Sandrine Cardinal - Academia.edu (original) (raw)
Papers by Sandrine Cardinal
Journal of Nuclear Materials, 2018
Nano-grained β-silicon carbide (β-SiC) pellets were prepared by Spark Plasma Sintering (SPS). The... more Nano-grained β-silicon carbide (β-SiC) pellets were prepared by Spark Plasma Sintering (SPS). These were implanted at room temperature with 800 keV xenon at ion fluences of 5.10 15 and 1.10 17 cm-2. Microstructural modifications were studied by electronic microscopy (TEM and SEM) and xenon profiles were determined by Rutherford Backscattering Spectroscopy (RBS). A complete amorphization of the implanted area associated with a significant oxidation is observed for the highest fluence. Large xenon bubbles formed in the oxide phase are responsible of surface swelling. No significant gas release has been measured up to 10 17 at.cm-2. A model is proposed to explain the different steps of the oxidation process and xenon bubbles formation as a function of ion fluence.
![Research paper thumbnail of {"__content__"=>"On the Potential of Bulk Metallic Glasses for Dental Implantology: Case Study on TiZrCuPd.", "sub"=>[{"__content__"=>"40"}, {"__content__"=>"10"}, {"__content__"=>"36"}, {"__content__"=>"14"}]}](https://attachments.academia-assets.com/99025735/thumbnails/1.jpg)
](Materials (Basel, Switzerland), Jan 6, 2018
TiZrCuPd Bulk Metallic Glass (BMG) appears very attractive for future biomedical applications tha... more TiZrCuPd Bulk Metallic Glass (BMG) appears very attractive for future biomedical applications thanks to its high glass forming ability, the absence of toxic elements such as Ni, Al or Be and its good mechanical properties. For the first time, a complete and exhaustive characterization of a unique batch of this glassy alloy was performed, together with ISO standard mechanical tests on machined implant-abutment assemblies. The results were compared to the benchmark Ti-6Al-4V ELI (Extra-Low-Interstitial) to assess its potential in dental implantology. The thermal stability, corrosion and sterilization resistance, cytocompatibility and mechanical properties were measured on samples with a simple geometry, but also on implant-abutment assemblies' prototypes. Results show that the glassy alloy exhibits a quite high thermal stability, with a temperature range of 38 °C between the glass transition and crystallization, a compressive strength of 2 GPa, a certain plastic deformation (0.7%)...
Materials Science Forum, 2014
The gold alloys are used in jewelry for their aesthetic appearance and inertia to the environment... more The gold alloys are used in jewelry for their aesthetic appearance and inertia to the environment. In jewelry a hardness superior to 300 HV is desirable to facilitate the final machining and reduce the wear of the final product. The maximum hardness that can be obtained with the standard 18 carats gold (Au75-Ag12.5-Cu12.5 (wt%)) through a combination of heat treatment and cold working is about 290 HV. Gold-based bulk metallic glasses (BMGs) are an alternative as they present unique properties in comparison with crystalline counterparts, especially easy thermoplastic processing combined with a high hardness. Pd-base BMGs are another solution, due also to their attractive features.An Au49Cu26.9Si16.3Ag5.5Pd2.3 (% at.) and a Pd40Cu30Ni10P20 (% at.) bulk metallic glasses were fabricated by a copper mould suction casting technique in an argon atmosphere. In the as-cast state hardness, shear modulus and hardness are high (HV0.3= 360 and 530 in the Au-and Pd-base BMGs, respectively). Vario...
