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Part A: The preliminary investigation of the thermal and electrical behaviour of thin metal films gives evidence, Part I, that several mechanisms are responsible for the change of resistance as the temperature increases from room temperature to 500°C. Firstly, there appears grain growth giving a characteristic decrease in resistance. Secondly, the formation of agglomerates upon the continued growth of grains; especially for the thinner Al and Cr films. This effect tends to increase the resistance and a mathematical model is proposed to explain the results qualitatively. Thirdly, the occurrence of what appeared to be an electromigration effect. This latter point provided the incentive for a study on the effects of electromigration in thin aluminum film, Part II. The results of this study are comparable to those obtained by other workers, except that the interpretation for the direction of electromigration in Al is reversed. One possible explanation for the difference in the direction of migration could be due to the interpretation of marker motion. A mathematical model is also proposed for electromigration, in which both the effects due to the applied electric field and the electrons collision with the ions have been taken into consideration. It was found that the effect due to electrons collision with the ions upon the migration of ions could be expressed in terms of an exponential function of the square of the electron to ion collision relaxation time. / Thesis / Master of Engineering (ME)

This study reports the synthesis of graphene by oxidizing graphite to graphite oxide using H2SO4 and KMnO4 and reducing graphene oxide to graphene by using NaBH4. Graphene was then characterized using FT-IR, TEM, AFM, XRD, Raman spectroscopy and solid state NMR. Nafion-Graphene in combination with a mercury film electrode, bismuth film electrode and antimony film electrode was used as a sensing platform for trace metal analysis in 0.1 M acetate buffer (pH 4.6) at 120 s deposition time, using square-wave anodic stripping voltammetry (SWASV). Detection limits were calculated using 3σblank/slope. For practical applications recovery studies was done by spiking test samples with known concentrations of metal ions and comparing the results to inductively coupled plasma mass spectrometry (ICPMS). This was then followed by real sample analyses.

This study reports the synthesis of graphene by oxidizing graphite to graphite oxide using H2SO4 and KMnO4 and reducing graphene oxide to graphene by using NaBH4. Graphene was then characterized using FT-IR, TEM, AFM, XRD, Raman spectroscopy and solid state NMR. Nafion-Graphene in combination with a mercury film electrode, bismuth film electrode and antimony film electrode was used as a sensing platform for trace metal analysis in 0.1 M acetate buffer (pH 4.6) at 120 s deposition time, using square-wave anodic stripping voltammetry (SWASV). Detection limits were calculated using 3σblank/slope. For practical applications recovery studies was done by spiking test samples with known concentrations of metal ions and comparing the results to inductively coupled plasma mass spectrometry (ICPMS). This was then followed by real sample analyses.

Magister Scientiae - MSc (Dept. of Chemistry) / This study reports the synthesis of graphene by oxidizing graphite to graphite oxide using H2SO4 and KMnO4 and reducing graphene oxide to graphene by using NaBH4. Graphene was then characterized using FT-IR, TEM, AFM, XRD, Raman spectroscopy and solid state NMR. Nafion-Graphene in combination with a mercury film electrode, bismuth film electrode and antimony film electrode was used as a sensing platform for trace metal analysis in 0.1 M acetate buffer (pH 4.6) at 120 s deposition time, using square-wave anodic stripping voltammetry (SWASV). Detection limits were calculated using 3σblank/slope. For practical applications recovery studies was done by spiking test samples with known concentrations of metal ions and comparing the results to inductively coupled plasma mass spectrometry (ICPMS). This was then followed by real sample analyses. / South Africa

Magister Scientiae - MSc / In this study multilayer graphene nanosheets was synthesize by oxidizing graphite to graphene oxide using H2SO4 and KMnO4 followed by reduction of graphene oxide to graphene using NaBH4. The graphene nanosheets were characterized by Fourier Transform Infrared (FTIR) and Raman spectroscopy, high resolution transmission electron microscopy (HRTEM), Scanning electron microscopy (SEM) and X-ray diffraction (XRD). HRTEM images showed that the multilayer graphene were obtained. The graphene was immobilized directly onto a glassy carbon electrode using the drop coating technique followed by the in situ deposition of mercury, bismuth or antimony thin films to afford graphene modified glassy carbon metal film electrodes (Gr-GC-MEs). The experimental parameters (deposition potential, deposition time, rotation speed, frequency and amplitude) were optimized, and the applicability of the modified electrode was investigated towards the individual and simultaneous determination of Zn2+, Cd2+ and Pb2+ at the low concentration levels (μg L-1) in 0.1 M acetate buffer (pH 4.6) using square wave anodic stripping voltammetry (SWASV). The detection limits values for the Gr-GC-HgE was 0.08, 0.05 and 0.14 μg L-1 for Zn2+, Cd2+ and Pb2+, respectively. The Gr-GC-BiE the detection limits for was 0.12, 0.22 and 0.28 μg L-1 for Zn2+, Cd2+ and Pb2+ while the detection limits for the Gr-GC-SbE was 0.1, 0.3 and 0.3 μg L-1 for Zn2+, Cd2+ and Pb2+, respectively. A Gr-GCE prepared without any binding agents or metal film had detection limits for Zn2+, Cd2+ and Pb2+ of 3.9, 0.8 and 0.2 μg L-1 for Zn2+, Cd2+ and Pb2+. Real sample analysis of which was laboratory tap water was performed using the Gr-GCMEs. Only Gr-GC-HgE was sensitive enough to detect metal ions in the tap water samples at the 3ppb level whereas, the GC-BiE and GC-SbE detected the metal ions at the 10 μg L-1 to 30 μg L-1 level.