Features of SiAlON synthesis from kaolin

Власова, М.; Vinokurov, V. B.; Grigor'ev, O. N.; Panasyuk, A. D.; Bega, N. D.; Kakazey, M.; Domínguez-Patiño, G.; Domínguez-Patiño, Martha Lilia

doi:10.1016/j.msea.2003.08.030

Cited by 23 publications

(12 citation statements)

References 6 publications

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“…This study continues previous research efforts on the synthesis of sialons from inexpensive natural raw materials [8,9]. Our objective is to examine the densification and phase formation during hot pressing of '-sialons of three compositions produced from natural raw material, kaolin, by carbothermal reduction in nitrogen and to analyze the effect of rare earth metal oxides (Y 2 O 3 , La 2 O 3 , and Sc 2 O 3 ) that activate sintering on this process.…”

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confidence: 66%

“…Thus, in samples with La 2 O 3 -Al 2 O 3 and Sc 2 O 3 -A1 2 O 3 additions, starting Si 3.7 A1 2.3 O 2.3 N 5.7 sialon, for which z = 2.3, disproportionates into two phases during hot pressing: sialon with z = 1.5 (composition shifts toward Si 3 N 4 ) and sialon with 15R-polytype AlN structure. The z value was determined using the linear dependence of the sialon lattice parameter on z derived previously [9]. The chemical composition of the sialon phase was not determined.…”

Section: Resultsmentioning

confidence: 99%

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The Structure and Properties of Si6–z Al z O z N8–z Sialons Hot-Pressed from Powders with Activating Oxide Additions

Neshpor

Panasyuk

Pshenichnaya

et al. 2014

Powder Metall Met Ceram

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The densification and phase formation during hot pressing of three compositions of '-sialon powders produced from natural raw materials (kaolin) by carbothermal reduction in nitrogen atmosphere are studied. It is determined that the onset temperature of shrinkage decreases with increase in z index.Keywords: kaolin, natural raw material, pressing of β'-sialon powders, influence of rare-earth metal oxide additions, hardness, fracture toughness, strength, high-temperature oxidation resistance. INTRODUCTIONBeta-sialon represents a material in which Si can be replaced by Al and N by O. About 2/3 of -Si 3 N 4 is replaced by Al without structural changes to form Al-O. The length of Si-N and Al-O bonds is the same, but the strength of Al-O is much higher than that of Si-N. Aluminum in -sialon is present as AlO 4 but not AlO 6 , which is typical of Al 2 O 3 . Hence, the bond strength in -sialon is 50% higher than in Al 2 O 3 and sialons have improved properties compared to Si 3 N 4 and Al 2 O 3 [1-4].Beta-sialon has formula Si 6-z Al z O z N 8-z , where index z increases from 0 to 4.2. Sintering proceeds in the presence of Y 2 O 3 , MgO, or rare earth metal (REM) oxides. As a solid solution, -sialon has lower vapor pressure than Si 3 N 4 and thus dissolves at lower temperatures. It densifies more easily than Si 3 N 4 during sintering. In addition, low vapor pressure decreases its dissociation at high temperatures. Sialon is thermodynamically more stable than Si 3 N 4 [5-7].Sialon ceramics hold much promise for their high hardness, wear resistance, and corrosion resistance at elevated temperatures. 450This study continues previous research efforts on the synthesis of sialons from inexpensive natural raw materials [8,9]. Our objective is to examine the densification and phase formation during hot pressing of '-sialons of three compositions produced from natural raw material, kaolin, by carbothermal reduction in nitrogen and to analyze the effect of rare earth metal oxides (Y 2 O 3 , La 2 O 3 , and Sc 2 O 3 ) that activate sintering on this process. EXPERIMENTAL PROCEDUREThe sialon powders were produced by carbothermal reduction-nitration of natural kaolins of the Prosyanov deposit: kaolin resulting from dry separation (S 1 ) and wet separation (S 2 ) and raw kaolin (S 3 ). The chemical and phase compositions of these sialons are summarized in Table 1.The main phase in all three powders is '-sialon. According to chemical analysis and X-ray diffraction, the composition of sialon S 3 virtually corresponds to Si 3.7 A1 2.3 O 2.3 N 5.7 (z = 2.3). Besides this phase, there are also small amounts of silicon-aluminum oxynitride (o'-sialon) and ~5-7% iron silicide. The powder S 1 is not singlephase either. X-ray diffraction revealed o'-sialon and SiC, which is indicative of carbothermal reduction-nitration of kaolin in nonequilibrium conditions and incomplete production of sialon. Composition of the '-phase in powder S 1 approximately corresponds to z = 1.85 and in powder S 2 to z = 3. There are also admixtures of mullite an...

