Dr. Khanna's expertise in crossdisciplinary research areas include orthopedic implants, bone tissue engineering, nanomechanics, and currently, fabrication of novel bio-inspired organic-inorganic nanocomposites with tunable mechanical performance. He received intensive postdoctoral training in interdisciplinary research areas concerning artificial hip joints, thin film electrode materials and characterization of metal-capped ceramics from leading national institutes and universities in Japan and USA. He is the recipient of prestigious JSPS (Japan Society for Promotion of Science) postdoctoral fellowship and research grant. Dr. Khanna received his PhD in Materials and Nanotechnology at North Dakota State University, specializing in mechanical behavior of cell-biomaterial composites. He received his MS in Materials and Metallurgical Engineering at Indian Institute of Technology Kanpur and BS in Ceramic Engineering at National Institute of Technology Rourkela. His research has led to development of high wear resistant and reliable artificial hip joint, cost-effective surface treatments to form conductive nanofibrous surface layer of Ti-oxynitrides for water splitting and to understanding the mechanisms of metal capping on ceramics. Address: USA
A Ti metal electrode with nanostructured titanium oxide that possesses high electrical conductivi... more A Ti metal electrode with nanostructured titanium oxide that possesses high electrical conductivity, a large specific surface area and the capacity for supporting catalysts was prepared by a simple solution and heat treatment.
Materials science & engineering. C, Materials for biological applications, 2015
In many hip replacement surgeries, monolithic alumina is used as a femoral head due to its high w... more In many hip replacement surgeries, monolithic alumina is used as a femoral head due to its high wear resistance. However, it is liable to fracture under load bearing operations in artificial joints. We propose a promising way to overcome this limitation by forming a dense alumina layer onto a relatively tough substrate such as Ti-6Al-4V alloy to obtain high wear resistance on a material that can sustain relatively high toughness. For this purpose, Al metal powders were deposited onto Ti-6Al-4V alloy by cold spraying in N2 atmosphere. Interfacial adhesion between Al and the Ti alloy was improved by the formation of a reaction layer of Al3Ti between them by heating at 640°C for 1h in air. Subsequently, micro-arc oxidation treatment was performed to oxidize Al. The oxidized layer was composed of an outer porous layer of γ-alumina and inner-most dense layer of α-alumina. The α-alumina layer was almost fully densified and exhibited high Vickers hardness almost equal to that of alumina ce...
The purpose of this research is to form a layer of alumina on Ti-6Al-4V alloy for hip joint by de... more The purpose of this research is to form a layer of alumina on Ti-6Al-4V alloy for hip joint by deposition of Al layer on the Ti alloy and its subsequent oxidation. In this work, a thick layer of Al was deposited onto the Ti alloy by cold spraying. The reaction layer of Al3Ti was formed by heat treatment of cold sprayed Al at 640°C in air/Ar atmosphere to ensure a good adhesion between cold sprayed Al layer and the Ti alloy. A thick Al3Ti layer formed by heat treatment of Al layer at 640°C for 12 h in air, was subjected to heat treatment at 850°C for 96 h in air to form a-alumina and Al2Ti. Thus, alumina scales can be formed on the top surface of the Ti alloy and can be densified by increasing the time duration of heat treatment.
