96
R. Chen et al.
particles bed is fluidized using either the inter purge gas or the reactive precursor
itself, and then, particles entering the splash zone fluidize as soft agglomerates.
The mechanical bed agitation, using either vibration motors, a magnetically coupled
stirring mechanism, or the pulsation of entering fluidization gases, promotes good
fluidization behavior for nanoparticles. A residual gas analyzer is attached to the
outlet of the FBR, allowing for the real-time detection of both reactants and products
of each ALD half reaction. Van Ommen et al. [150], Rauwel et al. [151], and SoriaHoyo et al. [152] also used the FBR with similar design to prepare ALD films on
the surface of particles. Pt ALD catalysts synthesized in FBR reactor demonstrate
nearly 100% conversion of CO to CO 2 . The photocatalytic activity of TiO 2 particles
is effectively quenched using SiO 2 or alucone polymer films deposited in the FBR
reactor.
Weimer and George et al. [153] have reported the rotary type reactor for ALD
on particles in 2007, which aims to prevent the particles from being agglomerated.
As shown in Fig. 3.11b, a porous cylindrical drum with porous metal walls was
positioned inside a vacuum chamber, which was rotated by a magnetically coupled
rotary feedthrough. By rotating the cylindrical drum to obtain a centrifugal force
of less than one gravitational force, the particles could be in a balance situation
among the gravity force, the inward viscous drag force for gases entering the porous
vessel, and the outward centrifugal force. In addition, an inert N 2 gas pulse helped
to dislodge the particles from the porous walls and provided an efficient method to
purge reactants and products from the particle bed. With the static exposures during
ALD, the rotary reactor provides an effective approach for making large quantities
of nanoparticles. Kedar Manandhar et al. [154] and Jinho Ahn et al. [155] also used
a similar rotary reactor to deposit ALD films on the surface of particles. In order
to inductively couple plasma-enhanced ALD on particles, Longrie et al. [156] have
designed a new rotary reactor by using an open glass tube in a vacuum quartz tube that
is connected with the pump. The deposited films on different particles via thermal and
plasma-enhanced ALD are conformal, uniform, and pinhole free, which is important
in the passivation of catalysts.
To improve the uniformity and efficiency of ALD on nanoparticles, Chen et al.
have designed a rotary reactor coupled with fluidization based on the above design
[157]. As shown in Fig. 3.11c, it consists of five major parts: reaction chamber,
dosing and fluidizing section, pumping section, rotary manipulator components, as
well as a double-layer cartridge for storage of particles. In the deposition procedure,
continuous fluidization of particles enlarges and homogenizes the void fraction in
the particle bed, while rotation enhances the gas–solid interactions to stabilize the
fluidization. The cylindrical particle cartridge uses fluidization to disperse particles,
and it adopts a high-speed rotation to enhance gas–solid interactions for the uniform
and stable fluidization of particle bed. Moreover, enlarged interstitials and intense
gas–solid contact under sufficient fluidizing velocity and proper rotation speed facilitate the precursor delivery throughout the particle bed and consequently provide a fast
coating process. The cartridge can ensure precursors flowing through the particle bed
exclusively to achieve high utilization without static exposure operation. The reactor
R. Chen et al.
particles bed is fluidized using either the inter purge gas or the reactive precursor
itself, and then, particles entering the splash zone fluidize as soft agglomerates.
The mechanical bed agitation, using either vibration motors, a magnetically coupled
stirring mechanism, or the pulsation of entering fluidization gases, promotes good
fluidization behavior for nanoparticles. A residual gas analyzer is attached to the
outlet of the FBR, allowing for the real-time detection of both reactants and products
of each ALD half reaction. Van Ommen et al. [150], Rauwel et al. [151], and SoriaHoyo et al. [152] also used the FBR with similar design to prepare ALD films on
the surface of particles. Pt ALD catalysts synthesized in FBR reactor demonstrate
nearly 100% conversion of CO to CO 2 . The photocatalytic activity of TiO 2 particles
is effectively quenched using SiO 2 or alucone polymer films deposited in the FBR
reactor.
Weimer and George et al. [153] have reported the rotary type reactor for ALD
on particles in 2007, which aims to prevent the particles from being agglomerated.
As shown in Fig. 3.11b, a porous cylindrical drum with porous metal walls was
positioned inside a vacuum chamber, which was rotated by a magnetically coupled
rotary feedthrough. By rotating the cylindrical drum to obtain a centrifugal force
of less than one gravitational force, the particles could be in a balance situation
among the gravity force, the inward viscous drag force for gases entering the porous
vessel, and the outward centrifugal force. In addition, an inert N 2 gas pulse helped
to dislodge the particles from the porous walls and provided an efficient method to
purge reactants and products from the particle bed. With the static exposures during
ALD, the rotary reactor provides an effective approach for making large quantities
of nanoparticles. Kedar Manandhar et al. [154] and Jinho Ahn et al. [155] also used
a similar rotary reactor to deposit ALD films on the surface of particles. In order
to inductively couple plasma-enhanced ALD on particles, Longrie et al. [156] have
designed a new rotary reactor by using an open glass tube in a vacuum quartz tube that
is connected with the pump. The deposited films on different particles via thermal and
plasma-enhanced ALD are conformal, uniform, and pinhole free, which is important
in the passivation of catalysts.
To improve the uniformity and efficiency of ALD on nanoparticles, Chen et al.
have designed a rotary reactor coupled with fluidization based on the above design
[157]. As shown in Fig. 3.11c, it consists of five major parts: reaction chamber,
dosing and fluidizing section, pumping section, rotary manipulator components, as
well as a double-layer cartridge for storage of particles. In the deposition procedure,
continuous fluidization of particles enlarges and homogenizes the void fraction in
the particle bed, while rotation enhances the gas–solid interactions to stabilize the
fluidization. The cylindrical particle cartridge uses fluidization to disperse particles,
and it adopts a high-speed rotation to enhance gas–solid interactions for the uniform
and stable fluidization of particle bed. Moreover, enlarged interstitials and intense
gas–solid contact under sufficient fluidizing velocity and proper rotation speed facilitate the precursor delivery throughout the particle bed and consequently provide a fast
coating process. The cartridge can ensure precursors flowing through the particle bed
exclusively to achieve high utilization without static exposure operation. The reactor