Thermodynamics of Te80Ge20 − x Pbx glass-forming alloys

1988 ◽  
Vol 3 (3) ◽  
pp. 570-575 ◽  
Author(s):  
L. Battezzati ◽  
A. L. Greer
Keyword(s):  
Free Energy ◽  
Specific Heat ◽  
Glass Forming Ability ◽  
Undercooled Liquid ◽  
Scanning Calorimetry ◽  
Entropy Of Fusion ◽  
Glass Forming ◽  
Crystal Phases ◽  
Solid Phases ◽  
Liquid And Solid Phases

The specific heat of liquid and solid phases and the heats of crystallization and fusion have been measured by differential scanning calorimetry (DSC) for a series of Te80Ge20 − x Pbx alloys (0≤x≤20). The enthalpy, entropy, and free energy of the undercooled liquid are quantitatively assessed with reference to the crystal phases. The available formulas for computing the free energy of the liquid are compared, and their relative merits are discussed. The glass transition temperature is shown to depend strongly on the ratio of the average excess specific heat of the liquid to the entropy of fusion. An anomaly in the liquid specific heat, which is particularly important for Te80Ge20 and Te80Ge15Pb5, leads to very good glass forming ability for these alloys; this is demonstrated by preparing amorphous samples by means of fluxing.

Thermodynamics of The Pd43Ni10Cu27P20 Bulk Metallic Glass Forming Alloy

2003 ◽  
Vol 806 ◽  
Author(s):  
Masahiro Kuno ◽  
Ludi A. Shadowspeaker ◽  
Jan Schroers ◽  
Ralf Busch
Keyword(s):  
Heat Capacity ◽  
Free Energy ◽  
Metallic Glass ◽  
Specific Heat ◽  
Bulk Metallic Glass ◽  
Gibbs Free Energy ◽  
Specific Heat Capacity ◽  
Undercooled Liquid ◽  
Glass Forming ◽  
Crystalline Mixture

ABSTRACTThe thermodynamics of the bulk metallic glass forming Pd43Ni10Cu27P20 alloy were investigated with differential scanning calorimetry (DSC). The specific heat capacity of the undercooled liquid with respect to the crystalline mixture was measured in the DSC simultaneously with the enthalpy of crystallization over the entire supercooled liquid region. The enthalpy, entropy, and Gibbs free energy change between the liquid and the crystalline mixture was determined from the specific heat capacity data. The calculated enthalpy function closely matched the enthalpies of crystallization that were measured in the DSC, which verifies the validity of the thermodynamic model used. A small Gibbs free energy difference between undercooled liquid and crystalline mixture was found for decreasing temperature in Pd43Ni10Cu27P20 when compared to other glass forming alloys. This reflects a small driving force for crystallization when undercooling this alloy and is the main contributing factor for its high glass forming ability.

scholarly journals Interfacial Free Energy Controlling Glass-Forming Ability of Cu-Zr Alloys

2014 ◽  
Vol 4 (1) ◽  
Author(s):  
Dong-Hee Kang ◽  
Hao Zhang ◽  
Hanbyeol Yoo ◽  
Hyun Hwi Lee ◽  
Sooheyong Lee ◽  
...  
Keyword(s):  
Free Energy ◽  
Interfacial Free Energy ◽  
Glass Forming Ability ◽  
Glass Forming ◽  
Zr Alloys

scholarly journals Myth or Truth: The Glass Forming Ability Class III Drugs Will Always Form Single-Phase Homogenous Amorphous Solid Dispersion Formulations

Pharmaceutics ◽  
2019 ◽  
Vol 11 (10) ◽  
pp. 529 ◽  
Author(s):  
Piyush Panini ◽  
Massimiliano Rampazzo ◽  
Abhishek Singh ◽  
Filip Vanhoutte ◽  
Guy Van den Mooter
Keyword(s):  
Single Phase ◽  
Solid Dispersions ◽  
Amorphous Solid ◽  
Glass Forming Ability ◽  
Amorphous Solid Dispersion ◽  
Class Iii ◽  
Scanning Calorimetry ◽  
Amorphous Solid Dispersions ◽  
Modulated Differential Scanning Calorimetry ◽  
Glass Forming

The physical stability of amorphous solid dispersions (ASD) of active pharmaceutical ingredients (APIs) of high glass forming ability (GFA class III) is generally expected to be high among the scientific community. In this study, the ASD of ten-selected class III APIs with the two polymers, PVPVA 64 and HPMC-E5, have been prepared by spray-drying, film-casting, and their amorphicity at T0 was investigated by modulated differential scanning calorimetry and powder X-ray diffraction. It was witnessed that only five out of ten APIs form good quality amorphous solid dispersions with no phase separation and zero crystalline content, immediately after the preparation and drying process. Hence, it was further established that the classification of an API as GFA class III does not guarantee the formulation of single phase amorphous solid dispersions.