Nuclear Instruments and Methods in Physics Research Section B: Beam Interactions with Materials and Atoms, 2009
Titanium nitride has been proposed as a fission product barrier in fuel structures for gas cooled... more Titanium nitride has been proposed as a fission product barrier in fuel structures for gas cooled fast reactor (GFR) systems. The thermal migration of Cs was studied by implanting 800 keV 133 Cs ++ ions into sintered samples of TiN at an ion fluence of 5 Â 10 15 cm À2. Thermal treatments at temperatures ranging from 1500 to 1650°C were performed under a secondary vacuum. Concentration profiles were determined by 2.5 MeV 4 He + elastic backscattering. The results reveal that the global mobility of caesium in the host matrix is low compared to xenon and iodine implanted in the same conditions. Nevertheless, the evolution of caesium depth profile during thermal treatment presents similarities with that of xenon. Both species are homogeneously transported towards the surface and the transport rate increases with the temperature. In comparison, iodine exhibits singular migration behaviour. Several assumptions are proposed to explain the better retention of caesium in comparison with both other species. The potential role played by the oxidation is underlined since even a slight modification of the surface stoichiometry may modify species mobility. More generally, the apparition of square-like shapes on the surface of the samples after implantations and thermal treatments is discussed.
Thin Solid Films, 2014
ABSTRACT Bulk metallic glasses have attracted considerable attention over the last decades for th... more ABSTRACT Bulk metallic glasses have attracted considerable attention over the last decades for their outstanding mechanical features (high strength, super-elasticity) and physico-chemical properties (corrosion resistance). Recently, some attempts to assign such original behavior from bulk materials to modified surfaces have been reported in the literature based on multicomponent alloys. In this paper we focused on the opportunity to form a metallic glass coating from the binary Zr–Cu system using a magnetron co-sputtering physical vapor deposition process. The composition of the films can be easily controlled by the relative intensities applied to both pure targets, which made possible the study of the whole Zr–Cu system (from 13.4 to 85.0 at.% Cu). The chemical composition of the films was obtained by energy dispersive X-ray spectroscopy, and their microstructure was characterized by scanning and transmission electron microscopy. The thermal stability of the films was deduced from an in situ X-ray diffraction analysis (from room temperature up to 600 °C) and correlated with the results of the differential scanning calorimetry technique. Their mechanical properties were determined by nanoindentation experiments.
Nuclear Instruments and Methods in Physics Research Section B: Beam Interactions with Materials and Atoms, 2010
Micro-Rutherford backscattering spectrometry experiments were performed on a set of sintered tita... more Micro-Rutherford backscattering spectrometry experiments were performed on a set of sintered titanium nitride samples implanted with xenon to a depth of about 150 nm. Implanted samples were annealed at 1500°C during 5 h. Xe depth profile and its lateral distribution on the surface were measured. Surface morphology was observed using scanning electron microscopy. The results reveal that the microstructure plays an important role on xenon release. Moreover, the crystalline orientation of each grain could be a key parameter to explain the heterogeneous evolution of the surface during thermal treatments as well as Xe release from surface.
Journal of Thermal Analysis and Calorimetry, 2012
The free sintering of ceramic powders into fully dense nanostructured materials is still a challe... more The free sintering of ceramic powders into fully dense nanostructured materials is still a challenging process, even more complex when nanostructured transition alumina is used as starting powder. In this paper, biphasic (Alumina-YAG) and triphasic (Alumina-YAG-ZrO 2) composite powders were produced by doping the same nanocrystalline transition alumina with inorganic precursors of the second-phases, which were subsequently yielded under controlled thermal treatments. The added dopants significantly increased both the hto a-phase transformation and the sintering temperatures, making even more difficult the retention of the starting nanometric grain size into the final dense materials. Thermal analyses (such as TG-DTA and dilatometry) are here used to support most of the ceramic processing steps involved in a successful elaboration of the desired ultra-fine structures. In fact, the thermal pre-treatments of the doped powders were set up on the ground of the DTA-TG curves whereas the dilatometric analyses were exploited to design optimised sintering cycles, through which the green bodies were successfully consolidated into fully dense materials, characterised by highly homogeneous and tailored micro/ nanostructures.
