68 4 Gas-Phase Synthesis of Nanoparticles
Reproducible results of the synthesis process are obtained only under conditions
where the flame is absolutely stable. A critical ingredient for a stable flame is the
correct amount of oxygen. Figure 4.28 displays the appearance of the flame with
different additions of oxygen to the fuel, methane, CH 4 . This example displays the
flame in the case of silica synthesis, where hexamethyl disiloxane, C 6 H 18 OSi 2 was
used as precursor.
Figure 4.27 Typical arrangements for flame synthesis of nanoparticles. (a) In this design, the
vaporized precursor is introduced from the side into the primary flame for reaction. (b) A field
of primary flames surrounds a secondary flame, in which the powder is produced.
Primary
flames
H 2 , O 2 , Ar mixture
Secondary
flame
Precursor,
carrier gas
Primary
flame
Precursor,
carrier gas
H 2 or CH 4 , O 2
Product parƟcles
(a)
(b)
Figure 4.28 Appearance of flames with
methane as fuel and hexamethyl disiloxane,
C 6 H 18 OSi 2 as a precursor for silica. The
amount of oxygen increased from (a) over
(b) to (c). The flame with the lowest oxygen
content was unstable, fluctuated. With
increasing oxygen content, the flame
burns more stably and the temperature
increases [16]. (Reproduced by permission
of Elsevier.)
5 cm
(a)
(b)
(c)
Reproducible results of the synthesis process are obtained only under conditions
where the flame is absolutely stable. A critical ingredient for a stable flame is the
correct amount of oxygen. Figure 4.28 displays the appearance of the flame with
different additions of oxygen to the fuel, methane, CH 4 . This example displays the
flame in the case of silica synthesis, where hexamethyl disiloxane, C 6 H 18 OSi 2 was
used as precursor.
Figure 4.27 Typical arrangements for flame synthesis of nanoparticles. (a) In this design, the
vaporized precursor is introduced from the side into the primary flame for reaction. (b) A field
of primary flames surrounds a secondary flame, in which the powder is produced.
Primary
flames
H 2 , O 2 , Ar mixture
Secondary
flame
Precursor,
carrier gas
Primary
flame
Precursor,
carrier gas
H 2 or CH 4 , O 2
Product parƟcles
(a)
(b)
Figure 4.28 Appearance of flames with
methane as fuel and hexamethyl disiloxane,
C 6 H 18 OSi 2 as a precursor for silica. The
amount of oxygen increased from (a) over
(b) to (c). The flame with the lowest oxygen
content was unstable, fluctuated. With
increasing oxygen content, the flame
burns more stably and the temperature
increases [16]. (Reproduced by permission
of Elsevier.)
5 cm
(a)
(b)
(c)