The materials properties of mica have surprising similarities to those of living systems. The mica hypothesis is that life could have originated between mica sheets, which provide stable compartments, mechanical energy for bond formation, and the isolation needed for Darwinian evolution. Mechanical energy is produced by the movement of mica sheets, in response to forces such as ocean currents or temperature changes. The energy of a carbon-carbon bond at room temperature is comparable to a mechanical force of 6 nanoNewtons (nN) moving a distance of 100 picometers. Mica's movements may have facilitated mechanochemistry, resulting in the synthesis of prebiotic organic molecules. Furthermore, mica's movements may have facilitated the earliest cell divisions, at a later stage of life's origins. Mica's movements, pressing on lipid vesicles containing proto-cellular macromolecules, might have facilitated the blebbing off of ‘daughter’ protocells. This blebbing-off process has been observed recently in wall-less L-form bacteria and is proposed to be a remnant of the earliest cell divisions (Leaver, et al. Nature457, 849 (2009).

The rate law for CO oxidation over Pd-substituted BaCeO3 was studied. Under CO-rich conditions over a range of pressures and temperatures, changing reaction orders for both CO and O2 suggest the coexistence of both Langmuir-Hinshelwood and BaCeO3-mediated mechanisms. The latter dominates at high P(CO)/P(O2), while both mechanisms contribute significantly at low P(CO)/P(O2). Under CO-lean conditions, the Langmuir-Hinshelwood mechanism dominates the kinetics. The importance of the BaCeO3-mediated mechanism increases with temperature. Steady-state isotopic transient kinetic analysis (SSITKA) using 18O2 confirmed the participation of labile lattice oxygen, thus BaCeO3 behaves as a BaO-stabilized form of CeO2.

A summary is presented of our theoretical and experimental work over more than two years related to switching in chalcogenide glass phase change memory. As a significant addition to the well known experiments, we have studied switching under considerably lower voltages and elevated temperatures, as well as the statistics of switching events and relaxation oscillations. Our analytical theory, based on field induced crystal nucleation, predicts all of our observed features and their dependencies on material parameters.

The characterization of spatial distribution of different phases in materials provides understanding of structural influence on the properties and allows making physically well-grounded correlations. The FIB/SEM nanotomography opens new possibilities for the target microstructure characterization on the scales from 10 nm to 100 μm. It is based on the automatic serial sectioning by the focused ion beam (FIB). Scanning electron microscope in high resolution mode can be used for the imaging of nanostructured materials. Afterwards a detailed three dimensional (3D) image analysis enables the comprehensive quantitative evaluation of local microstructure. The possibilities of these techniques will be presented on the example of silver-composite contact materials which were analyzed using FIB nanotomography before and after exposure to plasma discharge. Significant changes in the spatial distribution of the oxide particles within the switched zone induce among other effects the changes in the local electric and thermal properties. These cause eventually the failure of the contact material. Advanced methods of image analysis allow characterization of inhomogeneous distribution of oxide particles in silver contact materials. Quantitative parameters characterizing the agglomeration of oxide inclusions and accumulation of pores can be derived from the results of distance transformations and morphological operations. The additional consideration of the connectivity allows the quantification of homogeneous and inhomogeneous states with high sensitivity and confidence level. Local thermal and electrical properties were estimated using simulation software on the real tomographic data. The combination of FIB microstructure tomography with modern 3D analysis and simulation techniques provides new prospects for targeted characterization and thus understanding of the microstructure formation and local effect associated with e.g. electro-erosion phenomena [1], [2]. First correlations between 3D microstructure parameters and resulting properties will be discussed.

The study of indentation responses of rate-dependent (viscoplastic or creeping) solids has generally focused on the relationship between indentation hardness and an effective strain rate, which can be defined from a similarity transformation of the governing equations. The strain rate sensitivity exponent can be determined from the slope of a log-log plot of the hardness versus effective strain rate, while determining other constitutive parameters requires a knowledge of the relationship between contact size, shape, and indentation depth. In this work, finite element simulations have shown that the effects of non-axisymmetric contact and crystallography are generally negligible. Theoretical predictions agree well with real nanoindentation measurements on amorphous selenium when tested above glass transition temperature, but deviate quite significantly for experiments on high-purity indium, coarse-grained aluminum, and nanocrystalline nickel. Such a discrepancy is likely to result from the transient creep behavior.

