2020 - Repozytorium publikacji - Politechnika Gdańska

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Effect of Base-Connection Strength and Ductility on the Seismic Performance of Steel Moment-Resisting Frames
- Tomasz Falborski
- Pablo Torres-Rodas
- Farzin Zareian
- Amit Kanvinde
2020 JOURNAL OF STRUCTURAL ENGINEERING-ASCE
Column-base connections in steel moment-resisting frames (SMFs) in seismic regions are commonly designed to develop the capacity of adjoining column with an intent to develop a plastic hinge in the column member, rather than in the connection (i.e., a strong-base design). Recent research has shown base connections to possess high ductility, indicating that this practice may be not only expensive but also unnecessary. This suggests that concentrating inelastic rotations in the base connection may result in acceptable performance. Motivated by this finding, the performance of steel moment resisting frames with a weak-base design is investigated to examine the relationships between base-connection strength, deformation capacity, and structural performance. The main scientific basis of this study is nonlinear static pushover and nonlinear time history simulations on SMFs designed for high seismicity. These simulations interrogate parameters including frame height (4-, 8-, 12-, and 20-story), base-connection strength, base flexibility, and base rotation capacity, resulting in a total of 160 parametric combinations. The performance of each of these is assessed to estimate the probabilities of failure or collapse corresponding to a 2/50 (2% probability of exceedance in 50 years) intensity of shaking. The key finding is that for all frames, acceptable performance (i.e., comparable to current practice with capacity-designed bases) may be obtained by designing the base connections for overstrength seismic loads (i.e., based on the Ω factor) rather than based on column capacity; this has the potential to offer significant cost savings. For a low-rise (i.e., four-story) frame, acceptable performance is achieved even without significant rotational demands in the base connection. For the other frames, a baseconnection rotation capacity of approximately 0.05 rad is necessary to achieve acceptable performance. Implications of these findings for prospective design practices, as well as future research, are outlined, and limitations are discussed.
Effect of bio-based components on the chemical structure, thermal stability and mechanical properties of green thermoplastic polyurethane elastomers
- Paulina Parcheta
- Ewa Głowińska
- Janusz Datta
2020 Pełny tekst EUROPEAN POLYMER JOURNAL
It seems to be obvious that conditions changes during polyols synthesis have impact on the polyols properties. Even the chemical formula is the same or similar, physicochemical properties and also molecular weight of polyols might be different and are significant in term of future polyurethanes properties and processing. In this work, fully bio-based poly(propylene succinate)s synthesized at different temperature conditions were used as a polyol in thermoplastic polyurethane elastomers (TPU) synthesis. Novel bio-based TPUs were synthesized with the use of mentioned bio-based linear polyester polyols, poly(propylene succinate)s and also 4,4-diphenylmethane diisocyanate (MDI) and a chain extender 1,4-butanediol (BDO) or 1,3-propanediol (PDO), both with the natural origin. Influence of synthesized bio-based polyols on thermoplastic polyurethane elastomers characteristic was determined based on investigation of chemical structure, thermal, thermomechanical, mechanical and physical properties of synthesized bio-based TPU. Fourier transform infrared spectroscopy (FTIR) and proton nuclear magnetic resonance (1H NMR) were applied to the chemical formula determination. Thermogravimetry was supportive in thermal analysis, dynamic mechanical analysis (DMA), tensile test and hardness were used to determine thermomechanical behavior and mechanical properties at static and dynamic condition. The density of the obtained materials was also measured. It was established that using obtained fully bio-based polyester polyols the thermoplastic polyurethane elastomers can be synthesis without catalyst usage. Based on the results demonstrated greater influence of type of chain extender on bio-based TPU properties than condition of bio-based polyester synthesis. Each sample was characterized by glass temperature (Tg) ca. 0-5°C and similar thermal stability ca. 320°C. The tensile strength of prepared bio-based TPUs reach even 30 MPa with an elongation at break ca. 550%.
