Stabilization of Electrospun PAN/Gelatin Nanofiber Mats for Carbonization

Due to their electrical and mechanical properties, carbon nanofibers are of large interest for diverse applications, from batteries to solar cells to filters. They can be produced by electrospinning polyacrylonitrile (PAN), stabilizing the gained nanofiber mats, and afterwards, carbonizing them in inert gas. The electrospun base material and the stabilization process are crucial for the results of the carbonization process, defining the whole fiber morphology. While blending PAN with gelatin to gain highly porous nanofibers has been reported a few times in the literature, no attempts have been made yet to stabilize and carbonize these fibers. This paper reports on the first tests of stabilizing PAN/gelatin nanofibers, depicting the impact of different stabilization temperatures and heating rates on the chemical properties as well as the morphologies of the resulting nanofiber mats. Similar to stabilization of pure PAN, a stabilization temperature of 280°C seems suitable, while the heating rate does not significantly influence the chemical properties. Compared to stabilization of pure PAN nanofiber mats, approximately doubled heating rates can be used for PAN/gelatin blends without creating undesired conglutinations, making this base material more suitable for industrial processes.

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Stabilization and Incipient Carbonization of Electrospun Polyacrylonitrile Nanofibers Fixated on Aluminum Substrates

Fibers ◽

10.3390/fib8090055 ◽

2020 ◽

Vol 8 (9) ◽

pp. 55

Author(s):

Jan Lukas Storck ◽

Timo Grothe ◽

Khorolsuren Tuvshinbayar ◽

Elise Diestelhorst ◽

Daria Wehlage ◽

...

Keyword(s):

Chemical Properties ◽

Electrospun Nanofibers ◽

Fiber Morphology ◽

Oxidative Stabilization ◽

Simple Method ◽

Carbonization Process ◽

Aluminum Substrates ◽

Physical And Chemical ◽

The Impact ◽

Subsequent Stabilization

Polyacrylonitrile (PAN) nanofibers, prepared by electrospinning, are often used as a precursor for carbon nanofibers. The thermal carbonization process necessitates a preceding oxidative stabilization, which is usually performed thermally, i.e., by carefully heating the electrospun nanofibers in an oven. One of the typical problems occurring during this process is a strong deformation of the fiber morphologies—the fibers become thicker and shorter, and show partly undesired conglutinations. This problem can be solved by stretching the nanofiber mat during thermal treatment, which, on the other hand, can lead to breakage of the nanofiber mat. In a previous study, we have shown that the electrospinning of PAN on aluminum foils and the subsequent stabilization of this substrate is a simple method for retaining the fiber morphology without breaking the nanofiber mat. Here, we report on the impact of different aluminum foils on the physical and chemical properties of stabilized PAN nanofibers mats, and on the following incipient carbonization process at a temperature of max. 600 °C, i.e., below the melting temperature of aluminum.

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Stabilization of polyacrylonitrile nanofiber mats obtained by needleless electrospinning using dimethyl sulfoxide as solvent

Journal of Industrial Textiles ◽

10.1177/1528083718825315 ◽

2019 ◽

Vol 50 (2) ◽

pp. 224-239 ◽

Cited By ~ 13

Author(s):

Lilia Sabantina ◽

Michaela Klöcker ◽

Martin Wortmann ◽

José Rodríguez Mirasol ◽

Tomás Cordero ◽

...

Keyword(s):

Dimethyl Sulfoxide ◽

Base Material ◽

Thermochemical Conversion ◽

Original Material ◽

Optimal Stabilization ◽

Spatial Features ◽

Electrospinning Method ◽

Stabilization Temperature ◽

Nanofiber Mats ◽

First Time

Polyacrylonitrile can be used as a base material for thermochemical conversion into carbon. Especially nanofiber mats, produced by electrospinning, are of interest to create carbon nanofibers. Optimal stabilization and carbonization parameters, however, strongly depend on the spatial features of the original material. While differences between nano- and microfibers are well known, this paper shows that depending on the electrospinning method and the solvent used, considerable differences between various nanofiber mats have to be taken into account for the optimization of the stabilization conditions. Here, we examine for the first time polyacrylonitrile nanofiber mats, electrospun with wire electrospinning from the low-toxic dimethyl sulfoxide as a solvent, instead of the typically used needle electrospinning from the toxic dimethylformamide. Additionally, we used inexpensive polyacrylonitrile from knitting yarn instead of highly specialized material, tailored for carbonization. Our results show that by carefully controlling the maximum stabilization temperature and especially the heating rate, fully stabilized polyacrylonitrile fibers without undesired interconnections can be created as precursors for carbonization.

