Low-temperature photoluminescence investigation of light-induced degradation in boron-doped CZ silicon. - In: Physica status solidi, ISSN 1862-6319, Bd. 219 (2022), 17, 2200180, S. 1-9
Light-induced degradation (LID) in boron-doped Czochralski grown (CZ) silicon is a severe problem for silicon devices such as solar cells or radiation detectors. Herein, boron-doped CZ silicon is investigated by low-temperature photoluminescence (LTPL) spectroscopy. An LID-related photoluminescence peak is already found while analyzing indium-doped p-type silicon samples and is associated with the ASi-Sii defect model. Herein, it is investigated whether a similar peak is present in the spectra of boron-doped p-type CZ silicon samples. The presence of change in the photoluminescence signal intensity due to activation of the boron defect is investigated as well. Numerous measurements on boron-doped samples are made. For this purpose, samples with four different boron doping concentrations are analyzed. The treatments for activation of the boron defect are based on the LID cycle. During an LID cycle, an additional peak or shoulder neither in the areas of the boron-bound exciton transverse acoustic and nonphonon-assisted peaks (BTA, BNP) nor in the area of the boron-bound exciton transverse optical phonon-assisted peak (BTO) is found. The defect formation also does not lead to a lower photoluminescence (PL) intensity ratio BTO(BE)/ITO(FE).
https://doi.org/10.1002/pssa.202200180
Mathematical analysis of a low cost mechanical ventilator respiratory dynamics enhanced by a sensor transducer (ST) based in nanostructures of Anodic Aluminium Oxide (AAO). - In: Mathematics, ISSN 2227-7390, Bd. 10 (2022), 14, 2403, S. 1-32
Mechanical ventilation systems require a device for measuring the air flow provided to a patient in order to monitor and ensure the correct quantity of air proportionated to the patient, this device is the air flow sensor. At the beginning of the COVID-19 pandemic, flow sensors were not available in Peru because of the international supply shortage. In this context, a novel air flow sensor based on an orifice plate and an intelligent transducer was developed to form an integrated device. The proposed design was focused on simple manufacturing requirements for mass production in a developing country. CAD and CAE techniques were used in the design stage, and a mathematical model of the device was proposed and calibrated experimentally for the measured data transduction. The device was tested in its real working conditions and was therefore implemented in a breathing circuit connected to a low-cost mechanical ventilation system. Results indicate that the designed air flow sensor/transducer is a low-cost complete medical device for mechanical ventilators that is able to provide all the ventilation parameters by an equivalent electrical signal to directly display the following factors: air flow, pressure and volume over time. The evaluation of the designed sensor transducer was performed according to sundry transducer parameters such as geometrical parameters, material parameters and adaptive coefficients in the main transduction algorithm; in effect, the variety of the described results were achieved by the faster response time and robustness proportionated by transducers of nanostructures based on Anodic Aluminum Oxide (AAO), which enhanced the designed sensor/transducer (ST) during operation in intricate geographic places, such as the Andes mountains of Peru.
https://doi.org/10.3390/math10142403
Multifunctional water-organic hybrid electrolyte for rechargeable zinc ions batteries. - In: The chemical engineering journal, ISSN 1873-3212, Bd. 450 (2022), 3, 138265
Uncontrollable dendrite growth and parasitic reactions are the fundamental obstacles to achieve large-scale application of aqueous Zn-ion batteries. Herein, a new strategy of tuning the electrolyte solvation structure and electrode interface is demonstrated for highly reversible zinc plating/stripping. Acetonitrile (AN) is introduced into Zn(OTf)2 electrolyte as co-solvent, the interaction between Zn2+ and acetonitrile attenuates the Zn2+ solvation and water activity. Concomitantly, theoretical calculations demonstrate that acetonitrile molecules tend to adsorb on the surface of zinc electrode to form an adaptive zinc-electrolyte interface. Such an electrolyte engineering significantly prevents water hydrogen evolution, suppresses vanadium dissolution and modulates Zn deposition behavior. As proof of concept, Zn//Zn symmetric cells with acetonitrile additive exhibit a ultra-long cycling of 2100 h at a high current density of 5 mA cm^-2. In particular, the university of the acetonitrile-water co-solvent (AWCS) electrolyte is demonstrated, multiple battery systems (Zn//Al-V-O, Zn//Zn-V-O, Zn//VOOH, and Zn//Mn-V-O) deliver markedly improved cycling stability and rate performance. The mechanism of action of AWCS electrolyte on performance indicators is discussed in detail, which provides a promising insight for energy storage devices.
