scholarly journals Electrospun Anion-Conducting Ionomer Fibers—Effect of Humidity on Final Properties

Polymers ◽  
2020 ◽  
Vol 12 (5) ◽  
pp. 1020 ◽  
Author(s):  
Manar Halabi ◽  
Meirav Mann-Lahav ◽  
Vadim Beilin ◽  
Gennady E. Shter ◽  
Oren Elishav ◽  
...  
Keyword(s):  
Ionic Conductivity ◽  
Relative Humidity ◽  
Water Uptake ◽  
Electrospun Fiber ◽  
Large Diameter ◽  
Fiber Mats ◽  
Electrochemical Devices ◽  
Anion Conductivity

Anion-conducting ionomer-based nanofibers mats are prepared by electrospinning (ES) technique. Depending on the relative humidity (RH) during the ES process (RHES), ionomer nanofibers with different morphologies are obtained. The effect of relative humidity on the ionomer nanofibers morphology, ionic conductivity, and water uptake (WU) is studied. A branching effect in the ES fibers found to occur mostly at RHES < 30% is discussed. The anion conductivity and WU of the ionomer electrospun mats prepared at the lowest RHES are found to be higher than in those prepared at higher RHES. This effect can be ascribed to the large diameter of the ionomer fibers, which have a higher WU. Understanding the effect of RH during the ES process on ionomer-based fibers’ properties is critical for the preparation of electrospun fiber mats for specific applications, such as electrochemical devices.

First global assessment of modelled aerosol hygroscopicity in the context of other aerosol optical properties

2021 ◽  
Author(s):  
Maria Ángeles Burgos Simón ◽  
Elisabeth Andrews ◽  
Gloria Titos ◽  
Angela Benedetti ◽  
Huisheng Bian ◽  
...  
Keyword(s):  
Optical Properties ◽  
Light Scattering ◽  
Relative Humidity ◽  
Water Uptake ◽  
Chem Phys ◽  
Earth System ◽  
Aerosol Optical Properties ◽  
System Models ◽  
Earth System Models

&lt;p&gt;The particle hygroscopic growth impacts the optical properties of aerosols and, in turn, affects the aerosol-radiation interaction and calculation of the Earth&amp;#8217;s radiative balance. The dependence of particle light scattering on relative humidity (RH) can be described by the scattering enhancement factor f(RH), defined as the ratio between the particle light scattering coefficient at a given RH divided by its dry value.&lt;/p&gt;&lt;p&gt;The first effort of the AeroCom Phase III &amp;#8211; INSITU experiment was to develop an observational dataset of scattering enhancement values at 26 sites to study the uptake of water by atmospheric aerosols, and evaluate f(RH) globally (Burgos et al., 2019). Model outputs from 10 Earth System Models (CAM, CAM-ATRAS, CAM-Oslo, GEOS-Chem, GEOS-GOCART, MERRAero, TM5, OsloCTM3, IFS-AER, and ECMWF) were then evaluated against this in-situ dataset. Building on these results, we investigate f(RH) in the context of other aerosol optical and chemical properties, making use of the same 10 Earth System Models (ESMs) and in-situ measurements as in Burgos et al. (2020) and Titos et al. (2021).&lt;/p&gt;&lt;p&gt;Given the difficulties of deploying and maintaining instrumentation for long-term, accurate and comprehensive f(RH) observations, it is desirable to find an observational proxy for f(RH). This observation-based proxy would also need to be reproduced in modelling space. Our aim here is to evaluate how ESMs currently represent the relationship between f(RH), scattering &amp;#197;ngstr&amp;#246;m exponent (SAE), and single scattering albedo (SSA). This work helps to identify current challenges in modelling water-uptake by aerosols and their impact on aerosol optical properties within Earth system models.&lt;/p&gt;&lt;p&gt;We start by analyzing the behavior of SSA with RH, finding the expected increase with RH for all site types and models. Then, we analyze the three variables together (f(RH)-SSA-SAE relationship). Results show that hygroscopic particles tend to be bigger and scatter more than non-hygroscopic small particles, though variability within models is noticeable. This relationship can be further studied by relating SAE to model chemistry, by selecting those grid points dominated by a single chemical component (mass mixing ratios &gt; 90%). Finally, we analyze model performance at three specific sites representing different aerosol types: Arctic, marine and rural. At these sites, the model data can be exactly temporally and spatially collocated with the observations, which should help to identify the models which exhibit better agreement with measurements and for which aerosol type.&lt;/p&gt;&lt;p&gt;&amp;#160;&lt;/p&gt;&lt;p&gt;Burgos, M.A.&amp;#160;et al.:&amp;#160;A global view on the effect of water uptake on aerosol particle light scattering.&amp;#160;Sci Data&amp;#160;6,&amp;#160;157. https://doi.org/10.1038/s41597-019-0158-7, 2019.&lt;/p&gt;&lt;p&gt;Burgos, M.A. et al.: A global model&amp;#8211;measurement evaluation of particle light scattering coefficients at elevated relative humidity, Atmos. Chem. Phys., 20, 10231&amp;#8211;10258, https://doi.org/10.5194/acp-20-10231-2020, 2020.&lt;/p&gt;&lt;p&gt;Titos, G. et al.: A global study of hygroscopicity-driven light scattering enhancement in the context of other in-situ aerosol optical properties, Atmos. Chem. Phys. Discuss. [preprint], https://doi.org/10.5194/acp-2020-1250, in review, 2020.&lt;/p&gt;

