5 research outputs found
Production of Metallic Titanium by Electrowinning in Molten Salts of Titanium Oxycarbide Anode
The electrochemical behavior of Ti3+ in LiCl-LiF-TiF3 salt was investigated by cyclic and square wave voltammetries at 853 K. Both methods confirm the presence of a single reduction wave of Ti3+ ions to metal, at a potential of −2.3 V vs. Cl2/Cl−. The closeness of the potentials of TiCxOy dissolution and Ti3+/Ti4+ wave is an issue during the electrorefining of the anode. A low current density has to be applied to stay within the titanium oxycarbide dissolution and avoid the formation of Ti4+. The titanium deposition was studied by electrorefining of a titanium metal plate in LiCl-LiF-TiF3 (0.62 mol/kg). The cathodic deposit analysis by XRD and SEM confirms the formation of titanium metal with an average grain size of 150 µm. The faradic deposition yields are above 85% and constant between 60 and 160 mA/cm2
Etude de l'Ă©lectro-raffinage de l'oxycarbure de titane dans milieu sel fondu
This work is devoted to the study of electrowinning of a titanium oxycarbide anode in a molten salt. Two parts have been studied: the synthesis of the TiC0,5O0,5 anode and the development of an electrolytic process. The anode material was synthesized by carbothermal reduction of TiO2 at different temperatures. The optimal conditions to reach a pure and single-phase composition of TiC0,5O0,5 are: carboreduction of TiO2 at 1500 °C for 4 hours followed by an annealing treatment identical to the first one. The elaboration of titanium in molten salt is delicate because of the existence of multiple oxidation degrees in solution (Ti4+, Ti3+, Ti2+and Ti0), leading to the formation of mediamutation reactions and the fall of faradic yields. The challenge was therefore to adapt the salt composition to stabilize the Ti3+ oxidation state. Analytical chemistry studies were performed in two chloro-fluoride medium with different F/Ti ratios. It was shown that using an electrolyte with a high F/Ti ratio (in this case, F/Ti = 87; LiCl-KCl-K2TiF6) maximizes the presence of Ti3+ and minimizes the existence of Ti2+, thus obtaining better faradic yields. Titanium oxycarbide has a high anodic dissolution potential close to the potential of the Ti3+/Ti4+ couple. Therefore, it is important to apply a low current density during the electrowinning of TiC0,5O0,5 to avoid C and O contamination of the titanium produced. The evaluation of the purity of titanium revealed a low carbon and high oxygen content. However, it has been shown that the oxygen present in the deposits does not come from the anode material but rather from contamination by oxides and/or oxychlorides that may exist in the molten salt, or from the cleaning step of the deposit with water that may cause its oxidation.Ce travail a pour objectif dâĂ©tudier un procĂ©dĂ© Ă©lectrolytique dâĂ©laboration du titane mĂ©tallique par Ă©lectro-raffinage dans un sel fondu dâune anode en oxycarbure de titane. Ce travail comporte deux parties : la synthĂšse du matĂ©riau TiC0,5O0,5 et la mise au point dâun procĂ©dĂ© Ă©lectrolytique. Le matĂ©riau dâanode (oxycarbure de titane) a Ă©tĂ© synthĂ©tisĂ© par rĂ©duction carbothermique de TiO2 Ă diffĂ©rentes tempĂ©ratures. Les conditions optimales pour atteindre une composition pure et monophasĂ©e de TiC0,5O0,5 sont : carborĂ©duction de TiO2 Ă 1500 °C pendant 4 h suivie dâun traitement de recuit identique au premier. LâĂ©laboration du titane en milieu sel fondu est dĂ©licate en raison de lâexistence de multiples degrĂ©s dâoxydation en solution (Ti4+, Ti3+, Ti2+ et Ti0), entrainant