https://doi.org/10.1016/j.cej.2022.138265
Ellipsometry and polarimetry - classical measurement techniques with always new developments, concepts, and applications. - In: Advanced Optical Technologies, ISSN 2192-8584, Bd. 11 (2022), 3/4, S. 57-58
https://doi.org/10.1515/aot-2022-0025
Modified polydopamine derivatives as high-performance organic anodes for potassium-ion batteries. - In: Sustainable energy & fuels, ISSN 2398-4902, Bd. 6 (2022), 15, S. 3527-3535
Polydopamine (PDA) as a carbon source and a versatile coating material has been widely studied in rechargeable battery electrodes. However, it is rare to directly utilize PDA as an organic anode for ion storage, especially in potassium-ion batteries (PIBs). In this work, modified PDA (MPDA-350) with a porous structure is synthesized by collective methods of template-assisted and low-temperature pyrolysis, which endows PDA with large ion diffusion tunnels and increased active sites for K+ ion storage. Moreover, contrast experiments demonstrate that the annealing process with an appropriate temperature can increase the content and activity of electroactive groups in MPDA-350. The prepared MPDA-350 is first applied to PIBs that deliver high reversible capacity (384.9 mA h g^-1 at 100 mA g^-1) and very stable cyclability (99.94% capacity retention after 500 cycles). This work provides a new insight for the expansion of high-performance organic anodes for PIBs.
https://doi.org/10.1039/D2SE00684G
Fabrication of long-life quasi-solid-state Na-CO2 battery by formation of Na2C2O4 discharge product. - In: Cell reports, ISSN 2666-3864, Bd. 3 (2022), 7, 100973, S. 1-15
Rechargeable Na-CO2 batteries are promising energy-storage devices due to their high energy density, environmental friendliness, and cost effectiveness. However, the insulating nature and irreversibility of the Na2CO3 discharge product cause large polarization and poor cyclicity. Here, we report a reversible quasi-solid-state Na-CO2 battery that is constructed by the synergistic action of a Co-encapsulated N-doped carbon framework catalyst and gel electrolyte to ensure the formation of a highly reversible Na2C2O4 discharge product. Experiments and density functional theory calculations indicate that the electron-agglomeration effect of Co nanoparticles enhances CO2 adsorption and lowers energy barrier, as well as promotes Na2C2O4 generation. A gel electrolyte containing an imidazole organic cation is used to inhibit the decomposition of the thermodynamically unstable Na2C2O4. The fabricated Na-CO2 battery exhibits a high discharge capacity of 3,094 mAh g^-1, a high-rate performance of 1,777 mAh g^-1 at a current density of 0.5 mA cm^-2, and excellent cycling performance of 366 cycles (2,200 h).
https://doi.org/10.1016/j.xcrp.2022.100973
Synthesis of CoSe2 reinforced nitrogen-doped carbon composites as advanced anodes for potassium-ion batteries. - In: Inorganic chemistry frontiers, ISSN 2052-1553, Bd. 9 (2022), 15, S. 3719-3727
Potassium-ion batteries (PIBs) are considered potential candidates for large-scale energy storage applications with cost superiority. However, the development of PIBs is severely restricted by the sluggish electrochemical kinetics and severe volume expansion of anode materials. Herein, CoSe2 reinforced nitrogen-doped carbon composites (CoSe2C) are synthesized via a simple solution-based etching-coating method and further studied as high-performance anodes for PIBs. Electrochemical characterization studies indicate that the potassium storage performance of CoSe2@C composite anodes relies on the initial mass ratio of CoSe2 nanosheets and carbon precursors (that is dopamine hydrochloride) during the synthesis process. In the case of the mass ratio of CoSe2 nanosheets and dopamine hydrochloride being 1 : 1, the as-obtained CoSe2@C-1 : 1 anode exhibits a high reversible capacity (366.1 mA h g^-1 at 0.1 A g^-1 after 100 cycles), an excellent long-cycle stability (237.6 mA h g^-1 at 1.0 A g^-1 after 1000 cycles), and a good rate capability (281.5 mA h g^-1 at 5.0 A g^-1). The optimum performance of CoSe2@C-1 : 1 as a PIB anode in terms of cycling stability and kinetics is attributed to the uniform distribution of CoSe2 nanoparticles inside the carbon matrix.
