O. Quénard - Academia.edu (original) (raw)
Papers by O. Quénard
CEAS Space Journal, 2018
This study focuses on the microstructure and mechanical properties of metallic materials produced... more This study focuses on the microstructure and mechanical properties of metallic materials produced by additive layer manufacturing (ALM), especially the Laser Beam Melting process. The influence of the specimen orientation during the ALM process and that of two post-build thermal treatments were investigated. The identified metal powder is Ti-6Al-4V (titanium base). Metallographic analysis show their effects on the microstructure of the metals. Mechanical experiments involving tensile tests as well as toughness tests were performed according to ASTM (American Society for Testing and Materials) norms. The results show that the main influence is that of the thermal treatments; however the manufacturing stacking direction may lead to some anisotropy in the mechanical properties.
The selective reduction in H 2 of oxide solid solutions produces nanocomposite powders in which t... more The selective reduction in H 2 of oxide solid solutions produces nanocomposite powders in which transition metal nanoparticles are dispersed inside and on the surface of the oxide matrix grains. When using a H 2 /CH 4 reducing atmosphere, the metal nanoparticles that form on the surface of the oxide grains act as catalysts for the CH 4 decomposition and, because of their small size at high temperatures (>800 • C), favor the in-situ nucleation and growth of singlewall and thin multiwall carbon nanotubes. This article reviews our results on the synthesis and characterization of M-MgAl 2 O 4 (M = Fe, Fe/Co, Fe/Ni) nanocomposite powders, without and with carbon nanotubes, emphasizing the information that can be derived from Mössbauer spectroscopy as a complement to other characterization techniques.
Nanostructured Materials, 1996
MgAl204-CoA1204 and MgA1204-NiA12O.t solid solutions are synthesized by combustion in urea of the... more MgAl204-CoA1204 and MgA1204-NiA12O.t solid solutions are synthesized by combustion in urea of the appropriate metal nitrates. The selective reduction in hydrogen of these oxidesgives rise to a dispersion of nanometric Co orNiparticles in the spine1 matrix. The reduction of the Cozi andN?+ ions is complete at 900 and 1000°C respectively. Owing to the homogeneity of the starting oxide solid solution, the size distribution of the metal particles is narrow and their average size is about 10 nm. During a thermal treatment in air, the nanometric metal particles located in the open porosity of the matrix are totally oxidized at temperatures lower than 700 "C. whereas those dispersed inside the matrix grains are stable up to 900 "c. These latter particles accountfor more than half of the total metal content.
J. Mater. Chem., 1997
Olivier Quénard,a Eddy De Grave,b Christophe Laurent*a and Abel Rousseta aL aboratoire de Chimie... more Olivier Quénard,a Eddy De Grave,b Christophe Laurent*a and Abel Rousseta aL aboratoire de Chimie des Matériaux Inorganiques, ESA CNRS 5070, Université Paul-Sabatier, 31062 T oulouse cedex 4, France bNUMAT , Department of Subatomic and Radiation Physics, ...
Nanostructured Materials, 1999
Batches of poorly crystalline (GPC) and relatively well crystalline (GNL) goethite, ␣-FeOOH, powd... more Batches of poorly crystalline (GPC) and relatively well crystalline (GNL) goethite, ␣-FeOOH, powders have been suspended in a neutral aqueous medium and heated for three days in a pressure bomb at various temperatures between 100 and 300°C. The parent and resulting products have been characterised by thermogravimetric analyses, X-ray diffraction, BET surface-area measurements, transmission electron microscopy and 57 Fe Mössbauer spectroscopy. While the goethite particles of GNL are not affected by the treatments at up to 275°C, those of GPC initially grow with increasing heating temperature up to ϳ200°C and subsequently become smaller with further increase of the temperature. Above 250°C, GPC produces a mixture of hematite, ␣-Fe 2 O 3 , and maghemite, ␥-Fe 2 O 3. The presence of the latter phase is particularly obvious from the external-field Mössbauer spectrum. After being treated at 300°C, both goethites have completely converted to hematite. The morphology of the parent goethite has no marked effect on the final hematite phase.
Materials Research Bulletin, 2000
Materials Research Bulletin, 2000
MgAl 2 O 4 and x wt% ZrO 2-MgAl 2 O 4 (1 Յ x Յ 30) composite powders were prepared by the urea co... more MgAl 2 O 4 and x wt% ZrO 2-MgAl 2 O 4 (1 Յ x Յ 30) composite powders were prepared by the urea combustion route. The powders were further ground by either ball milling or attrition to refine the grain size. Zirconia was found solely in the tetragonal form. Dense materials were prepared by hot pressing. The spinel matrix grains were submicronic in size. The ZrO 2 particles were homogeneously dispersed at the grain junctions of the matrix, and their average size increased from less than 0.20 m to ca. 0.45 m with increasing content of ZrO 2. The formation of monoclinic ZrO 2 particles proceeded accordingly, being easier in materials with a finer matrix grain size (ex-attrition).