Effect of bitumen characteristics obtained according to EN and Superpave specifications on asphalt mixture performance in low-temperature laboratory tests
- Dawid Ryś
- Mariusz Jaczewski
- Marek Pszczoła
- Piotr Jaskuła
- Wojciech Bańkowski
2020 Pełny tekst CONSTRUCTION AND BUILDING MATERIALS
The paper aims to identify those characteristics of bitumen which have the greatest impact on asphalt mixture low-temperature performance. It was observed that stiffness and m-value of bitumen from BBR test were moderately related to stiffness and m-value of asphalt mixture obtained from 3 PB test. Simultaneously those rheological properties significantly impact on cryogenic stresses induced during TSRST test. The multiple regression model was developed and it implied that mixture failure temperature depends both on rheological properties, brittle fracture and content of bitumen, what means that only comprehensive assessment of bitumen properties enables reasonable assessment of its low-temperature performance.
Effect of chemical structure on complexation efficiency of aromatic drugs with cyclodextrins: The example of dibenzazepine derivatives
- Koleta Hemine
- Anna Skwierawska
- Cyprian Kleist
- Michał Olewniczak
- Katarzyna Szwarc-Karabyka
- Dariusz Wyrzykowski
- Anna Mieszkowska
- Jarosław Chojnacki
- Jacek Czub
- Łukasz Nierzwicki
2020 CARBOHYDRATE POLYMERS
It is widely believed that the hydrophobic effect governs the binding of guest molecules to cyclodextrins (CDs). However, it is also known that high hydrophobicity of guest molecules does not always translate to the formation of stable inclusion complexes with CDs. Indeed, a plethora of other factors can play a role in the efficiency of guest–CD interactions, rendering structure-based prediction of the complexation efficiency with CDs a non trivial task. In this combined experimental and computational study, we examine the major structural factors governing complexation efficiency of polycyclic aromatic drug-like compounds with natural CDs, using as an example iminostilbene and its N-substituted derivatives. We find that purely hydrophobic IS derivatives show negligible complexation efficiency with CDs and only IS with hydrophilic substituents form stable inclusion complexes in water. We show that the balance between the guest solubility and its affinity to CDs is critical for the effective formation of inclusion complexes. Finally, our results demonstrate that guest–host hydrogen bonds facilitate the formation of crystalline inclusion complexes with CDs.
Effect of Different Bromine Sources on the Dual Cation Mixed Halide Perovskite Solar Cells
- Damian Głowienka
- Francesco Giacomo Di
- Mehrdad Najafi
- Ilker Dogan
- Alfredo Mameli
- Fallon J. M. Colberts
- Jędrzej Szmytkowski
- Yulia Galagan
2020 Pełny tekst ACS Applied Energy Materials
Recent research has shown that perovskite solar cells with a mixed dual A-cation have much better structural stability without loss of efficiency than single cation devices. Mixed cation perovskites create a lot of questions about the salts being used for the formation of the best-quality layer. Here, we have investigated three sources of bromide in the perovskite absorption layer, using lead bromide (PbBr2), formamidinium bromide (FABr), and cesium bromide (CsBr). The experimental results have shown better performance for FABr and CsBr sources of bromide in comparison to the regularly used PbBr2. This effect has been explained with the complex species present in the not-annealed perovskite films which changes the defect states during the crystallization of the absorber layer. It has been found with numerical simulations that the observed phenomenon directly impacts the rates of the trap-assisted recombination. The results of this study are one more step forward in understanding the physics behind the crystallization process which is crucial in further improvement of the perovskite solar cells.
Effect of electrode waterproof coating on quality of underwater wet welded joints
- Jacek Tomków
- Dariusz Fydrych
- Kamil Wilk
2020 Pełny tekst Materials
In this paper, the effects of different hydrophobic coatings on the surface of covered electrodes on the quality of wet welded carbon steel joints were discussed. Commonly available hydrophobic substances used in industrial applications were selected for the research. The aim of using waterproof coatings was to check the possibility to decreasing the susceptibility of highstrength low-alloy S460N steel to cold cracking. During experiments diffusible hydrogen content in deposited metal determination by mercury method, metallographic macro- and microscopic testing and hardness measurements were performed. Investigations showed that waterproof coatings laid on covered electrodes can improve the quality of wet welded joints, by decreasing the Vickers HV10 hardness in heat-affected zone and decreasing the diffusible hydrogen content in deposited metal, which minimalize possibility of cold cracking.