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Water Vapor Permeability through PAN Nanofiber Mat with Varying Membrane-Like Areas

Fibres and Textiles in Eastern Europe ◽

10.5604/01.3001.0012.7502 ◽

2019 ◽

Vol 27 (1(133)) ◽

pp. 12-15 ◽

Cited By ~ 7

Author(s):

Lilia Sabantina ◽

Lubos Hes ◽

José Rodríguez Mirasol ◽

Tomás Cordero ◽

...

Keyword(s):

Water Vapor ◽

High Voltage ◽

Water Vapor Permeability ◽

Vapor Permeability ◽

High Voltage Electrode ◽

Vapour Permeability ◽

Thin Membranes ◽

Nanofiber Mats ◽

The Impact ◽

Pan Nanofiber

Electrospinning can be used to create nanofiber mats from diverse polymers which can be used as filters etc. Depending on the spinning parameters, also nano-membranes, i.e. non-fibrous mats, can be produced as well as mixtures from both morphologies. The ratio of membrane to fibrous areas can be tailored by the distance between the high voltage electrode and substrate. Here the impact of the mat morphology on the water vapour permeability through polyacrylonitrile nanofiber mats with different membrane-like areas is shown, allowing for tailoring the permeability between 0.1 Pa · m²/W and more than 10 Pa · m²/W. In this way it is possible to create the finest filters as well as nearly impenetrable thin membranes with the same technology.

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Stabilization and Carbonization of PAN Nanofiber Mats Electrospun on Metal Substrates

C – Journal of Carbon Research ◽

10.3390/c7010012 ◽

2021 ◽

Vol 7 (1) ◽

pp. 12

Author(s):

Jan Lukas Storck ◽

Bennet Brockhagen ◽

Timo Grothe ◽

Lilia Sabantina ◽

Bernhard Kaltschmidt ◽

...

Keyword(s):

Carbon Nanofibers ◽

Chemical Properties ◽

Substrate Material ◽

Metal Foil ◽

Sem Images ◽

Additional Equipment ◽

Nanofiber Mats ◽

Physical And Chemical ◽

Pan Nanofiber ◽

And Chemical Properties

Polyacrylonitrile (PAN) nanofiber mats are typical precursors for carbon nanofibers. They can be fixed or even elongated during stabilization and subsequent carbonization to gain straight, mechanically robust carbon nanofibers. These processes necessitate additional equipment or are—if the nanofiber mats are just fixed at the edges—prone to resulting in the specimens breaking, due to an uneven force distribution. Hence, we showed in a previous study that electrospinning PAN on aluminum foils and stabilizing them fixed on these substrates, is a suitable solution to keep the desired morphology after stabilization and incipient carbonization. Here, we report on the influence of different metallic and semiconductor substrates on the physical and chemical properties of the nanofiber mats after stabilization and carbonization at temperatures up to 1200 °C. For stabilization on a metal substrate, an optimum stabilization temperature of slightly above 240 °C was found, approached with a heating rate of 0.25 K/min. Independent from the substrate material, SEM images revealed less defect fibers in the nanofiber mats stabilized and incipiently carbonized on a metal foil. Finally, high-temperature carbonization on different substrates is shown to allow for producing metal/carbon nano-composites.

