DAYS
1,2 Sunday, Monday, September 28, 29, 2008
CONTENTS
Brazilian-MRS president Prof. Fernando Lázaro
Freire Jr. with conference chairs Prof. Aldo Craievich, Prof.
Reginaldo Muccillo and Prof. Osvaldo Novais de Oliveira Jr. at the
opening of the conference.
The 7th
Brazilian MRS Meeting (VII Encontro SBPMat) 2008 got off to an
excellent start on Sunday, September 28, in Guarujá, São Paulo,
Brazil. Guarujá is located on the Atlantic coast about 70 km from
the City of São Paulo, and is a popular tourist attraction primarily
for the beaches. The conference venue, the Casa Grande Hotel Resort,
is located on a quiet part of Enseada Beach, one of the well known
beaches there.
OPENING
CEREMONY
The conference started on
Sunday with a special opening ceremony. The president of the
Brazilian-MRS Prof. Fernando Lázaro Freire Jr. first welcomed
everyone to the meeting. He mentioned that this is the seventh in
the series of annual conferences and the conference has increased in
size each year. The first conference had 300 participants while the
present meeting had around 1500 abstracts submitted with an expected
attendance of well over 1000. Next, meeting chairs Prof. Aldo
Craievich and Prof. Osvaldo Novais de Oliveira Jr. in turn welcomed
all participants to Guarujá and São Paulo. This was followed by a
wonderful presentation by the University of São Paulo choral group
led by Marcia Hentschel including seven different pieces. A reception was held after the opening
ceremony.
PLENARY LECTURE
1: ALEXANDRA NAVROTSKY
Energetics
of Nanomaterials
|
The first event of the
conference was a plenary lecture on Monday morning by Prof.
Alexandra Navrotsky (Univ. California, Davis, USA) on the energetics
of nanomaterials. Nanotechnology is of course an important area of
research in materials science today. Navrotsky described
calorimetric studies of oxide nanoparticles which have established
systematic trends in energetics at the nanoscale. Typically,
idealized nanoparticles are considered for investigations. However,
real nanoparticles do not have ideal characteristics, with a
distribution of sizes, irregular varying shapes, defects,
imperfectly controlled surfaces etc. With this in consideration,
Navrotsky described the competition among polymorphism, surface
energies and hydration. This has been shown to lead to a crossover
in phase stability at the nanoscale. She described results for
α-alumina and γ-alumina. She also discussed water adsorption results
on iron oxides. Metastable polymorphs were found to have lower
surface energy. Oxyhydroxides have a lower surface energy than
oxides, and hydrated surfaces have lower surface energy than dry
surfaces. Ultimately, surface energy depends on morphology. She also
described the effects of morphology for ZnO. Nanoneedles were shown
to have the highest surface energy, nanorods intermediate, and
nanoparticles the smallest. Finally, she described thermodynamic
effects in titania nanoparticles again by considering water
adsorption on their surfaces.
PLENARY LECTURE
2: GERO DECHER
Rational
Design of LBL-Based Materials: Toward Soft Matter Devices
|
In the second plenary session,
Gero Decher, from the Institute Charles Sadron and Université Louis
Pasteur, Strasbourg, France, described layer-by-layer (LbL)
farication processes for nanoassembley of soft matter devices. In
his preliminary remarks, Decher said that the trend towards soft
materials is a natural consequence of the ubiquitousness of carbon
and the ease of synthesis, in contrast to inorganics. In addition,
he compared the shortcomings of the “bottom up” and “top down”
approaches in materials science, where there is currently a size gap
for functional devices, to natural processes, which can seemingly
make functional structures at any length scale. Furthermore, Decher
maintained that, while one-step self-organization has been a dream
of scientists for decades, this is not possible for lasagna, French
pastry, or for functional nanostructures; step-by-step fabrication,
such as LbL, is required. Citing several examples where surfaces are
very important – hip-joint replacements, corneal implants,
reflective coatings, and corrosion prevention, to name a few, Decher
said that LbL is the ultimate nanofabrication tool developed so
far.
His research group has recently
added nanobags and micropouches to their nanostructural repertoire
of layers, tubes and spheres. In a typical LbL process, a substrate
is coated with a polyanion, washed, coated with a polycation, and
washed again. This process can then be repeated innumerable times,
making automation easily feasible. Reseachers in Decher’s group
coated substrates by dipping them into solutions but more recently
coating by spraying has proven to be quicker, with uniformly
reproducible results. Citing published literature from other
research groups, Decher said that other types of interactions
between layers, such as covalent or van der Waals, have been
exploited in LbL fabrications. Characterization of the layers was
shown to be easily performed with UV-Vis spectroscopy, for example,
the absorption increases linearly with the number of layers, which,
combined with the number of x-ray reflections as a function of
scattering angle, obtains the coating thickness as a function of the
number of layers.