Journal of the European Ceramic Society, 2007
Synthesis of titanium nitride (TiN) powders by the self propagating high temperature synthesis (S... more Synthesis of titanium nitride (TiN) powders by the self propagating high temperature synthesis (SHS) process is economically appealing. This chemical reaction allows producing fine grains powders with a high specific surface area (12m2/g). After a thermal treatment above 1000°C under argon atmosphere, the physical and microstructural characteristics of the powders are drastically modified: density increases and specific surface decreases. Powders
Journal of Nuclear Materials, 2008
Titanium nitride is one of the inert matrixes proposed to surround the fuel in gas cooled fast re... more Titanium nitride is one of the inert matrixes proposed to surround the fuel in gas cooled fast reactor (GFR) systems. These reactors will operate at high temperature and refractory materials with a high chemical stability and good mechanical properties are required. Furthermore, a total retention of the most volatile fission products, such as I, Xe or Cs, by the inert matrix is needed during the in-pile process. The isothermal migration of iodine in TiN was studied by implanting 800 keV I ++ ions in sintered samples at an ion fluence of 5 • 10 15 cm À2. Thermal treatments were performed under secondary vacuum at temperatures ranging from 1200 to 1700°C. Iodine concentration profiles were determined by 2.5 MeV a-particle elastic backscattering. The migration of iodine seems to be correlated with point defects created by implanted ions near the surface. The Arrhenius plot corresponding to iodine detrapping is curved with possibly two straight-line regions which could indicate either the presence of two types of traps, or a strong dependence of trap's concentration on temperature above 1500°C. The activation energies associated with each linear region of the Arrhenius plot were found to be: E a = 2.4 ± 0.2 eV below 1500°C and E a 0 ¼ 11:4 AE 0:2 eV above 1500°C. Nitrogen evaporation from TiN surface under secondary vacuum was proposed as a contributing factor to the enhanced mobility of iodine at high temperature.
Journal of Nuclear Materials, 2013
ABSTRACT Titanium nitride is a refractory material that is being considered as an inert matrix in... more ABSTRACT Titanium nitride is a refractory material that is being considered as an inert matrix in future Generation IV nuclear reactors, in particular in relation to the Gas-cooled Fast Reactor. The main role of this matrix would be to act as a barrier against the release of fission products, in particular gaseous ones like xenon. This release phenomenon will be enhanced by high temperatures expected in the fuel vicinity: 1200° C under normal conditions, and up to 1800° C under accidental conditions. It is therefore necessary to investigate the behaviour of volatile fission products in TiN under high temperature and irradiation. Indeed, these basic data are very useful to predict the volatile fission products released under these extreme conditions. Our previous work has shown that Xe introduced by ion implantation in sintered TiN tends to be released as a result of annealing, due to a transport mechanism towards the sample surface. The aim of the present work is to determine under which physical state Xe is in TiN. Xenon was first introduced using ion implantation at 800 keV in TiN samples obtained by hot pressing at several concentrations ranging from 0.4 to 8 at. %. Secondly, samples were annealed at high temperature, from 1000° C to 1500° C. Xe was then characterized by X-ray Absorption Spectroscopy and Transmission Electron Microscopy. The formation of intragranular xenon bubbles was demonstrated, and the xenon concentration which is sufficient to form bubbles is found to be lower than 0.4 at. % under our experimental conditions. These bubbles were found unpressurised at 15 K. Their size increases with the temperature and the local xenon concentration. For the highest xenon concentrations, a mechanism involving the formation of a Xe interconnected bubble network is proposed to explain Xe massive release observed by Rutherford Backscattering Spectrometry experiments.
