Nucleation and growth concepts applied to the formation of a stoichiometric compound in a gas phase: The case of MgO smoke

2011 ◽  
Vol 329 (1) ◽  
pp. 52-56 ◽  
Author(s):  
Slavica Stankic ◽  
Maeva Cottura ◽  
Dominique Demaille ◽  
Claudine Noguera ◽  
Jacques Jupille
Keyword(s):  
Gas Phase ◽  
Nucleation And Growth ◽  
Stoichiometric Compound

Quantitative Study of the Role of Supersaturation during Sublimation Growth on the Yield of 50 mm 3C-SiC

2015 ◽  
Vol 821-823 ◽  
pp. 77-80 ◽  
Author(s):  
Dominik Rankl ◽  
Valdas Jokubavicius ◽  
Mikael Syväjärvi ◽  
Peter J. Wellmann
Keyword(s):  
Gas Phase ◽  
Nucleation And Growth ◽  
Vapor Transport ◽  
Quasi Equilibrium ◽  
Equilibrium Thermodynamic ◽  
Large Area ◽  
X Ray ◽  
Thermodynamic Conditions ◽  
Sublimation Growth

We have investigated the growth of 3C-SiC using sublimation growth in the temperature range from 1800°C to 1950°C. The supersaturation was determined using numerical modeling of the temperature field and gas phase composition by applying quasi-equilibrium thermodynamic conditions. Analysis of the 3C-SiC yield was carried out by optical microscopy, optical absorption, Raman spectroscopy and x-ray analysis. Quantitative data on supersaturation are compared with most stable 3C-SiC nucleation and growth condition. Finally the application to large area growth in a physical vapor transport growth reactor is briefly addressed.

Nucleation and Growth in Vicinity of Growing Surface in Making Microcrystalline Silicon

1990 ◽  
Vol 192 ◽  
Author(s):  
Masami Nakata ◽  
Tatsuru Namikawa ◽  
Hajime Shirai ◽  
Jun-ichi Hanna ◽  
Isamu Shimizu
Keyword(s):  
Substrate Temperature ◽  
Gas Phase ◽  
Atomic Hydrogen ◽  
Nucleation And Growth ◽  
Microcrystalline Silicon ◽  
Gas Phase Reactions ◽  
Plasma Enhanced Cvd ◽  
Close Study

ABSTRACTA close study was conducted on microcrystalline Silicon (μc-Si) prepared by PE-CVD (Plasma Enhanced CVD) from SiF4 with the assistance of atomic hydrogen. The atomic hydrogen played a major role in either making precursors, SiFnHm (n+m=3), by gas phase reactions with the fragments, SiFn (≤3), or constructing Si-network in the vicinity of the growing surface. Proper conditions of nucleation were markedly different from those of growth with respect to parameters, flow of atomic hydrogen and substrate temperature.

Modelling nitriding of iron: From thermodynamics to residual stress

2004 ◽  
Vol 120 ◽  
pp. 21-23
Author(s):  
M. A.J. Somers
Keyword(s):  
Gas Phase ◽  
Nucleation And Growth ◽  
Stress Generation ◽  
Model Description ◽  
Iron Nitride ◽  
Gaseous Nitriding ◽  
State Diffusion ◽  
Long Range Ordering ◽  
Nitride Layers ◽  
Kinetics Of

The present article presents a few selected aspects of the modelling of gaseous nitriding of pure iron. After descriptions of the thermodynamics of the gas phase and the reactions at the gas/solid interface, a model description of the thermodynamics of $\gamma'-Fe_{\rm 4}N{\rm 1-x}$ is given, which takes the long-range ordering of nitrogen atoms into account. Subsequently, the kinetics of nucleation and growth of iron nitride layers is described in terms of the rates of the surface reactions and solid state diffusion. Thereafter, the mechanisms of stress generation in $\gamma'-Fe_{\rm 4}N{\rm 1-x}$ layers during nitriding are summarized. Finally, the model for stress development in $\gamma'-Fe_{\rm 4}N{\rm 1-x}$ layers is compared with published experimental work.

