scholarly journals Biobased Dyes as Conductive Additives to Reduce the Diameter of Polylactic Acid Fibers during Melt Electrospinning

Materials ◽  
2020 ◽  
Vol 13 (5) ◽  
pp. 1055 ◽  
Author(s):  
Kylie Koenig ◽  
Naveen Balakrishnan ◽  
Stefan Hermanns ◽  
Fabian Langensiepen ◽  
Gunnar Seide
Keyword(s):  
Polylactic Acid ◽  
Fiber Diameter ◽  
High Surface ◽  
High Surface Area ◽  
Degree Of Crystallinity ◽  
Environmentally Sustainable ◽  
Melt Electrospinning ◽  
Conductive Additives ◽  
Fiber Deposition ◽  
Environmentally Friendly Process

Electrospinning is widely used for the manufacture of fibers in the low-micrometer to nanometer range, allowing the fabrication of flexible materials with a high surface area. A distinction is made between solution and melt electrospinning. The former produces thinner fibers but requires hazardous solvents; whereas the latter is more environmentally sustainable because solvents are not required. However, the viscous melt requires high process temperatures and its low conductivity leads to thicker fibers. Here, we describe the first use of the biobased dyes alizarin; hematoxylin and quercetin as conductive additives to reduce the diameter of polylactic acid (PLA) fibers produced by melt electrospinning; combined with a biobased plasticizer to reduce the melt viscosity. The formation of a Taylor cone followed by continuous fiber deposition was observed for all PLA compounds; reducing the fiber diameter by up to 77% compared to pure PLA. The smallest average fiber diameter of 16.04 µm was achieved by adding 2% (w/w) hematoxylin. Comparative analysis revealed that the melt-electrospun fibers had a low degree of crystallinity compared to drawn filament controls—resembling partially oriented filaments. Our results form the basis of an economical and environmentally friendly process that could ultimately, provide an alternative to industrial solution electrospinning

Microstructural factors influencing the properties of high surface area molybdenum nitride films converted from molybdenum trioxide films deposited via solution spray pyrolysis

1998 ◽  
Vol 13 (8) ◽  
pp. 2237-2244 ◽  
Author(s):  
S. L. Roberson ◽  
D. Finello ◽  
R. F. Davis
Keyword(s):  
Grain Size ◽  
Spray Pyrolysis ◽  
Surface Area ◽  
Molybdenum Trioxide ◽  
High Surface ◽  
High Surface Area ◽  
Degree Of Crystallinity ◽  
Molybdenum Nitride ◽  
Ambient Conditions ◽  
Average Grain Size

Molybdenum trioxide (MoO3) films, 15 µm thick, have been deposited on 50 µm thick polycrystalline titanium substrates from 250 to 500 °C via liquid spray pyrolysis. Molybdenum pentachloride (MoCl5) dissolved in methanol was used as the molybdenum source; ambient conditions provided the oxygen source. X-ray diffraction (XRD) data indicated that amorphous MoO3 films were produced at deposition temperatures below 400 °C. Randomly orientated polycrystalline MoO3 films were produced at 400 °C and higher deposition temperatures. The deposition temperature also influenced the surface area of the films and their average grain size. Subsequent conversion of the MoO3 films to high surface area (HSA) conductive films containing both γ–Mo2N and δ–MoN was accomplished via programmed reactions with anhydrous NH3 and involved the formation of MoO2 and MoOxN1−x as intermediate phases. The degree of crystallinity, surface area, and average grain size of the MoO3 films strongly influenced the average grain size and surface area of the resultant MoxN films.

The effect of additives and process parameters on the pilot-scale manufacturing of polylactic acid sub-microfibers by melt electrospinning

2020 ◽  
Vol 90 (17-18) ◽  
pp. 1948-1961
Author(s):  
Kylie Koenig ◽  
Stefan Hermanns ◽  
Jacqueline Ellerkmann ◽  
Katie Saralidze ◽  
Fabian Langensiepen ◽  
...  
Keyword(s):  
Polylactic Acid ◽  
Fiber Diameter ◽  
Sodium Stearate ◽  
Polymer Degradation ◽  
Pilot Scale ◽  
Laboratory Scale ◽  
Average Fiber Diameter ◽  
Pump Speed ◽  
Melt Electrospinning ◽  
Spin Pump

