Ip Kit Man = 準一維的硒化鋅納米結構的光致發光研究 / 葉潔雯. / Thesis (M.Phil.)--Chinese University of Hong Kong, 2004. / Includes bibliographical references (leaves 68-71). / Text in English; abstracts in English and Chinese. / Ip Kit Man = Zhun yi wei de xi hua xin na mi jie gou de guang zhi fa guang yan jiu / Ye Jiewen. / ACKNOWLEDGEMENTS --- p.i / ABSTRACT --- p.ii / TABLE OF CONTENTS --- p.vi / LIST OF TABLE --- p.vii / LIST OF FIGURES --- p.viii / Chapter Chapter1 --- Introduction / Chapter 1.1 --- Motivation --- p.1 / Chapter 1.2 --- Literature review --- p.2 / Chapter 1.3 --- Our study --- p.4 / Chapter 1.4 --- Growth conditions --- p.4 / Chapter Chapter2 --- Background / Chapter 2.1 --- Basic principle of PL --- p.6 / Chapter 2.2 --- Theories of excitations in semiconductor / Chapter 2.2.1 --- Bandgap and temperature effect of ZnSe --- p.8 / Chapter 2.2.2 --- Structure of ZnSe --- p.13 / Chapter 2.3 --- Surface effects --- p.16 / Chapter 2.4 --- Gas -Surface Interaction --- p.20 / Chapter Chapter 3 --- Experimental Procedures / Chapter 3.1 --- Setup of PL Spectroscopy --- p.21 / Chapter 3.2 --- Passivation and separation of ZnSe nanostructures --- p.26 / Chapter Chapter 4 --- Results and Discussions / Chapter 4.1 --- Analysis of ZnSe/Si nanostructures / Chapter 4.1.1 --- "Morphology, structure and separation of as-grown ZnSe/Si nanostructures" --- p.30 / Chapter 4.1.2 --- Temperature dependent PL of as-grown and very low density ZnSe/Si nanostructures --- p.33 / Chapter 4.1.3 --- Temperature dependent PL of ZnSe/Al203 nanowires --- p.41 / Chapter 4.1.4 --- Growth conditions dependence on PL --- p.44 / Chapter 4.1.4a --- PL result comparison: ZnSe grown on 3 different substrate --- p.45 / Chapter 4.1.4b --- PL result comparison: Silver and gold catalyst --- p.45 / Chapter 4.2 --- Analysis of the ammonium sulfide treated samples / Chapter 4.2.1 --- XPS results of ammonium sulfide treated samples --- p.47 / Chapter 4.2.2 --- Relationship between immersion time and enhancement factors of PL intensity --- p.49 / Chapter 4.3 --- Analysis of effects in PL of ZnSe/Si nanostructures in different gas ambients --- p.53 / Chapter Chapter 5 --- Conclusions --- p.66 / References --- p.68

Kwong Kwan Wai = 氧化鋅基低維納米結構之生長與分析 / 鄺筠慧. / Thesis (M.Phil.)--Chinese University of Hong Kong, 2004. / Includes bibliographical references (leaves 75-79). / Text in English; abstracts in English and Chinese. / Kwong Kwan Wai = Yang hua xin ji di wei na mi jie gou zhi sheng zhang yu fen xi / Guang Yunhui. / Acknowledgement --- p.i / Abstract --- p.ii / 摘要 --- p.iii / Table of Contents --- p.iv / List of Figures --- p.vii / Chapter Chapter 1 --- Introduction --- p.1 / Chapter Chapter 2 --- Background --- p.3 / Chapter Chapter 3 --- Instrumentation --- p.6 / Chapter 3.1 --- Tube furnace system --- p.6 / Chapter 3.2 --- X-ray Diffraction (XRD) --- p.8 / Chapter 3.3 --- Scanning Electron Microscopy (SEM) --- p.9 / Chapter 3.4 --- Transmission Electron Microscopy (TEM) --- p.12 / Chapter 3.4.1 --- General Review --- p.12 / Chapter 3.4.2 --- Low-magnification imaging --- p.14 / Chapter 3.4.3 --- Transmission electron diffraction (TED) --- p.14 / Chapter 3.4.4 --- High-resolution electron microscopy (HREM) --- p.15 / Chapter 3.4.5 --- Experimental --- p.15 / Chapter Chapter 4 --- Oxygen partial pressure effect on the morphology of ZnO nanostructures --- p.17 / Chapter 4.1 --- Introduction --- p.17 / Chapter 4.2 --- Experimental --- p.17 / Chapter 4.3 --- Results --- p.19 / Chapter 4.3.1 --- SEM study for general morphology --- p.21 / Chapter 4.3.2 --- TEM study for detailed microstructures of the tetrapods and the nanocombs --- p.28 / Chapter 4.3.2.1 --- Tetrapods --- p.28 / Chapter 4.3.2.2 --- Nanocombs --- p.29 / Chapter 4.4 --- Discussions --- p.34 / Chapter 4.4.1 --- Thermal reduction and oxidation to form ZnO --- p.34 / Chapter 4.4.2 --- Vapor-Solid (VS) growth mechanism