Katia Cristiane Gandolpho Candioto - Academia.edu (original) (raw)

Papers by Katia Cristiane Gandolpho Candioto

Research paper thumbnail of Microstructural characterization of Nb–B–Si alloys with composition in the Nb−Nb 5Si 2B (T 2-phase) vertical section

Materials Characterization, 2001

Multiphase alloys of the Me -B -Si (Me = refractory metal) systems have been considered for struc... more Multiphase alloys of the Me -B -Si (Me = refractory metal) systems have been considered for structural applications at high temperatures. In this work, the solidification pathway and phase stability of Nb-rich Nb -B -Si alloys were evaluated from arc-melted and heat-treated samples. The primary phases observed in the region of study were Nb ss , T 2 -phase and D8 8 -phase. The as-cast microstructure of all the alloys indicates formation of an Nb ss + T 2 eutectic in the last part to solidify. From the heat treatment of several alloys, the Nb ss À T 2 two-phase field was observed to exist at 1700°C. Based on DTA experiments, the Nb ss À T 2 two-phase field should be stable up to 2150°C. D

Research paper thumbnail of Niobium hydrogenation process: Effect of temperature and cooling rate from the hydrogenation temperature

International Journal of Refractory Metals & Hard Materials, 2011

High-purity niobium powder can be produced via the hydrogenation and dehydrogenation processes. T... more High-purity niobium powder can be produced via the hydrogenation and dehydrogenation processes. The present work aimed at the effect of temperature and cooling rate conditions on the niobium hydrogenation process using hydrogen gas. The hydrogen contents of the materials were evaluated by weight change and chemical analysis. X-ray diffraction (XRD) was performed to identify and determine the lattice parameters of the formed hydride phases. No hydrogenation took place under isothermal conditions, only during cooling of the materials. Significant hydrogenation occurred in the 500°C and 700°C experiments, leading to the formation of a β-NbH x single-phase material.

Research paper thumbnail of Nb–20%Ta alloy powder by the hydriding–dehydriding technique

International Journal of Refractory Metals & Hard Materials, 2006

Nb-Ta alloys have been used in the chemical industry to substitute pure Ta in corrosive environme... more Nb-Ta alloys have been used in the chemical industry to substitute pure Ta in corrosive environments (inorganic acids at high temperature). The production of components from these alloys does not show important technical problems due to the high ductility of these materials. The present work is aimed at the production of Nb-20%Ta (wt%) alloy powders by the hydriding-dehydriding technique. The alloy was produced in ingot form by the aluminothermic reduction of oxides (Nb 2 O 5 /Ta 2 O 5 ) and electron beam melting. The hydriding step has been carried out in a hydrogen gas atmosphere at diVerent temperatures using chips machined from the ingot. No signiWcant hydriding has been observed in the experiments carried out below 500°C, meaning that it is the lowest possible hydriding temperature of the material through the adopted experimental procedure. The XRD patterns of the hydride and Nb-20%Ta powders coincide with those of -NbH 0.89 and Nb XRD standards, respectively. The powders were of angular and irregular morphology. The speciWc masses of the hydride and Nb-20%Ta powder were determined as approximately 8.55 and 9.57 g/cm 3 , respectively. The apparent and TAP speciWc masses of the hydride and Nb-20%Ta powders were (4.30/5.60) and (4.65/6.10) g/cm 3 , respectively.

Research paper thumbnail of Rapid solidification and phase stability evaluation of Ti–Si–B alloys