Sub-microfibers are polymer filaments less than 1 µm in diameter that can be fabricated into highly flexible materials with a large specific surface area. They are often produced by solvent or melt electrospinning. The former is a scalable process that produces thinner fibers but requires hazardous solvents, whereas the latter is more environmentally sustainable due to the absence of solvents but is more challenging to scale up. Here we investigated the manufacturing of biobased polylactic acid (PLA) sub-microfibers by melt electrospinning using a single-nozzle laboratory-scale device and a novel 600-nozzle pilot-scale device combined with conductive and viscosity-reducing additives: sodium stearate (NaSt), sodium chloride (NaCl) and a polyester-based plasticizer. We determined the effect of different additive concentrations on fiber diameter, thermal properties, polymer degradation, and fiber deposition. At the laboratory scale, the minimum average fiber diameter (16.44 µm) was accomplished by adding 2% (w/w) NaCl, but a stable spinning process was not achieved and the plasticizer did not reduce the melt viscosity. NaSt was the most effective additive in terms of adapting the material properties of PLA for melt electrospinning, but extensive polymer degradation occurred at higher temperatures and with higher concentrations of the additive. At the pilot-scale, the minimum average fiber diameter (3.77 µm) was achieved by adding 6% (w/w) NaSt, with a spinneret temperature of 195℃ and a spin pump speed of 0.5 rpm (0.16 cm3), without further improvements such as the integration of a heating chamber. The smallest single-fiber diameter (1.23 µm) was achieved under the same conditions but using a spin pump speed of 2 rpm. The scaled-up melt-electrospinning device therefore offers significant potential for the production of biobased sub-microfibers, bridging the gap between laboratory-scale and pilot-scale manufacturing.

scholarly journals Synthetic Approaches for Accessing Rare-Earth Analogues of UiO-66

2021 ◽  
Author(s):  
P. Rafael Donnarumma ◽  
Sahara Frojmovic ◽  
Hudson de Aguiar Bicalho ◽  
Hatem M. Titi ◽  
Ashlee J Howarth
Keyword(s):  
Thermal Stability ◽  
Rare Earth ◽  
Surface Area ◽  
High Surface ◽  
High Surface Area ◽  
Degree Of Crystallinity ◽  
Synthetic Approaches ◽  
High Degree ◽  
First Time

Rare-earth (RE) analogues of UiO-66 with non-functionalised 1,4-benzenedicarboxylate linkers are synthesised for the first time, and a series of synthetic approaches is provided to troubleshoot the synthesis. RE-UiO-66 analogues are fully characterised, and demonstrate a high degree of crystallinity, high surface area and thermal stability, consistent with the UiO-66 archetype.

scholarly journals Synthetic Approaches for Accessing Rare-Earth Analogues of UiO-66

2021 ◽  
Author(s):  
P. Rafael Donnarumma ◽  
Sahara Frojmovic ◽  
Hudson de Aguiar Bicalho ◽  
Hatem M. Titi ◽  
Ashlee J Howarth
Keyword(s):  
Thermal Stability ◽  
Rare Earth ◽  
Surface Area ◽  
High Surface ◽  
High Surface Area ◽  
Degree Of Crystallinity ◽  
Synthetic Approaches ◽  
High Degree ◽  
First Time

Rare-earth (RE) analogues of UiO-66 with non-functionalised 1,4-benzenedicarboxylate linkers are synthesised for the first time, and a series of synthetic approaches is provided to troubleshoot the synthesis. RE-UiO-66 analogues are fully characterised, and demonstrate a high degree of crystallinity, high surface area and thermal stability, consistent with the UiO-66 archetype.

scholarly journals Nanostructured Ni Based Anode and Cathode for Alkaline Water Electrolyzers

Energies ◽  
2019 ◽  
Vol 12 (19) ◽  
pp. 3669 ◽  
Author(s):  
Fabrizio Ganci ◽  
Tracy Baguet ◽  
Giuseppe Aiello ◽  
Valentino Cusumano ◽  
Philippe Mandin ◽  
...  
Keyword(s):  
Fossil Fuels ◽  
High Surface ◽  
High Surface Area ◽  
Co2 Concentration ◽  
Cobalt Nanowires ◽  
Stable Performance ◽  
Electrochemical Water Splitting ◽  
Environmentally Friendly Process ◽  
Very High