ABSTRACT TiO2 nanostructures have attracted much attention due to their semi-conductivity and pho... more ABSTRACT TiO2 nanostructures have attracted much attention due to their semi-conductivity and photocatalytic properties, but are rarely used as functional electrodes for water electrolysis that requires high electrical conductivity. Compared to TiO2, a high doping level of N into titanates is expected due to their layered structure, which was attempted to improve the conductivity. Here, a surface layer of one dimensional hydrogen titanate (H-titanate) nanofibers with high surface area and poor crystallinity was synthesized on the surface of Ti metal by mild NaOH and HCl treatments, as compared to the commonly used severe hydrothermal treatments. The poorly crystallized structure of the layered H-titanate allowed the incorporation of a large amount of N into its surface layer by thermal treatments at 700 °C or more, thereby transforming it into Ti-oxynitrides with high electrical conductivity while retaining the high surface area of the treated layer. The depth profile analyses of the chemically and thermally treated Ti metal revealed that the concentration of O and H was the highest at the top surface of the surface layer. With increasing depth, the concentration of O and H decreased gradually whereas the concentration of N increased gradually, indicating gradients in the structures of the treated nanofibrous surface layer. The dense region below the nanofibrous surface layer was composed of Ti2N, whose amount increased with increasing temperature. This kind of gradient surface layer of N-doped titanate nanofibers without well-defined interfaces was synthesized on the surface of the Ti electrode by our unique chemical and thermal treatments and was modeled with varying depths. The specific objective of the present work is to characterize and study the mechanism of formation of the N-doped structures in a one dimensional gradient surface layer of H-titanate nanofibers synthesized on the treated Ti electrode. The treated one dimensional nanofibrous surface layer on a Ti electrode can be potentially used for the electro-splitting of water after fixation of molecular catalysts on its surface.
Current trends in total hip arthroplasty (THA) are to develop novel artificial hip joints with hi... more Current trends in total hip arthroplasty (THA) are to develop novel artificial hip joints with high wear resistance and mechanical reliability with a potential to last for at least 25–30 years for both young and old active patients. Currently used artificial hip joints are mainly composed of femoral head of monolithic alumina or alumina-zirconia composites articulating against cross-linked polyethylene liner of acetabular cup or Co-Cr alloy in a self-mated configuration. However, the possibility of fracture of ceramics or its composites, PE wear debris-induced osteolysis, and hypersensitivity issue due to metal ion release cannot be eliminated. In some cases, thin ultra-hard diamond-based, TiN coatings on Ti-6A-4V or thin zirconia layer on the Zr-Nb alloy have been fabricated to develop high wear resistant bearing surfaces. However, these coatings showed poor adhesion in tribological testing. To provide high wear resistance and mechanical reliability to femoral head, a new kind of ceramic/metal artificial hip joint hybrid was recently proposed in which 10–15 µm thick dense layer of pure α-alumina was formed onto Ti-6Al-4V alloy by deposition of Al metal layer by cold spraying or cold metal transfer methods with 1–2 µm thick Al 3 Ti reaction layer formed at their interface to improve adhesion. An optimal micro-arc oxidation treatment transformed Al to dense α-alumina layer, which showed high Vickers hardness 1900 HV and good adhesion to the substrate. Further tribological and cytotoxicity analyses of these hybrids will determine their efficacy for potential use in THA.
Recent advances in alumina ceramics are focused toward innovative processing routes to improve th... more Recent advances in alumina ceramics are focused toward innovative processing routes to improve their mechanical reliability while retaining their superior wear resistance, which might be possible if a thin layer of dense alumina can be formed on a metallic substrate such as Ti–6Al–4V with high mechanical strength. For this purpose, we propose a new two-step process in which a dense layer of Al deposited on the Ti alloy by cold metal transfer method, formed a dense Al 3 Ti gradient reaction layer at their interface to improve adhesion in a single step. Subsequent micro-arc oxidation treatment transformed Al layer to a graded alumina layer in which c-alumina decreased and a-alumina increased with increasing depth. Abrasion of outer regions revealed underlying pure a-alumina regions with high Vickers hardness matching with that of sintered alumina. The designed alumina/Ti alloy hybrid can be a potential candidate for wear resistance applications.
