Revisiting the limits of photon momentum based optical power measurement method, employing the case of multi-reflected laser beam. - In: Metrologia, ISSN 1681-7575, Bd. 58 (2021), 1, 015006, S. 1-13
In this work, we review the viability and precision of the photon-momentum-based optical power measurement method that employs an amplification effect caused by a multi-reflected laser beam trapped in an optical cavity. Measuring the total momentum transfer of the absorbed and re-emitted photons from a highly reflective surface (reflection of the laser beam from an optical mirror) as a force provides the possibility of measuring the optical power with direct traceability to SI units. Trial measurements were performed at two different metrology laboratories: the laboratory for mass/force at the Technical University of Ilmenau, and the clean room laser radiometry laboratory at PTB, with a portable force measurement setup consisting of two electromagnetic force compensation balances. We compared the results of the optical power measurements performed with the force measurement setup, via the photon-momentum-based method, with those performed using a calibrated reference standard detector traceable to PTB's primary standard for optical power, the cryogenic radiometer. The comparison was carried out for an optical power range between 1 W and 10 W at a wavelength of 532 nm, which corresponds to a force of approximately 2000 nN at the upper limit, yielding approximately 2.3% relative standard uncertainty in the case of 33 reflections. Thus, conflating the high-precision force metrology technique at μN to nN levels with the optical setup required to achieve specular multi-reflection configuration of the laser beam, where a macroscopic optical cavity with ultra-high reflective mirrors (>99.995%) can adjustably be suspended from the force sensors, depending on required geometry of reflections, we show that the uncertainty of the optical power measurements upon further increase of the nominally applied optical power, the number of laser beam reflections, or the reflectivity coefficient of the mirrors can be markedly reduced.
https://doi.org/10.1088/1681-7575/abc86e
Layer-by-layer polyelectrolyte assembly for the protection of GaP surfaces from photocorrosion. - In: ACS applied nano materials, ISSN 2574-0970, Bd. 4 (2021), 1, S. 425-431
Polyelectrolyte layer-by-layer assemblies are known as protective coatings for corrosion inhibition. Here, we demonstrate that polyelectrolyte multilayers of poly(ethyleneimine) (PEI) and poly(styrene sulfonate) (PSS)-(PEI/PSS)x-adsorbed at the GaP(100) photocathode surface remarkably mitigate the photocorrosion of GaP without decreasing its photoconversion efficiency. The activity of the polybase-polyacid complex is based on buffering pH changes at the solid-liquid interface. We carried out ab initio molecular dynamics-based simulations of the GaP(100) surface in contact with liquid water and demonstrated that an increase in the proton concentration enhances GaP dissolution. We used the scanning vibrating electrode technique (SVET) to characterize the distribution of photocorrosion activity areas over bare and polyelectrolyte-coated GaP surfaces and we showed that a polyelectrolyte coating impedes the dissolution kinetics. Data obtained using the SVET were compared to photoetched pores on the semiconductor surface. Voltammetric and chronoamperometric measurements were also performed to evaluate photoconversion efficiencies before and after the application of the protective coatings.
https://doi.org/10.1021/acsanm.0c02768
Electrocatalysis of lithium (poly-) sulfides in organic ether-based electrolytes. - In: Journal of the Electrochemical Society, ISSN 1945-7111, Bd. 167 (2021), 16, 166520, insges. 9 S.
