Growth of Carbon Nanotubes on Carbon/Cobalt Films with Different sp 2

The need of barrier layer such as SiO2 for carbon nanotubes (CNTs) growth limits their performance in electronic applications. In this study, conductive carbon/metal (carbon/cobalt—C:Co) composite films with the same metal content, but different sp2/sp3 ratios, were deposited using dual-source filtered cathodic vacuum arc (FCVA) technique. Three different C:Co composite films were deposited at different temperatures; visible Raman spectroscopy indicates that the sp2-rich C:Co composite film forms at high temperature (500°C), and high-resolution transmission electron microscopy (HRTEM) shows the formation of conducting graphitic-like sp2 clusters and with Co nanoclusters embedded within them. Electrical measurement shows a significant decrease in film resistivity as sp2/sp3 ratio increases. CNTs were successfully grown on the composite films by plasma-enhanced vapor deposition (PECVD) approach. Scanning electron microscopy (SEM) shows minor effect on the density of CNTs by varying the sp2/sp3 ratio. The dependence of defect level of the as-grown CNTs is found to reduce as sp2/sp3 ratio increases

Development of a novel filtered cathodic vacuum arc deposition system for carbon metal nanocluster thin films

Carbon metal nanocluster (C:Me) films have been used to protect the metal nanoclusters from oxidation and enhance its properties, in the same time the incorporation of metal nanoclusters within the carbon thin film is also able to reduce the high compressive stress of the carbon film, improve its mechanical, electrical properties. However, the conventional deposition methods to synthesize C:Me nanoclusters film still have difficulties in controlling the density of metal nanoclusters, and the metal content, etc. Hence, a better deposition method is desired to meet these requirements. In this thesis, a novel Y-shaped magnetic filters and anti-Helmholtz focusing coil is specially designed and implemented on the filtered cathodic vacuum arc (FCVA) deposition system. By using the Y-bend FCVA deposition system, two streams of plasma can be generated simultaneously, which is able to deposit C:Me nanocluster film. The ways to control the microstructure and property have been explored, such as magnetic trap generated by the anti-Helmholtz focusing coil which can be used to control the metal cluster density, arc current and growth temperature which can affect the film microstructure. Other than the deposition parameters, influence of post treatment such as thermal and laser annealing has also been studied. In addition, the electrical, tribological properties and applications of carbon based thin film have also been investigated. This thesis also reports on the growth of carbon nanotubes (CNTs) on C:Me nanocluster films such as C:Co nanocluster, which can be used as carbon hybrid system. The C:Co nanocluster film deposited using a 500°C growth temperature shows electrical conducting behavior, which can be used to eliminate the use of insulating barrier layer used in conventional CNTs growth.DOCTOR OF PHILOSOPHY (EEE

Structural evolution of amorphous carbon films upon annealing

Currently, Amorphous Carbon (a-C) attracts a lot of attention for different mechanical and electronic applications. In this project, studies on the properties of amorphous carbon were made. Filtered Cathodic Vacuum Arc—FCVA technology was used to prepare single layer a-C films under different substrate bias conditions. As-deposited a-C films were also subjected to laser irradiation for post-treatment. Two important Raman features—D and G peak position and I(D)/I(G) that can be influenced by both deposition conditions and laser annealing were investigated by using Raman spectroscopy. Field emission properties as a function of deposition and post deposition treatments were studied in parallel plate configuration. The changing of sp2 content and sp2 cluster sizes of the annealed films as compared to as-deposited films was also studied by using Raman spectroscopy.Bachelor of Engineerin

Laurenidificin, a new brominated C15-acetogenin from the marine red alga Laurencia nidifica

A new brominated C_(15-acetogenin, namely, laurenidificin, was isolated from the marine red alga Laurencia nidifica. Its structure was determined on the basis of spectroscopic method

Perchlorate Removal using Granular Activated Carbon Supported Iron Compounds: Synthesis, Characterization and Reactivity

Synthesis and use of the iron compounds supported on granular activated carbon (ICs/GAC) have shown significant environmental implications for perchlorate (ClO4-) removal. ICs/GAC was synthesized via hydrolyzing FeSO4·7H2O on GAC, reduced by NaBH4 solution in polyethylene glycol 6000 and ethanol solution, dried in vacuum condition and exposed to air. Synthesized ICs/GAC was characterized using transmission electron micrograph (TEM), Brunauer-Emmett-Teller, X-ray photoelectron spectroscopy (XPS). ICs/GAC was determined to be containing a large amount of FeOHSO4, Fe2O3 and a small amount of zero-valent iron (ZVI) nanoparticles according to TEM and XPS measurements. Batch static kinetic tests showed that 97% of ClO4- was removed within 10 hr at 90°C and 86% of ClO4- was removed within 12 hr at 25°C, at ICs/GAC dosage of 20 g/L. The experimental results also showed that FeOHSO4 and Fe2O3 nanoparticles have the function of perchlorate adsorption and play important roles in ClO4- removal. The activation energy (Ea) was determined to be 9.56 kJ/mol