Recent advances in hip replacements are focused towards producing reliable bearing surfaces to en... more Recent advances in hip replacements are focused towards producing reliable bearing surfaces to enhance their longevity. In this perspective, progressive attempts have been made to improve the wear resistance of polyeth-ylene to eliminate osteolysis and mechanical reliability of brittle alumina ceramics, but in vain. It is proposed that both high wear resistance and mechanical reliability can be retained if a thin layer of dense alumina is formed onto high toughness Ti-6Al-4V alloy. For this purpose, we devised a unique methodology in which a layer of Al metal was deposited onto the Ti alloy substrate by cold spraying (CS), followed by a heat treatment to form Al 3 Ti reaction layer at their interface to improve adhesion and subsequent micro-arc oxidation (MAO) treatment to transform Al to alumina layer. An optimal MAO treatment of cold sprayed Al formed an adherent and dense α-alumina layer with high Vickers hardness matching with that of sintered alumina used as a femoral head. Structure phase property relationships in dense α-alumina layer have been revealed and discussed in the light of our research findings. The designed alumina/Ti alloy hybrid might be a potential candidate for reliable bearing surfaces of artificial hip joint.
A Ti metal electrode with nanostructured titanium oxide that possesses high electrical conductivi... more A Ti metal electrode with nanostructured titanium oxide that possesses high electrical conductivity, a large specific surface area and the capacity for supporting catalysts was prepared by a simple solution and heat treatment. A precursor of the electrode that possesses one-dimensional hydrogen titanate, H2Ti3O7, 600 nm in thickness was produced by soaking the metal in 5 M NaOH at 60 C and subsequently in a 0.5 mM HCl solution at 40 C. The treated metal had a high specific surface area approximately 100 times higher than theoretical flat surface, but its scratch resistance was low. The heat treatment of the hydrogen titanate at 650 C for 1 h under air increased the scratch resistance markedly, but resulted in the development of an electric insulated surface layer that was composed of anatase and rutile. In contrast, when heat-treated under an N2 atmosphere, the hydrogen titanate was transformed into anatase containing a small amount of Ti4O7, TiN, TiNxO1x and Ti2N, which exhibited a relatively higher electrical conductivity that was in the range of semiconducting materials. It was also shown that the treated metal immobilized 1,10-ferrocenylbis(phosphonic acid) by forming a Ti–O–P bond and thereby induced a high electric current upon cyclic voltammetry, although the treated metal before the ferrocene modification showed almost no electric current. Thus, the treated Ti metal is expected to be useful as an electrode for various types of electrochemical systems due to its high specific surface area, electrical conductivity and large capacity for supporting catalysts.
In many hip replacement surgeries, monolithic alumina is used as a femoral head due to its high w... more In many hip replacement surgeries, monolithic alumina is used as a femoral head due to its high wear resistance. However, it is liable to fracture under load bearing operations in artificial joints. We propose a promising way to overcome this limitation by forming a dense alumina layer onto a relatively tough substrate such as Ti-6Al-4V alloy to obtain high wear resistance on a material that can sustain relatively high toughness. For this purpose, Al metal powders were deposited onto Ti-6Al-4V alloy by cold spraying in N2 atmosphere. Interfacial adhesion between Al and the Ti alloy was improved by the formation of a reaction layer of Al3Ti between them by heating at 640C for 1h in air. Subsequently, micro-arc oxidation treatment was performed to oxidize Al. The oxidized layer was composed of an outer porous layer of -alumina and inner-most dense layer of -alumina. The -alumina layer was almost fully densified and exhibited high Vickers hardness almost equal to that of alumina ceramics used as the femoral head. Thus, the newly developed dense alumina/Ti alloy can be potentially used to produce the reliable bearing surfaces of artificial hip joint.
