wear resistance are necessary for steel components. Here we investigated the wear characteristics of high strength low alloy steel surfaces under various environmental conditions, using a pin-on-disk wear test. Oxidation and wear debris effects on the coefficient of friction (COF) of the alloy steel were examined under air and argon (Ar) gas flow at atmospheric conditions.

Iron Cross-Contamination Dynamics at Elevated Temperatures in Oxygen Gas Flow

2019 ◽  
Vol 1 (30) ◽  
pp. 25-32
Author(s):  
Igor Rapoport ◽  
Patrick Taylor ◽  
Benno Orschel ◽  
Fritz Kirscht ◽  
Joel Kearns
Keyword(s):  
Gas Flow ◽  
Elevated Temperatures ◽  
Cross Contamination ◽  
Oxygen Gas
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