Solid Surfaces—Adsorption - Surface and Colloid Chemistry: Principles and Applications - page 129

Characterization of the size, shape, surface area, pore structure, and strength
of particles
Origins and effects of interparticle forces
Packing, failure, flow, and permeability of assemblies of particle
Particle-particle interactions and suspension rheology
Handling and processing operations (e.g., slurry flow, fluidization, pneu-
matic conveying)
Applications of particle technology in production of pharmaceuticals, chemi-
cals, foods, pigments, structural and functional materials, and in environ-
mental and energy-related areas
In a recent report, the effect of synthesis parameters on the precipitation of nanocrys-
talline boehmite from aluminate solutions has been investigated. Nanocrystalline
boehmite (AlOOH) is a useful and effective material for the production of Al 2 O 3 , as
applied in many industrial applications as catalyst or catalyst support, membranes,
and adsorbents. The preparation conditions applied in the production step of nano-
crystalline boehmite strongly affect its morphology, which in turn is reflected in
the final transition alumina. In this work, a precipitation method for the production
of nanocrystalline boehmite is described, studying the effect of pH, temperature,
and aging time on the morphology of the final precipitate. The experiments were
performed at temperatures of 30, 60, and 90°C under moderate pH (from 5 to 7)
conditions and 1 week of aging in the mother liquor. It is noteworthy that, in these
experiments, a unique starting solution is used, and also, the mixing procedure is
unique. The starting solution used is a supersaturated sodium aluminate solution. On
the other hand, the mixing procedure does not follow the normal route of addition
of the neutralization agent (acid) to the aluminate solution. Amorphous boehmite
was prepared at 30°C and pH 7 under prolonged aging conditions. At 60°C, pure
nanocrystalline boehmite with crystallites 3-8 nm was formed at pH 6 and pH 7
after aging in the mother liquor, while at the higher temperature of 90°C, the forma-
tion of pure nanocrystalline boehmite with crystallite size between 3 and 13 nm was
obtained at pH 5, pH 6, and pH 7. Aging and temperature influenced the crystallinity
of the precipitated phases, with prolonged aging and high temperatures inducing
high crystallinity. The pH conditions also had a strong effect on the crystallite size
of the precipitates. Actually, for the same temperature and aging time, the higher the
pH, the larger the crystallites of the precipitates.
Nanocrystalline boehmite can be synthesized by neutralization of AlOOH liquor
under atmospheric conditions (60°C/pH 6), proper aging, and a modification of the
usual neutralization procedure.
Other applications of nanoparticles: At present, there are many research
reports related to the development and processing of inorganic particles ranging
from the nanoscale of less than 10 nm to the microscale. The processing com-
prises various stages of materials fabrication from particles (powders), starting
with the particle synthesis to the point of forming and densification to reach the
final product.
Some of these projects are related to the development and functionalization of nano-
particles for drug and gene delivery, self-assembling of nanoparticles to achieve unique