Hydrogen Sensing Properties of Mesoporous SnO2 Loaded with Noble Metal

ナノダイナミクス国際シンポジウム 平成22年1月21日(木) 於長崎大学Nagasaki Symposium on Nano-Dynamics 2010 (NSND2010), January 21, 2010, Nagasaki University, Nagasaki, Japan, Invited Lectur

Gas-sensing Properties of Photoluminescence-type Macroporous SnO2-based Sensors

ナノダイナミクス国際シンポジウム 平成22年1月21日(木) 於長崎大学Nagasaki Symposium on Nano-Dynamics 2010 (NSND2010), January 21, 2010, Nagasaki University, Nagasaki, Japan, Invited Lectur

H2 sensing properties of diode-type gas sensors fabricated with Ti- and/or Nb-based materials

A thermally oxidized TiO2 or Nb2O5 film equipped with a top Pd film electrode and a bottom Ti or Nb plate electrode (Pd/MO(n)/M, MO: oxide film, M: metal plate, n: annealing temperature (°C)) has been investigated as a diode-type H2 sensor under air or N2 atmosphere. Pd/TiO2(n)/Ti sensors showed relatively poor H2 sensing properties in air, in comparison with Pd/anodic-TiO2(n)/Ti sensors constructed with an anodized TiO2 film equipped with a top Pd film electrode and a bottom Ti plate electrode, which were reported in our previous studies. On the other hand, Pd/Nb2O5(n)/Nb sensors showed relatively larger H2 response with fast response and recovery speeds than Pd/TiO2(n)/Ti sensors in air under high forward bias conditions. A Pd/Nb2O5(450)/Ti sensor, which was fabricated by radio-frequency magnetron sputtering of Nb metal on a Ti substrate followed by thermal oxidation at 450 °C, showed the largest H2 response and relatively fast response and recovery speeds in air, among the sensors tested. In addition, H2 response of the Pd/Nb2O5(450)/Ti sensor in air was much lower than that in N2, but the logarithm of H2 response was almost proportional to the logarithm of H2 concentration in a wide range of H2 concentration (10-8000 ppm) in air, and the H2 sensitivity in air was much higher than that in N2

Effects of microstructure of mesoporous SnO2 powders on their H2 sensing properties

Various mesoporous tin dioxide (m-SnO2) powders were prepared from two kinds of combination of a tin source and a surfactant template, and their H2 sensing properties were investigated. The specific surface area and pore volume of the m-SnO2 powder prepared from Na2SnO3・3H2O as a tin source and n-cetylpyridinium chloride monohydrate (C16PyCl; (C5H5NC16H33)Cl・H2O) as a template under a fixed pH value of 10 (m-SnO2(1)) were larger than those of the m-SnO2 powders prepared from SnCl4・5H2O as a tin source and aerosol-OT (AOT; C20H37O7SNa) as a template under different pH conditions (m-SnO2(2)-n; n is the value of pH of the precursor solution). However, the specific surface area of m-SnO2(1) decreased drastically by post-grinding, while m-SnO2(2)-n powders with small secondary agglomerates showed only a slight decrease in specific surface area during post-grinding. In addition, m-SnO2(2)-n sensors exhibited better H2 response and lower resistance than those of m-SnO2(1) sensor, especially at low operating temperatures, probably because of moderately developed mesopores which promoted easier diffusion of H2 to the most sensitive region of the surface of SnO2 particles

H2S Sensing Properties and Mechanism of Macroporous Semiconductor Sensors

Macroporous (mp-) In2O3-based films with and without 1 wt% CuO loading were fabricated by a modified sol-gel technique employing polymethylmethacrylate microspheres as a template and their sensor responses to H2S and the reaction behavior of H2S over the sensor materials were investigated. Introduction of macropores into an In2O3 film and simultaneous loading of CuO on the In2O3 surface were enormously effective in improving the H2S response. The large surface area of mp-In2O3 loaded with CuO, which increased the reactivity of CuO with H2S, is probably the most important factor to enhance the H2S response.214th ECS Meeting : Honolulu, HI, October 12 - October 17, 200

