Temperature Dependence of the Kinetics of Silicon Amorphization by He Ion Implantation

1992 ◽  
Vol 279 ◽  
Author(s):  
L. Laânab ◽  
A. Roumili ◽  
M. M. Faye ◽  
N. Gessinn ◽  
A. Claverie
Keyword(s):  
Energy Density ◽  
Ion Implantation ◽  
Substrate Temperature ◽  
Temperature Dependence ◽  
Drastic Change ◽  
Density Model ◽  
Different Types ◽  
Higher Temperature ◽  
Kinetics Of ◽  
Critical Damage

ABSTRACTWe have studied by XTEM the kinetics of Si amorphization by light ion implantation (He) as a function of substrate temperature. The analysis of these kinetics has been performed within the framework of the “Critical Damage Energy Density” model which is shown to apply for temperatures up to 250 K. There is a drastic change in the efficiency of the amorphization process at about 175 K. These results are discussed and explained by considering the different types of defects (I, V, I2, V2, complexes…) that can be stabilized in c-Si depending on the temperature. Above 150 K, the amorphization proceeds through the accumulation of interstitials and vacancies while at higher temperature it proceeds through the accumulation of di-interstitials and di-vacancies left in the network after annihilation and recombination of the Frenkel pairs created by the bombardment.

An Analysis of the Temperature Dependence of Photosynthesis Considering the Kinetics of RuP2 Carboxylase and the Pool of RuP2 in Intact Leaves

1988 ◽  
Vol 15 (6) ◽  
pp. 737 ◽  
Author(s):  
VM Oja ◽  
BH Rasulov ◽  
AH Laisk
Keyword(s):  
Temperature Dependence ◽  
Short Exposure ◽  
Co2 Uptake ◽  
Mesophyll Conductance ◽  
Mesophyll Cells ◽  
Binding Reaction ◽  
Cotton Plants ◽  
Different Temperatures ◽  
Higher Temperature ◽  
Kinetics Of

Sunflower and cotton plants were grown in growth boxes at 460 �mol m-2 s-1. The mesophyll conductance in N2, the assimilatory charge (post-illumination CO2 uptake) and the CO2 capacity (the solubility of CO2 + HCO3- + CO32-) were measured at different temperatures. The mesophyll conductance had its maximum at 29-30°C in sunflower leaves and rapidly declined at higher and lower temperatures. In cotton, the maximum occurred at a somewhat higher temperature. The assimilatory charge changed in parallel with the mesophyll conductance. When the assimilatory charge was measured after a short exposure to CO2-free N2, it remained constant at lower temperatures and declined only at superoptimal temperatures. As the assimilatory charge reflects the RuP2 pool in the leaf, the temperature dependence of the mesophyll conductance at a constant assimilatory charge reveals the actual activation energy of the CO2 binding reaction of carboxylase (together with the CO2 transport conductance in the liquid phase of mesophyll cells) which was 29 kJ mol-� for both species. At superoptimal temperatures, the primary cause for the reversible decrease of photosynthesis was a decrease in the assimilatory charge (RuP2 pool). The decrease cannot be caused by an inadequate rate of RuP2 resynthesis but is, presumably, the result of either too rapid drainage of triosephosphates to the cytosol from chloroplasts or de-energisation of thylakoids at high temperatures.

Temperature Dependence and Annealing Behaviour of Hf Implanted (100)Si: HfSi 2 Synthesis

1995 ◽  
Vol 402 ◽  
Author(s):  
M. R. Da Silva ◽  
A. A. Melo ◽  
J. C. Soares ◽  
M. F. Da Silva ◽  
R. Moons ◽  
...  
Keyword(s):  
Ion Implantation ◽  
Substrate Temperature ◽  
Temperature Dependence ◽  
Subsequent Annealing ◽  
High Fluence ◽  
Annealing Behaviour

AbstractWe investigated the formation of a buried HfSi2 layer by high fluence ion implantation of isotopically mass separated 179–180 Hf+ on heated silicon (100) substrates. It is shown that for the substrate temperature of 600°C a buried HfSi 2 layer is formed. By subsequent annealing at 1000 °C a continuous 12 nm HfSi2 layer on the Si surface is formed followed by 130 nm big almost spherodized HfSi2 ellipsoid and 80 nm small HfSi2 and Si grains. The annealing of samples implanted at lower temperatures show that HfSi2 is also formed but with reduced yield. A summary of the relevant data is presented.

