scholarly journals A Molecular Dynamics Study on the Constraint Conditions of the Particle Growth Process in Laser Synthesis of Nanopowders

2012 ◽  
Vol 2012 ◽  
pp. 1-5
Author(s):  
Shiwei Zhang ◽  
Jun Liu ◽  
Zhijun Zhang ◽  
Wenhui Zhang
Keyword(s):  
Molecular Dynamics ◽  
Growth Rate ◽  
Growth Process ◽  
Synthesis Method ◽  
Chemical Vapor ◽  
Particle Growth ◽  
Growth Zone ◽  
Final Size ◽  
Nanoparticle Growth ◽  
Surrounding Space

Laser-induced chemical vapor deposition (LICVD) is a nanopowder synthesis method in which the nanoparticles of a synthetic product undergo nucleation, growth, and agglomeration. The growth process is crucial because it directly determines the growth rate and final size of nanoparticles. In this paper, the nanoparticle growth process is analyzed through a molecular dynamics study, and the process is divided into five steps. In addition, this study explains the microscopic heat and mass transfer processes that occur in the surrounding space and on the particulate surface. Three constraint conditions that may restrict the growth process, namely, transfer constraint, surface constraint, and temperature constraint conditions, are proposed and modeled. To calculate the final diameter and the nanoparticle growth rate, formulae for the constraint conditions are developed. The behavior of four gases in the particulate growth zone is discussed in detail.

Development of Vertical 3×2〞LPCVD System for Fast Epitaxial Growth on 4H-SiC

2012 ◽  
Vol 717-720 ◽  
pp. 105-108 ◽  
Author(s):  
Wan Shun Zhao ◽  
Guo Sheng Sun ◽  
Hai Lei Wu ◽  
Guo Guo Yan ◽  
Liu Zheng ◽  
...  
Keyword(s):  
Growth Rate ◽  
Chemical Vapor Deposition ◽  
Epitaxial Growth ◽  
Vapor Deposition ◽  
Growth Process ◽  
Chemical Vapor ◽  
Low Pressure ◽  
High Quality ◽  
Pressure Chemical ◽  
Homoepitaxial Layers

A vertical 3×2〞low pressure chemical vapor deposition (LPCVD) system has been developed to realize fast epitaxial growth of 4H-SiC. The epitaxial growth process was optimized and it was found that the growth rate increases with increasing C/Si ratio and tends to saturate when C/Si ratio exceeded 1. Mirror-like thick 4H-SiC homoepitaxial layers are obtained at 1500 °C and C/Si ratio of 0.5 with a growth rate of 25 μm/h. The minimum RMS roughness is 0.20 nm and the FWHM of rocking curves of epilayers grown for 1 hour and 2 hours are 26.2 arcsec and 32.4 arcsec, respectively. These results indicate that high-quality thick 4H-SiC epilayers can be grown successfully on the off-orientation 4H-SiC substrates.

Reduction of the Surface Density of Single Shockley Faults by TCS Growth Process

2011 ◽  
Vol 679-680 ◽  
pp. 67-70 ◽  
Author(s):  
Andrea Canino ◽  
Massimo Camarda ◽  
Francesco La Via
Keyword(s):  
Growth Rate ◽  
Vapor Deposition ◽  
Surface Density ◽  
Growth Process ◽  
Chemical Vapor ◽  
Deposition Process ◽  
Epitaxial Layers ◽  
Spatially Resolved ◽  
Basal Plane Dislocation

Spatially resolved micro-photoluminescence has been used to study the Single Shockley faults surface density and properties on 4H-SiC epitaxial layers. The improvement of quality of epitaxial layers due to the chemical vapor deposition process has been studied by measuring the reduction of mean density of Single Shockley faults. The change of faults density has been correlated to the different precursor gas used for the growth. In fact trichlorosilane has been used instead of silane. The change of precursor led to two different advantages: the reduction of basal plane dislocation surface density and the capability to increase the growth rate of the process. Both these features allow reducing the density of Single Shockley faults.

