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  • About
  • The Global ETD Search service is a free service for researchers to find electronic theses and dissertations. This service is provided by the Networked Digital Library of Theses and Dissertations.
    Our metadata is collected from universities around the world. If you manage a university/consortium/country archive and want to be added, details can be found on the NDLTD website.
31

Phase control in the synthesis of yttrium oxide nano and micro-particles by flame spray pyrolysis

Mukundan, Mallika 15 May 2009 (has links)
The project synthesizes phase pure Yttria particles using flame spray pyrolysis, and to experimentally determines the effect of various process parameters like residence time, adiabatic flame temperature and precursor droplet size on the phase of Yttria particles generated. Further, through experimentation and based on the understanding of the process, conditions that produce pure monoclinic Y2O3 particles were found. An ultrasonic atomization set-up was used to introduce precursor droplets (aqueous solution of yttrium nitrate hex hydrate) into the flame. A hydrogen-oxygen diffusion flame was used to realize the high temperature aerosol synthesis. The particles were collected on filters and analyzed using X-Ray Diffraction (XRD) and Transmission Electron Microscopy (TEM). Individual process parameters (flame temperature, residence time, precursor concentration, precursor droplet size) were varied in continuous trials, keeping the rest of the parameters constant. The effect of the varied parameter on the phase of the product Yttria particles was then analyzed. Pre-flame heating was undertaken using a nozzle heater at variable power. Precursor solution concentrations of 0.026 mol/L, 0.26 mol/L, and 0.65 mol/L were used. Residence time was varied by means of burner diameter (9.5 mm and 1.6 mm ID). Large precursor droplets were removed by means of an inertial impactor. The higher flame temperatures and precursor heating favor the formation of monoclinic yttrium oxide. The fraction of the cubic phase is closely related to the particle diameter. All particles larger than a critical size were of the cubic phase. Phase pure monoclinic yttrium oxide particles were successfully synthesized. The end conditions included a precursor concentration of 0.65 mol/L, a pure hydrogen-oxygen flame and a 1.6 mm burner. The precursor droplets entrained fuel gas was passed through a round jet impactor and preheated at full power (130 VA). The particles synthesized were in the size range of 0.350 to 1.7 µm.
32

Pyrolysis and ignition behavior of coal, cattle biomass, and coal/cattle biomass blends

Martin, Brandon Ray 15 May 2009 (has links)
Increases in demand, lower emission standards, and reduced fuel supplies have fueled the recent effort to find new and better fuels to power the necessary equipment for society’s needs. Often, the fuels chosen for research are renewable fuels derived from biomass. Current research at Texas A&M University is focused on the effectiveness of using cattle manure biomass as a fuel source in conjunction with coal burning utilities. The scope of this project includes fuel property analysis, pyrolysis and ignition behavior characteristics, combustion modeling, emissions modeling, small scale combustion experiments, pilot scale commercial combustion experiments, and cost analysis of the fuel usage for both feedlot biomass and dairy biomass. This paper focuses on fuel property analysis and pyrolysis and ignition characteristics of feedlot biomass. Deliverables include a proximate and ultimate analysis, pyrolysis kinetics values, and ignition temperatures of four types of feedlot biomass (low ash raw manure [LARM], low ash partially composted manure [LAPC], high ash raw manure [HARM], and high ash partially composted manure [HAPC]) as well as blends of each biomass with Texas lignite coal (TXL). Activation energy results for pure samples of each fuel using the single reaction model rigorous solution were as follows: 45 kJ/mol (LARM), 43 kJ/mol (LAPC), 38 kJ/mol (HARM), 36 kJ/mol (HAPC), and 22 kJ/mol (TXL). Using the distributed activation energy model the activation energies were 169 kJ/mol (LARM), 175 kJ/mol (LAPC), 172 kJ/mol (HARM), 173 kJ/mol (HAPC), and 225 kJ/mol (TXL). Ignition temperature results for pure samples of each of the fuels were as follows: 734 K (LARM), 745 K (LAPC), 727 (HARM), 744 K (HAPC), and 592 K (TXL). There was little difference observed between the ignition temperatures of the 50% blends of coal with biomass and the pure samples of coal as observed by the following results: 606 K (LARM), 571 K (LAPC), 595 K (HARM), and 582 K (HAPC).
33

Phase control in the synthesis of yttrium oxide nano and micro-particles by flame spray pyrolysis

Mukundan, Mallika 15 May 2009 (has links)
The project synthesizes phase pure Yttria particles using flame spray pyrolysis, and to experimentally determines the effect of various process parameters like residence time, adiabatic flame temperature and precursor droplet size on the phase of Yttria particles generated. Further, through experimentation and based on the understanding of the process, conditions that produce pure monoclinic Y2O3 particles were found. An ultrasonic atomization set-up was used to introduce precursor droplets (aqueous solution of yttrium nitrate hex hydrate) into the flame. A hydrogen-oxygen diffusion flame was used to realize the high temperature aerosol synthesis. The particles were collected on filters and analyzed using X-Ray Diffraction (XRD) and Transmission Electron Microscopy (TEM). Individual process parameters (flame temperature, residence time, precursor concentration, precursor droplet size) were varied in continuous trials, keeping the rest of the parameters constant. The effect of the varied parameter on the phase of the product Yttria particles was then analyzed. Pre-flame heating was undertaken using a nozzle heater at variable power. Precursor solution concentrations of 0.026 mol/L, 0.26 mol/L, and 0.65 mol/L were used. Residence time was varied by means of burner diameter (9.5 mm and 1.6 mm ID). Large precursor droplets were removed by means of an inertial impactor. The higher flame temperatures and precursor heating favor the formation of monoclinic yttrium oxide. The fraction of the cubic phase is closely related to the particle diameter. All particles larger than a critical size were of the cubic phase. Phase pure monoclinic yttrium oxide particles were successfully synthesized. The end conditions included a precursor concentration of 0.65 mol/L, a pure hydrogen-oxygen flame and a 1.6 mm burner. The precursor droplets entrained fuel gas was passed through a round jet impactor and preheated at full power (130 VA). The particles synthesized were in the size range of 0.350 to 1.7 µm.
34

