2022 - Repozytorium publikacji - Politechnika Gdańska

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The valance state of vanadium-key factor in the flexibility of potassium vanadates structure as cathode materials in Li-ion batteries
- M. Prześniak-Welenc
- Małgorzata Nadolska-Dawidowska
- Kacper Jurak
- J. Li
- K. Górnicka
- A. Mielewczyk-Gryń
- M. Rutkowska
- A. P. Nowak
2022 Pełny tekst Scientific Reports
Potassium hexavanadate (K2V6O16·nH2O) nanobelts have been synthesized by the LPE-IonEx method, which is dedicated to synthesis of transition metal oxide bronzes with controlled morphology and structure. The electrochemical performance of K2V6O16·nH2O as a cathode material for lithium-ion batteries has been evaluated. The KVO nanobelts demonstrated a high discharge capacity of 260 mAh g−1, and long-term cyclic stability up to 100 cycles at 1 A g−1. The effect of the vanadium valence state and unusual construction of the nanobelts, composed of crystalline and amorphous domains arranged alternately were also discussed in this work. The ex-situ measurements of discharged electrode materials by XRD, MP-AES, XAS and XPS show that during the subsequent charge/discharge cycle the potassium in the K2V6O16·nH2O structure are replacing by lithium. The structural stability of the potassium hexavandate during cycling depends on the initial vanadium valence state on the sample surface and the presence of the “fringe free” domains in the K2V6O16·nH2O nanobelts.
The vibration-based assessment of the influence of elevated temperature on the condition of concrete beams with pultruded GFRP reinforcement
- Beata Zima
- Marcin Krajewski
2022 Pełny tekst COMPOSITE STRUCTURES
Concrete beams reinforced with glass fiber reinforced polymer (GFRP) bars subjected to elevated temperature have been experimentally studied. The influence of high temperatures on GFRP-reinforced concrete beams condition has been check both, destructively and nondestructively. The nondestructive tests foresaw vibration-based tests to obtain the natural frequency values after exposure to varying temperatures. The vibration-based tests allowed for the indirect observation of beams stiffness reduction after exposure to elevated temperature. The approach based on frequency response function (FRF) turned out to be efficient even in the case of relatively low temperatures (120⁰C). The investigation involved also destructive tests which were conducted in various conditions: once the bending load and elevated temperature were applied at the same time and in the next case, the destructive tests were conducted after heating and cooling down the experimental objects. The study proved that the increase of the temperature causes the reduction of characteristic mechanical parameters, regardless the beams were cooled down or not. However, the simultaneous action of bending load and elevated temperature resulted in a greater reduction of the ultimate strength of tested objects.
The Way One Defines Specification Matters: On the Performance Criteria for Efficient Antenna Optimization in Aggregated Bi-Objective Setups
- Adrian Bekasiewicz
- Michał Czyż
2022 Pełny tekst
Design of antenna structures for real-world applications is a challenging task that often involves addressing multiple design requirements at a time. Popular solution approaches to this class of problems include utilization of composite objectives. Although configuration of such functions has a significant effect on the cost and performance of the optimization, their specific structure is normally determined based on engineering experience and does not involve auxiliary investigations oriented towards adjustment of process efficiency. In this work, the effects of used functions and their composition on performance and cost of the bi-objective optimization process are investigated. The balance between the requirements is tailored to the problem at hand based on visual inspection of functional landscapes. The analyses are performed on a case study basis using a planar, multi-parameter antenna optimized for minimization of footprint and reflection within the 3.1 GHz to 10.6 GHz range. The numerical results show significant differences between the performance of the obtained solutions, as well as the computational cost of the optimization. The best geometry found using one of the considered objective functions is characterized by an in-band reflection of –9.6 dB and the footprint of only 171 mm2.
