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  • Eindhoven University of Technology

    MASTER

    Low-Energy Ion Scattering and spinal surfaces in catalysis

    Reijne, S.

    Award date: 1994

    Link to publication

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  • t(Î) Eindhoven University of Technology

    Faculty of Physics

    Low-Energy Ion Scattering and

    Spinel Surfaces in Catalysis

    S. REUNE FEBRUARY 1994

    Solid State Physics Division

    Physics of Surfaces and Interfaces

    Master Thesis

    Mentors:

    ee ir. J.-P. Jacobs - prof. dr. H.H. Brongersma Schuit katalyse instituut

  • Abstract

    Low-Energy Ion Scattering and Spinel Surfaces in Catalysis

    Abstract

    Low-Energy Ion Scattering is used todetermine the composition of the uppermost atomie

    layer of solid surfaces. Besides the top layer sensitivity easy quantification by calibration

    makes this technique very well suited for application in catalytic research.

    The influence of the chemical environment and surface roughness on the LEIS intensity

    from aluminum and nickel is investigated in alloys and oxides. It was found that in the

    alloys and oxides the signal was independent of the matrix which will allow quantification by calibration. In NiAl{ 110}, however, strong evidence of a matrix-induced decrease of

    the neutralization for the aluminum was observed. The obtained knowledge is used in the investigation of catalytically active spinels.

    Different ferrites were prepared; F~04, ZnF~04 and MgFe20 4, also a- and y-F~03 were included. Catalytic activity, LEIS and XRD show that the octahedral sites are

    preferentially exposed on these spinel surfaces.

    Furthermore, the influence of the preparation metbod and addition of Sn and Ca on the

    surface structure of zinc aluminates, a support material in catalysis, were studied. Ca was

    deposited on the spinel surface, while Sn induced a restructuring of the surface. Although large differences in the structure of the support material were found, the influence on the activity in isobutane dehydrogenation of the Pt supported zinc aluminates was small.

    1

  • Preface

    Preface

    One can only see what one observes, and one observes only things which

    are a/ready in the mind.

    Alphonse Bertillon

    I can only hope this quote is not always valid, but I would like to use this preface to

    thank all people of the surface and interface group at the faculty of physics at the

    Eindhoven University of Technology for the pleasant time during the last year of my

    study. Special thanks to Jean-Paul Jacobs, my coach, for his enthusiastic aid and

    cooperation during the project. I should not forget Hidde Brongersma, not only for the last

    year, but also for giving me the opportunity to do a project in Japan in April 1992. I would also like to thank Hans Dalderop and Gerard Wijers for their technica! assistance during this period. Furthermore thanks to everybody who had any attribution to this work. Finally l'd like to dedicate this work to my parents, for their support during my study.

    Eindhoven, february 1994

    Stef Reijne.

    11

  • Contents

    Abstract ........................................................ i

    Preface . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . ii

    Chapter 1

    Introduetion

    Chapter 2

    3

    Theoretica! aspectsof Low-Energy Ion Scattering . . . . . . . . . . . . . . . . . . . . . . . . . . 5 2.1 Introduetion . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 5 2.2 Basic principles of LEIS . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 5

    2.3 Quantification . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 7

    2.3.1 The differential cross section . . . . . . . . . . . . . . . . . . . . . . . . . 8

    2.3.2 The ion fraction . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 8 2.4 References . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 10

    Chapter 3

    Experimental . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 11 3.1 Introduetion . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 11 3.2 The NODUS . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 11

    3.2.1 The UHV system . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 13 3.2.2 The ion souree . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 13 3.2.3 The cylindrical mirror analyser . . . . . . . . . . . . . . . . . . . . . . . . 13 3.2.4 Detection of the ions . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 15 3.2.5 Charging of samples . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 15

    3.3 Other characterization techniques . . . . . . . . . . . . . . . . . . . . . . . . . . . 15 3.3.1 BET surface area . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 15

    3.3.2 Catalytic Activity . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 16

    3.3.3 X-ray diffraction . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 17 3.4 Experimental procedure . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 17

    3.5 References . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 17

    Chapter 4 Quantification of the composition of alloy and oxide surfaces using Low-Energy Ion

    Scattering . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 19

    4.1 Introduetion . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 19

    4.2 Experimental . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 21 4.3 Results and discussion ................................... 21

    4.3.1 Alloys ......................................... 22

    4.3.2 Oxides . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 25

    1

  • 4.3.3 Surface roughness . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 26

    4.3.4 Surface composition of powders . . . . . . . . . . . . . . . . . . . . . . . 28

    4.4 Conclusions .......................................... 28

    4.5 References . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 29

    Chapter 5 The surface structure of catalytically active spinels, Perrites . . . . . . . . . . . . . . . . . . . 31

    5.1 Introduetion . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 31

    5.2 Experimental . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 33

    5.2.1 Catalyst preparation . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 33

    5.2.2 Characterization of the catalysts . . . . . . . . . . . . . . . . . . . . . . . 34

    5.3 Results . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 35

    5.4 Discussion and conclusions . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 38

    5.5 References . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 39

    Chapter 6 The influence of the preparation metbod on the surface structure of ZnA120 4 ••••••• 41

    6.1 Introduetion . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 41

    6.2 Experimental . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 43

    6.2.1 Catalyst preparation . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 43

    6.2.2 Characterization . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 43

    6.3 Results and discussion ................................... 45

    6.3.1 Elemental composition and compounds .................. 45

    6.3.2 Surface area and porosity ............................ 46

    6.3.3 Surface analysis . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 47

    6.3.4 Catalytic test . . . . . . . . . . . . . . . . . . . . . . . . . . . .