Journal of Alloys and Compounds, 2011

Ti-rich Ti-Si-B alloys can be considered for structural applications at high temperatures (max. 7... more Ti-rich Ti-Si-B alloys can be considered for structural applications at high temperatures (max. 700 • C), however, phase equilibria data is reported only for T = 1250 • C. Thus, in this work the phase stability of this system has been evaluated at 700 • C. In order to attain equilibrium conditions in shorter time, rapid solidified samples have been prepared and carefully characterized. The microstructural characterization of the produced materials were based on X-ray diffraction (XRD), scanning electron microscopy (SEM-BSE), high resolution transmission electron microscopy (HRTEM), High Temperature X-ray diffraction with Synchrotron radiation (XRDSR) and Differential Scanning Calorimetry (DSC). Amorphous and amorphous with embedded nanocrystals have been observed after rapid solidification from specific alloy compositions. The values of the crystallization temperature (Tx) of the alloys were in the 509-647 • C temperature range. After Differential Scanning Calorimetry and High Temperature X-ray Diffraction with Synchrotron radiation, the alloys showed crystalline and basically formed by two or three of the following phases: ␣Ti, Ti 6 Si 2 B; Ti 5 Si 3 ; Ti 3 Si and TiB. It has been shown the stability of the Ti 3 Si and Ti 6 Si 2 B phases at 700 • C and the proposition of an isothermal section at this temperature.

Research paper thumbnail of Microstructural characterization of Nb–B–Si alloys with composition in the Nb−Nb 5Si 2B (T 2-phase) vertical section

Materials Characterization, 2001

Multiphase alloys of the Me -B -Si (Me = refractory metal) systems have been considered for struc... more Multiphase alloys of the Me -B -Si (Me = refractory metal) systems have been considered for structural applications at high temperatures. In this work, the solidification pathway and phase stability of Nb-rich Nb -B -Si alloys were evaluated from arc-melted and heat-treated samples. The primary phases observed in the region of study were Nb ss , T 2 -phase and D8 8 -phase. The as-cast microstructure of all the alloys indicates formation of an Nb ss + T 2 eutectic in the last part to solidify. From the heat treatment of several alloys, the Nb ss À T 2 two-phase field was observed to exist at 1700°C. Based on DTA experiments, the Nb ss À T 2 two-phase field should be stable up to 2150°C. D

Research paper thumbnail of Niobium hydrogenation process: Effect of temperature and cooling rate from the hydrogenation temperature

International Journal of Refractory Metals & Hard Materials, 2011

High-purity niobium powder can be produced via the hydrogenation and dehydrogenation processes. T... more High-purity niobium powder can be produced via the hydrogenation and dehydrogenation processes. The present work aimed at the effect of temperature and cooling rate conditions on the niobium hydrogenation process using hydrogen gas. The hydrogen contents of the materials were evaluated by weight change and chemical analysis. X-ray diffraction (XRD) was performed to identify and determine the lattice parameters of the formed hydride phases. No hydrogenation took place under isothermal conditions, only during cooling of the materials. Significant hydrogenation occurred in the 500°C and 700°C experiments, leading to the formation of a β-NbH x single-phase material.

Research paper thumbnail of Nb–20%Ta alloy powder by the hydriding–dehydriding technique

International Journal of Refractory Metals & Hard Materials, 2006

Nb-Ta alloys have been used in the chemical industry to substitute pure Ta in corrosive environme... more Nb-Ta alloys have been used in the chemical industry to substitute pure Ta in corrosive environments (inorganic acids at high temperature). The production of components from these alloys does not show important technical problems due to the high ductility of these materials. The present work is aimed at the production of Nb-20%Ta (wt%) alloy powders by the hydriding-dehydriding technique. The alloy was produced in ingot form by the aluminothermic reduction of oxides (Nb 2 O 5 /Ta 2 O 5 ) and electron beam melting. The hydriding step has been carried out in a hydrogen gas atmosphere at diVerent temperatures using chips machined from the ingot. No signiWcant hydriding has been observed in the experiments carried out below 500°C, meaning that it is the lowest possible hydriding temperature of the material through the adopted experimental procedure. The XRD patterns of the hydride and Nb-20%Ta powders coincide with those of -NbH 0.89 and Nb XRD standards, respectively. The powders were of angular and irregular morphology. The speciWc masses of the hydride and Nb-20%Ta powder were determined as approximately 8.55 and 9.57 g/cm 3 , respectively. The apparent and TAP speciWc masses of the hydride and Nb-20%Ta powders were (4.30/5.60) and (4.65/6.10) g/cm 3 , respectively.