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The Impact of Bioconjugation on the Interfacial Activity of a Protein Biosurfactant

10.26434/chemrxiv.7497053.v1 ◽

2018 ◽

Author(s):

Hossam H Tayeb ◽

Marina Stienecker ◽

Anton Middelberg ◽

Frank Sainsbury

Keyword(s):

Polyethylene Glycol ◽

Colloidal Stability ◽

Point Mutations ◽

Pharmaceutical Formulations ◽

Industrial Processes ◽

Parent Molecule ◽

Site Specific ◽

Interfacial Activity ◽

Surface Active ◽

The Impact

Biosurfactants, are surface active molecules that can be produced by renewable, industrially scalable biologic processes. DAMP4, a designer biosurfactant, enables the modification of interfaces via genetic or chemical fusion to functional moieties. However, bioconjugation of addressable amines introduces heterogeneity that limits the precision of functionalization as well as the resolution of interfacial characterization. Here we designed DAMP4 variants with cysteine point mutations to allow for site-specific bioconjugation. The DAMP4 variants were shown to retain the structural stability and interfacial activity characteristic of the parent molecule, while permitting efficient and specific conjugation of polyethylene glycol (PEG). PEGylation results in a considerable reduction on the interfacial activity of both single and double mutants. Comparison of conjugates with one or two conjugation sites shows that both the number of conjugates as well as the mass of conjugated material impacts the interfacial activity of DAMP4. As a result, the ability of DAMP4 variants with multiple PEG conjugates to impart colloidal stability on peptide-stabilized emulsions is reduced. We suggest that this is due to constraints on the structure of amphiphilic helices at the interface. Specific and efficient bioconjugation permits the exploration and investigation of the interfacial properties of designer protein biosurfactants with molecular precision. Our findings should therefore inform the design and modification of biosurfactants for their increasing use in industrial processes, and nutritional and pharmaceutical formulations.

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The Impact of Filler Geometry on Polylactic Acid-Based Sustainable Polymer Composites

Molecules ◽

10.3390/molecules26010149 ◽

2020 ◽

Vol 26 (1) ◽

pp. 149

Author(s):

Karol Leluk ◽

Stanisław Frąckowiak ◽

Joanna Ludwiczak ◽

Tomasz Rydzkowski ◽

Vijay Kumar Thakur

Keyword(s):

Polymer Composites ◽

Polylactic Acid ◽

Matrix Material ◽

Chemical Properties ◽

Precipitated Calcium Carbonate ◽

Cellulose Fibres ◽

Shape Factors ◽

Pure Cellulose ◽

Physico Chemical ◽

The Impact

Recently, biocomposites have emerged as materials of great interest to the scientists and industry around the globe. Among various polymers, polylactic acid (PLA) is a popular matrix material with high potential for advanced applications. Various particulate materials and nanoparticles have been used as the filler in PLA based matrix. One of the extensively studied filler is cellulose. However, cellulose fibres, due to their hydrophilic nature, are difficult to blend with a hydrophobic polymer matrix. This leads to agglomeration and creates voids, reducing the mechanical strength of the resulting composite. Moreover, the role of the various forms of pure cellulose and its particle shape factors has not been analyzed in most of the current literature. Therefore, in this work, materials of various shapes and shape factors were selected as fillers for the production of polymer composites using Polylactic acid as a matrix to fill this knowledge gap. In particular, pure cellulose fibres (three types with different elongation coefficient) and two mineral nanocomponents: precipitated calcium carbonate and montmorillonite were used. The composites were prepared by a melt blending process using two different levels of fillers: 5% and 30%. Then, the analysis of their thermomechanical and physico-chemical properties was carried out. The obtained results were presented graphically and discussed in terms of their shape and degree of filling.

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Ice Coverage Induced by Depositing a Water Drop onto the Supercooled Substrate at Extreme Low Vapor Pressure

Crystals ◽

10.3390/cryst11060691 ◽

2021 ◽

Vol 11 (6) ◽

pp. 691

Author(s):

Yugang Zhao ◽

Zichao Zuo ◽

Haibo Tang ◽

Xin Zhang

Keyword(s):

