A reliable quantitative analysis in electron tomography, which depends on the segmentation of the three-dimensional reconstruction, is challenging because of constraints during tilt-series acquisition (missing wedge) and reconstruction artifacts introduced by reconstruction algorithms such as the Simultaneous Iterative Reconstruction Technique (SIRT) and Discrete Algebraic Reconstruction Technique (DART). We have carefully evaluated the fidelity of segmented reconstructions analyzing a disordered mesoporous carbon used as support in catalysis. Using experimental scanning transmission electron microscopy (STEM) tomography data as well as realistic phantoms, we have quantitatively analyzed the effect on the morphological description as well as on diffusion properties (based on a random-walk particle-tracking simulation) to understand the role of porosity in catalysis. The morphological description of the pore structure can be obtained reliably both using SIRT and DART reconstructions even in the presence of a limited missing wedge. However, the measured pore volume is sensitive to the threshold settings, which are difficult to define globally for SIRT reconstructions. This leads to noticeable variations of the diffusion coefficients in the case of SIRT reconstructions, whereas DART reconstructions resulted in more reliable data. In addition, the anisotropy of the determined diffusion properties was evaluated, which was significant in the presence of a limited missing wedge for SIRT and strongly reduced for DART.

The mechanical and thermal behavior of nanoglasses (NGs) were studied with a focus on the effect of the microstructure. The thermal expansion was measured to track changes in excess free volume during heating. It was found that the excess free volume, which is initially more dominant in the interphase region between the denser amorphous particles, is partially lost as well as redistributed during annealing. This relaxation during heating causes the nanoglass to behave like a melt-spun ribbon after heating while remaining amorphous. Nanomechanical tests were used to probe the local incipient plasticity and the influence of the interphase region. This interphase appears to affect the mechanical response of the NGs by inhibiting the propagation of shear bands and thus offers a novel approach for the introduction of plasticity in bulk metallic glasses. The results suggest that the NGs consist of two distinct amorphous phases with different glass transition temperatures.

Solid-state based battery technology offers, in principle, the largest temperature range (from room temperature to 500 °C) of any battery technology. In fluoride based batteries, the chemical reaction used to create electrical energy is a solid-state reaction of a metal with fluoride anion [1]. Among the various types of solid preparation techniques, the mechanochemical synthesis has been recognized as a powerful route to novel, high-performance, and low-cost materials [2]. Thus, a mixed and highly disordered fluoride phase with retained cubic symmetry can be obtained with a very high Fˉ diffusivity [3].

In our group, a series of new electrolytes was developed, namely LaF3-BaF2-KF solid solutions, using mechanosynthesis method. The cubic structure of the product was confirmed by XRD. The nanoscale nature and morphology of the samples were characterized by SEM and TEM. First Solid-state electrochemical cells were built with LiF based composite cathode, LaF3-BaF2-KF derived electrolyte and Fe based composite anode.

Nanocrystalline zirconia particles coated with polymers have been prepared by a two step Chemical Vapor Synthesis process using a hot wall reactor to synthesize the nanocrystalline ceramic core and a subsequent RF plasma reactor for the polymer coating. The polymer coating is built up of organic byproducts of the pyrolysis of the zirconia precursor. By using continuous and pulsed plasma deposition and variation of the plasma parameters, such as RF power, period and duty-cycle, the structure and thickness of the polymer coating can be influenced. Typical particle radii are in the range of 3 to 4 nm with radii of the ceramic core in the range of 2 nm and a coating thickness in the range of 1 to 2 nm. The powders have been characterized by FT-IR, XRD, BET and HRTEM. Consequences for the dispersibility are reported.

In the multilayer system cobalt / copper at the second antiferromagnetic coupling maximum (2. AFM) with a copper thickness of dCu = 2,2 nm it is possible to reduce magnetoresistive hysteresis by the use of either very thin Co-layers or by alloyed magnetic layers Co1-xCux. It was possible to achieve values for the giant magnetoresistance effect of GMR ≈ 20 % for as prepared samples. A heat treatment was applied to study the degeneration of the system. For annealing at moderate temperatures (Tanneal ≤ 250°C) an increase up to GMR ≈ 25 % was observed. Annealing at slightly higher temperatures lead to an rapid decrease in the GMR effect. To study the structural changes the method of x-ray reflectivity was utilized showing changes in interface roughness as well as in bilayer thickness.

