ndThe 2 International Conference
NANOMATERIALS AND NANOTECHNOLOGIES
Creta Maris Hotel, Hersonessos, Crete, Greece
June 14 – 18, 2005
Web site: http://www.ipme.ru/ipme/conf/NN2005/
INTERNAL STRESS ANALYSIS FOR NANOSTRUCTURED Li-BATTERY
K. E. Aifantis
DAMTP, Centre for Mathematical Sciences, Cambridge, UK
Due to the small Li-intercalation of carbon, which is used as the base material for the negative electrode in rechargeable Li-batteries, extensive research is being performed, for over two decades in order to find alternative anode materials. This research has suggested that some of the best candidates are Sn and Si, due to their high capacity. These materials, however, have not been used commercially because of their large volume expansion, which results in crumbling of the electrode after continuous electrochemical cycling. It is therefore of great importance to model the internal stress development inside these anodes. Since the miniaturization of the high-energy storage devices at hand is desired, gradient elasticity is employed to capture size effects as the scale of the microstructure is reduced to the nanoscale; comparison with solutions obtained from classical elasticity are made.
Spontaneous self-agglomeration of magnetic nanoparticles into nanowires
1123I. Alexandrou, D. K. H. Ang, G. A. J. Amaratunga, S. Haq
1. Electrical Engineering and Electronics, University of Liverpool, Liverpool, UK
2. Department of Engineering, Cambridge University, Cambridge, UK
3. BAE Systems, Advanced Technology Centre, Bristol, UK
A newly developed method for the formation of nanowires by self-aggregation of nanoparticles is presented in this paper. The first experiments have been performed using Co-rich nanoparticles dispersed on a holey carbon grid. The nanoparticles are inserted in a vacuum oven and are annealed at temperatures below 400C in the presence of a hydrocarbon vapour without the use of any externally applied electric or magnetic fields. High resolution electron microscopy (HREM) was extensively used to determine the shape, size distribution and crystallographic phase of the starting and produced materials. Interestingly, after an annealing circle of 72 hours, the nanoparticles seem to self-agglomerate into nanowires which have diameters in the 5-20nm range and lengths exceeding at cases 1 micron. The diameter of the produced wires is in the same range as the diameter of the initial nanoparticles, further supporting the notion that the nanowires have formed out of the nanoparticle agglomeration. Close inspection of nanowire HREM images shows that the structure of the nanowire body indeed resembles at cases linked nanoparticles. Phase identification has also been performed using the HREM images and a comparison between the starting material and the produced nanowires will be presented.The process presented here shows that nanoparticles can spontaneously self-align into nanowires in way never reported before. Therefore there is certainly scope for studying this method further to reveal more information about the catalytic action of transitional metals on hydrocarbons and the exact nanowire formation mechanism. Although it is currently a matter of speculation, this process might lead to the effortless growth of nanowires at particular places when building miniature circuits.
The Relationship Between Stability/Nanostructured Omega Phase/Mechanical
Properties of Beta Titanium Alloys
S. Ankem, A. Jaworski Jr.
University of Maryland, College Park, MD, USA
The mechanical behavior of various Ti-V alloys was studied at room temperature. The beta phase of these alloys, which has a BCC structure, contains a nanostructured omega phase. When a single phase beta Ti-V alloy was deformed, the primary deformation mechanism was found to be twinning. Upon twinning the omega phase, which is present in the parent crystal, reforms in the twin. However, when a beta phase with similar stability in the presence of alpha phase was deformed, the beta phase was found to deform by the formation of stress induced HCP martensite. When this martensite forms, the nanostructured omega phase was found to disappear, i.e. the omega phase was consumed during the stress induced transformation. The effect of this on the mechanical properties and the details of the investigation will be presented. This work is being funded by the National Science Foundation under grant number DMR-0102320.
Multi-scale Modeling of Titanium Dioxide: Controlling Shape with Surface
123Amanda Barnard, Peter Zapol, Larry Curtiss
1. Center for Nanoscale Materials and Materials Science Division, Argonne National
Laboratory, Argonne, IL, USA
2. Center for Nanoscale Materials, Materials Science and Chemistry Divisions, Argonne
National Laboratory, Argonne, IL, USA
3. Materials Science and Chemistry Divisions, Argonne National Laboratory, Argonne, IL, USA
An important aspect in the use of titanium dioxide at the nanoscale for advanced photochemical applications is the controlled manipulation of the size, phase and morphology of the nanoparticles in solution. Solution pH is widely used to manipulate such properties at the nanoscale. We have used a multi-scale model designed to describe nanoparticles thermodynamics as a function of size, shape and chemical environment to investigate the effects of pH on the shape and phase stability of titanium dioxide nanoparticles. As input for the model, surface energies and surface tension of low index stoichiometric surfaces of anatase and rutile under hydrogen rich and hydrogen poor conditions have been calculated using density functional theory. Our results show how anatase phase is stabilized in acidic solution while the rutile is stabilized in basic solution, and that pH may also be used to control the particle shape and therefore the chemical functionality.
Computational Nano-morphology: Modeling Shape as well as Size
12Amanda Barnard, Larry Curtiss
1. Center for Nanoscale Materials and Materials Science Division, Argonne National
Laboratory, Argonne, IL, USA
2. Materials Science and Chemistry Divisions, Argonne National Laboratory, Argonne, IL, USA
As the demand for nanomaterials tailored to particular applications increases, so to the need for robust, monodispersed nanomaterials with reproducible and highly uniform properties will grow. It has been widely shown that many fundamental properties of nanomaterials have a strong dependence on particle size. Although great advances have been made in controlling the size of nanoparticles, variations of some properties still remain due to a dependence of the property not only on size, but also on the morphology. Individual particle properties such as quantum confinement, nanomagnetism, and catalytic properties have been found to be shape dependent, as have collective properties such as the self-assembly of metallic nanoparticles arrays. Therefore, nano-morphology must be carefully controlled to reliably synthesize large quantities of nanoparticles with uniform properties. We present results of a thermodynamic model designed to describe the shape of nanoparticle as a function of size and chemical environment; and show how the model may be used to explain how the shapes of nanoparticles differ from their macroscopic counterparts, and to predict the morphology of nanoparticles under desired conditions.
