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1 Supporting Information Temperature-invariant superelastic, fatigue resistant, and binary-network structured silica nanofibrous aerogels for thermal superinsulation Lvye Dou a , Xiaota Cheng a , Xinxin Zhang a , Yang Si,* a b , Jianyong Yu b and Bin Ding,* a b a State Key Laboratory for Modification of Chemical Fibers and Polymer Materials, College of Textiles, Donghua University, Shanghai 201620, China b Innovation Center for Textile Science and Technology, Donghua University, Shanghai 200051, China *E-mail addresses: [email protected] (Y. Si); [email protected] (B. Ding) Supporting Information contains: Supplementary Methods Supplementary Table S1-S2 Supplementary Fig. S1-S13 Electronic Supplementary Material (ESI) for Journal of Materials Chemistry A. This journal is © The Royal Society of Chemistry 2020
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Page 1: Supporting Information structured silica nanofibrous aerogels for … · 2020-03-27 · 1 Supporting Information Temperature-invariant superelastic, fatigue resistant, and binary-network

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Supporting Information

Temperature-invariant superelastic, fatigue resistant, and binary-network

structured silica nanofibrous aerogels for thermal superinsulation

Lvye Doua, Xiaota Chenga, Xinxin Zhanga, Yang Si,*a b, Jianyong Yub and Bin Ding,*a b

a State Key Laboratory for Modification of Chemical Fibers and Polymer Materials, College of

Textiles, Donghua University, Shanghai 201620, China

b Innovation Center for Textile Science and Technology, Donghua University, Shanghai

200051, China

*E-mail addresses: [email protected] (Y. Si); [email protected] (B. Ding)

Supporting Information contains:

Supplementary Methods

Supplementary Table S1-S2

Supplementary Fig. S1-S13

Electronic Supplementary Material (ESI) for Journal of Materials Chemistry A.This journal is © The Royal Society of Chemistry 2020

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Supplementary Methods

Fabrication of flexible SiO2 nanofibers

The SiO2 nanofibers were prepared by the combination of sol-gel method and electrospinning

reported in our previous work.[1-2] First, SiO2 precursor sol solution was prepared by mixing

TEOS, H2O, EtOH, C2H2O4 with a molar ratio of 1:3.57:0.71:0.016 at room temperature for 8

h. Meanwhile, a 23 wt% PVB/EtOH solution was prepared by stirring dissolving the PVB

powder in EtOH at room temperature for 8 h. Subsequently, SiO2 sol and PVB/EtOH solution

were mixed with the mass ratio of 3:1 and stirred for another 4 h to obtain the electrospinning

precursor solution. Following electrospinning process was performed by utilizing DXES-1

spinning equipment with an applied high voltage of 15 kV, receiving distance of 15 cm, and a

constant feed rate of 1 mL h-1. The as-spun composite PVB/TEOS composite nanofibers were

calcined at 800 °C in a muffle furnace by gradually increasing the temperature at a heating rate

of 5 °C min-1 to obtain SiO2 nanofibers.

Fabrication of SNFAs

SNFAs were prepared by freeze-drying method reported in our previous work.[2] The

procedure for the preparing of SNFA with a density of 5 mg cm-3 is as follows. Firstly, 1 g

flexible SiO2 nanofibers and 0.26 g SiO2 precursor sol were uniformly dispersed in 200 g PEO

solution with the content of 0.01 wt% by using high-pressure homogenizer (AH-BASIC,

Shanghai Yang Yi Biotech Co., Ltd. China.). Then, the obtained fibrous dispersion was

transferred to the pre-prepared molds, and frozen in liquid nitrogen bath, and then freeze-dried

for 24 h to completely removing the ice crystals within the samples to obtain the unbonded

polymer-assisted silica nanofibrous aerogels (PNFAs). Consequently, the PSNAs were calcined

at 700 ℃ in a muffle furnace by gradually increasing the temperature at a heating rate of 5 °C

min-1 to obtain SNFAs.

Fabrication of BSAs with ultralow density of 1 mg cm-3

Based on the fabrication process of SNFAs above, SNFAs with a flyweight density of 0.5

mg cm-3 were fabricated. Subsequently, this SNFA was immersed into the pre-prepared MTMS-

based silica sol with the mass content of MTMS 0.2 g. After the following hydrolysis-

condensation, solvent exchange, APD, and calcination process, BSA with ultralow density of 1

mg cm-3 was obtained. Theoretically, the density of the aerogel obtained by this method should

be 0.6 mg cm-3. However, the volume shrinkage of SNFA during the immersing process

resulting in the increase of density.

