Author
George H. Beall
Bio: George H. Beall is an academic researcher from Corning Inc.. The author has contributed to research in topics: Glass-ceramic & Ceramic. The author has an hindex of 30, co-authored 129 publications receiving 3297 citations.
Topics: Glass-ceramic, Ceramic, Crystal, Phase (matter), Crystallization
Papers published on a yearly basis
Papers
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TL;DR: In this article, two types of nanocrystalline glass-ceramics are studied: transparent glass and high-modulus glass with precisely engineered surfaces, and the key crystalline phases include β-quartz solid solutions, characterized by low-thermalexpansion behavior; spinel, with high hardness and elastic modulus; and mullite, which shows unique chromium-luminescence behavior.
Abstract: Future applications for glass-ceramics are likely to capitalize on designed-in, highly specialized properties for the transmission, display, and storage of information. Glass-ceramics with microstructures comprised of uniformly dispersed crystals <100 nm in size offer promise for many potential new applications as well as provide unique attributes for many current products. This paper focuses on two types of nanocrystalline glass-ceramics: transparent glass-ceramics and tough, high-modulus glass-ceramics with precisely engineered surfaces. Transparent glass-ceramics are formed from certain aluminosilicate glasses capable of efficient crystal nucleation and slow growth. The key crystalline phases include β-quartz solid solutions, characterized by low-thermal-expansion behavior; spinel, with high hardness and elastic modulus; and mullite, which shows unique chromium-luminescence behavior.
487 citations
TL;DR: In this article, the metastable binary two-liquid region is defined, and a structural interpretation of the phase separation and the effects of small oxide additions on it is offered, and evidence for both classical and possible spinodal nucleation mechanisms during liquid segregation in this system is presented.
Abstract: Metastable glass-in-glass separation was observed on rapid quenching of A12O3-SiO2 melts containing from 10 to 50 mol% A12O3. Nucleation and subsequent crystallization of mullite within the high-alumina-dispersed glass phase may occur either during cooling from the melt or on reheating. The metastable binary two-liquid region is compositionally defined, and a structural interpretation of the phase separation and the effects of small oxide additions on it is offered. Evidence for both classical and possible spinodal nucleation mechanisms during liquid segregation in this system is presented.
230 citations
TL;DR: In this paper, the relationships between composition, microstrcuture, and properties of glass-ceramics based on chain silicates are discussed, and potential applications are described.
Abstract: Glass-ceramics based on chain silicates: enstatite (MgSiO 3 ), potassium fluorrichterite (KNaCaMg 5 Si 8 O 22 F 2 ), and fluorcanasite (K 2 Na 4 Ca 5 Si 12 O 30 F 4 ), display a combination of high flexural strength ( > 200 MPa) and high fracture toughness (> 3 MPa rmm 1 2 ). The relationships between composition, microstrcuture, and properties are discussed. Recent and potential applications are described.
124 citations
TL;DR: In this article, the β-quartz structure can be crystallized from most glasses in the system SiO2-Mg(AlO2)2-LiAlO 2 as well as from many containing the additional components Zn(Al O2), Li2ZnO2, and Li2BeO2 and internal nucleation is afforded by adding ZrO2 or TiO2.
Abstract: Metastable solid solutions with the β-quartz structure can be crystallized from most glasses in the system SiO2-Mg(AlO2)2-LiAlO2 as well as from many containing the additional components Zn(AlO2)2 Al(AlO2)3, Li2ZnO2, and Li2BeO2. Internal nucleation is afforded by additions of ZrO2 or TiO2. Either transparent or opaque crystalline materials can be formed from glasses containing about 70% SiO2. The transparency is due to a combination of low birefringence in the major stuffed β-quartz phase and minute crystal size. Thermal expansions vary from -20 to +50 × 10−7/°C. Thermal stability is highly variable. Breakdown products include spinel, cordierite, β-spodumene, willemite, mullite, and cristobalite. Magnesian compositions can be strengthened by a 2Li+⇌ Mg2+ ionexchange reaction. Abraded flexural strengths range from 30,000 to 160,000 psi.
123 citations
TL;DR: In this article, the spectroscopic properties of Ni(2+)-doped nanocrystalline glass-ceramic fibers are reported, showing strong fluorescence with peak wavelength at 1250 nm, 3-dB bandwidth at 250nm, measured lifetimes at >1ms, and low-fluorescence saturation powers (~35mW) for 980-nm diode pumping.