Theoretical designing of selenium heterocyclic non-fullerene acceptors with enhanced power conversion efficiency for organic solar cells: a DFT/TD-DFT-based prediction and understanding
- Muhammad Khan
- Hameed Haq
- Saira Abbasi
- Shan E Zehra Syeda
- Muhammad Arshad
2022 JOURNAL OF MOLECULAR MODELING
In this study, we have designed and explored a new series of non-fullerene acceptors for possible applications in organic solar cells. We have designed four molecules named as APH1 to APH4 after end-capped modification of recently synthesized Y6-Se-4Cl molecule. Density functional theory and time dependent-density functional theory have been employed for computing geometric and photovoltaic parameters of the designed molecules. Designed molecules have displayed high values of fill factor and FF%. Further, high mobility of electrons and holes between metal electrodes are also noted for designed molecules. Good values of open circuit voltage enhance the power conversion efficiency in the APH1–APH4. Frontier molecular orbitals analysis and excitation energy values suggested easy transportation of charges between molecular orbitals. Moreover, red-shifting in the absorption spectrum with high oscillating strength is also noted in APH1 to APH4 as compared to reference molecules. Results of different opto-electronic and photovoltaic parameters recommended that APH1 to APH4 are effective contributors for the development of high performance organic solar cells.
Theoretical examination of the fracture behavior of BC3 polycrystalline nanosheets: Effect of crack size and temperature
- Ali Dadrasi
- Alireza Albooyeh
- Sasan Fooladpanjeh
- Azam Salmankhani
- Amin Hamed Mashhadzadeh
- Mohammad Saeb
2022 INTERNATIONAL JOURNAL OF BIOLOGICAL MACROMOLECULES
2D carbon graphene nanostructures are elements of advanced materials and systems. This theoretical survey provides explanation to the mechanical and fracture behavior of mono- and polycrystalline BC3 nanosheets (denoted as MC- and PCBC3NS, respectively) as a function of temperature and the type of crack defects. The mechanical performance of PCBC3NS at elevated temperatures was monitored varying the number of grain boundaries (the main source of stress concentration) by considering structural defects forming during the crystal growth. Molecular dynamics (MD) simulation was applied as a cost-effective technique to model and test MC- and PCBC3NS by selecting the proper potential function and boundary conditions. The results demonstrated that the mechanical properties of the perfect crystalline PCBC3NS was decreased by increase of the number of grains, particularly when the grain numbers were equal to or more than 36. For defective PCBC3NS, the mechanical properties were decreased by the crack length and the temperature. The lowest values of the Young's modulus, failure stress, and failure strain were assigned to the PCBC3NS having the crack length of L/2 at 1000 K, respectively by 23%, 46%, and 33% lower than the corresponding defect-free PCBC3NS. The crack tip played a key role in failure behavior, even more that the number of grain boundaries. Eventually, the critical stress intensity was decreased gradually by increasing the temperature. The results of this work can be generalized to more complicated cases to deepen understanding and predict fracture fingerprint of the next generations of 2D nanostructures.
Thermal buckling of functionally graded piezomagnetic micro- and nanobeams presenting the flexomagnetic effect
- Mohammad Malikan
- Tomasz Wiczenbach
- Victor Eremeev
2022 Pełny tekst CONTINUUM MECHANICS AND THERMODYNAMICS
Galerkin weighted residual method (GWRM) is applied and implemented to address the axial stability and bifurcation point of a functionally graded piezomagnetic structure containing flexomagneticity in a thermal environment. The continuum specimen involves an exponential mass distributed in a heterogeneous media with a constant square cross section. The physical neutral plane is investigated to postulate functionally graded material (FGM) close to reality. Mathematical formulations concern the Timoshenko shear deformation theory. Small scale and atomic interactions are shaped as maintained by the nonlocal strain gradient elasticity approach. Since there is no bifurcation point for FGMs, whenever both boundary conditions are rotational and the neutral surface does not match the mid-plane, the clamp configuration is examined only. The fourth-order ordinary differential stability equations will be converted into the sets of algebraic ones utilizing the GWRM whose accuracy was proved before. After that, by simply solving the achieved polynomial constitutive relation, the parametric study can be started due to various predominant and overriding factors. It was found that the flexomagneticity is further visible if the ferric nanobeam is constructed by FGM technology. In addition to this, shear deformations are also efficacious to make the FM detectable.