Silica particle growth in metastable supersaturation solution

2001 ◽  
Vol 16 (2) ◽  
pp. 545-552 ◽  
Author(s):  
Kyung-Soo Kim ◽  
Jun-Kyung Kim ◽  
Woo-Sik Kim
Keyword(s):  
Experimental Data ◽  
Growth Rate ◽  
Sodium Chloride ◽  
Silicon Dioxide ◽  
Growth Process ◽  
Rate Coefficient ◽  
Chloride Concentration ◽  
Molecular Transport ◽  
Particle Growth ◽  
Agitation Speed

In a metastable solution the particle growth rate of silicon dioxide increased with an increase in the initial supersaturation of the metastable solution and agitation speed in the ranges of 2.5 × 10−4 to 2.0 × 10−3 M and 300–1500 rpm, respectively. Based on a power law expression, the particle growth rate order was estimated as 2.0 independent of the initial supersaturation and agitation speed. Meanwhile, the particle growth rate coefficient was enhanced from 2.0 × 10−3 to 1.4 × 10−2 with increase in the agitation speed from 300 to 1500 rpm. From the experimental data, it would appear that the enhanced particle growth rate resulted from the promotion of molecular transport due to the agitation and driving force of the supersaturation in the particle growth process. A slight addition of sodium chloride into the metastable solution caused a marked reduction of the particle growth rate due to the inhibition of growth process by sodium chloride adsorbed on the particle. This effect of sodium chloride on the particle growth appeared in a significant drop of the particle growth rate coefficient from 4.5 × 10−3 to 8.0×10−4 with increase in the sodium chloride concentration from zero to 5.0×10−3 M, but not in the particle growth rate order. The influence of sodium chloride on the particle growth process of silicon dioxide predicted with a Langmuir isotherm matched with the experimental data.

scholarly journals Thermal Aggregation of Recombinant Protective Antigen: Aggregate Morphology and Growth Rate

2013 ◽  
Vol 2013 ◽  
pp. 1-12 ◽  
Author(s):  
Daniel J. Belton ◽  
Aline F. Miller
Keyword(s):  
Growth Rate ◽  
Protective Antigen ◽  
Monomer Concentration ◽  
Particle Growth ◽  
Aggregation Process ◽  
Thermal Aggregation ◽  
Final Size ◽  
Time Resolved ◽  
Electron Microscopies ◽  
Recombinant Protective Antigen

The thermal aggregation of the biopharmaceutical protein recombinant protective antigen (rPA) has been explored, and the associated kinetics and thermodynamic parameters have been extracted using optical and environmental scanning electron microscopies (ESEMs) and ultraviolet light scattering spectroscopy (UV-LSS). Visual observations and turbidity measurements provided an overall picture of the aggregation process, suggesting a two-step mechanism. Microscopy was used to examine the structure of aggregates, revealing an open morphology formed by the clustering of the microscopic aggregate particles. UV-LSS was used and developed to elucidate the growth rate of these particles, which formed in the first stage of the aggregation process. Their growth rate is observed to be high initially, before falling to converge on a final size that correlates with the ESEM data. The results suggest that the particle growth rate is limited by rPA monomer concentration, and by obtaining data over a range of incubation temperatures, an approach was developed to model the aggregation kinetics and extract the rate constants and the temperature dependence of aggregation. In doing so, we quantified the susceptibility of rPA aggregation under different temperature and environmental conditions and moreover demonstrated a novel use of UV spectrometry to monitor the particle aggregation quantitatively, in situ, in a nondestructive and time-resolved manner.

scholarly journals Unusual Dependence of the Diamond Growth Rate on the Methane Concentration in the Hot Filament Chemical Vapor Deposition Process

Materials ◽  
2021 ◽  
Vol 14 (2) ◽  
pp. 426
Author(s):  
Byeong-Kwan Song ◽  
Hwan-Young Kim ◽  
Kun-Su Kim ◽  
Jeong-Woo Yang ◽  
Nong-Moon Hwang
Keyword(s):  
Growth Rate ◽  
Chemical Vapor Deposition ◽  
Vapor Deposition ◽  
Methane Concentration ◽  
Chemical Vapor ◽  
Diamond Growth ◽  
Lower Growth ◽  
Filament Temperature ◽  
Diamond Phase ◽  
Hot Filament

Although the growth rate of diamond increased with increasing methane concentration at the filament temperature of 2100 °C during a hot filament chemical vapor deposition (HFCVD), it decreased with increasing methane concentration from 1% CH4 –99% H2 to 3% CH4 –97% H2 at 1900 °C. We investigated this unusual dependence of the growth rate on the methane concentration, which might give insight into the growth mechanism of a diamond. One possibility would be that the high methane concentration increases the non-diamond phase, which is then etched faster by atomic hydrogen, resulting in a decrease in the growth rate with increasing methane concentration. At 3% CH4 –97% H2, the graphite was coated on the hot filament both at 1900 °C and 2100 °C. The graphite coating on the filament decreased the number of electrons emitted from the hot filament. The electron emission at 3% CH4 –97% H2 was 13 times less than that at 1% CH4 –99% H2 at the filament temperature of 1900 °C. The lower number of electrons at 3% CH4 –97% H2 was attributed to the formation of the non-diamond phase, which etched faster than diamond, resulting in a lower growth rate.

