scholarly journals Short time dynamics determine glass forming ability in a glass transition two-level model: A stochastic approach using Kramers’ escape formula

2017 ◽  
Vol 146 (9) ◽  
pp. 094506 ◽  
Author(s):  
J. Quetzalcóatl Toledo-Marín ◽  
Gerardo G. Naumis
Keyword(s):  
Glass Transition ◽  
Stochastic Approach ◽  
Glass Forming Ability ◽  
Time Dynamics ◽  
Glass Forming ◽  
Level Model ◽  
Short Time ◽  
Two Level Model

Glass Formation and Glass Forming Ability of Alloys Near Eutectic Composition

2000 ◽  
Vol 644 ◽  
Author(s):  
Y. Li
Keyword(s):  
Glass Transition ◽  
Glass Formation ◽  
Eutectic Composition ◽  
Glass Forming Ability ◽  
Critical Section ◽  
Bulk Glass ◽  
Melting Behaviour ◽  
Eutectic Alloys ◽  
Section Thickness ◽  
Glass Forming

AbstractOnset temperature, Tm and offset temperature (liquidus) Tl of melting of a series of bulk glass forming alloys based on La, Mg, and Pd have been measured by studying systematically the melting behaviour of these alloys using DTA or DSC. Bulk metallic glass formation has been found to be most effective at or near their eutectic points and less effective for off-eutectic alloys. Reduced glass transition temperature Trg given by Tg/Tl is found to show a stronger correlation with critical cooling rate or critical section thickness for glass formation than Trg given by Tg/Tm.

Comments on “Fabrication of ternary Mg–Cu–Gd bulk metallic glass with high glass-forming ability under air atmosphere” [H. Men and D.H. Kim, J. Mater. Res. 18, 1502 (2003)]

2004 ◽  
Vol 19 (2) ◽  
pp. 427-428 ◽  
Author(s):  
Z.P. Lu ◽  
C.T. Liu
Keyword(s):  
Glass Transition ◽  
Metallic Glasses ◽  
Supercooled Liquid ◽  
Supercooled Liquid Region ◽  
Glass Forming Ability ◽  
Bulk Amorphous Alloy ◽  
Liquid Region ◽  
Glass Forming ◽  
Air Atmosphere ◽  
Acta Mater

A new Mg-based bulk amorphous alloy (i.e., Mg65Cu25Gd10) has successfully been developed by Men and Kim [H. Men and D.H. Kim, J. Mater. Res. 18, 1502 (2003)]. They showed that this alloy exhibits significantly improved glass-forming ability (GFA) in comparison with Mg65Cu25Y10 alloy. However, this improved GFA cannot be indicated by the supercooled liquid region ΔT and the reduced glass-transition temperature Trg. As shown in the current comment, the new parameter γ, Tx/(Tg + Tl) defined in our recent papers [Z.P. Lu and C.T. Liu, Acta Mater. 50, 3501 (2002); Z.P. Lu and C.T. Liu, Phys. Rev. Lett. 91, 115505 (2003)] can well gauge GFA for bulk metallic glasses, including the current Mg-based alloys.

scholarly journals Long-Term Physical (In)Stability of Spray-Dried Amorphous Drugs: Relationship with Glass-Forming Ability and Physicochemical Properties

Pharmaceutics ◽  
2019 ◽  
Vol 11 (9) ◽  
pp. 425 ◽  
Author(s):  
Edueng ◽  
Bergström ◽  
Gråsjö ◽  
Mahlin
Keyword(s):  
Glass Transition ◽  
Transition Temperature ◽  
Glass Transition Temperature ◽  
Physicochemical Properties ◽  
Physical Stability ◽  
Glass Forming Ability ◽  
Melt Quenching ◽  
Glass Forming ◽  
Spray Dried