A Continuous Heterogeneous Model for the Crystalline to Amorphous Transition in Ion Implanted Semiconductors : Relationship to the “Critical Damage Energy Density” Model

1991 ◽  
Vol 230 ◽  
Author(s):  
C. Vieu ◽  
A. Claverie ◽  
J. Faure ◽  
J. Beauvillain
Keyword(s):  
Energy Density ◽  
Damage Accumulation ◽  
Density Model ◽  
High Dose ◽  
Heterogeneous Model ◽  
New Approach ◽  
Critical Damage ◽  
Ion Implanted

AbstractA method is presented for calculating amorphization doses of ion implanted semiconductors, based on a continuous heterogeneous description of damage accumulation. This new approach is compared to the classical “critical damage energy density” (CDED) model. For high dose implantations the equivalence of both descriptions is formally established. It is proposed that the main limitation of the CDED model lies in the linear additivity of damage rather than the homogeneous damage build-up.

Studies on the Behavior Some Paints in Electro-insulating Fluid Based on Vegetable Esters

2018 ◽  
Vol 69 (5) ◽  
pp. 1139-1144
Author(s):  
Iosif Lingvay ◽  
Adriana Mariana Bors ◽  
Livia Carmen Ungureanu ◽  
Valerica Stanoi ◽  
Traian Rus
Keyword(s):  
Structural Changes ◽  
Oxidation Processes ◽  
High Oleic ◽  
Painting Materials ◽  
Insulating Paper ◽  
Different Types ◽  
Mechanism And Kinetics ◽  
Kinetics Of ◽  
Natural Ester

For the purpose of using three different types of painting materials for the inner protection of the transformer vats, their behavior was studied under actual conditions of operation in the transformer (thermal stress in electro-insulating fluid based on the natural ester in contact with copper for electro-technical use and electro-insulating paper). By comparing determination of the content in furans products (HPLC technique) and gases formed (by gas-chromatography) in the electro-insulating fluid (natural ester with high oleic content) thermally aged at 130 �C to 1000 hours in closed glass vessels, it have been found that the presence the investigated painting materials lead to a change in the mechanism and kinetics of the thermo-oxidation processes. These changes are supported by oxygen dissolved in oil, what leads to decrease both to gases formation CO2, CO, H2, CH4, C2H4 and C2H6) and furans products (5-HMF, 2-FOL, 2 -FAL and 2-ACF). The painting materials investigated during the heat treatment applied did not suffer any remarkable structural changes affecting their functionality in the electro-insulating fluid based on vegetable esters.

Kinetics of carbon monoxide methanation on a Ni/SiO2 catalyst

1990 ◽  
Vol 55 (7) ◽  
pp. 1678-1685
Author(s):  
Vladimír Stuchlý ◽  
Karel Klusáček
Keyword(s):  
Carbon Monoxide ◽  
Reaction Rate ◽  
Catalyst Activity ◽  
Adsorbed Hydrogen ◽  
Reaction Products ◽  
Co Methanation ◽  
Molar Ratios ◽  
Rate Determining Step ◽  
Higher Temperature ◽  
Kinetics Of

Kinetics of CO methanation on a commercial Ni/SiO2 catalyst was evaluated at atmospheric pressure, between 528 and 550 K and for hydrogen to carbon monoxide molar ratios ranging from 3 : 1 to 200 : 1. The effect of reaction products on the reaction rate was also examined. Below 550 K, only methane was selectively formed. Above this temperature, the formation of carbon dioxide was also observed. The experimental data could be described by two modified Langmuir-Hinshelwood kinetic models, based on hydrogenation of surface CO by molecularly or by dissociatively adsorbed hydrogen in the rate-determining step. Water reversibly lowered catalyst activity and its effect was more pronounced at higher temperature.

scholarly journals Ice Coverage Induced by Depositing a Water Drop onto the Supercooled Substrate at Extreme Low Vapor Pressure

