ISGS AEROGELS WORKSHOP (St. Petersburg, Russia) August 25, 2019 Transparent and Mechanically Robust Aergoels based on Hybrid Networks Kazuki Nakanishi Kazuyoshi Kanamori, Guoqing Zu, Taiyo Shimizu Institute of Materials and Systems for Sustainability, Nagoya University, Japan Institute for Integrated Cell - Material Sciences / Department of Chemistry, Graduate School of Science, Kyoto University, Japan Institute of Materials and Systems for Sustainability
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ISGS AEROGELS WORKSHOP (St. Petersburg, Russia) August 25, 2019
Transparent and Mechanically Robust Aergoels based on Hybrid Networks
Institute of Materials and Systems for Sustainability,Nagoya University, Japan
Institute for Integrated Cell-Material Sciences /Department of Chemistry, Graduate School of Science,
Kyoto University, Japan
Institute of Materials and Systems for Sustainability
プレゼンター
プレゼンテーションのノート
30 min Invited
Low density, transparent, low RI
Low thermal conductivity
What is aerogel?
100 nm
Nano-sized fine porous structure
ρbulk ~ 0.10−0.20 g cm−3
T550nm ~ 90 %/10-mm
λ ~ 12−20 mW m−1 K−1
Excellent thermal insulation of aerogels
Ther
mal
con
duct
ivity
, λ/m
Wm
−1K−
1
Hig
her i
nsul
atio
n
100
90
80
70
60
50
40
30
20
10
0
Superinsulation by aerogels has been expected for more than 80 years !
100 nm
Mesoporous structure consists of weakly connected nanoparticles with 10−20 nm
Mechanically “friable” because of the pore structureHigh-pressure supercritical drying (SCD) is requiredDifficulties in handling and shaping of obtained aerogels
Secondary particles
Primary particles~ 1 nm
10−20 nm
Nanostructure and low mechanical property
Before drying
Duringdrying
Afterdrying
Temporal shrinkage
Aerogel-likeXEROGEL
Spring-back
Gels with high・Strength & flexibility・Hydrophobicity
are needed.
Organogel(e.g. n-hexane)
• Condensation between surface silanols may limit the spring-back.
Si-OH HO-Si → Si-O-Si + H2O
Possibility of ambient pressure drying (APD)
• Gels with low mechanical strength will be damaged.
• First transparent PMSQ aerogels!• Properties are similar to silica aerogels, except mechanical property
Kanamori et al., Adv. Mater. 19, 1589 (2007), J. Ceram. Soc. Jpn. 117, 1333 (2009), etc.
Obtained PMSQ aerogels
29Si single pulse MAS NMR
SiCH3
OSiSiOOSi
T3
SiCH3
OSiSiOOH or OCH3
T2
800100012001400Tr
ansm
ittan
ce
Wavenumber/cm–1
Linear, branchedSi-O-Si
Cyclic, cageSi-O-Si
Si−OH
C−HCH3C−Si−O
-90-80-70-60-50-40ppm
FTIR
分子レベルの構造Molecular-level structures
T3:T2 = 87:13Condensation degree = 96 %
プレゼンター
プレゼンテーションのノート
両方とも水エージングなし NMRはCTAB基本、FTIRは1 mM HOAc
Optimized aerogel (CTAB system)
h0 h
F127 systemCTAB system
0 0.2 0.4 0.6 0.8 10
2
4
6
8
10
Stre
ss, σ
/MPa
Strain, ε
Uniaxial Compression Test on PMSQ Aerogel
プレゼンター
プレゼンテーションのノート
Young’s moduli are from the slopes around 0.2-0.3 MPa (10-20 N)
Max. shrinkage: 40 % in linear, 78 % in volume
FF ×9601 s = 16 min1 min = 16 h
