The use of magnesium hydroxide (Mg(OH)2) as a flame retardant and smoke-suppressor in polymeric materials has been of great interest recently. Because it contains no halogens or heavy metals, it is more environmentally friendly than the flame retardants based on antimony metals or halogenated compounds. Mg(OH)2 can be produced by the hydration of magnesium oxide (MgO), which is usually produced industrially from the calcination of the mineral magnesite (MgCO3). The thermal treatment of the calcination process dramatically affects the reactivity of the MgO formed. Reactivity of MgO refers to the extent and the rate of hydration thereof to Mg(OH)2. The aim of this study was to investigate the effect of calcination time and temperature on the reactivity of MgO, by studying the extent of its hydration to Mg(OH)2, using water and magnesium acetate as hydrating agents. A thermogravimetric analysis (TGA) method was used to determine the degree of hydration of MgO to Mg(OH)2. The reactivity of MgO was determined by BET (Brunauer, Emmett and Teller) surface area analysis and a citric acid reactivity method. Other techniques used included XRD, XRF and particle size analysis by milling and sieving. The product obtained from the hydration of MgO in magnesium acetate solutions contains mainly Mg(OH)2, but also some unreacted magnesium acetate. Magnesium acetate decomposition reaction takes place in the same temperature range as magnesium hydroxide, which complicates the quantitative TG analysis of the hydrated samples. As a result, a thermogravimetric method was developed to quantitatively determine the amounts of Mg(OH)2 and Mg(CH3COO)2 in a mixture thereof. The extent to which different experimental parameters (concentration of magnesium acetate, solid to liquid ratio and hydration time) influence the degree of hydration of MgO were evaluated using magnesium acetate as a hydrating agent. Magnesium acetate was found to enhance the degree of MgO hydration when compared to water. By increasing the hydration time, an increase in the percentage of Mg(OH)2 formed was observed. In order to study the effect of calcining time and temperature on the hydration of the MgO, the MgO samples were then calcined at different time periods and at different temperatures. The results have shown that the calcination temperature is the main variable affecting the surface area and reactivity of MgO. Lastly, an attempt was made to investigate the time for maximum hydration of MgO calcined at 650, 1000 and 1200oC. From the amounts of Mg(OH)2 obtained in magnesium acetate, it seems that the same maximum degree of hydration is obtained after different hydration times. A levelling effect that was independent of the calcination temperature of MgO was obtained for the hydrations performed in magnesium acetate. Although there was an increase in the percentage of Mg(OH)2 obtained from hydration of MgO in water, the levelling effect observed in magnesium acetate was not observed in water as a hydrating agent, and it seemed that the extent of MgO hydration in water was still increasing. The results obtained in this study demonstrate that the calcination temperature can affect the reactivity of MgO considerably, and that by increasing the hydration time, the degree of hydration of MgO to Mg(OH)2 is enhanced dramatically. / Chemistry / M. Sc. (Chemistry)