Research paper thumbnail of Rapid solidification and phase stability evaluation of Ti–Si–B alloys

Journal of Alloys and Compounds, 2011

Ti-rich Ti-Si-B alloys can be considered for structural applications at high temperatures (max. 7... more Ti-rich Ti-Si-B alloys can be considered for structural applications at high temperatures (max. 700 • C), however, phase equilibria data is reported only for T = 1250 • C. Thus, in this work the phase stability of this system has been evaluated at 700 • C. In order to attain equilibrium conditions in shorter time, rapid solidified samples have been prepared and carefully characterized. The microstructural characterization of the produced materials were based on X-ray diffraction (XRD), scanning electron microscopy (SEM-BSE), high resolution transmission electron microscopy (HRTEM), High Temperature X-ray diffraction with Synchrotron radiation (XRDSR) and Differential Scanning Calorimetry (DSC). Amorphous and amorphous with embedded nanocrystals have been observed after rapid solidification from specific alloy compositions. The values of the crystallization temperature (Tx) of the alloys were in the 509-647 • C temperature range. After Differential Scanning Calorimetry and High Temperature X-ray Diffraction with Synchrotron radiation, the alloys showed crystalline and basically formed by two or three of the following phases: ␣Ti, Ti 6 Si 2 B; Ti 5 Si 3 ; Ti 3 Si and TiB. It has been shown the stability of the Ti 3 Si and Ti 6 Si 2 B phases at 700 • C and the proposition of an isothermal section at this temperature.

Research paper thumbnail of Microstructural characterization of Nb–B–Si alloys with composition in the Nb−Nb 5Si 2B (T 2-phase) vertical section

Materials Characterization, 2001

Multiphase alloys of the Me -B -Si (Me = refractory metal) systems have been considered for struc... more Multiphase alloys of the Me -B -Si (Me = refractory metal) systems have been considered for structural applications at high temperatures. In this work, the solidification pathway and phase stability of Nb-rich Nb -B -Si alloys were evaluated from arc-melted and heat-treated samples. The primary phases observed in the region of study were Nb ss , T 2 -phase and D8 8 -phase. The as-cast microstructure of all the alloys indicates formation of an Nb ss + T 2 eutectic in the last part to solidify. From the heat treatment of several alloys, the Nb ss À T 2 two-phase field was observed to exist at 1700°C. Based on DTA experiments, the Nb ss À T 2 two-phase field should be stable up to 2150°C. D

Research paper thumbnail of Niobium hydrogenation process: Effect of temperature and cooling rate from the hydrogenation temperature

International Journal of Refractory Metals & Hard Materials, 2011

High-purity niobium powder can be produced via the hydrogenation and dehydrogenation processes. T... more High-purity niobium powder can be produced via the hydrogenation and dehydrogenation processes. The present work aimed at the effect of temperature and cooling rate conditions on the niobium hydrogenation process using hydrogen gas. The hydrogen contents of the materials were evaluated by weight change and chemical analysis. X-ray diffraction (XRD) was performed to identify and determine the lattice parameters of the formed hydride phases. No hydrogenation took place under isothermal conditions, only during cooling of the materials. Significant hydrogenation occurred in the 500°C and 700°C experiments, leading to the formation of a β-NbH x single-phase material.

Research paper thumbnail of Nb–20%Ta alloy powder by the hydriding–dehydriding technique

International Journal of Refractory Metals & Hard Materials, 2006

Nb-Ta alloys have been used in the chemical industry to substitute pure Ta in corrosive environme... more Nb-Ta alloys have been used in the chemical industry to substitute pure Ta in corrosive environments (inorganic acids at high temperature). The production of components from these alloys does not show important technical problems due to the high ductility of these materials. The present work is aimed at the production of Nb-20%Ta (wt%) alloy powders by the hydriding-dehydriding technique. The alloy was produced in ingot form by the aluminothermic reduction of oxides (Nb 2 O 5 /Ta 2 O 5 ) and electron beam melting. The hydriding step has been carried out in a hydrogen gas atmosphere at diVerent temperatures using chips machined from the ingot. No signiWcant hydriding has been observed in the experiments carried out below 500°C, meaning that it is the lowest possible hydriding temperature of the material through the adopted experimental procedure. The XRD patterns of the hydride and Nb-20%Ta powders coincide with those of -NbH 0.89 and Nb XRD standards, respectively. The powders were of angular and irregular morphology. The speciWc masses of the hydride and Nb-20%Ta powder were determined as approximately 8.55 and 9.57 g/cm 3 , respectively. The apparent and TAP speciWc masses of the hydride and Nb-20%Ta powders were (4.30/5.60) and (4.65/6.10) g/cm 3 , respectively.