https://doi.org/10.1039/D2QI00848C
The 2022 solar fuels roadmap. - In: Journal of physics, ISSN 1361-6463, Bd. 55 (2022), 32, 323003, S. 1-52
Renewable fuel generation is essential for a low carbon footprint economy. Thus, over the last five decades, a significant effort has been dedicated towards increasing the performance of solar fuels generating devices. Specifically, the solar to hydrogen efficiency of photoelectrochemical cells has progressed steadily towards its fundamental limit, and the faradaic efficiency towards valuable products in CO2 reduction systems has increased dramatically. However, there are still numerous scientific and engineering challenges that must be overcame in order to turn solar fuels into a viable technology. At the electrode and device level, the conversion efficiency, stability and products selectivity must be increased significantly. Meanwhile, these performance metrics must be maintained when scaling up devices and systems while maintaining an acceptable cost and carbon footprint. This roadmap surveys different aspects of this endeavor: system benchmarking, device scaling, various approaches for photoelectrodes design, materials discovery, and catalysis. Each of the sections in the roadmap focuses on a single topic, discussing the state of the art, the key challenges and advancements required to meet them. The roadmap can be used as a guide for researchers and funding agencies highlighting the most pressing needs of the field.
https://doi.org/10.1088/1361-6463/ac6f97
Anisotropy of the ΔE effect in Ni-based magnetoelectric cantilevers: a finite element method analysis. - In: Sensors, ISSN 1424-8220, Bd. 22 (2022), 13, 4958, S. 1-16
In recent investigations of magnetoelectric sensors based on microelectromechanical cantilevers made of TiN/AlN/Ni, a complex eigenfrequency behavior arising from the anisotropic ΔE effect was demonstrated. Within this work, a FEM simulation model based on this material system is presented to allow an investigation of the vibrational properties of cantilever-based sensors derived from magnetocrystalline anisotropy while avoiding other anisotropic contributions. Using the magnetocrystalline ΔE effect, a magnetic hardening of Nickel is demonstrated for the (110) as well as the (111) orientation. The sensitivity is extracted from the field-dependent eigenfrequency curves. It is found, that the transitions of the individual magnetic domain states in the magnetization process are the dominant influencing factor on the sensitivity for all crystal orientations. It is shown, that Nickel layers in the sensor aligned along the medium or hard axis yield a higher sensitivity than layers along the easy axis. The peak sensitivity was determined to 41.3 T−1 for (110) in-plane-oriented Nickel at a magnetic bias flux of 1.78 mT. The results achieved by FEM simulations are compared to the results calculated by the Euler-Bernoulli theory.
https://doi.org/10.3390/s22134958
The deuteron NMR Hahn echo decay in polyethylene oxide melts. - In: AIP Advances, ISSN 2158-3226, Bd. 12 (2022), 7, S. 075219-1-075219-12
The deuteron transverse relaxation properties of polyethylene oxide melts of four different molecular weights, covering the range from the onset of entanglements to the regime of fully entangled chains, are investigated using Hahn echo decays over an extensive time interval up to ten times the effective transverse spin relaxation time. The results are compared to predictions based on the Rouse and reptation formalisms, taking into account the dynamical heterogeneity of linear polymer chains produced by the end segments. The experimental results can be described qualitatively by a combination of both models, with the contribution of reptation dynamics increasing with growing chain length. The transition is continuous, rather than being characterized by sharp regime boundaries. Up to a molecular weight of 300.000 g/mol, the predicted limit of pure reptation dynamics is not yet reached. Quantitative deviations from the predicted decays as computed by numerical procedures become observable toward the long-time limit of the Hahn echo decays and are being discussed in terms of shortcomings of the available reptation theories.
https://doi.org/10.1063/5.0099293