Glass Forming Ability of Ca-Based Bulk Metallic Glasses

2011 ◽  
Vol 171 ◽  
pp. 121-126 ◽  
Author(s):  
Ashmi T. Patel ◽  
Kirit N. Lad ◽  
Arun Pratap
Keyword(s):  
Metallic Glasses ◽  
Driving Force ◽  
Bulk Metallic Glasses ◽  
Energy Difference ◽  
Glass Forming Ability ◽  
Point Of View ◽  
Undercooled Liquid ◽  
Free Energy Difference ◽  
Glass Forming ◽  
Gibbs Free Energy Difference

Knowledge of glass forming ability (GFA) of amorphous metallic alloys is very important from both theoretical and practical point of view. Thermodynamically, the Gibbs free energy difference, ΔG between the undercooled liquid and the corresponding crystalline state is driving force for crystallization. As a consequence, it is a good indicator for glass forming ability of metallic glasses. A novel expression for ΔG has been used to estimate the GFA of recently developed Ca-based bulk metallic glasses viz. Ca53Mg23Cu24,Ca65Mg15Cu20,Ca40Mg25Cu35, Ca50Mg22.5Cu27.5 and Ca55Mg15Cu30. Different GFA criteria are also evaluated for systems taken up in the study and effect of addition of variation in composition of Ca-Mg-Cu system is also investigated. Present work suggests that among different GFA criteria, ΔG is the best criterion for the prediction of GFA for Ca-based bulk metallic glasses.

Gibbs free energy for the crystallization of metallic glass-forming alloys from an undercooled liquid

2008 ◽  
Vol 88 (4) ◽  
pp. 239-249 ◽  
Author(s):  
H. Dhurandhar ◽  
T. L. Shanker Rao ◽  
K. N. Lad ◽  
A. Pratap
Keyword(s):  
Free Energy ◽  
Metallic Glass ◽  
Gibbs Free Energy ◽  
Undercooled Liquid ◽  
Glass Forming

Glass Forming Ability and Crystallization Kinetics of Al-Mg-Ni-La Metallic Glasses

2014 ◽  
Vol 960-961 ◽  
pp. 161-164 ◽  
Author(s):  
Juan Mu ◽  
Hai Feng Zhang
Keyword(s):  
Crystallization Kinetics ◽  
Glass Forming Ability ◽  
Continuous Heating ◽  
X Ray Diffraction ◽  
Scanning Calorimetry ◽  
Glass Forming ◽  
Dsc Measurements ◽  
Mg Addition ◽  
Kinetics Of ◽  
Thermal Stability Of

Glass forming ability and crystallization kinetics of Al-Mg-Ni-La alloys have been investigated by X-ray diffraction (XRD) and differential scanning calorimetry (DSC). The maximum thickness achievable in glasses of Al76Mg11Ni8La5and Al69Mg18Ni8La5ribbons were 200 and 120 μm, respectively. The crystallization temperature and peak temperature indicated by DSC measurements displayed dependence on the heating rate during continuous heating, and were coincident with Lanoka’s relationship. The activation energies for the crystallization reactionExwere obtained from the Kissinger’s equation. The results show the Mg addition is beneficial to the thermal stability of the amorphous phase.

Effect of Co Addition on the Glass-Forming Ability and Mechanical Properties of Ti-Zr-Be-Cu-Co Bulk Amorphous Alloys

2012 ◽  
Vol 182-183 ◽  
pp. 203-207
Author(s):  
Zhong Yuan Suo ◽  
Yan Ling Song ◽  
Ke Qiang Qiu
Keyword(s):  
Mechanical Properties ◽  
Glassy Alloy ◽  
Glass Forming Ability ◽  
Yield Strain ◽  
Scanning Calorimetry ◽  
High Fracture ◽  
Glass Forming ◽  
Transmission Electron ◽  
Bulk Glassy Alloy ◽  
Co Addition

The effect of Co substitution for Be on the glass-forming ability and mechanical properties was investigated in Ti35Zr30Be27.5-xCu7.5Cox (x=0, 3.5, 7.5, 11.5 at.%) alloys by using X-ray diffractometry (XRD), differential scanning calorimetry (DSC), high-resolution transmission electron microscopy (HRTEM) and compression test. With the substitution of Co for Be, glass-forming ability (GFA) is significantly enhanced and fully amorphous rods with a diameter of up to 12 mm were produced in the alloy with 3.5 and 7.5 at.% Co. The Ti35Zr30Be24Cu7.5Co3.5 bulk glassy alloy exhibits good plasticity of 4% during compressive applied load at ambient temperature in conjunction with distinct yield strain of 2% and high fracture strength of 2196 MPa. The effect of the addition of Co on the structure and deformation behavior of the Ti35Zr30Be27.5-xCu7.5Cox (x=0, 3.5, 7.5, 11.5 at.%) alloys is discussed.

