Research Work
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Current work and research interest

• TEM study on magnetic thin films and nanoparticles.
• Computer programs for electron diffraction and crystallography.
• HREM and electron diffraction study of crystal structures.

Honors

• Best poster prize for physics/material sciences(1998), Scandem98 conference, Espoo/Helsinki, Finland.
• Research fellowship (1994-1995), Alexander von Humboldt (AvH) Foundation.
• Youth scientist award (1993), Chinese Academy of Sciences.

Selected Publication

5. PCED2.0—A computer program for the simulation of polycrystalline electron diffraction pattern
X.Z. LI
Ultramicroscopy, 110, 297-304(2010).
4. HREM Study and structure modeling of the eta-prim phase, the hardening precipitates in commercial Al-Zn-Mg alloys
X.Z. LI, V. Hansen, J. Gjonnes and L.R. Wallenberg
Acta Mater., 47, 2651-2659(1999).
3. Structure of Al-Rh-Cu Decagonal Quasicrystal: I. A unit-cell approach
X. Z. Li, K. Hiraga and K. Yubuta
Physica. B, 240, 330-337(1997).
2. Two-colour Penrose Tiling
X. Z. Li, J. M. Dubois and K. H. Kuo
Phil. Mag. Lett., 69, 93-98 (1994).
1. Structure of Al₃Mn, an Orthorhombic Approximant of the Decagonal Quasicrystal
X. Z. Li, D. Shi and K. H. Kuo
Phil. Mag., B66, 331-340 (1992).

Publication List

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Advanced PolyCrystalline Electron Diffraction Simulation

For polycrystalline or powder TEM specimens, electron diffraction ring patterns are extensively used for phase identification, in which the diffraction pattern of a known phase acts as a fingerprint.

One approach is to use computer programs that implement the formula for electron diffraction intensity to analyze raw or processed polycrystalline electron diffraction patterns. A specially designed computer program is needed to provide a fast and accurate method for accomplishing this task. This is the motivation to develop the first version of PolyCrystalline Electron Diffraction (JECP/PCED, Li 2004).

PCED2.0 is an upgraded version of previous JECP/PCED. New features include (i) Blackman’s theory, an integral two-beam dynamical theory, for intensity calculation, (ii) Match model for out-of-plane and in-plane texture, (iii) pseudo-Voigt function for peak profile of diffraction ring and (iv) improvement on diffraction pattern indexing and matching to experimental pattern.

Phase confirmation (click to enlarge)	PECD simulation of two phase system (click to enlarge)

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HREM Study of Intermetallic Structure

High-resolution electron microscopic (HREM) study on the structure of the epsilo-Al₃Co phase is briefly shown here. The epsilo-Al₃Co phase (or Tao² Al₁₃Co₄ in early reports) is a monoclinic phase with lattice parameters, a = 3.9863 nm, b = 0.8139 nm, c = 3.2208 nm, ß=107.96. The crystalline phase is structurally related to the Al-Co decagonal quasicrystal. A structural model of the crystalline phase has been sucessfully worked out, the calculated images based on the model agree with quite well the observed ones
(X.Z.Li and K. Hiraga, J. Alloys and Compounds, 269(1998) L13-L16).

The [010] HREM images of the epsilo-Al₃Co phase

Observed images		Calculated images
defocus -48 nm	defocus -20 nm	defocus -48 nm	defocus -20 nm

(Click the images, see details)

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Cross sectional TEM images of FePt magnetic thin fim

Cross-sectional TEM study of the FePt/C thin film is briefly shown here. L1₀ nanocomposite FePt-based thin films attract attention for extremely high-density perpendicular recording media due to their high magnetic anisotropy. A L1₀ nanocomposite FePt:C perpendicular thin film with a soft underlayer (SUL) was designed and prepared using a nonepitaxial growth method. The cross-sectional TEM image verifies that this medium consists of a nanocomposite FePt:C layer with FePt nanoparticles embedded in a C matrix and 150 nm soft FeCoNi underlayer.
(M.L. Yan, X.Z.Li, L. Gao, S.H. Liou, and D.J. Sellmyer, Applied Physics Letters, 83(2003) 3332-3334).

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Links

work now at

Center for Materials Research and Analysis ,University of Nebraska-Lincoln.

studied and worked before at

Department of Materials Science and Engineering, Northwestern University.

Center for Materials Science,University of Oslo, Norway.

Institute for Materials Research, Tohoku University, Japan.

Institut fur Kristallographie, Universtitat Munchen, Germany.

Laboratoire de Science et Genie des Materiaux Metalliques(LSG2M), Ecole des Mines de Nancy, France.

Beijing Laboratory of Electron Microscopy(BLEM), CAS, P.R. China.

Beijing University of Iron and Steel Technology (BUIST), P.R. China
(renamed as) University of Science and Technology Beijing (USTB), P.R. China
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