Thesis (M.S.)--West Virginia University, 2008. / Title from document title page. Document formatted into pages; contains vi, 78 p. : ill. (some col.). Includes abstract. Includes bibliographical references (p. 42-44).

Thesis (M.S.)--Oregon State University, 2008. / Printout. Includes bibliographical references (leaves 50-62). Also available on the World Wide Web.

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The reaction kinetics of Iroko and Mahogany were studied using TGA. The pyrolysis process was achieved using six different heating rates of 2,5,8,12,15 and 20˚C. A 15˚C/min heating rate was used for gasification in steam at different temperatures while varying the concentrations of nitrogen and steam in the process. The kinetic parameters, activation energy and pre exponential factor, were obtained by implementing two chosen kinetic models. These models are: Friedman’s Iso-conversional Method, Flynn-Wall-Ozawa Method (FWO). There were substantial differences in the values of the kinetic triplets found from the experiments. Due to the substantial differences in the values, it was not the best way to perform this kind of analysis (which is the traditional way) but instead to use pure regression analysis; but using it for the whole data set (that means for all heating rates) and minimize the difference with experimental data.

A microelectromechanical systems (MEMS)-based environmental monitoring platform was presented in this dissertation. All devices were realized using thin-film piezoelectric-on-substrate (TPoS) technology, which provides a path to integrate various functionalities on a single substrate with MEMS components. TPoS resonators exhibit high quality factors (Qs) in air and are capable of low-power oscillator implementation, which further qualifies such a platform for mobile and portable systems. To validate the TPoS platform, gravimetric humidity sensing was demonstrated with thermally-corrected output by an uncoated "reference" temperature sensor. Also presented were TPoS sensors for toluene and xylene, which are pollutants of great importance for indoor and outdoor air quality as well as health screenings. Silicon dual-mode resonators and oscillators for self-temperature sensing were also explored. Dual-mode thermometry exploits the inherent frequency-temperature dependence of silicon to accurately and locally measure device temperature, forming an essential building block of highly stable oscillators and sensors. Multi-axis piezo-on-Si kinetic energy harvesting (KEH) devices with integrated frequency-upconverting transducers were also introduced. Devices were micromachined on the same substrate as TPoS resonant sensors and have an individual volume in mm3, enabling applications in wireless autonomous sensor nodes. In remote locations where continuous operation may be required, TPoS energy harvesters can provide battery replacement or recharging alternatives that do not increase overall system size.

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Les particules fines ont un impact réel sur la qualité de vie et la santé de millions de personnes dans les grandes zones urbaines, notamment en Asie. Pour les détecter et quantifier leur concentration, les capteurs de particules optiques sont les plus couramment étudiés, mais restent relativement chers et volumineux. Les transducteurs MEMS micropoutres sont largement utilisés pour des applications gravimétriques, pour la détection de particules ou de gaz, ce qui requiert des sensibilités massiques (Sm) élevées et des limites de détection (LOD) basses. Pour cela les micropoutres les plus adaptées sont celles ayant des fréquences de résonance (f0) et facteurs de qualité (Q) élevés, avec de faibles bruits de mesure et des masses faibles. Les micropoutres silicium sont couramment utilisées en tant que capteurs gravimétriques et sont de sérieux candidats pour répondre aux caractéristiques souhaitées. Cependant, la sérigraphie a le potentiel pour une fabrication moins chère, plus rapide et aussi à grande échelle. Pour ces micropoutres, l'actionnement et la lecture de f0 sont possibles par effet piézoélectrique. Bien qu'il existe des solutions inorganiques prometteuses sans plomb, les céramiques de titano-zirconate de plomb (PZT) possèdent encore les meilleures propriétés parmi les matériaux piézoélectriques. Des micropoutres fabriquées en technologie hybride couches épaisses sérigraphiées, à actionnement et lecture piézoélectriques intégrés, libérées à l'aide d'une couche sacrificielle polyester et avec co-cuisson de toutes les couches pour leurs libérations sont présentées ici. Différentes géométries ont été testées de 1 mm à 2 mm de large et de 1 mm à 8 mm de long, pour une épaisseur d'environ 100 μm. Une masse volumique ρ PZT = 7200 kg/m³ a été obtenue (≈ 93%ρ PZT massif). Enfin, avec une micropoutre 1×2×0,1 mm³, une sensibilité Sm ≈ 85 Hz/μm et une LOD de 70 ng ont été trouvées, permettant des applications en détection de particules. / Fine particulate matters (PM) have a real impact on the quality of life and health of millions of people in large urban areas, especially in Asia. In order to detect them and quantify their concentration, optical PM sensors are the most widely studied, but remain relatively expensive and bulky. MEMS microcantilever transducers are widely used for gravimetric applications, for PM or gas detection, which requires high mass sensitivities (Sm) and low limits of detection (LOD). A solution is to focus on microcantilevers with high resonance frequencies (f0) and quality factors (Q), low measurement noise and low masses. Silicon microcantilevers are commonly used as gravimetric sensors and are serious candidates to meet the desired characteristics. However, screen printing has the potential for cheaper, faster and large scale manufacturing. Such microcantilevers can be actuated and f0 read-out using the piezoelectric effect. Although promising lead-free inorganic solutions exist, titanium lead zirconate (PZT) ceramics still have the best properties among piezoelectric materials. Screen-printed microcantilevers manufactured in hybrid thick-film technology, with integrated piezoelectric actuation and read-out, released using a polyester sacrificial layer and with co-firing of all the layers are presented here. Different geometries were tested from 1 mm to 2 mm wide and from 1 mm to 8 mm long, for a thickness of about 100 μm. A density ρ PZT = 7200 kg/m³ (≈ 93%ρ PZT bulk) was obtained. With a 1×2×0.1 mm³ microcantilever, a sensitivity Sm ≈ 85 Hz/μm and a LOD of 70 ng were found, compatible with applications in PM mass detection.