Research paper thumbnail of Rapid solidification and phase stability evaluation of Ti–Si–B alloys

Journal of Alloys and Compounds, 2011

Ti-rich Ti-Si-B alloys can be considered for structural applications at high temperatures (max. 7... more Ti-rich Ti-Si-B alloys can be considered for structural applications at high temperatures (max. 700 • C), however, phase equilibria data is reported only for T = 1250 • C. Thus, in this work the phase stability of this system has been evaluated at 700 • C. In order to attain equilibrium conditions in shorter time, rapid solidified samples have been prepared and carefully characterized. The microstructural characterization of the produced materials were based on X-ray diffraction (XRD), scanning electron microscopy (SEM-BSE), high resolution transmission electron microscopy (HRTEM), High Temperature X-ray diffraction with Synchrotron radiation (XRDSR) and Differential Scanning Calorimetry (DSC). Amorphous and amorphous with embedded nanocrystals have been observed after rapid solidification from specific alloy compositions. The values of the crystallization temperature (Tx) of the alloys were in the 509-647 • C temperature range. After Differential Scanning Calorimetry and High Temperature X-ray Diffraction with Synchrotron radiation, the alloys showed crystalline and basically formed by two or three of the following phases: ␣Ti, Ti 6 Si 2 B; Ti 5 Si 3 ; Ti 3 Si and TiB. It has been shown the stability of the Ti 3 Si and Ti 6 Si 2 B phases at 700 • C and the proposition of an isothermal section at this temperature.

Research paper thumbnail of Microstructural characterization of Nb–B–Si alloys with composition in the Nb−Nb 5Si 2B (T 2-phase) vertical section

Materials Characterization, 2001

Multiphase alloys of the Me -B -Si (Me = refractory metal) systems have been considered for struc... more Multiphase alloys of the Me -B -Si (Me = refractory metal) systems have been considered for structural applications at high temperatures. In this work, the solidification pathway and phase stability of Nb-rich Nb -B -Si alloys were evaluated from arc-melted and heat-treated samples. The primary phases observed in the region of study were Nb ss , T 2 -phase and D8 8 -phase. The as-cast microstructure of all the alloys indicates formation of an Nb ss + T 2 eutectic in the last part to solidify. From the heat treatment of several alloys, the Nb ss À T 2 two-phase field was observed to exist at 1700°C. Based on DTA experiments, the Nb ss À T 2 two-phase field should be stable up to 2150°C. D

Research paper thumbnail of Niobium hydrogenation process: Effect of temperature and cooling rate from the hydrogenation temperature

International Journal of Refractory Metals & Hard Materials, 2011

High-purity niobium powder can be produced via the hydrogenation and dehydrogenation processes. T... more High-purity niobium powder can be produced via the hydrogenation and dehydrogenation processes. The present work aimed at the effect of temperature and cooling rate conditions on the niobium hydrogenation process using hydrogen gas. The hydrogen contents of the materials were evaluated by weight change and chemical analysis. X-ray diffraction (XRD) was performed to identify and determine the lattice parameters of the formed hydride phases. No hydrogenation took place under isothermal conditions, only during cooling of the materials. Significant hydrogenation occurred in the 500°C and 700°C experiments, leading to the formation of a β-NbH x single-phase material.

