“…It shows a sigmoidal curve, typical for zeolites crystallization. As mentioned previously, this behavior can be described by the KJMA model where n can be obtained from the slope of a Sharp–Hancock graph by taking the double logarithm of eq , as expressed in eq …”
We studied the crystallization of
ZSM-5 zeolite by hydrothermal
treatment in the absence of organic structure directing agents (OSDA)
at 170, 180, and 190 °C, using Perlite as a natural source of
SiO2 and Al2O3. Experimental data
were fitted by nonlinear regression following the Kolmogorov–Johnson–Mehl–Avrami’s
nucleation/crystallization model in order to calculate kinetic constants
(k), induction periods (t
0), and Avrami’s exponents (n). A constant
value of n = 3.4 implicates the same mechanism in
the studied range of temperature with a contribution from three dimensions
to crystal growth and a nucleation that may include both sporadic
and instantaneous mechanisms. Different stages of crystallization
were clearly differentiated, and specific kinetics parameters were
calculated. Compared with previously reported preparations, we found
that the synthesis from Expanded Perlite is a promising alternative
as it not only avoids the use of OSDA but also consumes less energy.
Finally, a five steps crystallization mechanism has been proposed.
“…It shows a sigmoidal curve, typical for zeolites crystallization. As mentioned previously, this behavior can be described by the KJMA model where n can be obtained from the slope of a Sharp–Hancock graph by taking the double logarithm of eq , as expressed in eq …”
We studied the crystallization of
ZSM-5 zeolite by hydrothermal
treatment in the absence of organic structure directing agents (OSDA)
at 170, 180, and 190 °C, using Perlite as a natural source of
SiO2 and Al2O3. Experimental data
were fitted by nonlinear regression following the Kolmogorov–Johnson–Mehl–Avrami’s
nucleation/crystallization model in order to calculate kinetic constants
(k), induction periods (t
0), and Avrami’s exponents (n). A constant
value of n = 3.4 implicates the same mechanism in
the studied range of temperature with a contribution from three dimensions
to crystal growth and a nucleation that may include both sporadic
and instantaneous mechanisms. Different stages of crystallization
were clearly differentiated, and specific kinetics parameters were
calculated. Compared with previously reported preparations, we found
that the synthesis from Expanded Perlite is a promising alternative
as it not only avoids the use of OSDA but also consumes less energy.
Finally, a five steps crystallization mechanism has been proposed.
“…Crystallization kinetics of Cu 55 Hf 45 and Cu 50 Zr 50 glassy alloy was studied . Meanwhile, influence of minor additions of Si on the crystallization kinetics of Cu 55 Hf 45 metallic glasses was reported . In this paper, the isothermal crystallization of Cu 55 Zr 45 binary glassy alloy will be investigated to further understand the crystallization process of binary glassy alloy.…”
Section: Introductionmentioning
confidence: 99%
“…13,14 Meanwhile, influence of minor additions of Si on the crystallization kinetics of Cu 55 Hf 45 metallic glasses was reported. 15 In this paper, the isothermal crystallization of Cu 55 Zr 45 binary glassy alloy will be investigated to further understand the crystallization process of binary glassy alloy. In isothermal crystallization condition, metallic glass is heated to the annealing temperatures to hold for a period of time for crystallization at a constant rate.…”
The crystallization kinetics of Cu55Zr45 (at%) glassy alloy is studied under isothermal condition using differential scanning calorimetry (DSC). The plot of correlation between the crystallized volume fraction α and annealing time t shows a sigmoid‐type curve, which is steeper with higher annealing temperature. Furthermore, in isothermal crystallization condition, local activation energy Eα values, determined using the Arrhenius equation, range from 181.1 to 187.8 kJ/mol, which is nearly a constant. The local Avrami exponent n(α) values, obtained by the Johnson‐Mehl‐Avrami equation, which range from 2.2 to 4.0 at different annealing temeperatures, which indicates that the crystallization mechanism is diffusion‐controlled transformation. Moreover, n(α) becomes greater with increasing annealing temperature, which indicates that annealing temperature can affect nucleation rate and growth type.
“…[4] Researchers have improved the GFA and developed new BMGs by adding small amounts of alloying element(s) starting from the best binary glass-forming alloys. [5][6][7][8] For example, Figueroa et al [9] found that the GFA of Cu 55 Hf 45 alloys could be maximized with the addition of 2.0-at.% Si, and that the supercooled liquid region was increased by 15 K relative to the matrix alloy. Cai et al [6] revealed that the substitution of Zr in Cu 50 Zr 50 alloy by Al could remarkably increase the GFA, and the best glass-forming alloy was Cu 50 Zr 47 Al 3 .…”
Section: Introductionmentioning
confidence: 99%
“…Cai et al [6] revealed that the substitution of Zr in Cu 50 Zr 50 alloy by Al could remarkably increase the GFA, and the best glass-forming alloy was Cu 50 Zr 47 Al 3 . The increase in GFA via minor doping has been explained using methods involving thermodynamics (e.g., thermal stability) [9,10] and kinetics (e.g., dynamic slowing down). [11] However, the atomic structural mechanism of the GFA of element-doped liquid alloys remains poorly understood because of experimental limitations.…”
The heredity of clusters in rapidly cooled (Zr50Cu50)100 – x
Al
x
melts and its correlation with glass-forming ability (GFA) are studied via molecular dynamics simulations. Pair distribution function and the largest standard cluster (LSC) are adopted to characterize the local atomic structures in the (Zr50Cu50)100 – x
Al
x
systems. The [12/555] icosahedra and their medium-range order (IMRO) play an important role in forming (Zr50Cu50)100 – x
Al
x
metallic glasses (MGs). The fraction of [12/555], the number of IMRO, and the maximum size of IMRO in MGs increase significantly with increasing x. A tracking study further reveals that the configuration heredity of icosahedral clusters starts from supercooled liquids. No direct correlation exists between the GFA and the onset temperature of continuous or stated heredity. Instead, a larger hereditary supercooled degree of icosahedra matches with better GFA of Al-doped Zr50Cu50 alloys.
scite is a Brooklyn-based organization that helps researchers better discover and understand research articles through Smart Citations–citations that display the context of the citation and describe whether the article provides supporting or contrasting evidence. scite is used by students and researchers from around the world and is funded in part by the National Science Foundation and the National Institute on Drug Abuse of the National Institutes of Health.