Fabrication And Hydrogen Sensing Properties Of Ttitania-based Composite Oxide Nanotubes

As a promising semiconductor titania is applied in many fields such as solar cell and photocatalytic devices. In this work, we optimized the anodization conditions of titanium and its alloys, and fabricated highly aligned titania-based nanotube arrays. We annealed the optimized nanotube arrays to obtain anatase nanotubes for further hydrogen sensing testings.The experimental results indicated that both the anodization voltage and temperature were key factors for fabricating highly aligned titania-based nanotubes. Higher anodization temperature could accelerate the dissolve speed on top of the nanotubes. And the anodization voltage could affect the length and the diameter of the nanotubes. We anodized as-cast Ti35NbxZr alloys. We found the nanotubes grew longer along with the increased Zr concentration. We also found that Zr dissolved much faster than other elements within the anodization course, and it accelerated the anodization. When the peak-aged Ti35Nb5Zr alloy was anodized in 1M NaH2PO4+0.5M HF electrolyte, it was found that the anodization voltage could affect the diameter of the nanotubes and also the thickness of the nanotube wall. The bonding strength between the nanotubes and the substrate was so weak that the nanotube film could stripe off the substrate during ultrasonic vibration. Peak-aged Ti35Nb5Zr alloy had two phases, and the anodization speeds are different between them in sulfate-based solution, but an organic solution could eliminate the difference. At last, we annealed the nanotube films fabricated on titanium and its alloys, and tested their hydrogen sensitivities. The testing results showed that, nanotube thin film fabricated on titanium exhibited different responses to atmospheres containing 100-1000ppm hydrogen, and its responses to the same H2 concentration atmospheres were the same; the nanotube thin film fabricated on Ti35Nb alloy exhibited no response to atmospheres containing H2 less than 500ppm, but it exhibited good sensitivity in atmospheres containing more than 500ppm H2.