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Uncategorized References[1] H. Shan, X. Wang, F. Shi, J. Yan, J. Yu, B. Ding, ACS Appl Mater Interfaces 2017, 9,

18966.[2] L. Dou, X. Zhang, X. Cheng, Z. Ma, X. Wang, Y. Si, J. Yu, B. Ding, Acs Applied

Materials & Interfaces 2019, 11, 29056.

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Table S1. Physical properties of SNFA and BSAs.

SampleMTMS

[g]

ρ

[mg cm-3]

Loading of granular

silica aerogel (%)Porosity [%] SBET

a) [m2 g-1] Vpore [cm3 g-1] Dpore

b)[nm]

SNFA 0 5.05 0 99.77 2.20 0.0017 34.22

BSA1 0.2 5.97 15.39 99.73 67.41 0.0472 4.10

BSA2 0.5 7.69 34.31 99.65 144.08 0.0907 3.41

BSA3 1 16.53 56.00 99.25 200.84 0.2070 5.62

BSA4 2 29.39 73.89 98.66 450.42 0.5963 6.09

a) Specific surface area obtained from the nitrogen adsorption–desorption isotherms using the

Brunauer-Emmett-Teller equation; b) Mean pore diameter obtained from the nitrogen

adsorption–desorption isotherms according to the Barrett-Joyner-Halenda method.

Table S2. The relevant properties of BSAs and other commonly used thermal insulators

Materials Density(mg cm-3)

Thermal conductivity(W m-1 K-1)

Maximumworking temperature

(℃)Compressibility

HNAs 1~30 0.022 - 0.027 1100 Superelastic

PU foams 30 – 200 0.027 – 0.2 200 Elastic

Glass fiber/SiO2 aerogels 50 – 300 0.04 – 0.2 800 Elastic

Nonwovens 50 – 200 0.05 – 0.3 150 Elastic

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Fig. S1 – S13

Fig. S1 SEM images of BSA1 (a), BSA2 (b), BSA3 (c) and BSA4 (d).

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Fig. S2 Micro-orientation and macro-isotropic structure of BSAs.

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Fig. S3 100-cyclic compressive test of BSA1 (a), BSA2 (b), BSA3 (c), and BSA4 (d).

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Fig. S4 (a) Three compressing direction (x, y, and z) on a cubic BSA sample. (b-d) Compressive stress versus strain curves for BSAs under three compressing direction.

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0 10 20 30 40 50 60

0

1

2

3

4

5 10 % min-1

50 % min-1

100 % min-1

200 % min-1

500 % min-1

Stre

ss (k

Pa)

Compressive strain (%)Fig. S5 The compressive σ−ε curves of BSAs under different compressive rates ranging from 10 to 500 mm min−1.

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Fig. S6 (a) The measurement of tensile mechanical property was performed by using a TA-Q850 DMA instrument with a tensile clamp. (b) Tensile σ-ε curve of BSAs.

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0 20 40 60 80

0

2

4

6

8

10

Stre

ss (k

Pa)

Compressive strain (%)

500oC25oC-100oC

Fig. S7 The single-cycle σ-ε curve at -100oC and 500oC are almost completely the same with the curve at 25oC (ε = 80%, both along the axial direction).

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Fig. S8 3D surface graphs of the stress dependence on strain and temperature in the compression (a) and release(b) process of BSAs.

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0

2

4

6

50020025

Mod

ulus

(kPa

)

Temperature (oC)

Young's modulusLoss modulus

-1000.00

0.05

0.10

0.15

0.20Damping ratio

Dam

ping

ratio

(tan

)

Fig. S9 The Young’s modulus, loss modulus, and damping ratio for the first cycle of BSAs (ε = 60%) at different temperature.

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Fig. S10 a SEM of silica nanofibrous membrane. b SEM of a single nanofiber showing the good flexibility. c The tensile stress–strain curve of silica nanofibrous membrane. Inset: Optical paragraph of silica nanofibrous membrane showing superior stretch resistance.

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0 25 50 75 100 125 1500

10

20

30

40

λ (m

W m

-1 K

-1)

Temperature (oC)

Fig. S11 The thermal conductivities of the BSA2 at different temperature.

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10 20 30 40 50 60 70 80 90

1000oC, 2h

1100oC, 2h

1200oC, 2h

(301

)(2

12)

(113

)

(200

)(1

02)

Inte

nsity

(a.u

.)

2θ (o)

1300oC, 2h

(101

)

Fig. S12 XRD patterns of BSA2 after calcined at 1000, 1100, 1200 and 1300oC for 2 h.

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0 10 20 30 40 50 60 700

1

2

3

4

5

6

7

2 4 6 8 10 12 14

0.0

0.2

0.4

0.6

Stre

ss (k

Pa)

Compressive strain (%)

Cycle 1 Cycle 5 Cycle 10 Cycle 100

8.0%

Fig. S13 100-cyclic compressive test of BSA2 after calcined at 1100oC for 2 h.


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