Nanoindentation Evaluation of Brittle Films on Metals Natalia

ABSTRACTThe present study addresses two cases of brittle ceramic films on metals. With the assistance of AE as a supplementary technique, yield initiation phenomena have been evaluated for W single crystal surfaces under several nm thick native oxide film. An AE sensor coupled to an indenter tip allowed an increasing sensitivity to localized fracture and plasticity events in the vicinity of an indentation contact. A good correlation between AE signals and indentation induced plasticity and fracture has been accomplished for contacts below 100 μN. Second, mechanical behavior of porous nanocrystalline SiC films on Mo substrates was examined. An analysis was based on the P-δ2 approach. With this method, both loading and unloading parts of indentation curves obtained with sharp pyramidal indenters may be represented as P=Kδ2 where P, and δ denote indentation load and displacement respectively. The parameter K includes a material's hardness/modulus ratio and indenter geometry.

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Nanoindentation of Aluminum Single Crystals: Experimental Study on Influencing Factors

Materials ◽

10.3390/ma12223688 ◽

2019 ◽

Vol 12 (22) ◽

pp. 3688 ◽

Cited By ~ 4

Author(s):

Pavel Filippov ◽

Ursula Koch

Keyword(s):

Single Crystals ◽

Orthotropic Material ◽

Crystal Orientation ◽

Model Systems ◽

Indentation Hardness ◽

Crystal Surfaces ◽

Single Crystal Surfaces ◽

Average Modulus ◽

First Time ◽

Indenter Geometry

Results from nanoindentation of aluminum single crystals deliver valuable information as model systems for understanding technical aluminum alloys. The effect of the crystal orientation and the azimuthal indenter orientation on indentation hardness and modulus was studied by Vickers indentation (max. load 10 mN) on single crystal surfaces with (100), (110), and (111) orientations. The average indentation hardness varied, depending on the crystallographic orientation, by 1.8%. The anisotropy of the elastic modulus (1.1% of the average modulus) is lowered (indentation averaging effect). This is predicted by explicit approximation of the contact problem (conical indenter, orthotropic material). It was found that indentation hardness and modulus vary periodically with the azimuthal indenter orientation on (100)- and (110)-oriented surfaces (relative amplitude of 1.8% for indentation hardness and 2.6% of the modulus). This is attributed to the combined effect of the indenter geometry and crystal symmetry. For the first time, this effect was quantified for aluminum single crystals.

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Surface reactions observed by photoemission electron microscopy (PEEM)

Proceedings, annual meeting, Electron Microscopy Society of America ◽

10.1017/s0424820100121831 ◽

1992 ◽

Vol 50 (1) ◽

pp. 286-287

Author(s):

H.H. Rotermund

Keyword(s):

Electron Microscopy ◽

Electron Microscope ◽

Work Function ◽

Chemical Reactions ◽

Reaction Diffusion ◽

Dynamic Processes ◽

Clean Surface ◽

Crystal Surfaces ◽

Single Crystal Surfaces ◽

Photoemission Electron

Chemical reactions at a surface will in most cases show a measurable influence on the work function of the clean surface. This change of the work function δφ can be used to image the local distributions of the investigated reaction,.if one of the reacting partners is adsorbed at the surface in form of islands of sufficient size (Δ>0.2μm). These can than be visualized via a photoemission electron microscope (PEEM). Changes of φ as low as 2 meV give already a change in the total intensity of a PEEM picture. To achieve reasonable contrast for an image several 10 meV of δφ are needed. Dynamic processes as surface diffusion of CO or O on single crystal surfaces as well as reaction / diffusion fronts have been observed in real time and space.

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Effects of chemisorbed sulphur on the hydrogen adsorption and evolution on metal single crystal surfaces

Journal de Chimie Physique ◽

10.1051/jcp/1991881423 ◽

1991 ◽

Vol 88 ◽

pp. 1423-1452 ◽

Cited By ~ 36

Author(s):

E Protopopoff ◽

P Marcus

Keyword(s):

Single Crystal ◽

Hydrogen Adsorption ◽

Crystal Surfaces ◽

Single Crystal Surfaces ◽

Metal Single Crystal

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Electronic and Vibrational Properties of Single Crystal Surfaces of NiAl

MRS Proceedings ◽

10.1557/proc-83-47 ◽

1986 ◽

Vol 83 ◽

Author(s):

S.-C. Lui ◽

J. M. Mundenar ◽

E. W. Plummer ◽

M. E. Mostoller ◽

R. M. Nicklow ◽

...

Keyword(s):

Photoelectron Spectroscopy ◽

Nearest Neighbor ◽

Surface States ◽

Active Surface ◽

Atomic Displacement ◽

Inelastic Electron ◽

Crystal Surfaces ◽

Single Crystal Surfaces ◽

Nial Alloy ◽

Bulk Surface

ABSTRACTSurface and bulk electronic structure of the ordered NiAl alloy were measured using angle resolved photoelectron spectroscopy. The measured bulk d-bands (Ni like) were observed to be narrower than theoretically calculated d band widths which are 20 to 40% wider (depending upon what is used as a measure of the width). At least two surface states were observed on both the (110) and (111) surfaces. The nature of these surface states and their relationship to the bulk band structure is discussed. Dispersion of bulk phonons was measured by neutron scattering and fitted with a fourth nearest neighbor Born-von Karman model. Dipole active surface phonons on the (110) and (111) surfaces were observed by inelastic electron scattering and the frequencies also calculated assuming a truncated bulk surface. The calculated surface modes present a qualitative picture of the atomic displacement at each surface and also show that the surface phonon energy and intensity depends upon the structure of the surface.

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