The effect of calcining temperature on gas sensitivity and resistance in wet air was observed with elements of Sn02 thick film. The results were interpreted as a function of the crystallite size. As the crystallite size reduced, the sensitivity to H 2 gas enhanced at temperatures lower than 300°C, but at those higher than 350°C it did not. The temperatures showing the minimum resistance in air and the maximum sensitivity to H 2 gas decreased with reduction of the crystallite size. The temperature variations were assigned to the change of the activation energies of the oxygen adsorbates. It is suggested that the decrease of activation energies is one of the reasons for the sensitivity enhancement with the fine powder.
Indium tin oxide (ITO) films (0.3 μm thick), with a doping level of 28 mol% SnO2, were prepared by a radio frequency magnetron sputtering mehthod. The effects of postannealing on the microstructure and the electrical properties of the ITO films were investigated. The as‐sputtered film showed an amorphous structure, whereas the films annealed at 350° and 510°C exhibited crystalline structures with grain sizes of 0.12 and 0.14 μm, respectively. Examination by TEM showed that the postannealing treatment induced SnO2 precipitates along the grain boundaries. The resistivity increased with increasing postannealing temperatures. The mobility of carriers appears to be responsible for the resistivity increase in these specimens. The mobility change is discussed in connection with the SnO2 precipitates.
The purpose of this study is to compare and analyze physical properties of different fluorescent fabrics and retroreflective materials to determine their compliance to international standard for high-visibility warning clothing. Four fluorescent fabrics were selected for the study: a PET 71%/Cotton 23%/PU 6% fabric used in public road cleaner uniforms in Korea (S1), an ISO-compliant Japan-made PET 65%/Cotton 35% + conductive fabric (S2), and a randomly selected Korean-made PET 100% fabric for adults (S3) and children (S4). Selected samples were evaluated on their seven criteria in ISO 20471. Subsequently, luminance and retroreflective properties of four retroreflective materials were compared: a 3M (USA) plain sample (R1), a rectangular-patterned sample made by ‘R’ company (Korea) (R2), a plain sample also by ‘R’ (R3), and a random plain sample from a marketplace in Korea (R4). As a result, S1 was the most similar to ISO-compliant S2 and moisture regain could be improved by adjusting the cotton ratio or surface finishing. However, S3 and S4 seemed less suitable. Second, two bead type (R1, R4) and two prism type (R2, R3) retroreflective materials showed luminance in the order of R4 > R2 ≥ R1 > R3. General retroreflective properties and post-5-condition retroreflective properties of all four samples were ISO-compliant, and the retroreflective property at observation angle of 12′ and incidence angle of 5° of R2, R3, and R4 against R1 ranged between 81.4% and 158.4%. Despite the variance, all four samples were ISO-compliant and suggest that R2, R3, and R4 are possible materials for export.
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