Pyrolytic study of 2-(2-Azidoethyl)-1H-indole and 2-Azido-1-(1H-indol-2-yl)ethanone

Chou, Wei-zhen 05 August 2004 (has links)
Flash vacuum pyrolysis (FVP) of 2-(2-azidoethyl)-1H-indole, via a nitrene intermediate, gave two products, 2-methyl-1H-indole and quinoline. However, under the same route, FVP of 2-azido-1-(1H-indol-2-yl)ethanone produced indole, 1-(1H-indol-2-yl)ethanone, (1H-indol-2-yl)-[4-(1H-indol-2-yl)-1H-imidazol-2-yl]ethanone and it¡¦s isomer.
35

Pyrolytic Study of 6-Phenylfulvene and Its Derivatives

Lin, Fang-Ying 11 July 2005 (has links)
Flash vacuum pyrolysis (FVP) of cyclopenta-2,4-dienylidenemethylbenzene gave acenaphthylene¡Bacenaphthene and dimer¡G5a,5b,11b,11c-tetrahydrocyclobuta[1",2":3,4;4",3":3',4']dicyclopenta[1,2-a:1',2'-a']diindene¡CPyrolysis of 1-bromo-4-cyclopenta-2,4-dienylidenemethylbenzene gave acenaphthene¡Bdimer¡B5-bromoacenaphthylene and 5-bromoacenaphthene¡CPyrolysis of 2-cyclopenta-2,4-dienylidenemethyl-3-methylthiophene gave 5H-1-thia-s-indacene and 7H-1-thia-s-indacene¡Aand naphthalene¡CPyrolysis of 2-inden-1-ylidene-methyl-3-methylthiophene gave 5H-1-thiacyclopenta[b]fluorene and unidentified products¡C
36

Pyrolytic study of 6-benzylfulvene and its benzofuran analogues

Wang, Yuan-Heng 05 July 2006 (has links)
Flash vacuum pyrolysis (FVP) of 1-(2-(cyclopenta-2,4-dienylidene)ethyl)benzene gave 1H-benzo[e]indene, 3H-benzo[e]indene, and fluorene. Pyrolysis of 2-cyclopentadienylidenemethyl-3-methylbenzofuran gave 1H-benzofurano[2,3-d]indene and 3H-benzofurano[2,3-d]indene. Pyrolysis of 2-cyclopentadienylidenemethylbenzofuran gave 1H-benzo[e]indene, 3H-benzo[e]indene, fluorene, 2-phenylbenzofuran, and unidentified products
37

Study of the Chemistry of 5-Thiapyrido[b]cyclobuten-6-one,6-Oxapyrido[b]cyclobuten-5-one and 5-Oxapyrido[b]cyclobuten-6-one

Liu, Wei-Min 27 June 2000 (has links)
Flash vacuum pyrolysis of 3-mercaptopyridine-2-carboxylic acid(74), gave 3-mercaptopyridine(83) and di-(3-pyridyl)disulfide(84). FVP of 3-hydroxy-pyridine-2-carboxylic acid(75), gave dipyrrolo[1,2-a;1',2'-d]pyrazine-5,10-dione(91). FVP of 2-hydroxypyridine-3-carboxylic acid(76), gave di-[2]-pyridylether(101) and trimer(102).
38

Synthesis and Study of the Hetero-analogues of Benzocyclobutenoe

Chiu, Shao-Jung 06 July 2000 (has links)
Flash Vacuum Pyrolysis of each proper precussors gave highly reactive intermediates : heteroanalogues of Benzocyclobutenoe, imino-compounds, and ketene compounds. The reactive intermediates could be used in many organic synthesis.
39

Synthesis and Pyrolysis of Benzoic3,5- Dimethyl-2-furoic Anhydride and 4-Quinolylmethyl Benzoate

LIN, CHI-CHENG 13 July 2000 (has links)
Synthesis and Pyrolysis of Benzoic3,5- Dimethyl-2-furoic Anhydride and 4-
40

Ptrolytic Study of 2-(azidoethyl)pyridine and 1-methyl-2- (2-azidoethyl) pyrrole

Chen, Li-Hui 04 July 2002 (has links)
Flash vacuum pyrolysis(FVP) of 2-(azidoethyl)pyridine, via a nitrene intermediate, gave two products, a dimer (1,2-di(2-pyridinyl)-ethane) and a trimer (3,5-di(2-pyridyl)-pyridine). However by the same route, FVP of 1-methyl-2- (2-azidoethyl) pyrrole produced only a dimer (1,2-di(1-methylpyrrol-2-yl)ethane).

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