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The laboratory researches about the inhibiting effect of citric acid on the flotation performance of serpentine activated by Cu2+ and Ni2+ were carried out through micro flotation tests, zeta potential measurements, collector adsorption capacity measurements and solution chemistry analysis. The flotation results showed that Cu2+ and Ni2+ could remarkably activate the flotation of serpentine when the pH value was more than 6, however, this activation could be effectively weakened by adding citric acid. Zeta potential measurement and adsorption capacity measurement indicated that the presence of citric acid could prevent the adsorption of Cu2+ and Ni2+, and therefore reduce the adsorption amount of potassium butyl xanthate on serpentine surface. Furthermore, solution chemical analysis of the flotation system showed that copper hydroxide Cu(OH)2(s) and the nickel hydroxide Ni(OH)2(s) were the main component in the pH range of 9 to 10, which adsorbed onto serpentine surface and made it activated; while the citric acid could effectively prohibit the formation of these metal hydroxide in slurry so as to inhibit the activation impact. [ABSTRACT FROM AUTHOR]

An innovative fabrication method to produce a macroporous Si surface by employing an anodic aluminium oxide (AAO) nanopore array layer as an etching template is presented. Combining AAO with a reactive ion etching (RIE) processes, a homogeneous and macroporous silicon surface can be effectively configured by modulating AAO process parameters and alumina film thickness, thus hopefully replacing conventional photolithography and electrochemical etch methods. The hybrid process integration is considered fully CMOS compatible thanks to the low-temperature AAO and CMOS processes. The gas-sensing characteristics of 50 nm TiO2 nanofilms deposited on the macroporous surface are compared with those of conventional plain (or non-porous) nanofilms to verify reduced response noise and improved sensitivity as a result of their macroporosity. Our experimental results reveal that macroporous geometry of the TiO2 chemoresistive gas sensor demonstrates 2-fold higher (∼33%) improved sensitivity than a non-porous sensor at different levels of oxygen exposure. In addition, the macroporous device exhibits excellent discrimination capability and significantly lessened response noise at 500 °C. Experimental results indicate that the hybrid process of such miniature and macroporous devices are compatible as well as applicable to integrated next generation bio-chemical sensors. [ABSTRACT FROM AUTHOR]