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5th Brazilian Materials Research Society Meeting (SBPMat)
October 8 - 12, 2006 | Florianópolis, Brazil
In co-operation with the Brazilian MRS
(Sociedade Brasileira de Pesquisas em Materiais) |
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Day 3 - Tuesday
The third day of the 5th Brazilian Materials Research Society Meeting (SBPMat) included a number of events and activities, including a full day of technical oral sessions, a well-attended plenary lecture on quantum computing, a full poster session, the exhibit, as well as a roundtable held at the end of the day on trends in industrial research vs academic research in Brazil.
PLENARY LECTURE
The plenary talk of the day was given by Prof. Luis Davidovich (UFRJ, Rio de Janeiro,
Brazil) who gave an outstanding talk on "Quantum Information: From Einstein To
Quantum Computers" to a packed room. There is significant current interest in developing quantum computers. There are two main motivations for this - the tremendous recent progress in quantum manipulation of atoms, and the limits on classical computational techniques. There are other motivations as well including the possibility of solving the factorization problem, which could result in the breaking of the current RSA code widely used in encryption technology. Davidovich went into details about possibilities for quantum information exchange. He described the quantum bit, or qubit, and photons which are flying cubits. He also discussed the peculiarities of quantum information, including the fact that it is not possible to measure the state of polarization of a single photon and it is not possible to clone a qubit.
Davidovich then talked about entangled states including photonic entangled states. There are materials science-related aspects to this field, and papers have now been published on atom-photon entanglement, entanglement of trapped ions, entangled quantum state of magnetic dipoles etc. The issue of entanglement is crucial for quantum information exchange and quantum computing. There are several candidate experimental technologies for quantum computing including ion traps, quantum dots, NMR, optical lattices, and Josephson junctions. The problem with all of these is decoherence. Davidovich concluded by suggesting that the new experimental techniques are promising for quantum computing. The field is strongly interdisciplinary involving fields such as quantum physics, computer science, engineering and materials science. Some aspects of quantum cryptography and quantum computers have already been demonstrated.
The future is mine!
TECHNICAL TALKS
Symposium F: Nanostructures and Defect Analysis by Electron Microscopy
Nanowires and Suspended Atomic Chains of Gold and Silver
Time-resolved high resolution transmission electron microscopy (HRTEM) results and molecular dynamics simulations of atomistic aspects associated with stretching of Au-Ag nanowires were reported by Daniel Ugarte (IFGW-UNICAMP and LNLS) in his invited talk within symposium F. While atomic-sized pure metal nanowires have been previously obtained by mechanical stretching, limited data is available for alloy nanowires. Ugarte's group used in situ HRTEM to focus the electron beam on Au-Ag thin films, with nanobridges forming between the holes. These were then stretched to obtained atomic-size nanowires. The results revealed that, unlike pure metals, structural defects, primarily twins and stacking faults, are sometimes present at the apexes and very close to the narrowest wire constriction, or even within the nanowires. Also, similar to pure
nanowires, linear suspended chains of atoms were observed. which represents the first experimental evidence for this in metallic alloys. It was also observed that the atomic-size Au-Ag alloy nanowires exhibit a spontaneous gold enrichment at the nanojunction region during the wire thinning process, resulting in a dominant gold-like behavior, even for alloys with minor gold content. This suggests the ability to control the stability or length of the atomic chains by using an appropriate and suitable alloy composition.
