Preparation of High-Purity Silicon Tetrafluoride by Thermal Dissociation of Na<sub>2</sub>SiF<sub>6</sub>

Буланов, А. Д.; Pryakhin, D. A.; Balabanov, V. V.

doi:10.1023/b:rjac.0000012654.22326.e5

Cited by 11 publications

(5 citation statements)

References 10 publications

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“…The model makes the following assumptions: (1) spherical symmetry, (2) isothermal particle, (3) the reaction is irreversible, and (4) no volume change throughout the reaction. Based on thermodynamic calculations and on previous reports from the literature, the reaction at the spherical surface is given by the following equation:

\begin{matrix} true \\ right {Na}_{2} {SiF}_{6 ((), s)} \to {NaF}_{(normals)} + {SiF}_{4 ((), g)} \end{matrix}

…”

Section: Resultsmentioning

confidence: 99%

“…There are five methods for production of silicon tetrafluoride (SiF 4 ) at a laboratory scale: (a) reaction of elemental silicon with fluorinating agents (b) fluorination of silicon dioxide , (c) fluorination of silicon tetrachloride (d) decomposing fluorosilicic acid with concentrated acids , and (e) thermal dissociation of metal hexafluorosilicates . The obtained SiF 4 by the latter method from Na 2 SiF 6 is of high purity, because the solid by‐product, sodium fluoride, absorbs impurities.…”

Section: Introductionmentioning

confidence: 99%

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Mechanism and Parameters Controlling the Decomposition Kinetics of Na₂SiF₆ Powder to SiF₄

Soltani

Pech-Canul

González

et al. 2016

Int J of Chemical Kinetics

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Sodium hexafluorosilicate (Na 2 SiF 6 ) powder has been used as a silicon source for formation of Si 3 N 4 coatings by the hybrid precursor system-chemical vapor deposition (HYSY-CVD) route. The quantitative effect of processing time, temperature, gas flow rate, and process atmosphere (N 2 and N 2 :5% NH 3 ) upon the fractional weight loss during the decomposition of Na 2 SiF 6 was studied using a standard L 9 Taguchi experimental design and analysis of variance. The decomposition kinetics of Na 2 SiF 6 (s) was studied theoretically and experimentally in the temperature range of 550-650ºC by applying the shrinking core model. It was found that regardless of atmosphere type, the reaction order is n 0.12 and that a two-stage mixed mechanism consisting of chemical reaction and boundary layer gas transfer controls the decomposition rate. The determined fractional weight loss during Na 2 SiF 6 decomposition in nitrogen atmosphere is about 1.05-1.5 orders of magnitude greater than that in N 2 :NH 3 . The gas flow rate affects the dissociation activation energy, being of 121, 109, and 94 kJ/mol in N 2 and of 140, 120, and 115 kJ/mol in N 2 :NH 3 , for the flow rates of 20, 60, and 100 cm 3 /min, respectively, in both atmosphere types. A good agreement is observed by comparing experimental weight loss data with model predictions.

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\begin{matrix} true \\ right {Na}_{2} {SiF}_{6 ((), s)} \to {NaF}_{(normals)} + {SiF}_{4 ((), g)} \end{matrix}

…”

Section: Resultsmentioning

confidence: 99%

Section: Introductionmentioning

confidence: 99%

Mechanism and Parameters Controlling the Decomposition Kinetics of Na₂SiF₆ Powder to SiF₄

Soltani

Pech-Canul

González

et al. 2016

Int J of Chemical Kinetics

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“…1), the decomposition of sodium fluorosilicate (Na 2 SiF 6 ), the hydrolysis of magnesium fluoride (MgF 2 ), etc. [8][9][10][11][12]. Therefore, an elevation of the temperature in the reaction blends (T 600 • C) was accompanied by complex solid-phase reactions with the participation of the liquid and gaseous phases (for the melt with oxide-fluoride composition) promoting the melting of blends.…”