Thermal cooling process by nanofluid flowing near stagnating point of expanding surface under induced magnetism force: A computational case study
- Faisal Shahzad
- Wasim Jamshed
- Amjad Ali Pasha
- Rabia Safdar
- Md. Mottahir Alam
- Misbah Arshad
- Syed M. Hussain
- Muhammad Bilal Hafeez
- Marek Krawczuk
2022 Pełny tekst Case Studies in Thermal Engineering
This paper is dedicated to the exam of entropy age and research of the effect of mixing nanosolid additives over an extending sheet. In this review, Newtonian nanofluid version turned into researched at the actuated appealing field, heat radiation and variable heat conductivity results. With becoming modifications, the proven PDEs are moved into popular differential situations and paintings mathematically making use of a specific mathematical plan called the Keller box method (KBM). The ranges of different dimensionless parameters used in our study are volume fraction of nanoparticles 0.01≤ϕ≤0.04, magnetic parameter 0.5≤Λ≤2, heat source/sink parameter 0.5≤Q0≤2, Prandtl number 5.7≤Pr≤6.2, Reynolds number 5≤Re≤15, which shows up during mathematical arrangement are shown as tables and charts. Positive modifications in heat radiation and heat conductivity affects increment the hotness pass coefficient of solar primarily based totally plane wings. Titanium alloy primarily based totally water (H2O) are taken into consideration for our research. We can see that because the Reynolds range and Brinkman range increment, the entropy increments. The thermodynamic exhibition of Titanium alloy-water (Ti6Al4V- H2O) nanofluid has been portrayed higher that of base nanofluid with comparable situations. Recorded hypothetical reproductions may be greater beneficial to similarly increase daylight primarily based totally nuclear strength frameworks
Thermal degradation of polylactic acid (PLA)/polyhydroxybutyrate (PHB) blends: A systematic review
- Mael Kervran
- Christelle Vagner
- Marianne Cochez
- Marc Ponçot
- Mohammad Saeb
- Henri Vahabi
2022 POLYMER DEGRADATION AND STABILITY
Polylactic acid (PLA) and polyhydroxybutyrate (PHB) are two biopolyesters obtained from renewable resources like corn or sugar under bacterial fermentation. PLA is the most widely used biopolymer in diverse applications. Addition of PHB to PLA can improves the crystallinity of PLA, and thereby its mechanical strength. However, both PLA and PHB suffer from poor thermal stability, which limits their potential industrial application. The purpose of this review is to explain thermal decomposition behavior and mechanism of these polymers and systematically categorize available reports on thermal degradation of the neat PLA and PHB, and also as-processed PLA/PHB blends along with PLA/PHB blends modified/reinforced with plasticizers, additives or crosslinkers. The characteristic temperatures (Tonset, and peak temperature or Tmax) of PLA and PHB are taken as the key parameters governing thermal degradation behavior of PLA/PHB blends and composites with variable composition. From this survey we can conclude that the thermal stability of PLA in PLA/PHB blend is lower than the neat PLA, contrary to the PHB with higher thermal stability in PLA/PHB blend. Therefore, thermal degradation mechanism of PLA/PHB blends must be taken as a complex physico-chemical phenomenon. Moreover, the selection of additive severely affects the thermal stability of PLA/PHB blends. Processing method and localization of additive in different phases or at the interface of the phases are factors determining the ultimate thermal stability of blend.