Graphene adlayer growth between nonepitaxial graphene and Ni(111) substrate: a promising theoretical scheme

2020 ◽  
Author(s):  
Lijuan Meng ◽  
Jinlian Lu ◽  
Yujie Bai ◽  
Lili Liu ◽  
Tang Jingyi ◽  
...  
Keyword(s):  
Molecular Dynamics ◽  
Density Functional Theory ◽  
Chemical Vapor Deposition ◽  
Molecular Dynamics Simulations ◽  
Vapor Deposition ◽  
Density Functional ◽  
Chemical Vapor ◽  
Density Functional Theory Calculations ◽  
Functional Theory ◽  
Dynamics Simulations

Understanding the fundamentals of chemical vapor deposition bilayer graphene growth is crucial for its synthesis. By employing density functional theory calculations and classical molecular dynamics simulations, we have investigated the...

scholarly journals A reactive molecular dynamics study on the mechanical properties of a recently synthesized amorphous carbon monolayer converted into a nanotube/nanoscroll

2021 ◽  
Author(s):  
Marcelo Lopes Pereira Junior ◽  
Wiliam Ferreira da Cunha ◽  
Douglas Soares Galvão ◽  
Luiz Antonio Ribeiro Junior
Keyword(s):  
Mechanical Properties ◽  
Molecular Dynamics ◽  
Chemical Vapor Deposition ◽  
Amorphous Carbon ◽  
Vapor Deposition ◽  
Chemical Vapor ◽  
Free Standing ◽  
Reactive Molecular Dynamics

Recently, laser-assisted chemical vapor deposition has been used to synthesize a free-standing, continuous, and stable monolayer amorphous carbon (MAC).

Deposition and Crystallisation Behaviour of Amorphous Silicon Thin Films Obtained by Pyrolysis of Disilane Gas at Very Low Pressure

1994 ◽  
Vol 345 ◽  
Author(s):  
T. Kretz ◽  
D. Pribat ◽  
P. Legagneux ◽  
F. Plais ◽  
O. Huet ◽  
...  
Keyword(s):  
Activation Energy ◽  
Growth Rate ◽  
Amorphous Silicon ◽  
Vapor Deposition ◽  
Electrical Conductance ◽  
Chemical Vapor ◽  
Crystalline Fraction ◽  
Silicon Thin Films ◽  
Crystallisation Behaviour

AbstractHigh purity amorphous silicon layers were obtained by ultrahigh vacuum (millitorr range) chemical vapor deposition (UHVCVD) from disilane gas. The crystalline fraction of the films was monitored by in situ electrical conductance measurements performed during isothermal annealings. The experimental conductance curves were fitted with an analytical expression, from which the characteristic crystallisation time, tc, was extracted. Using the activation energy for the growth rate extracted from our previous work, we were able to determine the activation energy for the nucleation rate for the analysed-films. For the films including small crystallites we have obtained En ∼ 2.8 eV, compared to En ∼ 3.7 eV for the completely amorphous ones.

Correlations for Interaction Layer Growth in U-Mo/Al Dispersion Fuels

2017 ◽  
Vol 375 ◽  
pp. 29-39
Author(s):  
Boris A. Tarasov ◽  
Stepan N. Nikitin ◽  
Dmitry P. Shornikov ◽  
Maria S. Tarasova ◽  
Igor I. Konovalov
Keyword(s):  
Growth Rate ◽  
Growth Process ◽  
Aluminum Matrix ◽  
Layer Growth ◽  
Radiation Diffusion ◽  
Fission Rate ◽  
Interaction Layer ◽  
The Matrix ◽  
Mechanism And Kinetics ◽  
Kinetics Of

Paper presents the results of the growth rate of the interaction layer of uranium-molybdenum dispersed fuel in aluminum matrix and influence of silicon alloying on it. The growth process of amorphous interaction layer depends on the radiation diffusion which is proportional to the fission rate in the power of 1⁄4. The alloying of the matrix by silicon does not lead to a change in the mechanism and kinetics of the interaction layer growth, but only slows it down.

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