Journal of Applied Physics, 2011
ABSTRACT Dense TiN and TiC samples were prepared by hot pressing using micrometric powders. Xenon... more ABSTRACT Dense TiN and TiC samples were prepared by hot pressing using micrometric powders. Xenon species (simulating rare gas fission products) were then implanted into the ceramics. The samples were annealed for 1 h at 1500 °C under several degraded vacuums with PO2 varying from 10−6 to 2×10−4 mbars. The oxidation resistance of the samples and their retention properties with respect to preimplanted xenon species were analyzed using scanning electron microscopy, grazing incidence x-ray diffraction, Rutherford backscattering spectrometry, and nuclear backscattering spectrometry. Results indicate that TiC is resistant to oxidation and does not release xenon for PO2 ≤ 6×10−6 mbars. When PO2 increases, geometric oxide crystallites appear at the surface depending on the orientation and size of TiC grains. These oxide phases are Ti2O3, Ti3O5, and TiO2. Apparition of oxide crystallites is associated with the beginning of xenon release. TiC surface is completely covered by the oxide phases at PO2 = 2×10−4 mbars up to a depth of 3 μm and the xenon is then completely released. For TiN samples, the results show a progressive apparition of oxide crystallites (Ti3O5 mainly) at the surface when PO2 increases. The presence of the oxide crystallites is also directly correlated with xenon release, the more oxide crystallites are growing the more xenon is released. TiN surface is completely covered by an oxide layer at PO2 = 2×10−4 mbars up to 1 μm. A correlation between the initial fine microstructure of TiN and the properties of the growing layer is suggested.
International Journal of Refractory Metals and Hard Materials, 2013
The oxidation behavior of several batches of TiC nanopowders and micropowders under air has been ... more The oxidation behavior of several batches of TiC nanopowders and micropowders under air has been studied. Using TGA, the oxidation of nanopowders is completed faster and at a lower temperature compared to micropowders. This is related to the higher specific surface area of the nanopowders. Using an amount of powder of about 41.6 mg through DTA, three different exothermic peaks were observed for both kinds of powders. Correlated to the in-situ temperature XRD diffractograms, these peaks were attributed to the following oxidation reactions: i) TiC → TiC x O 1 − x up to TiO, ii) → Ti 3 O 5 , and iii) → TiO 2. The same successive oxide phases for nanopowders and micropowders were observed, meaning that the oxidation mechanism is similar in both cases but with a shift of temperature. In this article, the role of the oxygen trapped in the powder and the effect of powder quantity on the oxidation kinetics and on the occurrence of one or three oxidation peaks are discussed.
International Journal of Refractory Metals and Hard Materials, 2005
Powders used for this study were synthesized by the self-propagating high temperature synthesis (... more Powders used for this study were synthesized by the self-propagating high temperature synthesis (SHS) process. This method allows producing titanium nitride powders in an economic and easy way. Densification of these original powders is carried out by the hot pressing process. Sintering is achieved, under a 50 MPa pressure, at different temperatures (1400°C, 1600°C and 1800°C). At 1600°C properties are optimised and bulk specimen density is superior to 98%. In addition, microhardness reaches the average value of 1790 ± 225 H V and Young modulus measured is 430 ± 10 GPa. A tribological characterization is then carried out with an adapted four balls machine tribometer. Titanium nitride tribological behavior is compared with the one of other hard materials such as 100C6 steel, titanium carbide and two cemented carbides of different compositions. Parameters such as toughness, hardness and wear volume are correlated in order to understand wear mechanisms origins.
International Journal of Refractory Metals and Hard Materials, 2005
In this paper, the TiC-based cermets with addition of TiN were fabricated by a conventional powde... more In this paper, the TiC-based cermets with addition of TiN were fabricated by a conventional powder metallurgy process. The titanium nitride (TiN) and titanium carbide (TiC) used as starting powders have been synthesized by the self-propagating high temperature synthesis (SHS) method. This exothermic reaction, easy to process, allows to obtain fine and original powders from lowcost raw materials. Cermets obtained by sintering powders of TiC and Mo 2 C with nickel binder phase are investigated. The effect of TiN adding on the microstructure and the mechanical properties of these composites are studied. Microstructures have been observed by scanning electron microscopy (SEM). Room temperature mechanical properties such as YoungÕs modulus, fracture toughness and microhardness have been measured and related to morphology and chemical composition of the samples. Tribological experiments were also performed and the friction coefficient of a cermet containing titanium nitride was compared with that of other hard materials. The SHS starting powders used present some particularities, as it was shown in a previous study [Matériaux à base de carbures et nitrures, pour coupe et usure, obtenus à partir de poudre SHS, PhD Thesis, INSA Lyon, 2004]. The purpose of this work is to show that results concerning the impact of TiN addition on microstructure and mechanical properties obtained on bulk specimens, from these original starting powders, are similar to the ones obtained on alloys from commercial starting powders.
