DAY 4
Wednesday, October 1, 2008
CONTENTS
The 7th
Brazilian MRS Meeting (VII Encontro SBPMat) 2008 completed its
fourth and penultimate day. The last three plenary lectures of the
meeting were the major highlight of the day, which also included the
final poster session, the exhibit and various technical sessions.
PLENARY LECTURE
7: GEHAN A. J. AMARATUNGA
Nanocomposites for Photovolatic Energy
Harvesting
Gehan Amaratunga, from
Cambridge University, UK, presented the seventh plenary lecture and
described his group’s ongoing research using nanocomposites for
photovoltaic (PV) energy harvesting. Distinct from PV energy
generation, which is an established technology growing at a rate of
50% per year as an alternate to conventional electricity generation,
PV energy harvesting is envisaged as employing inexpensive
technologies to capture light energy in low-light environments
unsuitable for conventional, silicon-based PV devices. For example,
implementation on flexible substrates, such as fabric and flexible
plastic, through processes such as painting and printing could power
autonomous sensing and communication electronics using ambient,
fluorescent light.
These possibilities have come
about due to the ability to synthesize nanoscale inorganic
semiconductors, such as ZnO, FeO, TiO, Si, GaAs and Ge, and combine
them within a polymer. The PV surface is essentially an ensemble of
nanoscale PV cells acting to yield an average terminal voltage and
current over a defined area. Amaratunga said that energy conversion
and local storage is more important than power conversion efficiency
because the environmental light source has a much lower intensity
than sunlight.
Amaratunga presented a
transparent PV cell fabricated by dispersing single-walled carbon
nanotubes (SWNTs) onto a transpatent substrate and then growing ZnO
nanowires over them using the hydrothermal method. Another PV cell
was fabricated by growing ZnO nanowires on a fabric composed of
electrospun carbon fiber. A black dye was included to enhance light
absorption. Considering the reverse process, Amaratunga fabricated
ZnO-SWNT composite light-emitting diode, which displays a strong
monochromatic emission at 450 nm. Amaratunga speculated that the
source of this emission had to do with defect sites in ZnO nanowires
that might act as cavities for light amplification.
PLENARY LECTURE
8: ENRICO TRAVERSA
Materials
for a Sustainable Development: The Key Role of
Nanostructure
Enrico Traversa (Università di
Roma “Tor Vergata”, Rome, Italy) started his plenary presentation by
discussing the current energy situation in the world. It is clear
from an environmental and sustainability view-point that alternate
energy sources need to be used. Another interesting dynamic is that
the overall population around the world is aging, meaning there are
larger number of older people, who will require adequate health care
in the future. For solutions to these problems, materials will play
a key role with required improvements in performance. The approach
followed by Traversa's research group is to find nanostructured
materials with innovative characteristics. He described three
different applications as examples, gas sensors, fuel cells and
tissue engineering, covering the environment, energy and health
areas respectively.
For gas sensing applictions, he
described reducing the size of semiconducting metal oxides to
increase sensitivity of sensors. For example, the gas responses of
titania-based gas sensors are strongly dependent on particle size.
He also discussed Pt|YSZ|Pt|Nb2O5and
Pt|YSZ|Nb2O5 sensors for on-board diagnostics
in automobiles. These are being used for monitoring the output to
comply with increasingly stricter European standards for emissions.
Next, Traversa discussed SOFCs,
which are very promising for stationary energy production
applications. Currently, the availability of SOFCs is limited by the
high operation temperature (1000°C) of commercial cells, needed due
to the use of yttria-stabilized zirconia (YSZ) as solid electrolyte.
It is necessary to reduce the temperature below 700°C to overcome
this. One of the tricks is to use nanostructured materials for the
electrodes. He described the development of nanostructured materials
for the electrolyte, cathode, anode and protonic conductors. He also
described miniaturizing SOFCs for applications at lower temperatures
using pulsed laser deposition for forming thin films. Finally,
Traversa described some recent work in his group on tissue
engineering of cardiac tissue. This requires mm scale, micron scale
and nanoscale structures all within the same single structure. He
concluded by suggesting that it is possible to be optimistic about
the future and that we will overcome all of these energy and
sustainibility challenges.
