Nanostructured Ge and GeSn Films by High-pressure He Plasma Sputtering for High-capacity Li ion Battery Anodes

We fabricated nanostructured Ge and GeSn films in He radio-frequency magnetron plasma sputtering deposition. Monodisperse amorphous Ge and GeSn nanoparticles of 30-40 nm in size were orderly arranged without aggregation by off-axis sputtering deposition in high He-gas-pressure range of 0.1 Torr. The Ge film porosity was over 30%. We tested the charge/discharge cycle performance of Li-ion batteries with nanostructured Ge and GeSn anodes. The Ge anode with an ordered arrangement of nanoparticles showed Li-storage capacity of 565 mAh/g after the 60th. The capacity retention was markedly improved by the addition of 3at% Sn in Ge anode. GeSn anode (3at% Sn) achieved a higher capacity of 1,128 mAh/g after 60th cycles with 92% capacity retention. Precise control of the nano-morphology and electrical characteristics by a single step procedure using low temperature plasma is effective for stable cycling of high-capacity Ge anodes.

Engineering polymer film porosity for solvent triggered actuation

A novel approach for the fabrication of porous polymer films and their self-folding behavior in response to water is investigated.

Thickness Optimization of Highly Porous Flame-Aerosol Deposited WO3 Films for NO2 Sensing at ppb

Nitrogen dioxide (NO2) is a major air pollutant resulting in respiratory problems, from wheezing, coughing, to even asthma. Low-cost sensors based on WO3 nanoparticles are promising due to their distinct selectivity to detect NO2 at the ppb level. Here, we revealed that controlling the thickness of highly porous (97%) WO3 films between 0.5 and 12.3 μm altered the NO2 sensitivity by more than an order of magnitude. Therefore, films of WO3 nanoparticles (20 nm in diameter by N2 adsorption) with mixed γ- and ε-phase were deposited by single-step flame spray pyrolysis without affecting crystal size, phase composition, and film porosity. That way, sensitivity and selectivity effects were associated unambiguously to thickness, which was not possible yet with other sensor fabrication methods. At the optimum thickness (3.1 μm) and 125 °C, NO2 concentrations were detected down to 3 ppb at 50% relative humidity (RH), and outstanding NO2 selectivity to CO, methanol, ethanol, NH3 (all > 105), H2, CH4, acetone (all > 104), formaldehyde (>103), and H2S (835) was achieved. Such thickness-optimized and porous WO3 films have strong potential for integration into low-power devices for distributed NO2 air quality monitoring.

Porous Polymer Based Flexible Pressure Sensors for Medical Applications

This paper focuses on the use of microporous PDMS foams as a highly deformable film to improve the sensitivity of flexible capacitive pressure sensor dedicated to wearable use. A fabrication process allowing the mechanical properties of foams to be adjusted is proposed together with a non-linear behavioral model used to objectively estimate the sensor performances in terms of sensitivity and measurement range. Sensors fabricated and characterized in this study show that the sensitivity and the measurement range can be adjusted from 0.14%/kPa up to 13.07%/kPa, and from 594 kPa to 183 kPa, respectively, while the PDMS film porosity ranges from 0% up to 85%.

Morphological and Raman Study of an Anodized Tio2 Nanotubular Matrix without Presence of Nanograss, Using Graphite as Cathode

One set of TiO2 nanotubes is anodized to identify and study the time lapse of a matrix of them without presence of nanograss as a residual layer. The anodization process consists of an organic media of ethylene glycol and NH4 F salts, constant voltage for a time period from 10 to 60 minutes. All anodized samples are rinsed and annealed to 400 °C by 2 hours to obtain an anatase crystalline structure. The morphological characterization was carried out by Field Emission Scanning Electron Microscopy to verify the presence of the nanotubes and calculate the surface roughness factor and film porosity. It was observed that roughness factor and porosity doesn’t have important variations, as time function, except for 60 minutes where nanograss has a strong presence and the gaps between nanotubes are minimal. Raman Spectroscopy was used for optical characterization in order to identify the changes in signal intensity and Eg mode Shift associated with anodization time. It was observed that intensity suffers an increment and Eg mode Shift suffers a decrement as thickness function (anodization time).

Multimode Sensor of Fluids Based on Porous Film

Multimode interferometers are coming of age both as sensors and components of quantum circuits.Here we investigate an interferometer based on a porous thinfilm sensor of refractive index of fluids. Eigenmode analysis is used to identify effective single- and multi-mode sensing regimes and the corresponding realizations of interferometer. A general measure in a form of Fisher information is introduced to describe the impact of the film porosity on sensitivity and nonlinearity of the interferometer. As high sensitivity relies on formation of a highly peaked mode in the film, a parallel with plasmonic sensors is drawn. Close correlations between the sensor nonlinearity, mode profile and the shape of Fisher information function indicate the potential of this measure in describing complex non-Gaussian multimode structures

Mechanistic Study of FAC Processes Focused on the Oxide Layer Properties

Detailed FAC processes and effects of local H2 partial pressure, oxide film porosity, and Cr content on the enhancement of dissolution through the oxide layer have been discussed focused on the result of FAC experiments and oxide layer characterizations. Porosity of oxide layer is closely related to corrosion resistance of the steels even in Cr content range of 0.003 to 1.01 wt %. Compact inner oxide layer suppress the diffusion of oxidizer (H2O) and Fe ion via pores, on the other hand, liquid-state diffusion through a porous oxide layer is considered to be dominant under high FAC rate conditions. The model of spiral enhancement of dissolution through the oxide layer has been proposed. It has been considered that FAC is enhanced with increase of local H2 partial pressure and film porosity. It has also been suggested that low solubility Fe-Cr spinel-type oxide formed on the high Cr content steels suppresses the spiral enhancement of dissolution through the oxide layer.