Journal of Nuclear Materials, 2018
Nano-grained β-silicon carbide (β-SiC) pellets were prepared by Spark Plasma Sintering (SPS). The... more Nano-grained β-silicon carbide (β-SiC) pellets were prepared by Spark Plasma Sintering (SPS). These were implanted at room temperature with 800 keV xenon at ion fluences of 5.10 15 and 1.10 17 cm-2. Microstructural modifications were studied by electronic microscopy (TEM and SEM) and xenon profiles were determined by Rutherford Backscattering Spectroscopy (RBS). A complete amorphization of the implanted area associated with a significant oxidation is observed for the highest fluence. Large xenon bubbles formed in the oxide phase are responsible of surface swelling. No significant gas release has been measured up to 10 17 at.cm-2. A model is proposed to explain the different steps of the oxidation process and xenon bubbles formation as a function of ion fluence.
Materials (Basel, Switzerland), Jan 6, 2018
TiZrCuPd Bulk Metallic Glass (BMG) appears very attractive for future biomedical applications tha... more TiZrCuPd Bulk Metallic Glass (BMG) appears very attractive for future biomedical applications thanks to its high glass forming ability, the absence of toxic elements such as Ni, Al or Be and its good mechanical properties. For the first time, a complete and exhaustive characterization of a unique batch of this glassy alloy was performed, together with ISO standard mechanical tests on machined implant-abutment assemblies. The results were compared to the benchmark Ti-6Al-4V ELI (Extra-Low-Interstitial) to assess its potential in dental implantology. The thermal stability, corrosion and sterilization resistance, cytocompatibility and mechanical properties were measured on samples with a simple geometry, but also on implant-abutment assemblies' prototypes. Results show that the glassy alloy exhibits a quite high thermal stability, with a temperature range of 38 °C between the glass transition and crystallization, a compressive strength of 2 GPa, a certain plastic deformation (0.7%)...
Materials Science Forum, 2014
The gold alloys are used in jewelry for their aesthetic appearance and inertia to the environment... more The gold alloys are used in jewelry for their aesthetic appearance and inertia to the environment. In jewelry a hardness superior to 300 HV is desirable to facilitate the final machining and reduce the wear of the final product. The maximum hardness that can be obtained with the standard 18 carats gold (Au75-Ag12.5-Cu12.5 (wt%)) through a combination of heat treatment and cold working is about 290 HV. Gold-based bulk metallic glasses (BMGs) are an alternative as they present unique properties in comparison with crystalline counterparts, especially easy thermoplastic processing combined with a high hardness. Pd-base BMGs are another solution, due also to their attractive features.An Au49Cu26.9Si16.3Ag5.5Pd2.3 (% at.) and a Pd40Cu30Ni10P20 (% at.) bulk metallic glasses were fabricated by a copper mould suction casting technique in an argon atmosphere. In the as-cast state hardness, shear modulus and hardness are high (HV0.3= 360 and 530 in the Au-and Pd-base BMGs, respectively). Vario...
Nuclear Instruments and Methods in Physics Research Section B: Beam Interactions with Materials and Atoms, 2009
Titanium nitride has been proposed as a fission product barrier in fuel structures for gas cooled... more Titanium nitride has been proposed as a fission product barrier in fuel structures for gas cooled fast reactor (GFR) systems. The thermal migration of Cs was studied by implanting 800 keV 133 Cs ++ ions into sintered samples of TiN at an ion fluence of 5 Â 10 15 cm À2. Thermal treatments at temperatures ranging from 1500 to 1650°C were performed under a secondary vacuum. Concentration profiles were determined by 2.5 MeV 4 He + elastic backscattering. The results reveal that the global mobility of caesium in the host matrix is low compared to xenon and iodine implanted in the same conditions. Nevertheless, the evolution of caesium depth profile during thermal treatment presents similarities with that of xenon. Both species are homogeneously transported towards the surface and the transport rate increases with the temperature. In comparison, iodine exhibits singular migration behaviour. Several assumptions are proposed to explain the better retention of caesium in comparison with both other species. The potential role played by the oxidation is underlined since even a slight modification of the surface stoichiometry may modify species mobility. More generally, the apparition of square-like shapes on the surface of the samples after implantations and thermal treatments is discussed.
