溶凝膠法製做玻璃
溶凝膠法的過程與原理:以SiO2為例
TMOS(Si(OCH3)4)+水+醇
(a)水解(hydrolysis)反應
OR
RO Si OR
+
OR
HO Si OR + ROH
H2O
OR
OR
(b)縮合(condensation)反應
OR
RO Si OH + HO Si
OH
OR
OR
OR
OR
OR
RO Si O Si OR + H2O
OR
OR
(c) 多縮合反應(polycondensation)
OH
HO
OH
Si O Si OH + 6Si(OH)4
HO
HO
OH
HO Si O O
H H
OH
O
HO Si O Si O
OH
Si OH
OH
O
Si O Si OH + 6(H2O)
O
HO
O
O
H
H
HO Si O O Si OH
H
OH
OH
聚合反應
單體
(monomer)
顆粒
(particle)
鏈狀結構
(chain)
三維網狀結構
(3D network)
不同環境下的聚合反應
(1) Far from gel point
10nm
10nm
(2) Near from gel point
(3) Gel point
(acid-catalyzed)
(base-catalyzed)
溶凝膠過程與溫度之關係
溶凝膠的不同製程與結果
xerogel film
dense film
heat
Metal
alkoxide
solution
xerogel
wet gel
evaporation
hydrolysis
condensation
dense ceramics
heat
aerogel
uniform particle
sol
precipitating
furnace
ceramic fiber
溶凝膠法的優缺點
優點：
(1) 均質性與高純度。
(2) 節省能源，減少蒸發的損失與空
氣的汙染、較純的樣品、避開相
變、結晶的過程。
缺點：
(1) 原料昂貴。
(2) 凝膠的收縮量大。
(3) 殘留孔穴、氫氧基、碳。
影響成膠時間的因素
1. 溶液酸鹼值
2. 溫度
3. 矽前驅物與水的莫耳比
4. 矽前驅物的分子量
5. 醇類與水的體積比
6. 其他溶劑與添加物
solvent
Methanol (CH3OH)
Formamide(甲醯胺,HCNOH2)
gelling time (hrs)
8
6
Dimethyl-formamide(二甲基甲醯胺, C3H7CNO) 28
23
Acetonitrile(甲基氰, H3CCN)
41
Dioxane(二氧六環, C H O )
4
8
2
熟化過程(Aging process)
acid-catalyzed
base-catalyzed
particulate silica gels
high solubility
particulate silica gels
low solubility
緻密化(Densification)
Flow Chart of the two methods used to vary the pore
characteristics of the gel silica matrices
Alumina gel
ORMOSILS (Organically Modified Silicates)
Si(OR)4+R2Si(OR)2+yR′Si(OC2H5)3
where R is alkyl(烷基) group( -CH3), R′ is alkylene group(烯
烴基 -(CH2)n), y is organofunction group such as -(CH2)3NH2,
-(CH2)3NHCOONH2, - (CH2)3S(CH2)2CHO.
Basic NMR Interactions in Solids
NMR: Nuclear Magnetic Resonance
The Hamiltonian of the interaction of the nucleus with external
magnetic field B0 and its environment:
H=HZ + HQ + HC + HD
Where HZ is the Zeeman interaction, HQ is the quadrupole interaction,
HC is the chemical shift interaction, and HD is the magnetic dipoledipole interaction.
Zeeman interactio n
 
H Z = -μ • B0
E = -γB0 m, where m = -I, I - 1, , - I + 1, - I
resonance frequency ν 0 = γB0 / 2 π
原子核種
自旋
自然界含量(%)
磁場7T時
的共振頻率(MHz)
1H
1/2
99.9
300.1
6Li
1
3/2
7.6
92
44.1
116.6
11B
3
3/2
19.9
80.1
32.2
96.3
17O
5/2
0.038
40.7
27Al
5/2
100
78.2
29Si
1/2
4.7
59.6
31P
1/2
100
121.4
51V
7/2
99.7
78.9
69Ga
3/2
3/2
60
40
72.0
91.5
7Li
10B
71Ga
FT
FT
Quadruploe interaction- first order
1
1
1
ν m↔m-1 = ν 0 - ν Q [ (3 cos 2 θ - 1) - η sin 2 θ cos 2φ]( m - )
2
2
2
3Qcc
where the quadrupole coupling constant ν Q =
2I(2I - 1)
and η is the asymmetry parameter (0 ≤η ≤1)
First order quadrupole powder pattern for spin I=3/2
Quadrupole Interaction- second order
R
[A (φ) cos 4 θ + B(φ) cos 2 θ + C(φ)]
6ν0
3
2
where R = ν Q
[I(I + 1) - ],
4
27 9
3
A (φ) = - - ηcos2φ - η2cos 2 2φ,
8 4
8
30 1
3
B(φ) = - - η2 + 27cos2φ + η2cos 2 2φ,
8 2
4
3 1
1
3
C(φ) = - + η2 + ηcos2φ - η2cos 2 2φ.
8 3
4
8
ν -1/2 ↔1/2 = ν 0 -
Second order quadrupole powder pattern
for central transition of a spin I=3/2
電腦模擬參數
QCC
sQcc
η
sh
Weight(%)
BO3
2.55MHz
180KHz
0.15
0
60.4
BO4
0.2MHz
0
0.1
0
39.6
3Si+1B
4Si
27Al
MAS spectrum of 9Al2O3-2B2O3
B0=40T
11B
MAS spectrum of borosilicate glass
B0=14.1T
Chemical shift interaction