TiO2 nanostructures have attracted much attention due to their semi-conductivity and photocatalyt... more TiO2 nanostructures have attracted much attention due to their semi-conductivity and photocatalytic properties, but are rarely used as functional electrodes for water electrolysis that requires high electrical conductivity. Compared to TiO2, a high doping level of N into titanates is expected due to their layered structure, which was attempted to improve the conductivity. Here, a surface layer of one dimensional hydrogen titanate (H-titanate) nanofibers with high surface area and poor crystallinity was synthesized on the surface of Ti metal by mild NaOH and HCl treatments, as compared to the commonly used severe hydrothermal treatments. The poorly crystallized structure of the layered H-titanate allowed the incorporation of a large amount of N into its surface layer by thermal treatments at 700 °C or more, thereby transforming it into Ti-oxynitrides with high electrical conductivity while retaining the high surface area of the treated layer. The depth profile analyses of the chemically and thermally treated Ti metal revealed that the concentration of O and H was the highest at the top surface of the surface layer. With increasing depth, the concentration of O and H decreased gradually whereas the concentration of N increased gradually, indicating gradients in the structures of the treated nanofibrous surface layer. The dense region below the nanofibrous surface layer was composed of Ti2N, whose amount increased with increasing temperature. This kind of gradient surface layer of N-doped titanate nanofibers without well-defined interfaces was synthesized on the surface of the Ti electrode by our unique chemical and thermal treatments and was modeled with varying depths. The specific objective of the present work is to characterize and study the mechanism of formation of the N-doped structures in a one dimensional gradient surface layer of H-titanate nanofibers synthesized on the treated Ti electrode. The treated one dimensional nanofibrous surface layer on a Ti electrode can be potentially used for the electro-splitting of water after fixation of molecular catalysts on its surface.
A Ti metal electrode with nanostructured titanium oxide that possesses high electrical conductivi... more A Ti metal electrode with nanostructured titanium oxide that possesses high electrical conductivity, a large specific surface area and the capacity for supporting catalysts was prepared by a simple solution and heat treatment.
Materials science & engineering. C, Materials for biological applications, 2015
In many hip replacement surgeries, monolithic alumina is used as a femoral head due to its high w... more In many hip replacement surgeries, monolithic alumina is used as a femoral head due to its high wear resistance. However, it is liable to fracture under load bearing operations in artificial joints. We propose a promising way to overcome this limitation by forming a dense alumina layer onto a relatively tough substrate such as Ti-6Al-4V alloy to obtain high wear resistance on a material that can sustain relatively high toughness. For this purpose, Al metal powders were deposited onto Ti-6Al-4V alloy by cold spraying in N2 atmosphere. Interfacial adhesion between Al and the Ti alloy was improved by the formation of a reaction layer of Al3Ti between them by heating at 640°C for 1h in air. Subsequently, micro-arc oxidation treatment was performed to oxidize Al. The oxidized layer was composed of an outer porous layer of γ-alumina and inner-most dense layer of α-alumina. The α-alumina layer was almost fully densified and exhibited high Vickers hardness almost equal to that of alumina ce...
The purpose of this research is to form a layer of alumina on Ti-6Al-4V alloy for hip joint by de... more The purpose of this research is to form a layer of alumina on Ti-6Al-4V alloy for hip joint by deposition of Al layer on the Ti alloy and its subsequent oxidation. In this work, a thick layer of Al was deposited onto the Ti alloy by cold spraying. The reaction layer of Al3Ti was formed by heat treatment of cold sprayed Al at 640°C in air/Ar atmosphere to ensure a good adhesion between cold sprayed Al layer and the Ti alloy. A thick Al3Ti layer formed by heat treatment of Al layer at 640°C for 12 h in air, was subjected to heat treatment at 850°C for 96 h in air to form a-alumina and Al2Ti. Thus, alumina scales can be formed on the top surface of the Ti alloy and can be densified by increasing the time duration of heat treatment.
