1. Glenn Research Center at Lewis Field
NANO-CASTED METAL OXIDE AEROGELS
AS DUAL PURPOSE STRUCTURAL COMPONENTS
FOR SPACE EXPLORATION
Eve F. Fabrizio, Ph.D.
NASA Glenn Research Center
Materials Division/Polymer Branch
Brookpark, OH
2003-2004

2. Glenn Research Center at Lewis Field
Motivation For Research
Conductive
Magnetic
Light Emitters
•Electrical Conduits
•Sensors
Ultralightweight Strong
Structural components
Dual Purpose Materials
Metal Oxide Nano-casted
Aerogels

3. Glenn Research Center at Lewis Field
Overview
• Preparation of Metal Oxide Aerogels:
– Overall process and chemical reactions
• Characterization
– IR: Hydroxyl content vs. Carbonate content
– TGA: Thermal Stability, Phase Transitions
– DSC: Phase Transitions
– UV-VIS and Photoluminescence
– Surface Analysis: Area
– Skeletal Density
• Crosslinking Chemistries

4. Glenn Research Center at Lewis Field
Aerogels
nonporous
primary
particles
(<1 nm; dense silica)
mesopores
channels to
micropores
porous
secondary
particles
(density ~ 1/2 silica)
~5-10 nm
• Properties
– Low density (0.05-
0.5 g/cc)
– High porosity
– High surface area
(300-1000 m2/g)
• Uses
– Poor thermal conductors; Good insulators (see
picture)
– Good electrical insulators; SiO2-low dielectric <2
– Good electrical conductors; RuOx, VOx
– Photophysical properties; optics
– Sensors; Optical, Magnetic and Electronic
– Catalysts; High surface area increases
efficiency of reactions
Scanning Electron Microscopy
Silicon Dioxide Aerogel

5. Glenn Research Center at Lewis Field
MOx Aerogels Prepared
Gelled and Tested Attempted; No Gellation
Rare-Earth
Aerogels:
Focus
of this Study

6. Glenn Research Center at Lewis Field
Silicon Dioxide Aerogels: Chemistry
Note: Same chemistry was used to prepare vanadium oxide aerogels.

7. Glenn Research Center at Lewis Field
Silicon Dioxide Aerogels: Structure
O
Si
O
O Si
O
O
O
Si O Si O
OO
Si
O
Si
O
O
O
O
Si
HO
Si
HO
Si
HO
OH
OH
OH
OH
Si
OH
Si
OH
Si
HO
HO
HO
O
O O
O
particle
particle
interparticle neck-zone
N
C
O
N
C
O
H[-O(CH2)4O2C(CH2)4CO-
]n(CH2)3CH2O-H
poly(1,4-butylene adipate), diol end-capped
N
O
O
Structure of Silica:
Polyurethane chemistry:
carbamate
polyurethane
Desmodur N-3200
poly(hexamethylene diisocyanate)

8. Glenn Research Center at Lewis Field
Titanium Oxide Aerogels: Chemistry
Catalyst: HCl

9. Glenn Research Center at Lewis Field
Overall Process for Preparing
Transition Metal Oxide Aerogels
aged gel
Native Silica Aerogels Silica / di-ISO Composites
MeOH /
Water
NH OH
sol
15 min
gel
aging
(48 h)
gel
aged gel
washed with
EtOH
and then
acetone
several
wash cycles
(2 days)
supercritical
drying (CO )
Native silica
aerogel monolith
sol
gel
oven (100 deg. C, 3 days)
supercritical
drying (CO )
di_ISO cross-linked silica
aerogel monolith
gel washed with EtOH
then propylene carbonate
di-ISO in
propylene
cabonate
(4 washings)
4
2 2
TMOS in
MeOH
MeOH /
Water
NH OH4
4 washings with
acetone

10. Glenn Research Center at Lewis Field
Metal Oxide Aerogels: Transition Metals
(in ethanol) (age for 72 hrs)
MClx
.
6H2O MOx
O
Cl
a)
M
O
HH
O
Cl M
O
H
O
Cl
H
+
+
b) O
Cl
H
M
Cl
M
OH
ClHO
+ +

11. Glenn Research Center at Lewis Field
supercritical
drying (CO2)
Overall Process for Preparing
Transition Metal Oxide Aerogels
MClX · 6 H2O
in CH3CH2OH
O
Cl
MOx Gel
Pour into molds and
Aged for 72 h
Gels washed 4 times
with CH3CH2OH
Gels washed
4 times
with CH3CN
Characterization
IR,TGA,DSC,Density
Surface Area

12. Glenn Research Center at Lewis Field
Transition Metal Aerogels: Structure
YOx GdOx ErOx
YbOx FeOx RuOx

13. Glenn Research Center at Lewis Field
Characterization of Rare-Earth Aerogels
MOx
Density
(g/cc)
Skeletal
Density
(g/cc)
Surface
Area
(m2/g)
Average
Pore
Diameter
(A)
labs,max
(nm)
lex,max
(nm)
Magnetic
Susceptibility
PrOx 0.18 2.82 186 84 (< 300) None N/A
NdOx 0.19 3.13 384 109 582 None N/A
SmOx 0.22 2.97 383 93 (<300) None N/A
EuOx 0.20 2.47 379 77 394 616 N/A
GdOx 0.18 3.14 383 72 (<300) None N/A
TbOx 0.20 3.32 365 88 (<300) None N/A
DyOx 0.18 3.02 N/A N/A (<300) None N/A
HoOx 0.21 2.47 N/A N/A 451.5 None N/A
ErOx 0.16 3.28 368 89 520/523 None N/A
TmOx 0.14 3.17 N/A N/A (<300) None N/A
YbOx 0.15 3.25 345 79 291.5 None N/A
SiO2 0.18 1.77 500-1000 14 None None N/A

