Thin robust Pd membranes for low-temperature application.

Area of Science:

• Materials Science
• Chemical Engineering
• Hydrogen Technology

Background:

• Hydrogen embrittlement causes structural failure in pure palladium (Pd) membranes, restricting their use to temperatures above 293 °C.
• Understanding the influence of membrane geometry on hydrogen embrittlement resistance is crucial for expanding the operational range of Pd membranes.

Purpose of the Study:

• To investigate the correlation between membrane geometry and hydrogen embrittlement resistance in ultrathin pure Pd membranes.
• To evaluate the performance of different Pd membrane geometries under hydrogen exposure at various temperatures.

Main Methods:

• Fabrication and testing of ultrathin pure Pd membranes with varying geometries (tubular and hollow fiber).
• Exposure of membranes to hydrogen (H₂) at room temperature and during repeated heating/cooling cycles.
• In situ X-ray diffraction (XRD) analysis to assess lattice strain and residual stresses.

Main Results:

• Thin tubular Pd membranes (2.7–6.3 μm thickness, 4–12 mm o.d.) experienced immediate structural destruction when exposed to H₂ at room temperature.
• Thin hollow fiber Pd membranes (thickness < 4 μm, 2 mm o.d.) demonstrated strong resistance to hydrogen embrittlement below 100 °C.
• Hollow fiber membranes withstood repeated heating/cooling cycles (up to 10 °C min^-1) under H₂ atmosphere without structural degradation.

Conclusions:

• Hollow fiber geometry significantly enhances hydrogen embrittlement resistance in ultrathin pure Pd membranes at lower temperatures.
• Reduced lattice strain gradients and lower residual stresses in hollow fiber structures contribute to improved stability during the α-β phase transition.
• The findings indicate a promising potential for hollow fiber Pd membranes in low-temperature hydrogen separation applications.