Effect of Ethanol Extracts of Propolis (EEPs) against Staphylococcal Biofilm—Microscopic Studies
- Katarzyna Grecka
- Zirui Ray Xiong
- Hanyu Chen
- Karolina Pełka
- Randy Worobo
- Piotr Szweda
2020 Pełny tekst Pathogens
Staphylococci growing in the form of biofilm exhibit high resistance to a plethora of antibiotics. The aim of the study was to assess the influence of ethanolic extract of propolis (EEPs) on S. epidermidis ATCC 35984 biofilm using fluorescent microscopy. Propidium iodide (PI) and SYTO 9 were used for differentiation of live and dead cells, and calcofluor white was used to stain the extracellular matrix, the self-produced extracellular polymeric substances (EPS). The outcomes of the research confirm the promising potential of EEPs for eradication of staphylococcal biofilm. However, its activity cannot be classified as fully satisfactory, either in terms of the effectiveness of elimination of bacterial cells or disturbing the EPS structure. A two or even four times higher concentration of EEPs compared to MIC (Minimum Inhibitory Concentration) against planktonic cells (128 µg/mL) was necessary for effective (estimated for 90%) elimination of living cells from the biofilm structure. Unfortunately, even at that concentration of EEPs, the extracellular matrix was only partially disturbed and effectively protected the residual population of living cells of S. epidermidis ATCC 35984. In our opinion, a combination of EEPs with agents disrupting components of EPS, e.g., proteases, lysines, or enzymes degrading extracellular DNA or PIA (polysaccharide intercellular adhesin).
Effect of Flow Normalization in Micro-Pin-Finned Heat Sink: Numerical Study
- Gurjeet Singh
- Kumar Ritunesh
- Dariusz Mikielewicz
2020 Pełny tekst JOURNAL OF THERMOPHYSICS AND HEAT TRANSFER
The micro-pin-fin heat sink (MPFHS) is widely employed for the heat transfer enhancement of microchannel heat sinks. In the current paper, the effect of flow normalization on the thermohydraulic performance of micro-pin-finned heat sinks is studied numerically. Two geometries of MPFHSs, the conventional design micro-pin-fin heat sink (CD-MPFHS) with a uniform-width micro pin fin and the proposed design micro-pin-fin heat sink (PD-MPFHS) with a nonuniform-width micro pin fin, are studied. Flow distribution analysis in the primary and secondary channels of MPFHSs is carried out. More flow resistance offered by wider central micro pin fins diverts more flow toward side channels; as a result of which, better flow distribution in primary channels and higher flow across secondary channels are noticed for the PD-MPFHS as compared to the CD-MPFHS. As a result of that, maximum and average base temperatures are reduced by 4.6 and 2.2K as compared to the CD-MPFHS. The Nusselt number increased by 10.1%, and a better thermohydraulic performance index has been offered by the PD-MPFHS for the entire studied Reynolds number range.
Effect of interconnect coating procedure on solid oxide fuel cell performance
- Hamid Abdoli
- Sebastian Molin
- Hamidreza Farnoush
2020 Pełny tekst MATERIALS LETTERS
Chromium (Cr) species vaporizing from chromia-forming alloy interconnects is known as a source of degradation in solid oxide fuel cell (SOFC) stacks called “cathode poisoning”. (Mn,Co)3O4 spinel coatings offer good protection against Cr evaporation during operation. In this study, Crofer 22 APU steel interconnects were electrophoretically deposited in different mediums to obtain high packing of green coating layer. The optimized sample was then sintered in air-atmosphere or dual-atmospheres (reducing-oxidizing). Anode-supported cells were exposed from cathode side to bare or coated interconnects for 100 h at 800 °C. The electrochemical performances of aged cells were compared at 800 °C. Due to higher density coating obtained by dual-atmospheres sintering process, the exposed cell showed performance similar to non-poisoned cell (0.95–0.98 W/cm2). The cell exposed to air-atmosphere sintered coating interconnect showed lower output power (0.75 W/cm2) due to coating lower density. The cell exposed to uncoated interconnect exhibited considerable degradation and the lowest power (0.66 W/cm2).
