Rheology of Glass-Forming Melts

Gutzow, I.; Schmelzer, Jürn W. P.

doi:10.1007/978-3-642-34633-0_12

Cited by 16 publications

(126 citation statements)

References 34 publications

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“…That is, the number of crystals per volume [but determined per area, which can be transformed to volume terms according to DeHoff and Aigeltinger ( 1970 ) and Toschev and Gutzow ( 1967 )] decreases as a function of time, while the diameter and length of the crystals grow. Therefore, fundamentals of the theory of Ostwald ripening [reported by Slezov ( 2009 ) and Gutzow and Schmelzer ( 2013 )] are fulfilled: The thermodynamically driving force of the process is the reduction of the surface of the crystals by reducing the number of crystals and growing of larger ones. During this process, the total amount of the new phase remains constant but the Gibbs free energy decreases.…”

Section: Discussionmentioning

confidence: 99%

Radiopaque Strontium Fluoroapatite Glass-Ceramics

Höland

Schweiger

Dittmer

et al. 2015

Front. Bioeng. Biotechnol.

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The controlled precipitation of strontium fluoroapatite crystals was studied in four base glass compositions derived from the SiO2–Al2O3–Y2O3–SrO–Na2O–K2O/Rb2O/Cs2O–P2O5–F system. The crystal phase formation of these glasses and the main properties of the glass-ceramics, such as thermal and optical properties and radiopacity were compared with a fifth, a reference glass-ceramic. The reference glass-ceramic was characterized as Ca-fluoroapatite glass-ceramic. The four strontium fluoroapatite glass-ceramics showed the following crystal phases: (a) Sr5(PO4)3F – leucite, KAlSi2O6, (b) Sr5(PO4)3F – leucite, KAlSi2O6, and nano-sized NaSrPO4, (c) Sr5(PO4)3F – pollucite, CsAlSi2O6, and nano-sized NaSrPO4, and (d) Sr5(PO4)3F – Rb-leucite, RbAlSi2O6, and nano-sized NaSrPO4. The proof of crystal phase formation was possible by X-ray diffraction. The microstructures, which were studied using scanning electron microscopy, demonstrated a uniform distribution of the crystals in the glass matrix. The Sr-fluoroapatites were precipitated based on an internal crystallization process, and the crystals demonstrated a needle-like morphology. The study of the crystal growth of needle-like Sr-fluoroapatites gave a clear evidence of an Ostwald ripening mechanism. The formation of leucite, pollucite, and Rb-leucite was based on a surface crystallization mechanism. Therefore, a twofold crystallization mechanism was successfully applied to develop these types of glass-ceramics. The main focus of this study was the controlled development of glass-ceramics exhibiting high radiopacity in comparison to the reference glass-ceramic. This goal could be achieved with all four glass-ceramics with the preferred development of the Sr-fluoroapatite – pollucite-type glass-ceramic. In addition to this main development, it was possible to control the thermal properties. Especially the Rb-leucite containing glass-ceramic showed the highest coefficient of thermal expansion (CTE). These glass-ceramics allow optical properties, especially the translucency and color, to be tailored to the needs of biomaterials for dental applications. The authors conclude that it is possible to use twofold crystallization processes to develop glass-ceramic biomaterials featuring different properties, such as specific radiopacity values, CTEs, and optical characteristics.

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Section: Discussionmentioning

confidence: 99%

Radiopaque Strontium Fluoroapatite Glass-Ceramics

Höland

Schweiger

Dittmer

et al. 2015

Front. Bioeng. Biotechnol.

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“…Instead, the molecules reach a state where they are randomly oriented, like in a liquid, but where movement is halted. The temperature at which this occurs is called the glass transition temperature (T g ) . In most cases, very fast cooling rates are necessary to reach the glassy state.…”

Section: Introductionmentioning

confidence: 99%

Revisiting the Optimal Nano‐Morphology: Towards Amorphous Organic Photovoltaics

Nunzi

Lebel

2018

The Chemical Record

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Organic photovoltaic cells commonly use an active layer with a polycrystalline bulk heterojunction. However, for simplifying the fabrication process, it may be worthwhile to use an amorphous active layer to lessen the burden on processing to achieve optimal performance. While polymers can adopt amorphous phases, molecular glasses, small molecules that can readily form glassy phases and do not crystallize over time, offer an appealing alternative, being monodisperse species. Our group has developed a series of reactive molecular glasses that can be covalently bonded to chromophores to form glass‐forming adducts, and this strategy has been used to synthesize glass‐forming donor and acceptor materials. Herein, the results of devices incorporating these materials in either partially or fully amorphous active layers are summarized. Additionally, these molecular glasses can be used as ternary components in crystalline systems to enhance efficiency without perturbing the morphology.

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“…The theory of a vitreous state inevitably includes the nucleation phenomena [1]. Every vistreous medium contains the embryos of a crystal phase which are growing extremely slowly.…”

Section: Introductionmentioning

confidence: 99%

Theoretical Description of the Glass Preparation with the Necessary Optical Properties

Kurasov

2016

Advances in Optical Technologies

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The method to get the glass media with necessary optical characteristics is proposed. This method is based on inserting a necessary number of heterogeneous centers of given activity into the system. The theoretical description of the nucleation process in such situation is given and the resulting formulas allow choosing the characteristics of heterogeneous centers necessary to get the required optical characteristics of the media.

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Rheology of Glass-Forming Melts

Cited by 16 publications

References 34 publications

Radiopaque Strontium Fluoroapatite Glass-Ceramics

Radiopaque Strontium Fluoroapatite Glass-Ceramics

Revisiting the Optimal Nano‐Morphology: Towards Amorphous Organic Photovoltaics

Theoretical Description of the Glass Preparation with the Necessary Optical Properties

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