Owing to the progressive abandoning of the fossil fuels and the increase of atmospheric CO2 concentration, the use of renewable energies is strongly encouraged. The hydrogen economy provides a very interesting scenario. In fact, hydrogen is a valuable energy carrier and can act as a storage medium as well to balance the discontinuity of the renewable sources. In order to exploit the potential of hydrogen it must be made available in adequate quantities and at an affordable price. Both goals can be potentially achieved through the electrochemical water splitting, which is an environmentally friendly process as well as the electrons and water are the only reagents. However, these devices still require a lot of research to reduce costs and increase efficiency. An approach to improve their performance is based on nanostructured electrodes characterized by high electrocatalytic activity. In this work, we show that by using template electrosynthesis it is possible to fabricate Ni nanowires featuring a very high surface area. In particular, we found that water-alkaline electrolyzers with Ni nanowires electrodes covered by different electrocatalyst have good and stable performance at room temperature as well. Besides, the results concern nickel-cobalt nanowires electrodes for both hydrogen and oxygen evolution reaction will be presented and discussed. Finally, preliminary tests concerning the use of Ni foam differently functionalized will be shown. For each electrode, electrochemical and electrocatalytic tests aimed to establishing the performance of the electrolyzers were carried out. Long term amperostatic test carried out in aqueous solution of KOH will be reported as well.

scholarly journals Automated Nanofiber Diameter Measurement in SEM Images Using a Robust Image Analysis Method

2014 ◽  
Vol 2014 ◽  
pp. 1-6 ◽  
Author(s):  
Ertan Öznergiz ◽  
Yasar Emre Kiyak ◽  
Mustafa E. Kamasak ◽  
Isa Yildirim
Keyword(s):  
Image Analysis ◽  
Fiber Diameter ◽  
High Surface ◽  
High Surface Area ◽  
Real Data ◽  
Average Fiber Diameter ◽  
Diameter Measurement ◽  
Sem Images ◽  
Human Errors ◽  
Nanofiber Diameter

Due to the high surface area, porosity, and rigidity, applications of nanofibers and nanosurfaces have developed in recent years. Nanofibers and nanosurfaces are typically produced by electrospinning method. In the production process, determination of average fiber diameter is crucial for quality assessment. Average fiber diameter is determined by manually measuring the diameters of randomly selected fibers on scanning electron microscopy (SEM) images. However, as the number of the images increases, manual fiber diameter determination becomes a tedious and time consuming task as well as being sensitive to human errors. Therefore, an automated fiber diameter measurement system is desired. In the literature, this task is achieved by using image analysis algorithms. Typically, these methods first isolate each fiber in the image and measure the diameter of each isolated fiber. Fiber isolation is an error-prone process. In this study, automated calculation of nanofiber diameter is achieved without fiber isolation using image processing and analysis algorithms. Performance of the proposed method was tested on real data. The effectiveness of the proposed method is shown by comparing automatically and manually measured nanofiber diameter values.

Fiber Creation and Deposition on Arbitrary Surfaces With Gas-Modified Electrospinning

2019 ◽  
Author(s):  
Emily A. Kooistra-Manning ◽  
Lane G. Huston ◽  
Jack L. Skinner ◽  
Jessica M. Andriolo
Keyword(s):  
Gas Flow ◽  
High Surface ◽  
High Surface Area ◽  
Volume Ratio ◽  
Separation Distance ◽  
Element Analysis ◽  
Fiber Mats ◽  
Portable System ◽  
Fiber Deposition ◽  
Electrically Charged

Abstract Electrospinning (ES) is a manufacturing technique used for the fabrication of polymer-based nano to microscale fibers with a high surface-area-to-volume ratio. Traditional ES involves a large floor or tabletop apparatus and must include a collection substrate that is electrically charged relative to the spinneret. Here, we report a miniaturized electrospinner designed for efficiency and portability, which eliminates dependency on an electrically connected deposition surface through addition of gas flow. Using the portable system, polyethylene oxide (200k MW) fiber mats were deposited. During ES, air flow rate, separation distance, and applied voltage were varied, and resultant fiber mats were analyzed and compared for quality and dimension. Finite element analysis was used to predict fiber deposition coverage in conjunction with experimental parameters.

scholarly journals Development of Electrospun Iminochitosan for Improved Wound Healing Application

