Porous Nickel Support Research Articles

Ultra-thin Ni dense membrane prepared by polishing treatment of porous nickel support for high-temperature H2 separation

Ultra-thin nickel dense membranes (∼0.5 μm) were developed by polishing treatment of porous nickel supports. The polishing treatment involved the use of 400 grit sand paper, 1000 grit, and 1500 grit, which was able to remove the surface pores due to the ductility of the PNS. The hydrogen permeation test showed that 4.53×10−2 mol m−2 s−1 of hydrogen permeation flux through the membrane could be achieved at a temperature of 973K and a pressure difference of 136 kPa. The nitrogen leakage tests confirmed that there were no pinholes on the surface of the ultra-thin nickel dense membrane.

Characteristics of dense palladium alloy membranes formed by nano-scale nucleation and lateral growth

In this study, fine, uniform nano-scale layers of Pd were deposited by an advanced sputtering system with high vacuum, high temperature, and high power to overcome the limitations of existing sputtering systems. Thin Pd films formed by continuous sputtering exhibited vertical growth, combined with the lateral growth of Pd clusters due to the improved reactivity of Pd nano-particles, the diffusion of activated Pd atoms at high temperature, and the self-catalyst effect of the porous nickel support (PNS). Additionally, uniformly dense Pd structures were formed by the successive deposition of Pd particles, and Pd clusters formed with a uniform density. A fine Pd–Au alloy membrane manufactured by this advanced sputtering system not only improved hydrogen selectivity due to the pinhole-free membrane surface but also increased hydrogen permeability because the thin film had a thickness less than 6µm and a uniformly fine grained structure. Additionally, the Pd alloy membrane exhibited enhanced durability because the inter-diffusion of the support component to the membrane surface was prevented by the low temperature of the heat treatment for crystallization and the low alloying temperature.

Pd–Cu alloy membrane deposited on CeO2 modified porous nickel support for hydrogen separation

In this study, the hydrogen permeation behavior of a Pd93–Cu7 alloy membrane deposited on ceria-modified porous nickel support (PNS) was evaluated. PNS, which has an average pore size of 600 nm, was modified by alumina sol. Alumina sol was prepared using precursors that had a mean particle size of 300 nm. Alumina-modified PNS was further treated with ceria sol modification to produce a smoother surface morphology and narrow surface pores. A 7 μm thick Pd93–Cu7 alloy membrane was made on an alumina-modified PNS and a ceria-finished membrane was fabricated by magnetron sputtering followed by Cu-reflow at 700 °C for 2 h. SEM analysis showed that the membrane deposited on a ceria-finished PNS contained more clear grain boundaries than the membrane deposited on the alumina-modified PNS. The membrane was mounted in a stainless steel permeation cell with a gold-plated stainless steel O-ring. Permeation tests were then conducted using pure hydrogen and helium at temperatures ranging from 673 to 773 K and feed side pressures ranging from 100 to 400 kPa. These tests showed that the membrane had a hydrogen permeation flux of 2.8 × 10−1 mol m−2 s−1 with H2/He selectivity of >50,000 at a temperature of 773 K and pressure difference of 400 kPa.

Ceramics used as intermetallic diffusion barriers in Pd-based composite membranes sputtered on porous nickel supports

Abstract A ceramic barrier was introduced onto the surface of a porous nickel support (PNS) to prevent intermetallic diffusion. Al 2 O 3 and ZrO 2 were deposited on the PNS by RF sputtering to a thickness of 200 nm. Pd and Au were then deposited by DC and RF sputtering with thicknesses of 3 μm and 0.5 μm, respectively, on the PNS with the diffusion barrier. The permeation measurement was carried out using hydrogen and helium at 723 K and a pressure difference of 100–2000 kPa. The gas permeation tests confirmed that the hydrogen permeation flux increased with increasing pressure difference and reached 4.07 mol m −2 s −1 at 2000 kPa with an H 2 /He selectivity of more than 5000. The ZrO 2 barrier membrane provided a flux of 1.5 times higher than that achieved by the Al 2 O 3 barrier membrane. The sputtering method was successful in depositing intermetallic diffusion barriers and Pd–Au alloy layers.

팔라듐 합금 수소 분리막의 전처리에 관한 연구

A Pd-based hydrogen membranes for hydrogen purification and separation need high hydrogen perm-selectivity. The surface roughness of the support is important to coat the pinholes free and thin-film membrane over it. Also, The pinholes drastically decreased the hydrogen perm-selectivity of the Pd-based composite membrane. In order to remove the pinholes, we introduced various surface pre-treatment such as alumina powder packing, nickel electro-plating and micro-polishing pre-treatment. Especially, the micro-polishing pretreatment was very effective in roughness leveling off the surface of the porous nickel support, and it almost completely plugged the pores. Fine Ni particles filled surface pinholes with could form open structure at the interface of Pd alloy coating and Ni support by their diffusion to the membrane and resintering. In this study, a surface pore-free Pd-Cu-Ni ternary alloy membrane on a porous nickel substrate was successfully prepared by micro-polishing, high temperature sputtering and Cu-reflow process. And permeation and leak tests showed that the Pd-Cu-Ni ternary alloy hydrogen membrane achieved both high permeability of permation flux and infinite selectivity.