Thermal dewetting as a method of surface modification of the gold thin films for surface plasmon resonance based sensor applications
- Marcin Łapiński
- Robert Kozioł
- Agnieszka Zawadzka
- Wojciech Sadowski
- Barbara Kościelska
2022 Materials Today Communications
Here, we report a quick and simple approach with low, optimized production costs to obtain surface plasmon resonance (SPR) based sensors fabricated through a time- and resource-effective method based on thermal dewetting of thin Au films. From the applicative point of view, the method of detection presented here should be easier to implement, since light transmission measurements seem to be much less challenging than light refractive index changes measurements conducted by many authors. Metallic films with nanometric thickness were deposited by magnetron sputtering method on a Corning 1737 glass substrates. Plasmonic nanostructures were formatted as a result of thermal annealing of the films. The detection repeatability, selectivity, and sensibility of manufactured devices were investigated. For this purpose, many verification tests were performed. The quality of the plasmonic nanostructures used for the detection was examined by scanning electron microscopy (SEM), high-resolution transmission electron microscopy (HR-TEM), and ultraviolet-visible spectroscopy (UV–VIS). X-ray photoelectron spectroscopy (XPS) and Fourier transform infrared spectroscopy (FTIR) spectra showed the absence of any signs of structure degradation after several cycles of detection in the liquid environment. The surface plasmon resonance position of the achieved sensors was linearly changeable in correlation with the ethanol concentration, which translates into their high robustness. Such a simply prepared sensing device showed key features desired in the detection in the liquids area, which opens up the possibility of large-scale commercial production
Thermal Energy Development in Magnetohydrodynamic Flow Utilizing Titanium Dioxide, Copper Oxide and Aluminum Oxide Nanoparticles: Thermal Dispersion and Heat Generating Formularization
- Muhammad Bilal Hafeez
- Marek Krawczuk
- Wasim Jamshed
2022 Pełny tekst Frontiers in Energy Research
The main aim of this article heat transfer in thermal engineering deals with the production, use, transformation, and transfer of thermal energy. Engineering and industrial fields including food packaging, the production of food additives, electronic cooling, microturbines, etc. heavily rely on heat transmission. Due to its intriguing potential in industries like the production of polymers, paper, crystal glass, etc., scientists from all over the world have endeavored to investigate the effect of heat transmission on fluid flows past an expandable surface.
Thermal Instability of Choline Chloride-Based Deep Eutectic Solvents and Its Influence on Their Toxicity─Important Limitations of DESs as Sustainable Materials
- Mateusz Marchel
- Hubert Cieśliński
- Grzegorz Boczkaj
2022 Pełny tekst INDUSTRIAL & ENGINEERING CHEMISTRY RESEARCH
Deep eutectic solvents (DESs) have become a hot topic in many branches of science due to their remarkable properties. They have been studied in a wide variety of applications. In particular, choline chloride (ChCl)-based DESs are one of the most commonly used representatives of these fluids. Nevertheless, in order to apply DESs in some fields, it is essential to guarantee their stability, reusability, and biocompatibility. In this context, the long-term stability of three ChCl-based DESs formed using glucose, malonic acid, and urea as hydrogen bond donors was investigated. Furthermore, the possible formation of toxic byproducts during long-term heating was evaluated for the first time, and toxicological studies using three bacterial strains (Escherichia coli, Pseudomonas aeruginosa, and Staphylococcus aureus) were performed. ChCl:urea DES revealed a high long-term thermal stability and was also found to be less toxic to the bacteria and thus can be considered as green solvent. ChCl:glucose DES started to decompose as a result of possible caramelization at 100 °C, and decomposition was further promoted at more elevated temperatures. Degradation of this DES did not affect greatly the toxicity toward bacteria, and low antibacterial properties were observed. The applicability of ChCl:malonic DES is not recommended as this DES was shown to be thermally unstable due to esterification and decomposition of malonic acid into acetic acid and carbon dioxide. Moreover, high toxicity of this DES in comparison to other DESs assayed in this study was reported.