H CS = γ I • σ • B0

where I is the spin - angular momentum, σ is the chemical shift tens or,

and B0 is the external magnetic field .
Chemical shift powder pattern
ν=ν0 [(1 - σ33 )sin 2 θsin2 φ+ (1 - σ22 )cos 2 θsin2 φ+ (1 - σ11 )cos 2 θ]
=ν0 [1 - σis o - σax (3cos 2 θ- 1) - σanis o s in 2 θcos2φ]

where the angle θ and φ are the polar angles of the field B0 with respect to
the principal axes of the chemical shift tens or, and σ11, σ 22 , σ33 are the principal
values of the chemical shift tens or which are labeled so that σ33 ≤ σ 22 ≤ σ11,
1
1
1
σiso = ( σ11 + σ 22 + σ33 ), σ ax = (2σ11 - σ33 - σ 22 ), σ aniso = (σ 22 - σ11 ).
3
6
2
ν1 = ν 0 (1 - σ11 ),
ν 2 = ν 0 (1 - σ 22 ),
ν 3 = ν 0 (1 - σ33 ).
Magnetic dipole-dipole interaction
 
   
1 μ i • μ j 3(μ i • rij )(μ j • rij )
H D = ∑[ 3 ]
5
2 i ≠j rij
rij
2
(
1
3
cos
θij )
 
1
2∑
≈ γi γ j [
(3Iiz I jz - Ii • I j )]
3
4
r
i ≠j
ij
In practice, it is very difficult to carry out a calculation of the lineshape
due to dipole-dipole interaction. An excellent approximation for many
cases is made by using a normalized Gaussian shape function given by
1
- ( ν - ν0 )2
G ( ν) =
exp[
]
2
Δ 2π
2Δ
where 2Δ is equal to the peak to peak width of the derivative of G( ν ).
7 Tesla
14 Tesla
21.1 Tesla
The 45 Tesla Hybrid superconducting magnet of 11.5 tesla with a resistive magnet of 33.5 tesla
Strength
45 tesla
Type
Hybrid
Bore size
32 mm (~1.25 inches)
Online since
December 1999
Cost
$14.4 million
Weight
31,752 kg (35 tons)
Height
6.7 meters (22 feet)
Operating temperature
-271 ° C (-456 ° F)
Water used per minute
15,142 liters
(4,000 gallons)
Power required
33 MW
Magic Angle Spinning (MAS)
probe
rotor
Second order quadrupole interaction
Chemical shift interaction
The structural groups of alkali silicate glasses determined from 29Si MAS-NMR
(Journal of Non-Crystalline Solids 127 (1991) 53-64)
29SI
29Si
MAS-NMR spectra of sodium silicate glasses.
MAS-NMR spectrum of sodium metasilicate glass.
Experimentally determined Q, distribution in lithium (△),
sodium (□) and potassium (○) silicate glasses as a function
of moll% of alkali oxide. Fitted lines were calculated from
equilibrium constants shown in table.
, Q 4;
, Q3 ;
, Q 2；
, Q1 ,
, Q0.
Conclusion:
The detailed distribution of the structural units Qn in binary silicate glasses
was determined by means of the MAS-NMR technique. The equilibrium of
the following types were found apparently to govern the concentrations
of Qn species,
2Qn
Qn-1 + Qn+1 (n = 3, 2, 1),
of n = 3, 2, 1 for sodium and potassium and n = 3, 2 for lithium silicate
glasses in limited composition ranges. The agreements with the
thermodynamic data were quantitative in the sodium and potassium
silicates but only qualitative in the lithium silicate. The chemical shift for
all Qn, species depends linearly on the composition and the slopes are less
for Qn, with smaller n. The linear relations between the averaged chemical
shift and the theoretical optical basicity strongly suggest the potential use
of the 29Si chemical shift as a scale for the basicity of the system.
Structure of sodium aluminoborate glasses study by NMR
(Solid State Nuclear Magnetic Resonance 27 (2005) 37–49)
27Al
B=18.8T
11B
B=14.1T
17O
B=14.1T
Random mixing model:
In a random mixing model without any
constraints.
4–4 avoidance model:
In this model, connections between
tetrahedral network units, [4]M–[4]N
(avoidance of [4]Al–O–[4]Al, [4]Al–O–[4]B and
[4]B–O–[4]B species) are unfavorable, involving
only trivalent cations (B and Al).
oxygen containing [5,6]Al three-coordinated
Conclusions:
Details of linkages such as [4]Al–O–[4]Al, [3]O(2[5,6]Al,[4]Al), [4]Al–O–[4]B,
[4]Al–O–[3]B, [5,6]Al–O–[3]B, [4]Al–O–[4]B, [4]B–O–[3]B and [3]B–O–[3]B
and B-NBO can be distinguished. The fractions of oxygen species can be
calculated with the known
fraction of B and Al species based on random mixing and mixing
considering 4–4 avoidance (avoidance of [4]Al–O–[4]Al, [4]Al–O–[4]B and
[4]B–O–[4]B species). All
of the glasses in this study show high degrees of bond regularity (higher
fractions of Al–B pairs than random) resulting from the ‘‘maximum 4–4
avoidance’’. However,
the significant amounts of [4]Al–O–[4]B suggests that the [4]Al–O–[4]B is
energetically less unfavorable than [4]Al–O–[4]Al and [4]B–O–[4]B. A
better approach to predicting the oxygen speciation for the glasses
containing significant amounts of [5,6]Al involves grouping two [5,6]Al
species. The result strongly suggests the presence of [3]O(2[5,6]Al, [4]Al).