Successful ambient pressure drying (Movie)
プレゼンター
プレゼンテーションのノート
45℃乾燥では約1割収縮したまま。150℃にすると100%スプリングバックする
Thickness = 5 mm
400 500 600 700
20
40
60
80
100
Tran
smitt
ance
(%)
Wavelength/nm
PMSQ xerogelPMSQ aerogelSilica aerogel
PMSQ aerogel Xerogel
Bulk density/g cm−3
Transmittance at 550 nm/%
PMSQ xerogel 0.14 84
PMSQ aerogel 0.13 89
A silica aerogel 0.17 77
Comparable properties between aerogel and xerogel
10-2 10-1 100 101 102 103 104 1050
0.005
0.010
0.015
0.020
0.025
0.030
Nitrogen gas pressure/Pa
Ther
mal
con
duct
ivity
/W m
–1K–1
• Thermal conductivity comparable with silica aerogel• A problem remains: Low bending strength
Thermal conductivity of PMSQ xerogel
PMSQ xerogelSilica aerogelNitrogen gas
(Review) Kanamori, J. Mater. Res. 29, 2773 (2014)
Our new PMSQ aerogels and xerogels
PMSQ aerogel
Xerogel Monolith(Ambient Pressure Drying)
First transparent, superinsulating PMSQ aerogel
“Spring-back” behavior
Granules Composite with fibrous material (Blanket)
Kanamori, Nakanishi, et al., Adv. Mater. 19, 1589 (2007)Hayase, Kanamori, Nakanishi, et al. ACS Appl. Mater. Interfaces 6, 9466 (2014), etc.
プレゼンター
プレゼンテーションのノート
As I showed in the movie, the new PMSQ aerogels derived from ambient pressure drying show flexible behavior against compression, and bending flexibility is now improving by starting from different precursors. The PMSQ aerogels can be processed into monolith, granules and composites with fibrous materials called as blanket.
Today’s MenuApplications
http://www.emg-pr.com/en/prfitem.aspx?id=3024Transparent insulating windows
As I showed in the movie, the new PMSQ aerogels derived from ambient pressure drying show flexible behavior against compression, and bending flexibility is now improving by starting from different precursors. The PMSQ aerogels can be processed into monolith, granules and composites with fibrous materials called as blanket.
Bridged polymethylsiloxanes: 2nd generation
1,2-Bis(MethylDiEthoxysilyl)ethane(BMDE-ethy)
Si
CH3
H5C2OH5C2O
Si
CH3
CH2−CH2
OC2H5
OC2H5
Bridged PolyMethylSiloxane(Ethy-BPMS and Ethe-BPMS)
Shimizu, Kanamori, Nakanishi, et al., Langmuir 32, 13427 (2016) and Langmuir 33, 4543 (2017).
1,2-Bis(MethylDiEthoxysilyl)ethene(BMDE-ethe)
Si
CH3
H5C2OH5C2O
Si
CH3
CH=CHOC2H5
OC2H5
=CH=CHCH2−CH2O
Ethe-BPMSEthy-BPMSPMSQ
Experimental for Ethe-BPMS
Polyoxyethylene 2-ethylhexyl ether (EH-208), n ~ 8
Tetramethylammoniumhydroxide (TMAOH)
BMDE-ethe EH-208 5 mM Nitric acid
10 min at r.t.
TMAOH aq.
Gelation & aging at 60 °C or 80 °C
30 s
Solv. exch. with methanol, IPA
CO2 SCD14 MPa, 80 °C, 10 h
BMDE-ethe
This synthetic process was first developed for VTMS system:Shimizu, Kanamori, Nakanishi, et al. Chem. Mater. 28, 6860 (2016).
Almost the same for Ethy-BPMS.
0.10 M 0.30 M 0.60 M 0.90 M 1.2 M 1.5 MCTMAOH = 0.050 M
Tgel = 80 °C
BMDE-ethe EH-208 5 mM NA TMAOH aq.
0.50 mL0.50 mL0.50 mL0.50 mL
Transparency of aerogels is changed depending on CTMAOH.
