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Wyszukujesz frazę "nucleation and growth" wg kryterium: Wszystkie pola


Wyświetlanie 1-5 z 5
Tytuł:
Investigation on Nucleation Kinetics, Growth and Nonlinear Optical Properties of L-Cystine Hydrochloride Crystal
Autorzy:
Manivannan, D.
Kirubavathi, K.
Selvaraju, K.
Powiązania:
https://bibliotekanauki.pl/articles/1029827.pdf
Data publikacji:
2018-01
Wydawca:
Polska Akademia Nauk. Instytut Fizyki PAN
Tematy:
crystal growth
nucleation kinetics
optical materials
NLO
Opis:
The semiorganic nonlinear optical crystal of amino-carboxyl acid family, L-cystine hydrochloride (LCHCl) was successfully grown from its aqueous solution by the slow evaporation solution growth method. The solubility, metastable zone width and induction period were determined for the first time experimentally and there by the possibility of growing bulk crystals of LCHCl using deionized water as solvent. The induction period was recorded for the different supersaturation ratios (S=1.2, 1.3, 1.4, and 1.5), which reveals that the induction period of LCHCl decreases with increase in supersaturation. The nucleation kinetic parameters such as critical free energy, change of volume free energy, critical radius, number of molecules in the critical nucleus and nucleation rate have been evaluated for LCHCl crystals. The interfacial energy values of LCHCl were determined for different supersaturation ratio by means of varying temperatures. The single crystal X-ray diffraction gives the lattice parameters value of the grown crystals. The second harmonic generation efficiency was confirmed by the Kurtz-Perry powder method. The laser damage threshold energy of the grown crystal indicates that grown crystal has excellent resistance to laser radiation also compared with known other nonlinear optical crystals.
Źródło:
Acta Physica Polonica A; 2018, 133, 1; 63-67
0587-4246
1898-794X
Pojawia się w:
Acta Physica Polonica A
Dostawca treści:
Biblioteka Nauki
Artykuł
Tytuł:
Modelling and identification of voids nucleation and growth effects in porous media plastic flow
Autorzy:
Nowak, Z.
Stachurski, A.
Powiązania:
https://bibliotekanauki.pl/articles/970581.pdf
Data publikacji:
2003
Wydawca:
Polska Akademia Nauk. Instytut Badań Systemowych PAN
Tematy:
optymalizacja globalna
regresja nieliniowa
programowanie nieliniowe
plastic flow of voided media
material functions identification
global optimization
nonlinear regression
nonlinear programming
Akaike and FPE tests for nested models
Vuong test for nonnested models
Opis:
In the paper the effects of nucleation and growth of voids in the plastic porous media are investigated. Three different forms of the model are considered: the augmented Gurson model (total porosity model) with variable nucleation and growth material function, the same model with constant growth material function and the separated porosity model. The identification of the material functions parameters is based on Fischer's experimental data set for axisymmetric tension of steel specimens and formulated as a typical nonlinear regression problem using the least squares approach. The resulting minimization problem is solved by means of our own implementation of the Boender at al. global minimization method. Calculations and statistical analysis (Akaike, FPE and Vuong tests) have led to a conclusion that the growth material function in the uniaxial tension for steel may be assumed to be constant although not necessarily equal to one.
Źródło:
Control and Cybernetics; 2003, 32, 4; 819-849
0324-8569
Pojawia się w:
Control and Cybernetics
Dostawca treści:
Biblioteka Nauki
Artykuł
Tytuł:
Nucleation and Crystal Growth of Cu on Ir Tips Under Ultra-High Vacuum and in the Presence of Oxygen
Autorzy:
Zuber, S. M.
Ciszewski, A.
Powiązania:
https://bibliotekanauki.pl/articles/2013288.pdf
Data publikacji:
2000-04
Wydawca:
Polska Akademia Nauk. Instytut Fizyki PAN
Tematy:
61.16.Fk
81.15.Ef
68.35.Bs
Opis:
Results concerning the morphology of Cu adsorption layers deposited from vapor under ultrahigh vacuum on Ir tip and the influence of oxygen on this morphology are reported. The method employed was field electron emission microscopy. It was found that the presence of oxygen decreases the copper wettability of iridium. Preadsorption of oxygen on the Ir surface is followed by an increase in cohesion interaction between atoms of the Cu deposited onto the tip at room temperature. Coadsorption of Cu and O on the Ir tip surface at liquid nitrogen temperature, when followed by gradually heating the adlayer, results in crystallization of the deposit in the temperature range from 430 K to about 700 K. Some evidence indicates the formation of Cu$\text{}_{2}$O with a high degree of crystallinity under these conditions. Cu and O coadsorption on the Ir surface at a temperature higher than 1090 K leads to selective accumulation of Cu on the {111} faces and to formation of epitaxial crystals which are oriented to the substrate in the same manner as the Cu crystals grown at ultra-high vacuum from Cu flux containing no oxygen. Oxygen incorporated into the Cu beam interact preferentially with {011} and {001} Ir faces, where it can produce oxide layers.