Research paper thumbnail of Nb–20%Ta alloy powder by the hydriding–dehydriding technique

International Journal of Refractory Metals & Hard Materials, 2006

Nb-Ta alloys have been used in the chemical industry to substitute pure Ta in corrosive environme... more Nb-Ta alloys have been used in the chemical industry to substitute pure Ta in corrosive environments (inorganic acids at high temperature). The production of components from these alloys does not show important technical problems due to the high ductility of these materials. The present work is aimed at the production of Nb-20%Ta (wt%) alloy powders by the hydriding-dehydriding technique. The alloy was produced in ingot form by the aluminothermic reduction of oxides (Nb 2 O 5 /Ta 2 O 5 ) and electron beam melting. The hydriding step has been carried out in a hydrogen gas atmosphere at diVerent temperatures using chips machined from the ingot. No signiWcant hydriding has been observed in the experiments carried out below 500°C, meaning that it is the lowest possible hydriding temperature of the material through the adopted experimental procedure. The XRD patterns of the hydride and Nb-20%Ta powders coincide with those of -NbH 0.89 and Nb XRD standards, respectively. The powders were of angular and irregular morphology. The speciWc masses of the hydride and Nb-20%Ta powder were determined as approximately 8.55 and 9.57 g/cm 3 , respectively. The apparent and TAP speciWc masses of the hydride and Nb-20%Ta powders were (4.30/5.60) and (4.65/6.10) g/cm 3 , respectively.

Research paper thumbnail of Rapid solidification and phase stability evaluation of Ti–Si–B alloys

Journal of Alloys and Compounds, 2011

Ti-rich Ti-Si-B alloys can be considered for structural applications at high temperatures (max. 7... more Ti-rich Ti-Si-B alloys can be considered for structural applications at high temperatures (max. 700 • C), however, phase equilibria data is reported only for T = 1250 • C. Thus, in this work the phase stability of this system has been evaluated at 700 • C. In order to attain equilibrium conditions in shorter time, rapid solidified samples have been prepared and carefully characterized. The microstructural characterization of the produced materials were based on X-ray diffraction (XRD), scanning electron microscopy (SEM-BSE), high resolution transmission electron microscopy (HRTEM), High Temperature X-ray diffraction with Synchrotron radiation (XRDSR) and Differential Scanning Calorimetry (DSC). Amorphous and amorphous with embedded nanocrystals have been observed after rapid solidification from specific alloy compositions. The values of the crystallization temperature (Tx) of the alloys were in the 509-647 • C temperature range. After Differential Scanning Calorimetry and High Temperature X-ray Diffraction with Synchrotron radiation, the alloys showed crystalline and basically formed by two or three of the following phases: ␣Ti, Ti 6 Si 2 B; Ti 5 Si 3 ; Ti 3 Si and TiB. It has been shown the stability of the Ti 3 Si and Ti 6 Si 2 B phases at 700 • C and the proposition of an isothermal section at this temperature.

Research paper thumbnail of Microstructural characterization of Nb–B–Si alloys with composition in the Nb−Nb 5Si 2B (T 2-phase) vertical section

Materials Characterization, 2001

Multiphase alloys of the Me -B -Si (Me = refractory metal) systems have been considered for struc... more Multiphase alloys of the Me -B -Si (Me = refractory metal) systems have been considered for structural applications at high temperatures. In this work, the solidification pathway and phase stability of Nb-rich Nb -B -Si alloys were evaluated from arc-melted and heat-treated samples. The primary phases observed in the region of study were Nb ss , T 2 -phase and D8 8 -phase. The as-cast microstructure of all the alloys indicates formation of an Nb ss + T 2 eutectic in the last part to solidify. From the heat treatment of several alloys, the Nb ss À T 2 two-phase field was observed to exist at 1700°C. Based on DTA experiments, the Nb ss À T 2 two-phase field should be stable up to 2150°C. D

Research paper thumbnail of Niobium hydrogenation process: Effect of temperature and cooling rate from the hydrogenation temperature

International Journal of Refractory Metals & Hard Materials, 2011

High-purity niobium powder can be produced via the hydrogenation and dehydrogenation processes. T... more High-purity niobium powder can be produced via the hydrogenation and dehydrogenation processes. The present work aimed at the effect of temperature and cooling rate conditions on the niobium hydrogenation process using hydrogen gas. The hydrogen contents of the materials were evaluated by weight change and chemical analysis. X-ray diffraction (XRD) was performed to identify and determine the lattice parameters of the formed hydride phases. No hydrogenation took place under isothermal conditions, only during cooling of the materials. Significant hydrogenation occurred in the 500°C and 700°C experiments, leading to the formation of a β-NbH x single-phase material.