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mentioning

confidence: 66%

Section: Resultsmentioning

confidence: 99%

The Structure and Properties of Si6–z Al z O z N8–z Sialons Hot-Pressed from Powders with Activating Oxide Additions

Neshpor

Panasyuk

Pshenichnaya

et al. 2014

Powder Metall Met Ceram

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“…In addition to the above-mentioned ceramic bonding phases, the Sialon phases in Al 2 O 3 -C refractories provide certain advantages due to their higher bonding capabilities and exemplary thermal shock resistance [11,12]. Galinari and Dutra [13] studied Sialon-reinforced Al 2 O 3 -C refractories and found that Sialon increased the strength of the materials from 110 MPa to 380 MPa and drastically improved their abrasion and thermal shock resistances.…”

Section: Introductionmentioning

confidence: 99%

In-situ synthesis mechanism of plate-shaped β-Sialon and its effect on Al2O3–C refractory properties

Deng¹,

Li²,

Zhu³

et al. 2015

Ceramics International

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“…Silicon nitride and oxynitride ceramics have attracted interest in high temperature engineering applications for nearly 50 years, because of their excellent properties: (1) high strength; (2) wear resistance; (3) high decomposition temperature; (4) oxidation resistance; (5) thermal shock resistance; (6) low coefficient of friction; and (7) resistance to corrosive environments.…”

Section: Introductionmentioning

confidence: 99%

“…Silicon nitride and oxynitride ceramics have attracted interest in high temperature engineering applications for nearly 50 years, 1 because of their excellent properties [2][3][4] : (1) high strength;…”

Section: Introductionmentioning

confidence: 99%

Carbon Fiber Reinforced β‐SiAlON for Ultra High Temperature Ablative Heat Shields

Bahramian

Kokabi

Soorbaghi

2012

Int J Applied Ceramic Tech

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The aim of this study is to give information on the influence of the experimental conditions to estimate thermal diffusivity of carbon fiber reinforced b-SiAlON ablative composite. Here, we present the inverse solution technique to estimate the parameter used to identify the effective thermal diffusivity. The transient temperature measurements, taken from the top surface and through the thickness of the samples in oxyacetylene flame test, are used in the inverse analysis. The results of this study clarify the mechanism of the ablation and thermal diffusivity of the b-SiAlON-based composite heat shields due to the ultra high temperature ablation. NomenclatureBi : Biot number C : Heat capacity (J/kg/K) C p : Heat capacity of the air (J/kg/K) h : Heat convection coefficient (J/m 2 ÁK/s) I : Enthalpy of surrounding hot gas (J/kg) K : Thermal conductivity (J/m/s/K) L 0 : The initial thickness (m) q e : The convective heat flux carried off from the surrounding into the surface (J/s/m 2 ) q K : The heat flux consumed for warming the sample due to heat conduction (J/s/m 2 ) q rw : The radiation heat flux carried off from the surface at the expense of own radiation of the surface (J/s/m 2 ) q w : The convective heat flux carried off from the heated surface heated up to temperature T w into the surrounding (J/s/m 2 ) R : Universal gas constant (J/kg/mol/K) s : Char moving boundary (m) t : Time (s) T : Absolute temperature (K) T e : Hot gas temperature (K) *abahramian@modares.ac.ir

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Features of SiAlON synthesis from kaolin

Cited by 23 publications

References 6 publications

The Structure and Properties of Si6–z Al z O z N8–z Sialons Hot-Pressed from Powders with Activating Oxide Additions

The Structure and Properties of Si6–z Al z O z N8–z Sialons Hot-Pressed from Powders with Activating Oxide Additions

In-situ synthesis mechanism of plate-shaped β-Sialon and its effect on Al2O3–C refractory properties

Carbon Fiber Reinforced β‐SiAlON for Ultra High Temperature Ablative Heat Shields

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