Production and Characterization of Nanoporous Polymer Membranes Produced by an Electrospraying Process

2000 ◽  
Author(s):  
Phillip Gibson ◽  
Heidi Schreuder-Gibson
Keyword(s):  
Transport Properties ◽  
Membrane Structure ◽  
Protective Clothing ◽  
Theoretical Calculations ◽  
Electrospun Fiber ◽  
Air Flow ◽  
Filtration Efficiency ◽  
Thin Layers ◽  
Direct Result ◽  
Fiber Mats

Abstract Electrospinning is a process by which high voltages are used to produce an interconnected membrane-like web of small fibers (10 to 500 nanometers in diameter). This novel fiber spinning technique provides the capacity to lace together a variety of types of polymers, fibers, and particles to produce ultrathin layers which are useful for chemical protective clothing. Of particular interest are electrospun membranes composed of elastomeric fibers, which are under development for several protective clothing applications. The various factors influencing electrospun nonwoven fibrous membrane structure and transport properties are discussed. Performance measurements on experimental electrospun fiber mats compared favorably with transport properties of textiles and membranes currently used in protective clothing systems. It was found that electrospun layers presented minimal impedance to moisture vapor diffusion required for evaporative cooling. There may be special considerations in the application of elastomeric membranes for protective clothing. Effects of membrane distortion upon transport behavior of the structure might be significant. Preliminary measurements have found that changes in elastomeric membrane structure under different states of biaxial strain were reflected in measurements of air flow through the membrane. Changes in membrane structure were also evident in environmental scanning electron microscope images of the pore/fiber rearrangement as the membrane was stretched. Experimental measurements and theoretical calculations show electrospun fiber mats to be extremely efficient at trapping airborne particles. The high filtration efficiency is a direct result of the submicron-size fibers generated by the electrospinning process. Electrospun nanofiber coatings were applied directly to an open cell polyurethane foam. The air flow resistance and aerosol filtration properties correlated with the electrospun coating add-on weight. Particle penetration through the foam layer, which is normally very high, was eliminated by extremely thin layers of electrospun nanofibers sprayed on to the surface of the foam. Electrospun fiber coatings produce an exceptionally lightweight multifunctional membrane for protective clothing applications which exhibits high breathability, elasticity, and filtration efficiency.

Optimization of Chitosan/PVA Concentration in Fabricating Nanofibers Membrane and its Prospect as Air Filtration

2017 ◽  
Vol 901 ◽  
pp. 20-25 ◽  
Author(s):  
Himayatus Shalihah ◽  
Ahmad Kusumaatmaja ◽  
Ari Dwi Nugraheni ◽  
Kuwat Triyana
Keyword(s):  
Electrospun Fiber ◽  
Chemical Compounds ◽  
Average Diameter ◽  
Air Filtration ◽  
Maximum Condition ◽  
Chemical Absorption ◽  
Fiber Mats ◽  
Before And After ◽  
Porosity Percentage ◽  
Scanning Electron

Chitosan/polyvinyl-alcohol (Chitosan/PVA) based nanofibers were successfully produced using electrospinning machine and investigated their application as air filtration. Firstly, 2 wt% chitosan was dissolved to 1 wt% acetic acid followed by mixing with PVA solution to produce fiber mats or membrane. Secondly, the morphology and diameter of the electrospun fiber were analyzed by using a scanning electron microscopy (SEM), while the chemical compounds in the membrane were characterized using Fourier transform infrared spectroscopy (FTIR). It was found that the conductivity of solution increased by the concentration of chitosan. Meanwhile, the average diameter and percentage of porosity decreased due to the upsurge of the conductivity of the solution. The average diameter of PVA 13 wt% was and the percentage of porosity were 50.32%. The maximum condition of chitosan/PVA was obtained at 20/80 wt%, in line with the average of fiber diameters and the percentage of porosity were 25.32%. Physicochemical properties of chitosan/PVA solution, such as conductivity, morphology, and chemical absorption were investigated before and after the air filtration. The porosity percentage of PVA 13wt% after air filtration changed to 35.85% and the percentage of porosity of chitosan/PVA 20/80 became 25.32%. Remarkable absorption peaks of PVA 13wt% exhibited and - shifted after the air filtration test, it was indicating that functional groups had been reduced. The chemical absorption of chitosan/PVA 20/80 wt% showed at the the region then disappeared after the air filtration test.