Effect of pine impregnation and feed speed on sound level and cutting power in wood sawing
- Roksana Licow
- Daniel Chuchała
- Mariusz Deja
- Kazimierz Orłowski
- Piotr Taube
2020 Pełny tekst JOURNAL OF CLEANER PRODUCTION
The sound levels along with the cutting power registered during the sawing process of the impregnated and non-impregnated pine wood at two feed speeds are shown and compared in this paper. Statistically significant differences in the acoustic signals occurred at the lower feed rate. The differences became smaller with an increase in the feed speed. In contrast to the sound signal, the differences in the cutting power were statistically significant only for the higher feed rate. In addition, the average electric power of the main drive allowed for the identification of knots during the sawing process. Obtained results indicated that monitoring based on the analysis of sound signals can be used as a supplementary source of information related to the wood cutting processes. This kind of independently used monitoring could be recommended for long-running and stabilized sawing processes, due to high noise level generated during the transition states when the tool enters and exits the material - transition states.
Effect of selected ammonia escape inhibitors on carbon dioxide capture and utilization via calcium carbonate precipitation
- Natalia Czaplicka
- Donata Konopacka-Łyskawa
- Barbara Kościelska
- Marcin Łapiński
2020 Journal of CO2 Utilization
Carbon dioxide was used to precipitate CaCO3 with CaCl2 solution in the presence of NH3 as a CO2 absorption promoter. Compounds that were previously indicated as inhibitors of ammonia escape during CO2 absorption were also added to the reaction mixture. Inorganic salts, i.e. ZnCl2, CuCl2, CoCl2, and organic substances, i.e. glycerol, ethylene glycol and triethanolamine were tested inhibitors in this work. A model post-distillation liquid from the Solvay process was used as the reaction mixture, while the gas stream fed into the system had a composition corresponding to the exhausted gases produced by the fossil fuels combustion. The purpose of this research was to investigate the efficiency of CO2 sequestration and the consumption of calcium ions during precipitation in the carbonation processes and determine the characteristics of produced CaCO3 particles. Of the tested additives, glycerol turned out to be the most effective, because its presence resulted in increased calcium ion consumption and CO2 sequestration compared to the control process. 90.5 % CO2 sequestration and 88.1 % Ca2+ consumption were obtained. The CaCO3 particles obtained in the presence of all tested organic inhibitors were in the form of vaterite and were characterized by a significantly larger specific surface area and larger pore volume.
Effect of sintering temperature on electrochemical performance of porous SrTi1-xFexO3-δ (x = 0.35, 0.5, 0.7) oxygen electrodes for solid oxide cells
- Aleksander Mroziński
- Sebastian Molin
- Piotr Jasiński
2020 Pełny tekst JOURNAL OF SOLID STATE ELECTROCHEMISTRY
This work evaluates the effects of the sintering temperature (800 °C, 900 °C, 1000 °C) of SrTi1-xFexO3-δ (x = 0.35, 0.5, 0.7) porous electrodes on their electrochemical performance as potential oxygen electrode materials of solid oxide cells. The materials were prepared by a solid-state reaction method and revealed the expected cubic perovskite structure. After milling, the powders were characterised by a sub-micrometre particle size with high sinter-activity. It was shown that the lowest area specific resistance was achieved after sintering SrTi0.65Fe0.35O3 electrodes at 1000 °C, and SrTi0.5Fe0.5O3 and SrTi0.30Fe0.70O3 electrodes at 800 °C, which can be considered to be a relatively low temperature. In general, EIS measurements showed that increasing the Fe content results in lowered electrode polarisation and a decrease of the series resistance. Even though the studied materials have much lower total conductivities than state-of-the-art electrode materials (e.g. (La,Sr)(Co,Fe)O3), the polarisation resistances obtained in this work can be considered low.