of low-dimensional nanostructures --- p.34 / Chapter 4.4.3 --- The oxygen partial pressure effect on the morphology of the ZnO nanostructures --- p.35 / Chapter 4.4.4 --- Transition from tetrapod to nanocomb --- p.36 / Chapter 4.4.5 --- Decreasing size effect --- p.39 / Chapter Chapter 5 --- Self-assembly of periodical ZnO/C multilayers on Zn nanowire --- p.40 / Chapter 5.1 --- Introduction --- p.40 / Chapter 5.2 --- Experimental --- p.42 / Chapter 5.3 --- Results and Discussion --- p.46 / Chapter 5.3.1 --- Freshly synthesized Zn nanowires --- p.46 / Chapter 5.3.2 --- Introducing carbon into the Zn nanowires一Solid phase diffusion --- p.50 / Chapter 5.3.3 --- Introducing carbon into the Zn nanowires一Gas phase reaction --- p.52 / Chapter 5.3.3.1 --- Diffusion of the gas molecules through the ZnO sheath to the Zn/ZnO interface --- p.60 / Chapter 5.3.3.2 --- Chemical reaction(s) --- p.60 / Chapter 5.3.3.3 --- Phase separation of ZnO and C --- p.61 / Chapter 5.3.3.4 --- Self-organized multilayers --- p.62 / Chapter 5.3.3.5 --- Factors affecting SAM formation --- p.64 / Chapter 5.3.3.5.1 --- Crystallinity of original oxide sheath (series A) --- p.64 / Chapter 5.3.3.5.2 --- Temperature (series B) --- p.66 / Chapter 5.3.3.5.3 --- Gas molecules (series C) --- p.69 / Chapter Chapter 6 --- Conclusions --- p.72 / Appendix --- p.74 / References --- p.75

Liu Zhuang = 硒化鋅准一維納米結構的形貌和陰極射線致發光的研究 / 劉壯. / Thesis (M.Phil.)--Chinese University of Hong Kong, 2004. / Includes bibliographical references (leaves 60-63). / Text in English; abstracts in English and Chinese. / Liu Zhuang = Xi hua xin zhun yi wei na mi jie gou de xing mao he yin ji she xian zhi fa guang de yan jiu / Liu Zhuang. / ABSTRACT --- p.i / ACKNOWLEDGMENTS --- p.iii / TABLE OF CONTENTS --- p.iv / LIST OF TABLES --- p.vi / LIST OF FIGURES --- p.vii / Chapter 1. --- Introduction --- p.1 / Chapter 1.1 --- Synthesizing quasi one-dimensional nanostructures of ZnSe using MOCVD --- p.1 / Chapter 1.2 --- Well-aligned nanostructures and heterocrystalline nanorods --- p.2 / Chapter 1.3 --- Advantages of CL in studying nanostructures --- p.3 / Chapter 2. --- Experimental conditions and procedures --- p.7 / Chapter 2.1 --- Information on the samples --- p.7 / Chapter 2.2 --- SEM and CL setting --- p.9 / Chapter 2.3 --- CL calibration --- p.10 / Chapter 3. --- Experimental results and data analysis --- p.14 / Chapter 3.1 --- SEM results and discussion --- p.14 / Chapter 3.1.1 --- SEM studies helping to find the optimal growth condition --- p.14 / Chapter 3.1.2 --- Morphological studies --- p.18 / Chapter 3.1.3 --- The growth direction of well-aligned nanostructure --- p.22 / Chapter 3.1.4 --- Discussion of the growth mechanisms of the nanostructures based on the morphological studies --- p.28 / Chapter 3.2 --- CL results and discussion --- p.34 / Chapter 3.2.1 --- CL spectra of nanostructures of different morphologies --- p.34 / Chapter 3.2.2 --- CL images for studying of distribution of localized radiative centers --- p.40 / Chapter 3.2.3 --- CL studies of a single nanorod --- p.44 / Chapter 3.2.3.1 --- Room temperature CL studies of a single nanorod --- p.44 / Chapter 3.2.3.2 --- Liquid Helium temperature (4.5 K) CL studies of a single nanorod --- p.50 / Chapter 4. --- Conclusions --- p.59 / Reference --- p.60

