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| Author(s): |
Carlos Antonio Neves
Total Authors: 1
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| Document type: | Master's Dissertation |
| Press: | São Paulo. |
| Institution: | Universidade de São Paulo (USP). Conjunto das Químicas (IQ e FCF) (CQ/DBDCQ) |
| Defense date: | 2000-10-02 |
| Examining board members: |
Claudimir Lúcio do Lago;
Denise Freitas Siqueira Petri;
Jarbas José Rodrigues Rohwedder
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| Advisor: | Claudimir Lúcio do Lago |
| Abstract | |
This dissertation describes the development of devices based on separated-electrode piezoelectric quartz crystals (ESPC) to study surface modifications. This is accomplished by monitoring the oscillation frequency and impedance spectrum of the crystal in the cell. A TTL oscillator coupled to a frequency counter and a microcomputer interface is used for monitoring the oscillation frequency. A dynamic link library and HP-VEE 4.0 programs were developed to control the interface. Other programs were also developed to acquire the impedance spectra from a spectrum analyzer by using the GPIB protocol. The first device (DFD) is intended to study deposited films. It is made in Plexiglas, with brass electrodes positioned at a few tenths of millimeters from the crystal surface, and a thermostatic water jacket. The second device (DMS) is similar to the first one, but allows the use of corrosive reagents in the gas phase for surface modification. The performance of both devices was evaluated and the results showed good agreement between the deposited mass and the one predicted by Sauerbrey equation. The DFD was used for offline monitoring of the crystal surface modification by N-[3-(triethoxysilyl)propyl]-1,2-ethanediamine followed by iodoacetic acid. The results show evidences of mass and viscoelastic variations of the film. The DMS was used for on-line monitoring during surface modification with trimethylchlorosilane (TMCS) and dimethyldichlorosilane (DMDCS). Due to the monolayer formed by TMCS, no significant frequency variation could be observed. On the other hand, the polymerization of DMDCS could be monitored. (AU) | |