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Title: Sintering of Mixed-Conducting Composites for Hydrogen Membranes From Nanoscale Co-Synthesized Powders

Abstract

The potential for highly selective, nongalvanic permeation of hydrogen through dense mixed conducting composites at elevated temperatures makes them attractive as hydrogen separation membranes. The glycine-nitrate combustion synthesis technique has been used to co-synthesize a cation-doped barium cerate protonic conducting phase together with a metallic nickel electronic conducting phase (15-35 vol% Ni). Co-synthesis of these phases results in an intimately mixed powder with particle sizes on the order of 10 nm. DTA/TGA of all as-synthesized compositions determined that a calcination temperature of 1000°C was required for full reaction of the cerate components. DTA/TGA and sintering shrinkage dilatometry were performed on calcined powders to determine that a sintering temperature of 1250°C would be adequate for achieving >90% relative density in all compositions. Bars of the material containing 25 vol% Ni were reduced at three different points in the heat treatment process (e.g., before, during, or after sintering). It was determined that there was less porosity in the sample reduced during sintering than any other. It was also seen on SEM that the primary grain size, regardless of when reduction occurred compared to sintering of the material, is less than 5 µm.

Authors:
; ; ; ; ; ;
Publication Date:
Research Org.:
Pacific Northwest National Lab. (PNNL), Richland, WA (United States)
Sponsoring Org.:
USDOE
OSTI Identifier:
901468
Report Number(s):
PNNL-SA-48245
TRN: US200714%%58
DOE Contract Number:
AC05-76RL01830
Resource Type:
Conference
Resource Relation:
Conference: Processing and manufacturing of advanced materials international conference; THERMEC 2006, Jul 5th, 2006, Vancouver, Canada. Materials Science Forum, 539-543(Part. 2):1413-1420
Country of Publication:
United States
Language:
English
Subject:
08 HYDROGEN; BARIUM; CALCINATION; COMBUSTION; DILATOMETRY; GRAIN SIZE; HEAT TREATMENTS; HYDROGEN; MANUFACTURING; MEMBRANES; NICKEL; PARTICLE SIZE; POROSITY; PROCESSING; SHRINKAGE; SINTERING; SYNTHESIS; mixed-conducting composite; H2 membrane

Citation Formats

Canfield, Nathan L., Crum, Jarrod V., Matyas, Josef, Bandyopadhyay, Amit, Weil, K. Scott, Pederson, Larry R., and Hardy, John S. Sintering of Mixed-Conducting Composites for Hydrogen Membranes From Nanoscale Co-Synthesized Powders. United States: N. p., 2007. Web.
Canfield, Nathan L., Crum, Jarrod V., Matyas, Josef, Bandyopadhyay, Amit, Weil, K. Scott, Pederson, Larry R., & Hardy, John S. Sintering of Mixed-Conducting Composites for Hydrogen Membranes From Nanoscale Co-Synthesized Powders. United States.
Canfield, Nathan L., Crum, Jarrod V., Matyas, Josef, Bandyopadhyay, Amit, Weil, K. Scott, Pederson, Larry R., and Hardy, John S. Fri . "Sintering of Mixed-Conducting Composites for Hydrogen Membranes From Nanoscale Co-Synthesized Powders". United States. doi:.
@article{osti_901468,
title = {Sintering of Mixed-Conducting Composites for Hydrogen Membranes From Nanoscale Co-Synthesized Powders},
author = {Canfield, Nathan L. and Crum, Jarrod V. and Matyas, Josef and Bandyopadhyay, Amit and Weil, K. Scott and Pederson, Larry R. and Hardy, John S.},
abstractNote = {The potential for highly selective, nongalvanic permeation of hydrogen through dense mixed conducting composites at elevated temperatures makes them attractive as hydrogen separation membranes. The glycine-nitrate combustion synthesis technique has been used to co-synthesize a cation-doped barium cerate protonic conducting phase together with a metallic nickel electronic conducting phase (15-35 vol% Ni). Co-synthesis of these phases results in an intimately mixed powder with particle sizes on the order of 10 nm. DTA/TGA of all as-synthesized compositions determined that a calcination temperature of 1000°C was required for full reaction of the cerate components. DTA/TGA and sintering shrinkage dilatometry were performed on calcined powders to determine that a sintering temperature of 1250°C would be adequate for achieving >90% relative density in all compositions. Bars of the material containing 25 vol% Ni were reduced at three different points in the heat treatment process (e.g., before, during, or after sintering). It was determined that there was less porosity in the sample reduced during sintering than any other. It was also seen on SEM that the primary grain size, regardless of when reduction occurred compared to sintering of the material, is less than 5 µm.},
doi = {},
journal = {},
number = ,
volume = ,
place = {United States},
year = {Fri Mar 30 00:00:00 EDT 2007},
month = {Fri Mar 30 00:00:00 EDT 2007}
}