Crystals ◽  
2021 ◽  
Vol 11 (6) ◽  
pp. 691
Author(s):  
Yugang Zhao ◽  
Zichao Zuo ◽  
Haibo Tang ◽  
Xin Zhang
Keyword(s):  
Vapor Pressure ◽  
Substrate Temperature ◽  
Water Drop ◽  
Industrial Processes ◽  
Aircraft Icing ◽  
Ice Coverage ◽  
Fundamental Understanding ◽  
Order Of Magnitude ◽  
The Impact ◽  
Kinetics Of

Icing/snowing/frosting is ubiquitous in nature and industrial processes, and the accretion of ice mostly leads to catastrophic consequences. The existing understanding of icing is still limited, particularly for aircraft icing, where direct observation of the freezing dynamics is inaccessible. In this work, we investigate experimentally the impact and freezing of a water drop onto the supercooled substrate at extremely low vapor pressure, to mimic an aircraft passing through clouds at a relatively high altitude, engendering icing upon collisions with pendant drops. Special attention is focused on the ice coverage induced by an impinging drop, from the perimeter pointing outward along the radial direction. We observed two freezing regimes: (I) spread-recoil-freeze at the substrate temperature of Ts = −15.4 ± 0.2 °C and (II) spread (incomplete)-freeze at the substrate temperature of Ts = −22.1 ± 0.2 °C. The ice coverage is approximately one order of magnitude larger than the frozen drop itself, and counterintuitively, larger supercooling yields smaller ice coverage in the range of interest. We attribute the variation of ice coverage to the kinetics of vapor diffusion in the two regimes. This fundamental understanding benefits the design of new anti-icing technologies for aircraft.

scholarly journals Pyrolysis and Oxidation of PAN in Dry Air. Thermoanalytical Methods

1970 ◽  
Vol 17 (1) ◽  
pp. 38-42
Author(s):  
Anna BIEDUNKIEWICZ ◽  
Pawel FIGIEL ◽  
Marta SABARA
Keyword(s):  
Temperature Increase ◽  
Heating Rates ◽  
Linear Change ◽  
Dry Air ◽  
Isothermal Conditions ◽  
Gaseous Products ◽  
Heterogeneous Processes ◽  
Temperature Ranges ◽  
Higher Temperature ◽  
Kinetics Of

The results of investigations on pyrolysis and oxidation of pure polyacrylonitrile (PAN) and its mixture with N,N-dimethylformamide (DMF) under non-isothermal conditions at linear change of samples temperature in time are presented. In each case process proceeded in different way. During pyrolysis of pure PAN the material containing mainly the product after PAN cyclization was obtained, while pyrolysis of PAN+DMF mixture gave the product after cyclization and stabilization. Under conditions of measurements, in both temperature ranges, series of gaseous products were formed.For the PAN-DMF system measurements at different samples heating rates were performed. The obtained results were in accordance with the kinetics of heterogeneous processes theory. The process rates in stages increased along with the temperature increase, and TG, DTG and HF function curves were shifted into higher temperature range. This means that the process of pyrolysis and oxidation of PAN in dry air can be carried out in a controlled way.http://dx.doi.org/10.5755/j01.ms.17.1.246

Kinetics of Ion-Pair Effect of Aquation of Bromopentaammine Cobalt(III) Complex in Different Dicarboxylate Media

2011 ◽  
Vol 324 ◽  
pp. 166-169 ◽  
Author(s):  
Farah Zeitouni ◽  
Gehan El-Subruiti ◽  
Ghassan Younes ◽  
Mohammad Amira
Keyword(s):  
Free Energy ◽  
Solvent Effect ◽  
Compensation Effect ◽  
Ion Pairing ◽  
Reaction Rates ◽  
Ion Pair ◽  
Free Energy Of Activation ◽  
Different Types ◽  
Different Temperatures ◽  
Kinetics Of

The rate of aquation of bromopentaammine cobalt(III) ion in the presence of different types of dicarboxylate solutions containing tert-butanol (40% V/V) have been measured spectrophotometrically at different temperatures (30-600°C) in the light of the effects of ion-pairing on reaction rates and mechanism. The thermodynamic and extrathermodynamic parameters of activation have been calculated and discussed in terms of solvent effect on the ion-pair aquation reaction. The free energy of activation ∆Gip* is more or less linearly varied among the studied dicarboxylate ion-pairing ligands indicating the presence of compensation effect between ∆Hip* and ∆Sip*. Comparing the kip values with respect of different buffers at 40% of ter-butanol is introduced.

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