PHYS 570 -Introduction to Synchrotron Radiation

Structure and melting of Bi

nanocrystals embedded in a

B2O3-Na2O glass

Mariana C. SiqueiraMariana C. Siqueira

December/2013

Outline

� Introduction� Experimental Details� Theoretical Background� Results and Discussion

Introduction

� Potential use of nanometer�sized metallic particles as catalystics and heat exchange materials;

� Metallic clusters embedded in glass matrices has singular optical properties.

Experimental Details

� Material: Bi nanocrystals embedded in a B2O3$Na2O glass;

� SAXS and WAXS combined measurements at SAS beamline of LNLS;

� Record using one$dimensional gas x$ray position$sensitive detector;

� X$ray monitor placed before and after the sample;

� X$ray beam with λ=1.61Å;� Different temperatures measurements

from 304K to 503K.

Theoretical Background

� SAXS Intensity:

� WAXS Intensity:

� Scherrer equation for average chord lenght:

� Nanocrystal to Liquid Transition:

−−=

∆=

++=

−= ∫

∞

m

llcc

hklhklhkl

lgcWAXS

nmpSAXS

RLTbTm

M

TIITITI

dRqRFRRDqI

)(31

cos)2(

),()(),(),(

)]([)(3

4)()(

26

0

ρσρσ

θθ

λ

θθθθ

πρρ

Results and Discussion

� SAXS

� Volume fraction of spherical clusters determined by SAXS.

Results and Discussion

� WAXS

Results and Discussion

� Ic of WAXS � Average chord lenght

Results and Discussion� Melting Temperature as

a function of the nanocrystal reciprocal radius.

� Volume fraction of spherical clusters determined by WAXS.

Results and Discussion

� The simultaneous use od SAX and WAXS techniques yield usefull and precise information on the structure and on the crystal$transition of nanocrystals in the glass matrix.

References

� G. Kellermann, A. F. Craievich. Phys. Rev. B, 65:134204 (2002);

� G. Kellermann, A. F. Craievich. Phys. Rev. B, 67:085405 (2003);

� F. Gonella, P. Mazzoldi, Handbook of Nanostructure MAterials and Nanotechnology (Academic, New York, 2000)

THANK YOU ALL!!!