Preparation of hierarchical porous metallic materials via deposition of microporous particles

• A new method was used to fabricate hierarchical porous metals.
• The pore structure and its formation mechanism were investigated.
• Bimodal pores were formed in as-sprayed molybdenum deposit.
• Nanopores were produced in semi-molten particles by reducing oxides.

It is the first time to report the preparation of hierarchical porous molybdenum (Mo) metal materials containing interconnected pores with a wide size range from sub-millimeter down to micrometer and nanometer scale. Microporous Mo particles were deposited in bimodal molten states, i.e. limited-molten and semi-molten state, by thermal spraying. In as-sprayed coatings, hierarchical macro/microporous structures were produced with macropores formed among solid particles and micropores remained in limited-molten particles. After annealing in a reductive atmosphere, Mo oxides inside semi-molten particles were reduced and nanometer pores were further created. Therefore, the as-received deposits exhibited multi-modal hierarchical pores with high open porosity and high specific surface area, which are promising for functional applications.

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