Exploring nucleation mechanisms in the hydrogen reduction of MoO2 to Mo

S. Rainer; M. G. Willinger; E. Willinger; M. O'Sullivan; H. Huppertz

doi:10.1016/j.ijrmhm.2025.107615

Exploring nucleation mechanisms in the hydrogen reduction of MoO₂ to Mo

S. Rainer
, M. G. Willinger
, E. Willinger
, M. O'Sullivan
, H. Huppertz

Chair of Electron Microscopy with research emphasis on Energy Materials

University of Innsbruck
Technical University of Munich
Metallwerk Plansee

Research output: Contribution to journal › Article › peer-review

Abstract

The nucleation of various MoO₂ starting materials was investigated on a laboratory scale during the second reduction step from MoO₂ to Mo of the two-step reduction process from MoO₃ to Mo. It was found that a certain proportion of γ-Mo₄O₁₁ or a higher potassium content in the MoO₂ samples as well as the addition of water to the hydrogen gas stream led to a shift from the pseudomorphic transformation towards the CVT process at a low reduction temperature of 900 °C. Not only spherical/polyhedral Mo nuclei but also rod-shaped nuclei were detected for the first time using the γ-Mo₄O₁₁ containing MoO₂ starting material after a short reduction time and subsequent cooling in Ar gas flow. The influence of an increased potassium content in the γ-Mo₄O₁₁ containing MoO₂ samples on the nucleation was also investigated. Additionally, a mechanism for the formation of the rod-shaped nuclei is proposed.

Original language	English
Article number	107615
Journal	International Journal of Refractory Metals and Hard Materials
Volume	136
DOIs	https://doi.org/10.1016/j.ijrmhm.2025.107615
State	Published - Apr 2026

Keywords

Hydrogen reduction
Molybdenum
Molybdenum oxide
Nucleation
Potassium

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10.1016/j.ijrmhm.2025.107615

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title = "Exploring nucleation mechanisms in the hydrogen reduction of MoO2 to Mo",

abstract = "The nucleation of various MoO2 starting materials was investigated on a laboratory scale during the second reduction step from MoO2 to Mo of the two-step reduction process from MoO3 to Mo. It was found that a certain proportion of γ-Mo4O11 or a higher potassium content in the MoO2 samples as well as the addition of water to the hydrogen gas stream led to a shift from the pseudomorphic transformation towards the CVT process at a low reduction temperature of 900 °C. Not only spherical/polyhedral Mo nuclei but also rod-shaped nuclei were detected for the first time using the γ-Mo4O11 containing MoO2 starting material after a short reduction time and subsequent cooling in Ar gas flow. The influence of an increased potassium content in the γ-Mo4O11 containing MoO2 samples on the nucleation was also investigated. Additionally, a mechanism for the formation of the rod-shaped nuclei is proposed.",

keywords = "Hydrogen reduction, Molybdenum, Molybdenum oxide, Nucleation, Potassium",

author = "S. Rainer and Willinger, \{M. G.\} and E. Willinger and M. O'Sullivan and H. Huppertz",

note = "Publisher Copyright: {\textcopyright} 2025 The Authors",

year = "2026",

month = apr,

doi = "10.1016/j.ijrmhm.2025.107615",

language = "English",

volume = "136",

journal = "International Journal of Refractory Metals and Hard Materials",

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TY - JOUR

T1 - Exploring nucleation mechanisms in the hydrogen reduction of MoO2 to Mo

AU - Rainer, S.

AU - Willinger, M. G.

AU - Willinger, E.

AU - O'Sullivan, M.

AU - Huppertz, H.

PY - 2026/4

Y1 - 2026/4

N2 - The nucleation of various MoO2 starting materials was investigated on a laboratory scale during the second reduction step from MoO2 to Mo of the two-step reduction process from MoO3 to Mo. It was found that a certain proportion of γ-Mo4O11 or a higher potassium content in the MoO2 samples as well as the addition of water to the hydrogen gas stream led to a shift from the pseudomorphic transformation towards the CVT process at a low reduction temperature of 900 °C. Not only spherical/polyhedral Mo nuclei but also rod-shaped nuclei were detected for the first time using the γ-Mo4O11 containing MoO2 starting material after a short reduction time and subsequent cooling in Ar gas flow. The influence of an increased potassium content in the γ-Mo4O11 containing MoO2 samples on the nucleation was also investigated. Additionally, a mechanism for the formation of the rod-shaped nuclei is proposed.

AB - The nucleation of various MoO2 starting materials was investigated on a laboratory scale during the second reduction step from MoO2 to Mo of the two-step reduction process from MoO3 to Mo. It was found that a certain proportion of γ-Mo4O11 or a higher potassium content in the MoO2 samples as well as the addition of water to the hydrogen gas stream led to a shift from the pseudomorphic transformation towards the CVT process at a low reduction temperature of 900 °C. Not only spherical/polyhedral Mo nuclei but also rod-shaped nuclei were detected for the first time using the γ-Mo4O11 containing MoO2 starting material after a short reduction time and subsequent cooling in Ar gas flow. The influence of an increased potassium content in the γ-Mo4O11 containing MoO2 samples on the nucleation was also investigated. Additionally, a mechanism for the formation of the rod-shaped nuclei is proposed.

KW - Hydrogen reduction

KW - Molybdenum

KW - Molybdenum oxide

KW - Nucleation

KW - Potassium

UR - https://www.scopus.com/pages/publications/105025192214

U2 - 10.1016/j.ijrmhm.2025.107615

DO - 10.1016/j.ijrmhm.2025.107615

M3 - Article

AN - SCOPUS:105025192214

SN - 0263-4368

VL - 136

JO - International Journal of Refractory Metals and Hard Materials

JF - International Journal of Refractory Metals and Hard Materials

M1 - 107615

ER -

Exploring nucleation mechanisms in the hydrogen reduction of MoO₂ to Mo

Abstract

Keywords

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