Glass-Forming Ability and Crystallization Kinetics of Hf-Ti-Cu-Ni-Al Bulk Metallic Glass

2012 ◽  
Vol 479-481 ◽  
pp. 1786-1789 ◽  
Author(s):  
Tie Jun Chen
Keyword(s):  
Thermal Stability ◽  
Crystallization Kinetics ◽  
Glass Formation ◽  
Glass Forming Ability ◽  
Ideal Condition ◽  
X Ray Diffraction ◽  
Scanning Calorimetry ◽  
Cross Sectional ◽  
Glass Forming

Multi-component Hf45.6Cu27.8Ni9.3Ti5Al12.4bulk metallic glasses (BMGs) were prepared successfully by casted into the water-cooled Cu mold. Characterization of the casted Hf45.6Cu27.8Ni9.3Ti5Al12.4rods was carried out by X-ray diffraction. The thermal stability and crystallization kinetics were followed by differential scanning calorimetry. The results show that the alloy Hf45.6Cu27.8Ni9.3Ti5Al12.4had a critical cylindrical rod diameter for glass formation, Dc, of 7 mm and the largest cross-sectional diameter (about 12.4mm) can be obtained in the ideal condition. The critical cooling rate for glass formation is 6.48K/s. The Hf45.6Cu27.8Ni9.3Ti5Al12.4BMG has larger glass forming ability and higher thermal stability.

Effect of Zr addition on the glass-forming ability and mechanical properties of Ni–Nb alloy

2007 ◽  
Vol 22 (2) ◽  
pp. 453-459 ◽  
Author(s):  
Z.W. Zhu ◽  
H.F. Zhang ◽  
W.S. Sun ◽  
Z.Q. Hu
Keyword(s):  
Mechanical Properties ◽  
Glass Forming Ability ◽  
Compression Tests ◽  
Casting Method ◽  
Scanning Calorimetry ◽  
Glass Forming ◽  
Zr Addition ◽  
Pattern Structures ◽  
Injection Casting ◽  
Zr Alloys

The effect of zirconium (Zr) addition on the glass-forming ability (GFA) and mechanical properties of the Ni61.5Nb38.5 alloy has been studied. The addition of Zr improves the GFA. When x = 5 for Ni61.5Nb38.5−xZrx (in at.%) alloys, the alloy exhibits the best GFA and can be cast into 3-mm-diameter amorphous samples by using the copper mold injection-casting method. Differential scanning calorimetry measurements indicated that the thermal parameters, such as Trg and γ, have not a good correlation with the GFA in the Ni–Nb–Zr alloys. Compression tests reveal that the addition of Zr just decreases the fracture strength slightly from 3.4 to 3 GPa and that all of the tested samples exhibit a little compressive plasticity of about 2%. When x = 9, the feature of the fracture surface indicates that the alloy has a tendency for transition from the ductile to the brittle. And delicate “dimple” and microscale vein pattern structures have been observed on it.

Crystal packing and crystallization tendency from the melt of 2-((2-ethylphenyl)amino)nicotinic acid

2018 ◽  
Vol 233 (1) ◽  
pp. 9-16 ◽  
Author(s):  
Arjun Kalra ◽  
Mingtao Zhang ◽  
Sean Parkin ◽  
Tonglei Li
Keyword(s):  
Nicotinic Acid ◽  
Crystal Packing ◽  
Amorphous State ◽  
Glass Forming Ability ◽  
Melt Quenching ◽  
Scanning Calorimetry ◽  
Glass Forming ◽  
Planar Conformation ◽  
Acid Acid ◽  
Crystallization Tendency

Abstract2-((2-ethylphenyl)amino)nicotinic acid (2EPNA) was synthesized and its crystal structure was determined. It was observed that alkylation of the phenyl ring with ethyl group disrupts the planar conformation of the molecule by steric repulsion, resulting in formation of an acid-pyridine heterosynthon (instead of acid-acid homosynthon) in the crystal. Crystallization tendency from the melt state of the polymorph was studied by differential scanning calorimetry (DSC). It was revealed that this compound could form a very stable amorphous phase on melt quenching and not crystallize even on re-heating. The formation of acid-pyridine hydrogen bonding in the amorphous state is believed to be responsible for its good glass forming ability.

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