Date of Award

2011

Document Type

Thesis

Degree Name

Master of Science (MS)

Department

Chemical Engineering

First Advisor

Ilias, Shamsuddin Dr.

Abstract

Pd-Cu composite membranes on microporous stainless steel substrate (MPSS) were fabricated by novel electroless plating (EP process. In conventional Pd-EP process, the oxidation-reduction reactions between Pd-complex and hydrazine result in evolution of NH3 and N2 gas bubbles. When adhering to a substrate surface and in the pores, these gas bubbles can hinder uniform Pd-film deposition, which results in dendrite growth leading to poor film formation. We addressed this problem by introducing cationic surfactant in the electroless plating process known as surfactant induced electroless plating (SIEP). The unique features of this innovation provide control of (1) Pd- and Cudeposition rate, and (2) Pd- and Cu-grain size distribution. The surfactant molecules play a key role in the plating process in tailoring grain size and the process of agglomeration by removing tiny gas bubbles through adsorption at the gas-liquid interface. The water soluble surfactants which have near neutral hydrophilic-lipophilic balance (HLB) value, apparently have a stronger capability of removing gas bubbles from the substrate surface and the pores. To verify the improvement of membrane performance after introducing surfactant in bath solution, Pd-Cu membranes are fabricated by both conventional electroless plating (CEP) and surfactant induced electroless plating (SIEP). The pre- and post-annealing characterizations of these membranes (Pd-Cu on MPSS substrate) were carried out by SEM, XRD, EDX, and AFM studies. The SEM images showed a xvii significant improvement of the membrane surface morphology, in terms of metal grain structures and grain agglomeration compared to the membranes fabricated by conventional EP process. The SEM images and helium gas-tightness studies indicated that dense and thinner films of Pd-Cu membranes can be produced with shorter deposition time using surfactant. From cross-sectional SEM and EDX studies, the alloying of Pd-Cu was confirmed at the annealing condition of about 773 K with different annealing time in hydrogen environment. These membranes were also studied for hydrogen perm-selectivity as a function of temperature and feed pressure. Finally, long term thermal stability of Pd-Cu membrane fabricated by SIEP method was tested as a function of H2 flux.

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