Self‐Organized Growth of Sodium Borate‐Rich Droplets in a Phase‐Separated Sodium Borosilicate Glass

Abstract

A glass with the composition 60 SiO2, 37 B2O3, and 3 Na2O was casted and subsequently cooled to room temperature. During subsequent heat treatment at temperatures in the range from 520 to 680°C, the glass shows phase separation and SiO2‐rich droplets in a B2O3‐rich matrix are formed. The droplet size strongly depends on the temperature and duration of heat treatment. In the dilatometric curves of the phase‐separated glasses, two glass transition temperatures are observed. At high annealing temperatures, the transition temperatures vary according to the decomposition cupola. At lower temperatures, the phase formation is restricted by the kinetics. Particle sizes and growth rates are not governed by Ostwald ripening and deviate from the expected rate law d ~ t1/3. The exponent in the rate law is much smaller than one‐third, and hence, the coarsening of the droplet structured is hindered. In analogy to crystal growth models reported in the literature, this growth hindrance is explained by the formation of a highly viscous shell around growing particles.

Structural Origins of BaF2/Ba1 −xRxF2 +x/RF3 Nanocrystals Formation from Phase Separated Fluoroaluminosilicate Glass: A Molecular Dynamic Simulation Study

“…The glass former tetrahedra, [SiO 4 ] and [AlO x F y ], on the oxide–fluoride phase interface are the potential structures to develop into a rigid shell around the fluoride‐rich phase, limiting the size of the precipitating fluoride nanocrystals. This is called self‐limiting crystallization in experiments . In these referred experiment studies, the time of the thermal treatment does not affect the crystal size.…”

“…[21] Na + initially charge compensates [AlO 4 ] − in the oxide phase. [24,25,43,47,[49][50][51] In these referred experiment studies, the time of the thermal treat-ment does not affect the crystal size. Owing to a more compact structure is formed in aluminosilicate oxide phase after fluoride phase separation, Na + is not preferred to bond to [SiO 4 ] and create NBOs in the aluminosilicate oxide-rich phase.…”

Stress Corrosion Cracking in Amorphous Phase Separated Oxide Glasses: A Holistic Review of Their Structures, Physical, Mechanical and Fracture Properties

“…Moreover, kinetic factors also have essential effects on the phase separation processes. For a given glass with a chemical composition within the miscibility gap, annealing protocols determine: (1) the phase composition while attaining equilibrium (Section 3.1), (2) the type of phase separation (binodal or spinodal) [83], (3) the nucleation/growth kinetics in the miscibility gaps [77,102], and (4) the final phase compositions and phase size [94,103,104]. The next section focuses on different structures of some APS-SBN (amorphous phase separated SBN) glasses.…”

“…Ternary oxide SBN system also undergoes binodal decomposition. Häßler and Rüssel [94] investigated a glass with the following chemical composition: [SiO 2 ] = 60.0%, [B 2 O 3 ] = 37.0%, and [Na 2 O] = 3.0%, where [•] implies mol%. The square in Figure 6 depicts the location of the glass system in the ternary oxide phase diagram at 600 • C. It clearly resides in the two-phase area.…”

“…Based on its chemical composition, one expects the structure to be sodium borate-rich particles embedded in a silica-rich matrix [119]. Häßler and Rüssel [94] subjected the samples to various annealing protocols: annealing temperature ranges from 520 • C to 680 • C and annealing times range from 1 h to 100 h. TEM and SEM were used to characterize the medium-range structure of samples. In their studies [94], EDX characterization tests show clearly the occurrence of APS in the samples.…”