2012 ◽  
Vol 7 (2) ◽  
pp. 155892501200700 ◽  
Author(s):  
Rupesh Gajanan Nawalakhe ◽  
Samuel M. Hudson ◽  
Abdel-Fattah Mohamed Seyam ◽  
Ahmed I. Waly ◽  
Nabil Y. Abou-Zeid ◽  
...  
Keyword(s):  
Surface Area ◽  
Fiber Diameter ◽  
High Surface ◽  
High Surface Area ◽  
Electrospun Nanofibers ◽  
Inhibition Zone ◽  
Fiber Formation ◽  
Diffusion Method ◽  
Disc Diffusion Method ◽  
Electrospinning Technique

Chitosan is a well known anti-microbial polymer. It is desired to develop and evaluate chitosan based structures with high surface area using electrospun nanofibers. To explore the properties of chitosan derivatives, iminochitosan was synthesized and electrospinning of its solutions was conducted. Nanofibers were obtained from iminochitosan solutions using trifluoroacetic acid (TFA) as a solvent. Nanofiberwebs of fiber diameter range 70–400 nm were successfully obtained from 3%-8% iminochitosan solution in TFA using electrospinning technique of electric field of 2.5–6.0 kV/cm. Contact kill performance of the iminochitosan structures against a range of microbes was carried out using the disc diffusion method. The results indicate that the nanofiberwebs exhibit excellent antimicrobial behavior. It was found that the inhibition zone is affected by the iminochitosan structure parameters, namely covering power, surface area (which was affected by diameter), and basis weight. Viscosity of the solutions was determined and fiber formation was obtained in the range of 400–670cP.

In Situ microscopy of the anodic etching of silicon

1995 ◽  
Vol 53 ◽  
pp. 232-233
Author(s):  
Frances M. Ross ◽  
Peter C. Searson
Keyword(s):  
Composite Structures ◽  
High Surface ◽  
High Surface Area ◽  
Chemical Properties ◽  
Selective Etching ◽  
Silicon On Insulator ◽  
Second Phase ◽  
Porous Layers ◽  
New Class ◽  
Porous Semiconductors

Porous semiconductors represent a relatively new class of materials formed by the selective etching of a single or polycrystalline substrate. Although porous silicon has received considerable attention due to its novel optical properties1, porous layers can be formed in other semiconductors such as GaAs and GaP. These materials are characterised by very high surface area and by electrical, optical and chemical properties that may differ considerably from bulk. The properties depend on the pore morphology, which can be controlled by adjusting the processing conditions and the dopant concentration. A number of novel structures can be fabricated using selective etching. For example, self-supporting membranes can be made by growing pores through a wafer, films with modulated pore structure can be fabricated by varying the applied potential during growth, composite structures can be prepared by depositing a second phase into the pores and silicon-on-insulator structures can be formed by oxidising a buried porous layer. In all these applications the ability to grow nanostructures controllably is critical.

Electron holography of catalysts

1995 ◽  
Vol 53 ◽  
pp. 416-417
Author(s):  
A. K. Datye ◽  
D. S. Kalakkad ◽  
L. F. Allard ◽  
E. Völkl
Keyword(s):  
Heterogeneous Catalysts ◽  
High Surface ◽  
High Surface Area ◽  
Atomic Scale ◽  
Nano Particles ◽  
Phase Image ◽  
Electron Holography ◽  
Specimen Thickness ◽  
Phase Information ◽  
Particle Structure

The active phase in heterogeneous catalysts consists of nanometer-sized metal or oxide particles dispersed within the tortuous pore structure of a high surface area matrix. Such catalysts are extensively used for controlling emissions from automobile exhausts or in industrial processes such as the refining of crude oil to produce gasoline. The morphology of these nano-particles is of great interest to catalytic chemists since it affects the activity and selectivity for a class of reactions known as structure-sensitive reactions. In this paper, we describe some of the challenges in the study of heterogeneous catalysts, and provide examples of how electron holography can help in extracting details of particle structure and morphology on an atomic scale.Conventional high-resolution TEM imaging methods permit the image intensity to be recorded, but the phase information in the complex image wave is lost. However, it is the phase information which is sensitive at the atomic scale to changes in specimen thickness and composition, and thus analysis of the phase image can yield important information on morphological details at the nanometer level.

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