Thermal properties of a cement composite containing phase change materials (PCMs) with post-pyrolytic char obtained from spent tyres as a carrier
- Michał Ryms
- Katarzyna Januszewicz
- Elżbieta Haustein
- Paweł Kazimierski
- Witold Lewandowski
2022 ENERGY
This work examines the possible use of post-pyrolysis char made from spent vehicle tyres as a carrier for phase change materials (PCM), which could be used as an additive to cement mortar. Because of the ability of PCM to accumulate heat, the cement composite obtained from it, apart from its structural and strength properties, will acquire an additional energy storage function, which can be very important for energy-saving construction. In the development of the new cement composite, Rubitherm RT22 was used as a PCM. Rubitherm's phase change temperature is within the range (ca 17–25 °C) of temperature fluctuations in buildings. Systematic comparative tests were carried out in order to evaluate the thermal properties of the new cement composite containing 0.67, 2.00, 3.33, 4.67 and 6.67% of char, which contains 32% PCM, i.e. the maximum amount that can be permanently absorbed without activation. These tests included calorimetric measurements of the influence of the composite's composition on the cumulative specific heat, and took phase change effects into consideration. The results of the experiments showed that the use of tyre char as a PCM carrier in cement mortars is not only possible, but also thermodynamically advantageous.
Thermal visualization of Ostwald-de Waele liquid in wavy trapezoidal cavity: Effect of undulation and amplitude
- Ahmad Hijaz
- Rashid Mahmood
- Muhammad Bilal Hafeez
- Afraz Hussain Majeed
- Sameh Askar
- Hasan Shahzad
2022 Pełny tekst Case Studies in Thermal Engineering
The present study is concerned with the numerical simulations of Ostwald-de Waele fluid flow in a wavy trapezoidal cavity in the presence of a heated cylinder situated at the center of the cavity. The work consists in characterizing the mixed convection as a function of the intensity of heat flow. The flow behaviour and temperature distribution in a cavity are the main focus of this study. The lower wall of the cavity is fixed and heated while the wavy surface is insulated and moves with a constant speed. The sloping walls are kept cold and are subject to zero no-slip conditions for velocity components. The whole setup is modeled as a set of coupled partial differential equations and is solved by the Finite Element Method. For pressure and velocity approximations, we use the stable finite element pair , while for temperature approximation we use the space of linear polynomial as The ranges of the parameters involved in the study are the Ostwald-de Wale index , Prandlt number Grashof number , the number of undulation , and the non-dimensional amplitude of the wavy surface . The major findings of the study are shown using velocity profile, streamlines, and isotherms. Moreover, the kinetic energy and average Nusselt number is determined for various values of the parameters involved.
Thermally activated persulfate-based Advanced Oxidation Processes — recent progress and challenges in mineralization of persistent organic chemicals: a review
- Shirish H. Sonawane
- Manoj P Rayaroth
- Vividha K. Landge
- Kirill Fedorov
- Grzegorz Boczkaj
2022 Pełny tekst Current Opinion in Chemical Engineering
Thermally activated persulfate (TAP) finds application in Advanced Oxidation Processes for the removal of pollutants from contaminated water and soil. This paper reviewed the various cases of TAP in the environmental remediation. The pollutants such as individual pharmaceuticals, biocides, cyclic organic compounds, and dyes are considered in this review. It is interesting to note that most of the organic compounds undergo complete degradation at a high temperature of 70°C with a first-order reaction kinetics. The influence of operating parameters such as temperature, persulfate concentration, initial pH, and degradation behavior in the presence of natural water constituents are also discussed. In addition, several processes to reduce the temperature of TAP are highlighted.
