Viscosity measurement by thermomechanical analyzer

Košťál, Petr; Hofírek, Tomáš; Málek, Jiřı́

doi:10.1016/j.jnoncrysol.2017.05.027

Cited by 15 publications

(10 citation statements)

References 31 publications

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“…TMA instruments were used for the study of material viscosity utilizing two experimental methods: the penetration method and the parallel‐plate method. Both methods and the calibration procedure are described in detail in our previous work 33 . Here, only the fundamentals of measurements and experimental setups are mentioned.…”

Section: Methodsmentioning

confidence: 99%

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Viscosity and heat capacity of As₂Se₃ connected via Adam–Gibbs model

Koštál,

Včeláková,

Málek

2023

J Am Ceram Soc.

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The viscosity data measured by penetration and parallel‐plate methods for As2Se3 glass and undercooled melt were compared with literature data. The MYEGA equation (log η0 = −4.67 ± 0.12, m = 43.2 ± 0.4, and T12 = 441.7 ± 0.3 K) was used for the description of the selected viscosity data, including melt region (15 orders of magnitude). The heat capacity data for As2Se3 glass, undercooled melt, and melt, as well as for crystalline As2Se3 were determined for low and medium‐range temperature intervals. These data were compared with previously reported data. Equations that describe the heat capacity of As2Se3 in a broad temperature interval were formulated. The values of the standard molar enthalpy, Δ0THm0, and entropy, Δ0TSm0, at T = 298.15 K are 26.202 kJ·mol−1 and 193.8 J·mol−1·K−1, respectively. The heat capacity data determined from very low temperatures were used for the calculation of crystal, glass, and melt entropies. These heat capacity temperature dependencies were used both for the estimation of the Kauzmann temperature (TK = 292.5 K) and the glass entropy at 0 K (S0 = 25.96 J·mol−1·K−1), and for the determination of the excess entropy. The proportionality between the viscosity of the As2Se3 melt and the excess entropy clearly indicates the applicability of the Adam–Gibbs (AG) model.

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Section: Methodsmentioning

confidence: 99%

“…The accuracy determined by the NBS 711 standard is about ± 0.05 log units. A more detailed description of the precision and accuracy of viscosity measurements is provided in our previous work 33 . The described methods for viscosity determination are also appropriate for measuring different materials.…”

Section: Methodsmentioning

confidence: 99%

Viscosity and heat capacity of As₂Se₃ connected via Adam–Gibbs model

Koštál,

Včeláková,

Málek

2023

J Am Ceram Soc.

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“…The temperature was calibrated on melting points of pure metals (Ga, In, Sn, Pb, Zn, Al). More details about the instrument, calibration, methodology, experimental arrangement and errors can be found in the work of Koštál et al [34]. Direct measurements of crystal growth were performed by an optical microscope (Olympus BX51 equipped with camera DP72 and infrared camera XM10; in the reflection mode).…”

Section: Methodsmentioning

confidence: 99%

Analysis of crystal growth and viscosity in Ge-Sb-Se-Te undercooled melts

Barták

Košťál

Málek

2019

Journal of Non-Crystalline Solids

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A comprehensive analysis on crystal growth and viscosity is presented for the Ge2Sb2Se5-xTex (x = 0.5 and 1) undercooled melts in this article. Temperature dependence of the measured viscosities (10 7.5 -10 12.5 Pa•s) can be described by a simple exponential Arrhenius type equation in the relatively narrow temperature region in which the measurements were performed. Fragility of the measured materials are all roughly equal to 43, which means that these materials belong to the so called "intermediate" liquids (lying in the middle between strong and fragile liquids) and cannot be described by simple Arrhenius type equation if the temperature region is expanded from glass transition to melting, which is important for description of crystal growth. Therefore, MYEGA equation is used to extrapolate the viscosity data into the temperature region of studied crystal growth. Nucleation and crystal growth started on a surface of studied samples. The isothermal growth rate of the formed surface crystalline layer was measured at various temperatures. Analysis of the growth data revealed a crystal growth driven by liquid-crystal interface kinetics. Therefore, the standard crystal growth models were used for description of crystal growth rates in the studied systems.

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“…Among others, in viscosity values ranging 10 5 –10 12 Pa s, parallel plate, penetration, fiber elongation, or beam bending methods are used. Stokes’ falling sphere/bubble rise methods are usually used at a low viscosity of <10 4 Pa s. At viscosity values <10 6 Pa s, the rotating concentric cylinders technique is the standard [ 6 , 7 ]. Several models can be used to obtain theoretical viscosity values as a function of composition and temperature.…”

Section: Introductionmentioning

confidence: 99%

Assigning Viscosity Values in the Glass Softening Temperature Range

Prado

Benedetto

2023

Materials

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A new optical method for assigning glass viscosity values in the softening temperature range is presented. In this method, an irregular particle, a few millimeters in size, laying on an alumina plate, is heated up to temperature T, and then remains at this temperature. T should be within the softening temperature range of the glass. There are no external applied shear stresses, the only acting shear forces are those coming from the particle’s own surface energy. At the fixed temperature T, the surface free energy of the sample decreases by viscous flow while its shape evolves from a polyhedron or irregular shape towards a spherical or rounded shape. This shape evolution is recorded using a photographic camera. From each image, the sample’s roundness is determined, obtaining a characteristic time τ from the roundness against time. Simultaneously, using the available software, a value for the viscosity η was calculated, at temperature T, allowing for building sets of T, τ, η, namely three data values. Accordingly, if T, τ are considered as independent variables, a master function η = η (T, τ) can be built. Now, if we measure T, τ data on a glass of an unknown viscosity, the master function makes it possible to assign a η value. When incipient crystallization or liquid–liquid phase separations are present, effective viscosity values are obtained. This method requires a high temperature microscope, as well as tridimmensional samples with a few cubic millimeters of volume. Each isothermal τ determination can take from minutes to several hours. We tested the method with two glasses of known viscosity values: borosilicate glass (VG98) and alumimoborosilicate glass (SG7), both of which are used for radioactive waste immobilization and have assigned log(η) values between 6 and 7.3 with η in Pa s. The discrepancy between the log(η) values assigned here and those values fitted with a VFT function on the values measured for the SG7 and VG98 glasses were within ±14%.

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Viscosity measurement by thermomechanical analyzer

Cited by 15 publications

References 31 publications

Viscosity and heat capacity of As₂Se₃ connected via Adam–Gibbs model

Viscosity and heat capacity of As₂Se₃ connected via Adam–Gibbs model

Analysis of crystal growth and viscosity in Ge-Sb-Se-Te undercooled melts

Assigning Viscosity Values in the Glass Softening Temperature Range

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Viscosity measurement by thermomechanical analyzer

Cited by 15 publications

References 31 publications

Viscosity and heat capacity of As2Se3 connected via Adam–Gibbs model

Viscosity and heat capacity of As2Se3 connected via Adam–Gibbs model

Analysis of crystal growth and viscosity in Ge-Sb-Se-Te undercooled melts

Assigning Viscosity Values in the Glass Softening Temperature Range

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Product

Resources

About

Viscosity and heat capacity of As₂Se₃ connected via Adam–Gibbs model

Viscosity and heat capacity of As₂Se₃ connected via Adam–Gibbs model