Yau Man Yan Eric = 鎂和氧化鋅反應製備氧化鎂納米棒 / 游文仁. / Thesis (M.Phil.)--Chinese University of Hong Kong, 2004. / Includes bibliographical references. / Text in English; abstracts in English and Chinese. / Yau Man Yan Eric = Mei he yang hua xin fan ying zhi bei yang hua mei na mi bang / You Wenren. / Acknowledgement --- p.i / Abstract --- p.ii / 摘要 --- p.iii / Table of contents --- p.iv / List of tables --- p.viii / List of figures --- p.ix / Chapter Chapter 1 --- Introduction / Chapter 1.1 --- Nanostructured materials --- p.1-1 / Chapter 1.2 --- Application of nano-materials --- p.1-1 / Chapter 1.3 --- Current development of nano-materials --- p.1-2 / Chapter 1.4 --- Synthesis of nano-materials --- p.1-2 / Chapter 1.4.1 --- Physical methods --- p.1-3 / Chapter 1.4.1.1 --- Physical vapor deposition --- p.1-3 / Chapter 1.4.1.2 --- Arc-discharge process --- p.1-3 / Chapter 1.4.1.3 --- Laser ablation --- p.1-4 / Chapter 1.4.2 --- Chemical methods --- p.1-4 / Chapter 1.4.2.1 --- Chemical vapor deposition --- p.1-4 / Chapter 1.4.2.2 --- Metal-organic chemical vapor deposition (MOCVD) --- p.1-4 / Chapter 1.4.2.3 --- Solgel method --- p.1-5 / Chapter 1.5 --- Study on growth mechanism of nano-materials --- p.1-5 / Chapter 1.5.1 --- Vapor-liquid-solid (VLS) mechanism --- p.1-5 / Chapter 1.5.2 --- Vapor-solid (VS) mechanism --- p.1-6 / Chapter 1.6 --- Applications of Magnesium Oxide (MgO) materials --- p.1-7 / Chapter 1.7 --- Previous works on MgO nanostructures --- p.1-8 / Chapter 1.7.1 --- Network like MgO nanobelts --- p.1-8 / Chapter 1.7.2 --- Decorated MgO crystalline fibers --- p.1-9 / Chapter 1.7.3 --- Mg2Zn11 - MgO belt-like nanocables --- p.1-9 / Chapter 1.7.4 --- MgO nanowires with uniform diameter distribution --- p.1-10 / Chapter 1.7.5 --- Aligned MgO nanorods on MgO (100) substrates --- p.1-11 / Chapter 1.8 --- Objectives and approaches of this project --- p.1-12 / Chapter 1.8.1 --- Addition of sodium chloride (NaCl) --- p.1-13 / Chapter 1.9 --- Thesis Layout --- p.1-13 / Chapter 1.10 --- References --- p.1-15 / Chapter Chapter 2 --- Methodology and Instrumentation / Chapter 2.1 --- Introduction --- p.2-1 / Chapter 2.2 --- Powder Metallurgy --- p.2-1 / Chapter 2.3 --- Sample fabrication --- p.2-1 / Chapter 2.3.1 --- Starting materials --- p.2-1 / Chapter 2.3.2 --- Cold pressing --- p.2-2 / Chapter 2.3.2.1 --- Single pellet method --- p.2-2 / Chapter 2.3.2.2 --- Double pellet method --- p.2-3 / Chapter 2.3.3 --- Argon tube furnace sintering --- p.2-3 / Chapter 2.4 --- Study of fabrication parameters --- p.2-4 / Chapter 2.4.1 --- Heat treatment temperature --- p.2-4 / Chapter 2.4.2 --- NaCl content in sample --- p.2-4 / Chapter 2.4.3 --- Duration of heat treatment --- p.2-5 / Chapter 2.5 --- Control Experiments --- p.2-5 / Chapter 2.5.1 --- Effect of addition of NaCl --- p.2-5 / Chapter 2.5.2 --- Effect of residual oxygen --- p.2-5 / Chapter 2.5.3 --- Geometrical effect of experimental setup --- p.2-6 / Chapter 2.5.3.1 --- Compressed double pellet method --- p.2-6 / Chapter 2.5.3.2 --- Powder on Magnesium pellet method --- p.2-6 / Chapter 2.5.3.3 --- Single pellet method --- p.2-7 / Chapter 2.6 --- Characterization Methods --- p.2-7 / Chapter 2.6.1 --- Thermal analysis - Differential thermal analyzer (DTA) --- p.2-7 / Chapter 2.6.2 --- Structural analysis --- p.2-7 / Chapter 2.6.2.1 --- Scanning electron microscopy (SEM) --- p.2-7 / Chapter 2.6.2.2 --- Transmission electron microscopy (TEM) --- p.2-8 / Chapter 2.6.3 --- Phases determination - X-ray powder diffractometry (XRD) --- p.2-8 / Chapter 2.7 --- References --- p.2-9 / Chapter Chapter 3 --- Results of Mg-ZnO-NaCl System / Chapter 3.1 --- Introduction --- p.3-1 / Chapter 3.2 --- Results of thermal analysis --- p.3-1 / Chapter 3.2.1 --- Chemical reactions --- p.3-1 / Chapter 3.2.2 --- DTA results --- p.3-2 / Chapter 3.3 --- Variation of heat treatment temperature --- p.3-3 / Chapter 3.3.1 --- XRD pattern --- p.3-3 / Chapter 3.3.2 --- SEM images --- p.3-4 / Chapter 3.4 --- Variation of NaCl content --- p.3-5 / Chapter 3.4.1 --- TEM analysis --- p.3-5 / Chapter 3.5 --- Variation of duration of heat treatment --- p.3-6 / Chapter 3.6 --- Additional findings --- p.3-7 / Chapter 3.7 --- Discussions --- p.3-7 / Chapter 3.8 --- References --- p.3-10 / Chapter Chapter 4 --- Results of Control Experiments / Chapter 4.1 --- Introduction --- p.4-1 / Chapter 4.2 --- The study of Mg-ZnO system --- p.4-1 / Chapter 4.3 --- The study of residual oxygen effect --- p.4-2 / Chapter 4.4 --- The study of geometrical effect of experiment setup --- p.4-2 / Chapter 4.5 --- Discussions --- p.4-3 / Chapter 4.5.1 --- Effect of addition of NaCl --- p.4-3 / Chapter 4.5.2 --- Effect of residual oxygen --- p.4-3 / Chapter 4.5.3 --- Role of ZnO --- p.4-4 / Chapter 4.5.4 --- Growth model --- p.4-4 / Chapter 4.6 --- References --- p.4-7 / Chapter Chapter 5 --- Conclusions and Further Studies / Chapter 5.1 --- Conclusion --- p.5-1 / Chapter 5.2 --- Further studies --- p.5-2 / Chapter 5.3 --- References --- p.5-3

No description available.