Hung Ngar Chun = 氧化鋅納米棒的生長和表徵 / 洪雅真. / Thesis (M.Phil.)--Chinese University of Hong Kong, 2004. / Includes bibliographical references. / Text in English; abstracts in English and Chinese. / Hung Ngar Chun = Yang hua xin na mi bang de sheng zhang he biao zheng / Hong Yazhen. / Acknowledgements --- p.i / Abstract --- p.ii / 摘要 --- p.iii / List of Tables --- p.iv / List of Figures --- p.v / Table of contents --- p.vii / Chapter Chapter 1 --- Introduction / Chapter 1.1. --- Objectives --- p.1-1 / Chapter 1.2. --- Background --- p.1-1 / Chapter 1.2.1. --- Nanomaterials --- p.1-1 / Chapter 1.2.1.1. --- From three-dimensional to one-dimensional --- p.1-1 / Chapter 1.2.1.2. --- One-dimensional nanomaterials --- p.1-2 / Chapter 1.2.2. --- Characteristics and potential applications --- p.1-2 / Chapter 1.2.3. --- Growth mechanisms --- p.1-4 / Chapter 1.2.3.1. --- The VLS growth --- p.1-4 / Chapter 1.2.3.2. --- The VS growth --- p.1-5 / Chapter 1.2.4. --- ZnO --- p.1-6 / Chapter 1.2.4.1. --- Characteristics and potential applications --- p.1-6 / Chapter 1.2.4.2. --- Recent works performed by the others --- p.1-7 / Chapter 1.2.4.2.1. --- Different fabrication systems --- p.1-7 / Chapter 1.2.4.2.2. --- Different morphologies and shapes --- p.1-8 / Chapter 1.3. --- Our work --- p.1-9 / Chapter 1.3.1. --- Advantages of our fabrication method --- p.1-9 / Chapter 1.4. --- Thesis layout --- p.1-9 / References --- p.1-10 / Figures --- p.1-13 / Tables --- p.1-14 / Chapter Chapter 2 --- Methodology and Experiments / Chapter 2.1. --- Introduction --- p.2-1 / Chapter 2.2. --- The setup --- p.2-1 / Chapter 2.2.1. --- Preparation of substrate --- p.2-1 / Chapter 2.2.2. --- Chamber pressure and gas flow rate --- p.2-2 / Chapter 2.2.3. --- Heating profile --- p.2-2 / Chapter 2.3. --- The two important growth parameters --- p.2-3 / Chapter 2.3.1. --- Substrate compositions --- p.2-3 / Chapter 2.3.2. --- Temperature --- p.2-3 / Chapter 2.4. --- Methods of characterizations --- p.2-4 / Chapter 2.4.1. --- Morphology --- p.2-4 / Chapter 2.4.1.1. --- SEM --- p.2-4 / Chapter 2.4.1.2. --- TEM --- p.2-5 / Chapter 2.4.2. --- Phases and Microstructures --- p.2-5 / Chapter 2.4.2.1. --- XRD --- p.2-5 / Chapter 2.4.2.2. --- HRTEM --- p.2-5 / Chapter 2.4.3. --- Cathodoluminescence --- p.2-6 / References --- p.2-7 / Figures --- p.2-8 / Chapter Chapter 3 --- Results / Chapter 3.1. --- Introduction --- p.3-1 / Chapter 3.2. --- General Morphologies --- p.3-1 / Chapter 3.3. --- Microstructural analysis --- p.3-2 / Chapter 3.4. --- Samples sintered using substrate of different composition --- p.3-2 / Chapter 3.5. --- Samples sintered at different temperatures --- p.3-4 / Chapter 3.6. --- The cathodoluminescence of the ZnO nanorods --- p.3-4 / References --- p.3-6 / Figures --- p.3-7 / Chapter Chapter 4 --- Discussions / Chapter 4.1. --- Introduction --- p.4-1 / Chapter 4.2. --- Proposed growth model --- p.4-1 / Chapter 4.2.1. --- Chemical reactions --- p.4-1 / Chapter 4.2.2. --- Justification on the effect of residue oxygen and leakage --- p.4-2 / Chapter 4.2.3. --- Justification on the possibility of VLS growth --- p.4-3 / Chapter 4.2.4. --- Coarsening mechanisms --- p.4-3 / Chapter 4.2.4.1. --- Oswald Ripening --- p.4-4 / Chapter 4.2.4.2. --- Preferential growth direction --- p.4-4 / Chapter 4.3. --- The effects of substrate composition --- p.4-5 / Chapter 4.3.1. --- Roles of Si and Si02 --- p.4-5 / Chapter 4.4. --- The effects of temperature --- p.4-6 / Chapter 4.4.1. --- Range of sintering temperature --- p.4-6 / Chapter 4.4.2. --- Diameter of the rods --- p.4-7 / Chapter 4.4.3. --- Luminescence behavior --- p.4-7 / References --- p.4-10 / Figures --- p.4-11 / Chapter Chapter 5 --- Conclusions and future works

El presente trabajo de investigación tuvo como objetivo de estudio realizar una evaluación de la resistencia a la corrosión mediante el ensayo de niebla salina en acero estructural A36 recubiertas de pintura alquídica incorporando nanopartículas de óxido de zinc. Se utilizaron nano ZnO industriales, las cuales fueron caracterizadas por espectroscopia infrarroja con transformada de Fourier (FTIR), espectroscopia UVvisible, microscopía electrónica de barrido (SEM) y difracción de rayos X (DRX). Se realizó la incorporación de nanopartículas de óxido de zinc en la pintura alquídica en porcentajes en peso de 0,5; 1,5 y 3,0. La evaluación de la incorporación de estás nanopartículas sobre el sustrato metálico se realizó por FTIR, SEM-EDS