la formation de rĂ©actions de mĂ©diamutation et la chute des rendements faradiques. Lâenjeu Ă©tait donc dâadapter la composition saline pour stabiliser le degrĂ© dâoxydation Ti3+ . Des Ă©tudes de chimie analytique ont Ă©tĂ© rĂ©alisĂ©es dans deux milieux chloro-fluorĂ©s avec diffĂ©rents rapports F/Ti. Il a Ă©tĂ© dĂ©montrĂ© que lâutilisation dâun Ă©lectrolyte avec un rapport F/Ti Ă©levĂ© (dans ce cas, F/Ti = 87 ; LiCl-LiF-K2TiF6) permet de maximiser la prĂ©sence de Ti3+ et minimiser lâexistence de Ti2+, et obtenir ainsi de meilleurs rendements faradiques. Lâoxycarbure de titane a un potentiel de dissolution anodique Ă©levĂ© proche du potentiel du couple Ti3+/Ti4+. Il est donc important dâappliquer une faible densitĂ© de courant lors de lâĂ©lectrodissolution de TiC0,5O0,5 pour Ă©viter la formation dâions Ti4+ et la chute des rendements faradiques. Lâutilisation dâune faible densitĂ© de courant a Ă©galement permis de favoriser la production de CO et de limiter celle de CO2, lors de lâĂ©lectro-raffinage de TiC0,5O0,5, pour Ă©viter la contamination en C et O du titane produit. LâĂ©valuation de la puretĂ© des dĂ©pĂŽts de titane a rĂ©vĂ©lĂ© une faible teneur en carbone et une forte teneur en oxygĂšne. NĂ©anmoins, il a Ă©tĂ© dĂ©montrĂ© que lâoxygĂšne prĂ©sent dans les dĂ©pĂŽts ne provient pas du matĂ©riau dâanode mais plutĂŽt dâune contamination par les oxydes et/ou oxychlorures pouvant exister dans lâĂ©lectrolyte fondu, ou de lâĂ©tape de nettoyage du dĂ©pĂŽt Ă lâeau pouvant provoquer son oxydation
Etude de l'Ă©lectro-raffinage de l'oxycarbure de titane dans milieu sel fondu
This work is devoted to the study of electrowinning of a titanium oxycarbide anode in a molten salt. Two parts have been studied: the synthesis of the TiC0,5O0,5 anode and the development of an electrolytic process. The anode material was synthesized by carbothermal reduction of TiO2 at different temperatures. The optimal conditions to reach a pure and single-phase composition of TiC0,5O0,5 are: carboreduction of TiO2 at 1500 °C for 4 hours followed by an annealing treatment identical to the first one. The elaboration of titanium in molten salt is delicate because of the existence of multiple oxidation degrees in solution (Ti4+, Ti3+, Ti2+and Ti0), leading to the formation of mediamutation reactions and the fall of faradic yields. The challenge was therefore to adapt the salt composition to stabilize the Ti3+ oxidation state. Analytical chemistry studies were performed in two chloro-fluoride medium with different F/Ti ratios. It was shown that using an electrolyte with a high F/Ti ratio (in this case, F/Ti = 87; LiCl-KCl-K2TiF6) maximizes the presence of Ti3+ and minimizes the existence of Ti2+, thus obtaining better faradic yields. Titanium oxycarbide has a high anodic dissolution potential close to the potential of the Ti3+/Ti4+ couple. Therefore, it is important to apply a low current density during the electrowinning of TiC0,5O0,5 to avoid C and O contamination of the titanium produced. The evaluation of the purity of titanium revealed a low carbon and high oxygen content. However, it has been shown that the oxygen present in the deposits does not come from the anode material but rather from contamination by oxides and/or oxychlorides that may exist in the molten salt, or from the cleaning step of the deposit with water that may cause its oxidation.Ce travail a pour objectif dâĂ©tudier un procĂ©dĂ© Ă©lectrolytique dâĂ©laboration du titane mĂ©tallique par Ă©lectro-raffinage dans un sel fondu dâune anode en oxycarbure de titane. Ce travail comporte deux parties : la synthĂšse du matĂ©riau TiC0,5O0,5 et la mise au point dâun procĂ©dĂ© Ă©lectrolytique. Le matĂ©riau dâanode (oxycarbure de titane) a Ă©tĂ© synthĂ©tisĂ© par rĂ©duction carbothermique de TiO2 Ă diffĂ©rentes tempĂ©ratures. Les conditions optimales pour atteindre une composition pure et monophasĂ©e de TiC0,5O0,5 sont : carborĂ©duction de TiO2 Ă 1500 °C pendant 4 h suivie dâun traitement de recuit identique au premier. LâĂ©laboration du titane en milieu sel fondu est dĂ©licate en raison de lâexistence de multiples degrĂ©s dâoxydation en solution (Ti4+, Ti3+, Ti2+ et Ti0), entrainant la formation de rĂ©actions de mĂ©diamutation et la chute des rendements faradiques. Lâenjeu Ă©tait donc dâadapter la composition saline pour stabiliser le degrĂ© dâoxydation Ti3+ . Des Ă©tudes de chimie analytique ont Ă©tĂ© rĂ©alisĂ©es dans deux milieux chloro-fluorĂ©s avec diffĂ©rents rapports F/Ti. Il a Ă©tĂ© dĂ©montrĂ© que lâutilisation dâun Ă©lectrolyte avec un rapport F/Ti Ă©levĂ© (dans ce cas, F/Ti = 87 ; LiCl-LiF-K2TiF6) permet de maximiser la prĂ©sence de Ti3+ et minimiser lâexistence de Ti2+, et obtenir ainsi de meilleurs rendements faradiques. Lâoxycarbure de titane a un potentiel de dissolution anodique Ă©levĂ© proche du potentiel du couple Ti3+/Ti4+. Il est donc important dâappliquer une faible densitĂ© de courant lors de lâĂ©lectrodissolution de TiC0,5O0,5 pour Ă©viter la formation dâions Ti4+ et la chute des rendements faradiques. Lâutilisation dâune faible densitĂ© de courant a Ă©galement permis de favoriser la production de CO et de limiter celle de CO2, lors de lâĂ©lectro-raffinage de TiC0,5O0,5, pour Ă©viter la contamination en C et O du titane produit. LâĂ©valuation de la puretĂ© des dĂ©pĂŽts de titane a rĂ©vĂ©lĂ© une faible teneur en carbone et une forte teneur en oxygĂšne. NĂ©anmoins, il a Ă©tĂ© dĂ©montrĂ© que lâoxygĂšne prĂ©sent dans les dĂ©pĂŽts ne provient pas du matĂ©riau dâanode mais plutĂŽt dâune contamination par les oxydes et/ou oxychlorures pouvant exister dans lâĂ©lectrolyte fondu, ou de lâĂ©tape de nettoyage du dĂ©pĂŽt Ă lâeau pouvant provoquer son oxydation
Study of the electro-refining of titanium oxycarbide in a molten salt medium
Ce travail a pour objectif dâĂ©tudier un procĂ©dĂ© Ă©lectrolytique dâĂ©laboration du titane mĂ©tallique par Ă©lectro-raffinage dans un sel fondu dâune anode en oxycarbure de titane. Ce travail comporte deux parties : la synthĂšse du matĂ©riau TiC0,5O0,5 et la mise au point dâun procĂ©dĂ© Ă©lectrolytique. Le matĂ©riau dâanode (oxycarbure de titane) a Ă©tĂ© synthĂ©tisĂ© par rĂ©duction carbothermique de TiO2 Ă diffĂ©rentes tempĂ©ratures. Les conditions optimales pour atteindre une composition pure et monophasĂ©e de TiC0,5O0,5 sont : carborĂ©duction de TiO2 Ă 1500 °C pendant 4 h suivie dâun traitement de recuit identique au premier. LâĂ©laboration du titane en milieu sel fondu est dĂ©licate en raison de lâexistence de multiples degrĂ©s dâoxydation en solution (Ti4+, Ti3+, Ti2+ et Ti0), entrainant la formation de rĂ©actions de mĂ©diamutation et la chute des rendements faradiques. Lâenjeu Ă©tait donc dâadapter la composition saline pour stabiliser le degrĂ© dâoxydation Ti3+ . Des Ă©tudes de chimie analytique ont Ă©tĂ© rĂ©alisĂ©es dans deux milieux chloro-fluorĂ©s avec diffĂ©rents rapports F/Ti. Il a Ă©tĂ© dĂ©montrĂ© que lâutilisation dâun Ă©lectrolyte avec un rapport F/Ti Ă©levĂ© (dans ce cas, F/Ti = 87 ; LiCl-LiF-K2TiF6) permet de maximiser la prĂ©sence de Ti3+ et minimiser lâexistence de Ti2+, et obtenir ainsi de meilleurs rendements faradiques. Lâoxycarbure de titane a un potentiel de dissolution