Viscosity of Metallic Glass Forming Liquids: Analysis Based on Bond Strength-Coordination Number Fluctuations

2010 ◽  
Vol 638-642 ◽  
pp. 1621-1626 ◽  
Author(s):  
Masaru Aniya ◽  
Masahiro Ikeda
Keyword(s):  
Metallic Glass ◽  
Bond Strength ◽  
Viscous Flow ◽  
Coordination Number ◽  
Structural Units ◽  
Mean Values ◽  
Glass Forming ◽  
The Mean

A model that describes the viscous behavior in terms of the mean values of the bond strength, the coordination number, and their fluctuations of the structural units that form the melt has been proposed by one of the authors. In the present study, the viscous behavior of several metallic glass forming systems are analyzed by using the model. From the analysis, microscopic information such as the number of bonds that must be broken to observe the viscous flow is obtained. It is also shown that when the magnitudes of energy and coordination number fluctuations are equal, the behavior of the viscosity described by our model corresponds perfectly to the behavior described by the Vogel-Fulcher-Tammann (VFT) equation.

Analysis of Cooperativity in Metallic Glass Forming Liquids

2014 ◽  
Vol 783-786 ◽  
pp. 1889-1894 ◽  
Author(s):  
Masaru Aniya ◽  
Masahiro Ikeda
Keyword(s):  
Metallic Glass ◽  
Bond Strength ◽  
Temperature Dependence ◽  
Coordination Number ◽  
Atomic Motion ◽  
Structural Units ◽  
Mean Values ◽  
Glass Forming ◽  
The Mean ◽  
Fluctuation Model

The relation between fragility and cooperativity of atomic motion in bulk metallic glass forming liquids is studied based on the bond strength-coordination number fluctuation model. The model describes the temperature dependence of the viscosity in terms of the mean values of the bond strength, coordination number and their fluctuations of the structural units that form the melt. According to the model, the cooperativity increases with the increase of fragility. The model estimates that the magnitude of the cooperativityNBextends approximately from 7 to 60 structural units, depending on the material. The temperature dependence ofNBfor different metallic glass forming systems reveals thatNBincreases with the decrease of temperature. The relation betweenNBand diffusivity of atoms is discussed briefly.

Fractional Exponent of the Modified Stokes-Einstein Relation in the Metallic Glass-Forming Melt Pd43Cu27Ni10P20

2010 ◽  
Vol 146-147 ◽  
pp. 1463-1468
Author(s):  
Masahiro Ikeda ◽  
Masaru Aniya
Keyword(s):  
Diffusion Coefficient ◽  
Glass Transition ◽  
Transition Temperature ◽  
Glass Transition Temperature ◽  
Metallic Glass ◽  
Bond Strength ◽  
Coordination Number ◽  
Einstein Relation ◽  
Glass Forming ◽  
Highly Correlated

The diffusion coefficient in the metallic glass-forming systems such as Pd-Cu-Ni-P exhibits a marked deviation from the Stokes-Einstein (SE) relation in the proximity of the glass transition temperature. Such a deviation is characterized by the fractional exponent p of the modified SE expression. For the material Pd43Cu27Ni10P20, it has been reported that it takes the value p = 0.75. In this work, it is shown that the value of p is highly correlated with the ratio ED / ENB, where ED and ENB are the activation energies for diffusion coefficient D and cooperativity NB defined by the Bond Strength-Coordination Number Fluctuation (BSCNF) model. The present paper reports that for the metallic glass-forming melt Pd43Cu27Ni10P20, the fractional exponent p can be calculated accurately within the framework of the BSCNF model.