Fabrication of porous alumina ceramics having cell windows with controlled size by PMMA template method

Highly porous alumina compacts have been prepared by filling alumina slurry into opening of a specially designed template block prepared by cross-linked (cl-) polymethylmethacrylate (PMMA) microspheres (mean particle size: 98.6 μm) under reduced pressure, followed by firing to remove the template and then sintering at 1600 °C. The template blocks were prepared by utilizing cl-PMMA and acetone solution dissolving noncrosslinked (Ncl-) PMMA as an adhesive to make partial connection among the cl-PMMA microspheres. Furthermore, the effects of the addition of other chemicals (two types of triblockcopolymers and a nonionic surfactant) to the Ncl-PMMA adhesive solution were tested to improve the wettability of the solution to cl-PMMA and then to control the cell windows among the cl-PMMA-originated cells after the firing. By employing the template block, prepared with the adhesive solution containing an appropriate amount of triblockcopolymer, a highly porous alumina compact having an open porosity of 77.2%, a mean cell window diameter of 28.8 μm, and strong alumina skeleton could be fabricated.The original publication is available at www.springerlink.co

Effects of Porous Structure of the Auxiliary Electrode on the CO2 Sensing Properties of a NASICON-based Sensor

Structural effects of the auxiliary electrode layer on the CO_2 sensing properties of NASICON (Na_3Zr_2Si_2PO_) solid electrolyte sensors have been investigated. The sensor with a macroporous Li_2CO_3-BaCO_3-based auxiliary layer showed faster CO_2 response and recovery and a smaller EMF drift against a humidity change than those observed for the sensor equipped with a dense auxiliary layer. The CO_2 response of the present sensors was slightly larger than the theoretical one. This suggests the existence of some impurities capable of reacting with CO_2 in the auxiliary layer prepared in the present study.Nagasaki Symposium on Nano-Dynamics 2008 (NSND2008) 平成20年1月29日(火)於長崎大学 Poster Presentatio

Characterizations of Polystyrene-Based Hybrid Particles Containing Hydrophobic Mg (

Polystyrene (PS)-based hybrid particles containing a large amount of Mg(OH)2 powder treated with methylhydrogen polysiloxane (MHS) were fabricated by a bulk and subsequent suspension two-step polymerization method. All the particles fabricated showed spherical shape and their particle sizes were about 500 μm, irrespective of the additive amount of the Mg(OH)2 powder modified with MHS (ST-1). The actual content of ST-1 powder incorporated inside each kind of hybrid particle was almost the same as that in the raw mixture, and agglomeration of ST-1 powder was hardly observed inside the hybrid particles. The compressive strength of the hybrid particles remained almost unchanged, even when the ST-1 powder content increased from 10 to 50 phr. Furthermore, a composite fabricated by employing the hybrid particles achieved homogenous distribution of ST-1 powder and showed a higher oxygen index than that of a composite fabricated by directly mixing of PS pellets and ST-1 powder

Fabrication of Highly Porous Alumina-Based Ceramics with Connected Spaces by Employing PMMA Microspheres as a Template

Highly porous alumina-based ceramics were fabricated by a slip casting method by employing polymethylmethacrylate (PMMA) microspheres having different diameters as a template and MgO or SiC powder as a sintering aid and subsequent calcination at 1600°C. Spherical pores reflecting the morphology of the PMMA microspheres could be fabricated. In addition, the formation of much smaller connected space among the pores was observed on the pore\u27s inner walls of all ceramics. In this method, porous structure, for example, pore diameter, shape (open or closed), and mechanical properties, could be controlled by varying the particle size of PMMA microspheres and its concentration in alumina-based slurries. Highly porous and mechanically strong alumina-based ceramics having an open porosity of 62, a connected space size of 1.3 m, and a compressive strength of 147.6 MPa could be fabricated by employing PMMA microspheres with a mean particle size of 22.6 m and an appropriate amount of SiC