Role of Finite Vacancy Relaxation Rate at SHS Reactions in Nanosized Multilayers

2011 ◽  
Vol 309-310 ◽  
pp. 215-222
Author(s):  
T.V. Zaporozhets ◽  
Andriy Gusak
Keyword(s):  
Relaxation Rate ◽  
Free Path ◽  
Vacancy Concentration ◽  
Free Path Length ◽  
Mean Free Path ◽  
Temperature Dependent ◽  
Slowing Down ◽  
Vacancy Generation ◽  
Synthesis Reactions

Rate of SHS (self-propagating high-tеmperature synthesis) reactions in solid nano-sized multilayers is controlled by the time and temperature dependent vacancy concentration. The increase of reaction temperature is typically faster than the rate of vacancy generation. Therefore, the finite relaxation rate of vacancies leads to drastic slowing down of SHS. On the other hand, as-prepared vacancy supersaturation due to fast deposition on the cold substrate may lead to a certain acceleration of SHS. Influence of (1) vacancy mean free path and (2) initial vacancy supersaturation on the SHS rate is investigated numerically. In wide region of parameters the front velocity appears to be inversely proportional to the square root of vacancy mean free path length.

The measurement of mean free path λs using a slowing down time lead spectrometer in the 1–10 eV energy region

1968 ◽  
Vol 22 (4) ◽  
pp. 261-262
Author(s):  
M.P. Navalkar ◽  
K. Chandramoleshwar ◽  
D.V.S. Ramkrishna
Keyword(s):  
Free Path ◽  
Energy Region ◽  
Mean Free Path ◽  
Slowing Down ◽  
Time Lead

Role of neutral-particle bombardment in dust–dust interactions in plasmas

2001 ◽  
Vol 65 (4) ◽  
pp. 257-272 ◽  
Author(s):  
Ya. K. KHODATAEV ◽  
G. E. MORFILL ◽  
V. N. TSYTOVICH
Keyword(s):  
Free Path ◽  
Particle Bombardment ◽  
Neutral Particle ◽  
Mean Free Path ◽  
Dust Particles ◽  
Neutral Particles ◽  
Additional Force ◽  
Numerical Coefficient ◽  
The Mean

It is shown that the interaction of dust with neutral plasma particles can lead to attractive forces between dust particles, both in the case where the distance between dust particles is less than the mean free path of neutral particles and in the case where it is greater. The expressions for attractive forces differs in the two limits only by a numerical coefficient. The additional force of dust interaction is found to be due to the neutrals created by recombination of charged plasma particles on the surface of dust particles. The influence of radiative dust cooling on dust–dust interaction is considered.

Lattice Boltzmann Simulation of Rarefied Gas Flow Along Moving Rigid Objects in Micro-Cavities

2015 ◽  
Author(s):  
Weilin Yang ◽  
Hongxia Li ◽  
TieJun Zhang ◽  
Ibrahim M. Elfadel
Keyword(s):  
Free Path ◽  
Lattice Boltzmann ◽  
Path Length ◽  
Gas Flow ◽  
Rarefied Gas ◽  
Free Path Length ◽  
Mean Free Path ◽  
Fluid Simulation ◽  
Transition Flow ◽  
Rarefied Gas Flow

Rarefied gas flow plays an important role in the design and performance analysis of micro-electro-mechanical systems (MEMS) under high-vacuum conditions. The rarefaction can be evaluated by the Knudsen number (Kn), which is the ratio of the molecular mean free path length and the characteristic length. In micro systems, the rarefied gas flow usually stays in the slip- and transition-flow regions (10−3 < Kn < 10), and may even go into the free molecular flow region (Kn > 10). As a result, conventional design tools based on continuum Navier-Stokes equation solvers are not applicable to analyzing rarefaction phenomena in MEMS under vacuum conditions. In this paper, we investigate the rarefied gas flow by using the lattice Boltzmann method (LBM), which is suitable for mesoscopic fluid simulation. The gas pressure determines the mean free path length and Kn, which further influences the relaxation time in the collision procedure of LBM. Here, we focus on the problem of squeezed film damping caused by an oscillating rigid object in a cavity. We propose an improved LBM with an immersed boundary approach, where an adjustable force term is used to quantify the interaction between the moving object and adjacent fluid, and further determines the slip velocity. With the proposed approach, the rarefied gas flow in MEMS with squeezed film damping is characterized. Different factors that affect the damping coefficient, such as pressure of gas and frequency of oscillation, are investigated in our simulation studies.

Temperature-dependent ballistic transport in a channel with length below the scattering-limited mean free path

2012 ◽  
Vol 111 (5) ◽  
pp. 054301 ◽  
Author(s):  
Vijay K. Arora ◽  
Mastura Shafinaz Zainal Abidin ◽  
Michael L. P. Tan ◽  
Munawar A. Riyadi
Keyword(s):  
Free Path ◽  
Ballistic Transport ◽  
Mean Free Path ◽  
Temperature Dependent

Imaging of Metal/Semiconductor Interface by Ballistic-Electron-Emission Microscopy (Beem)

1992 ◽  
Vol 295 ◽  
Author(s):  
E. Y. Lee ◽  
B. R. Turnew ◽  
J. R. Jimenez ◽  
L. J. Schowalter
Keyword(s):  
Free Path ◽  
Spatial Resolution ◽  
Electron Emission ◽  
Path Length ◽  
Free Path Length ◽  
Mean Free Path ◽  
Ballistic Electron Emission Microscopy ◽  
Semiconductor Interface ◽  
Ballistic Electron ◽  
Emission Microscopy

AbstractStudies in ballistic-electron-emission spectroscopy (BEES) have enabled precise energy measurements of Schottky barrier heights with excellent spatial resolution and, more recently, it was shown that even scattering at the metal/semiconductor interface affects the BEES spectrum [1]. Monte Carlo simulations have been done to predict the spatial resolution of ballistic-electron-emission microscopy (BEEM) [2]. In this paper, we will discuss the experimental spatial resolution of BEEM, and we will also give some of our BEES results for Au/Si and for Au/PtSi/Si. Our experimental BEEM studies indicate that, for Au/Si, hot electron transport is diffusive rather than ballistic, because the inelastic mean free path length (∼100 nm) is much larger than the elastic mean free path length (∼10 nm). This is in agreement with existing theories and with the literature on the internal photoemission method of studying the transport. Even in this diffusive regime, the spatial resolution of BEEM is still expected to be very good, being on the order of 10 nm [2]. Our preliminary work on PtSi shows that it has an attenuation length of 4 nm, which differs significantly from that of Au.

Lifetime of the 961 keV 1 - level in 152 Sm

1960 ◽  
Vol 257 (1288) ◽  
pp. 52-58 ◽  
Keyword(s):  
Free Path ◽  
Electron Capture ◽  
Resonance Scattering ◽  
Mean Free Path ◽  
Resonance Fluorescence ◽  
Slowing Down

With a 152m EuO3 source and a Sm 2 O 3 scatter er, nuclear y-ray resonance scattering and resonance fluorescence self-absorption experiments were performed to determine the lifetime of the 961 keV 1 - level in 152 Sm. The value obtained from scattering , (8±2) x 10 -14 s, is larger than that determined from self absorption , (4.7±0.5) x 10 -14 s; this could be due to in ade­quate know ledge about the slowing down of the source nuclei before the emission of the y-ray. From a comparison of these values, a mean free path of 0.6 x 10 -8 cm for the source nucleus recoiling after electron capture in 152 Eu 2 O 3 has been calculated.

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