Research paper thumbnail of Nb–20%Ta alloy powder by the hydriding–dehydriding technique

International Journal of Refractory Metals & Hard Materials, 2006

Nb-Ta alloys have been used in the chemical industry to substitute pure Ta in corrosive environme... more Nb-Ta alloys have been used in the chemical industry to substitute pure Ta in corrosive environments (inorganic acids at high temperature). The production of components from these alloys does not show important technical problems due to the high ductility of these materials. The present work is aimed at the production of Nb-20%Ta (wt%) alloy powders by the hydriding-dehydriding technique. The alloy was produced in ingot form by the aluminothermic reduction of oxides (Nb 2 O 5 /Ta 2 O 5 ) and electron beam melting. The hydriding step has been carried out in a hydrogen gas atmosphere at diVerent temperatures using chips machined from the ingot. No signiWcant hydriding has been observed in the experiments carried out below 500°C, meaning that it is the lowest possible hydriding temperature of the material through the adopted experimental procedure. The XRD patterns of the hydride and Nb-20%Ta powders coincide with those of -NbH 0.89 and Nb XRD standards, respectively. The powders were of angular and irregular morphology. The speciWc masses of the hydride and Nb-20%Ta powder were determined as approximately 8.55 and 9.57 g/cm 3 , respectively. The apparent and TAP speciWc masses of the hydride and Nb-20%Ta powders were (4.30/5.60) and (4.65/6.10) g/cm 3 , respectively.

Research paper thumbnail of Rapid solidification and phase stability evaluation of Ti–Si–B alloys

Journal of Alloys and Compounds, 2011

Ti-rich Ti-Si-B alloys can be considered for structural applications at high temperatures (max. 7... more Ti-rich Ti-Si-B alloys can be considered for structural applications at high temperatures (max. 700 • C), however, phase equilibria data is reported only for T = 1250 • C. Thus, in this work the phase stability of this system has been evaluated at 700 • C. In order to attain equilibrium conditions in shorter time, rapid solidified samples have been prepared and carefully characterized. The microstructural characterization of the produced materials were based on X-ray diffraction (XRD), scanning electron microscopy (SEM-BSE), high resolution transmission electron microscopy (HRTEM), High Temperature X-ray diffraction with Synchrotron radiation (XRDSR) and Differential Scanning Calorimetry (DSC). Amorphous and amorphous with embedded nanocrystals have been observed after rapid solidification from specific alloy compositions. The values of the crystallization temperature (Tx) of the alloys were in the 509-647 • C temperature range. After Differential Scanning Calorimetry and High Temperature X-ray Diffraction with Synchrotron radiation, the alloys showed crystalline and basically formed by two or three of the following phases: ␣Ti, Ti 6 Si 2 B; Ti 5 Si 3 ; Ti 3 Si and TiB. It has been shown the stability of the Ti 3 Si and Ti 6 Si 2 B phases at 700 • C and the proposition of an isothermal section at this temperature.

Research paper thumbnail of Microstructural characterization of Nb–B–Si alloys with composition in the Nb−Nb 5Si 2B (T 2-phase) vertical section

Materials Characterization, 2001

Multiphase alloys of the Me -B -Si (Me = refractory metal) systems have been considered for struc... more Multiphase alloys of the Me -B -Si (Me = refractory metal) systems have been considered for structural applications at high temperatures. In this work, the solidification pathway and phase stability of Nb-rich Nb -B -Si alloys were evaluated from arc-melted and heat-treated samples. The primary phases observed in the region of study were Nb ss , T 2 -phase and D8 8 -phase. The as-cast microstructure of all the alloys indicates formation of an Nb ss + T 2 eutectic in the last part to solidify. From the heat treatment of several alloys, the Nb ss À T 2 two-phase field was observed to exist at 1700°C. Based on DTA experiments, the Nb ss À T 2 two-phase field should be stable up to 2150°C. D

