scholarly journals Design, Manufacturing, and Characterization of High-Performance Lightweight Bipolar Plates Based on Carbon Nanotube-Exfoliated Graphite Nanoplatelet Hybrid Nanocomposites

2012 ◽  
Vol 2012 ◽  
pp. 1-8 ◽  
Author(s):  
Myungsoo Kim ◽  
Gu-Hyeok Kang ◽  
Hyung Wook Park ◽  
Young-Bin Park ◽  
Yeon Ho Park ◽  
...  
Keyword(s):  
High Performance ◽  
Processing Parameters ◽  
Hybrid Nanocomposites ◽  
Exfoliated Graphite ◽  
Electrical Performance ◽  
Dominant Factor ◽  
Graphite Nanoplatelets ◽  
Bipolar Plates ◽  
Alternative Material

We report a study on manufacturing and characterization of a platform material for high-performance lightweight bipolar plates for fuel cells based on nanocomposites consisting of carbon nanotubes (CNTs) and exfoliated graphite nanoplatelets (xGnPs). The experiments were designed and performed in three steps. In the preexperimental stage, xGnP-epoxy composite samples were prepared at various xGnP weight percentages to determine the maximum processable nanofiller concentration. The main part of the experiment employed the statistics-based design of experiments (DOE) methodology to identify improved processing conditions and CNT : xGnP ratio for minimized electrical resistivity. In the postexperimental stage, optimized combinations of material and processing parameters were investigated. With the aid of a reactive diluent, 20 wt.% was determined to the be maximum processable carbon nanomaterial content in the epoxy. The DOE analyses revealed that the CNT : xGnP ratio is the most dominant factor that governs the electrical properties, and its implications in relation to CNT-xGnP interactions and microstructure are elucidated. In addition, samples fabricated near the optimized condition revealed that there exists an optimal CNT : xGnP ratio at which the electrical performance can be maximized. The electrical and mechanical properties of optimal samples suggest that CNT-xGnP hybrid nanocomposites can serve as an alternative material platform for affordable, lightweight bipolar plates.

Effect of exfoliated graphite nanoplatelets on thermal and heat deflection properties of kenaf polypropylene hybrid nanocomposites

2016 ◽  
Vol 36 (9) ◽  
pp. 877-889 ◽  
Author(s):  
Christopher Igwe Idumah ◽  
Azman Hassan
Keyword(s):  
Electron Microscopy ◽  
Thermal Conductivity ◽  
Thermal Stability ◽  
Heat Dissipation ◽  
Hybrid Nanocomposites ◽  
Exfoliated Graphite ◽  
Graphite Nanoplatelets ◽  
Uniform Dispersion ◽  
Thermally Conductive ◽  
And Behavior

Abstract Exfoliated graphite nanoplatelet (GNP) polypropylene (PP)/kenaf fiber (KF) hybrid nanocomposites (PP/KF/MAPP/GNP collectively presented as PKMG) were developed through melt extrusion using a co-rotating screw speed extruder. The loadings of GNPs in nanocomposites were varied from 1–5 phr and characterized for thermal conductivity, stability and behavior, morphology, and heat deflection temperature (HDT). Results revealed increasing effective thermal conductivity with increasing inclusion of GNP. This behavior was attributed to the formation of thermally conductive, interconnected, sheets of GNP which enhanced heat dissipation. Thermal stability analysis revealed high thermal residue content at 3 phr loading attributed to uniform dispersion of GNP sheets in polymer matrix and the formation of enhanced oxygen-barrier due to effective char formation. Results also revealed enhanced HDT (0.46 MPa/1.8 MPa) with increasing incorporation of GNP ascribed to high modulus and thermal stability of GNP sheets. This implies capability of material to sustain loading at high temperatures without losing its rigidity. Thermal behavior revealed increased crystallization temperature and reduced degree of crystallization with slight increase in melting temperature in the range of 2–5°C. Morphological analysis using transmission electron microscopy (TEM) and field emission scanning electron microscopy (FESEM) revealed exfoliated and uniform dispersion of graphene in matrix polymer at 3 phr loading.