14. Glenn Research Center at Lewis Field
Absorbance and Photoluminescence of EuOx
0.5
1
1.5
2
2.5
3
3.5
4
4.5
300 1300 2300
wavelength (nm)
absorbance
0
0.05
0.1
0.15
0.2
0.25
0.3
0.35
0.4
0.45
0.5
470 570 670
wavelength (nm)
emissionintensity
lex. = 394 nmabsorbance transistion
used for excitation

15. Glenn Research Center at Lewis Field
Iron Oxide Aerogel
Low Density Magnetic Material
Native
Aerogel
Crosslinked
with di-isocyanate
Crosslinked aerogel
sinter until magnetic

16. Glenn Research Center at Lewis Field
Process to Crosslink Metal Oxide Aerogels
supercritical
drying (CO2)
MOx gel
Pour into molds and
aged for 72 h
(Amine modified gels
were prepared with
aminopropylsilane and
No base catalyst)
Gels extracted from
mold and washed
4 times
with solvent for
cross-linking
Gels placed in
monomer solution
and crosslinked:
D or Initiator
Gels washed
4 times
with solvent for
supercritical drying:
Acetone or
Acetonitrile
Characterization
of final gel; physical,
chemical and spectral

17. Glenn Research Center at Lewis Field
Crosslinking Chemistries: Polyurethane
Si-OH OCN R NCO+ Si-O C
O
N
H
R NCO
Si-O C
O
N
H
R NCO
H2O
Si-O C
O
N
H
R NH2
Si-O C
O
N
H
R NH2 OCN R NCO+
Si-O C
O
N
H
R N
H
C
O
N
H
R NCO
adsorbed
on
silica
+ CO2
carbamate
urea
+ H2O, etc.
silica

18. Glenn Research Center at Lewis Field
Additional Crosslinking Chemistries
NH
N
H
NH
O
O
O O
O
O
O
O
O
O
O
O
O
O
O
NH2
NH2
NH2
O O
O O
Secondary particle
NH
N
H
NH
O
O
O O
O
O
O
O
O
O
O
O
O
O
O
NH2
NH2
NH2
O O
O O
NH
N
H
NH
O
O
O O
O
O
O
O
O
O
O
O
O
O
O
NH2
NH2
NH2
O O
O O
NHNH
N
H
N
H
NHNH
O
O
O O
O
O
O
O
O
O
O
O
O
O
O
NH2NH2
NH2NH2
NH2NH2
O O
O O
Secondary particle
2 Si-(CH2)3-NH + n 
Si-(CH2)3-NH NH-(CH2)3-Si
n-1
AIBN
DH
Polystyrene
linkage
2 Si-(CH2)3-NH + n 
Si-(CH2)3-NH NH-(CH2)3-Si
n-1
AIBN
DH
2 Si-(CH2)3-NH + n 
Si-(CH2)3-NH NH-(CH2)3-Si
n-1
AIBN
DH
Polystyrene
linkage
Epoxies
Polystyrene
Si-(CH2)3-NH2 +  Si-(CH2)3-NH
Aminopropyl groupSecondary
particle
Cl
Styrene
Si-(CH2)3-NH2 +  Si-(CH2)3-NH
Aminopropyl groupSecondary
particle
Cl
Styrene
Cl
StyreneStyrene

19. Glenn Research Center at Lewis Field
Silicon Dioxide Aerogels Crosslinked with Di-isocyanate
(Bayer’s Desmodur N3200)
Native
Aerogel
Native Aerogel
Cross-linked Aerogel

20. Glenn Research Center at Lewis Field
Vanadium Oxide Aerogel Crosslinked with a Di-
Isocyanate (Bayer’s Desmodur N3200)
Native gel
Crosslinked VOx Aerogel

21. Glenn Research Center at Lewis Field
Results and Conclusions
• The following Rare-Earth Gels were prepared:
From all these metals, two were unsuccessful
La- very fragile (unable to remove from mold)
Ce-precipitated prior to gelling
• For most, structure similar to the silica aerogels with some differences:
– more macroporous than microporous
– skeletal density greater and pore diameter higher
• Analysis by IR,TGA and DSC determined the presence of carbonate in the native
rare earth gels.
• Carbonate formed during the supercritical drying: impact on crosslinking to
be determined
• All gels were successfully crosslinked using di-isocyanate and are presently being
characterized for chemical, physical and structural properties.
Tb HoDyPr Nd Sm Eu Gd Er TmYb LuLa Ce

22. Glenn Research Center at Lewis Field
Acknowledgements
• Plousia Vassilaras (LERCIP)
• Anna Palczer (GRC)
• Linda McCorkle and Faysal Ilhan,
Ph. D. (OAI)
• Nicholas Leventis, Ph.D. (GRC)
• Ohio Aerospace Institute (OAI)
• Polymer Branch/NASA Glenn
Research CenterDemonstration of the insulating
properties of aerogels