A dissertation submitted to the Faculty of Science, University of the Witwatersrand, Johannesburg, in fulfilment of requirements for the degree of Master of Science. Johannesburg, 2016. / This study has explored the CVD synthesis of carbon nanofibres (CNFs) using Eskom’s waste coal fly ash as a catalyst with acetylene and hydrogen as the carbon source and carrier gas, respectively. In the process, a possible growth mechanism for these carbon nanofibres was sought. CNFs were successfully synthesised from fly ash and were found to have an average diameter of 22±7 nm. The growth mechanism of these CNFs was studied using EDS, TEM and laser Raman spectroscopy. It was observed that CNFs grew via root growth on spherical particles of fly ash and by tip growth on irregular-shaped metal oxide agglomerates. Both of these were found, through EDS analysis, to be Fe-rich. CNFs were functionalised between 2-12 h under reflux at 110 °C using a 3:1 (v/v) combination of HNO3 and H2SO4 in order to introduce functional groups onto their surfaces to act as anchors for hydrophilic reactants. The functionalisation of these CNFs was studied using TEM, laser Raman spectroscopy, ATR-FTIR spectroscopy, PXRD, BET, XRF and TGA. ATR-FTIR spectroscopy showed that some carbonyl functional groups were present on the surfaces of these CNFs after functionalisation. The functionalised CNFs (fCNFs) were then treated using a simple hydrothermal method to deposit 10% (m/m) of TiO2 nanoparticles onto their surface. This hydrothermal method employed the drop-wise addition of TiCl4 to a cold water-fCNFs mixture, which was then refluxed at 115 °C for 2-12 h. Laser Raman spectroscopy confirmed the presence of both TiO2 (phase pure anatase) and CNFs. ATR-FTIR spectroscopy provisionally revealed the presence of covalent Ti-O-C bonds. Studies where the duration of exposure to TiCl4 and the functionalisation time of CNFs were examined showed that the particle size and agglomeration of the TiO2 nanoparticles did not affect the surface area of the CNF-TiO2 hybrids significantly. However, CNF-TiO2 hybrids which were shown by TGA to have high fly ash content were observed to have low surface areas. fCNFs functionalised at 2 h had the highest surface area, at all fixed durations of exposure to TiCl4 by comparison with fCNFs which had been functionalised for longer periods. / GR2016

A dissertation submitted to the Faculty of Science, University of the Witwatersrand, Johannesburg, in fulfilment of the requirements for the Degree of Master of Science. Johannesburg, 2015. / Fly ash is a by-product generated during the combustion of coal for electricity gen- eration. Previous studies have shown that various waste fly-ashes (Japanese, Saudi Arabian, and Australian) contain trace quantities of transition metal elements which can be used in the synthesis of shaped carbon nanomaterials. A survey of the litera- ture has shown that no attempts to correlate the composition of a particular coal fly ash and the type or quantity of carbon nanomaterials (CNMs) that can be synthesized has been made. Neither has the effect of leached fly ash been tested for the synthesis of CNMs. Hence a study on the effect of the chemical composition of South African fly ash (collected from ESKOM’s Duvha power station in Mpumalanga) upon the chemical vapour deposition (CVD) synthesis of carbon nanostructures is justified. Untreated and chemically treated fly ash samples were used as catalysts in the CVD method to synthesize CNMs. In the latter case selective leaching experiments were conducted on the fly ash samples under acidic, basic and neutral conditions. Op- timal CNM synthetic conditions were achieved by initially flowing H2 gas to re- duce the metal oxides within the fly ash catalyst followed by the introduction of the carbon source (C2H2) at a temperature range of 600 - 800 ◦C. All samples were quantitatively and/or qualitatively characterized. Inductively coupled plasma optical emission spectrometry (ICP-OES) and X-ray fluorescence (XRF) techniques were used to quantify the metal ions which were removed from the fly ash samples. Fur- thermore, qualitative studies were conducted with (PXRD, and laser Raman spec- troscopy), morphological and surface area characterization techniques (SEM, TEM and BET) were used to investigate the synthesis of CNMs from the untreated and chemically treated fly ash samples. Results have shown that carbon nanofibers (CNFs) of different geometric morpholo- gies were synthesized at an optimal yield temperature of 700◦C. A combination of smooth, thin, wide, spiral platelet-like, stacked cup, and fishbone morphologies were reported when the untreated fly ash catalyst was used. Fly ash catalysts under acidic, basic and neutral treatments showed CNFs of varying sizes and specific morpholo- gies. Smooth graphitic platelet-like, stacked cup and platelet-like CNFs were re- ported when the fly ash catalyst was leached with neutral, basic and acidic solutions. Carbon nanofibre sizes with the IG ID ratios were reported as follows 115 nm (1.092), 52 nm (0.799), and 200 nm (0.960) under neutral, basic and acidic mediums respec- tively. Surface areas (41, 14 and 7) m2/g for the CNFs that were synthesised from the neutral, basic and acidic treated fly ash catalysts were related to the selective leaching of metals. The quality and quantity of CNFs obtained under acidic medium were associated with the leaching of iron (5.6%), cobalt (1.7%), calcium (20.4%), copper (12.5%), chromium (4.6%), magnesium (23.3%), manganese (15.2%) and nickel (2%) from the fly ash catalyst. Under a basic medium only chromium (0.2%), calcium (0.3%) and copper (7.4%) were removed. Significantly the best quality of CNFs was ob- tained when fly ash was treated under neutral conditions. Metal ions such as: cal- cium (3.7%), copper (3.8%), chromium (0.1%), and magnesium (1.3%) were mod- erately removed from the ash matrix. Therefore, composition and quantity of the fly ash catalyst had an effect on the synthesis of CNFs.