Section: Resultsmentioning

confidence: 99%

Ultra Fine Layered Silicate Synthesis from Synthetic Silicate Raw Material

Khachatryan

Yeritsyan

2010

Composite Interfaces

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This paper reports the results of experiments on ultra fine layered silicates Na-fluorotaeniolite and Na-fluorotetrasilicic mica synthesis in the melts prepared from reaction blends based on synthetic silicate raw material, namely synthetic magnesium silicate dihydrate (MSDH, MgO · SiO 2 · 2H 2 O). The MSDH-Na 2 SiF 6 -LiF, MSDH-Na 2 SiF 6 -MgF 2 and MSDH-Na 2 SiF 6 -NaF blends, whose compositions are close to the stoichiometry of the Na-fluorotaeniolite (NaMg 2 Li[Si 4 O 10 ]F 2 ) and Na-fluorotetrasilicic mica (NaMg 2.5 [Si 4 O 10 ]F 2 ) were studied in the temperature range 1080-1225 • C.Magnesium silicate dihydrate, the phase composition of synthesis products and layered silicates (Nafluorotaeniolite and Na-fluorotetrasilicic mica) were examined using the crystal optical, X-ray diffraction at room and high temperatures, differential thermal and chemical analyses.It has been shown that studied blends possessed a high reactivity, owing to which the layered silicates were synthesized at lower temperatures (∼180-300 • C) and the duration of the synthesis was shortened severalfold. The maximal yield of the Na-fluorotetrasilicic mica was observed in the reaction blend with the Na 2 SiF 6 and NaF as halogen-containing compounds. The specific effects of MSDH on the physicochemical processes proceeded during heat treatment of the reaction blends were described. © Koninklijke Brill NV, Leiden, 2010 KeywordsReinforcing and powering fillers, ultra fine layered silicate, synthetic silicate raw material, melt, fluorotetrasilicic mica

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Section: Introductionmentioning

confidence: 99%

“…Sodium hexafluorosilicate is an odorless, white powder of hexagonal crystals (MW=188.06, density=2.679 g/cm 3 ). It is used as a fluoridation agent for drinking water 1 , insecticide, rodenticide and veterinary treatment for lice 2 , production of high purity silicon tetrafluoride 3 , and the production of enamels for china and porcelain products. Sodium hexafluorosilicate is used widely in industry, for a selective removal of surface acidity in zeolite ZSM-5, in photovoltaic applications 4 , synthesis of mesoporous silica 5 , dealumination of MCM-22 zeolite and ferrietite, as active agents in the formulation of mouth washes and dentifrices, synthesis of advanced ceramic materials 6 , and as catalysis products in the frosted glass industry 7 .…”

Section: Introductionmentioning

confidence: 99%

The effect of reaction conditions on the precipitation of sodium hexafluorosilicate produced from waste hexafluorosilicic acid

Batiha

Al-Harahsheh

2011

Polish Journal of Chemical Technology

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The purpose of the study is to investigate the optimum conditions for the precipitation of sodium hexafluorosilicate (Na 2 SiF 6) from waste hexafluorosilicic acid, an effluent from the phosphoric acid industry. Sodium chloride and sodium hydroxide were used as reactants to produce Na 2 SiF 6. The effect of various parameters on the precipitation was investigated and includes; the molar ratio of the reactants, contact time, the temperature and the effect of seeding. The optimum reaction conditions were found to be as follows; excess sodium chloride or sodium hydroxide to hexafluorosilicic acid of 25%, contact time 40 minutes and a reaction temperature of 40°C. The reaction of hexafluorosilicic acid with an aqueous solution of sodium chloride at optimum conditions gave a maximum yield of 94.26% Na 2 SiF 6 while the reaction of hexafluorosilicic acid with the aqueous solution of sodium hydroxide at optimum conditions gave a maximum yield of 97.3% Na 2 SiF 6. The X-Ray diffraction (XRD) analysis reveals that the only crystals present in the precipitate are Na 2 SiF 6. Also, Scanning Electron Microscope (SEM) analysis shows that the different morphology of these crystals depend on the precipitation conditions.

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Preparation of High-Purity Silicon Tetrafluoride by Thermal Dissociation of Na₂SiF₆

Cited by 11 publications

References 10 publications

Mechanism and Parameters Controlling the Decomposition Kinetics of Na₂SiF₆ Powder to SiF₄

Mechanism and Parameters Controlling the Decomposition Kinetics of Na₂SiF₆ Powder to SiF₄

Ultra Fine Layered Silicate Synthesis from Synthetic Silicate Raw Material

The effect of reaction conditions on the precipitation of sodium hexafluorosilicate produced from waste hexafluorosilicic acid

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Preparation of High-Purity Silicon Tetrafluoride by Thermal Dissociation of Na2SiF6

Cited by 11 publications

References 10 publications

Mechanism and Parameters Controlling the Decomposition Kinetics of Na2SiF6 Powder to SiF4

Mechanism and Parameters Controlling the Decomposition Kinetics of Na2SiF6 Powder to SiF4

Ultra Fine Layered Silicate Synthesis from Synthetic Silicate Raw Material

The effect of reaction conditions on the precipitation of sodium hexafluorosilicate produced from waste hexafluorosilicic acid

Contact Info

Product

Resources

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Preparation of High-Purity Silicon Tetrafluoride by Thermal Dissociation of Na₂SiF₆

Mechanism and Parameters Controlling the Decomposition Kinetics of Na₂SiF₆ Powder to SiF₄

Mechanism and Parameters Controlling the Decomposition Kinetics of Na₂SiF₆ Powder to SiF₄