bluuebunny/crossref_metadata_2025_split huggingface dataset:
Isolation of Adsorbent-Free Long Semiconducting Single-Walled Carbon Nanotubes Using a Hydrogen-Bonding Supramolecular Polymer
Authors: Nakashima Naotoshi , Toshimitsu Fumiyuki 
Published: February 2020

The separation/purification of semiconducting single-walled carbon nanotubes (sem-SWNTs) according to their chirality is one of the most important issues in the science and technology of carbon nanotubes[1-4]. We previously reported supramolecular coordination polymer systems [1] to achieve elimination of the sem-SWNT-extracting agents afterward, which was the first report to utilize a supramolecular system to selectively sort chemically purified sem-SWNTs not containing the used adsorbent.
The ideal form of semiconducting-single-walled carbon nanotubes (sem-SWNTs) for science and technology is long, defect-free, chirality pure and chemically pure isolated narrow diameter tubes. While various techniques to solubilize and purify sem-SWNTs have been developed, many of them targeted only chiral- or chemical-purity with sacrificing sem-SWNT intrinsic structural identities by applying long-time ultrasonication and/or chemical modifications.
Toward the ultimate purification of the sem-SWNTs, we report a mild-conditioned extraction of the sem-SWNTs using removable hydrogen-bonding supramolecular polymers (HBPs) that are consisted of dicarboxilic- or diaminopyridyl-fluorenes with ~70%-(8,6)SWNT selectivity. Replacing conventional strong sonication to a simple shaking using HPBs was found to provide a very low D/G ratio of the extracted sem-SWNTs with long (>2.0 μm) tubes, which wad determined by an atomic force microscopy observation. The HBPs were readily removed from the nanotube surfaces by an outer stimuli, such as change of solvent polarities, to provide chemically pure (8,6)-enriched sem-SWNTs. We also describe molecular mechanics calculations to provide a possible structure of the HBP-wrapped sem-SWNTs.
Such an efficient and easy extraction of the sem-SWNTs is a great advance in the chirality selective separation of SWNTs and the study is highly important since such advanced material is a promising nanomaterial in many applications.

References

[1] F. Toshimitsu, N. Nakashima, “Semiconducting Single-walled Carbon Nanotubes Sorting with a Removable Solubilizer Based on Dynamic Supramolecular Coordination Chemistry”, Nature Communications, 2014, 5, art no. 5041.
[2] F. Toshimitsu, N. Nakashima, “Hybrids of Copolymers of Fluorene and C60-carrying-carbazole with Semiconducting Single-Walled Carbon Nanotubes”, Chem. Eur. J., 2015, 21, 3359-3366.
[3] K. Akazaki, F. Toshimitsu, H. Ozawa, T. Fujigaya, N. Nakashima, “Recognition and One-pot Extraction of Right- and Left-handed Semiconducting Single-Walled Carbon Nanotube Enantiomers Using Fluorene-Binaphthol Chiral Copolymers", J. Am. Chem. Soc. 2012, 134, 12700-12707.
[4] H. Ozawa, X. Yi, T. Fujigaya, Y. Niidome, T. Asano and N. Nakashima, “Supramolecular Hybrid of Gold Nanoparticles and Semiconducting Single-Walled Carbon Nanotubes Wrapped by a Porphyrin-Fluorene Copolymer”, J. Am. Chem. Soc., 133, 14771–14777(2011).
Graphene Quantum Dots Prepared from Graphene Hydrogels Basing on Hydrothermal Method
Authors: Qin Hongyi , Gong Tao , Liu Jingling , Jin Yinhua , Cho Yujin , Shin Cheolmin , Lee Changgu , Kim Taesung 
Published: February 2020

Graphene quantum dots (GQDs) is one of the derivatives of graphene. Due to the unique spin, electronic and optical properties, GQDs has attracted much attention. Graphene is a famous 2D and zero-bandgap material, and its size can be controlled to be from several micrometers to 30 inches. In principle, the bandgap of graphene can be tuned by varying its size. GQDs, less than 20 nm, can be considered as ultra-small fragments of graphene. The bandgap of small GQDs widens due to the quantum confinement effect. GQDs become semiconductors, which makes GQDs suitable for various fields such as optoelectronic devices, sensors and bio-imaging.
Herein, we report a novel method to prepare graphene quantum dots (GQDs) from graphene hydrogels. Various methods of synthesizing GQDs have been reported, such as hydrothermal synthesis, solvothermal, electrochemical methods, microwave technology and the bottom-up method. In our study, graphene hydrogels were prepared using a hydrothermal technique. By immersion of the hydrogels in low-polarity organic solvents, GQDs were released from the hydrogels. This method did not require additional treatments such as the centrifugation, filtration and dialysis in the general hydrothermal process. These GQDs have the strongest emission at ~347 nm.
Nanostructured Carbon Fibers for the Oxygen Reduction Reaction
Authors: Martinez Ulises , Simotwo Silas , Dumont Joseph H , Mohite Aditya , Kalra Vibha , Gupta Gautam 
Published: February 2020