Aerosol size and relative humidity: Water uptake by mixtures of salts

Tellus ◽  
1979 ◽  
Vol 31 (6) ◽  
pp. 478-486 ◽  
Author(s):  
GOTTFRIED HÄNEL ◽  
BRIGITTE ZANKL
Keyword(s):  
Relative Humidity ◽  
Water Uptake

scholarly journals Non-invasive diagnosis of viability in seeds and lichens by infrared thermography under controlled environmental conditions

Plant Methods ◽  
2019 ◽  
Vol 15 (1) ◽  
Author(s):  
Beatriz Fernández-Marín ◽  
Othmar Buchner ◽  
Gerald Kastberger ◽  
Federica Piombino ◽  
José Ignacio García-Plazaola ◽  
...  
Keyword(s):  
Relative Humidity ◽  
Infrared Thermography ◽  
Water Uptake ◽  
Imaging Techniques ◽  
Time Windows ◽  
Life Forms ◽  
Aerobic Metabolism ◽  
Gaseous Atmosphere ◽  
Non Invasive ◽  
Pea Seeds

Abstract Background Non-invasive procedures for the diagnosis of viability of plant or fungal tissues would be valuable for scientific, industrial and biomonitoring purposes. Previous studies showed that infrared thermography (IRT) enables non-invasive assessment of the viability of individual "orthodox" (i.e. desiccation tolerant) seeds upon water uptake. However, this method was not tested for rehydrating tissues of other desiccation tolerant life forms. Furthermore, evaporative cooling could obscure the effects of metabolic processes that contribute to heating and cooling, but its effects on the shape of the "thermal fingerprints" have not been explored. Here, we further adapted this method using a purpose-built chamber to control relative humidity (RH) and gaseous atmosphere. This enabled us to test (i) the influence of relative humidity on the thermal fingerprints during the imbibition of Pisum sativum (Garden pea) seeds, (ii) whether thermal fingerprints can be correlated with viability in lichens, and (iii) to assess the potential influence of aerobic metabolism on thermal fingerprints by controlling the oxygen concentration in the gaseous atmosphere around the samples. Finally, we developed a method to artificially "age" lichens and validated the IRT-based method to assess lichen viability in three lichen species. Results Using either 30% or 100% RH during imbibition of pea seeds, we showed that "live" and "dead" seeds produced clearly discernible "thermal fingerprints", which significantly differed by > |0.15| °C in defined time windows, and that RH affected the shape of these thermal fingerprints. We demonstrated that IRT can also be used to assess the viability of the lichens Lobaria pulmonaria, Pseudevernia furfuracea and Peltigera leucophlebia. No clear relationship between aerobic metabolism and the shape of thermal fingerprints was found. Conclusions Infrared thermography appears to be a promising method for the diagnosis of viability of desiccation-tolerant tissues at early stages of water uptake. For seeds, it is possible to diagnose viability within the first hours of rehydration, after which time they can still be re-dried and stored until further use. We envisage our work as a baseline study for the use of IR imaging techniques to investigate physiological heterogeneity of desiccation tolerant life forms such as lichens, which can be used for biomonitoring, and for sorting live and dead seeds, which is potentially useful for the seed trade.

scholarly journals Bio-Based Polymer Electrolytes for Electrochemical Devices: Insight into the Ionic Conductivity Performance

Materials ◽  
2020 ◽  
Vol 13 (4) ◽  
pp. 838 ◽  
Author(s):  
Marwah Rayung ◽  
Min Min Aung ◽  
Shah Christirani Azhar ◽  
Luqman Chuah Abdullah ◽  
Mohd Sukor Su’ait ◽  
...  
Keyword(s):  
Ionic Conductivity ◽  
Polymer Electrolyte ◽  
Polymer Electrolytes ◽  
Future Prospects ◽  
Electrolyte System ◽  
The Past ◽  
Device Applications ◽  
Electrochemical Devices ◽  
Insight Into ◽  
General Method

With the continuing efforts to explore alternatives to petrochemical-based polymers and the escalating demand to minimize environmental impact, bio-based polymers have gained a massive amount of attention over the last few decades. The potential uses of these bio-based polymers are varied, from household goods to high end and advanced applications. To some extent, they can solve the depletion and sustainability issues of conventional polymers. As such, this article reviews the trends and developments of bio-based polymers for the preparation of polymer electrolytes that are intended for use in electrochemical device applications. A range of bio-based polymers are presented by focusing on the source, the general method of preparation, and the properties of the polymer electrolyte system, specifically with reference to the ionic conductivity. Some major applications of bio-based polymer electrolytes are discussed. This review examines the past studies and future prospects of these materials in the polymer electrolyte field.

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