Vapor Pressure ◽

Substrate Temperature ◽

Water Drop ◽

Industrial Processes ◽

Aircraft Icing ◽

Ice Coverage ◽

Fundamental Understanding ◽

Order Of Magnitude ◽

The Impact ◽

Kinetics Of

Icing/snowing/frosting is ubiquitous in nature and industrial processes, and the accretion of ice mostly leads to catastrophic consequences. The existing understanding of icing is still limited, particularly for aircraft icing, where direct observation of the freezing dynamics is inaccessible. In this work, we investigate experimentally the impact and freezing of a water drop onto the supercooled substrate at extremely low vapor pressure, to mimic an aircraft passing through clouds at a relatively high altitude, engendering icing upon collisions with pendant drops. Special attention is focused on the ice coverage induced by an impinging drop, from the perimeter pointing outward along the radial direction. We observed two freezing regimes: (I) spread-recoil-freeze at the substrate temperature of Ts = −15.4 ± 0.2 °C and (II) spread (incomplete)-freeze at the substrate temperature of Ts = −22.1 ± 0.2 °C. The ice coverage is approximately one order of magnitude larger than the frozen drop itself, and counterintuitively, larger supercooling yields smaller ice coverage in the range of interest. We attribute the variation of ice coverage to the kinetics of vapor diffusion in the two regimes. This fundamental understanding benefits the design of new anti-icing technologies for aircraft.

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The impact of acid hydrolysis conditions on carbohydrate determination in lignocellulosic materials: a case study with Eucalyptus globulus bark

Holzforschung ◽

10.1515/hf-2020-0250 ◽

2021 ◽

Vol 0 (0) ◽

Author(s):

Ricardo Jorge Oliveira ◽

Bruna Santos ◽

Maria J. Mota ◽

Susana R. Pereira ◽

Pedro C. Branco ◽

...

Keyword(s):

Acid Hydrolysis ◽

Eucalyptus Globulus ◽

Industrial Processes ◽

Lignocellulosic Materials ◽

Optimal Conditions ◽

Hydrolysis Conditions ◽

The Impact ◽

Eucalyptus Bark

Abstract Lignocellulosic biomass represents a suitable feedstock for production of biofuels and bioproducts. Its chemical composition depends on many aspects (e.g. plant source, pre-processing) and it has impact on productivity of industrial bioprocesses. Numerous methodologies can be applied for biomass characterisation, with acid hydrolysis being a particularly relevant step. This study intended to assess the most suitable procedures for acid hydrolysis, taking Eucalyptus globulus bark as a case study. For that purpose, variation of temperature (90–120 °C) was evaluated over time (0–5 h), through monosaccharides and oligosaccharides contents and degradation. For glucose, the optimal conditions were 100 °C for 2.5 h, reaching a content of 48.6 wt.%. For xylose, the highest content (15.2 wt.%) was achieved at 90 °C for 2 h, or 120 °C for 0.5 h. Maximum concentrations of mannose and galactose (1.0 and 1.7 wt.%, respectively) were achieved at 90 and 100 °C (2–3.5 h) or at 120 °C (0.5–1 h). These results revealed that different hydrolysis conditions should be applied for different sugars. Using this approach, total sugar quantification in eucalyptus bark was increased by 4.3%, which would represent a 5% increase in the ethanol volume produced, considering a hypothetical bioethanol production yield. This reflects the importance of feedstock characterization on determination of economic viability of industrial processes.

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Assessment of Pellets from Three Forest Species: From Raw Material to End Use

Forests ◽

10.3390/f12040447 ◽

2021 ◽

Vol 12 (4) ◽

pp. 447

Author(s):

Miguel Alfonso Quiñones-Reveles ◽

Víctor Manuel Ruiz-García ◽

Sarai Ramos-Vargas ◽

Benedicto Vargas-Larreta ◽

Omar Masera-Cerutti ◽

...