Thin Solid Films, 2014
ABSTRACT Bulk metallic glasses have attracted considerable attention over the last decades for th... more ABSTRACT Bulk metallic glasses have attracted considerable attention over the last decades for their outstanding mechanical features (high strength, super-elasticity) and physico-chemical properties (corrosion resistance). Recently, some attempts to assign such original behavior from bulk materials to modified surfaces have been reported in the literature based on multicomponent alloys. In this paper we focused on the opportunity to form a metallic glass coating from the binary Zr–Cu system using a magnetron co-sputtering physical vapor deposition process. The composition of the films can be easily controlled by the relative intensities applied to both pure targets, which made possible the study of the whole Zr–Cu system (from 13.4 to 85.0 at.% Cu). The chemical composition of the films was obtained by energy dispersive X-ray spectroscopy, and their microstructure was characterized by scanning and transmission electron microscopy. The thermal stability of the films was deduced from an in situ X-ray diffraction analysis (from room temperature up to 600 °C) and correlated with the results of the differential scanning calorimetry technique. Their mechanical properties were determined by nanoindentation experiments.
Nuclear Instruments and Methods in Physics Research Section B: Beam Interactions with Materials and Atoms, 2010
Micro-Rutherford backscattering spectrometry experiments were performed on a set of sintered tita... more Micro-Rutherford backscattering spectrometry experiments were performed on a set of sintered titanium nitride samples implanted with xenon to a depth of about 150 nm. Implanted samples were annealed at 1500°C during 5 h. Xe depth profile and its lateral distribution on the surface were measured. Surface morphology was observed using scanning electron microscopy. The results reveal that the microstructure plays an important role on xenon release. Moreover, the crystalline orientation of each grain could be a key parameter to explain the heterogeneous evolution of the surface during thermal treatments as well as Xe release from surface.
Journal of Thermal Analysis and Calorimetry, 2012
The free sintering of ceramic powders into fully dense nanostructured materials is still a challe... more The free sintering of ceramic powders into fully dense nanostructured materials is still a challenging process, even more complex when nanostructured transition alumina is used as starting powder. In this paper, biphasic (Alumina-YAG) and triphasic (Alumina-YAG-ZrO 2) composite powders were produced by doping the same nanocrystalline transition alumina with inorganic precursors of the second-phases, which were subsequently yielded under controlled thermal treatments. The added dopants significantly increased both the hto a-phase transformation and the sintering temperatures, making even more difficult the retention of the starting nanometric grain size into the final dense materials. Thermal analyses (such as TG-DTA and dilatometry) are here used to support most of the ceramic processing steps involved in a successful elaboration of the desired ultra-fine structures. In fact, the thermal pre-treatments of the doped powders were set up on the ground of the DTA-TG curves whereas the dilatometric analyses were exploited to design optimised sintering cycles, through which the green bodies were successfully consolidated into fully dense materials, characterised by highly homogeneous and tailored micro/ nanostructures.
