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Wyszukujesz frazę "Khan, S. M. M." wg kryterium: Autor


Wyświetlanie 1-4 z 4
Tytuł:
Study of Glass Transition and Crystallization Behavior in $Ga_{15}Se_{85 - x}Pb_x$ (0 ≤ x ≤ 6) Chalcogenide Glasses
Autorzy:
Khan, Z.
Khan, S.
Alvi, M.
Powiązania:
https://bibliotekanauki.pl/articles/1400308.pdf
Data publikacji:
2013-01
Wydawca:
Polska Akademia Nauk. Instytut Fizyki PAN
Tematy:
61.43.Dq
61.05.cp
64.70.p
64.70.dg
65.60.+a
Opis:
There has been a growing interest in the synthesis and characterization of amorphous chalcogenide glasses due to their importance in preparing electronic memories, grating, switching devices and their optical applications as good IR transmitting materials. The study of the glass transformations and crystallization processes in the amorphous systems is interesting not only from the fundamental aspect of establishing the reaction mechanism of crystal nucleation and growth, but also from a technological point of view. The present research work is concentrated on the study of glass transition and crystallization behavior in $Ga_{15}Se_{85 - x}Pb_x$ with x=0, 3, and 6 chalcogenide glasses by differential scanning calorimetry. Their amorphous nature has been verified by X-ray diffraction. The differential scanning calorimetry experiments were performed at different continuous heating rates (5 to 25 K/min). The glass transition temperature (T_{g}) and crystallization temperature $(T_{c})$ of these glasses has been determined from differential scanning calorimetry thermograms. The dependence of $T_{g}$ and $T_{c}$ on the heating rate (β) has been used for the determination of different crystallization parameters such as the activation energy of crystallization (Δ $E_{c}$), the activation energy for structural relaxation (Δ $E_{t}$) and the order parameter (n). The results of crystallization were discussed on the basis of different models such as Kissinger's approach and modification for non-isothermal crystallization in addition to Johnson, Mehl, Ozawa and Avrami.
Źródło:
Acta Physica Polonica A; 2013, 123, 1; 80-86
0587-4246
1898-794X
Pojawia się w:
Acta Physica Polonica A
Dostawca treści:
Biblioteka Nauki
Artykuł
Tytuł:
Two-Step Martensitic Transformation in an Aged $Ti_{50}Ni_{15}Pd_{25}Cu_{10}$ High Temperature Shape Memory Alloys
Autorzy:
Rehman, S.
Khan, M.
Nusair Khan, A.
Ali, L.
Imran Jaffery, S.
Powiązania:
https://bibliotekanauki.pl/articles/1401938.pdf
Data publikacji:
2015-08
Wydawca:
Polska Akademia Nauk. Instytut Fizyki PAN
Tematy:
81.30.Kf
Opis:
Multi-step martensitic transformation in an aged Ni-rich binary NiTi shape memory alloy is considered as usual behavior during transformation from austenite to martensite phase; from (austenite) B2 to R-phase and then R-phase to B19' (monoclinic). However, for equi-atomic NiTi-based quaternary high temperature shape memory alloy, two-step martensitic transformation was detected for the first time. The $Ti_{50}Ni_{15}Pd_{25}Cu_{10}$ high temperature shape memory alloys were investigated for the evolution of transformation temperatures at aging temperature of 550°C and 700°C. Aging at 550°C for 6 h resulted in significant reduction of phase transformation temperatures. During forward transformation from austenite to martensite, two-step martensitic transformation B2 → R and R → B19 (orthorhombic) was observed. By aging the alloy at 700°C for 6 h, no significant effect was found on phase transition behavior and transformation temperatures.
Źródło:
Acta Physica Polonica A; 2015, 128, 2B; B-125-B-127
0587-4246
1898-794X
Pojawia się w:
Acta Physica Polonica A
Dostawca treści:
Biblioteka Nauki
Artykuł
Tytuł:
Luminescence of Highly Excited Nonpolar a-Plane GaN and AlGaN/GaN Multiple Quantum Wells
Autorzy:
Juršėnas, S.
Kuokštis, E.
Miasojedovas, S.
Kurilčik, G.
Žukauskas, A.
Chen, C. Q.
Yang, J. W.
Adivarahan, V.
Asif Khan, M.
Powiązania:
https://bibliotekanauki.pl/articles/2038100.pdf
Data publikacji:
2004-06
Wydawca:
Polska Akademia Nauk. Instytut Fizyki PAN
Tematy:
78.55.Cr
73.21.Fg
72.20.Jv
78.47.+p
Opis:
Carrier recombination dynamics in polar and nonpolar GaN epilayers and GaN/AlGaN multiple quantum wells grown over sapphire substrates with various crystallographic orientation were studied under high photoexcitation by 20 ps laser pulses. The transient of luminescence featured a significant enhancement in nonradiative recombination of free carriers for nonpolar a-plane GaN epilayers compared to conventional c-plane samples. The epitaxial lateral overgrowth technique was demonstrated to significantly improve the quality of nonpolar a-plane films. This was proved by more than 40-fold increase in luminescence decay time (430 ps compared to ≤10 ps in the ordinary a-plane epilayer). Under high-excitation regime, a complete screening of built-in electric field by free carriers in multiple quantum wells grown on c-plane and r-plane sapphire substrates was achieved. Under such high excitation, luminescence efficiency and carrier lifetime of multiple quantum wells was shown to be determined by the substrate quality.
Źródło:
Acta Physica Polonica A; 2004, 105, 6; 567-573
0587-4246
1898-794X
Pojawia się w:
Acta Physica Polonica A
Dostawca treści:
Biblioteka Nauki
Artykuł
Tytuł:
Luminescence of Highly Photoexcited GaN Epilayers and Heterostructures Grown on Different Sapphire Crystal Planes
Autorzy:
Juršėnas, S.
Miasojedovas, S.
Kurilčik, G.
Liuolia, V.
Žukauskas, A.
Chen, C. Q.
Yang, J. W.
Kuokštis, E.
Adivarahan, V.
Asif Khan, M.
Powiązania:
https://bibliotekanauki.pl/articles/2041736.pdf
Data publikacji:
2005-02
Wydawca:
Polska Akademia Nauk. Instytut Fizyki PAN
Tematy:
78.55.Cr
73.21.Fg
72.20.Jv
78.47.+p
Opis:
GaN epilayers and AlGaN/GaN multiple quantum wells grown by metalorganic chemical vapor deposition on different crystal planes (c, a, and r) of the sapphire substrate were studied by excitation intensity dependent and time-resolved photoluminescence. In polar multiple quantum wells grown on a- and c-planes, a blueshift of the luminescence band with increasing the excitation energy was observed, indicating that screening of built-in field by free carriers takes place, whereas in nonpolar r-plane grown multiple quantum wells, the luminescence band maintained an almost constant peak position. Full screening of built-in field was achieved at the excitation densities higher than 0.3 mJ/cm$\text{}^{2}$. Under conditions of screened built-in electric field the structures were characterized by carrier lifetime. It was shown that nonpolar multiple quantum wells suffer from high density of nonradiative traps that can be due to substrate related threading dislocations.
Źródło:
Acta Physica Polonica A; 2005, 107, 2; 235-239
0587-4246
1898-794X
Pojawia się w:
Acta Physica Polonica A
Dostawca treści:
Biblioteka Nauki
Artykuł
    Wyświetlanie 1-4 z 4

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