Mechanical Properties of CaO–Al2O3–SiO2 Glass-Ceramics Precipitating Hexagonal CaAl2Si2O8 Crystals

Abstract

Fracture behavior via a flexural test for a newly found CaO–Al2O3–SiO2 (CAS) glass-ceramic (GC) was compared with that of enstatite GC and mica GC, which are well-known GCs with high-fracture toughness and machinability, respectively. By focusing on the nonelastic load–displacement curves, CAS GC was characterized as a less brittle material similar to machinable mica GC, compared with enstatite GC, which showed higher fracture toughness, KIC. The microcrack toughening mechanism in CAS GC was supported by the nondestructive observation of microcracks around the Vickers indentation using the X-ray microcomputed tomography technique. The CAS GC also showed higher transparency than mica GC due to its low crystallinity. Moreover, the precursor glass had easy formability due to its low-liquidus temperature.

Effects of kaolinite layer expansion and impurities on the solid-state reaction of kaolinite

“…33 , exhibits phosphorescence when doped with rare earth ions. 34 Additionally, the CaO-Al 2 O 3 -SiO 2 glass-ceramic precipitated metastable CaAl 2 Si 2 O 8 crystals shows improved mechanical properties and unique fracture behavior 35 that is currently under investigaiton. Amorphous metastable CaAl 2 -Si 2 O 8 has also been shown to efficiently remove heavy metal ions from solutions in conjunction with a minimal increase in pH.…”

“…Metastable CaAl 2 Si 2 O 8 containing anorthite, the stable phase of CaAl 2 Si 2 O 8 , can be produced by the calcination of a mixture of ground CaCO 3 and Georgia kaolinite (GK), a brown kaolinite, for 12 h. 10 Metastable CaAl 2 Si 2 O 8 , a series of layered inorganic solids having the formula RAl 2 Si 2 O 8 (where R is an alkali metal cation) 33 , exhibits phosphorescence when doped with rare earth ions. 34 Additionally, the CaO–Al 2 O 3 –SiO 2 glass–ceramic precipitated metastable CaAl 2 Si 2 O 8 crystals shows improved mechanical properties and unique fracture behavior 35 that is currently under investigaiton. Amorphous metastable CaAl 2 Si 2 O 8 has also been shown to efficiently remove heavy metal ions from solutions in conjunction with a minimal increase in pH.…”

Unique properties and potential of glass-ceramics

“…37) Maeda et al also focused on the so-called R-curve behavior 38),39) of the CAS glass-ceramics during fracture, and mentioned the similarity with mica-based glass-ceramics. 40) It has been considered that the ease of microcrack formation due to the strong cleavage of the hexagonal CaAl 2 Si 2 O 8 crystal, as well as mica, plays a significant role in the high toughness of those glass-ceramics. The effort to understand the effect of the microcrack formation on increasing toughness using X-ray micro-CT is underway.…”

Spectroscopic and Surface Crystallization Characterizations of Yttrium-Doped Phosphate Glasses

“…Glass-ceramics have been widely reported and are generally obtained by using heat treatment techniques to control the crystallization of glass samples. The literature indicates that glass-ceramics possess better mechanical performance and higher chemical and thermal stability than the parent glasses; in particular, the presence of regular nano-crystals is helpful to improving the properties of glass-ceramics [11][12][13]. However, iron phosphate glass-ceramics containing rare earth elements have received less attention [7,10,14].…”