anodique Ă©levĂ© proche du potentiel du couple Ti3+/Ti4+. Il est donc important dâappliquer une faible densitĂ© de courant lors de lâĂ©lectrodissolution de TiC0,5O0,5 pour Ă©viter la formation dâions Ti4+ et la chute des rendements faradiques. Lâutilisation dâune faible densitĂ© de courant a Ă©galement permis de favoriser la production de CO et de limiter celle de CO2, lors de lâĂ©lectro-raffinage de TiC0,5O0,5, pour Ă©viter la contamination en C et O du titane produit. LâĂ©valuation de la puretĂ© des dĂ©pĂŽts de titane a rĂ©vĂ©lĂ© une faible teneur en carbone et une forte teneur en oxygĂšne. NĂ©anmoins, il a Ă©tĂ© dĂ©montrĂ© que lâoxygĂšne prĂ©sent dans les dĂ©pĂŽts ne provient pas du matĂ©riau dâanode mais plutĂŽt dâune contamination par les oxydes et/ou oxychlorures pouvant exister dans lâĂ©lectrolyte fondu, ou de lâĂ©tape de nettoyage du dĂ©pĂŽt Ă lâeau pouvant provoquer son oxydation.This work is devoted to the study of electrowinning of a titanium oxycarbide anode in a molten salt. Two parts have been studied: the synthesis of the TiC0,5O0,5 anode and the development of an electrolytic process. The anode material was synthesized by carbothermal reduction of TiO2 at different temperatures. The optimal conditions to reach a pure and single-phase composition of TiC0,5O0,5 are: carboreduction of TiO2 at 1500 °C for 4 hours followed by an annealing treatment identical to the first one. The elaboration of titanium in molten salt is delicate because of the existence of multiple oxidation degrees in solution (Ti4+, Ti3+, Ti2+and Ti0), leading to the formation of mediamutation reactions and the fall of faradic yields. The challenge was therefore to adapt the salt composition to stabilize the Ti3+ oxidation state. Analytical chemistry studies were performed in two chloro-fluoride medium with different F/Ti ratios. It was shown that using an electrolyte with a high F/Ti ratio (in this case, F/Ti = 87; LiCl-KCl-K2TiF6) maximizes the presence of Ti3+ and minimizes the existence of Ti2+, thus obtaining better faradic yields. Titanium oxycarbide has a high anodic dissolution potential close to the potential of the Ti3+/Ti4+ couple. Therefore, it is important to apply a low current density during the electrowinning of TiC0,5O0,5 to avoid C and O contamination of the titanium produced. The evaluation of the purity of titanium revealed a low carbon and high oxygen content. However, it has been shown that the oxygen present in the deposits does not come from the anode material but rather from contamination by oxides and/or oxychlorides that may exist in the molten salt, or from the cleaning step of the deposit with water that may cause its oxidation
Production of Metallic Titanium by Electrowinning in Molten Salts of Titanium Oxycarbide Anode
The electrochemical behavior of Ti3+ in LiCl-LiF-TiF3 salt was investigated by cyclic and square wave voltammetries at 853 K. Both methods confirm the presence of a single reduction wave of Ti3+ ions to metal, at a potential of â2.3 V vs. Cl2/Clâ. The closeness of the potentials of TiCxOy dissolution and Ti3+/Ti4+ wave is an issue during the electrorefining of the anode. A low current density has to be applied to stay within the titanium oxycarbide dissolution and avoid the formation of Ti4+. The titanium deposition was studied by electrorefining of a titanium metal plate in LiCl-LiF-TiF3 (0.62 mol/kg). The cathodic deposit analysis by XRD and SEM confirms the formation of titanium metal with an average grain size of 150 ”m. The faradic deposition yields are above 85% and constant between 60 and 160 mA/cm2