Research paper thumbnail of Niobium hydrogenation process: Effect of temperature and cooling rate from the hydrogenation temperature

International Journal of Refractory Metals & Hard Materials, 2011

High-purity niobium powder can be produced via the hydrogenation and dehydrogenation processes. T... more High-purity niobium powder can be produced via the hydrogenation and dehydrogenation processes. The present work aimed at the effect of temperature and cooling rate conditions on the niobium hydrogenation process using hydrogen gas. The hydrogen contents of the materials were evaluated by weight change and chemical analysis. X-ray diffraction (XRD) was performed to identify and determine the lattice parameters of the formed hydride phases. No hydrogenation took place under isothermal conditions, only during cooling of the materials. Significant hydrogenation occurred in the 500°C and 700°C experiments, leading to the formation of a β-NbH x single-phase material.

Research paper thumbnail of Nb–20%Ta alloy powder by the hydriding–dehydriding technique

International Journal of Refractory Metals & Hard Materials, 2006

Nb-Ta alloys have been used in the chemical industry to substitute pure Ta in corrosive environme... more Nb-Ta alloys have been used in the chemical industry to substitute pure Ta in corrosive environments (inorganic acids at high temperature). The production of components from these alloys does not show important technical problems due to the high ductility of these materials. The present work is aimed at the production of Nb-20%Ta (wt%) alloy powders by the hydriding-dehydriding technique. The alloy was produced in ingot form by the aluminothermic reduction of oxides (Nb 2 O 5 /Ta 2 O 5 ) and electron beam melting. The hydriding step has been carried out in a hydrogen gas atmosphere at diVerent temperatures using chips machined from the ingot. No signiWcant hydriding has been observed in the experiments carried out below 500°C, meaning that it is the lowest possible hydriding temperature of the material through the adopted experimental procedure. The XRD patterns of the hydride and Nb-20%Ta powders coincide with those of -NbH 0.89 and Nb XRD standards, respectively. The powders were of angular and irregular morphology. The speciWc masses of the hydride and Nb-20%Ta powder were determined as approximately 8.55 and 9.57 g/cm 3 , respectively. The apparent and TAP speciWc masses of the hydride and Nb-20%Ta powders were (4.30/5.60) and (4.65/6.10) g/cm 3 , respectively.

Research paper thumbnail of Rapid solidification and phase stability evaluation of Ti–Si–B alloys

Journal of Alloys and Compounds, 2011

Ti-rich Ti-Si-B alloys can be considered for structural applications at high temperatures (max. 7... more Ti-rich Ti-Si-B alloys can be considered for structural applications at high temperatures (max. 700 • C), however, phase equilibria data is reported only for T = 1250 • C. Thus, in this work the phase stability of this system has been evaluated at 700 • C. In order to attain equilibrium conditions in shorter time, rapid solidified samples have been prepared and carefully characterized. The microstructural characterization of the produced materials were based on X-ray diffraction (XRD), scanning electron microscopy (SEM-BSE), high resolution transmission electron microscopy (HRTEM), High Temperature X-ray diffraction with Synchrotron radiation (XRDSR) and Differential Scanning Calorimetry (DSC). Amorphous and amorphous with embedded nanocrystals have been observed after rapid solidification from specific alloy compositions. The values of the crystallization temperature (Tx) of the alloys were in the 509-647 • C temperature range. After Differential Scanning Calorimetry and High Temperature X-ray Diffraction with Synchrotron radiation, the alloys showed crystalline and basically formed by two or three of the following phases: ␣Ti, Ti 6 Si 2 B; Ti 5 Si 3 ; Ti 3 Si and TiB. It has been shown the stability of the Ti 3 Si and Ti 6 Si 2 B phases at 700 • C and the proposition of an isothermal section at this temperature.