ABSTRACT TiO2 nanostructures have attracted much attention due to their semi-conductivity and pho... more ABSTRACT TiO2 nanostructures have attracted much attention due to their semi-conductivity and photocatalytic properties, but are rarely used as functional electrodes for water electrolysis that requires high electrical conductivity. Compared to TiO2, a high doping level of N into titanates is expected due to their layered structure, which was attempted to improve the conductivity. Here, a surface layer of one dimensional hydrogen titanate (H-titanate) nanofibers with high surface area and poor crystallinity was synthesized on the surface of Ti metal by mild NaOH and HCl treatments, as compared to the commonly used severe hydrothermal treatments. The poorly crystallized structure of the layered H-titanate allowed the incorporation of a large amount of N into its surface layer by thermal treatments at 700 °C or more, thereby transforming it into Ti-oxynitrides with high electrical conductivity while retaining the high surface area of the treated layer. The depth profile analyses of the chemically and thermally treated Ti metal revealed that the concentration of O and H was the highest at the top surface of the surface layer. With increasing depth, the concentration of O and H decreased gradually whereas the concentration of N increased gradually, indicating gradients in the structures of the treated nanofibrous surface layer. The dense region below the nanofibrous surface layer was composed of Ti2N, whose amount increased with increasing temperature. This kind of gradient surface layer of N-doped titanate nanofibers without well-defined interfaces was synthesized on the surface of the Ti electrode by our unique chemical and thermal treatments and was modeled with varying depths. The specific objective of the present work is to characterize and study the mechanism of formation of the N-doped structures in a one dimensional gradient surface layer of H-titanate nanofibers synthesized on the treated Ti electrode. The treated one dimensional nanofibrous surface layer on a Ti electrode can be potentially used for the electro-splitting of water after fixation of molecular catalysts on its surface.
Current trends in total hip arthroplasty (THA) are to develop novel artificial hip joints with hi... more Current trends in total hip arthroplasty (THA) are to develop novel artificial hip joints with high wear resistance and mechanical reliability with a potential to last for at least 25–30 years for both young and old active patients. Currently used artificial hip joints are mainly composed of femoral head of monolithic alumina or alumina-zirconia composites articulating against cross-linked polyethylene liner of acetabular cup or Co-Cr alloy in a self-mated configuration. However, the possibility of fracture of ceramics or its composites, PE wear debris-induced osteolysis, and hypersensitivity issue due to metal ion release cannot be eliminated. In some cases, thin ultra-hard diamond-based, TiN coatings on Ti-6A-4V or thin zirconia layer on the Zr-Nb alloy have been fabricated to develop high wear resistant bearing surfaces. However, these coatings showed poor adhesion in tribological testing. To provide high wear resistance and mechanical reliability to femoral head, a new kind of ceramic/metal artificial hip joint hybrid was recently proposed in which 10–15 µm thick dense layer of pure α-alumina was formed onto Ti-6Al-4V alloy by deposition of Al metal layer by cold spraying or cold metal transfer methods with 1–2 µm thick Al 3 Ti reaction layer formed at their interface to improve adhesion. An optimal micro-arc oxidation treatment transformed Al to dense α-alumina layer, which showed high Vickers hardness 1900 HV and good adhesion to the substrate. Further tribological and cytotoxicity analyses of these hybrids will determine their efficacy for potential use in THA.
Recent advances in alumina ceramics are focused toward innovative processing routes to improve th... more Recent advances in alumina ceramics are focused toward innovative processing routes to improve their mechanical reliability while retaining their superior wear resistance, which might be possible if a thin layer of dense alumina can be formed on a metallic substrate such as Ti–6Al–4V with high mechanical strength. For this purpose, we propose a new two-step process in which a dense layer of Al deposited on the Ti alloy by cold metal transfer method, formed a dense Al 3 Ti gradient reaction layer at their interface to improve adhesion in a single step. Subsequent micro-arc oxidation treatment transformed Al layer to a graded alumina layer in which c-alumina decreased and a-alumina increased with increasing depth. Abrasion of outer regions revealed underlying pure a-alumina regions with high Vickers hardness matching with that of sintered alumina. The designed alumina/Ti alloy hybrid can be a potential candidate for wear resistance applications.
