Welcome to Materials Characterization projects perform at FYSIKK

1
Welcome to Materials Characterization projects
perform at FYSIKK IMT, NTNU
Nano-scale Materials Characterizations
2
What has been done
for understanding Pb se- gregation on Al
surface In 50ppm Pb-Al alloy
Al oxide
Al matrix
10 nm
Combining microstructure and EDS composition
analysis both from the cross-section and stripped
surface TEM samples, Pb segregation was
identified to build up at the metal-oxide
interface significantly.
3
Carbon Nanotube or Filament?
Filament
Catalyst particle
Carbon deposit specimen was prepared by exposing
a catalyst (Ni on the silica-alumina support) to
flowing reaction gas at 500C and ambient
pressure. High-Resolution Transmission Electron
Microscopy (HRTEM) investigations were performed
to characterize the grown product morphology for
comparing with the suggested models.
Shell
Carbon wall lattice distance as 0.34 nm
Nanotube
4
Characterization of Chemical Coated LaCoO3 Phase
on YSZ Substrate
LaCoO3 film was coated on YSZ substrate
(Yitrium-ZrO2 single crystal), then annealed at
1000?C for 3h. TEM cross-section specimens were
prepared by the following procedures cutting,
gluing, polishing, dimpling, and ion milling.
SAED pattern of 110 YSZ (FCC-Cubic structure, a
0.516 nm) reveals the possible growth
orientation relationship between the coated
LaCoO3 and YSZ substrate. TEM results reveal
that under the present chemical coating
condition, no continuous LaCoO3 membrane was
formed, only individual grown droplets were
formed on YSZ substrate.
5
Orientation Characterization of Epitaxial Thin
Film
The epitaxial growth model can be designed
according to HRTEM and SAED results, and the
misfit parameter can be calculated as 3.47
between the epitaxial grown LaFeO3 thin film and
LaAlO3 substrate.
Interface dislocations
6
Microstructure Characterization of AlN Fiber
Amorphous covered surface
Configuration Fiber Tip
Aluminum nitride whisker was prepared by
nitridation of aluminium foil at 1500 ?C under
250 mbar N2 gas pressure for 5 hrs.
Both of SAED pattern (streak lines) and HRTEM
provide the microstructure information of the
whisker-like growth relationship, with AlN (001)
perpendicular to the growth direction.
7
Welcome to Microstructure Characterizations The
projects are carried out by Yingda Yu, Dr.
Nano-scale Materials Characterizations
8
Why the thermal conductivity is so different in
two similar AlN materials
Sample Wt Y2O3 Sintering cond. Thermal Con. (W/mK) Lattice oxygen (wt ) Total oxygen (wt ) Grain size (µm)
A 0.8 BN crucible 91 0.56 1.32 3.4
B 3.9 C crucible 154 0.52 1.63 2.9
A high thermal conductivity is essential for
using AlN materials as electronic
substrates. TEM characterizations confirm that
the presence of secondary phases (as marked by
arrows) along grain boundaries and at grain
junctions has a major influence on the thermal
conductivity. No substantial differences were
seen between grain boundaries (GBs) in the two
samples Microstructural changes were found to
disrupt the connectivity of the AlN grains,
resulting in a decrease in the thermal
conductivity of the materials.
9
TEM Characterization of Pressureless Sintered
AlN(CaO) Ceramics
To search new and improved materials to apply in
Hall-Héroult aluminium electrolysis cells as
alternative side linings, which demands more
cheap AlN materials. In the present
investigation, the low cost additive (mayenite
12CaO-7Al2O3) and lower sinter temperature are
explored.
TEM and EDX composition results confirm that
secondary phase equilibrium is existed in the
CaO-Al2O3 secondary phase system during
sintering, which consist with the crystallized CA
phase (CaAl2O4) and high Ca-containing amorphous
C12A7 phase. It is agreement with the result as
expected from CaO-Al2O3 phase diagram
10
TEM Characterization of AlN-TiN Composite
Ceramics
20volTiN/AlN composite
10volTiN/AlN
4 mm
Nano-pores (arro-wed) appeared as increasing TiN
to 20vol
HRTEM reveals the amorphous GBs between AlN and
TiN, and local residual strain contrasts cause by
the thermal expansion mismatch between AlN and
TiN (arrowed below).
Eutectic Y-Al-O reaction lowing the sintering
temperature.
For understanding the relation-ships between
microstructures and sintering conditions to lead
to improving AlN Composite mechanical properties.
The smaller (lt1µm) TIN parti-cles are located in
intragran- ualar positions while large TIN
particles are in intergranualar positions of AlN
matrix.
11
AlN-SiC Solid Solution and AlN-SiC Composite
Ceramics
For improving AlN flexural strength and fracture
toughness, the in-situ formed SiC reinforced AlN
materials are investigated.
Elongated SiC grains associated with SiC polytype
are formed along AlN matrix GBs during sintering.
EELS chemical mapping (from above white square
area) is performed by using three-window
technique, to understand the element distribution
around yttrium-oxide secondary phase region.
SiC Polytype is formed by different stacking
sequences, while AlN Polytype is modified by
different AlO6 octahedral layers.
Moiré fringe
AlN-SiC Solid Solution formed as SiC content
below 10vol. As SiC contents increasing from 10
to 30vol, the average AlN grain size decreased
from 6-8 down to 3-5 µm.
HRTEM and Moiré fringe techniques can be used to
investigate SiC polytype details and SiC
re-nucleation in SiC/AlN composite.
12
Fine phase identification of the elongated AlN
polytype ceramic
AlN polytype grains with the elongated growth for
improving AlN fracture toughness, with
pressureless sintering at 1950C for 4 h.
Here, HRTEM shows the partial AlN polytype
phases 24H, 33R and 39R. Several new phases were
identified by HRTEM
Inversion Domain Boundaries (IDBs) are found as
polytype nucleation nuclear sites.
Detailed polytype phase development during
sintering can be fully identified by HRTEM