y DRX. Finalmente, se realizó el ensayo de corrosión acelerada de niebla salina, con una exposición de solución salina de NaCl al 5.0%w. Los resultados de la caracterización de las nano ZnO indicaron que las nanopartículas muestran la estructura cristalina hexagonal tipo wurtzita, sensibilidad a la luz UV-vis con banda característica en el espectro ultravioleta, y en el caso del FTIR mostrón una manda característica en el rango de 400-500cm-1. La incorporación de nano-ZnO de concentración en la pintura alquídica de 0,5% w mostró un mejor aspecto superficial a comparación de 1,5 y 3,0 %w que mostraron un aspecto más rugoso. La mayor resistencia a la corrosión la mostró la concentración de 1.5% w de nano-ZnO en el ensayo de corrosión acelerada de niebla salina. / The objective of this research was to evaluate corrosion resistance by the salt spray test in A36 structural steel coated with alkyd paint incorporating zinc oxide nanoparticles. Industrial ZnO nano were used, which were characterized by infrared spectroscopy with Fourier transform (FTIR), UV-visible spectroscopy scanning electron microscopy (SEM) and X-ray diffraction (XRD). The incorporation of zinc oxide nanoparticles in the alkyd paint was performed in percentages by weight of 0.5; 1.5 and 3.0. The evaluation of the incorporation of these nanoparticles on the metallic substrate was performed by FTIR, SEM-EDS and XRD. Finally, the salt spray accelerated corrosion test was performed, with a 5.0%w NaCl saline solution. The results of the nano-ZnO characterization indicated that the nanoparticles show the wurtzite-type hexagonal crystal with structure, with, sensitivity to UV-vis light with characteristic band in the ultraviolet spectrum, and in the case of FTIR showed a characteristic band in the range of 400-500cm-1. The incorporation of nano-ZnO concentration in alkyd paint 0.5%w showed a better surface appearance compared to 1.5 and 3.0%w which showed a more rough appearance. The highest corrosion resistance was shown by the concentration of 1.5% w of nano-ZnO in the accelerated salt spray corrosion test. / Tesis

In the hydrometallurgical processing route for primary production of zinc, one of the most significant impurities in terms of cost of processing is iron. In the last two decades, electroplating of steel sheet with alloys such as zinc/iron has seen considerable industrial development. In this process, there is an 'anomalous co-deposition', in which zinc is deposited at a higher rate than iron, even though it is more cathodic in the electrochemical series.In the 1980's research papers reported high current efficiencies for zinc electroplating in the presence of a comparable concentration of iron. It is of interest to the zinc industry to know conditions under which zinc could be electrowon efficiently without prior separation of iron. The chief aim of the current project was to obtain data which would allow evaluation of a zinc electrowinning step carried out in the presence of iron. It was necessary to understand the robustness of such a process towards variations in parameters such as electrolyte composition and purity, temperature, and current density. Means of producing smooth, strippable deposits at high current efficiencies also required evaluation. In order to electrolyse high iron solutions at high current efficiency, it is necessary to introduce a separator into the cell, to prevent cycling of iron oxidation at the anode and reduction at the cathode. The focus of this project was on the cathode process, particularly the determination of factors influencing morphology and current efficiency. Experiments involved modifications of some cells typically used in studies of conventional zinc electrowinning. A range of techniques for morphological studies and for electrochemical tets was evaluated for application to this problem, as well as to studies of conventional zinc electrowinning operations / Doctor of Philosophy (PhD)