Measurements have been made of the X-ray scatter from an MgO single crystal at low temperatures irradiated by an infra-red laser beam of wavelength 10.6μm. The purpose of these measurements was to obtain information about the anharmonic coupling between the lattice vibrations. The modes investigated were the transverse acoustic phonons in the [100] direction, which it has been suggested have anomalously long lifetimes at very low temperatures. The above method was chosen after considering a variety of possible excitation methods including electron-phonon interactions via the piezoelectric effect and the deformation potential. These other processes had to be rejected because they either excited phonons which were unsuitable for X-ray measurement or required pulsed experiments. The dispersion curves for MgO, obtained from a deformable shell model for the lattice were analysed to provide information as to the most likely positions in reciprocal space for phonon population enhancement to occur. The decay routes for the primary phonons excited directly by the infra-red radiation were predicted from the dispersion curves. A major part of the work involved the design and construction of the helium cryostat on which the sample crystal was mounted and kept at as low a temperature as possible. The standard X-ray detection technique of a scintillating crystal-photomultiplier combination was employed and the infra-red beam was produced by a CO2 gas laser with an output power of up to lOW. Because of the nature of the measurements, the results obtained for the change in X-ray scatter by the MgO crystal when the infra-red beam was shone on the crystal required analysis by statistical methods in order to provide the maximum information. It was possible to set an upper limit to the effects found of a few percent, and to compare the orders of magnitude of the coupling for two different processes.

Thesis (Ph. D.)--Auburn University, 2008. / Abstract. Vita. Includes bibliographical references (p. 140-142).

Thesis (M.S.)--University of California, Berkeley, 1962. / "UC-34 Physics" -t.p. "TID-4500 (17th Ed.)" -t.p. Includes bibliographical references (p. 15).

Thesis (Ph.D.)--University of California, Berkeley, 1962. / "UC-4 Chemistry" -t.p. "TID-4500 (16th Ed.)" -t.p. Includes bibliographical references (p. 70-72).

No description available.

No description available.

Magnesium oxide (MgO) is a cost-effective and environmentally sustainable alternative to magnesium chloride (MgCl2) and sodium hydroxide (NaOH) used for sidestream struvite recovery from anaerobically digested supernatant (centrate) through the Pearl® process. MgO is produced from magnesite (MgCO3) calcination, and different calcination conditions can alter the quality and characteristics of the MgO product. It was hypothesized that the insolubility of MgO could provide a "slowly available" form of Mg2+ in the reactor and consequently allow the reactor to be operated beyond design phosphorus (P) reactor loading. MgO has been utilized in other P recovery technologies, e.g. the Phospaq™ Process, but operation and performance of MgO using a full-scale Pearl® 500 fluidized bed reactor was investigated. Performance at rated reactor loading utilizing MgO was initially comparable to baseline conventional MgCl2 reactor operation, ≥50% struvite yield (P recovered/theoretical P recovery) and ≥70% total phosphorus (TP) removal. However, the pilot reactor operated at 2X reactor loading showed comparable results to baseline performance at 1.5X reactor loading. During the full-scale pilot, optimization of the reactor utilizing MgO was limited by the struvite product size that the struvite post-processing equipment could effectively harvest. Additionally, the MgO characteristics due to calcination conditions were hypothesized to affect struvite precipitation kinetics. In struvite precipitation jar testing, MgO products were used to analyze the saturation index, measure precipitation kinetics, and understand the effect that MgO hydration and reactivity had on struvite precipitation. Jar testing showed that initial P removal increased with increasing MgO product reactivity. The most reactive MgO used, Timab AK98, showed 1-40% P removal and substantial decrease in solution saturation index immediately after dosing MgO to centrate. The slower P removal and decrease in saturation index observed with the less reactive material suggests that MgO can provide a "slowly available" Mg2+ reserve throughout the struvite precipitation reaction. / Master of Science / Phosphorus is an essential element for human, plant and animal health. Necessary bodily functions cannot be performed without inputting phosphorus to cell metabolic pathways, such as cell repair and formation of nucleic acids, bone mineral and stored energy. Phosphates are the most common form of phosphorus found in the environment and are a component of many common substances, such as detergents, fertilizers, food and urine. Due to the increasing population and food demand the need for phosphorus-based fertilizers has soared since the 1940s. In 2018, 240 megatons of phosphate rock were mined, and 17 megatons of phosphorus were extracted from mined ore. 15 megatons of the extracted phosphorus were used in fertilizer production. Because of phosphorus loss from the soil and inefficient agro-practices, only 20% of the extracted phosphorus is consumed by humans and animals from food and little is then recycled from our waste systems. There is a major gap in the agricultural phosphorus cycle that is necessary to address with sustainable practices (Oster, M. et al. 2018). Phosphorus can be recovered from wastewater in the form of struvite, which is a mineral that can be utilized a slow-release fertilizer. Conventional methods of phosphorus recovery from wastewater have the potential to be costly. By utilizing an alternative chemical, struvite recovery can be more cost-effective and environmentally sustainable.