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The purpose of this study was to investigate the effects of titania addition on adhesion strength of silver colloids to glass substrate. Our results indicated that when the pH was adjusted to 10, the mixed slurry of titania and silver colloids was stable with no sign of settling at approximately 4 hr. After film deposition by doctor blade method and subsequent sintering treatment, the adhesion strength between silver film and glass substrate was measured by both ASTM D3359 and D4541 standards. The results showed positive correlation of adhesion strength to both the titania concentration and sintering temperature. The adhesion strength reached 7.0 MPa when we added 8 wt% titania (based on silver) and sintered the film at 320°C for 20 min. X-ray photoelectron spectroscopy data revealed that interdiffusion of Ti into both glass substrate and silver colloid might be responsible for adhesion enhancement. On the other hand, the electrical resistivity of films increased with titania addition. This fact implied that we need to compromise between these two properties when titania addition was used to improve adhesion between silver colloid and glass substrate. An empirical model was subsequently proposed to simulate the compromise between adhesion strength and electrical resistivity. [ABSTRACT FROM PUBLISHER]

The adhesion of silver colloids to a polyimide (PI) substrate was investigated in this study. This issue would be of concern when one tried to print electronic circuits on a flexible PI substrate. To enhance the adhesion between them, the PI surface was first roughened by using the sandblasting technique, and varying degrees of roughness were achieved using various sizes of alumina particles and various air pressures for sandblasting. The adhesion strength of silver colloids to the PI substrate after sintering was then measured according to both ASTM D4541 and ASTM 3359 standards. The results indicated that adhesion strength increased proportionally with surface roughness; however, this enhancement effect was lessened when the roughness was above 880 nm. Sintering temperature was also beneficial in increasing adhesion to the substrate; however, the electrical resistance of the silver colloids after sintering also increased with the degree of roughness. This implied that the packing of silver colloids was also affected by surface roughness. Consequently, values of surface roughness were optimal when adhesion strength and electrical resistivity were balanced. [ABSTRACT FROM PUBLISHER]

In this study, a simple thick-film humidity sensor was fabricated by coating wet-synthesized ZnO nanorods on screen-printing interdigitated electrodes. We investigated the influence of the coating procedure on the microstructure of ZnO nanorod films and thereby on humidity sensing. The experimental results revealed that the specific surface area (SSA) decreased and the average pore size (APS) increased with increasing the sintering time and the number of coating layer. The humidity response depended significantly on the pore properties of the ZnO nanorod films. By virtue of the incipient wetness analysis, it was found that the adsorption of water molecules on the ZnO surface led to the decrease in electrical resistance even though the ZnO was rod like, n-type semiconductor. While tuning the pore structure of the ZnO nanorod film, the thick-film humidity sensor might display near-linear response in the full range of 0%-100% relative humidity (RH). [ABSTRACT FROM AUTHOR]