[View extended abstract]
 
Carbon Aerogels and C/metal Nanocomposites Formed Using Supercritical CO2 Processing
The use of the supercritical regime of CO2 is useful for chemical and materials processing. It has recently been used for processing nanostructured materials. In his presentation, Mark Aindow presented work on using supercritical CO2 (scCO2)to synthesize carbon aerogels (CA) and carbon-metal nanocomposites. The CAs were produced by sol-gel polymerization of resorcinol and formaldehyde to produce a hydrogel, which was converted to a CA by solvent exchange, scCO2 drying and thermal pyrolysis. The CAs had mesopores ranging from 3 to 25 nm. Further thermal processing yielded stable C structures. Metal-carbon nanocomposites were formed by organometallic-scCO2 solution to impregnate the carbons with a monomolecular layer of an
organometallic precursor and then to reduce this to give a distribution of metallic nanoparticles over the C
surface. Aindow showed results for both Ru- and Pt-carbon nanocomposites. Ru and Pt are catalysts and these nanocomposites could be used for fuel-cell applications. Aindow also described the radiolytic formation of buckyonions from the CAs. Finally, he showed the formation of C-encapsulated nanoparticles by loading the CAs with Ru in one example, and heat-treating it. The advantage of this is the significant chemical stability of the encapsulated nanoparticles.
[View extended abstract]
Courtesy: M. Aindow, Univ. Connecticut
C-encapsulated Ru nanoparticle.
Symposium H: 5th Brazilian Electroceramics Symposium Fabrication of SnO2-based Ceramics for Varistors
A varistor is a device that is used to protect electrical circuits against excessive transient voltages. Varistors typically have non-ohmic I-V characteristics. In his presentation (in Portuguese), M.A Ramírez (Universidade Estadual Paulista, UNESP, Araraquara, Brazil) described continuing work on the fabrication and development of varistor ceramics based on SnO2. The SnO2-based system has been shown to have excellent electrical properties including a high value of the nonlinear coefficient, a high electrical breakdown field (3900 V/cm) and low leakage current (below 90 μA). In this presentation, Ramirez reported properties of varistor samples of the SCNCr system (98.9%SnO2+1%CoO+0.05%Nb2O5+0.05Cr2O3 (mol%)) with different area-volume (A/V) ratios sintered at 1300°C in an ambient atmosphere. It was shown that the A/V ratio had little effect on the electrical and microstructural properties of the SCNCr system when sintered at 1300°C, thus indicating a very stable system, as compared to the traditional ZnO based varistors.
[View extended abstract]
"Here's the plan ....."
Multiferroic Ceramics Obtained by a Co-Precipitation Technique
Multiferroics are materials in which at least two of the ferroelectric, ferro/antiferromagnetic and ferroelastic phases coexist. Marina Villegas (Instituto de Cerámica y Vidrio – CSIC, Madrid, Spain) described a co-precipitation method to form zinc, nickel and cobalt ferrites, MFe2O4 (the ferromagnetic phase, FM) by
coprecipitation using cobalt and iron chlorides, and nickel and zinc nitrates as
precursors and NaOH as precipitant agent. Commercial BaTiO3 was used as the ferroelectric phase (FE). The two were mixed to obtain a multiferroic material with a composition of xFM-(1-x)FE with x=0.2 and 0.4, and these mixtures were sintered at 1200ºC to obtain magnetoelectric materials. A clear magnetoelectric response was obtained. The co-existence of the FE and FM phases were corroborated by X-ray diffraction.
[View extended abstract]
"I know this really great restaurant."
NiCu/CGO Anodes for Direct Oxidation of Hydrocarbons and Alcohols
Fuel cells are an important method of making electrical use of fuels like methanol, natural gas or higher hydrocarbons. Agusti Sin in his talk on Monday described the development of new anode electrodes from the synthesis of nanoparticles and nanocomposites for cathodes (LaSrCoFeO) and anodes (NiCu + CeGdO). Colloidal and sol-gel chemistry were used to synthesize the raw nanomaterials and the “gentle chemistry" allows the crystallization temperature of oxides to be reduced significantly thereby obtaining extremely fine materials. It also allowed the deposition of layers of controlled thickness and composition and could be used to commercially produce fuel cells. Ball milling produced particles of 9.1 microns, the electrode deposition was made by spraying on to a hot plate at 200C and then a complex thermal treatment between 100 and 700C produce the final product. The cells worked for more than 10 days and the performance improved with time. The optimum anode material was Ni(0.2)Cu(0.8). Steam was used in the process to avoid a build up of carbon.