Abstract: The spectroscopic properties of Ni(2+)- doped nanocrystalline glass-ceramic fibers are reported. The cerammed fibers show strong fluorescence with peak wavelength at 1250 nm, 3-dB bandwidth at ~250nm, measured lifetimes at >1ms, and low-fluorescence saturation powers (~35mW) for 980-nm diode pumping. Current diode-pumped output powers are ~100microW .
114 citations
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TL;DR: The mechanical properties of nanocrystalline materials are reviewed in this paper, with emphasis on their constitutive response and on the fundamental physical mechanisms, including the deviation from the Hall-Petch slope and possible negative slope, the effect of porosity, the difference between tensile and compressive strength, the limited ductility, the tendency for shear localization, fatigue and creep responses.
3,828 citations
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01 Jan 1995
TL;DR: In this paper, the topology of the tetrahedral linkage and the efficiency of space filling are compared for the various polymorphs of SiO2, and the displacive transformations from a more open high-temperature form (e.g., "high" or "h") to a denser form stable at lower temperatures (α quartz or cristobalite) are discussed.
Abstract: With very few exceptions the numerous polymorphs of SiO2 all consist of SiO4 tetrahedra linked through their corners, thus forming three-dimensional framework structures. The topology of the tetrahedral linkage and the efficiency of space filling are different for the polymorphs. For a given type of framework, for example, that of quartz or cristobalite, space filling can be improved by so-called displacive transformations from a more open high-temperature form (e.g., “high”, “h”, or β “quartz”) to a denser form stable at lower temperatures (“low” or “α quartz”). These transformations do not change the topology of the framework, i.e., chemical bonds in a crystal can be deformed, but are not broken and rearranged.
2,101 citations
TL;DR: In this paper, spectroscopic and diffraction studies of simple phosphate glasses, including v-P2O5 and binary phosphate compositions, are described and special attention is given to the structures of anhydrous ultraphosphate glasses, which have received close attention from the glass community only in the past six years.
Abstract: Recent developments of phosphate glasses for a variety of technological applications, from rare-earth ion hosts for solid state lasers to low temperature sealing glasses, have led to renewed interest in understanding the structures of these unusual materials. In this review, spectroscopic and diffraction studies of simple phosphate glasses, including v-P2O5 and binary phosphate compositions, are described. Special attention is given to the structures of anhydrous ultraphosphate glasses, which have received close attention from the glass community only in the past six years.
1,312 citations
01 Mar 2010
TL;DR: In this article, the authors review the structure and properties of bone, focusing on mechanical deformation and fracture behavior from the perspective of the multidimensional hierarchical nature of its structure and derive its resistance to fracture with a multitude of deformation mechanisms at many size scales ranging from the nanoscale structure of protein molecules to the macroscopic physiological scale.
Abstract: One of the most intriguing protein materials found in nature is bone, a material composed of assemblies of tropocollagen molecules and tiny hydroxyapatite mineral crystals that form an extremely tough, yet lightweight, adaptive and multifunctional material. Bone has evolved to provide structural support to organisms, and therefore its mechanical properties are of great physiological relevance. In this article, we review the structure and properties of bone, focusing on mechanical deformation and fracture behavior from the perspective of the multidimensional hierarchical nature of its structure. In fact, bone derives its resistance to fracture with a multitude of deformation and toughening mechanisms at many size scales ranging from the nanoscale structure of its protein molecules to the macroscopic physiological scale.
504 citations
TL;DR: In this article, two types of nanocrystalline glass-ceramics are studied: transparent glass and high-modulus glass with precisely engineered surfaces, and the key crystalline phases include β-quartz solid solutions, characterized by low-thermalexpansion behavior; spinel, with high hardness and elastic modulus; and mullite, which shows unique chromium-luminescence behavior.
Abstract: Future applications for glass-ceramics are likely to capitalize on designed-in, highly specialized properties for the transmission, display, and storage of information. Glass-ceramics with microstructures comprised of uniformly dispersed crystals <100 nm in size offer promise for many potential new applications as well as provide unique attributes for many current products. This paper focuses on two types of nanocrystalline glass-ceramics: transparent glass-ceramics and tough, high-modulus glass-ceramics with precisely engineered surfaces. Transparent glass-ceramics are formed from certain aluminosilicate glasses capable of efficient crystal nucleation and slow growth. The key crystalline phases include β-quartz solid solutions, characterized by low-thermal-expansion behavior; spinel, with high hardness and elastic modulus; and mullite, which shows unique chromium-luminescence behavior.
487 citations