Nucleation and Growth of Gallium Oxide Tubes, Nanopaintbrushes and Nanowires from Molten Gallium

2002 ◽  
Vol 755 ◽  
Author(s):  
Shashank Sharma ◽  
Mahendra K. Sunkara ◽  
Uschi M. Graham ◽  
Burtron H. Davis
Keyword(s):  
Gas Phase ◽  
Tin Oxide ◽  
Gallium Oxide ◽  
Microwave Plasma ◽  
Nucleation And Growth ◽  
Oxide Nanowires ◽  
One Dimensional ◽  
Oxide Nanostructures ◽  
First Time ◽  
Synthesis Of Nanostructures

ABSTRACTWe have synthesized highly crystalline β-gallium oxide tubes, nanowires, and unique one-dimensional structures in the form of nanopaintbrushes using molten gallium and microwave plasma containing a mixture of monoatomic oxygen and hydrogen. Multiple nucleation and growth of gallium oxide nanostructures occurred directly out of molten gallium upon exposure to an appropriate composition of hydrogen and oxygen in the gas phase. Gallium oxide nanowires were 20 to 100 nm thick and tens to hundreds of microns long. In addition to these morphologies, we also report for the first time, non-template based synthesis of novel 2-D networks of crystalline gallium oxide nanowires and nanotubes. Demonstration of this technique with gallium oxide certainly presents a new route for synthesis of nanostructures of other important metal oxides such as indium oxide, tin oxide, and zinc oxide.

scholarly journals Recent progress in understanding particle nucleation and growth

1997 ◽  
Vol 352 (1350) ◽  
pp. 191-201 ◽  
Author(s):  
F. L. Eisele ◽  
P. H. McMurry
Keyword(s):  
Gas Phase ◽  
Growth Rates ◽  
Ultrafine Particles ◽  
Ultrafine Particle ◽  
Field Measurements ◽  
Particle Growth ◽  
Nucleation And Growth ◽  
Nucleation Theory ◽  
Alternative Mechanism ◽  
Particle Nucleation

In the past half decade, several new tools have become available for investigating particle nucleation and growth. A number of joint field and laboratory studies exploiting some of these new measurement capabilities will be described and new insights shared. the ability to measure OH, SO 2 , H 2 SO 4 and aerosol number and size distributions has made possible a comparison between H 2 SO 4 production and loss onto particles in continental air masses. In regions remote from urban emissions, agreement is typically quite good. In contrast, joint field measurements of nucleation precursors such as gas phase H 2 SO 4 and ultrafine particles suggest that classical bimolecular nucleation theory may not properly describe the tropospheric nucleation process. An alternative mechanism, possibly involving ammonia as a stabilizing agent for H 2 SO 4 /H 2 O molecular clusters is discussed. Finally, ultrafine particle measurements are shown to offer new opportunities for studying particle growth rates. Preliminary results suggest that in a remote continental air mass, gas phase H 2 SO 4 uptake is far too slow to explain observed growth rates.

AEM analysis of crystallization in Ti-based amorphous alloys

1983 ◽  
Vol 41 ◽  
pp. 270-271
Author(s):  
A.R. Pelton ◽  
A.F. Marshall ◽  
Y.S. Lee
Keyword(s):  
Magnetic Properties ◽  
Amorphous Alloys ◽  
Amorphous Materials ◽  
Isothermal Annealing ◽  
Amorphous Matrix ◽  
Nucleation And Growth ◽  
Current Interest ◽  
Amorphous Films ◽  
Electrical And Magnetic Properties

Amorphous materials are of current interest due to their desirable mechanical, electrical and magnetic properties. Furthermore, crystallizing amorphous alloys provides an avenue for discerning sequential and competitive phases thus allowing access to otherwise inaccessible crystalline structures. Previous studies have shown the benefits of using AEM to determine crystal structures and compositions of partially crystallized alloys. The present paper will discuss the AEM characterization of crystallized Cu-Ti and Ni-Ti amorphous films.Cu60Ti40: The amorphous alloy Cu60Ti40, when continuously heated, forms a simple intermediate, macrocrystalline phase which then transforms to the ordered, equilibrium Cu3Ti2 phase. However, contrary to what one would expect from kinetic considerations, isothermal annealing below the isochronal crystallization temperature results in direct nucleation and growth of Cu3Ti2 from the amorphous matrix.

Observations oh Nucleation and Growth of Voids in Nickel

1970 ◽  
Vol 28 ◽  
pp. 414-415
Author(s):  
J. L. Brimhall ◽  
H. E. Kissinger ◽  
B. Mastel
Keyword(s):  
High Purity ◽  
Growth Stage ◽  
Elevated Temperatures ◽  
Early Growth ◽  
Nucleation And Growth ◽  
Pure Nickel ◽  
Different Temperatures ◽  
Total Fluence ◽  
Neutron Exposure ◽  
Growth Of Voids

Some information on the size and density of voids that develop in several high purity metals and alloys during irradiation with neutrons at elevated temperatures has been reported as a function of irradiation parameters. An area of particular interest is the nucleation and early growth stage of voids. It is the purpose of this paper to describe the microstructure in high purity nickel after irradiation to a very low but constant neutron exposure at three different temperatures.Annealed specimens of 99-997% pure nickel in the form of foils 75μ thick were irradiated in a capsule to a total fluence of 2.2 × 1019 n/cm2 (E > 1.0 MeV). The capsule consisted of three temperature zones maintained by heaters and monitored by thermocouples at 350, 400, and 450°C, respectively. The temperature was automatically dropped to 60°C while the reactor was down.