Zu, Kanamori, Nakanishi et al. ACS Nano 12, 521 (2018)Zu, Kanamori, Nakanishi et al., Chem. Mater. 30, 2759 (2018)
JP Patent 2017-162308
Doubly crosslinked system: 3rd generation
A detailed example in PVPMS
Polyvinyl-polymethylsiloxane(PVPMS) network
APD without any solvent-exchange
Di-tert-butyl peroxide
(1-5 mol%)
120 ºC, 48 h
BzOH or IPA,H2O, Catalyst (TMAOH)
Polyvinyl-methyldimethoxysilane
PVMDMS(n ~ 40-70)
Vinylmethyl-dimethoxysilane
100 ºC, 4 d
200 nm
Transparent to translucent
Homogeneous pores High BET surface area Scalable High hydrophobicity Compressive flexibility Bending flexibility Low-cost processBut lower thermal durability(~ 200 ºC)
Xerogel
80 % uniaxial compression and perfect recovery
Immersed in n-
hexane
APD againNot damaged!
Bending flexibility of a thick film
Unusual properties in PVPMS xerogels
Durability against solvents
Outstanding machinability
Zu, Kanamori, Nakanishi, et al. ACS Nano 2018, 12, 521.
DCエアロゲルの低熱伝導性と物性比較Thermal conductivity and other properties
DCエアロゲルの低熱伝導性と物性比較Aerogels based on decreased siloxane density
µm
Morphology
Particle size: 1.5-3.0 μm
Pore size: 2.0-20.0 μm
a
b
PA1-1
PA1-2
c PA2-1
d PA2-2
Particle size: 200-400 nm
Pore size: 200 nm-6 μm
PA1
PA2
Superhydrophobic
Superhydrophobic
低架橋DCエアロゲルの多孔構造Coarse pore structures of PA1,2 (less D units)
PA1-1
Mechanical properties High compression flexibility
Absorption capacity of PA1and PA2 for various organic solvents and oils
n-hexane/water
Absorption/drying cycle performance of PA1-1 for n-hexane (it is dried via evaporation at 60 ℃)
n-hexane
water
aerogel
低架橋DCエアロゲルの油吸収特性Oil absorption performanc of PA1
Porous structure
200 nm
PA3
SBET=438 m2 g-1
SBET=605 m2 g-1
200 nm
PA4
PA3 PA4
With the molar ratio of VDMMS to VMDMS decreasing to 1:1 and 1:2, the macroscopic phase separation is further suppressed by the network with lower hydrophobicity and higher cross-linking density, leading to a microstructure with smaller particle and pore sizes
Particle size: 35-100 nm
Pore size: 30-180 nm
Particle size: 20-80 nm
Pore size: 20-100 nm
the hydrophobicity of PA3 and PA4 becomes lower. In spite of this, the contact angles of water of PA3 and PA4 are still above 140°
Hydrophobicity
D単位の比較的多い系における微細な多孔構造の形成Fine pore structures of PA3,4 (more D units)
High compression flexibility
PA4
PA3
5.1 MPa4.2 MPa
PA4
bend release
shaping
PA4
High bending flexibility
Excellent machinability
air PA3 PA4
17.6 16.2
~26
Thermal superinsulation performance
微細な多孔構造をもつDCエアロゲルの機械的物性と低熱伝導性Mechanical/thermal properties of PA3,4
A simple hybridizing method
PA2-G
Graphene
PVPDMS/PVPMS network
The graphene nanopaltes with 2–10 nm thickness and 5–15 μm width are well distributed in the highly porous aerogel matrix
It is also superhydrophobic with a contact angle of water of ~157°
Morphology and superhydrophobicity
導電性物質 (グラフェン) の導入Introduction of graphene
PA2-GLEDreleasecompress
High compression flexibility Strain-sensitive conductivity
brightness fluctuates with compression and decompression of the aerogels
A strain sensor of PA2-G adhered to a finger
PA2-G
More contactsamong
graphene
less contactsamong
graphene
PA2-G
Normalized electrical resistance versus compressive strain