Study of the sintering and oxidation behavior to the HfB2/SiC system. Synthesis, reactivity and chemical-physical characterization.

HAL Id: hal-01375962

https://hal-unilim.archives-ouvertes.fr/hal-01375962

Submitted on 3 Oct 2016

HAL is a multi-disciplinary open access archive for the deposit and dissemination of sci- entific research documents, whether they are pub- lished or not. The documents may come from teaching and research institutions in France or abroad, or from public or private research centers.

L’archive ouverte pluridisciplinaire HAL, est destinée au dépôt et à la diffusion de documents scientifiques de niveau recherche, publiés ou non, émanant des établissements d’enseignement et de recherche français ou étrangers, des laboratoires publics ou privés.

Study of the sintering and oxidation behavior to the HfB2/SiC system. Synthesis, reactivity and

chemical-physical characterization.

Cassandre Piriou, Olivier Rapaud, Ludovic Charpentier, Sylvie Foucaud

To cite this version:

Cassandre Piriou, Olivier Rapaud, Ludovic Charpentier, Sylvie Foucaud. Study of the sinter- ing and oxidation behavior to the HfB2/SiC system. Synthesis, reactivity and chemical-physical characterization.. 7th International Workshop on Advanced Ceramics, Sep 2016, Limoges, France.

�10.13140/RG.2.2.18838.34885�. �hal-01375962�

Introduction

Study of the sintering and oxidation behavior to the HfB

/SiC system.

Synthesis, reactivity and chemical-physical characterization.

1 : Laboratoire Science des Procédés Céramiques et de Traitements de Surface – UMR CNRS 7315

Université de Limoges – Centre Européen de la Céramique, 12 Rue Atlantis, F-87068 Limoges Cedex - France

C. Piriou¹, O. Rapaud¹, L. Charpentier², S. Foucaud¹

Study of sintering and oxidation behaviour

2 : Laboratoire Procédés, Matériaux et Energie Solaire – UPR CNRS 8521 7 Rue du Four Solaire, 66120 Font Romeu Odeillo - France

The first aim of our work consists in synthesizing Ultra High Temperature HfB₂/SiC ceramics, used as structural materials in aeronautic and aerospace areas, by Spark Plasma Sintering (SPS). This process is used to obtain fully dense materials (>99% relative density) with fine grains, at lower sintering temperature and shorter dwell time than conventional techniques. Sintered materials are then oxidized in a solar furnace and characterized in order to better understand the oxidation mechanisms.

Conclusion

Spark Plasma Sintering (SPS)

Oxidation in solar furnace

Characterization of oxidized products

Electrode

Piston (graphite) Sample

Matrix (graphite) Spacer

HfB₂* 5µm

SiC

1µm > 99% relative

density

SiC content (% vol.)

Sintering temperature

(°C)

Relative density

(%)

0 1850 100

5 1850 99

10 1800 100

15 1750 100

20 1750 100

25 1700 99

c-HfC (00-039-1491)

10 30 50 70

Intensity (a.u.)

2θ (°)

1450K 1550K 1800K

m-HfO₂ (00-034-0104) h-HfB₂ (00-038-1398) α-SiC (00-029-1131)

m-SiO₂ (00-051-1377)

• Sintering of fully dense HfB₂/SiC ceramics by Spark Plasma Sintering

• Decrease of sintering temperature with the addition of silicon carbide

• Oxidation tests carried out with a solar furnace up to 1800K under stagnant air

Mass gain

Protective oxide layer

Slower mass gain rate for

80% vol. HfB₂ +

20% vol. SiC

• Slower mass gain rate for the composition 80% vol. HfB₂ + 20% vol. SiC

• Different microstructures observed depending on the oxidation temperature and ceramic composition.

1450 K

1550 K

1800 K 1450 K

1550 K

1800 K

Solar flux

Exposed surfaces

c-HfC (00-039-1491) m-HfO₂ (00-034-0104) h-HfB₂ (00-038-1398) α-SiC (00-029-1131)

• Appearance of hafnium and silicon dioxides

• Increase of dioxides intensity peaks with

temperature

• Silicon carbide grains growth with oxidation

temperature

• External oxide layer growth with oxidation

temperature

H80S20

SiC

Black grains

HfB₂

Grey grains

*Milled powder

1650 1700 1750 1800 1850

0 10 20

Sintering temperature (°C)

SiC content (% vol.)

H100 H95S5 H90S10 H85S15 H80S20 H75S25

10 30 50 70

Intensity (a.u.)

2θ (°)

H100 H95S5 H90S10 H85S15 H80S20 H75S25

Surface Section

Surface

0 5 10 15 20

1200 1400 1600 1800

Mass gain rate (mg.cm-2 .h-1 )

Temperature (K)

H100 H95S5 H90S10 H85S15 H80S20

*

* H95S5: 95% vol. of milled HfB₂ + 5% vol. SiC

The milling was carried out in a planetary mill during 30 minutes containing 6 cycles of 6 minutes (1 minute of milling and 5 minutes rest).