scholarly journals Modeling of Catalytic Centers Formation Processes during Annealing of Multilayer Nanosized Metal Films for Carbon Nanotubes Growth

Nanomaterials ◽  
2020 ◽  
Vol 10 (3) ◽  
pp. 554
Author(s):  
Oleg Il’in ◽  
Nikolay Rudyk ◽  
Alexandr Fedotov ◽  
Marina Il’ina ◽  
Dmitriy Cherednichenko ◽  
...  
Keyword(s):  
Carbon Nanotubes ◽  
Mass Transfer ◽  
Chemical Potential ◽  
Stress Gradient ◽  
Metal Films ◽  
Film Structure ◽  
Formation Processes ◽  
Thermal Expansion Coefficients ◽  
Mass Transfer Processes ◽  
The Difference

The paper presents a theoretical model of the catalytic centers formation processes during annealing of multilayer nanosized metal films for carbon nanotubes growth. The approach to the description of the model is based on the mass transfer processes under the influence of mechanical thermoelastic stresses, which arise due to the difference in the thermal expansion coefficients of the substrate materials and nanosized metal layers. The thermal stress gradient resulting from annealing creates a drop in the chemical potential over the thickness of the film structure. This leads to the initiation of diffusion mass transfer between the inner and outer surfaces of the films. As a result, the outer surface begins to corrugate and fragment, creating separate islands, which serve as the basis for the catalytic centers formation. Experimental research on the formation of catalytic centers in the structure of Ni/Cr/Si was carried out. It is demonstrated that the proposed model allows to predict the geometric dimensions of the catalytic centers before growing carbon nanotubes. The results can be used to create micro- and nanoelectronics devices based on carbon nanotube arrays.

scholarly journals A Semi-Theoretical Model for Water Condensation: Dew Used in Conservation of Earthen Heritage Sites

Water ◽  
2020 ◽  
Vol 13 (1) ◽  
pp. 52
Author(s):  
Xiang He ◽  
Sijia Wang ◽  
Bingjian Zhang
Keyword(s):  
Mass Transfer ◽  
Theoretical Model ◽  
Field Experiments ◽  
Environmental Control ◽  
Mass Transfer Process ◽  
Formation Processes ◽  
Heritage Sites ◽  
Dew Formation ◽  
The Difference ◽  
Two Parameter

Dew is a common but important phenomenon. Though water is previously considered to be a threat to earthen heritage sites, artificial dew is showing potential in relic preservation. A model of dew prediction on earthen sites will be essential for developing preventive protection methods, but studies of dew formation processes on relics are limited. In this study, a two parameter model is proposed. It makes approximations according to the features of earthen heritage sites, assuming that a thin and steady air layer exists close to the air–solid interface. This semi-theoretical model was based on calculations of the mass transfer process in the air layer, and was validated by simulations of laboratory experiments (R > 0.9) as well as field experiments. Additionally, a numerical simulation, performed by the commercial software COMSOL, confirmed that the difference between fitting parameter δ and the thickness of assumed mass transfer field was not significant. This model will be helpful in developing automatic environmental control systems for stabilizing water and soluble salts, thus enhancing preventive protection of earthen heritage sites.

scholarly journals The Interrelation between the Optical Coefficients of Ultrathin Metal Films and Their Geometric Parameters of Surface Morphology

2020 ◽  
Vol 15 (2) ◽  
pp. 5-13
Author(s):  
Alim S. Mazinov
Keyword(s):  
High Frequency ◽  
Electromagnetic Waves ◽  
Metal Films ◽  
Film Structure ◽  
Maximum Absorption ◽  
Frequency Range ◽  
Conductive Films ◽  
The Difference ◽  
Transmission And Absorption ◽  
Super High Frequency

The theoretical and experimental data on the study of the optical coefficients of electromagnetic waves in the super high frequency range 2–4,5 GHz and their relationship with the thickness of the conductive films by the example of aluminum are presented. It is showed that transformation of the relief of a thin-film structure with an increase in the bulk mass of the deposited material causes an increase in surface roughness with a maximum of 7 nanometers. It is worth noting that exactly for these thicknesses of the studied films the maximum absorption of the incident electromagnetic wave is experimentally achieved. Meanwhile, a theoretical calculation of the reflection, transmission and absorption coefficients showed the maximum absorption of the incident wave at a thickness of 5 nm. The difference between the experimental and theoretical values of the absorptivity is explained by the non-ideal geometry of ultrathin conductive surfaces. At the thicknesses from 1 nm to 10 nm the film itself is formed in the form of separate nanoislands.