Globally, low zinc (Zn) soils are widespread, but one of the largest expanses of such soils is in south west Australia (WA). Early Zn research in the region determined how much fertiliser Zn was required for profitable production of spring wheat (Triticium aestivum L.) and subterranean clover (Trifolium subterraneanum L), the major crop and pasture species at the time. The research showed that Zn sulfate and ZnO were equally effective Zn fertilisers, but ZnO was cheaper and so was widely used. The research indicated that in the year of application, depending on soil type, between 0.5-1.5 kg Zn/ha provided adequate Zn for the production of wheat and subterranean clover. The length of time that a single application of Zn fertiliser remains fully effective in maintaining the production of crops and pasture in future years (residual value; (RV)) had not been determined. This knowledge of the RV of Zn fertilisers is required for soils of WA. The experiments that measured the RV of fertiliser Zn for spring wheat and subterranean clover form the bulk of this thesis. The soils in the region were also initially acutely phosphorus (P) deficient requiring the application of fertiliser P for profitable production. Single superphosphate was the P fertiliser initially used. It was manufactured locally using phosphate rock imported from Nauru and Christmas Islands. This phosphate rock also contained much Zn, and the single superphosphate manufactured from it contained 400-600 mg Zn/kg. At amounts of application needed to provide adequate P, the Zn-contaminated superphosphate also supplied about 90 g Zn/ha. Therefore, early field experiments measured the RV of ZnO applied to soil when single superphosphate was applied annually at >150 kg/ha. In these experiments, the RV of Zn was measured when different amounts of fertiliser nitrogen (N) was applied. This was because it has recently been very profitable to apply fertiliser N to wheat crops, which greatly increased grain yields and so may have increased the demand for Zn, thereby probably decreasing the RV of the original ZnO application. In these experiments, there were many nil-Zn plots. In subsequent years, freshly-applied ZnO amounts were applied to measure the RV of the original ZnO treatments relative to the fresh Zn treatment. No Zn deficiency was detected for up to 23 years after applying ZnO while applying superphosphate at >150 kg/ha per year and for all amounts of N applied. Subsequently cheap imported DAP fertiliser was used for wheat crops instead of locally produced Zn-contaminated single superphosphate and urea. The imported DAP contained about 50 mg Zn/kg (1/12 that of single superphosphate). This new fertiliser strategy induced Zn deficiency in many wheat crops. This led to further field studies to determine the RV of ZnO fertiliser when DAP was applied. The experiments also included 2 Zn-contaminated single superphosphate treatments. In one, no ZnO was applied, and superphosphate was applied at >150 kg/ha per year to match the amount of P applied as DAP to the other treatments. The other treatment was the same, except 1.5 kg/ha Zn as ZnO was applied in the first year only. In subsequent years, freshly-applied ZnO amounts were applied to measure the RV of the original ZnO treatments relative to the fresh Zn treatment. Relative to freshly-applied Zn in each year, the RV of the original ZnO treatments decreased as the length of time that the Zn was in contact with soil increased. However, the rate of decline in the RV was also found to differ with soil type, and was affected by soil pH, clay and organic carbon content of soil, and in alkaline soils with the calcium carbonate content of soil. Parallel glasshouse studies measured the RV of Zn, as Zn sulfate, for wheat and subterranean clover, using