Nenhuma / Desde que as singulares propriedades mecânicas e condutoras dos nanotubos de carbono (NCs) estão associadas a tubos individuais isolados, a dispersão e estabilização de seus feixes em diferentes líquidos são de extrema importância em estudos fundamentais e aplicados. Solventes do tipo amida são atualmente considerados os melhores candidatos, dentre os solventes orgânicos, à dispersão quantitativa dos feixes de nanotubos, sendo que a funcionalização das paredes dos tubos favorece essa dispersão em determinados meios. Amostras brutas de nanotubos de carbono são compostas por feixes contendo até centenas de tubos com distribuição em diâmetro, comprimento, quiralidade e caráter eletrônico, unidos por interações de van der Waals. Para a dispersão desses feixes, o potencial atrativo entre os tubos deve ser balanceado por um potencial repulsivo. Assim, o custo energético das interações nanotubosolvente, que depende fortemente da composição química da superfície dos tubos e das propriedades dielétricas do meio, precisa ser entendido. Teorias de solubilidade têm sido recentemente aplicadas no entendimento dos sistemas nanotubo-solvente. Nelas, a dispersão é favorecida quando os parâmetros de solubilidade do soluto e do solvente têm valores próximos. Nos parâmetros de Hansen, contribuições de energias dispersivas (dd), dipolares (dp) e de ligação de hidrogênio (dh) são consideradas nas interações intermoleculares. O parâmetro de Flory-Huggins (χ) estima a diferença de interação entre o soluto e o solvente, podendo ser expresso em termos dos parâmetros de Hansen. Neste trabalho, apresentamos um estudo sistemático da dispersão de nanotubos de carbono de parede única, como preparados e funcionalizados com grupos ácidos contendo oxigênio, em solventes do tipo amida. As interações nanotubos-solvente foram analisadas em termos dos parâmetros de solubilidade de Hansen e de Flory-Huggins. Por refluxo em solução de HNO3 diluída, quantidades similares (~ 0,3 mmol/g C) de grupos ácidos carboxílicos e hidroxílicos foram covalentemente introduzidos à superfície dos tubos, sem criar defeitos adicionais ou destruir tubos de diâmetros menores. Os materiais de partida e funcionalizado foram amplamente caracterizados por termogravimetria, microscopia eletrônica de varredura e transmissão, titulação potenciométrica e espectroscopias por dispersão de energia, Raman, na região do infravermelho e de fotoelétrons excitados por raios X. As dispersões obtidas por sonificação/centrifugação dos NCs, antes e após funcionalização, em N-metilpirrolidona (NMP), N,N-dimetilformamida (DMF), N,N-dimetilacetamida (DMA), Ndodecilpirrolidona (N12P) e ciclohexilpirrolidona (CHP) foram caracterizadas por espectroscopia de absorção óptica na região do ultravioleta-visível (UV-Vis). Em estudo de absorbância em função da concentração, foram estimados os limites de dispersão e os coeficientes de absorção dos nanotubos de carbono em cada solvente. A presença dos grupos funcionais aumentou a dispersabilidade dos tubos em NMP, DMF e DMA, mas diminuiu em N12P e CHP. Os coeficientes de absorção, entretanto, diminuíram para todos os solventes após oxidação, refletindo a diminuição da probabilidade da transição p-p* com a funcionalização e a interação com o solvente. Os parâmetros de solubilidade de Hansen e de interação de Flory-Huggins foram calculados para as amostras antes e após funcionalização, permitindo uma análise termodinamicamente quantitativa das interações intermoleculares nos sistemas estudados. Os valores dos parâmetros de Hansen obtidos para a amostra bruta foram dD = 18,0 MPa1/2, dP = 7,4 MPa1/2 e dH = 6,8 MPa1/2, enquanto aqueles para a amostra funcionalizada foram dD = 17,4 MPa1/2, dP = 12,0 MPa1/2 e dH = 9,2 MPa1/2. Em comparação com valores tabelados para os solventes, o parâmetro de energia dispersiva mostrou-se dominante na dispersão dos tubos não-funcionalizados, enquanto interações dipolares e ligações de hidrogênio exerceram uma maior influência na dispersão dos tubos funcionalizados com grupos oxigenados ácidos. Os parâmetros de interação de Flory-Huggins estimados mostraram que os sistemas com maior afinidade foram a amostra bruta dispersa no solvente CHP e a amostra funcionalizada dispersa nos solventes NMP, DMA e DMF.

A kinetic study of the pyrolysis of municipal solid waste (MSW) was carried out bythermogravimetric analysis (TGA). Different runs were performed at heating rates of 5, 10and 150C/min. The effect of the N2, CO2 and O2 gas with different combination in theprocess was also evaluated. The results show that the most weight loss was obtained whenthe MSW was treated at a temperature interval of (20-750)0C which led to a weigh loss of95%. The kinetic study of the pyrolysis process showed also the gas mixture used in theprocess effect also the activation energy of the process and the presence of the CO2 in theincreased the activation energy (Ea) to 56 kJ/mol. Higher concentration of CO2 in the processlead to increase in the activation energy which is not optimal for the reaction. The treated andthe untreated samples were incubated and the biological activity was observed. The resultsshow that the pretreated samples did not have any biological activity. From these results itcould be concluded that the thermal pretreatment could be an alternative way for of waste forlong period of time, which could have significant impact in i.e. for transportation anddurability during storage. / Program: Högskoleingenjörsutbildning i kemiteknik