Recent advances in hip replacements are focused towards producing reliable bearing surfaces to en... more Recent advances in hip replacements are focused towards producing reliable bearing surfaces to enhance their longevity. In this perspective, progressive attempts have been made to improve the wear resistance of polyeth-ylene to eliminate osteolysis and mechanical reliability of brittle alumina ceramics, but in vain. It is proposed that both high wear resistance and mechanical reliability can be retained if a thin layer of dense alumina is formed onto high toughness Ti-6Al-4V alloy. For this purpose, we devised a unique methodology in which a layer of Al metal was deposited onto the Ti alloy substrate by cold spraying (CS), followed by a heat treatment to form Al 3 Ti reaction layer at their interface to improve adhesion and subsequent micro-arc oxidation (MAO) treatment to transform Al to alumina layer. An optimal MAO treatment of cold sprayed Al formed an adherent and dense α-alumina layer with high Vickers hardness matching with that of sintered alumina used as a femoral head. Structure phase property relationships in dense α-alumina layer have been revealed and discussed in the light of our research findings. The designed alumina/Ti alloy hybrid might be a potential candidate for reliable bearing surfaces of artificial hip joint.
A Ti metal electrode with nanostructured titanium oxide that possesses high electrical conductivi... more A Ti metal electrode with nanostructured titanium oxide that possesses high electrical conductivity, a large specific surface area and the capacity for supporting catalysts was prepared by a simple solution and heat treatment. A precursor of the electrode that possesses one-dimensional hydrogen titanate, H2Ti3O7, 600 nm in thickness was produced by soaking the metal in 5 M NaOH at 60 C and subsequently in a 0.5 mM HCl solution at 40 C. The treated metal had a high specific surface area approximately 100 times higher than theoretical flat surface, but its scratch resistance was low. The heat treatment of the hydrogen titanate at 650 C for 1 h under air increased the scratch resistance markedly, but resulted in the development of an electric insulated surface layer that was composed of anatase and rutile. In contrast, when heat-treated under an N2 atmosphere, the hydrogen titanate was transformed into anatase containing a small amount of Ti4O7, TiN, TiNxO1x and Ti2N, which exhibited a relatively higher electrical conductivity that was in the range of semiconducting materials. It was also shown that the treated metal immobilized 1,10-ferrocenylbis(phosphonic acid) by forming a Ti–O–P bond and thereby induced a high electric current upon cyclic voltammetry, although the treated metal before the ferrocene modification showed almost no electric current. Thus, the treated Ti metal is expected to be useful as an electrode for various types of electrochemical systems due to its high specific surface area, electrical conductivity and large capacity for supporting catalysts.
In many hip replacement surgeries, monolithic alumina is used as a femoral head due to its high w... more In many hip replacement surgeries, monolithic alumina is used as a femoral head due to its high wear resistance. However, it is liable to fracture under load bearing operations in artificial joints. We propose a promising way to overcome this limitation by forming a dense alumina layer onto a relatively tough substrate such as Ti-6Al-4V alloy to obtain high wear resistance on a material that can sustain relatively high toughness. For this purpose, Al metal powders were deposited onto Ti-6Al-4V alloy by cold spraying in N2 atmosphere. Interfacial adhesion between Al and the Ti alloy was improved by the formation of a reaction layer of Al3Ti between them by heating at 640C for 1h in air. Subsequently, micro-arc oxidation treatment was performed to oxidize Al. The oxidized layer was composed of an outer porous layer of -alumina and inner-most dense layer of -alumina. The -alumina layer was almost fully densified and exhibited high Vickers hardness almost equal to that of alumina ceramics used as the femoral head. Thus, the newly developed dense alumina/Ti alloy can be potentially used to produce the reliable bearing surfaces of artificial hip joint.