A Comparative Study of Molecular Motion Cooperativity in Polymeric and Metallic Glass-Forming Liquids

2016 ◽  
Vol 879 ◽  
pp. 151-156 ◽  
Author(s):  
Masaru Aniya ◽  
Masahiro Ikeda ◽  
Sahara
Keyword(s):  
Metallic Glass ◽  
Bond Strength ◽  
Comparative Study ◽  
Coordination Number ◽  
Molecular Motion ◽  
Fragility Index ◽  
Glass Forming ◽  
Cooperative Relaxation ◽  
The Difference ◽  
The Relationship

In order to investigate the relationship between the bonding nature and the cooperative relaxation, a comparative study of the relaxation behavior in polymeric and metallic glass forming systems has been performed based on the Bond Strength–Coordination Number Fluctuation (BSCNF) model developed by the authors. In the present work, we studied the correlations between the fragility m, the Vogel temperature T0, the degree of molecular cooperativity NB, and the Kohlrausch exponent βKWW. The results show that T0 and NB increase, whereas βKWW decreases systematically with the increase of m. Reflecting the difference of the interatomic interactions of the materials considered, the analysis by the present study reveals that the value of NB in ion-conducing polymers is about 5 times larger than that in metallic systems, and for each system, the material dependence of βKWW is clearly seen in the fragility index m and the cooperativity NB.

Evaluation of a Characteristic Temperature in the Relaxation of Metallic Glass Forming Liquids

2018 ◽  
Vol 941 ◽  
pp. 2331-2336 ◽  
Author(s):  
Masaru Aniya ◽  
Masahiro Ikeda
Keyword(s):  
High Temperature ◽  
Melting Point ◽  
Metallic Glass ◽  
Bond Strength ◽  
Temperature Dependence ◽  
Coordination Number ◽  
Structural Relaxation ◽  
Characteristic Temperature ◽  
Glass Forming ◽  
Metallic Liquids

The high-temperature viscosity of metallic glass-forming liquids is investigated by using the Bond Strength-Coordination Number Fluctuation (BSCNF) model developed by the authors. For many glass-forming liquids, a salient change in the structural relaxation is observed above the melting point. The temperature dependence of the structural relaxation exhibits a deviation from an Arrhenius-like behavior, and upon cooling it transforms to a non-Arrhenius-like one. In the present study, we show that the BSCNF model describes well the high-temperature viscosity behaviors of metallic liquids. The analysis based on the BSCNF model also enables to extract a characteristic temperature at high temperature. The results of the present study show that such characteristic temperature can be a good indicator for the evaluation of the range of the transition from the Arrhenius-like to the non-Arrhenius-like relaxation behavior.

Controlled Elasticity in Nano-Structured Metallic Glass by Ion Implantation Method

2007 ◽  
Vol 561-565 ◽  
pp. 1315-1318
Author(s):  
Shinji Muraishi ◽  
Hirono Naito ◽  
Jhi Shi ◽  
Yoshio Nakamura ◽  
Tatsuhiko Aizawa
Keyword(s):  
Metallic Glass ◽  
Glassy Phase ◽  
Glassy Matrix ◽  
Nano Structure ◽  
Glass Forming ◽  
Nitride Formation ◽  
Indentation Tests ◽  
The Mean ◽  
Implantation Method ◽  
Critical N Concentration

Different reactivity of ions has been implanted into Zr-Cu metallic glass to obtain nano-structured surface with controlled elasticity. The penetration of glass forming element of Ni+ into crystalline Zr-Cu stabilizes glassy phase to induce crystalline-amorphous (c-a) transition during implantation process. In the meanwhile, penetration of N+ into glassy matrix induces precipitation of (Zr, Cu)N at the mean penetration depth of N. Critical N concentration for nitride formation is estimated to be (Zr,Cu)-20at%N, which also suggests existing of N solid solution of glassy phase. Inert element of Ar+ yields dispersion of nano-voids among glassy matrix. Nano-indentation tests reveal that Young’s modulus of ion implanted glassy film dramatically changes with respect to the induced nano-structure, to decrease 0.4 times for Ar+, to increase 1.3 times for N+ as comparison with that for as-deposited state.

scholarly journals Influence of Silver Nanoparticles on the Specific Properties of Acrylic Resin for Ocular Prosthesis

