Title page for ETD etd-011006-123013

Document Type	dissertation
Author Name	Guazzone, Federico
URN	etd-011006-123013
Title	Engineering of Substrate Surface for the synthesis of Ultra-Thin Composite Pd and Pd-Cu Membranes for H2 Separation
Degree	PhD
Department	Chemical Engineering
Advisors	Yi Hua Ma, Advisor Nikolaos K. Kazantzis, Committee Member Satya Shivkumar, Committee Member
Keywords	Hydrogen synthesis Pd-Cu metallic membranes Pd
Date of Presentation/Defense	2005-12-15
Availability	unrestricted
Abstract This work describes a novel technique to prepare ultra-thin composite Pd–porous metal membranes for H2 separation. This novel technique consists of the gradual smoothing of the Porous Metal (PM) support’s surface with several layers of pre-activated alumina particles of different sizes. The deposition of coarse, fine and ultra-fine alumina particles resulted in the narrowing of the PM’ surface pore size distribution. The excellent surface smoothness achieved after the grading of the PM ‘s surface support allowed for the preparation of gas tight Pd layers as thin as 5.6?m. The Pd layers were extremely uniform due to the presence of the grade layer and strongly attached to the support. Composite Pd membranes prepared on graded supports showed H2 permeance as high as 50 m3/(m2 h bar0.5) at 500ºC and ideal selectivities (H2/He) as high as 27000. Moreover, the H2 permeance and ideal selectivity were stable over 1100 hours at 500ºC in H2 atmosphere. Composite Pd-Cu membranes showed H2 permeance as high as 30 m3/(m2 h bar0.5) at 450ºC and ideal selectivities (H2/He) as high as 900. The H2 permeance and ideal selectivity of Pd-Cu membranes were stable over 500 hours at 450ºC in H2 atmosphere. The outstanding long-term H2 permeance and ideal selectivity stability of all composite Pd and Pd-Cu membranes represented a breakthrough in composite Pd membrane synthesis. The thermal stresses arising from the mismatch in the coefficient of thermal expansion between the Pd film and the support were determined by means of x-ray diffraction. The results indicated that the release of stresses began to occur at temperatures close to 400ºC. Also, the release of stresses took place with a visible sintering of Pd clusters within the thin Pd film. The stresses due to the absorption of H2 were also studied and modeled. It was estimated that the maximum compressive stress under which these composite Pd membranes were characterized was equal to 260 MPa.
Files	Guazzone1.pdf Guazzone2.pdf Guazzone3.pdf Guazzone4.pdf Guazzone5.pdf Guazzone6.pdf Guazzone7.pdf Guazzone8.pdf

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