May 16, 2011 — Risø DTU researchers, in collaboration with scientists from China and USA, found a new method for revealing a 3D picture of the structure inside a material.

Most solid materials are composed of millions of small crystals, packed together to form a fully dense solid. The orientations, shapes, sizes and relative arrangement of crystals are important in determining many material properties.

Traditionally, it has only been possible to see the crystal structure of a material by looking at a cut surface, giving just 2D information. In recent years, X-ray methods have been developed that can be used to look inside a material and obtain a 3D map of the crystal structure. However, these methods have a resolution limit of around 100nm.

The new technique allows 3D mapping of the crystal structure inside a material down to nanometer resolution, and can be carried out using a transmission electron microscope (TEM).

Figure. 3D mapping of nanometal aluminium film. SOURCE: Riso DTU.

Samples must be thinner than a few hundred nanometers. This will particularly benefit researchers investigating crystal structures inside nanomaterials, where the average crystal size is less than 100nm. The ability to collect a 3D picture of the crystal structure in these materials is an important step in being able to understand the origins of their special properties.

An example of such a 3D map is given in the figure, showing the arrangement of crystals in a 150nm thick nanometal aluminium film. The crystals have identical lattice structure (arrangement of atoms) but they are orientated in different ways in the 3D sample as illustrated by the labels 1 and 2. The colors represent the orientations of the crystals and each crystal is defined by volumes of the same color. The individual crystals of various sizes (from a few nm to about 100 nm) and shapes (from elongated to spherical) are clearly seen and mapped with a resolution of 1nm.

3D mapping allows users to observe the changes taking place inside a material directly. For example, the mapping may be repeated before and after a heat treatment, revealing how the structure changes during heating.

The results are published in the journal Science: Three-Dimensional Orientation Mapping in the Transmission Electron. H. H. Liu, et al. Science 332, 833 (2011). Access the article here: http://www.sciencemag.org/content/332/6031/833.short

The paper is written by scientists from Risø DTU (Denmark), in collaboration with scientists from Tsinghua University (China), Shenyang National Laboratory for Materials Science, IMR (China) and Johns Hopkins University (USA).

The project is funded by Danish National Research Foundation.

Courtesy of Marianne Vang Ryde, http://www.risoe.dtu.dk/.

Follow Small Times on Twitter.com by clicking www.twitter.com/smalltimes. Or join our Facebook group