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Assembled nano-structures from micron-sized precursors
Stockholm University, Faculty of Science, Department of Materials and Environmental Chemistry (MMK).
Stockholm University, Faculty of Science, Department of Materials and Environmental Chemistry (MMK).
Stockholm University, Faculty of Science, Department of Materials and Environmental Chemistry (MMK).
Stockholm University, Faculty of Science, Department of Materials and Environmental Chemistry (MMK).
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2014 (English)In: RSC Advances, ISSN 2046-2069, E-ISSN 2046-2069, Vol. 4, no 58, 30754-30757 p.Article in journal (Refereed) Published
Abstract [en]

Oriented assembly of small crystals to form larger structures are common in nature and full understanding and control of such process would be beneficial for the forthcoming nano-technologies. Such bottom-up assembly of nano-structures most often requires a precursor of nano-sized crystals. Here we demonstrate a novel laser sintering process that can rupture a submicron-sized zirconia precursor into nano-sized crystals, followed by a rapid oriented assembly of these small crystals. A detailed structure study has been carried out to understand the complex process and a model has been proposed. Such a process sheds light on a new way of fabricating nano-materials using commercialized oxide materials.

Place, publisher, year, edition, pages
2014. Vol. 4, no 58, 30754-30757 p.
National Category
Chemical Sciences
Research subject
Inorganic Chemistry
Identifiers
URN: urn:nbn:se:su:diva-107448DOI: 10.1039/c4ra03191aISI: 000340500300042OAI: oai:DiVA.org:su-107448DiVA: diva2:747160
Note

AuthorCount:5;

Available from: 2014-09-15 Created: 2014-09-15 Last updated: 2017-12-05Bibliographically approved
In thesis
1. Laser sintered materials with Non-equilibrium structures
Open this publication in new window or tab >>Laser sintered materials with Non-equilibrium structures
2014 (English)Doctoral thesis, comprehensive summary (Other academic)
Abstract [en]

This thesis is focused on achieving materials with non-equilibrium structures fabricated by high-energy laser sintering. The chosen precursor materials have rigid and inert structures like high-melting point ceramics or metals. It was necessary to use real-time monitoring of temperature and spectrum profiles for selecting the optimal laser parameters for the laser sintering process. This monitoring was done by an off-axial setup that also controls the surface morphologies during the laser irradiation process. The laser focal spot receives very high temperatures and subsequent extreme cooling rates within a short time period. New non-equilibrium structures will emerge ruled by kinetics, huge temperature gradients or stresses and freeze by quenching in solid state. These material structures were found to form at different length scales from nano- to macro-level, frequently by a hierarchical ordering. This opens a method to engineer materials with both hierarchical and non-equilibrium structures by a single operation in both metal and ceramics by laser sintering. In the Co-Cr-Mo alloy system, structures on three levels of lengths were observed, namely i) nano-level structures dominated by the grain boundary segregation; ii) micron-level structures characterized by the interlocked clusters of columns; and iii) macro-level structures defined by the selected laser scan patterns. The non-equilibrium structures of the Co-Cr-Mo alloy are related to mechanical, corrosion and bio-compatibility properties. In ZrO2 ceramics, the final product had a non-equilibrium nano- and micron-sized structure created by uneven absorption of laser energy and rupture. The structure inside the micron-sized grains is formed through ordered coalescence of nano-crystals. Properties of the laser sintered materials were established and related to the observed structures. The materials properties might be tailored by controlling the structures in different levels and potential applications of the new materials will be given.

Place, publisher, year, edition, pages
Stockholm: Department of Materials and Environmental Chemistry, Stockholm University, 2014. 61 p.
Keyword
Laser sintering, Materials, Non-equilibrium structures, microstructure, hierarchical structure
National Category
Materials Engineering
Research subject
Inorganic Chemistry
Identifiers
urn:nbn:se:su:diva-101096 (URN)978-91-7447-866-2 (ISBN)
Public defence
2014-03-31, Magnélisalen, Kemiska övningslaboratoriet, Svante Arrhenius väg 16 B, Stockholm, 13:00 (English)
Opponent
Supervisors
Note

At the time of the doctoral defense, the following papers were unpublished and had a status as follows: Paper 2: Accepted. Paper 3: Accepted. Paper 4: Submitted. Paper 5: Manuscript.

Available from: 2014-03-09 Created: 2014-02-25 Last updated: 2017-05-11Bibliographically approved

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