TY - JOUR
T1 - The Formation of Porous Membranes by Filtration of Aerosol Nano-particles
AU - Andersen, Sune Klint
AU - Johannessen, Tue
AU - Mosleh, Majid
AU - Wedel, Stig
AU - Tranto, Jane
AU - Livbjerg, Hans
PY - 2002
Y1 - 2002
N2 - Flame-generated aerosol particles of Al2O3 were deposited by gas filtration on two types of porous and ceramic
tubes of α-Al2O3 with mean pore diameters of 450 and 2700 nm, respectively. The particles were aggregates with
average mobility diameters in the range of 30¨¢100 nm and primary particle diameters of 4¨¢8 nm. The particles are
characterized by differential mobility analysis, transmission electron microscopy, and by their specific surface area.
The deposited membranes are characterized by gas permeability measurements, scanning electron microscopy, and
by their pore size distribution from nitrogen capillary condensation. The particles form a distinct, homogeneous
membrane layer with a porosity of ∼90% on top of the substrate surface and only penetrate slightly into the
substrate structure. The mean pore sizes of the deposited membranes determined by nitrogen condensation agree
approximately with those determined by gas permeation and the specific surface area. The mean pore diameter
varies in the range of 30¨¢70 nm. The gas permeability of the deposited membranes is related to the specific surface
area but influenced by the high porosity. The mean pore size and the permeability of the membranes are almost
independent of the substrate structure.
The development of a membrane with uniform properties is preceded by a short initial period in which the
deposited particles, with an equivalent membrane thickness of roughly 2 m, have a significantly lower permeability
than the ultimately developed uniform membrane layer. This effect is particularly significant for the aerosol particles
with the lowest mean size, probably due to particles deposited in the pore mouths of the substrate.
The particles and the deposited membranes are X-ray amorphous but retain their specific surface area on heating
to even high temperatures. When the membranes are heated to 1473K for 10 h, X-ray diffraction shows a mixture of
θ- and α-alumina, accompanied by a partial disintegration of the membrane and a considerable loss of surface area.
AB - Flame-generated aerosol particles of Al2O3 were deposited by gas filtration on two types of porous and ceramic
tubes of α-Al2O3 with mean pore diameters of 450 and 2700 nm, respectively. The particles were aggregates with
average mobility diameters in the range of 30¨¢100 nm and primary particle diameters of 4¨¢8 nm. The particles are
characterized by differential mobility analysis, transmission electron microscopy, and by their specific surface area.
The deposited membranes are characterized by gas permeability measurements, scanning electron microscopy, and
by their pore size distribution from nitrogen capillary condensation. The particles form a distinct, homogeneous
membrane layer with a porosity of ∼90% on top of the substrate surface and only penetrate slightly into the
substrate structure. The mean pore sizes of the deposited membranes determined by nitrogen condensation agree
approximately with those determined by gas permeation and the specific surface area. The mean pore diameter
varies in the range of 30¨¢70 nm. The gas permeability of the deposited membranes is related to the specific surface
area but influenced by the high porosity. The mean pore size and the permeability of the membranes are almost
independent of the substrate structure.
The development of a membrane with uniform properties is preceded by a short initial period in which the
deposited particles, with an equivalent membrane thickness of roughly 2 m, have a significantly lower permeability
than the ultimately developed uniform membrane layer. This effect is particularly significant for the aerosol particles
with the lowest mean size, probably due to particles deposited in the pore mouths of the substrate.
The particles and the deposited membranes are X-ray amorphous but retain their specific surface area on heating
to even high temperatures. When the membranes are heated to 1473K for 10 h, X-ray diffraction shows a mixture of
θ- and α-alumina, accompanied by a partial disintegration of the membrane and a considerable loss of surface area.
M3 - Journal article
SN - 1572-896X
VL - 4
SP - 405
EP - 416
JO - Journal of Nanoparticle Research
JF - Journal of Nanoparticle Research
IS - 5
ER -