Nanofibers of aluminum oxide

Nafen is produced from melt:
industrial-scale technology

TEM micrographs / SAXS data
small-angle scattering (SAXS);
also indicate high degree of alignment

Nafen nanofibers : summary of properties
* - phase composition can not be accurately quantified because of lack
of structure model for χ-phase

Is it unique?
Reference 1:
AlOOH “aerogel” (FEI)
Reference 2:
Nano Technology Inc. (Korea):
“diameter is approximately 5-10 nm, and the aspect ratio is in
the 50 to 200 range”

Mechanical properties of
individual fiber
CNTs (Wiki):
Young's modulus on the order of 270 - 950 GPa and tensile strength
of 11 - 63 GPa

Phase analysis (XRD)
Typical diffraction patterns for low-temperature phases of alumina
chi is identified by the peak at 2θ=42.8
Diffraction patterns
of two samples of Nafen
the phase is identified as mostly chi, with some gamma
crystallite (CSR) size 50-100 nm
Nafen fibers are polycrystalline alumina in gamma and chi phases

High-temperature phase transformation (XRD)
At 1200–1400 C, transformation to alpha phase occurs

The surface is ‘saw-shaped’ (TEM)

EP-PP copolymers:
“as co-monomer”
Surface treatment type affects
the performance, including level of
TOD stability enhancement
790% / 5.8 MPa
940% / 8.0 MPa
Main application:
reinforcing filler for thermoset-based adhesives
Refefence:
N.M. Bravaya et al.,
J. Appl. Polymer Sci. (2017) –
accepted for publication

Technological challenges & solutions
Ultrasonic dispersion and/or targeted surface treatment (functionalization) allows good (almost to single fiber) level of dispersion

Surface chemistry
1H MAS NMR:
three types of surface protons:
- terminal
- bridge
- hydrogen-bonded
IR spectroscopy / CO absorption:
only weak and medium-strength
Brønsted and Lewis centers are present:
max Q(LC) = 39 kJ/mole - considerably lower
than for “conventional” Al2O3 types

Nafen as support for heterogeneous catalysts:
first trials
1) HDC of halogen-aromatic compounds:
application for waste treatment
(unpublished)
2) Emulsion hydrogenation
of substituted phenols
(unpublished data):
23 compounds tested
Nafen-supported catalyst
showed up to 95% yield and
up to 94% selectivity
2) Low-temp CO-oxidation
95% conversion already
with unmodified commercial catalyst

Nafen as support for heterogeneous catalysts:
potential / advantages
low-T Al2O3 polymorph
relatively high SSA and “highly-defective” surface:
allows easy anchoring of catalytically active components
low acidity: no / minimal side reactions → selectivity
surface chemistry can be tailored:
- three subtypes of Nafen available
- functionalization is possible
ready masterbatches for liquid dispersion type processes
can be produced
“bonus” reinforcement effect (?)