Hydrogen recovery from ethylene mixture with PD-AU composite membrane

Hydrogen separation from the refinery off-gas of the ethylene decomposition was carried out with Pd-1wt.%Au alloy membranes deposited on a porous nickel support using the sputtering and polishing method. In order to verify the effect of ethylene on the membrane, hydrogen permeation tests were carried out with 5% ethylene mixtures at temperatures ranging from 573 to 673 K and pressure differences ranging from 500 to 1500 kPa. Hydrogen permeation tests, which were carried out with the membranes that had an effective area of 16.6 cm2, revealed that the ethylene mixture did not affect hydrogen permeation behavior when the feed streams were 3000 ml min−1 and the pressure difference was 500 kPa at 673 K. As the pressure difference and temperature increased and the feed flow rate decreased, hydrogen permeation flux became less than ideal, indicating that depletion was a major factor in the hydrogen permeation behavior. From the aspect of process design, the membrane with an effective area of 16.6 cm2 could enrich 5% ethylene of 2000 ml min−1 up to 76, 80, and 82% at 573 K, 623 K, and 673 K, respectively with a hydrogen recovery ratio of >96% at a pressure difference of 1500 kPa.

Pd-Cu alloy membrane deposited on alumina modified porous nickel support (PNS) for hydrogen separation at high pressure

This study reports on the hydrogen permeation properties of Pd-Cu alloy membranes at high pressures. A 7 μm thick Pd-Cu alloy membrane was prepared on an alumina-modified porous nickel support (PNS) by our developed magnetron sputtering and Cu-reflow method at 700 °C for 2 hours. The membrane was mounted in a stainless steel permeation cell with a gold-plated stainless steel O-ring. Helium leak testing confirmed that the membrane and membrane module were free of defects. Permeation tests were then conducted using hydrogen at temperatures in the range from 678 to 816 K with a transmembrane pressure difference of 1–20 bars, which showed that the membrane had a hydrogen permeation flux of 1.06 mol m−2 s−1 at a temperature of 816 K and a pressure difference of 20 bars. EDX analysis was carried out after hydrogen permeation test at 816 K and showed that there was no intermetallic diffusion between the Pd-Cu layer and PNS because the alumina layer inhibited it effectively.

Module configuration in CO 2 capture using Pd-based composite membranes

In this study, the effect of module configuration on the performance of Pd-based membrane devices was examined using a Pd-Au composite membrane deposited on a porous nickel support. Hydrogen permeation flux, recovery, and CO 2 enrichment were experimentally examined using two different modules. The module configuration that had a narrower space between the surface of the membrane and cover plate provided a large linear flow velocity of the gas mixture, which allowed for a reduction in the concentration polarization. The CO 2 enrichment capacity of the membrane module with a space distance of 0.4 mm was 4 times higher than the module with a space distance of 2.5 mm. In regards to the process design, the membrane with an effective area of 16.6 cm 2 could enrich 40% of the CO 2 at a flow rate of 2000 ml min −1 up to 87% with a hydrogen recovery ratio of >90% at 673 K and a total feed pressure of 1600 kPa.

Pd–Cu–Ni Ternary Alloy Membrane with High Temperature Durability for Hydrogen Separation and Purification

For successful commercialization, Pd-based membranes used for hydrogen purification and separation need stable thermal durability at high temperatures. In order to meet this requirement, Pd–Cu–Ni ternary alloy hydrogen membranes with a saturated surface concentration were fabricated on a 1-in. porous nickel support using high temperature sputtering and Cu-reflow processes. These membranes had considerably enhanced thermal durability because of their thermally stable surface concentration and morphology.

Fabrication and characterization of Pd/Nb 40Ti 30Ni 30/Pd/porous nickel support composite membrane for hydrogen separation and purification

A porous nickel support was successfully prepared by uniaxial compression of nickel powders. Microstructures and mechanical properties of Nb 40Ti 30Ni 30 membranes fabricated by magnetron sputtering were investigated. Deposited and annealed Nb 40Ti 30Ni 30 membranes consisted of amorphous and crystalline phases, respectively. Higher base temperature was shown to increase the hardness and elastic modulus of the Nb 40Ti 30Ni 30 membrane. Pd/Nb 40Ti 30Ni 30/Pd/porous nickel support composite membranes were then fabricated using a multilayer magnetron sputtering method. The hydrogen permeability of the composite membranes with amorphous and crystallized Nb 40Ti 30Ni 30 metal layer was measured and compared with that of self-supported Nb 40Ti 30Ni 30 and Pd alloys. Solid-state diffusion was shown to be the rate-controlling factor when the thickness of the Nb 40Ti 30Ni 30 layer was about 12 μm or greater, while other factors were in effect for thinner layers (such as 6 μm). The Pd/Nb 40Ti 30Ni 30/Pd/porous nickel support composite membrane exhibited excellent permeation capability and satisfactory mechanical properties. It is a promising new permeation membrane that could replace Pd and PdAg alloys for hydrogen separation and purification.