Thesis. 1976. Sc.D.--Massachusetts Institute of Technology. Dept. of Chemical Engineering. / Microfiche copy available in Archives and Science. / Vita. / Bibliography: leaves 321-328. / by Ashok S. Padia. / Sc.D.

Os lodos provenientes de estação de tratamento de água brasileira são, frequentemente, dispostos e lançados diretamente nos corpos d\'água, causando um impacto negativo no meio ambiente. Também, cinzas de carvão são produzidas pela queima de carvão em usinas termelétricas e é o resíduo sólido industrial mais gerado no sul do Brasil: cerca de 4 milhões ton/ano. A disposição eficiente das cinzas de carvão é um problema devido ao seu volume maciço e aos riscos nocivos para o ambiente. O objetivo deste trabalho foi estudar a viabilidade da incorporação desses dois resíduos industriais em uma massa utilizada na fabricação de tijolos ecológicos. As amostras de cinzas leve do filtro ciclone da usina termelétrica localizada no Município de Figueira, Estado do Paraná, Brasil e o lodo de estação de tratamento de água localizada no município de Terra Preta, Estado de São Paulo, Brasil, foram utilizados no estudo. Tijolos de cinzas leve-lodo e cinzas leve-lodo-solo-cimento foram moldados e testados de acordo com padrões brasileiros. Os materiais foram caracterizados por análises físico-químicas, difração de raios X, análise térmica, análise morfológica, espectroscopia no infravermelho com transformada de Fourier e análise granulométrica. Os resultados indicaram que o lodo de estação de tratamento de água e as cinzas de carvão podem ser usados na manufatura de tijolos prensados solo-cimento de acordo com a Norma Brasileira NBR 10836/94. / Sludge from treatment water Brazilian plant station are, frequently, disposed and launched directly in the water bodies, causing a negative impact in the environment. Also, coal ashes is produced by burning of coal in coal-fired power stations and is the industrial solid waste most generated in southern Brazil: approximately 4 million tons/y. The efficient disposal of coal ashes is an issue due to its massive volume and harmful risks to the environment. The aim of this work was study the feasibility of incorporating these two industrial wastes in a mass used in the manufacture of ecological bricks. Samples of fly ashes from a cyclone filter from a coal-fired power plant located at Figueira County in Paraná State, Brazil and waterworks sludge of Terra Preta County in São Paulo State, Brazil, were used in the study. Fly ash-sludge and fly ash-sludge-soil-cement bricks were molded and tested, according to the Brazilians Standards. The materials were characterized by physical-chemical analysis, X-ray diffraction, thermal analysis, morphological analysis, Fourier transform infrared spectroscopy and granulometric analysis. The results indicate that the waterworks sludge and coal ashes have potential to be used on manufacturing soil-cement pressed bricks according to the of Brazilians Standards NBR 10836/94.

Thesis (M.S.)--Oregon State University, 1983. / Typescript (photocopy). One map folded in pocket. Includes bibliographical references (leaves 107-110). Also available online.

On-going research at Texas A&M University indicated that soil stabilization using calcium chloride filter cake along with Class F fly ash generates high strength. Previous studies were conducted with samples containing calcium chloride filter cake and both Class C fly ash and Class F fly ash. Mix design was fixed at 1.3% and 1.7% calcium chloride and 5% and 10% fly ash with crushed limestone base material. Throughout previous studies, recommended mix design was 1.7% calcium chloride filter cake with 10% Class F fly ash in crushed limestone base because Class F fly ash generates early high and durable strength. This research paper focused on the strength increase initiated by greater than 1.7% pure calcium chloride used with Class F fly ash in soil to verify the effectiveness and optimum ratio of calcium chloride and Class F fly ash in soil stabilization. Mix design was programmed at pure calcium chloride concentrations at 0% to 6% and Class F fly ash at 10 to 15%. Laboratory tests showed samples containing any calcium chloride concentration from 2% to 6% and Class F fly ash content from 10% to 15% obtained high early strength however, optimum moisture content, different mix design, and mineralogy deposit analysis are recommended to evaluate the role and the effectiveness of calcium chloride in soil stabilization because of the strength decreasing tendency of the samples containing calcium chloride after 56 days.

Thesis (doctoral)--Helsinki University of Technology, 2000. / Includes bibliographical references. Also available on the World Wide Web.

Thesis (M.S.)--West Virginia University, 2001. / Title from document title page. Document formatted into pages; contains vii, 53 p. : ill. (some col.). Includes abstract. Includes bibliographical references (p. 48-53).

Thesis (M.S.)--West Virginia University, 2002. / Title from document title page. Document formatted into pages; contains viii, 152 p. : ill. (some col.). Vita. Includes abstract. Includes bibliographical references (p. 87-91).

Thesis (Ph. D.)--Washington State University, December 2009. / Title from PDF title page (viewed on Dec. 15, 2009). "School of Earth and Environmental Sciences." Includes bibliographical references (p. 232-247).