This study shows the importance of the chosen method for assessing the glass-forming ability (GFA) and glass stability (GS) of a drug compound. Traditionally, GFA and GS are established using in situ melt-quenching in a differential scanning calorimeter. In this study, we included 26 structurally diverse glass-forming drugs (i) to compare the GFA class when the model drugs were produced by spray-drying with that when melt-quenching was used, (ii) to investigate the long-term physical stability of the resulting amorphous solids, and (iii) to investigate the relationship between physicochemical properties and the GFA of spray-dried solids and their long-term physical stability. The spray-dried solids were exposed to dry (<5% RH) and humid (75% RH) conditions for six months at 25 °C. The crystallization of the spray-dried solids under these conditions was monitored using a combination of solid-state characterization techniques including differential scanning calorimetry, Raman spectroscopy, and powder X-ray diffraction. The GFA/GS class assignment for 85% of the model compounds was method-dependent, with significant differences between spray-drying and melt-quenching methods. The long-term physical stability under dry condition of the compounds was predictable from GFA/GS classification and glass transition and crystallization temperatures. However, the stability upon storage at 75% RH could not be predicted from the same data. There was no strong correlation between the physicochemical properties explored and the GFA class or long-term physical stability. However, there was a slight tendency for compounds with a relatively larger molecular weight, higher glass transition temperature, higher crystallization temperature, higher melting point and higher reduced glass transition temperature to have better GFA and better physical stability. In contrast, a high heat of fusion and entropy of fusion seemed to have a negative impact on the GFA and physical stability of our dataset.

Glass-forming ability of Pr–(Cu,Ni)–Al alloys in eutectic system

2003 ◽  
Vol 18 (3) ◽  
pp. 664-671 ◽  
Author(s):  
Y. Zhang ◽  
H. Tan ◽  
H. Z. Kong ◽  
B. Yao ◽  
Y. Li
Keyword(s):  
Glass Transition ◽  
Transition Temperature ◽  
Glass Transition Temperature ◽  
Eutectic Composition ◽  
Solidus Temperature ◽  
Eutectic Point ◽  
Glass Forming Ability ◽  
Al Alloys ◽  
Eutectic System ◽  
Glass Forming

A eutectic point in Pr-rich Pr-(Cu,Ni)-Al alloys was experimentally determined by measuring the solidus temperature (Tm) and liquidus temperature (T1). It was found that Pr68(Cu0.5Ni0.5)25Al7 (at.%) is at the eutectic composition in the pseudoternary Pr–(Cu0.5Ni0.5)–Al alloys. The alloy Pr68(Cu0.5Ni0.5)25Al7 exhibits better glass-forming ability (GFA) than the ternary eutectic alloy Pr68Cu25Al7. However, the best GFA was obtained at an off-eutectic composition (Pr54[Cu0.5Ni0.5]30Al16) in the Pr–(Cu0.5Ni0.5)–Al alloys, which can be formed in fully amorphous rods with diameter of 1.5 mm by copper mold casting. Moreover, the glass-transition temperature Tg increases quickly (from 367 to 522 K) with the increasing of the Al content (from 3 to 27 at.%). The deviation of the best GFA composition from the eutectic point [Pr68(Cu0.5Ni0.5)25Al7] was explained in terms of the asymmetric coupled eutectic zone, the competition between growth of crystalline phase and formation of amorphous, and the higher glass-transition temperature Tg on the hypereutectic side.

DSC, ESR AND IR SPECTRAL STUDIES ON Li2O–WO3–B2O3 GLASS SYSTEM DOPED WITH VANADIUM IONS

2009 ◽  
Vol 02 (03) ◽  
pp. 127-130 ◽  
Author(s):  
LINGANABOINA SRINIVASA RAO ◽  
TUMU VENKATAPPA RAO
Keyword(s):  
Glass Transition ◽  
Local Structure ◽  
Glass Matrix ◽  
Glass Forming Ability ◽  
Glass System ◽  
Spectral Studies ◽  
Glass Forming ◽  
System A ◽  
Vanadium Ions ◽  
B2o3 Glass