2018 ◽  
Vol 11 (3) ◽  
pp. 1573-1581 ◽  
Author(s):  
Maha M. Turki ◽  
Faiza M. Abdul-Ameer
Keyword(s):  
Surface Roughness ◽  
Impact Strength ◽  
Flexural Strength ◽  
Bond Strength ◽  
Shear Bond Strength ◽  
Acrylic Resin ◽  
Control Group ◽  
Mean Values ◽  
The Mean ◽  
Group B

Scleral acrylic resin is widely used to synthesize ocular prosthesis. However, the properties of this material change over time, thus requiring the prosthesis to be refabricated. Many studies were conducted to improve these properties by reinforcing this material with nanoparticles. This study aims to evaluate the effect of silver nanoparticle powder on the mechanical properties (transverse flexural strength, impact strength, shear bond strength, surface microhardness, and surface roughness) of scleral acrylic resin used for ocular prostheses. Two concentrations were selected from the pilot study and evaluated for their effects on scleral acrylic resin properties. According to the pilot study, 0.01 and 0.02wt% AgNPs powder improved the transverse flexural strength, microhardness, and surface roughness compared with other percentages. The specimens in the main study were divided into (3) main groups, (50) specimens without additives (control group A), (50) experimental specimens (with 0.01wt% AgNPs group B), and (50) experimental specimens (with 0.02 wt% AgNPs group C). Each group was subdivided into (5) equal subgroups depending on the tests used. The data were studied using one way ANOVA and post hoc LSD test. At 0.01 wt% AgNPs addition, the mean values of transverse flexural strength insignificantly increased (p> 0.05), and those of impact strength and shear bond strength significantly increased (p< 0.05) compared with those of the control group. At 0.02 wt% AgNPs addition (group C), the mean value of transverse flexural strength significantly increased (p< 0.05), that of impact strength insignificantly increased (p> 0.05), and that of shear bond strength increased with high significance (p< 0.01) compared with those of the control group. Group C showed insignificant increase in the mean values of transverse flexural strength, impact strength, and shear bond strength (p. 0.05) compared with group B. The scleral acrylic resin added with 0.01 and 0.02 wt% AgNPs showed insignificant increase in microhardness and insignificant decrease in surface roughness. The addition of AgNPs powder in both concentrations improved the mechanical properties of scleral acrylic resin used for ocular prostheses.

scholarly journals Viscous Flow of Supercooled Liquid in a Zr-Based Bulk Metallic Glass Synthesized by Additive Manufacturing

Materials ◽  
2020 ◽  
Vol 13 (17) ◽  
pp. 3803
Author(s):  
Konrad Kosiba ◽  
Liang Deng ◽  
Sergio Scudino
Keyword(s):  
Additive Manufacturing ◽  
Metallic Glass ◽  
Viscous Flow ◽  
Supercooled Liquid ◽  
Viscous Liquids ◽  
Powder Bed ◽  
Glass Forming ◽  
Size Limitation ◽  
Structural Applications ◽  
Thermoplastic Forming

The constraint in sample size imposed by the critical cooling rate necessary for glass formation using conventional casting techniques is possibly the most critical limitation for the extensive use of bulk metallic glasses (BMGs) in structural applications. This drawback has been recently overcome by processing glass-forming systems via additive manufacturing, finally enabling the synthesis of BMGs with no size limitation. Although processing by additive manufacturing allows fabricating BMG objects with virtually no shape limitation, thermoplastic forming of additively manufactured BMGs may be necessary for materials optimization. Thermoplastic forming of BMGs is carried out above the glass transition temperature, where these materials behave as highly viscous liquids; the analysis of the viscosity is thus of primary importance. In this work, the temperature dependence of viscosity of the Zr52.5Cu17.9Ni14.6Al10Ti5 metallic glass fabricated by casting and laser powder bed fusion (LPBF) is investigated. We observed minor differences in the viscous flow of the specimens fabricated by the different techniques that can be ascribed to the higher porosity of the LPBF metallic glass. Nevertheless, the present results reveal a similar overall variation of viscosity in the cast and LPBF materials, which offers the opportunity to shape additively manufactured BMGs using already developed thermoplastic forming techniques.

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