PLENARY LECTURE
9: FERNANDO COSME RIZZO ASSUNÇÃO
A
Prospective Study of Advanced Materials
In the ninth and final plenary
talk of the conference, Fernando Rizzo, Director of CGEE (the Center
for Strategic Analysis and Study, roughly translated), Brazil,
outlined and gave examples of prospective studies on advanced
materials. He first gave a brief overview of CGEE, which was
established seven years ago. Its mission is to subsidize the policy
and strategic management in the areas of science, technology, and
innovation. Each project goes through four phases – information,
knowledge, commitment, and strategy – in order to develop a vision
for the future.
The growing importance of
advanced materials in everyday life, as well as substantial advances
in new and existing technologies, has stimulated CGEE to develop a
series of prospective studies aimed at increasing the
competitiveness of the materials science industry and the rational
utilization of natural resources in Brazil. The main goal of these
studies is to provide direction for future research and development
through a collective decision making process with involvement from
academe, government, and industry. The results of these studies have
been incorporated into technological roadmaps for specific
industrial sectors. Recently, a prospective study on advanced
materials has been initiated with a time horizon of 2022.
Prioritizing research and
development topics using criteria including potential return of
investment and the level of technical maturity in Brazil and the
world, seven themes were selected for advanced materials: 1)
Sustainable utilization of natural resources (mineral and
biological) 2) Energies for the future: generation and
storage 3) Environmental remediation 4) Health quality 5)
Dual technologies 6) Tribology 7) Photonic, electronic, and
magnetic materials. Rizzo presented the current status of several
prospective studies, highlighting some of the results obtained so
far.
TECHNICAL
TALKS
Symposium A: Novel Hybrid Organic-Inorganic
Multifunctional Materials Influence of Nanostructure on
Properties of Organic-Inorganic Hybrid Materials of Technological
Interest
|
In an invited talk in Symposium
A, K. Dahmouche, from the Institute of Macromolecules, University
Federale Rio de Janeiro, showed how profoundly the nanostructural
features of different types of organic-inorganic hybrids determine
their properties. The nanostructures of hybrids prepared by the
sol-gel method displaying ionic or electronic conductivity, magnetic
properties, and good optical, mechanical, or adhesion properties,
were investigated with small-angle x-ray scattering (SAXS).
Dahmouche generally concluded that much more than optimizing the
local or individual properties of each phase of the materials,
nanostructural control is the key to improving the applicability of
hybrid nanocomposites. Some examples of possible technological
applications of a few hybrid families were presented, such as
silica-modified SPEEK membranes, as possible replacement for
commercial Nalfion membranes, epoxy-POSS hybrid materials, and
Fe(II)- and Fe(III)-doped siloxane-PEO nanohybrids.
Template effect on the formation of vanadium oxide
nanostructures
G. Gonzalez, from the
Universidad Tecnológica Metropolitana, Santiago, Chile, in his
contributed talk first reviewed the interesting properties that make
nanoparticles such a popular area of research. Of particular
interest is the electronic structure of mixed valence oxides and
self- assembling phenomena. He then described the preparation of
vanadium oxide nanotubes using two different templates – long chain
alylamines and alkythiols. In addition, both templates can lead to
more complex 3D structures, depending on the preparation conditions.
Gonzalez also discussed the role of the surfactant and the reaction
conditions in the “roll-up” mechanism that transforms 2D laminar
nanostructures into 1D nanotubes.
Organized multilayered mesoporous core-shell colloids
with tailored chemical groups
A. Wolosiuk reported on his
research on organized multilayered mesoporous core-shell colloids
with tailored chemical groups. The confined domains of cavities and
pores allow modulation of electrical and optical properties as well
as ways to control catalysis, sorption, and separation. Stober’s
method was used to obtain silica core particles, while multiple
layered mesoporous shell syntheses were performed using various
alkoxy silane precursors and cationic surfactants as soft templates
for pore formation. Wolosiuk was able to tailor the thickness and
chemical composition of the mesoporous core shell colloids by
varying the reaction conditions. He confirmed the results using
FTIR, EDS, XPS, and TEM.