Conducting polymer materials can be developed as muscle-like actuators for applications in robotics, micro-electro mechanical systems, drug delivery systems etc. These materials are available in a large number of different varieties that can be synthesized and processed in different ways. However, their applications as actuators are limited due to the inability to create conducting polymer materials with robust mechanical properties. Currently most of the dynamic mechanical analysis technologies require the polymer created to be free standing and able to withstand large stresses. This severely limits the development of new materials with potential actuator applications. In this study, a technique to measure the actuation of polymers in the electrochemical deposition environment is described. This allows testing of an electrochemically grown conducting polymer sample on the surface of the deposition electrode itself. Thin polypyrrole films (2 to 20 microns thick) doped with tetraethylammonium hexaflourophosphate were grown on the surface of a glassy carbon electrode. These films were then tested on the surface of the glassy carbon using a custom built electrochemical dynamic mechanical analyzer. A square wave potential (+/- 0.8 V) is applied to the films that results in the actuation of the films. The films are able to generate a changing force of 3 mN of force against a 0.1 N sensor preloaded at 5 mN. The resulting magnitude of the measured force is a function of the film thickness while the change in force due to actuation is approximately constant.

Colloids generated from the engineered barriers of a high level radioactive waste repository (HLWR) emplaced in crystalline rock could play a significant role in radionuclide transport and they are of concern for the safety assessment of these repositories.

The main objectives of this study are: a) to analyze the transport properties of colloids in a crystalline fractured rock under hydrodynamic conditions as similar as possible to those expected in a repository (i.e. low flow rates) and b) to discuss the effects of their presence on the transport of radionuclides.

Transport experiments with bentonite and latex colloids in a fractured granite column from the Grimsel Test Site (Switzerland) were carried out, under geochemical conditions ensuring colloid stability (alkaline and low ionic strength water). Transport experiments were also carried out with 85Sr and 233U and the results with and without the presence of bentonite colloids were compared.

Colloid filtration in the fracture was always observed, even when colloids presented high stability and the conditions were unfavorable to colloid attachment to rock surfaces, being both the colloids and the rock negatively charged and the fracture surface smooth. The retention in the fracture depended on the water flow rate, increasing the retention as the water flow decreased.

This work illustrates as both the mobile and retained fraction of colloids, which strongly depend on the hydrodynamic conditions, are of importance in the overall radionuclide mobility.

Optimized compositions for bulk metallic glass (BMG) formation have been determined for the Cu−Hf binary and Cu−Hf−Al ternary systems. The Cu−Hf−Al BMG-forming composition region is identified to correlate with the (L → Cu10Hf7 + CuHf2 + CuHfAl) eutectic reaction. The eutectic temperature is reduced by nearly 50 K relative to that of the binary eutectic, demonstrating the significant role of the third element Al in stabilizing the liquid. The fragility parameter D* of the Cu55Hf45 binary and Cu49Hf42Al9 ternary supercooled liquid was determined from relaxation time measurements, indicating that Al incorporation also leads to a “stronger” liquid. The combination of these thermodynamic and kinetic effects is responsible for the dramatic enhancement of glass-forming ability from the Cu−Hf binary to the Cu−Hf−Al ternary.

We characterize a temperature sensor made from Erbium ions embedded in an amorphous AlGaN matrix that is accessed remotely by measuring the relative intensities from photoluminescence peaks of Er3+. We use this sensor to measure the nanoscale temperature around an optically excited single gold nanoparticle that has been immobilized on the AlGaN substrate. The maximum temperature increase measured experimentally is 8.3 K. The temperature measurement is diffraction limited by our microscope to 490 nm. This temperature corresponds theoretically to a maximum local temperature increase of 22 K. A straight-forward analysis using energy balance gives the thermal conductivity of the amorphous AlGaN substrate as 4.5 W/m-K.