Keyword(s):

Chemical Properties ◽

Ash Content ◽

Hot Water ◽

Raw Material ◽

Chemical Components ◽

Energy Yield ◽

Cellulose Content ◽

Fixed Carbon ◽

End Use ◽

The Impact

This study aimed to evaluate and compare the relationship between chemical properties, energy efficiency, and emissions of wood and pellets from madroño Arbutus xalapensis Kunth, tázcate Juniperus deppeana Steud, and encino colorado Quercus sideroxyla Humb. & Bonpl. in two gasifiers (top-lit-up-draft (T-LUD) and electricity generation wood camp stove (EGWCS)) in order to determine the reduction of footprint carbon. In accordance with conventional methodologies, we determined the extracts and chemical components (lignin, cellulose, holocellulose), and the immediate analyses were carried out (volatile materials, fixed carbon, ash content and microanalysis of said ash), as well as the evaluation of emission factors (total suspended particulate matter (PM2.5), CO, CO2, CH4, black carbon (BC), elemental carbon (EC), and organic carbon (OC)). The results were statistically analyzed to compare each variable among species and gasifiers. The raw material analyzed showed how the pH ranged from 5.01 to 5.57, and the ash content ranged between 0.39 and 0.53%. The content values of Cu, Zn, Fe, Mg, and Ca ranged from 0.08 to 0.22, 0.18 to 0.19, 0.38 to 0.84, 1.75 to 1.90, and 3.62 to 3.74 mg kg−1, respectively. The extractive ranges from cyclohexane were 2.48–4.79%, acetone 2.42–4.08%, methanol 3.17–7.99%, and hot water 2.12–4.83%. The range of lignin was 18.08–28.60%. The cellulose content ranged from 43.30 to 53.90%, and holocellulose from 53.50 to 64.02%. The volatile material range was 81.2–87.42%, while fixed carbon was 11.30–17.48%; the higher heating value (HHV) of raw material and pellets presented the ranges 17.68–20.21 and 19.72–21.81 MJ kg−1, respectively. Thermal efficiency showed statistically significant differences (p < 0.05) between pellets and gasifiers, with an average of 31% Tier 3 in ISO (International Organization for Standardization) for the T-LUD and 14% (ISO Tier 1) for EGWCS, with Arbutus xalapensis being the species with the highest energy yield. The use of improved combustion devices, as well as that of selected raw material species, can reduce the impact of global warming by up to 33% on a cooking task compared to the three-stone burner.

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The impact of orally administered gadolinium orthovanadate GdVO4:Eu3+ nanoparticles on the state of phospholipid bilayer of erythrocytes

Turkish Journal of Biochemistry ◽

10.1515/tjb-2019-0427 ◽

2020 ◽

Vol 45 (4) ◽

pp. 389-395

Author(s):

Anton Tkachenko ◽

Anatolii Onishchenko ◽

Vladimir Klochkov ◽

Nataliya Kavok ◽

Oksana Nakonechna ◽

...

Keyword(s):

Fluorescent Probes ◽

Lipid Membranes ◽

Chemical Properties ◽

Proton Donor ◽

The State ◽

Phospholipid Bilayer ◽

Erythrocyte Membranes ◽

Control Group ◽

Donor Ability ◽

The Impact

AbstractObjectivesTo assess the state of phospholipid bilayer of red blood cells (RBCs) in rats orally exposed to gadolinium orthovanadate GdVO4:Eu3+ nanoparticles (VNPs) during two weeks using fluorescent probes − ortho-hydroxy derivatives of 2,5-diaryl-1,3-oxazole.MethodsSteady-state fluorescence spectroscopy: a study by the environment-sensitive fluorescent probes − 2-(2′-OH-phenyl)-5-phenyl-1,3-oxazole (probe O1O) and 2-(2′-OH-phenyl)-phenanthro[9,10]-1,3-oxazole (probe PH7).ResultsNo significant changes are detected in the spectra of the fluorescent probes bound to the RBCs from the rats orally exposed to nanoparticles in comparison with the corresponding spectra of the probes bound to the cells from the control group of animals. This indicates that, in case of the rats orally exposed to nanoparticles, no noticeable changes in physico-chemical properties (i.e., in the polarity and the proton-donor ability) are observed in the lipid membranes of RBCs in the region, where the probes locate.ConclusionsNo changes in the physical and chemical properties of the erythrocyte membranes are detected in the region from glycerol backbones of phospholipids to the center of the phospholipid bilayer in the rats orally exposed to VNPs during 2 weeks.

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