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  • A powder comprised of nickel oxide and proton-conducting Nd- and Zr-doped barium cerate with a particle size on the order of 10 nm has been co-synthesized using the glycine-nitrate combustion process. The two compositions are intimately mixed with no significant elemental substitution between them after synthesis. The resulting powder must be calcined at 1000 degrees C to ensure complete reaction of the cerate components. Among the barium cerate compositions investigated, the 30 per cent Zr- and 15 per cent Nd-doped material exhibited the best combination of chemical stability in CO2 and conductivity in hydrogen environments. At least 35 vol percentmore » Ni is required to achieve percolation in the composites. When sintering is carried out in an atmosphere which promotes reduction of nickel oxide to nickel metal, the result is a mixed conducting composite which has potential use as a hydrogen separation membrane. Composites with a relative density of 98.9 per cent and submicron grains have been prepared by hot pressing.« less
  • Two-phase powders for making mixed conducting cermet hydrogen separation membranes have been co-synthesized using the glycine-nitrate combustion technique. The two components include a proton conducting barium cerate-based ceramic and nickel oxide, which is subsequently reduced to electron conducting nickel metal. The particle size of the resulting powder is on the order of 10 nm in size and the two phases are intimately mixed. Analysis of energy dispersive x-ray (EDX) spectra taken during transmission electron microscopy (TEM) suggests that the elements partition into the compositions for which they were intended. X-ray diffraction (XRD) confirms that the desired barium cerate and nickelmore » oxide phases are formed exclusively during synthesis and calcination. The composition of the cermet was further refined by determining (1) the combination of Zr- and Nd-doping levels in the barium cerate phase that impart stability at elevated temperatures in a carbon dioxide atmosphere, and (2) the percolation threshold of Ni in the composite.« less
  • PZT (PbTi{sub 1-x}Zr{sub x}O{sub 3}) powders were hydrothermally produced at 200{degrees}C for 24 hrs, from a solution containing Ti(OH){sub 4}{center_dot}xH{sub 2}O, ZrOCl{sub 2}, Pb(CH{sub 3}COO){sub 2} and Na0H. PZT powder was also produced by the solid-state sintering method. The powders from both the hydrothermal method and the solid-state reaction method were pressed and subsequently sintered ranging between 1100{degrees}C and 1250{degrees}C for 2 hrs. The microstructures, density, grain size, K value, D value, Kp value, and Qm value of the sintered PZT ceramics were measured and compared with each other. Large density and grain size differences were found in ceramics producedmore » between 1100{degrees}C and 1250{degrees}C from the hydrothermal powders and by the solid-state reaction powders. The hydrothermal powder was much more sinterable than powders produced from the solid-state reaction method and grain growth occurred more easily. The hydrothermal PZT ceramics were observed to have a higher K value, higher Kp value, lower D value, and lower Qm value, and were electrically {open_quote}softer{close_quote} than the ceramics produced from the solid-state reaction powders at the same chemical composition.« less
  • The electronic transference numbers of BCY were relatively low when compared with the protonic numbers. At 800 C, a hydrogen flux of only 0.02 cm{sup 3}/min/cm{sup 2} was obtained in an {approx} 2-rnm-thick BCY sample by short-circuiting the two Pt electrodes. We have developed a novel composite system with improved electronic transport, and preliminary measurements indicate that the new membrane materials can be used in a nongalvanic mode to separate hydrogen from gas mixtures. A maximum flux of 0.12 cm{sup 3}/min/cm{sup 2} has been measured at 800 C in the composite material operated in the nongalvanic mode. Currently, work ismore » underway to further enhance the hydrogen flux in the composite membrane materials.« less
  • SrCeO{sub 3}- and BaCeO{sub 3}-based proton conductors have been prepared and their transport properties have been investigated by impedance spectroscopy in conjunction with open circuit voltage and water vapor evolution measurements. BaCe{sub 0.8}Y{sub 0.2}O{sub 3-{delta}} exhibits the highest conductivity in a hydrogen-containing atmosphere; however, its electronic conductivity is not adequate for hydrogen separation in a nongalvanic mode. In an effort to enhance ambipolar conductivity and improve interfacial catalytic properties, BaCe{sub 0.8}Y{sub 0.2}O{sub 3-{delta}} cermets have been fabricated into membranes. The effects of ambipolar conductivity, membrane thickness, and interfacial resistance on permeation rates have been investigated. In particular, the significance ofmore » interfacial resistance is emphasized.« less