Polycrystalline silicon (pc-Si) thin films have been synthesized by aluminium induced crystallization (AIC) of amorphous silicon (a-Si) at low temperatures (≤500°C) on flexible metallic substrates for the first time. Different diffusion barrier layers were used to prepare stress free pc-Si films as well as to evaluate the effective barrier against substrate impurity diffusion. The layers of aluminum (Al) and then amorphous silicon with the thickness of 0.27 μm and 0.37 μm were deposited on barrier coated metal sheets by means of an electron beam evaporation and PECVD, respectively. The bi-layers were annealed in a tube furnace at different temperatures (400-500°C) under nitrogen flow for different time periods (1-10hours). The degree of crystallinity of the as-grown layers was monitored by micro-Raman and reflectance spectroscopies. Structure, surface morphology and impurity analysis were carried out by X-ray diffraction, scanning electron microscopy (SEM) and EDAX, respectively. The X-ray diffraction measurements were used to determine the orientation of grains. The results show that the AIC films on metal sheets are polycrystalline and the grains oriented in (100) direction preferentially. However, the properties of AIC films are highly sensitive to the surface roughness.

We have investigated the effect of post-growth rapid thermal annealing (RTA) at different temperature on two InAs/GaAs bilayer quantum dots samples with different spacer thicknesses (7.5nm and 8.5nm). It is found that when RTA temperature gradually increases, there is usual blue shift of ground state emission peak wavelength for the sample having thinner spacer but for the other sample the emission peak sustains at same peak wavelength position upto a higher annealing temperature. The dots inside the sample with less spacer thickness dissolute much earlier (beyond 700°C annealing temperature) in comparison to the other sample. The structural and optical characterization has been done by cross sectional transmission electron microscope (XTEM) and low temperature photoluminescence (PL) experiments respectively.

Platinum nanoparticles stabilized by linear polyethyleneimine were prepared by the liquid-phase reduction of chloroplatinic(IV) acid with sodium borohydride. The particle sizes were 3.26 nm and 1.76 nm when the molecular weights of linear polyethyleneimine were 25000 and 2150, respectively. These nanoparticles were well-dispersed in water in the range of pH 1-6. Branched polyethyleneimine also provided nanoparticles that dispersed in water in the range of pH 0-8. Linear poly(ethyleneimine-co-N-methylethyleneimine) gave nanoparticles that dispersed in water in the range of pH 0-10. The dispersibility of the nanoparticles decreased with increasing content of the N-methyl group.

Measurement of elongational stresses, stereographic images of jet paths, innovative collection of fluid jets, and utilization of elongational flow for assembly or disassembly of particulate structures, the electron microscopic views inside nanofibers, and the morphological and crystallographic changes that occur during heating of the metastable electrospun fibers illuminate the growing versatility of the electrospinning process.

We report on recent advances in the development of a luminescence spectroscopy based on scanning tunneling microscopy (STM) and its application to fundamental aspects of Cu(In,Ga)Se2 (CIGS) thin films. Relevant to our discussion is the specifics of the surface electronics. The CIGS shows pronounced stoichiometric deviations at the surface and, consequently, distinct surface electronics that has been shown to be critical in achieving high efficiency. Cathodoluminescence (CL), a luminescence spectrum imaging mode in scanning electron microscopy (SEM), provides a direct correlation between the microstructure of the CIGS and its electronic properties. As such, cathodoluminescence can resolve the emission spectrum between grain boundaries and grain interiors or be used to investigate the influence of local orientation and stoichiometry on the electronic properties of the CIGS at the microscale. Cathodoluminescence is not a surface microscopy, however, and resolving the electronic structure of the CIGS surface remains elusive to all luminescence microscopies. With this motivation, we have developed a luminescence microscopy based on STM, in which tunneling electrons are responsible for the excitation of luminescence (scanning tunneling luminescence or STL). The hot-tunneling-electron excitation is confined to the surface and, consequently, the tunneling luminescence spectrum reveals the electronic states near the surface. The STM is integrated inside the SEM and, therefore, both CL and STL can be measured over the same location and compared. Using this setup, the transition from the grain interior to the surface can be investigated. We have improved the collection of our optics to a level in which tunneling luminescence spectrum imaging can be performed. Here we present a detailed account on our investigation of the surface electronics in CIGS deposited in the regime of selenium deficiency as defined by <Se>/(<Cu> + <In> + < Ga >) = 1.