With in glass forming region of Li2O–WO3–B2O3 glass system, a particular composition 40Li2O–5WO3–(55 –x) B2O3 : x V2O5 (with x ranging from 0.2 to 0.8, all are in mol.%) is chosen. The DSC traces are obtained to identify the glass transition temperature ( Tg ) and the glass forming ability of all the glass samples. The ESR and IR spectra portray the local structure of the glass system and valance states of the vanadium ions in the glass matrix. As the content of V2O5 increases up to 0.6 mol.% in the glass system, a gradual conversion of vanadium ions from V5+ state to V4+ state is observed, causing the depolymerization in the glass matrix by the transformation of several glass forming units BO4 → BO3 and WO4 → WO6 .

scholarly journals Elastic Properties and Glass Forming Ability of the Zr50Cu40Ag10 Metallic Alloy

2020 ◽  
Vol 310 ◽  
pp. 145-149 ◽  
Author(s):  
Ramil M. Khusnutdinoff ◽  
Anatolii V. Mokshin
Keyword(s):  
Glass Transition ◽  
Shear Modulus ◽  
Temperature Dependence ◽  
Elastic Properties ◽  
Metallic Glasses ◽  
Liquid Glass ◽  
Glass Forming Ability ◽  
Metallic Alloy ◽  
Poisson's Ratio ◽  
Glass Forming

The elastic properties of the Zr50Cu40Ag10 metallic alloy, such as the bulk modulus B, the shear modulus G, the Young’s modulus E and the Poisson’s ratio σ, are investigated by molecular dynamics simulation in the temperature range T=250–2000 K and at an external pressure of p=1.0 bar. It is shown that the liquid–glass transition is accompanied by a considerable increase in the shear modulus G and the Young’s modulus E (by more than 50%). The temperature dependence of the Poisson’s ratio exhibits a sharp fall from typical values for metals of approximately 0.32–0.33 to low values (close to zero), which are characteristic for brittle bulk metallic glasses. Non-monotonic temperature dependence of the longitudinal and transverse sound velocity near the liquid-glass transition is also observed. The glass forming ability of the alloy is evaluated in terms of the fragility index m. Its value is m≈64 for the Zr50Cu40Ag10 metallic glass, which is in a good agreement with the experimental data for the Zr-based metallic glasses.

Effect of K2O/ZnO+CaO Ratio on Density, Glass Forming Ability, Crystallization of SiO2- Al2O3- ZnO- K2O- CaO Frites

2021 ◽  
Author(s):  
aida faghinia ◽  
R. Salami ◽  
Z. Khakpour ◽  
M. Zakeri
Keyword(s):  
Glass Transition ◽  
Mole Fraction ◽  
Raw Materials ◽  
Glass Forming Ability ◽  
Powder Size ◽  
Molar Volumes ◽  
Glass Stability ◽  
Glass Forming ◽  
Zno Powder ◽  
Hardness Values

Abstract The frites by mole fraction of 2.5 SiO2, 0.20 Al2O3, 0.15 B2O3, 0.15ZnO, 0.17K2O, 0.67CaO systems in three ratios of S including 0.37(denoted by F1frites ),0.31(F2), 0.24(F3) (S=K2O/CaO+ZnO) were studied. ZnO powder with 500 nm (N series) and >1μm sizes (F series) opted from the recycled Zn ingots dusts and commercially ZnO respectively, were used as the raw materials. By decreasing the S ratio, the Molar Volumes of frites were decreased, The glass transition ΔTg(=-154ºC), and the crystallization temperatures ΔTp (=+17ºC) values were decreased and increased respectively. It was shown that the GS (glass stability) values are independent of the Zinc Oxide's powder size, while the Molar Volumes of N series were lower than the F ones. The Zinc Silicate (Willemite) beside Anorthite and Parawollastonite phases were crystallized in the resulted glazes. The hardness values were in 700-850 Hv range, the transparency and whiteness were higher than 80 and 60 respectively.

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