A model revealing grain boundary arrangement-dominated fatigue cracking behavior in nanoscale metallic multilayers. - In: MRS communications, ISSN 2159-6867, Bd. 9 (2019), 3, S. 936-940
In order to reveal the quantitative relationship between fatigue crack deflection path and cross-sectional grain boundary (GB) arrangement of metallic nanolayered composites (NLCs), a stochastic model was established based on the interface-dominant fatigue damage for the ultrafine-scale NLCs. The model indicates that the crack deflection length decreases with decreasing GB arrangement deviation and grain size of constituent layers. The observation and quantitative analysis of fatigue cracking behavior of the Cu/W multilayers with a layer thickness of 5 and 20 nm was conducted to verify the model.
https://doi.org/10.1557/mrc.2019.75
N-doped TiO2 with a disordered surface layer fabricated via plasma treatment as an anode with clearly enhanced performance for rechargeable sodium ion batteries. - In: Sustainable energy & fuels, ISSN 2398-4902, Bd. 3 (2019), 10, S. 2688-2696
Im Titel ist "2" tiefgestellt
https://doi.org/10.1039/C9SE00350A
A fast start up system for microfluidic direct methanol fuel cells. - In: International journal of hydrogen energy, ISSN 1879-3487, Bd. 44 (2019), 48, S. 26517-26529
A novel simple and effective heating system for microfluidic direct methanol fuel cells was characterized experimentally. It consisted of a semi-conductive indium tin oxide heating layer of nanometer thickness that was applied to the anode and cathode cover plates and subjected to high electrical power. Within only 25 s, temperatures of up to 80˚C were reached in the vicinity of the membrane, which was verified experimentally. With this system the time needed to generate more than 90 of the maximum output power of the fuel cell can be reduced to 20 s, thus overcoming the well known problem of long start up times in the order of minutes of this type of fuel cells. Furthermore, deeper insight into the role of the convective heat transfer is given. For the first time simultaneous measurements of the three-dimensional velocity and temperature distributions within the anode channel of a microfluidic direct methanol fuel cell were performed by means of luminescence lifetime imaging and astigmatism particle tracking velocimetry. The experimental results prove a significant cooling effect of the anode flow, whereas the influence of the cathode flow is small. Finally, various possible future improvements to increase the efficiency of the heating system are identified.
https://doi.org/10.1016/j.ijhydene.2019.08.107
On the application of a supercontinuum white light laser for simultaneous measurements of temperature and velocity fields using thermochromic liquid crystals. - In: Experimental thermal and fluid science, Volume 109 (2019), 109914, Seite 1-13
Simultaneous velocity and temperature measurements using thermochromic liquid crystals (TLC) as tracer particles are discussed, with regard to measuring range, uncertainty and spatial resolution. For the first time, a supercontinuum laser is used to illuminate these particles, which shall later be used for the characterization of the momentum and heat transfer in Rayleigh-Bénard cells with high aspect ratio using particle image velocimetry (PIV) and particle image thermometry (PIT). Light scattered from the TLCs is analyzed by spectrometer measurements, revealing its general scattering characteristics depending on the angle between the light sheet plane and the viewing axis. It is shown that white light sources with continuous spectral characteristic and a slightly higher fraction of light in the red wavelength range perform well, thereby the supercontinuum white light laser can be used, even though it has a cut-in wavelength of about 475 nm. The numerical aperture of the detection optics and chromatic aberrations of the laser light significantly affect the temperature sensitivity and dynamic range of the color of the TLCs. This may cause an effective temperature sensitivity range of about one-tenth of their nominal range, particularly at large angles between light sheet plane and viewing axis, as usually applied in PIV. A simultaneous velocity and temperature measurement in a Rayleigh-Bénard cell experimentally validates that the use of the supercontinuum laser allows for reliable simultaneous PIV and PIT measurements with high spatial resolution of less than 500 [my]m in out-of-plane direction, on condition that an appropriate two-dimensional calibration is applied.
https://doi.org/10.1016/j.expthermflusci.2019.109914
A hyperfine look at titanium dioxide. - In: AIP Advances, ISSN 2158-3226, Bd. 9 (2019), 8, 085208, insges. 5 S.
https://doi.org/10.1063/1.5097459
Modulation of adaptive cognitive control by prefrontal high-definition transcranial direct current stimulation in older adults. - In: The journals of gerontology, ISSN 1758-5368, Bd. 74 (2019), 7, S. 1174-1183
https://doi.org/10.1093/geronb/gbz048
Fundamental mechanisms with reactive infiltration of silicon melt into carbon capillaries. - In: Advanced engineering materials, ISSN 1527-2648, Volume 21 (2019), issue 8, 1900184, Seite 1-11
https://doi.org/10.1002/adem.201900184
Passive control of the concentration boundary layer in microfluidic fuel cells using Dean vortices. - In: Microfluidics and nanofluidics, ISSN 1613-4990, Bd. 23 (2019), 9, 110, S. 1-11
https://doi.org/10.1007/s10404-019-2274-2
MEMS-based RF oscillators using SiCer technology. - In: IEEE microwave magazine, Bd. 20 (2019), 10, S. 71-85
https://doi.org/10.1109/MMM.2019.2928678
RF MEMS modules. - In: IEEE microwave magazine, Bd. 20 (2019), 10, S. 44-55
https://doi.org/10.1109/MMM.2019.2928676