Effect of Surface Treatment of Halloysite Nanotubes (HNTs) on the Kinetics of Epoxy Resin Cure with Amines
- Vahideh Akbari
- Maryam Jouyandeh
- Seyed Paran
- Mohammad Ganjali
- Hossein Abdollahi
- Henri Vahabi
- Zahed Ahmadi
- Krzysztof Formela
- Amin Esmaeili
- Ahmad Mohaddespour
- Sajjad Habibzadeh
- Mohammad Saeb
2020 Pełny tekst Polymers
The epoxy/clay nanocomposites have been extensively considered over years because of their low cost and excellent performance. Halloysite nanotubes (HNTs) are unique 1D natural nanofillers with a hollow tubular shape and high aspect ratio. To tackle poor dispersion of the pristine halloysite (P-HNT) in the epoxy matrix, alkali surface-treated HNT (A-HNT) and epoxy silane functionalized HNT (F-HNT) were developed and cured with epoxy resin. Nonisothermal differential scanning calorimetry (DSC) analyses were performed on epoxy nanocomposites containing 0.1 wt.% of P-HNT, A-HNT, and F-HNT. Quantitative analysis of the cure kinetics of epoxy/amine system made by isoconversional Kissinger–Akahira–Sunose (KAS) and Friedman methods made possible calculation of the activation energy (Eα) as a function of conversion (α). The activation energy gradually increased by increasing α due to the diffusion-control mechanism. However, the average value of Eα for nanocomposites was lower comparably, suggesting autocatalytic curing mechanism. Detailed assessment revealed that autocatalytic reaction degree, m increased at low heating rate from 0.107 for neat epoxy/amine system to 0.908 and 0.24 for epoxy/P-HNT and epoxy/A-HNT nanocomposites, respectively, whereas epoxy/F-HNT system had m value of 0.072 as a signature of dominance of non-catalytic reactions. At high heating rates, a similar behavior but not that significant was observed due to the accelerated gelation in the system. In fact, by the introduction of nanotubes the mobility of curing moieties decreased resulting in some deviation of experimental cure rate values from the predicted values obtained using KAS and Friedman methods.
Effect of the Drying Method of Pine and Beech Wood on Fracture Toughness and Shear Yield Stress
- Daniel Chuchała
- Jakub Sandak
- Kazimierz Orłowski
- Tomasz Muziński
- Marcin Lackowski
- Tomasz Ochrymiuk
2020 Pełny tekst Materials
The modern wood converting processes consists of several stages and material drying belongs to the most influencing future performances of products. The procedure of drying wood is usually realized between subsequent sawing operations, affecting significantly cutting conditions and general properties of material. An alternative methodology for determination of mechanical properties (fracture toughness and shear yield stress) based on cutting process analysis is presented here. Two wood species (pine and beech) representing soft and hard woods were investigated with respect to four diverse drying methods used in industry. Fracture toughness and shear yield stress were determined directly from the cutting power signal that was recorded while frame sawing. An original procedure for compensation of the wood density variation is proposed to generalize mechanical properties of wood and allow direct comparison between species and drying methods. Noticeable differences of fracture toughness and shear yield stress values were found among all drying techniques and for both species, but only for beech wood the differences were statistically significant. These observations provide a new highlight on the understanding of the effect of thermo-hydro modification of wood on mechanical performance of structures. It can be also highly useful to optimize woodworking machines by properly adjusting cutting power requirements.