Decher showed many applications
for devices fabricated using the LbL method; one, close to the
Frenchman’s heart, was wine classification by taste sensors. Other
examples included light-emitting diodes, compartmentalized films,
functionalization of nanoparticles, giant nanomembranes, and films
with inorganic barrier layers. Citing work previously published by
another research group, Decher showed how a texture sensor with
fidelity comparable to the human finger was fabricated with a
modified LbL process. Descher said that the next generation of LbL
materials will include drug-delivery devices, implantable materials,
and living multilayers – artificial tissues that can be embedded
with human cells.
PLENARY LECTURE
3: AGUSTI SIN
The
Consequence of Air Pollution and Possible Materials Science
Solutions
|
Particulate matter pollution is
already a serious issue around the globe. In his plenary talk in the
evening, Agusti Sin (Pirelli Eco Technology, an off-shoot of Pirelli
and Co., Italy) described various materials science solutions to
this problems being pursued in his company. A lot of the work he
presented was done at Pirelli labs. Specifically, he described the
use of ceramics in various applications including environmental
sensors, oxygen sensors, fuel cells, oxygen generation, and diesel
particle filter. He devoted a significant part of his talk
discussing diesel particle filters that will be produced by Pirelli
Eco Technology, with plants in Italy and Romania. The total
particulate matter, TPM, in diesel exhaust includes a solid
fraction, a soluble organic fraction and sulfates. Particulate
matter is a serious health hazard, particularly for the lungs, and
there are strict European limits coming into effect by 2014 as to
the extent of such particulate matter that can be released into the
atmosphere. The Pirelli filter uses silicon carbide, because of its
resistance to heat and temperature variations. It also uses a Pt
catalyst on a supporting alumina layer which is present on a
honeycomb structure. The system uses particulate ignition and
catalytic regeneration. It can be retrofitted into existing diesel
buses and trucks. It can be separately installed in passenger cars.
Real life tests on buses showed reduction in particulate matter
emission of upto 97% fulfilling the requirements for European
emission standards. In fact, the exhaust downstream from the filter
was found to be cleaner than ambient air.
TECHNICAL
TALKS
Symposium L: High Resolution Electron
Microscopy The new paradigm in TEM - On the way to the
ultimate limits of optics
|
Knut Urban (Research Center
Julich, Germany) gave the first talk in symposium L on
aberration-corrected transmission electron microscopy, which is
leading to remarkable resolutions enabling materials researchers to
peer deeply into materials right up to the atomic scale. He started
by describing the basics of electron optics and the problems with
aberration encountered in conventional systems. The original
Scherzer's theory for phase contrast yields a large point spread
function. A new theory for phase contrast was proposed a few years
back that reduces the point spread allowing for very fine contrast.
He showed the example of SrTiO3 wherein Sr, Ti and O
atoms can be separated in the image. He then described the negative
spherical aberration imaging (NCSI) technique and showed the example
of the Σ3 {111} twin boundary in BaTiO3 wherein the
atomic separation distances at the twin boundary can be determined,
which different from those in the untwinned crystal. The vertical
atomic separations at the twin boundary were determined to be 0.267
nm for Ti-Ti and 0.214 for Ba-Ba, which were confirmed to be very
close to other experimental data. Finally, Urban described the
current push towards picometer microscopy, edging towards the limits
of electron optics. He described the data for the 90° tilt boundary
in YBa2Cu3O7 and ferroelectric
domain walls in PZT. He used the latter example to suggest that
atomic scale structure can now be used to drive physical properties
of the material by allowing for the understanding of even minute
changes at the atomic scale.
(HR)TEM as a
tool to characterize nanomaterials
|
High resolution TEM, along with
various associated techniques, is ideal for nanotechnology, said
Marcelo Orlandi (Universidade Estadual Paulista, Brazil). The main
focus of this presentation was the characterization of tin oxide and
tin-doped indium oxide (ITO) nanobelts grown from the vapor
phase.The nanobelts with a rectangular cross-section were obtained
by a reduction carbothermal method. The belts are single-crystalline
and can grow in SnO or SnO2 phase depending on the
synthesis conditions. The SnO2 belts were found to grow
by an indirect vapor-solid process. The SnO nanobelts formed
dendritic structures on the sides likely caused by a self-catalytic
VLS process. The SnO nanobelts, being thermodynamically unstable,
change to the SnO2 phase after a thermal treatment,
resulting in a volume reduction and formation of cracks and
cavities. Orlandi's ultimate motivation in presenting this work was
to demonstrate the versatility of HRTEM in studying
nanomaterials.
Symposium
F: Electrochemistry of Nanostructured and Biological
Macromolecules
On the
interactions between metallic nanoparticles and biomolecules:
Fundamental studies and applications in sensing In a contributed talk, Valtencir Zucolotto
presented results of fundamental studies on the interactions between
nanoparticles and biomolecules but with the ultimate goal of curing
or preventing diseases that are problems to his native Brazil, e.g.,
Leishmanuasis detection, which relies on microscopic examination of
samples and is problematic due to frequent false positives with
Chagas disease. Zucolotto showed that antigenic membrane proteins
from protozoa could be identified and isolated, and then
incorporated into nanostructured films fabricated using a
layer-by-layer technique. The capacitance of these films shows a
signature distinct from films lacking the membrane proteins.