Symposium D: Powder Processing of Novel
Materials Viability of the use of colorful
clays of the Rio
Grande do Norte in artistic and
decorative ceramics
|
In the Rio Grande do Norte
state in Brazil, ceramics represent an important part of the local
economy, exclusively producing roofing tiles, bricks and blocks of
red ceramics. One of the interesting aspects of this is that the Rio
Grande do Norte has various clays with natural coloration, yielding
diverse oxides with a variety of colors including white, lilac,
orange. As described by Narayanna M. Farreira (Centro Federal de
Educacao Tecnologica do Rio Grande do Norte), the purpose of this
work was to characterize these clays using porosity measurements,
plasticity testing, thermal analysis, X-rays and Electronic Scanning
Microscopy. Depending on the time and the temperature of sintering,
characteristic colorations without the need to incorporate other
oxides or subsequent ceramic dyes could be obtained. Subsequently,
the ceramic powder is used as a liquid phase slurry in slip casting
to form the ceramics. Sintering emperatures of 900ºC, 950ºC, 1000ºC
and 1100ºC were used. Farreira showed examples of decorative and
colorful ceramic pieces produced using these clays as the raw
material. The colors of the clays were also correlated with the
compositions. The clays maintained their natural colors upto
sintering temperatures of 1100ºC above which changes in the color
were observed.
Symposium J: Applications of Lasers in Materials
Processing Laser material processing at IEAv
In an invited talk in Symposium
J, R. Riva recounted some of the laser methods for materials
processing developed at IEAv – the Institute for Advanced Studies,
created in 1982. Under the Photonics research division (other
divisions include Optics and Fiber Optic Sensors), Laser Research is
divided into laser development, laser isotope separation, and
materials processing. With nine PhD researchers, eight technicians,
and 12 students (undergraduates and graduate students), Riva
summarized the many accomplishments of his laboratory,
including:
- Laser heat treatment and
laser alloying process were both used to increase surface hardness
and to reduce the friction coefficient and wear of mechanical
components.
- Laser surface structuring
and texturing were used to control surface roughness in order to
obtain better adhesion of hard layers on substrates, increasing
the lifetime of mill and forging tools, as well as improving
surface lubrication of automotive components.
- Laser sintering of metal or
ceramic powder for rapid prototyping of mechanical components;
sintering successive thin layers allows fabrication of complex 3D
structures.
- Laser beam welding of
aeronautical aluminum using a high power fiber laser might soon
replace riveting aeronautical and aerospace structures.
- Laser beam micro-welding of
very thin metallic foils with nanosecond pulsed lasers for
applications like sensors and insulator membranes.
- Laser beam joining of
cable-connector electrical contacts for avionics
applications.
- Laser-induced fracturing to
improve manufacturing of automotive components; the technique has
also been used to fabricate rupture diaphragms with control of
hypersonic shock tunnel working pressure.
- Real time measurement of
laser beam quality; the innovative method based on light
scattering imaging can measure beam quality factor of just a
single laser pulse.
Symposium M: Electron Microscopy in
Industry Analysis of post-consumer polyethylene composites
reinforced with sugarcane bagasse-based
fibers
In a poster presented by
Alberto G. V. de Carvalho-Neto, Silvia L. Fávaro, A. C. M. da Rosa,
and E. Radovanovic of the Universidade Estadual de Maringá, PR,
Brazil, the authors described forming composites using waste
polyethylene (or as they called it, post-consumer PE) as the matrix
and waste sugarcane fibers (bagasse fibers) as the reinforcement.
Chemical modification of the sugarcane fibers was carried out to
improve their compatibility and adhesion to the matrix using an NaOH
solution followed by an acetylating reaction. The composites were
prepared using an extrusion process with 5, 10 or 20 wt% of fibers.
The morphology of the compsites was evaluated by SEM . The chemical
modification of the fibers was clearly found to improve the adhesion
between the matrix and the reinforcement fibers.
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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