Thermodynamic, ecological, and economic analysis of negative CO2 emission power plant using gasified sewage sludge
- Artur Ziółkowski
- Halina Pawlak-kruczek
- Paweł Madejski
- Przemysław Bukowski
- Tomasz Ochrymiuk
- Kamil Stasiak
- Milad Amiri
- Lukasz Niedzwiecki
- Dariusz Mikielewicz
2022 Pełny tekst
Currently, sewage sludge is considered as a biomass, according to the Polish act on renewable energy sources from 20th of February 2015 and its novel version from 19th of July 2019. Possibility to utilize sewage sludge in gasification process is an additional advantage of the negative CO2 emissions power plant (nCO2PP). The work presents results of thermodynamic, ecological, and economical analysis using a zero-dimensional mathematical models of a negative CO2 emission novel structure power plant. Parameters of thermodynamic cycles such as output power, efficiency, combustion gas composition, exhaust temperature, avoided emission of carbon dioxide, as well Specific Primary Energy Consumption for Carbone Avoided (SPECCA), Discounted cash-flows, NPV, IRR etc., will be taken into account. Precise thermodynamic models are particularly important for Carbon Capture and Storage (CCS) and CCU (Carbon Capture and Utilization) energy system, where quite new devices mutually cooperate and their thermodynamic parameters affect those devices. Proposed negative CO2 emission novel power plant includes wet combustion chamber, spray-ejector condenser, gas-steam turbine, sewage sludge gasifier, separator of CO2, to determine the effect of cycle into environment. First of all, the possibility of a negative CO2 emission power plant and the positive environmental impact of the proposed solution has been demonstrated. Secondly, the technical-economic analysis made for presented feasibility study showed the high profitability of the installation which allows to: 1) gasification and vitrification of the sludge, 2) energy generation and 3) CO2 capture. All these activities are the basis of revenues or avoided costs. According to the performed analysis, the real return period for assumed commercial scale installation is 4 years. Internal rate of return is also high (IRR=24.11%). The main conclusion is that the investment in the analysed installation is profitable.
Thermodynamic study of binary mixtures of 2-propanol with ionic liquids, 1-hexyl-3-methylimidazolium bis(trifluoromethylsulfonyl)imide, 1-hexyl-3-methylimidazolium trifluoromethanesulfonate and triethylhexylammonium bis(trifluoromethylsulfonyl)imide
- Dorota Warmińska
- Iwona Cichowska-Kopczyńska
2022 JOURNAL OF CHEMICAL THERMODYNAMICS
In this work, densities, speeds of sound, refractive indices and viscosities of three binary mixtures containing the ionic liquids 1-hexyl-3-methylimidazolium bis(trifluoromethyl-sulfonyl)imide, 1-hexyl-3-methylimidazolium trifluoromethanesulfonate and triethylhexyl-ammonium bis(trifluoromethylsulfonyl)imide, mixed with 2-propanol at wide temperature and composition ranges at atmospheric pressure have been measured. From these experimental data, the excess molar volume, excess molar compressibility, deviation in refractive index and deviation in viscosity have been calculated. Excess properties have been correlated with the composition data using Redlich-Kister polynomial equation. The effects of temperature, cation and anion of ionic liquid on the physicochemical properties were analysed and discussed in terms of intermolecular interactions occurring in the studied systems. The Prigogine-Flory-Patterson theory was examined for suitability for the correlation of excess molar volumes with compositions.