Effect of the integration into Global Value Chains on the employment contract in Central and Eastern European countries
- Dagmara Nikulin
- Sabina Szymczak
2020 Pełny tekst EQUILIBRIUM Quarterly Journal of Economics and Economic Policy
Research background: In the era of globalization, there is a need to address decent work deficits in Global Value Chains (GVCs). The forms of working conditions reveal a broad dispersion of contents. The literature review exposes hardly any Europe-focused research assessing the socioeconomic impact of global production links and going beyond their pure economic effects assessed in terms of employment, productivity or wages. Purpose of the article: This paper investigates how involvement in GVCs affects labour standards. In particular, we assess how the integration into GVCs impacts the probability of having indefinite type of employment contract, which stands for one of the decent work indicator. Moreover, we draw individual and firm-level characteristics determining the type of employment contract. Methods: We use linked employer-employee data from the Structure of Earnings Survey merged with industry-level statistics on GVCs based on World Input-Output Database — the sample is composed of over 5 million workers from 10 Central and Eastern European countries (CEEC) observed in 2014. The involvement into GVCs is measured using a novel approach based on the concepts of global import intensity (GII). We employ logistic regression with robust standard errors. Findings & Value added: Controlling for individual and firm-level characteristics (sex, age, education level, length of service in enterprise, size of the enterprise) we find that greater integration into GVCs increases the probability of having temporary type of employment contract, mainly in tradable sectors. However, across CEE countries the relation between GVC and employment type is mixed. In this way we expand the existing literature by reporting the effects of GVCs on labour standards in CEEC.
Effect of Thermal Treatment of Birch Wood by Saturated Water Vapor on Granulometric Composition of Chips from Sawing and Milling Processes from the Point of View of Its Processing to Composites
- Richard Kminiak
- Kazimierz Orłowski
- Ladislav Dzurenda
- Daniel Chuchała
- Adrian Banski,
2020 Pełny tekst Applied Sciences-Basel
The goal of this work is to investigate the impact of thermal modification of birch wood with saturated steam on the particle size distribution of the sawing and milling process. Birch wood (Betula pendula Roth) is an excellent source to produce plywood boards. Wastes from mechanical processing of birch wood are suitable to produce composite materials. Granulometric analyses of chips from sawing processes on the PRW 15M frame saw, as well as on the 5-axis CNC machining centre SCM TECH Z5 and the 5-axis CNC machining centre AX320 Pinnacle, proved that more than 95% of chips are chips of coarse and medium coarse chip fractions with dimensions above 0.125 mm. Depending on the shape, coarse and medium-thick chips belong to the group of fiber chips, the length of which is several times greater than the width and thickness. Fine fractions with dimensions smaller than 125 μm are isometric chips that are approximately the same size in all three dimensions. Thoracic dust fractions below 30 μm were not measured. The performed analyses showed that the heat treatment of birch wood with saturated steam did not affect the grain size of chips formed in sawing and milling processes on CNC machining centre and can be used as a raw material for the production of composite materials. Fabric filters are suitable for separating chips extracted from frame saws, PRW-15M or machining centre. Environmental criteria for the separation of chips from transport air in textile filters are met by filters with a fabric classified in class G4.
Effective Collaboration of Entrepreneurial Teams—Implications for Entrepreneurial Education
- Beata Krawczyk-Bryłka
- Katarzyna Stankiewicz
- Paweł Ziemiański
- Michał Tomczak
2020 Pełny tekst Education Sciences
In the situation of a permanent change and increased competition, business ventures are more and more often undertaken not by individuals but by entrepreneurial teams. The main aim of this paper is to examine the team principles implemented by eective entrepreneurial teams and how they dier in nascent and established teams. We also focused on the relationship between the implementation of these rules by entrepreneurial team members and their evaluation of venture performance and personal satisfaction. The quantitative method was used: a list of nine items describing the principles important for the entrepreneurial teams’ collaboration was included in a questionnaire conducted in a group of 106 Polish entrepreneurs who run their businesses as members of entrepreneurial teams. The results of the research showed that all the collaboration principles included in the prepared scale are implemented by the tested entrepreneurial teams; in the case of two particular items, the obtained scores were higher in nascent teams. The correlation between principle implementation and venture performance as well as the correlation between principle implementation and entrepreneurs’ professional satisfaction was confirmed. In addition, the goal was to emphasize the importance of the entrepreneurial team’s collaboration due to its eectiveness, and propose the prepared scale as a tool for entrepreneurial reflective learning. Finally, statements by members of two entrepreneurial teams concerning team collaboration are presented to deliver case studies that can be used during entrepreneurship courses.
