89 research outputs found
Fabrication of Boehmite Nanofiber Internally-Reinforced Resorcinol-Formaldehyde Macroporous Monoliths for Heat/Flame Protection
No full textBy
distributing boehmite nanofibers to a resorcinol-formaldehyde
(RF) skeletal phase formed by phase separation in an aqueous sol,
composite macroporous monoliths were produced by performing gelation,
aging, and drying processes at 60 °C. In the nanofiber-reinforced
structure, boehmite nanofiber is arranged in parallel within the RF
skeleton and showed high Young’s modulus against uniaxial compression
for their bulk density. These materials can be expected to be applied
to heat/flame protection materials using their heat insulating properties
and high flame resistance
Marshmallow-like Macroporous Silicone Monoliths as Reflective Standards and High Solar-Reflective Materials
No full textThe growing need to expand outdoor
remote sensing using
drones
and robots and to mitigate the urban heat island effect has led to
an increasing demand for highly reflective materials suitable for
outdoor use. I have successfully developed flexible macroporous silicone
monoliths that exhibit high diffuse reflectance due to Mie scattering
caused by the skeletal structure. The porous silicone materials were
prepared by a two-step acetic acid–triethanolamine catalyzed
surfactant-free sol–gel process using tetra-, tri-, and difunctional
silicon alkoxides as co-precursors. In the optimal sample, the material
exhibited a total reflectance of more than 97.5% in the 400–1100
nm wavelength. This range corresponds to the light detection range
of silicon diodes. The optical property suggests potential applications
for the silicone monoliths as simple optical calibration targets (reflective
standard), providing a viable alternative to conventional materials
such as porous polytetrafluoroethylene or barium sulfate. In addition,
high reflectance of the material surfaces across the solar spectrum
results in a significant reduction of increased surface temperature
when exposed to direct sunlight. With its combination of reflectivity,
water repellency, UV resistance, low thermal conductivity, and mid-infrared
radiation properties, the macroporous silicone monolith offers promising
potential for outdoor thermal management applications
Boehmite Nanofiber-Reinforced Resorcinol-Formaldehyde Macroporous Monoliths for Heat/Flame Protection
No full textBy distributing boehmite nanofibers (BNFs) to a resorcinol-formaldehyde (RF) skeletal phase formed by phase separation in an aqueous sol, composite macroporous monoliths have been produced. The nanofiber reinforced monoliths have a skeleton in which BNF is arranged in parallel within the RF structure, and showed high Young's modulus against uniaxial compression for their bulk density. These materials can be expected to be applied to heat/flame protection materials using heat insulating properties and high flame resistance.<br
Boehmite Nanofiber–Melamine–Formaldehyde Composite Aerogels and Derivatives for Thermal Insulation and Optical Applications
No full textMachinable composite aerogels combining melamine resin
and boehmite
nanofibers were successfully prepared by using a sol–gel reaction
in a mixed solvent of aqueous acetic acid and N,N-dimethylformamide. The composite aerogel exhibits
low thermal conductivity and surface processability, making it a potential
thermal insulating material for electronic substrates. Transparent
γ-alumina aerogels and black alumina–graphite aerogels
with a designed surface topography were also prepared through computer
numerical control (CNC) machining and calcination. These aerogels
with precise surface structures are expected to have applications
in fields such as optical materials
Pseudoboehmite Nanorod–Polymethylsilsesquioxane Monoliths Formed by Colloidal Gelation
No full textThe addition of a trifunctional silicon alkoxide methyltrimethoxysilane (MTMS) to aluminum oxide hydroxide pseudoboehmite nanorod (PBNR) aqueous dispersions resulted in adhesion between the PBNR colloids to form macroporous monoliths. The use of greater amounts of MTMS led to coarsening of the skeleton and strengthening of the skeletal structure, and the monoliths got water resistance. When a dispersion of zirconium oxide nanoparticles and MTMS was used as a starting material, a macroporous monolith was also obtained by the same simple process. The colloidal gelation occurs because the silanol moiety is more likely to react with the colloid surface of ceramic materials than with other silanols derived from MTMS and their oligomer. Due to the development of material chemistry, colloidal dispersions having various shapes and compositions are becoming available as products. Based on this mechanism, it is expected to be feasible to fabricate various porous monoliths with characteristic morphologies and properties depending on the colloid.<br
Boehmite Nanofibers as a Dispersant for Nanotubes in an Aqueous Sol
No full textBy exploiting the dispersibility and rigidity of boehmite nanofibers (BNFs) with a high aspect ratio of 4 nm in diameter and several micrometers in length, multiwall-carbon nanotubes (MWCNTs) were successfully dispersed in aqueous solutions. In these sols, the MWCNTs were dispersed at a ratio of about 5–8% relative to BNFs. Self-standing BNF–nanotube films were also obtained by filtering these dispersions and showing their functionality. These films can be expected to be applied to sensing materials
ゾル-ゲル法によるモノリス型多孔性有機ポリシロキサンに関する研究
No full text京都大学0048新制・課程博士博士(理学)甲第18096号理博第3974号新制||理||1573(附属図書館)30954京都大学大学院理学研究科化学専攻(主査)准教授 中西 和樹, 教授 北川 宏, 教授 竹腰 清乃理学位規則第4条第1項該当Doctor of ScienceKyoto UniversityDFA
Optical tactile sensor using scattering inside sol–gel-derived flexible macroporous monoliths
No full textTactile sensors are an essential technology for robots, and various types have been developed. This paper reports on a new optical tactile sensor based on multiple scattering in a porous material with a viscoelastic phase-separated structure fabricated by a sol–gel method. When a macroporous silicone monolith with a few micrometer diameter skeletons was compressed, the diffuse light intensity near the light source was reduced due to Mie multiple scattering. This light intensity change was opposite to the behavior of conventional polymer foams (cellular structures), which have a large structural scale. A simple tactile sensor using a macroporous monolith and a photo reflector was fabricated based on this finding. The skeleton diameter was an important factor for the sensor. In the case of macroporous silicones, the voltage-strain curve showed an almost hysteresis-free clear response. However, the response of macroporous polymethylmethacrylate monolith with a smaller skeleton diameter was weak due to low Mie scattering intensity. Sensors using sol–gel derived macroporous materials have the potential to be thinner and provide improved surface tactile sensation compared to foam materials
Optical tactile sensor using scattering inside sol-gel-derived flexible macroporous monoliths
No full text
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