Zucolotto developed similar sensor systems for Pasteurelosis and
hemophilia. In other work, Zucolotto complexed gold nanoparticles
with dendrimers for dopamine and methionine sensing; complexed gold
nanoparticles with enzymes for urea detection; showed that Ag and Au
nanoparticles sometimes allow stem cells to grow faster than the
control; and showed evidence that nanotubes are incorporated into
cell membranes during formation.
MnO2 nanostructured electrode prepared by
electrodeposition over a colloidal crystal template as cathode for
lithium battery
|
In a contributed talk in
Symposium F (Electrochemistry of nanostructured and biological
materials), Tania M. Benedetti, from the University of Sao Paulo,
Brazil, presented her research on MnO2 nanostructured
electrodes. Working towards the goal of supercapacitors, which fill
the void between regular capacitors and batteries, Benedetti noted
that magnesium oxides offer high specific energy at low cost, and
are environmentally advantageous but they display low stability
after successive charge-discharge cycles. Decreasing the solid-state
diffusion path would reduce mechanical stress during
charging/discharging, and, in addition, improve capacitance because
additional intercalation sites would be available for lithium
intercalation. Benedetti and co-researchers fabricated a
nanostructured electrode prepared by depositing polystyrene (PS)
spheres from a colloidal suspension over gold previously deposited
on quartz. MnO2 was then electrodeposited with the PS
nanospheres, acting as a template, subsequently removed with THF.
The electrode structure was characterized with SEM and showed
significantly more surface area than a control, fabricated without
the PS template. Electrochemical measurements were performed with a
typical electrolyte and with an ionic liquid. The results are
encouraging but Benedetti expects improved performance, especially
after following suggestions made by attendee, and Plenary Lecturer,
Gero Decher.
Systematic
study of cathodic pre-treatment influence on surface properties and
electrochemical behavior of boron doped diamond produced at
different doping levels In a contributed talk Matsushima et al. presented work on
boron-doped diamond (BDD) films, which have been shown to be
conductive and have application in energy-storage devices. In order
to develop a method to rigorously control diamond growth patterns,
required to produce electrodes with surface properties suitable to
the application, the researchers performed a systematic study of
deposition, characterization, and electrochemical sensitivity of BDD
using four different doping levels. BDD samples were prepared with
the hot filament chemical vapor deposition (CVD) technique, using
the standard mixture of H2 and CH4. Diamond
quality and morphology were characterized by Raman spectroscopy and
x-ray diffraction, while the film surfaces were analyzed by contact
angle measurements, cyclic voltammetry, and synchrotron X-ray
photoelectron spectroscopy. The researchers found that the doping
level influences the level of sp2 C-C bonding at the film’s grain
boundary as well as the defect level in the diamond
lattice.
Symposium
G: Theoretical and Experimental Advanced in the Development of New
Materials A survey on the joint use of experimental and
theoretical methods and techniques in materials
science
|
Addressing a mostly Brazilian
audience in Spanish, Professor Juan Andres, from Jaume I University,
Spain, used slides in English to survey the computational methods
currently used in materials science. Stating that an atomistic level
of understanding is mandatory to discover new synthetic routes and
to better comprehend solid state properties, Andres said that
electronic structure theory has progressed from a descriptive tool
to an analytic tool and is now routinely used in the interpretation
of experimental results. Furthermore, in addition to the two
established components of science – experiment and theory –
computational simulation has emerged as a third component. With the
observation of phenomena at an atomic scale just beginning to be
realized, Andres envisages the role for computational simulation to
include predictions of chemical stability, free energy, and chemical
reactions, while structure property relationships will continue the
traditional link between theory and experiment. Rather than be
competitive disciplines, experiment, theory, and computation are
complementary tools. Andres demonstrated his viewpoint with several
case studies, including growth mechanisms of pure and mixed metal
oxide nanostructures; structural and electronic properties of metal
oxides; high-symmetry and low-symmetry forms of perovskite-based
materials; transverse inversion polarization in ferroelectrics;
defects in crystal structures; photoluminescence; the formation of
microscopic facets; and the formation of Au zig-zag
nanotubes.
SCENES FROM THE
RECEPTION
ABOUT THE
MEETING SCENE
- The 7th Brazilian MRS
meeting is being covered for the Meeting Scene by Dr. Gopal Rao
(Materials Research Society, Warrendale, Pennsylvania, USA), and
Dr. Steve Trohalaki (Air Force Research Lab, Wright Patterson AFB,
Ohio, USA).
Gopal Rao
Steve
Trohalaki
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