Effective Permeability of Multi Air Gap Ferrite Core 3-Phase Medium Frequency Transformer in Isolated DC-DC Converters
- Piotr Dworakowski
- Andrzej Wilk
- Michał Michna
- Bruno Lefebvre
- Fabien Sixdenier
- Michel Mermet-Guyennet
2020 Pełny tekst ENERGIES
The magnetizing inductance of the medium frequency transformer (MFT) impacts the performance of the isolated dc-dc power converters. The ferrite material is considered for high power transformers but it requires an assembly of type “I” cores resulting in a multi air gap structure of the magnetic core. The authors claim that the multiple air gaps are randomly distributed and that the average air gap length is unpredictable at the industrial design stage. As a consequence, the required effective magnetic permeability and the magnetizing inductance are difficult to achieve within reasonable error margins. This article presents the measurements of the equivalent B(H) and the equivalent magnetic permeability of two three-phase MFT prototypes. The measured equivalent B(H) is used in an FEM simulation and compared against a no load test of a 100 kW isolated dc-dc converter showing a good fit within a 10% error. Further analysis leads to the demonstration that the equivalent magnetic permeability and the average air gap length are nonlinear functions of the number of air gaps. The proposed exponential scaling function enables rapid estimation of the magnetizing inductance based on the ferrite material datasheet only.
Effectiveness of toluene separation from gas phase using supported ammonium ionic liquid membrane
- Iwona Cichowska-Kopczyńska
- Robert Aranowski
2020 Pełny tekst CHEMICAL ENGINEERING SCIENCE
Ammonium ionic liquids (ILs) are relatively cheap in synthesis and environmentally benign and despite that they have been very rarely used in gas separation. In this research we used several ammonium ILs as liquid membranes for removal of residual toluene from gas phase. Ionic liquids used in this study were composed of bis(trifluoromethylsulfonyl)imide anion [Tf2N] and trimethylbutylammonium [N1114], trietylbutylammonium [N2224], trietylhexylammonium [N2226], trietyloctylammonium [N2228] cations. Selected ILs formed stable membranes with limited swelling effect and good performance. The highest toluene permeability was recorded for [N2228][Tf2N] of 2666 barrers and for triethyl based ILs it was decreasing with carbon atoms number. The selectivity of toluene/N2 separation was in a range of 29 to 120. For better process illustration, the factors influencing the permeation process, namely viscosity and partition coefficients were examined.
Effects of Bromine Doping on the Structural Properties and Band Gap of CH3NH3Pb(I1–xBrx)3 Perovskite
- Miłosz Martynow
- Damian Głowienka
- Yulia Galagan
- Julien Guthmuller
2020 Pełny tekst ACS Omega
An experimental and theoretical study is reported to investigate the influence of bromine doping on CH3NH3Pb(I1−xBrx)3 perovskite for Br compositions ranging from x = 0 to x = 0.1, in which the material remains in the tetragonal phase. The experimental band gap is deduced from UV−vis absorption spectroscopy and displays a linear behavior as a function of bromine concentration. Density functional theory calculations are performed for five different series of randomly doped structures in order to simulate the disorder in bromine doping sites. The computations predict a linear variation of the lattice parameters, supercell volume, density, band gap, and formation energy in the considered doping range. The calculated evolution of the band gap as the function of Br doping is in excellent agreement with the experimental data, provided that different Br doping configurations are included in the simulations. The analysis of the structural and electronic properties shows a correlation between the increase of the band gap and the increased distortion of the Pb(I1−xBrx)6 octahedrons. Additionally, the simulations suggest that in CH3NH3Pb(I1−xBrx)3 bromine doping is likely to occur at both the equatorial and apical positions of the octahedrons.