Preparation and Characterization of NH2-Terminal Fibrinogen Bβ Fragments from N-DSK of Human Fibrinogen

1984 ◽  
Vol 51 (01) ◽  
pp. 016-021 ◽  
Author(s):  
S Birken ◽  
G Agosto ◽  
B Lahiri ◽  
R Canfield
Keyword(s):  
High Performance ◽  
Gel Filtration ◽  
Ion Exchange Chromatography ◽  
Exchange Chromatography ◽  
Reverse Phase ◽  
Human Fibrinogen ◽  
Human Volunteers ◽  
Cnbr Cleavage ◽  
Two Peaks

SummaryIn order to investigate the early release of NH2-terminal plasmic fragments from the Bβ chain of fibrinogen, substantial quantities of Bβ 1-42 and Bβ 1-21 are required as immunogens, as radioimmunoassay standards and for infusion into human volunteers to determine the half-lives of these peptides. Towards this end methods that employ selective proteolytic cleavage of these fragments from fibrinogen have been developed. Both the N-DSK fragment, produced by CNBr cleavage of fibrinogen, and Bβ 1-118 were employed as substrates for plasmin with the finding of higher yields from N-DSK. Bβ 1-42 and Bβ 1-21 were purified by gel filtration and ion-exchange chromatography on SP-Sephadex using volatile buffers. When the purified preparation of Bβ 1-42 was chromatographed on reverse-phase high performance liquid chromatography, two peaks of identical amino acid composition were separated, presumably due either to pyroglutamate or to amide differences.

Kinetic Adsorption of Humic Acids Mixture Obtained from Microalgae on Exfoliated Graphite Nanoplatelets

2018 ◽  
Vol 69 (1) ◽  
pp. 191-195
Author(s):  
Elena Radu ◽  
Elena Emilia Oprescu ◽  
Cristina Emanuela Enascuta ◽  
Catalina Calin ◽  
Rusandica Stoica ◽  
...  
Keyword(s):  
Humic Acid ◽  
Humic Acids ◽  
Alkali Treatment ◽  
Exfoliated Graphite ◽  
Acid Mixture ◽  
Acidic Ph ◽  
Graphite Nanoplatelets ◽  
Mixture Concentration ◽  
Ft Ir ◽  
Exfoliated Graphite Nanoplatelets

The dehydration of polysaccharides fraction in the presence of acid catalysts, is a chemical process in which results as secondary product humic matter. In our work, the humic acid mixture was for the first time based on our knowledge extracted from defatted microalgae biomass rich in polysaccharides by standard alkali treatment, followed by precipitation at acidic pH. The dried humic acid mixture has been characterized using infrared spectroscopic measurements (FT-IR). Exfoliated graphite nanoplatelets (xGnP) were used as new adsorbents for this type of humic acids mixture, their adsorption being investigated. The effect of several parameters such as: contact time, concentration of humic acid mixture, concentration of xGnP, temperature and pH of the solutions were studied. The process of adsorption took place with good results, in the following conditions: at a concentration of humic acid mixture of 18.6 mg L-1, an xGnP amount of 0.01 mg in 25 mL of solution, at a temperature of 25 �� and at acidic pH values, in aqueous solution.

Preparation and Characterization of the High Molecular Weight [3H]Hyaluronic Acid

1992 ◽  
Vol 57 (10) ◽  
pp. 2151-2156 ◽  
Author(s):  
Peter Chabreček ◽  
Ladislav Šoltés ◽  
Hynek Hradec ◽  
Jiří Filip ◽  
Eduard Orviský
Keyword(s):  
Molecular Weight ◽  
Hyaluronic Acid ◽  
High Molecular Weight ◽  
Methyl Bromide ◽  
High Performance ◽  
Hydrogen Atoms ◽  
Isolation And Characterization ◽  
Labelling Procedure ◽  
Enzymatic Depolymerization

Two methods for the preparation of high molecular weight [3H]hyaluronic acid were investigated. In the first one, hydrogen atoms in the molecule were replaced by tritium. This isotopic substitution was performed in aqueous solution using Pd/CaCO3 as the catalyst. In the second method, the high molecular weight hyaluronic acid was alkylated with [3H]methyl bromide in liquid ammonia at a temperature of -33.5 °C. High-performance gel permeation chromatographic separation method was used for the isolation and characterization of the high molecular weight [3H]hyaluronic acid. Molecular weight parameters for the labelled biopolymers were Mw = 128 kDa, Mw/Mn = 1.88 (first method) and Mw = 268 kDa, Mw/Mn = 1.55 (second method). The high molecular weight [3H]hyaluronic acid having Mw = 268 kDa was degraded further by specific hyaluronidase. Products of the enzymatic depolymerization were observed to be identical for both, labelled and cold biopolymer. This finding indicates that the described labelling procedure using [3H]methyl bromide does not induce any major structural rearrangements in the molecule.

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