Synthesis and characterization of copper nanoparticles inserted in organic
Boudjahem Abdel-Ghani, Ksouri Rabah, Merdes Rachid
University of Guelma, Guelma, Algeria
Unsupported and supported copper nanoparticles are obtained by reduction of copper nitrate by the polyol process and characterized by X-ray diffraction, SEM, and TEM. The study we have undertaken on the preparation of copper nanoparticles showed that they can be obtained in a wide range of size depending on the concentration of the copper salt or ethylene glycol, the presence of a second metal, temperature and time of reduction, presence or not of a stabilizer or support, the metal loading in the case of supported materials. Addition of Ag and decreasing the copper content or increasing the EG/copper ratio decreased the metal particle size. Silica surface defects were suggested as catalytic sites which accelerated copper ions reduction in the presence of silica as surfactant or support. Strong metal- support interaction and reduction rate were the main factor determining the size and morphology of the supported metal particles formed. The thermal study of the copper nanoparticles evidenced the presence of an organic matrix and gave some structural information on the fresh samples.Hydrogen thermal treatment of the reduced phase showed also that the organic fragment, belonging to the precursor salt, still remained attached to the supported or unsupported copper particles as stabilizing matrix.The organic matrix retained on the reduced copper phase played a similar role as silica, that of stabilizing a agent of the metal nanoparticles
Nanocrystalline HF-CVD-grown Diamond and its Industrial Applications
Kai Bruehne and Hans J. Fecht
University of Ulm, Center for Micro- and Nanomaterials, Ulm, Germany
The correlation between the micro- and nanostructure of a material and its physical and chemical properties is the key issue in materials development. Considerable progress has been achieved recently by the development of new processing technologies (hot-filament-CVD-deposition) and new materials in a nanocrystalline state (nanodiamond) with superior mechanical strength and tribological properties. A novel fabrication method, based on CVD diamond deposition has recently been established at the University of Ulm. Reliable processing parameters have been developed in order to produce 30 - 40 micrometer thick samples of diamond with an average grain size of about 15 nm on 2 inch diameter silicon wafers. Further processes based on lithographic techniques known from silicon technology allow further microstructuring of CVD-diamond. This approach is unique world-wide. So far, the microstructuring of highly oriented columnar diamond has been hampered by the fact that the internal microstructure is being reproduced by plasma etching yielding rather rough surfaces. This problem now can be overcome by the production of nanoscale diamond. It can be expected that microparts (microtoothed wheels, atomically sharp cutting edges, functionalized diamond surfaces etc.) can be produced on a reliable basis in the near future. The fabrication of ultra sharp diamond cutting edges, resulting in radii of curvature below 10nm has already successfully been demonstrated. However, major stepping stones have to be overcome, such as, for example, the control of internal stresses limiting the film thickness, homogeneity of the films, doping procedures etc.
STUDY OF SELF-ASSEMBLED MONOLAYERS OF DNA AND DNA-
CARBON NANOTUBE HYBRIDS AND THEIR APPLICATION TO DNA
Germarie Sánchez-Pomales, Yarinel Morales-Negrón, Carlos R. Cabrera
Chemistry Department, University of Puerto Rico, San Juan, Puerto Rico
Recent interest on the design and fabrication of new types of bionanosystems has increased the amount of studies regarding the functionalization of nanomaterials with biomolecules. These novel systems have the potential to be used in a variety of applications, including chemical and biological probes and sensors. This work presents the study of the supramolecular complex formed by the non-covalent functionalization of carbon nanotubes by DNA. The optimal conditions for the formation of these hybrids will be determined. In addition, gold substrates will be modified by self-assembled monolayers of mercaptohexanol, DNA and DNA-carbon nanotube hybrids, and the efficiency of the modification will be determined by microscopic, electrochemical, and spectroscopic techniques. Parameters such as concentration, immobilization time, and DNA length and sequence will be studied. These studies will enhance our understanding of the interaction between DNA and carbon nanotubes, which will lead us to develop more efficient bionanomaterials, in particular DNA sensors.
Rheology of CuO nanoparticle suspension prepared by ASNSS
11123Chih-Hung Lo, Ho Chang, Tsing-Tshih Tsung, Hong-Ming Lin, Ching-Song Jwo
1. Department of Mechanical Engineering, National Taipei University of Technology,Taipei,
2. Department of Materials Engineering, Tatung University, Taipei, Taiwan 3. Department of Air-Conditioning and Refrigeration Engineering, National Taipei University of
Technology, Taipei, Taiwan
In this study, a low-pressure control method for an arc-submerged nanoparticle synthesis system (ASNSS) was proposed and developed for CuO nanoparticle fabrication. This study investigates into the rheology of CuO nanofluid having different mean particle sizes. Experimental results indicate that the pH value of the CuO nanofluid fabricated in this study is 6.5, which is far smaller than isoelectric point (i.e.p) of pH 10. The CuO nanofluid with larger mean particle sizes has a larger shear stress when the shear rate of different mean particle sizes are the same. Moreover, the smaller the mean particle size of the CuO nanofluid, the higher its viscosity is because of the larger the specific surface area, and the electrostatic force between particles would also be increased.