Źródło:
Acta Physica Polonica A; 2000, 97, 4; 681-692
0587-4246
1898-794X
Pojawia się w:
Acta Physica Polonica A
Dostawca treści:
Biblioteka Nauki
Artykuł
Tytuł:
Optimisation of LT-GaN nucleation layer growth conditions for the improvement of electrical and optical parameters of GaN layers
Autorzy:
Wośko, Mateusz
Powiązania:
https://bibliotekanauki.pl/articles/174388.pdf
Data publikacji:
2019
Wydawca:
Politechnika Wrocławska. Oficyna Wydawnicza Politechniki Wrocławskiej
Tematy:
GaN
nucleation
recrystallization
metalorganic chemical vapor deposition
nitrides
LED
MSM
MESFET devices
Opis:
In this work we present the influence of low temperature gallium nitride (LT-GaN) nucleation layer deposition and recrystallization conditions on the electrical and optical properties of buffer and active layer of metal–semiconductor field-effect transistor (MESFET) structure. MESFET structures were used to investigate the properties of bulk materials that determine also the performance of many type GaN based devices, like light emitting diodes (LEDs), high electron mobility transistors (HEMTs) and metal–semiconductor–metal (MSM) detectors. The set of n-GaN/u-GaN/sapphire structures using different nucleation LT-GaN layers thickness and different annealing times was deposited using AIXTRON CCS epitaxial system. In contrast to typical procedure, the high resistive GaN buffer layer was not obtained by intentional Fe/Mg doping, but by specific adjustment of GaN nucleation conditions and recrystallization process parameters that introduce carbon atoms in epitaxial layers, that serve as donors. Generally, low pressure (below 200 mbar) in a reactor chamber, during initial stages of nucleation and recrystallization as well as HT-GaN epitaxy, promotes the growth of high resistive material. Obtained results show that annealing/recrystallization time of LT-GaN has a significant impact on the electrical and optical properties of GaN buffer layers. Longer annealing periods tend to promote crystallization of material with higher electron mobility and higher Si dopant incorporation/activation while maintaining high resistivity in u-GaN buffer area. It was shown that the dimensions of the GaN islands, that could be influenced by the duration of an annealing step of LT-GaN growth, have no impact on the HT-GaN buffer layer coalescence process and material resistivity, but influences mainly electrical properties of active n-GaN layer. Author suggests that the key parameters that are determining the buffer resistivity are the pressure and temperature during LT-GaN annealing and buffer layer coalescence. The influence of GaN island diameters, after LT-GaN annealing, on the u-GaN resistivity was not confirmed.
Źródło:
Optica Applicata; 2019, 49, 1; 167-176
0078-5466
1899-7015
Pojawia się w:
Optica Applicata
Dostawca treści:
Biblioteka Nauki
Artykuł
Tytuł:
Reduction of Industrial Nickel Oxides with a Hydrogen Bearing Gas Between 523 and 673K
Autorzy:
Plascencia, G.
Powiązania:
https://bibliotekanauki.pl/articles/352276.pdf
Data publikacji:
2018
Wydawca:
Polska Akademia Nauk. Czytelnia Czasopism PAN
Tematy:
nickel oxides reduction
hydrogen reduction
Avrami-Erofeyev kinetic model
nucleation and growth
activation energy
Opis:
Reduction of three industrial nickel oxides (Goro, Tokyo and Sinter 75) with a hydrogen bearing gas was revisited in the temperature interval from 523 to 673 K (250 to 400°C). A pronounced incubation period is observed in the temperature interval tested. This period decreases as the reduction temperature increases. Thermogravimetric data of these oxides were fitted using the Avrami-Erofeyev kinetic model. The reduction of these oxides is controlled by a nucleation and growth mechanism of metallic nickel over the oxides structure. Rate kinetic constants were re-evaluated and the activation energy for the reduction of these oxides was re-calculated.
Źródło:
Archives of Metallurgy and Materials; 2018, 63, 2; 781-789
1733-3490
Pojawia się w:
Archives of Metallurgy and Materials
Dostawca treści:
Biblioteka Nauki
Artykuł
    Wyświetlanie 1-5 z 5

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