Formation of a defect-free Pd–Cu–Ni ternary alloy membrane on a polished porous nickel support (PNS)

In order to decrease its resistance we enlarged the pore size of a porous nickel support (PNS) by using nickel powder with a larger particle size. The gas permeation test showed that this increased the gas permeation flux compared with the previous support. To make up for the various disadvantages, such as the enlarged surface roughness and pore size, a polishing process was introduced with sandpaper, followed by wet polishing with alumina powder. The polishing treatment was very effective in leveling off the surface of the porous nickel support, but it almost completely plugged the pores. Those pores blocked by the polishing process could be regenerated during Cu-reflow at 973 K by the upward diffusion of nickel and in this way a 12 μm defect-free Pd–Cu–Ni ternary alloy film was formed on the polished porous nickel support. Furthermore, we were able to obtain a three times higher hydrogen permeability than that reported in previous studies, because of the decreased support resistance of the porous nickel support.

Long-term hydrogen permeation tests of Pd–Cu–Ni/PNS with temperature cycles from room temperature to 773 K

Pd–Cu–Ni ternary alloy membranes were fabricated on a porous nickel support by sputtering followed by the Cu-reflow method. The weight composition of Pd:Cu:Ni was 88.9:7.4:3.7 and the thickness was 12 μm. α–β phase transition tests were carried out using hydrogen gas in the temperature range from 373 to 623 K using feed side pressures of 0.052 and 0.138 MPa. There were neither peaks nor shoulders in the hydrogen flux across the entire temperature range, meaning that the α–β phase transition did not occur below the critical points of the Pd–H system, i.e. 565 K, 1.97 MPa. The durability of the membranes was demonstrated by performing temperature cycles from room temperature to 773 K at a feed side pressure of 0.138 MPa and this was attributed to the phase stability of the α-phase even at room temperature.

The study of Pd–Cu–Ni membrane deposited on porous nickel support with Cu-reflow technique

The study of Pd–Cu–Ni membrane deposited on porous nickel support with Cu-reflow technique

The study of a new porous nickel support for palladium-based alloy membrane

The study of a new porous nickel support for palladium-based alloy membrane

The effect of support resistance on the hydrogen permeation behavior in Pd–Cu–Ni ternary alloy membrane deposited on a porous nickel support

This paper shows the effect of support resistance on the pressure exponent. Pd–Cu–Ni ternary alloy film is formed on the newly developed porous nickel support which has Knudsen diffusion. Permeation flux of hydrogen was measured at 673, 723 and 773 K under two different permeation directions, i.e. support to film (SF mode) and film to support (FS mode). It was found that the permeation direction had an effect on the hydrogen permeation flux and the pressure exponent as well. For both of permeation directions, the interface pressure of Pd alloy film and porous nickel support was determined and it was affected by permeation direction. The obtained interface pressure was used to clarify the reason why the pressure exponent was deviated from the Sieverts’ law and it was found that the reason is the support resistance rather than surface reaction.

Development of a new porous metal support of metallic dense membrane for hydrogen separation

Porous nickel support was successfully made by uniaxial pressing of nickel powder for gases separation or metal support of Pd and/or Pd-alloy dense membrane. Since the used nickel powder was prepared by pulsed wire evaporation (PWE) method, it has a good thermal stability. Furthermore, a broad particle size distribution from 20 to 5000 nm cleared out the powder mixing step in the procedures of fabrication of porous nickel support. From the pore characterization and SEM analysis, it was clarified that the fabricated porous nickel support had so small uniform pore size of 33 nm and very smooth surface so that it can be offered as new material for the substrate of palladium and/or palladium-based alloy membrane. As a result of single gas permeation test using H 2 and N 2, permeance was constant with increasing transmembrane pressure difference and the selectivity was around 3.7, which indicated that the gas permeation was contributed by Knudsen diffusion. Since it has thermal resistance up to 650 °C, sputtering followed by cupper reflow could be applied to the formation of Pd–Cu–Ni ternary film on it. Furthermore, it showed the defect-free dense membrane characteristic.

Characterization of Pd–Cu–Ni ternary alloy membrane prepared by magnetron sputtering and Cu-reflow on porous nickel support for hydrogen separation

Pd–Cu–Ni alloy membrane was successfully deposited 4 μm in thickness on porous nickel support by multitarget sputtering and Cu-reflow technique. The surface of porous nickel support needed not to be modified because it has very uniform and small pore distribution as 33 nm. From the XRD and SEM analysis, it was clarified that the fabricated Pd–Cu–Ni ternary alloy film had Pd–Cu–Ni alloy character and no defects on the surface of thin membrane. The weight composition of Pd:Cu:Ni was 89:4.5:6.5 from EDS analysis. As a result of single gas permeation test using H 2 and N 2, hydrogen permeance increased with an increase of operating temperature and transmembrane pressure difference. Furthermore, hydrogen separation factor with single gas test was infinity indicating pinhole-free palladium-based alloy membrane. In additions, it was so stable that the morphology of the surface was not changed and there were no indications of metal interdiffusion during time-on-stream test for 10 days with the cycling of operating temperature and transmembrane pressure difference.