The Effect of Metal-Semiconductor Contact on the Transient Photovoltaic Characteristic of HgCdTe PV Detector

The transient photovoltaic (PV) characteristic of HgCdTe PV array is studied using an ultrafast laser. The photoresponse shows an apparent negative valley first, then it evolves into a positive peak. By employing a combined theoretical model of pn junction and Schottky potential, this photo-response polarity changing curves can be interpreted well. An obvious decreasing of ratio of negative valley to positive peak can be realized by limiting the illumination area of the array electrode. This shows that the photoelectric effect of Schottky barrier at metal-semiconductor (M/S) interface is suppressed, which will verify the correctness of the model. The characteristic parameters of transient photo-response induced from p-n junction and Schottky potential are extracted by fitting the response curve utilizing this model. It shows that the negative PV response induced by the Schottky barrier decreases the positive photovoltage generated by the pn junction

Contribution of amide-based coagulant polyacrylamide as precursors of haloacetamides and other disinfection by-products

Coagulation is a widespread method of drinking water treatment. Coagulation can mitigate the formation of disinfection by-products (DBPs) through removing their precursors. Here we report that the amide-based organic polymer coagulants polyacrylamide (PAM) and its monomer acrylamide (AM) can serve as a source of HAcAm and other DBPs including trihalomethanes (THMs) and haloacetonitriles (HANs) during chlor(am)ination. The impact of the key experimental parameters, including reaction time, Cl2 or NH2Cl dose, pH and initial bromide concentration on the formation of DBPs was investigated. Furthermore, the major reaction pathways for AM transformation and DBP formation during chlor(am)ination are proposed and include N-chlorination, addition, and substitution. Jar tests demonstrated that coagulation by alum coupled with PAM achieved greatest removal of DOC and UV254, compared with alum and PAM alone. Treatment with PAM didn’t significantly promote the formation of THMs and HANs during post-chlorination, indicating that the PAM residual hardly contributes to THM and HAN formation. However, coagulation by applying alum salt and PAM increased total HAcAm concentrations by 2.2–3.1 μg/L at the higher PAM dose (2.0 mg/L), compared with alum alone. Therefore, the contribution of PAM to the formation of HAcAm cannot be ignored. The results highlight that the generation of secondary pollutants from the amide-based engineered organic polymer coagulants in drinking water should be considered; that is, they can adversely affect water quality because of their ability to enhance DBPs generated during downstream disinfection. Accordingly, the understanding of the stability and reactivity of PAM in the presence of disinfectants could help to better evaluate their contribution to the formation of HAcAms, THMs, and HANs, which has important implications for their environmental fate, transport, and responsible applications

Formation and estimated toxicity of trihalomethanes, haloacetonitriles, and haloacetamides from the chlor(am)ination of acetaminophen

The occurrence of pharmaceuticals and personal care products (PPCPs) in natural waters, which act as drinking water sources, raises concerns. Moreover, those compounds incompletely removed by treatment have the chance to form toxic disinfection byproducts (DBPs) during subsequent disinfection. In this study, acetaminophen (Apap), commonly used to treat pain and fever, was selected as a model PPCP. The formation of carbonaceous and nitrogenous DBPs, namely trihalomethanes, haloacetonitriles, and haloacetamides, during chlor(am)ination of Apap was investigated. Yields of chloroform (CF), dichloroacetonitrile (DCAN), dicholoacetamide (DCAcAm), and tricholoacetamide (TCAcAm), during chlorination were all higher than from chloramination. The yields of CF continuously increased over 48 h during both chlorination and chloramination. During chlorination, as the chlorine/Apap molar ratios increased from 1 to 20, CF yields increased from 0.33 ± 0.02% to 2.52 ± 0.15%, while the yields of DCAN, DCAcAm and TCAcAm all increased then decreased. In contrast, during chloramination, increased chloramine doses enhanced the formation of all DBPs. Acidic conditions favored nitrogenous DBP formation, regardless of chlorination or chloramination, whereas alkaline conditions enhanced CF formation. Two proposed formation mechanisms are presented. The analysed DBPs formed during chlorination were 2 orders of magnitude more genotoxic and cytotoxicity than those from chloramination