https://doi.org/10.1149/1945-7111/abd60c
Method for contact resistance determination of copper during fast temperature changes. - In: Journal of materials science, ISSN 1573-4803, Bd. 56 (2021), 5, S. 3827-3845
https://doi.org/10.1007/s10853-020-05490-w
Formation of CuCrCoFeNiO high entropy alloy thin films by rapid thermal processing of Cu/CrNiO/FeCo multilayers. - In: Surface and coatings technology, ISSN 1879-3347, Bd. 405 (2021), 126563
https://doi.org/10.1016/j.surfcoat.2020.126563
Radius and roundness measurement of micro spheres based on a set of AFM surface scans. - In: Measurement science and technology, ISSN 1361-6501, Bd. 32 (2021), 4, 044005, S. 1-11
Micro coordinate measuring machines have been developed for the traceable characterisation of small complex parts, due to the demand in research and industry. These machines require geometrically well characterised probing spheres of ever smaller radii. Currently, there is no established procedure for the measurement of such spheres below radii of 500 [my]m. In this paper we, therefore, propose and investigate an approach which is based on a set of AFM surface scans in conjunction with a stitching algorithm. The strategy was implemented on a nano measuring machine and investigated on a ruby sphere with a radius of 150 [my]m. Although the strategy can generally be applied to the characterisation of a full sphere, we limit ourselves to the measurement of one greate circle (equator). The technique enables the measurement of micro spheres with a high lateral and vertical resolution. The mean radius of the ruby sphere was measured with a standard deviation of 3.7 nm over 6 repetitions. As our experiments have shown, the measurement procedure is at the moment mainly influenced by the shape of the AFM tip which requires further attention.
https://doi.org/10.1088/1361-6501/abcff4
Influence of different Ni coatings on the long-term behavior of ultrasonic welded EN AW 1370 cable/EN CW 004A arrestor dissimilar joints. - In: Welding in the world, ISSN 1878-6669, Bd. 65 (2021), 3, S. 429-440
The increasing demand for energy-efficient vehicles requires suitable methods for cost and weight reduction. This can be achieved by the replacement of copper by aluminum, in particular for the on-board power systems. However, the complete substitution is restricted by the mechanical and physical material properties of aluminum as well as challenges in the aluminum copper interface. The challenges concern the corrosion vulnerability and the occurrence of brittle intermetallic compounds (IMC) which can negatively influence the mechanical properties and the electrical conductivity. Therefore, current investigations focus on the one hand on the realization of dissimilar aluminum copper joints by suitable joining technologies, like ultrasonic welding, and on the other hand on the assurance of a sufficient prevention against harmful corrosion effects. In cases where the joint cannot be protected against corrosion by sealing, nickel coatings can be used to protect the joint. In the present study, the influence of electroless, electroplated, and sulfamate nickel coatings was investigated regarding the long-term stability. The joints were performed as industry-related arrester connections, consisting of EN AW 1370 cables and EN CW 004A terminals. The samples were exposed to corrosive as well as electrical, thermal, and mechanical stress tests according to current standards and regulations.
https://doi.org/10.1007/s40194-020-01030-x
Ni-Cu-Zn ferrites with high Curie temperature for multilayer inductors with increased operating temperatures. - In: International journal of applied ceramic technology, ISSN 1744-7402, Bd. 18 (2021), 1, S. 129-137
https://doi.org/10.1111/ijac.13623
Electrocodeposition of Ni composites and surface treatment of SiC nano-particles. - In: Surface and coatings technology, ISSN 1879-3347, Bd. 406 (2021), 126663, insges. 8 S.
https://doi.org/10.1016/j.surfcoat.2020.126663
Determination of transport parameters in [EMIm]Cl-based ionic liquids - diffusion and electrical conductivity. - In: Electrochimica acta, ISSN 1873-3859, Bd. 366 (2021), 137370
The density, electrical conductivity and diffusion coefficients of anions and cations in the ionic liquid AlCl3/1-ethyl-3-methylimidazolium chloride, [EMIm]Cl, were determined to study physical correlations of these important parameters. The density was measured for different molar ratios of AlCl3:[EMIm]Cl from 0.5:1 to 2.0:1 at ambient temperature. The diffusion coefficient of the electrochemically active heptachloroaluminate complex, Al2Cl7-, was measured for a molar ratio of 2:1 in the range of 25˚C to 100˚C. The corresponding current density and potential transients were discussed regarding the decomposition of the [EMIm]+ cation and deviation from the theoretical Cottrell behavior. The electrical conductivity was measured for molar ratios of 1.5:1 and 2:1 in the range of 25˚C to 100˚C. Both the diffusion coefficient and electrical conductivity can be described well by an Arrhenius law. The diffusion coefficients of AlCl4-, Al2Cl7- and [EMIm]+ were estimated from the Nernst-Einstein and Stokes-Einstein relation. The results indicate a strong impact of ion pairing in these electrolytes.
https://doi.org/10.1016/j.electacta.2020.137370