Electrochemical nucleation and growth of copper on iron and aluminum: A TEM study of industrial copper cementation

1978 ◽  
Vol 36 (1) ◽  
pp. 454-455
Author(s):  
L.E. Murr ◽  
V. Annamalai
Keyword(s):  
Metal Surface ◽  
Copper Deposit ◽  
Nucleation And Growth ◽  
16Th Century ◽  
Electrochemical Reactions ◽  
Mine Shaft ◽  
De Re ◽  
Copper Precipitation ◽  
Electrochemical Nucleation ◽  
Interesting System

Georgius Agricola in 1556 in his classical book, “De Re Metallica”, mentioned a strange water drawn from a mine shaft near Schmölnitz in Hungary that eroded iron and turned it into copper. This precipitation (or cementation) of copper on iron was employed as a commercial technique for producing copper at the Rio Tinto Mines in Spain in the 16th Century, and it continues today to account for as much as 15 percent of the copper produced by several U.S. copper companies.In addition to the Cu/Fe system, many other similar heterogeneous, electrochemical reactions can occur where ions from solution are reduced to metal on a more electropositive metal surface. In the case of copper precipitation from solution, aluminum is also an interesting system because of economic, environmental (ecological) and energy considerations. In studies of copper cementation on aluminum as an alternative to the historical Cu/Fe system, it was noticed that the two systems (Cu/Fe and Cu/Al) were kinetically very different, and that this difference was due in large part to differences in the structure of the residual, cement-copper deposit.

Fundamental Research into Thin Films in a Developing Country

1972 ◽  
Vol 30 ◽  
pp. 500-501
Author(s):  
J.A. Eades ◽  
E. Grünbaum
Keyword(s):  
Thin Films ◽  
Growth Process ◽  
Empirical Process ◽  
Nucleation And Growth ◽  
Research Groups ◽  
Film Research ◽  
Fundamental Research ◽  
Controlled Deposition ◽  
The One ◽  
The University

In the last decade and a half, thin film research, particularly research into problems associated with epitaxy, has developed from a simple empirical process of determining the conditions for epitaxy into a complex analytical and experimental study of the nucleation and growth process on the one hand and a technology of very great importance on the other. During this period the thin films group of the University of Chile has studied the epitaxy of metals on metal and insulating substrates. The development of the group, one of the first research groups in physics to be established in the country, has parallelled the increasing complexity of the field.The elaborate techniques and equipment now needed for research into thin films may be illustrated by considering the plant and facilities of this group as characteristic of a good system for the controlled deposition and study of thin films.

Growth of hematite by surface oxidation of olivine

1988 ◽  
Vol 46 ◽  
pp. 800-801
Author(s):  
S. McKernan ◽  
C. B. Carter
Keyword(s):  
Electron Microscope ◽  
Surface Oxidation ◽  
Thin Foil ◽  
Nucleation And Growth ◽  
Ion Milling ◽  
Annealed Material ◽  
Thin Foils ◽  
Natural Olivine ◽  
Approximate Composition ◽  
Second Phases

The oxidation of natural olivine has previously been performed on bulk samples and the reactions followed by preparation of TEM specimens from the annealed material. These results show that below ∼1000°C hematite and amorphous silica are formed, particularly around dislocations. At higher temperatures magnetite and some enstatite-like phase are formed. In both cases the olivine is left almost totally Fe depleted. By performing the oxidation on characterized thin TEM specimens it is possible to obtain more information on the nucleation and growth of the second phases formed. The conditions in a thin foil, however, are very different from those in the bulk especially with regard to surface effects. The nucleation of precipitates in particular may be expected to occur differently in these thin foils than in the bulk.TEM specimens of natural olivine (approximate composition Mg+Fe+Si2o4) which had been annealed at 1000°C for 1 hr were prepared by mechanical polishing and dimpling, followed by Ar ion milling to perforation. The specimens were characterized in the electron microscope and then heated in air in alumina boats to 900°C for between 30 and 180 minutes.

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