Thermomechanical and Fire Properties of Polyethylene-Composite-Filled Ammonium Polyphosphate and Inorganic Fillers: An Evaluation of Their Modification Efficiency
- Mateusz Barczewski
- Aleksander Hejna
- Kamila Sałasińska
- Joanna Aniśko
- Adam Piasecki
- Katarzyna Skórczewska
- Jacek Andrzejewski
2022 Pełny tekst Polymers
The development of new polymer compositions characterized by a reduced environmental impact while lowering the price for applications in large-scale production requires the search for solutions based on the reduction in the polymer content in composites’ structure, as well as the use of fillers from sustainable sources. The study aimed to comprehensively evaluate introducing low-cost inorganic fillers, such as copper slag (CS), basalt powder (BP), and expanded vermiculite (VM), into the flame-retarded ammonium polyphosphate polyethylene composition (PE/APP). The addition of fillers (5–20 wt%) increased the stiffness and hardness of PE/APP, both at room and at elevated temperatures, which may increase the applicability range of the flame retardant polyethylene. The deterioration of composites’ tensile strength and impact strength induced by the presence of inorganic fillers compared to the unmodified polymer is described in detail. The addition of BP, CS, and VM with the simultaneous participation of APP with a total share of 40 wt% caused only a 3.1, 4.6, and 3 MPa decrease in the tensile strength compared to the reference value of 23 MPa found for PE. In turn, the cone calorimeter measurements allowed for the observation of a synergistic effect between APP and VM, reducing the peak heat rate release (pHRR) by 60% compared to unmodified PE. Incorporating fillers with a similar thermal stability but differing particle size distribution and shape led to additional information on their effectiveness in changing the properties of polyethylene. Critical examinations of changes in the mechanical and thermomechanical properties related to the structure analysis enabled the definition of the potential application perspectives analyzed in terms of burning behavior in a cone calorimetry test. Adding inorganic fillers derived from waste significantly reduces the flammability of composites with a matrix of thermoplastic polymers while increasing their sustainability and lowering their price without considerably reducing their mechanical properties, which allows for assigning developed materials as a replacement for flame-retarded polyethylene in large-scale non-loaded parts.
Three-Dimensional Fractography for Conventional and Additive Manufactured Steels After Bending-Torsion Fatigue
- Wojciech Macek
- Ricardo Branco
- Jarosław Trembacz
- José Domingos Costa
- J. A. M. Ferreira
- Carlos Capela
2022 Structural Integrity
In this study, fracture surface topography parameters were measured to investigate the effects of multiaxial loading. In order to assess the metrological aspects of fracture for notched specimens made of high-strength steels processed by both conventional and additively manufacturing (AM) techniques, an optical surface profilometer was used. Three bending moment to torsion moment ratios (B/T) were studied, i.e. 2, 1 and 2/3. The geometries were solid round bars with lateral notches made of conventional steel and hollow round bars with transversal holes for AM specimens. The investigations indicate that arithmetical mean height, Sa, decreased and fractal dimension, Df, increased with higher B/T ratios and higher fatigue lives.
Three-dimensional Weyl topology in one-dimensional photonic structures
- Kosmas L. Tsakmakidis
- Tomasz Stefański
2022 Pełny tekst Light-Science & Applications
Topological features, in particular distinct band intersections known as nodal rings, usually requiring three-dimensional structures, have now been demonstrated experimentally in an elegantly simple one-dimensional photonic crystal.
Time reversal invariant single-gap superconductivity with upper critical field larger than the Pauli limit in NbIr2B2
- Debarchan Das
- Karolina Górnicka
- Zurab Guguchia
- Jan Jaroszynski
- Robert J. Cava
- Weiwei Xie
- Hubertus Luetkens
- Tomasz Klimczuk
2022 PHYSICAL REVIEW B
Recently, compounds with noncentrosymmetric crystal structure have attracted much attention for providing a rich playground in search for unconventional superconductivity. NbIr2B2 is a new member to this class of materials harboring superconductivity below Tc = 7.3(2) K and a very high upper critical field that exceeds Pauli limit. Here we report on muon spin rotation (μSR) experiments probing the temperature and field dependence of effective magnetic penetration depth in this compound. Our transverse-field-μSR results suggest a fully gapped s-wave superconductivity. Furthermore, the estimated high value of the upper critical field is also supplemented by high-field transport measurements. Remarkably, the ratio Tc/λ−2 (0) obtained for NbIr2B2 (∼2) is comparable to those of unconventional superconductors. Zero-field μSR data reveal no significant change in the muon spin relaxation rate above and below Tc, evincing that time-reversal symmetry is preserved in the superconducting state. The presented results will stimulate theoretical investigations to obtain a microscopic understanding of the origin of superconductivity with preserved time-reversal symmetry in this unique noncentrosymmetric system.