Journal of the European Ceramic Society, 2007
Synthesis of titanium nitride (TiN) powders by the self propagating high temperature synthesis (S... more Synthesis of titanium nitride (TiN) powders by the self propagating high temperature synthesis (SHS) process is economically appealing. This chemical reaction allows producing fine grains powders with a high specific surface area (12m2/g). After a thermal treatment above 1000°C under argon atmosphere, the physical and microstructural characteristics of the powders are drastically modified: density increases and specific surface decreases. Powders
Journal of Nuclear Materials, 2008
Titanium nitride is one of the inert matrixes proposed to surround the fuel in gas cooled fast re... more Titanium nitride is one of the inert matrixes proposed to surround the fuel in gas cooled fast reactor (GFR) systems. These reactors will operate at high temperature and refractory materials with a high chemical stability and good mechanical properties are required. Furthermore, a total retention of the most volatile fission products, such as I, Xe or Cs, by the inert matrix is needed during the in-pile process. The isothermal migration of iodine in TiN was studied by implanting 800 keV I ++ ions in sintered samples at an ion fluence of 5 • 10 15 cm À2. Thermal treatments were performed under secondary vacuum at temperatures ranging from 1200 to 1700°C. Iodine concentration profiles were determined by 2.5 MeV a-particle elastic backscattering. The migration of iodine seems to be correlated with point defects created by implanted ions near the surface. The Arrhenius plot corresponding to iodine detrapping is curved with possibly two straight-line regions which could indicate either the presence of two types of traps, or a strong dependence of trap's concentration on temperature above 1500°C. The activation energies associated with each linear region of the Arrhenius plot were found to be: E a = 2.4 ± 0.2 eV below 1500°C and E a 0 ¼ 11:4 AE 0:2 eV above 1500°C. Nitrogen evaporation from TiN surface under secondary vacuum was proposed as a contributing factor to the enhanced mobility of iodine at high temperature.
Journal of Nuclear Materials, 2013
ABSTRACT Titanium nitride is a refractory material that is being considered as an inert matrix in... more ABSTRACT Titanium nitride is a refractory material that is being considered as an inert matrix in future Generation IV nuclear reactors, in particular in relation to the Gas-cooled Fast Reactor. The main role of this matrix would be to act as a barrier against the release of fission products, in particular gaseous ones like xenon. This release phenomenon will be enhanced by high temperatures expected in the fuel vicinity: 1200° C under normal conditions, and up to 1800° C under accidental conditions. It is therefore necessary to investigate the behaviour of volatile fission products in TiN under high temperature and irradiation. Indeed, these basic data are very useful to predict the volatile fission products released under these extreme conditions. Our previous work has shown that Xe introduced by ion implantation in sintered TiN tends to be released as a result of annealing, due to a transport mechanism towards the sample surface. The aim of the present work is to determine under which physical state Xe is in TiN. Xenon was first introduced using ion implantation at 800 keV in TiN samples obtained by hot pressing at several concentrations ranging from 0.4 to 8 at. %. Secondly, samples were annealed at high temperature, from 1000° C to 1500° C. Xe was then characterized by X-ray Absorption Spectroscopy and Transmission Electron Microscopy. The formation of intragranular xenon bubbles was demonstrated, and the xenon concentration which is sufficient to form bubbles is found to be lower than 0.4 at. % under our experimental conditions. These bubbles were found unpressurised at 15 K. Their size increases with the temperature and the local xenon concentration. For the highest xenon concentrations, a mechanism involving the formation of a Xe interconnected bubble network is proposed to explain Xe massive release observed by Rutherford Backscattering Spectrometry experiments.
Journal of Applied Physics, 2011
ABSTRACT Dense TiN and TiC samples were prepared by hot pressing using micrometric powders. Xenon... more ABSTRACT Dense TiN and TiC samples were prepared by hot pressing using micrometric powders. Xenon species (simulating rare gas fission products) were then implanted into the ceramics. The samples were annealed for 1 h at 1500 °C under several degraded vacuums with PO2 varying from 10−6 to 2×10−4 mbars. The oxidation resistance of the samples and their retention properties with respect to preimplanted xenon species were analyzed using scanning electron microscopy, grazing incidence x-ray diffraction, Rutherford backscattering spectrometry, and nuclear backscattering spectrometry. Results indicate that TiC is resistant to oxidation and does not release xenon for PO2 ≤ 6×10−6 mbars. When PO2 increases, geometric oxide crystallites appear at the surface depending on the orientation and size of TiC grains. These oxide phases are Ti2O3, Ti3O5, and TiO2. Apparition of oxide crystallites is associated with the beginning of xenon release. TiC surface is completely covered by the oxide phases at PO2 = 2×10−4 mbars up to a depth of 3 μm and the xenon is then completely released. For TiN samples, the results show a progressive apparition of oxide crystallites (Ti3O5 mainly) at the surface when PO2 increases. The presence of the oxide crystallites is also directly correlated with xenon release, the more oxide crystallites are growing the more xenon is released. TiN surface is completely covered by an oxide layer at PO2 = 2×10−4 mbars up to 1 μm. A correlation between the initial fine microstructure of TiN and the properties of the growing layer is suggested.