The present study represents a first step towards an understanding of what we refer to as the functional fatigue behaviour of shape-memory polymers. These materials have a processing shape B and a programmed shape A [1]. And when the material is exposed to an appropriate stimulus (in our case: heating above a critical temperature), a one way effect is observed: A → B (one way effect: 1WE). The objectives of the present study were to find out whether and how often programming can be repeated, whether repeated programming affects the 1WE and how much irreversible strain the material accumulates. We study the effect in dependence of different stress levels, and consider the effect of recovery temperature and recovery time. As a model material we examine the commercial amorphous shape-memory polymer Tecoflex® and subject it to 50 programming/1WE cycles. It turns out that programming, cooling, unloading and heating to trigger the 1WE causes an increase of irreversible strain and is associated with a corresponding decrease of the intensity of the 1WE in particular during the first thermomechanical cycles.1. M. Behl and A. Lendlein, materials today 10, 20 (2007).

Thermo-sensitive multiphase polymer networks with triple-shape capability have been recently introduced as a new class of active polymers that can change on demand from a first shape A to a second shape B and from there to a permanent shape C. Such multiphase polymer networks consist of covalent cross-links that determine shape C and at least two phase-segregated domains with distinct thermal transitions T trans,A and T trans,B , that are associated to shape A and B. In general the application of a two step programming or a one step programming procedure is required for creation of triple-shape functionality. In this study we report about a series of CLEGC nanocomposites consisting of silica coated nanoparticles (SNP) incorporated in a multiphase graft polymer network matrix from crystallisable poly(ε-caprolactone) diisocyanatoethyl methacrylate (PCLDIMA) and poly(ethylene glycol) monomethyl ether monomethacrylate (PEGMA) forming crystallisable side chains. These CLEGC nanocomposites were designed to enabling non contact activation of triple-shape effect in alternating magnetic field. Composites with variable PCLDIMA content ranging from 30 wt-% and 70 wt-% and different SNP amounts (0 wt-%, 2.5 wt-%, 5 wt-% and 10 wt-%) were realized by thermally induced polymerization. The thermal and mechanical properties of the CLEG nanocomposites were explored by means of DSC, DMTA and tensile tests. The triple-shape properties were quantified in cyclic, thermomechanical experiments, which consisted of a two step programming procedure and a recovery module under stress-free conditions for recovery of shapes B and C.While the thermal properties and the Young’s modulus of the investigated polymer networks were found to be independent from the incorporated amount of SNP, the elongation at break (εB) decreases with increasing nanoparticle content. All investigated composites exhibit excellent triple-shape properties showing a well separated two step shape recovery process.

The generation of high frequency steady-state photoconductivity in nitrogen doped hydrogenated amorphous silicon (a-Si:H-N) films has been demonstrated at infrared (IR) frequencies of 650 to 2000 cm-1 or 15 to 5 μm in wavelength. This allows IR photoconductivity to be observed using a simple thermal source. In order to produce high frequency photoconductivity effects the plasma frequency must be increased to the desired device operation frequency or higher as described by the Drude model. IR ellipsometry was used to measure the steady-state permittivity of the a-Si:H-N films as a function of pump illumination intensity. The largest permittivity change was found to be Δεr = 2 resulting from a photo-carrier concentration on the order of 1022 cm-3. IR photoconductivity is shown to be limited by the effective electron mobility at IR frequencies.

