![]() Three glass-ceramic samples composed of 16.3%, 28.6% and 56.0% CS content and two other raw materials, quartz and calcium carbonate, were produced. ![]() ![]() Perhaps the first glass-ceramic made with CS was produced by Yetka et al. Iron-rich phases are claimed to impart magnetic, electrical and thermal properties, as well as a brownish shade, to glass-ceramics ( Chinnam et al., 2013). Since CS contains iron, its effect on the crystallisation of glass-ceramics, which has not been studied extensively, can be of interest. Transition metal oxides and sulphides, such as titanium dioxides (TiO 2) and zirconium dioxides (ZrO 2), are typically used as nucleating agents. Glass-ceramics are polycrystalline materials formed by controlling the nucleation and growth of crystal phases within the glass. Chao Qun Lye, in Sustainable Construction Materials: Copper Slag, 2017 3.6.5 Glass-Ceramics A–W glass-ceramics contain crystalline apatite, Ca 10 (PO 4) 6(OH) 2, and wollastonite, CaO–SiO 2, in an MgO–CaO–SiO2 glassy matrix and exhibit greater strength than bioglass and sintered Hap, as demonstrated by Kokubo and co-workers. A typical glass-ceramic is apatite and wollastonite (A–W), which has the ability to form tight chemical bonds with living tissues when implanted in the body. Furthermore, materials with novel properties, known neither in glass nor in ceramic materials, can be designed. Consequently, special combinations of properties can be achieved in this group of materials. Moreover, glass-ceramics exhibit special properties that are characteristic of both glass and ceramic materials. Glass-ceramics are manufactured from base glasses, using the mechanisms of controlled nucleation and crystallisation. Glass-ceramics are multiphase materials, consisting of at least one glass phase and one crystalline phase. Zhao, in Bioactive Materials in Medicine, 2011 Glass-ceramics Furthermore, the advantage of using bioactive glass–ceramics to create scaffolds with high strength has diminished because of the capacity shown recently to create strong porous scaffolds of silicate bioactive glass [ Huang et al., 2011 Q. However, a common difficulty with glass–ceramic scaffolds for tissue engineering applications is the slow and unpredictable degradation resulting from the presence of the crystalline phase. A fluorite-containing glass–ceramic (porosity 23.5–50%), formed by sintering particles with a pore-forming (polyethylene) phase, showed strengths (100–150 MPa) comparable to those of cortical bone. īecause of the tendency of 45S5 glass to crystallize during sintering (which reduces the ability of the glass particles to sinter by viscous flow), glass–ceramic scaffolds of 45S5 glass have low strength, in the range reported for trabecular bone. Since that time, other glass–ceramics and glass–ceramic scaffolds with a variety of composition and architecture have been developed for bone replacement. An early example was the development of apatite/wollastonite (A/W) bioactive glass–ceramics for the replacement of vertebrae. Consequently, one rationale for the development of bioactive glass ceramics was the potential for achieving better mechanical properties. ![]() With a composite structure composed typically of a fine crystalline phase dispersed in a matrix of glass, the glass–ceramic often has better physical and mechanical properties (e.g., strength fracture toughness) than the parent glass formed by melting and casting. Glass–ceramics, as described earlier, are crystallized glasses formed by a controlled heat treatment of the parent glass or as a result of thermal treatment (sintering) during fabrication. Rahaman, in Tissue Engineering Using Ceramics and Polymers (Second Edition), 2014 3.9 Bioactive glass–ceramics ![]()
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