Nonlinear mass transfer and hydrodynamic stability in solubility phenomena

2002 ◽  
Vol 74 (10) ◽  
pp. 1801-1810
Author(s):  
Chr. Bojadjiev
Keyword(s):  
Mass Transfer ◽  
Hydrodynamic Stability ◽  
Heterogeneous Reaction ◽  
Nonlinear Effects ◽  
Concentration Gradients ◽  
Transfer Processes ◽  
Mass Transfer Processes ◽  
The Face ◽  
Mass Transfer Theory ◽  
The Difference

The dissolution of gases, liquids,or solids in liquids is a heterogeneous reaction, and in many cases, the reaction rate is limited by a diffusive transfer of substance in the boundary layer at the face interphase. In modern industry, intensive interphase mass transfer processes are accomplished by large concentration gradients. This can result in a set of nonlinear effects and the difference between experimental data and predictions of the linear mass transfer theory. One of the main nonlinear effects is a result of the induction of a secondary flow at the interface boundary. This can lead to essential changes of the dissolution rate and the hydrodynamic stability of the system.

I Like Her, Because I Like Myself: Self-Evaluation as a Source of Interpersonal Attitudes

2003 ◽  
Vol 50 (4) ◽  
pp. 239-246 ◽  
Author(s):  
Eva Walther ◽  
Claudia Trasselli
Keyword(s):  
Opposite Effect ◽  
Learning Phase ◽  
The Self ◽  
Attitude Formation ◽  
Formation Processes ◽  
False Feedback ◽  
Self Evaluation ◽  
Evaluation Group ◽  
Group A ◽  
The Difference

Abstract. Two experiments tested the hypothesis that self-evaluation can serve as a source of interpersonal attitudes. In the first study, self-evaluation was manipulated by means of false feedback. A subsequent learning phase demonstrated that the co-occurrence of the self with another individual influenced the evaluation of this previously neutral target. Whereas evaluative self-target similarity increased under conditions of negative self-evaluation, an opposite effect emerged in the positive self-evaluation group. A second study replicated these findings and showed that the difference between positive and negative self-evaluation conditions disappeared when a load manipulation was applied. The implications of self-evaluation for attitude formation processes are discussed.

Analysis and calculation of the process of low-pressure reverse osmosis during recycling of hygienic water

2019 ◽  
pp. 28-36
Author(s):  
Leonid S. Bobe ◽  
Nikolay A. Salnikov
Keyword(s):  
Mass Transfer ◽  
Reverse Osmosis ◽  
Life Support ◽  
Space Station ◽  
Low Pressure ◽  
Operating Pressure ◽  
Life Support System ◽  
Cleaning Agent ◽  
The Difference ◽  
Pressure Channel

Analysis and calculation have been conducted of the process of low-pressure reverse osmosis in the membrane apparatus of the system for recycling hygiene water for the space station. The paper describes the physics of the reverse osmosis treatment and determines the motive force of the process, which is the difference of effective pressures (operating pressure minus osmotic pressure) in the solution near the surface of the membrane and in the purified water. It is demonstrated that the membrane scrubbing action is accompanied by diffusion outflow of the cleaning agent components away from the membrane. The mass transfer coefficient and the difference of concentrations (and, accordingly, the difference of osmotic pressures) in the boundary layer of the pressure channel can be determined using an extended analogy between mass transfer and heat transfer. A procedure has been proposed and proven in an experiment for calculating the throughput of a reverse osmosis apparatus purifying the hygiene water obtained through the use of a cleaning agent used in sanitation and housekeeping procedures on Earth. Key words: life support system, hygiene water, water processing, low-pressure reverse osmosis, space station.

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