[View extended abstract]
Zirconia-Yttria/Zirconia-Magnesia Composites for Disposable High-Temperature Oxygen Sensors
Erica Caproni from IPEN showed that a zirconia-yttria/zirconia-magnesia composite used for oxygen detection has a higher electrical conductivity than commercial zirconia-magnesia solid electrolytes while showing similar shrinkage behavior. The emf output for the same oxygen level is thereby raised and the response time at 1000°C is 30s which is a very good value.
[View extended abstract]
Symposium M: Advanced techniques of Microscopy for Characterization and Modification of Materials- MICROMAT
Current Trends in Sub-wavelength Microscopy
P.S. Dorozhkin (NT-MDT Co., Moscow) described a setup that combined in one instrument a wide range of scanning probe techniques including Scanning Kelvin Microscopy, Electrostatic Force Microscopy, Atomic Force Acoustic Microscopy and several others, based on different types of interactions between an AFM probe and the surface. With this setup an investigator can determine whether single or double walled nanotubes were formed and 3d imaging can also be performed. Other applications include seeing areas of ZnTe that have very low luminescence and observing a nanotube acting as an optical fiber. The ability to get multiple images enables very rich investigations of samples.
[View extended abstract]
"Brazil is definitely going to win the
World Cup in 2010."
Nano-manipulator for In Situ SEM Experiments
D. Ugarte/Vitor Oiko, LNLS/Unicamp-IFGW, described the development and application of an inexpensive two probe tip nanomanipulator for in situ experiments in an SEM. The manipulator includes two kinds of movements: coarse, with mm range and submicron precision, and fine, with micron range and few nanometers of precision. Coarse movements are based on parallel guiding spring mechanics which include no moving parts so they do not require lubrication. Fine movements are based on piezoelectric elements and give a precise three-axis movement of both probe tips which have independent electrical supplies, allowing a wide range of nanomanipulation and nanocharacterization experiments. The system has been used for different kinds of in-situ experiments, such as: a) fabricating high aspect-ratio AFM tips based on multi-walled carbon nanotubes; b) collecting, moving and positioning semiconductor nanowires (50-200 nm in diameter, microns in length) on pre-defined electrical contacts or special sample sites; c) measuring electrical properties of nanowires inside the microscope. An interesting fact is that only carbon nanotubes are strong enough to provide probes at this scale. Diamond does not do it.
[View extended abstract]
Brazilian coffee - the best in the world? |
After the break.... |
Symposium B: Recent Advances in Powder Technology
Thermal Resistance of Perovskites with Cerium for Methane Oxidation
Maria Conceicao Greca, of the Laboratorio de Catalise, Rio de Janeiro, Argentina, presented a poster on the use of Perovskites as catalysts for methane oxidation. She showed that the introduction of cerium into the perovskite to replace lanthanum in the A position in the lattice leads to improved thermal stability of the cubic structure up to temperatures of 1100°C thereby improving its efficient use at elevated temperatures. Structures without cerium tend to degrade at 700°C.
[View extended abstract]
Symposium E: International Symposium on Hybrid Materials and their Applications Characterization of the Mechanical and Thermal Properties of Poly(e-Caprolactone ) and Cellulose Acetate Blends
Marcelo Bardi, of the Universidade Sao Francisco, Brazil, presented a poster on his study of the mechanical properties of a blend of poly(e-caprolactone) (PCL) and cellulose acetate (CA). This is an attempt to find an inexpensive biodegradable material that has some of the high tensile strength of CA. Since PCL and CA are naturally immiscible and incompatible it is necessary to add a compatibilizer (polyethylene-graft-glycidyl methacrylate (PE-g-GMA)). The results indicate that the compatibilizer did not affect the miscibility of the system but affected the organization of the polymer chains. The 40-60 blend had the best mechanical properties.
[View extended abstract]
© Materials Research Society, 2006 |