An Aerosol Mass Spectrometer (AMS) is a combination of a Quadrupol- (QMS) and a Particle Mass Spectrometer (PMS) and enables the in-situ analysis of gas phase processes for the generation of nanoparticles. Size distributions of ultrafine silicon carbide particles in the range of 104 atomic mass units (amu) to 107 amu are measured in the PMS. Simultaneously, molecular species up to 300 amu can be detected in the QMS. Aerosols containing nanocrystalline silicon carbide are produced from tetramethylsilane (TMS) by thermal decomposition. In situ process analysis with the AMS as a function of process parameters was performed to elucidate the formation and growth mechanism of SiC nanoparticles.

We have prepared thin yttria-stabilized zirconia (YSZ) electrolyte layers by chemical vapor deposition (CVD) on a pre-sintered NiO/YSZ fuel cell anode substrate. Structural analysis by scanning electron microscopy (SEM) and x-ray-diffraction shows a homogeneous, nanocrystalline layer.

Conventional electrolyte films reach desired electrical properties only at elevated temperatures, typically 1000°C to 1100°C. The YSZ films grown by CVD on rough anode substrates show better growth behavior and less defects at the anode/electrolyte interface than films deposited by conventional methods (screen printing, sol-gel). Results of electrical properties at lower SOFC working temperatures are obtained by impedance spectroscopy on pressed nanocrystalline YSZ powder pellets produced by chemical vapor synthesis (CVS).

The catalytic oxidation of methane was studied over palladium supported on nanocrystalline ceria. Three palladium weight loadings (1, 5, and 10 wt%) were tested after calcining at 500 °C, at 280 °C and after no calcination at all. For the 5 and 10 wt% loadings, the 280 °C-calcined and non-calcined catalysts exhibit enhanced activity after several heating and cooling cycles. Calcining these same catalysts at 500 °C results in a systematic decline in activity. For all pretreatments the 1 wt% Pd catalyst exhibits decreasing activity. For the 5 and 10 wt% Pd loadings, the non-calcined catalysts are more active than the 280 °C-calcined catalysts, which are more active than the 500 °C-calcined catalysts. For the 1 wt% Pd catalyst, the opposite is true. The catalyst activity improves as the Pd loading is increased.

Nanoparticles of indium oxide, tin oxide and indium oxide doped with tin oxide (ITO) have been prepared by Chemical Vapor Synthesis, CVS (a modified CVD process), starting with In- (tmhd)3 as precursor. A modification of the CVS process using a novel radio-frequency reaction zone has been developed in order to avoid the rapid decomposition of the nanocrystalline indium oxide particles at high temperatures. These oxides are candidates for applications as transparent conducting oxides, catalysts and gas sensors. Structural characterization by high resolution scanning and transmission electron microscopy and X-ray-diffraction has been used to determine the phase, grain size, grain size distribution and crystallinity of the nanoparticles. The specific surface area, and particle or agglomerate size of the powders have been measured by nitrogen sorption. Agglomerate sizes in aqueous dispersions have been determined by photon correlation spectroscopy. Zeta-potentials were measured. As well CVS powders exhibit a narrow size distribution with an average size of about 5 nm.

The catalytic activity of polycrystalline and nanocrystalline CeO2-supported Pd (Pd/pCeO2 and Pd/nCeO2) has been determined as a function of temperature and Pd loading. While the untreated nCeO2 support gives 50% methane conversion at 420°C, the untreated pCeO2 support exhibits little activity under the conditions examined due to its low surface area. A Pd loading of 5 wt% increases the activity of pCeO2 to 50% conversion at 260°C, while a 40 wt% Pd loading on nCeO2 exhibits a relatively smaller activity increase, yielding 50% conversion at 240°C. On a mass basis the 40 wt% Pd/nCeO2 catalyst is the most active tested in this study, but it is less active than the 5 wt% Pd/pCeO2 catalyst on a surface-area basis. Furthermore, the activity of the 40 wt% Pd/nCeO2 catalyst does not decrease during 100 hrs of exposure to CH4 and O2 at 250°C.

