4 research outputs found
Nanoengineering Super Heat-Resistant, Strong Alumina Aerogels
Because
of ultralow thermal conductivity, excellent catalytic activity,
and better heat resistance than silica aerogel, alumina-based aerogel
has drawn great interest as thermal insulators and catalysts. However,
it is too fragile and sinters above 1000 °C (it shrinks drastically,
>50%, and leaves the surface area as low as 10–70 m<sup>2</sup>/g at 1300 °C), which badly limits its high-temperature
applications.
Herein, super heat-resistant, strong alumina aerogels are prepared
via a novel acetone-aniline in situ water formation (ISWF) method
combined with novel modification techniques: supercritical fluid modification
(SCFM) and hexamethyldisilazane gas phase modification. The heat resistance
of alumina aerogel is enhanced up to 1300 °C via this method.
The shrinkage of the optimized alumina aerogel is reduced to as low
as 1 and 5% and the corresponding surface area reaches up to 152–261
and 125–136 m<sup>2</sup>/g after being heated to 1200 and
1300 °C for 2 h, respectively. The strength is significantly
increased by more than 120% through SCFM. It also exhibits excellent
thermal insulation properties at temperatures up to 1300 °C.
This may significantly contribute to their practical ultrahigh-temperature
applications in thermal insulations, catalysts, catalyst supports,
etc
Super Black Material from Low-Density Carbon Aerogels with Subwavelength Structures
Many scientists have
devoted themselves to the study of the interaction
between subwavelength structures and electromagnetic waves. These
structures are commonly composed of regular arrays of subwavelength
protuberances, which can be artificially designed. However, extending
from 2D periodic patterns to 3D disordered subwavelength structures
has not been studied yet. In this study, we studied the total diffuse
reflectivity of carbon aerogels with various 3D networks of randomly
oriented particle-like nanostructures by using normally incident visible
light (430–675 nm). We observed that the different 3D network
nanostructures of carbon aerogels, especially for the structures with
the minimum size, reduced the reflectivity effectively. It was found
that the key mechanism for the subwavelength-structure-induced ultralow
reflectivity property is due to the decrease of the amplitude of electron
vibration forced by the electromagnetic wave, which provides a simple
method for designing perfect black materials
Reaction-Induced Microsyneresis in Oxide-Based Gels: The Assembly of Hierarchical Microsphere Networks
Rigid
and stable networks composed of litchi-shaped microspheres were formed
via hierarchical self-assembly (SA) of oxide-based nanoparticles (NPs).
The phenomenon of the apparent changes from NPs networks to microspheres
networks after the gelation was similar to normal microsyneresis.
However, in-situ composition evolution results indicate that the SA
is driven by interparticle dehydration, but not affinity difference
between the network for itself and for the solvent. In-situ small-angle
X-ray scattering (SAXS), UV–vis–NIR, and electric conductivity
were used to study the microsyneresis process. To further demonstrate
the mechanism, extra complexant was added and successfully restrained
the NPs–microsphere transition by inactivating the surface
hydroxyl of the NPs. Considering the structural similarity, this work
may provide a new approach to control the assemblies of diverse oxide-based
NPs
A Facile and Versatile Post-Treatment Method to Efficiently Functionalize 3D-Printed Carbon Aerogels via Introducing Tailored Metal Elements
The rigorous viscoelastic rheology limits the ink formulation
for
3D-printed carbon aerogels (CAs), making their functional customization
challenging. Herein, we functionalize 3D-printed CAs via a unique
combination of liquid phase deposition and thermal treatment. The
electrodes’ improved areal capacitance after functionalization
is 3949 mF cm–2, exceeding that of the pure 3D-printed
CA electrode by 33.4%, which is superior by comparison with the carbonaceous
electrodes reported previously. These impressive results highlight
the effectiveness of this strategy for further functionalization of
3D-printed CAs. Moreover, numerous other potential applications, including
catalysis, electromagnetic shielding, and solar steam generation,
may be inspired by these findings