Causes of Phase Separation in Simple Silicate Systems

Galakhov, F. Ya.; Varshal, B. G.

doi:10.1007/978-1-4757-0157-9_2

Cited by 4 publications

(6 citation statements)

References 7 publications

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“…In G1.00, both Si and Al phase separation are observable to greater extent. It has been reported that Mg shows higher phase separation tendencies than Na in silicate systems (Galakhov and Varshal, 1973;Kreidl, 1991;Hudon and Baker, 2002). This can explain the phase separation observed in compositions close to magnesium endmember.…”

Section: Understanding Phase Separation In Glasses Through Semmentioning

confidence: 79%

“…They suggested that the electrostatic bond strength (Z/C n , where Z and C n represent cation charge and coordination number respectively) of the network-modifying cations influences the shape of liquidus curve and the immiscibility. Galakhov and Varshal (1973) proposed that cationic field strength (Z/r 2 ) is the significant factor controlling phase separation in simple silicate systems. The network-modifying cations with higher field strength produces greater phase separation.…”

Section: Understanding Phase Separation In Glasses Through Semmentioning

confidence: 99%

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Field Strength of Network-Modifying Cation Dictates the Structure of (Na-Mg) Aluminosilicate Glasses

et al. 2020

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Aluminosilicate glasses are materials with a wide range of technological applications. The field strength of network-modifying cations strongly influences the structure of aluminosilicate glasses and their suitability for various applications. In this work, we study the influence of the field strength of network-modifying cations on the structure of [(Na 2 O) 1−x (MgO) x (Al 2 O 3) 0. 25 (SiO 2) 1. 25 ] glasses. Due to the higher cation field strength of magnesium than sodium, magnesium prefers the role of network modifier, while sodium preferentially acts as a charge compensator. When magnesium replaces sodium as network modifier, Q 3 silicon species are converted into Q 2 species. The replacement of sodium with magnesium as charge compensator leads to the following changes: (1) the proportion of aluminum-rich Q 4 species [Q 4 (4Al) and Q 4 (3Al)] decreases, while the proportion of aluminum-deficient Q 4 species [Q 4 (2Al) and Q 4 (1Al)] increases; and (2) there is an increased tendency for phase separation between silica-rich and alumina-rich glasses.

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Section: Understanding Phase Separation In Glasses Through Semmentioning

confidence: 79%

Section: Understanding Phase Separation In Glasses Through Semmentioning

confidence: 99%

Field Strength of Network-Modifying Cation Dictates the Structure of (Na-Mg) Aluminosilicate Glasses

et al. 2020

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“…The study of the formation of hierarchical structures deserves special attention. One of these processes is phase decay and, in particular, separation in the liquid phase -miscibility gap [10][11][12][13][14][15][16][17][18][19][20]. The structures that appear upon rapid cooling of samples from the miscibility gap can be classified as hierarchical due to the appearance of a number of sublevels with rounded inclusions ranging in size from 0.01 to 10 µm [11].…”

Section: Introductionmentioning

confidence: 99%

Phase equilibria and materials in the TiO2-SiO2-ZrO2 system: a review

Kirillova¹,

Almjashev²,

Stolyarova³

2021

Nanosystems: Phys. Chem. Math.

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This paper analyzes the available data on phase equilibria in the TiO 2 -SiO 2 -ZrO 2 system. The advantages of specialized databases and software systems for the analysis of information on phase equilibria are pointed. Phase diagrams are kind of a roadmap for the design of materials. As shown in the review, nanomaterials are no exception to this. Data on phase equilibria, such as eutectic points, solubility limits, binodal and spinodal curves, make it possible to predict the possibility of the formation of nanoscale structures and materials based on them. In its turn during the transition to the nanoscale state, the mutual component solubility, the temperature of phase transformation may change significantly, and other features may become observable. This provides additional variability when choosing compositions and material design based on the phases of a given system. As an example, for design of nuclear fuel assemblies that are tolerant to severe accidents at nuclear power plants, mixed carbides (so-called MAX-phases) are considered as one of the most promising options as nanoscale layers on fuel cladding. It is suggested that the materials of the TiO 2 -SiO 2 -ZrO 2 system, which are the product of oxidation of some MAX-phases, can serve as an inhibitor of their further corrosion. Ensuring the stability of materials based on MAX-phases expands their prospects in nuclear power. This requires comprehensive information about phase equilibria and formation conditions of nanostructured states in the analyzed system.

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“…The liquid immiscibility in simple silicate systems is attributed to the formation of network modifying cations into cation-oxygen groups, which differ from silica oxygen (network forming) ones (Galakhov and Varshal, 1969;Varshal, 1981). The distribution of net work forming cations and modifier cations in the melt structure leads to the differentiation between polymer ized and depolymerized domains in the melt and, cor respondingly, to the splitting of liquid into two phases.…”

Section: Previous Studies and Formation Mechanism Of The Immiscibilitmentioning

confidence: 98%

“…3. The average com positions of urtites and lujavrites from different units of the differentiated complexes of the Lovozero alka line massif (Gerasimovskii et al, 1966) and those of loparites and urtites, malignites and lujavrites (Vlasov et al, 1959) are shown for comparison. It is seen that natural objects are close in composition to run prod ucts produced by liquid immiscibility in the melts, exclusively, in the presence of aqueous fluid.…”

Section: Experimental Studies Of Alkaline Magmaticmentioning

confidence: 99%

Experimental study of liquid immiscibility in the fluid-magmatic silicate systems containing Ti, Nb, Sr, REE, and Zr

Сук

2012

Petrology

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Aluminosilicate alkaline systems containing Ti, REE (La, Ce), Y, Sr, and Nb were studied exper imentally at T = 1200 and 1250°C and P = 2 kbar in the presence of aqueous and alkaline fluid. In the fluid absent experiments with systems containing the same elements, loparite crystals in a silicate matrix were obtained. These systems in the presence of aqueous and alkaline fluid pressure conditions demonstrate an immiscible splitting into two liquids: (1) aluminosilicate matrix and (2) droplets enriched in Ti, REE (La, Ce), Y, Sr, and Nb, which contain silicate admixture and are compositionally close to loparites. According to approximate estimates, the partition coefficients between the melts of the droplets and aluminosilicate matrix (K = C dr /C sil ) are more than 5 for TiO 2 , < 0.35 for SiO 2 , 10-20 for Nb 2 O 5 , > 15 for REE, and from 2.3 to 7.6 for SrO. Obtained unmixing may be of great significance for explaining the genesis of REE-Nb (loparite) deposits. In addition, the experiments demonstrate that Zr may be accumulated together with Ti and REE due to liquid immiscibility of this type. The partition coefficient of ZrO 2 between the melts of droplets and aluminosilicate matrix (K = C dr /C sil ) according to approximate estimates varies from ~ 3.5 to 9.

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Causes of Phase Separation in Simple Silicate Systems

Cited by 4 publications

References 7 publications

Field Strength of Network-Modifying Cation Dictates the Structure of (Na-Mg) Aluminosilicate Glasses

Field Strength of Network-Modifying Cation Dictates the Structure of (Na-Mg) Aluminosilicate Glasses

Phase equilibria and materials in the TiO2-SiO2-ZrO2 system: a review

Experimental study of liquid immiscibility in the fluid-magmatic silicate systems containing Ti, Nb, Sr, REE, and Zr

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