Thesis (Ph.D.)--University of Wollongong, 2005. / Typescript. Includes bibliographical references.

Thesis (Master)--İzmir Institute Of Technology, İzmir, 2005. / Helical polymers, conjugated polymers, allene. Includes bibliographical references (leaves. 53-55).

Thesis (M.S.)--West Virginia University, 1999. / Title from document title page. Document formatted into pages; contains xi, 96 p. : ill. (some col.) Includes abstract. Includes bibliographical references.

Thesis (Ph. D.)--Ohio State University, 2005. / Title from first page of PDF file. Document formatted into pages; contains xvi, 145 p.; also includes graphics (some col.) Includes bibliographical references (p. 137-145).

Thesis (Ph. D.)--Chemistry and Biochemistry, Georgia Institute of Technology, 2005. / Anselm Griffin, Committee Member ; Uwe Bunz, Committee Chair ; David Collard, Committee Member ; Laren Tolbert, Committee Member ; Joseph Perry, Committee Member.

Thesis (Ph. D.)--University of Oregon, 2004. / Typescript. Includes vita and abstract. Includes bibliographical references (leaves 173-178). Also available for download via the World Wide Web; free to University of Oregon users.

Thesis (Ph. D.)--Drexel University, 2007. / Includes abstract and vita. Includes bibliographical references (leaves 275-279).

In this study the development of an improved electrochemical fuel cell sensor for the detection of low-levels of formaldehyde vapour is described. Current fuel cell sensors used in the commercial Formaldemeter™ instrument lack sensitivity, respond to methanol, and show an interference response to humidity. For the detection and accurate determination of low-level concentrations of formaldehyde an improvement in these characteristics is essential. Two routes were investigated to achieve these requirements. Firstly the oxygen reduction reaction at the cathode was replaced with that of a conducting polymer, polyaniline (P ANI). Before construction of the fuel cells the stability and open circuit behaviour of various P ANI films were investigated in order to assay their suitability as a cathode material in a fuel cell application. Based on these results various fuel cells containing P ANI as the cathode were prepared and incorporated into the FormaldemeterTM. The cells were then evaluated using a calibrated vapour stream. Fuel cells containing a Pt-black anode and a P ANI/SOlcoated Pt-black cathode in H2S04 electrolyte displayed a significant improvement in sensitivity, selectivity and a reduced humidity response. In addition a fast response time, excellent reproducibility and a long shelf life was demonstrated. It is proposed that a P ANI film coated on Pt-black behaves as a more stable electron sink for the cathodic reaction instead of the oxygen reduction reaction which is dependent on the diffusion of oxygen. The fast fuel cell response time is explained by the fast switching of PAN I « lOJls). In the second part of the work, the effect of changing fuel cell catalyst was investigated. Initially, the electrocatalytic activity of various noble metals and alloys electrodeposited on glassy carbon were investigated. Based on these results several fuel cell electrodes were prepared and characterised by SEM and EDAX. Fuel cells were then constructed and their performance evaluated. Cells made up of 50:50 % atomic weight ratio of platinum and palladium showed that while the fuel cell was active towards low levels of formaldehyde, its response to equivalent levels of methanol was very small.

Made available in DSpace on 2014-06-11T19:35:06Z (GMT). No. of bitstreams: 0 Previous issue date: 2009-08-28Bitstream added on 2014-06-13T20:06:26Z : No. of bitstreams: 1 dias_ds_dr_araiq.pdf: 2168209 bytes, checksum: 92fc6fd83876c2b2bf91b5e580b4f894 (MD5) / Coordenação de Aperfeiçoamento de Pessoal de Nível Superior (CAPES) / Com o avanço da tecnologia e industrialização houve um aumento de produtos descartáveis de uso doméstico ou industrial. A partir de então, tem início o trabalho de coleta seletiva e a reutilização desses produtos nas mais diversas áreas. Os “plásticos” são os produtos mais agressivos ao meio ambiente devido a sua difícil degradabilidade. Entre eles está o PET (polietileno tereftalato). Sabendo que garrafas PET pós-consumo (PET-R) é um problema muito sério no meio ambiente devido a sua alta resistência a degradação, pensou-se na sua reutilização, preparando blendas poliméricas com poli(3- hidroxibutirato), (PHB), que pertence a uma família de polímeros biodegradáveis, os polihidroxialcanoatos (PHAs) produzidos a partir de matéria-prima renovável como o açúcar da cana, matérias amiláceas e óleos vegetais. O PHB apresenta desvantagens como alto grau de cristalinidade e instabilidade térmica. Para melhorar essas características, o preparo de blendas poderia aliar as características dos polímeros convencionais, que são poucos degradáveis, mas possuem boas propriedades mecânicas com os polímeros biodegradáveis. Esse trabalho tem como objetivo a obtenção de blendas poliméricas na forma de mistura mecânica e na forma de filmes a partir de solução de PET-R e PHB (PHBPET-R) em várias proporções de massa As misturas obtidas foram caracterizadas utilizando Termogravimetria (TG), Calorimetria Exploratória Diferencial (DSC), difratometria de raios X, espectrometria na região do infravermelho (FTIR), Microscopia Eletrônica de Varredura (MEV) e Microscopia Óptica (MO). Os resultados obtidos por TG, DSC, MEV e MO evidenciam que amostras obtidas por métodos e proporções diferentes possuem comportamento térmico e morfologia diferente. Os parâmetros cinéticos foram obtidos utilizando o modelo de Flynn - Wall e Ozawa e a partir... / With the advancement of technology and industrialization is verified an increase of household disposable products and industrial. The disposable products and reused of in several field. The plastic products are harmful to the environment due to their hand degradability, among them is the PET (polyethylene terephthalate). Once that post- consumer PET bottles (PET-R) constitutes a very serious problem in the environment due to its high resistance to degradation, it was thought in his re-obtain polymer blends with poly (3-hydroxybutyrate) (PHB), which belongs to a family of biodegradable polymers, the polyhydroxyalkanoates (PHAs) produced from renewable raw materials such as sugar from cane, vegetable oils and starch materials. The PHB presents disadvantages such as high degree of crystallinity and thermal instability. To improve these characteristics, a solution would be the preparation of blends. Thus, one can combine the characteristics of conventional polymers, which are few degradable but have good mechanical properties with biodegradable polymers. The aim of this study was investigate the synthesis of polymer blends in the form of mechanical mixture and in the form of films from solution between PET and R-PHB (PHBPET-R) in various proportions of mass. The mixtures obtained were characterized using thermogravimetry (TG), differential scanning calorimetry (DSC), X ray diffraction, spectroscopy in the infrared (FTIR), scanning electron microscopy (SEM) and optical microscopy (OM). The results obtained by TG, DSC, SEM and OM showed that samples obtained by different methods and proportions present different thermal behavior and morphology. The kinetic parameters were obtained using the model of Flynn - Wall and Ozawa and from the values of activation energy (Ea) and pre-exponential factor log A were evaluated the change of kinetic energy (Ea) on alpha (α) and ... (Complete abstract click electronic access below)

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