International Journal of Refractory Metals and Hard Materials, 2013
The oxidation behavior of several batches of TiC nanopowders and micropowders under air has been ... more The oxidation behavior of several batches of TiC nanopowders and micropowders under air has been studied. Using TGA, the oxidation of nanopowders is completed faster and at a lower temperature compared to micropowders. This is related to the higher specific surface area of the nanopowders. Using an amount of powder of about 41.6 mg through DTA, three different exothermic peaks were observed for both kinds of powders. Correlated to the in-situ temperature XRD diffractograms, these peaks were attributed to the following oxidation reactions: i) TiC → TiC x O 1 − x up to TiO, ii) → Ti 3 O 5 , and iii) → TiO 2. The same successive oxide phases for nanopowders and micropowders were observed, meaning that the oxidation mechanism is similar in both cases but with a shift of temperature. In this article, the role of the oxygen trapped in the powder and the effect of powder quantity on the oxidation kinetics and on the occurrence of one or three oxidation peaks are discussed.
International Journal of Refractory Metals and Hard Materials, 2005
Powders used for this study were synthesized by the self-propagating high temperature synthesis (... more Powders used for this study were synthesized by the self-propagating high temperature synthesis (SHS) process. This method allows producing titanium nitride powders in an economic and easy way. Densification of these original powders is carried out by the hot pressing process. Sintering is achieved, under a 50 MPa pressure, at different temperatures (1400°C, 1600°C and 1800°C). At 1600°C properties are optimised and bulk specimen density is superior to 98%. In addition, microhardness reaches the average value of 1790 ± 225 H V and Young modulus measured is 430 ± 10 GPa. A tribological characterization is then carried out with an adapted four balls machine tribometer. Titanium nitride tribological behavior is compared with the one of other hard materials such as 100C6 steel, titanium carbide and two cemented carbides of different compositions. Parameters such as toughness, hardness and wear volume are correlated in order to understand wear mechanisms origins.
International Journal of Refractory Metals and Hard Materials, 2005
In this paper, the TiC-based cermets with addition of TiN were fabricated by a conventional powde... more In this paper, the TiC-based cermets with addition of TiN were fabricated by a conventional powder metallurgy process. The titanium nitride (TiN) and titanium carbide (TiC) used as starting powders have been synthesized by the self-propagating high temperature synthesis (SHS) method. This exothermic reaction, easy to process, allows to obtain fine and original powders from lowcost raw materials. Cermets obtained by sintering powders of TiC and Mo 2 C with nickel binder phase are investigated. The effect of TiN adding on the microstructure and the mechanical properties of these composites are studied. Microstructures have been observed by scanning electron microscopy (SEM). Room temperature mechanical properties such as YoungÕs modulus, fracture toughness and microhardness have been measured and related to morphology and chemical composition of the samples. Tribological experiments were also performed and the friction coefficient of a cermet containing titanium nitride was compared with that of other hard materials. The SHS starting powders used present some particularities, as it was shown in a previous study [Matériaux à base de carbures et nitrures, pour coupe et usure, obtenus à partir de poudre SHS, PhD Thesis, INSA Lyon, 2004]. The purpose of this work is to show that results concerning the impact of TiN addition on microstructure and mechanical properties obtained on bulk specimens, from these original starting powders, are similar to the ones obtained on alloys from commercial starting powders.