many soils from WA and other Australian States. The glasshouse studies also showed that the rate of decline in the RV of the original Zn application varied markedly with soil type and was strongly influenced by soil pH, clay and organic carbon content of soil, and in the alkaline soils, the amount of calcium carbonate in soil. In the above studies, the RV of fertiliser Zn was measured relative to freshly-applied Zn using yield of plants (shoots and grain for wheat, shoots for clover), Zn content in shoots and grain, and soil test Zn using the ammonium oxalate and DTPA procedures. In addition, Zn concentration in young tissue and rest of shoots (glasshouse studies) and young tissue and whole shoots (field studies) was measured, and Zn concentration related to 90 % of the maximum yield (critical Zn in plant parts) was determined. The studies showed that the DTPA soil test procedure, together with soil pH, and clay and organic matter content of soil, was an accurate prognostic test for indicating when Zn deficiency was likely in the next clover or wheat crop. The study confirmed that young tissue (youngest fully expanded leaves) provided critical plant test values for diagnosing Zn deficiency in plants. The plant and soil tests for Zn are now used by commercial soil and tissue testing laboratories. When Zn deficiency was diagnosed early in field grown wheat, Zn sprays can be applied to the crop foliage to prevent or minimise decreases in grain yields at the end of the growing season. Zn sulfate and Zn chelate are the most widely used compounds. This thesis reports the results of a field study to compare the effectiveness of the two compounds when the spray was applied at two growth stages of wheat (Gs14; seedling growth and Gs24; tillering). In addition, Zn applied with the seed while sowing the wheat crop was also included. Zinc applied to the soil while sowing was the most effective treatment. Zn chelate was more effective as a spray than Zn sulfate when applied at the earlier growth stage, but Zn sulfate was cheaper, and both sprays were equally effective when applied at the later growth stage. Recently in the region, durum wheat (T. durum L.), narrow-leafed lupin (Lupinus angustifolius L.), yellow lupin (L. luteus L.), white lupin (L. albus L.), canola (Brassica napus L.), chickpea (Cicer arietinum L.), faba bean (Vicia faba L.) and lentil (Lens culinaris Medik) were all increasingly grown in rotation with spring wheat. Consequently, the Zn requirement of the new crops was compared with the Zn requirements of spring wheat. Species requiring less Zn than spring wheat to produce the same relative yield were faba bean, chickpea, albus lupin and canola; species requiring more Zn were lentil and durum wheat. Spreadsheet models were developed to determine when re-application of fertiliser Zn was required for low and high production systems. Relative to freshly-applied Zn, the rate of decline in the RV of Zn applied in a previous year varied depending on the amount of Zn applied, time the Zn was in contact with soil since application, properties of the soil (soil pH, % clay, % organic carbon, % free calcium carbonate), plant species, and the amount of Zn removed in harvested grain or hay. The thesis has culminated in a better understanding of Zn in the agricultural production systems of WA. The distribution and correction of Zn deficiency is now predictable for the many soil types and cropping systems of WA. Accurate identification of Zn deficiency for a range of crop and pasture species by plant analyses, typically the youngest mature leaf, is now possible for local conditions. With the calibration of the DTPA Zn soil test for soils of WA, particularly for wheat the major crop species grown in WA, prognosis of potential Zn deficiency can now be predicted before the appearance of Zn deficiency or loss in plant production.