X-ray photoelectron spectroscopy (XPS) and ion scattering spectroscopy (ISS) have been used to characterize the surfaces of both bare supports and Pd-containing catalysts before and after exposure to reactor conditions. The XPS results reveal that the Pd surface concentration is more than an order of magnitude higher for 5 wt% Pd/pCeO2 than for 5 wt% Pd/nCeO2 due to the larger surface area of nCeO2 and that the 40 wt% Pd/nCeO2 catalyst has a lower Pd loading on a surface-area basis than the 5 wt% Pd/pCeO2 catalyst. Most of the supported Pd is in the form of PdO, but higher PdO2/PdO ratios are observed for both CeO2 supports compared to Pd supported on ZrO2 or CO3O4. Furthermore, a significant amount of metallic Pd forms on Pd/nCeO2 but not on Pd/pCeO2 during reaction. The nanocrystalline and polycrystalline CeO2 behave differently chemically which is consistent with the fact that the nanocrystalline catalysts are less active on a surface-area basis. Accumulation of H20 on the Pd/pCeO2 surface during reaction is significant but not on the Pd/nCeO2 surface. This suggests that the rate limiting step may be H2O desorption on Pd/pCeO2 while for Pd on nCeO2 adsorption of methane appears to be the slow step. The ISS data indicate that the outermost atomic layer of Pd/nCeO2 consists mostly of O and C, which is not the case for Pd/pCeO2. Site blockage by these species may also contribute to the lower activity on a surface-area basis of Pd/nCeO2 compared to Pd/pCeO2.

Nanocrystalline and polycrystalline ZrO2, CeO2 and Mn3O4 without and with 5 wt% Pd have been tested for methane oxidation. The nanocrystalline catalysts perform better than the polycrystalline catalysts on a weight basis. Nanocrystalline (n)-CeO2 performs much better than n-ZrO2, and both perform much better than polycrystalline (P)-CeO2 and P-ZrO2. 5 wt% Pd/n-ZrO2 is the best catalyst tested, but 5 wt% Pd/n-CeO2 performs nearly as well. A 20 wt% Ag/p-ZrO2 and a 20 wt% Ag/n-ZrO2 catalyst were also tested. The Ag yields a significant improvement over the bare supports, but not as much so as Pd.

Studies of microstructure evolution as a function of sintering parameters are necessary to better control the microstructure of nanophase ceramic compacts during processing. Small-angle scattering provides a comprehensive probe of the statistically-representative microstructures present in nanophase ceramics. A complete characterization includes complementary density, electron microscopy, nitrogen desorption and x-ray diffraction measurements. Small-angleneutron and ultra-small-angle x-ray scattering have been used to determine the effects of different sintering temperatures, pressures and additives during sintering of nanophase zirconia compacts. The samples were of sufficient size and uniformity to permit absolute calibration of the scattering data, making it possible to confirm that scattering from the pore/grain interface dominates the total scattering cross-section. A quantitative microstructural model was developed for this system, resulting in the determination of specific pore surface area, total pore volume fraction, pore number size distribution and grain size as a function of sintering parameters.

Ion beam mixing (IM) was measured in homogeneous amorphous metallic alloys of Cu-Er and Ni-Ti as a function of temperature using tracer impurities, i.e., the so called “marker geometry”. In Cu-Er, a strong temperature dependence in IM was observed between 80 K and 373 K, indicating that radiation-enhanced diffusion mechanisms are operative in this metallic glass. Phase separation of the Cu-Er alloy was also observed under irradiation as Er segregated to the vacuum and SiO2 interfaces of the specimen. At low-temperatures, the amount of mixing in amorphous Ni-Ti is similar to that in pure Ni or Ti, but it is much greater in Cu-Er than in either Cu or Er.