TiO2 nanostructures have attracted much attention due to their semi-conductivity and photocatalyt... more TiO2 nanostructures have attracted much attention due to their semi-conductivity and photocatalytic properties, but are rarely used as functional electrodes for water electrolysis that requires high electrical conductivity. Compared to TiO2, a high doping level of N into titanates is expected due to their layered structure, which was attempted to improve the conductivity. Here, a surface layer of one dimensional hydrogen titanate (H-titanate) nanofibers with high surface area and poor crystallinity was synthesized on the surface of Ti metal by mild NaOH and HCl treatments, as compared to the commonly used severe hydrothermal treatments. The poorly crystallized structure of the layered H-titanate allowed the incorporation of a large amount of N into its surface layer by thermal treatments at 700 °C or more, thereby transforming it into Ti-oxynitrides with high electrical conductivity while retaining the high surface area of the treated layer. The depth profile analyses of the chemically and thermally treated Ti metal revealed that the concentration of O and H was the highest at the top surface of the surface layer. With increasing depth, the concentration of O and H decreased gradually whereas the concentration of N increased gradually, indicating gradients in the structures of the treated nanofibrous surface layer. The dense region below the nanofibrous surface layer was composed of Ti2N, whose amount increased with increasing temperature. This kind of gradient surface layer of N-doped titanate nanofibers without well-defined interfaces was synthesized on the surface of the Ti electrode by our unique chemical and thermal treatments and was modeled with varying depths. The specific objective of the present work is to characterize and study the mechanism of formation of the N-doped structures in a one dimensional gradient surface layer of H-titanate nanofibers synthesized on the treated Ti electrode. The treated one dimensional nanofibrous surface layer on a Ti electrode can be potentially used for the electro-splitting of water after fixation of molecular catalysts on its surface.
Uploads
Papers by Rohit Khanna
specific surface area and the capacity for supporting catalysts was prepared by a simple solution and heat
treatment. A precursor of the electrode that possesses one-dimensional hydrogen titanate, H2Ti3O7,
600 nm in thickness was produced by soaking the metal in 5 M NaOH at 60 C and subsequently in a
0.5 mM HCl solution at 40 C. The treated metal had a high specific surface area approximately 100
times higher than theoretical flat surface, but its scratch resistance was low. The heat treatment of the
hydrogen titanate at 650 C for 1 h under air increased the scratch resistance markedly, but resulted in
the development of an electric insulated surface layer that was composed of anatase and rutile. In
contrast, when heat-treated under an N2 atmosphere, the hydrogen titanate was transformed into
anatase containing a small amount of Ti4O7, TiN, TiNxO1x and Ti2N, which exhibited a relatively higher
electrical conductivity that was in the range of semiconducting materials. It was also shown that the
treated metal immobilized 1,10-ferrocenylbis(phosphonic acid) by forming a Ti–O–P bond and thereby
induced a high electric current upon cyclic voltammetry, although the treated metal before the
ferrocene modification showed almost no electric current. Thus, the treated Ti metal is expected to be
useful as an electrode for various types of electrochemical systems due to its high specific surface area,
electrical conductivity and large capacity for supporting catalysts.
specific surface area and the capacity for supporting catalysts was prepared by a simple solution and heat
treatment. A precursor of the electrode that possesses one-dimensional hydrogen titanate, H2Ti3O7,
600 nm in thickness was produced by soaking the metal in 5 M NaOH at 60 C and subsequently in a
0.5 mM HCl solution at 40 C. The treated metal had a high specific surface area approximately 100
times higher than theoretical flat surface, but its scratch resistance was low. The heat treatment of the
hydrogen titanate at 650 C for 1 h under air increased the scratch resistance markedly, but resulted in
the development of an electric insulated surface layer that was composed of anatase and rutile. In
contrast, when heat-treated under an N2 atmosphere, the hydrogen titanate was transformed into
anatase containing a small amount of Ti4O7, TiN, TiNxO1x and Ti2N, which exhibited a relatively higher
electrical conductivity that was in the range of semiconducting materials. It was also shown that the
treated metal immobilized 1,10-ferrocenylbis(phosphonic acid) by forming a Ti–O–P bond and thereby
induced a high electric current upon cyclic voltammetry, although the treated metal before the
ferrocene modification showed almost no electric current. Thus, the treated Ti metal is expected to be
useful as an electrode for various types of electrochemical systems due to its high specific surface area,
electrical conductivity and large capacity for supporting catalysts.