RT info:eu-repo/semantics/article
T1 Atmosphere-controlled thermal processing enables tunable optical properties via iron-oxide phase engineering in natural silicate materials
A1 Urbaneja Miguel, Álvaro
A1 Torija López, Alba
A1 Carrancho Alonso, Ángel
A1 Iriarte Avilés, Eneko
A1 González Moreno, Sara
A1 González Martín, José Manuel
A1 Trigo López, Miriam
A1 Vallejos Calzada, Saúl
K1 Iron-oxide phase equilibria
K1 Redox-controlled thermal processing
K1 Process–structure–property relationship
K1 Magnetite–hematite transformation
K1 Atmosphere-controlled heat treatment
K1 Functional optical materials
K1 Ciencia de materiales
K1 Materials science
K1 Mineralogía
K1 Mineralogy
AB Controlled-atmosphere thermal processing was investigated as a method to engineer iron-oxide phase assemblages in iron-bearing silicate materials. Natural sandstone was heated between 200 and 1000 °C under air, N2 and CO2 atmospheres to evaluate how oxygen partial pressure governs redox transformations and the resulting macroscopic optical behaviour.The treatments produced a wide and reproducible range of optical responses from a single starting material. Colour evolution, quantified in the CIELAB space, correlates with bulk mineral transformations. Oxidizing conditions stabilize hematite-dominated assemblages and generate red hues, whereas reduced-oxygen atmospheres promote magnetite formation and progressive darkening. Rock-magnetic measurements identify atmosphere-dependent phase assemblages, including a high-coercivity iron oxide under strongly oxidizing conditions. The magnetic response mirrors the optical evolution, indicating that colour development originates from internal phase transformations.Compressive strength remained within the same order of magnitude as the untreated material across the studied conditions, indicating no catastrophic mechanical degradation.These results show that oxygen availability acts as a key processing variable controlling iron-oxide stability and optical response. The study establishes a process-based approach for tuning optical properties in mineral materials through atmosphere-controlled thermal processing without chemical additives. Unlike previous studies focused on temperature-driven effects or isolated observations, this work demonstrates a reproducible process-based approach to tune optical properties in natural silicate materials through controlled atmosphere engineering.
PB Elsevier
SN 2238-7854
YR 2026
FD 2026-05-29
LK https://hdl.handle.net/10259/11978
UL https://hdl.handle.net/10259/11978
LA eng
NO We gratefully acknowledge the financial support provided by all funders. Authors S. Vallejos and Á. Carrancho received Grant PID2023-147301OB-I00 and Grant PID2024-159094NB-I00, respectively, funded by MICIU/AEI/10.13039/501100011033 and FEDER. The financial support provided by Fondo Europeo de Desarrollo Regional-European Regional Development Fund (FEDER, ERDF) and Regional Government of Castilla y León -Consejería de Educación, Junta de Castilla y León- (BU025P23 and BU037P23) is gratefully acknowledged. This work was supported by the Regional Government of Castilla y León (Junta de Castilla y León) and by the Ministry of Science and Innovation MICIN and the European Union NextGenerationEU PRTR. Author Saul Vallejos received grant BG22/00086 funded by Spanish Ministerio de Universidades.
DS Repositorio Institucional de la Universidad de Burgos
RD 28-ago-2026