Wheat production is the largest enterprise within the Australian grain industry, with an annual gross value of production of approximately $4 billion. However high temperature stress (>35°C) and zinc (Zn) deficiency in soils are a frequent occurrence across the Australian wheat belt and represent two of the most important environmental limitations to wheat production and grain quality. The work presented here has shown for the first time that Zn nutrition can provide wheat plants with a level of tolerance to high temperature stress. Field trials, along with controlled environment studies, showed that supplementary Zn nutrition improved photosynthetic activity during a high temperature event, by stabilising chlorophyll initial fluorescence, Fo. Since increases in Fo under heat stress are associated with an increase in lipid fluidity of the thylakoid membranes at high temperature, the results suggested that adequate Zn fertilisation could preserve membrane integrity during heat stress. Electron microscopy confirmed this hypothesis, and showed that adequate Zn nutrition could maintain the integrity of a number of cellular membranes during high temperature, including the tonoplast, chloroplast envelope and the thylakoid membranes. Measurements of canopy temperature depression showed an improvement in the evaporative cooling of the canopy with supplementary Zn nutrition in the Zn inefficient varieties, suggesting better soil water extraction under warm conditions. Supplementary Zn nutrition also increased the kernel weight of plants grown under warm conditions in the field, however this was unrelated to the improvement in photosynthetic ctivity. Nevertheless, results from both controlled environment and field experiments demonstrated that the detrimental effects of low Zn availability and high temperature on the yield of Zn inefficient or thermosensitive wheat varieties will be most damaging when these stresses occur in combination. Analysis of protein composition showed that supplementary Zn fertilisation increased the glutenin:gliadin ratio in the grain. This suggests that Zn fertilisation may improve the bread-making quality of wheat under conditions of Zn deficiency. The results also showed a negative association between grain Zn concentration and the number of days over 35°C during grain filling, which suggests that the negative effects of high temperature stress on grain protein composition will be compounded when plants are grown on soils of low Zn availability. This thesis represents a valuable contribution to the understanding of the relationships between micronutrient supply and environmental stress. Further studies should be undertaken to establish whether the protective effect of Zn on the photosynthetic apparatus will be maintained under consecutive heat stress events, to determine the ways in which Zn ions stabilise and protect bio- membranes under heat stress and to confirm the positive effects of Zn on grain protein composition and baking quality. / Thesis (Ph.D.)--School of Agriculture and Wine, 2004.

Graduation date: 1969

Columbia River sediment was irradiated with ultraviolet light to determine if organic material could be removed without altering the sorptive properties of the hydrous oxides of iron and manganese. A laboratory preparation of Zn-65 spiked hydrous ferric oxide was subjected to ultraviolet irradiation in order to assess the photochemical effect upon Zn-65 release. The photochemically induced release of Mn-54 present on the Columbia River sediment was used to assess the effect on the hydrous oxides of manganese. The ultraviolet irradiation proved effective in removing up to 68% of the sedimentary organic material in 17 hours without causing release of Zn-65 or Sc-46. While the ultraviolet irradiation had no effect upon Zn-65 release from laboratory preparations of hydrous ferric oxides and Zn-65 spiked montmorillonite, a significant release of Mn-54 resulted from the photolysis treatment. The removal of Mn-54 was not accompanied by the release of sorbed Zn-65 or Sc-46 (nuclides expected to be sorbed by hydrous oxides), nor did there appear to be any permanent change in the nature of the Mn-54 on the sediment. Although it is possible that the hydrous oxides of manganese are affected by the ultraviolet treatment, it is likely that another species, such as the carbonate, is the species involved. Photo-oxidation appears to provide a method of obtaining sediments with substantially reduced organic content without affecting the sorptive properties of hydrous oxides or clay minerals. This result should allow the use of uptake studies to determine the importance of organic material in trace metal sorption by sediments. / Graduation date: 1972