Nanostructured Materials, 1996
ABSTRACT
CEAS Space Journal, 2018
This study focuses on the microstructure and mechanical properties of metallic materials produced... more This study focuses on the microstructure and mechanical properties of metallic materials produced by additive layer manufacturing (ALM), especially the Laser Beam Melting process. The influence of the specimen orientation during the ALM process and that of two post-build thermal treatments were investigated. The identified metal powder is Ti-6Al-4V (titanium base). Metallographic analysis show their effects on the microstructure of the metals. Mechanical experiments involving tensile tests as well as toughness tests were performed according to ASTM (American Society for Testing and Materials) norms. The results show that the main influence is that of the thermal treatments; however the manufacturing stacking direction may lead to some anisotropy in the mechanical properties.
The selective reduction in H 2 of oxide solid solutions produces nanocomposite powders in which t... more The selective reduction in H 2 of oxide solid solutions produces nanocomposite powders in which transition metal nanoparticles are dispersed inside and on the surface of the oxide matrix grains. When using a H 2 /CH 4 reducing atmosphere, the metal nanoparticles that form on the surface of the oxide grains act as catalysts for the CH 4 decomposition and, because of their small size at high temperatures (>800 • C), favor the in-situ nucleation and growth of singlewall and thin multiwall carbon nanotubes. This article reviews our results on the synthesis and characterization of M-MgAl 2 O 4 (M = Fe, Fe/Co, Fe/Ni) nanocomposite powders, without and with carbon nanotubes, emphasizing the information that can be derived from Mössbauer spectroscopy as a complement to other characterization techniques.
Nanostructured Materials, 1996
MgAl204-CoA1204 and MgA1204-NiA12O.t solid solutions are synthesized by combustion in urea of the... more MgAl204-CoA1204 and MgA1204-NiA12O.t solid solutions are synthesized by combustion in urea of the appropriate metal nitrates. The selective reduction in hydrogen of these oxidesgives rise to a dispersion of nanometric Co orNiparticles in the spine1 matrix. The reduction of the Cozi andN?+ ions is complete at 900 and 1000°C respectively. Owing to the homogeneity of the starting oxide solid solution, the size distribution of the metal particles is narrow and their average size is about 10 nm. During a thermal treatment in air, the nanometric metal particles located in the open porosity of the matrix are totally oxidized at temperatures lower than 700 "C. whereas those dispersed inside the matrix grains are stable up to 900 "c. These latter particles accountfor more than half of the total metal content.
J. Mater. Chem., 1997
Olivier Quénard,a Eddy De Grave,b Christophe Laurent*a and Abel Rousseta aL aboratoire de Chimie... more Olivier Quénard,a Eddy De Grave,b Christophe Laurent*a and Abel Rousseta aL aboratoire de Chimie des Matériaux Inorganiques, ESA CNRS 5070, Université Paul-Sabatier, 31062 T oulouse cedex 4, France bNUMAT , Department of Subatomic and Radiation Physics, ...
Nanostructured Materials, 1999
Batches of poorly crystalline (GPC) and relatively well crystalline (GNL) goethite, ␣-FeOOH, powd... more Batches of poorly crystalline (GPC) and relatively well crystalline (GNL) goethite, ␣-FeOOH, powders have been suspended in a neutral aqueous medium and heated for three days in a pressure bomb at various temperatures between 100 and 300°C. The parent and resulting products have been characterised by thermogravimetric analyses, X-ray diffraction, BET surface-area measurements, transmission electron microscopy and 57 Fe Mössbauer spectroscopy. While the goethite particles of GNL are not affected by the treatments at up to 275°C, those of GPC initially grow with increasing heating temperature up to ϳ200°C and subsequently become smaller with further increase of the temperature. Above 250°C, GPC produces a mixture of hematite, ␣-Fe 2 O 3 , and maghemite, ␥-Fe 2 O 3. The presence of the latter phase is particularly obvious from the external-field Mössbauer spectrum. After being treated at 300°C, both goethites have completely converted to hematite. The morphology of the parent goethite has no marked effect on the final hematite phase.
Materials Research Bulletin, 2000
Materials Research Bulletin, 2000
MgAl 2 O 4 and x wt% ZrO 2-MgAl 2 O 4 (1 Յ x Յ 30) composite powders were prepared by the urea co... more MgAl 2 O 4 and x wt% ZrO 2-MgAl 2 O 4 (1 Յ x Յ 30) composite powders were prepared by the urea combustion route. The powders were further ground by either ball milling or attrition to refine the grain size. Zirconia was found solely in the tetragonal form. Dense materials were prepared by hot pressing. The spinel matrix grains were submicronic in size. The ZrO 2 particles were homogeneously dispersed at the grain junctions of the matrix, and their average size increased from less than 0.20 m to ca. 0.45 m with increasing content of ZrO 2. The formation of monoclinic ZrO 2 particles proceeded accordingly, being easier in materials with a finer matrix grain size (ex-attrition).
Nanostructured Materials, 1996
ABSTRACT