This symposium is a memorial to Dr. Marni Goldman. Although she never walked and had only limited use of her arms, Marni's academic and professional accomplishments placed her in elite company. She obtained two bachelors degrees from the University of Pennsylvania and a Ph.D. in Materials Science from the University of California at Berkeley. Even with a heavy course load, she was involved in educational outreach during her studies. She started her career as a Research Associate (Education Director) in Stanford's NSF Materials Research Science and Engineering Center on Polymer Interfaces and Macromolecular Assemblies in 2000 and retained those responsibilities until her death in 2007. During this period she rapidly added the responsibilities as Education Director for Stanford's Nanofabrication Facility and was ultimately named Associate Director of Stanford's Office of Science Outreach. Marni was a dynamo whose activities at Stanford included a large summer undergraduate internship program, a Research Experiences for Teachers program (local and national activities), a program to bring community college students (especially minority students) to the campus, public science (San Jose Tech Museum of Innovation, San Francisco Exploratorium), outreach to high schools with high minority populations, and a program with summer internships for students with disabilities. Marni's achievements are thanks in no small part to her extraordinary family, to her own intelligence and tenacity, and to a wide and loving circle of friends, drawn to her by the spirit of her determination and the unmistakable largeness of her heart.

The US Navy continues to pursue electrochemical power sources with high energy density for low rate, long endurance undersea applications. The direct electro-oxidation and electro-reduction of sodium borohydride and hydrogen peroxide are being investigated to meet these goals. In an effort to minimize polarization losses and increase power density, a novel carbon microfiber array (CMA) electrode is being investigated.

The CMA is composed of 750 micron long, 10 micron diameter graphite fibers that protrude from a current collector like blades of grass. The CMA was developed for the direct reaction of peroxide in the Mg-H2O2 semi fuel cell. [1] There, the high surface area of the microfiber cathode reduces peroxide concentration polarization, resulting in increased power and energy density. For this work the CMA architecture was adapted into a novel membrane electrode assembly and evaluated in the direct BH4- / H2O2 fuel cell. The unique feature of this architecture vs. traditional membrane electrode assemblies (MEAs) is how all three components of the triple boundary interface are optimized: electrical connectivity, ionic connectivity and mass transport. The current iteration of this electrode architecture utilizes a carbon cloth that has been hot pressed into N115 membrane. This component is then placed over the CMFA electrode. The carbon microfibers of the CMFA protrude up into the carbon cloth matrix forming a 3-dimewnsional, interdigitated electrode architecture. The result of this modification is improved electrolyte flow through the CMFA and improved utilization of the surface area afforded by the carbon microfibers that was not observed in the non modified CMFA.Half cell polarization measurements were obtained simultaneously with the fuel cell polarization. Initial results using this modified CMFA electrode architecture show that the polarization losses observed for both the reduction of hydrogen peroxide and for the oxidation of borohydride were 5.2 times lower than for the non-modified CMAs electrode (0.014 ohms vs. 0.074 ohms). Comparing these results to those calculated from the literature [2, 3], where traditional membrane electrode assemblies were used for borohydride oxidation, 5 and 2.6 time improvements were obtained (0.07 ohms and 0.037 ohms were the effective resistive losses seen in the anode half cell polarizations).

Functional carbonaceous materials, organic electronic materials, and polymer materials which "speak the language" of biomaterials in their propensity for hierarchical structure formation play a central role in current materials science research. In this context, we prepared hierarchically structured conjugated polymers from diacetylene macromonomers based on β-sheet-forming oligopeptide-polymer conjugates as supramolecular building blocks. The monomers gave rise to supramolecular polymers with a finite number of strands, a uniform diameter of a few nanometers, and defined superstructures. These were then converted into conjugated polymers under retention of their hierarchical structures, leading to poly(diacetylene)s with multiple-helical quaternary structures and a rich folding behavior. The diacetylene macromonomers served as a model system to improve our understanding of how to use hydrogen-bonding sites in order to control the placement of reactive molecular precursors for hierarchically structured organic materials.