62 4 Gas-Phase Synthesis of Nanoparticles
with and without water addition. This product shows small particles within a
narrow size distribution. The zirconia specimen, displayed in the micrograph,
produced without addition of water excel with a grain size around 8 nm with a very
narrow size distribution, whereas the material produced with water additions is
characterized by a broad distribution of particle sizes in the range from 10 to
50 nm. This dramatic difference between these two batches of the same material
clearly proves the validity of this model.
As long as the product is not an electrical conductor, nearly every material can
be produced with an arrangement as depicted in Figure 4.16. A typical example
of a further product, ZrN, is displayed in Figure 4.19. This material was synthesized using ZrCl 4 as precursor and a mixture of N 2 and NH 3 as carrier and reaction
gas [11]. As this figure demonstrates, the nitrides also take advantage of the electrical charges of equal sign, the particles are small (less than 10 nm) and show a
narrow particle-size distribution.
Figure 4.15 shows that there is a second range, where particles, carrying electrical charges of one sign, negative charges. Such a system, powered with a radiofrequency, RF, generator was described by Buss [12] und later by Matsui [13]. The
design of their system is depicted in Figure 4.20.
The system depicted in Figure 4.20 works with a pulsed plasma, burning
between two permeable electrodes. In the axis of the reaction tube, a steady flow
of carrier gas mixed with evaporated precursor flows. As long as the RF is “on”,
the particles are kept in the reaction zone and grow. In the “off” cycle, the particles
are blown out from the reaction zone and collected outside of the reaction zone.
The operating conditions, gas pressure and RF frequency are selected in such a
way that the energy of the electrons is in the range of 3 eV. Electrons in this energy
range tend to attach at the surface of the particles; they are not ionizing; therefore,
the particles carry negative charges. As the particles carry unipolar electrical
Figure 4.19 Zirconium nitride, ZrN particles made of ZrCl 4 as precursor and a mixture of N 2
and NH 3 as carrier and reaction gas, in a microwave plasma. The lattice fringes visible within
some of the particles indicate they are well-crystallized material [11]. (Reproduced by
permission of Elsevier.)
10 nm
10 nm
10 nm
10 nm
with and without water addition. This product shows small particles within a
narrow size distribution. The zirconia specimen, displayed in the micrograph,
produced without addition of water excel with a grain size around 8 nm with a very
narrow size distribution, whereas the material produced with water additions is
characterized by a broad distribution of particle sizes in the range from 10 to
50 nm. This dramatic difference between these two batches of the same material
clearly proves the validity of this model.
As long as the product is not an electrical conductor, nearly every material can
be produced with an arrangement as depicted in Figure 4.16. A typical example
of a further product, ZrN, is displayed in Figure 4.19. This material was synthesized using ZrCl 4 as precursor and a mixture of N 2 and NH 3 as carrier and reaction
gas [11]. As this figure demonstrates, the nitrides also take advantage of the electrical charges of equal sign, the particles are small (less than 10 nm) and show a
narrow particle-size distribution.
Figure 4.15 shows that there is a second range, where particles, carrying electrical charges of one sign, negative charges. Such a system, powered with a radiofrequency, RF, generator was described by Buss [12] und later by Matsui [13]. The
design of their system is depicted in Figure 4.20.
The system depicted in Figure 4.20 works with a pulsed plasma, burning
between two permeable electrodes. In the axis of the reaction tube, a steady flow
of carrier gas mixed with evaporated precursor flows. As long as the RF is “on”,
the particles are kept in the reaction zone and grow. In the “off” cycle, the particles
are blown out from the reaction zone and collected outside of the reaction zone.
The operating conditions, gas pressure and RF frequency are selected in such a
way that the energy of the electrons is in the range of 3 eV. Electrons in this energy
range tend to attach at the surface of the particles; they are not ionizing; therefore,
the particles carry negative charges. As the particles carry unipolar electrical
Figure 4.19 Zirconium nitride, ZrN particles made of ZrCl 4 as precursor and a mixture of N 2
and NH 3 as carrier and reaction gas, in a microwave plasma. The lattice fringes visible within
some of the particles indicate they are well-crystallized material [11]. (Reproduced by
permission of Elsevier.)
10 nm
10 nm
10 nm
10 nm