Despite efforts to obtain the optimal carbon electrocatalyst while taking advantage of carbon’s desirable properties, i.e. high conductivity, large surface area, and low cost, the challenge remains to create an ideal material that possesses all required properties such as durability, efficient mass-transport, anchoring sites for nucleation of nanoparticles, and catalytically active sites. In this work, we present the electrocatalytic activity of nanostructured carbon fibers (NCF) for the oxygen reduction reaction. Synthesis of NCF was achieved via a polymer templating technique of nitrogen-rich polymer (PAN) along with a rigid sacrificial polymer (Nafion®). The pyrolysis process of these precursors results in the decomposition of the sacrificial polymer resulting in the formation of intra-fiber micro/mesopores with controllable surface areas ranging from 100-1500 m2/g [1]. Our results show that depending on the porosity and surface area of the NCF, the electrocatalyst exhibits selectivity towards either the two-electron process generating hydrogen peroxide or the four-electron reduction of oxygen to water. In addition to the tunability of these materials, the controlled 3D morphology facilitating reactant and product transport, high electronic conductivity, high double layer capacitance, enhanced durability, and large concentration of heteroatom doped sites which can function as active sites or as anchors for the nucleation of metal catalyst nanoparticles make CNF an attractive alternative to replace precious metal catalysts for hydrogen peroxide production and four-electron oxygen reduction in fuel cells.
1. Tran, C. and V. Kalra, Fabrication of porous carbon nanofibers with adjustable pore sizes as electrodes for supercapacitors. Journal of Power Sources, 2013. 235: p. 289-296.
Fabrication and Characterization of Pyrrole/Multi-Walled Carbon Nanotubes Composite Electrodes
Authors: Dushatinski Thomas , Abdel-Fattah Tarek M 
Published: February 2020

Carbon based nano-materials have received a large amount of focus because of their ultra-high energy density which approaches 600 F/g. Specifically, pyrrole and graphene double layer supercapacitors have achieved the highest charge density. Their performance has been attributed to the films conductivity, surface area and low density. This study focused on fabrication of a pyrrole (Pyr)/ multi-walled carbon nanotubes (MWCNTs) composite for analysis.
Composite films were electrochemically deposited from an aqueous MWCNTs, Pyr, and sodium dodecyl sulfate (SDS) solution onto a copper substrate. After deposition the films were annealed at 230˚C for an hour, allowed to cool to room temperature, then exfoliated using tape. SEM, AFM, and ATR-FT-IR spectroscopy were performed on unexfoliated films. 4-point probe conductivity and UV-Vis transmission measurements were performed on exfoliated films.
SEM analysis (Figure 1) shows two components of the composite, MWCNTs and Pyr forming a dense mat. All three components of the precursor were present in the final film as confirmed by ATR-FT-IR spectroscopy and the films were minimally transparent in the UV-Vis region (%T<.5%). The roughness of the film from AFM was RMS = 77.1 nm. Lastly the films had low conductivity of 0.015 S/cm.
Further optimization of the precursor and deposition cycle will hopefully result in composite films with high charge density for applications in double layered capacitors.

Figure 1

Figure 1:SEM micrograph of the edge of the Pyr/ MWCNT composite film deposition.
The Effects Functionalized Graphene Nano-Particles Have on the Corrosion Inhibition of Iron and Galvanised Steel
Authors: Richards Calvin , Glover Carol , McMurray Hamilton Neil , Williams Geraint 
Published: February 2020

The ever present need to replace chromate in anti-corrosive coatings has lead to a number of alternative chemistries. Graphene is one such proposed chemistry that has garnered a large amount of interest in recent years. Ongoing studies at Swansea University have demonstrated effective corrosion-inhibition, to both iron and galvanised steel surfaces, by utilising the anti-corrosive properties of graphene nano-pigments (GNPs) dispersed within a polyvinylbutryal (PVB) carrier. In-situ scanning Kelvin probe (SKP) techniques have shown GNPs’ ability to stall and resist underfilm delamination of organic PVB systems to both iron and galvanized surfaces. Current theories attribute graphene inhibition to an electrochemical and mass-transport blocking effect.
Throughout Swansea University’s studies the GNPs have been supplied by Haydale Ltd, who produce these nano-pigments by means of graphite exfoliation. HDPlas™ GNPs, produced by Haydale, are particles of graphene that have been plasma processed to modify the surface of the nanomaterials for enhancements in application. The plasma process imparts chemical species onto the surface of the GNPs; this plasma surface modification does not penetrate into the bulk of the material, leaving the GNPs undamaged. Two of the available functionalities are carboxyl (COOH) and amines (NHx). In this study the effect that these functionalities have on the GNPs’ corrosion inhibition is examined by use of the SKP technique. The functionalized GNPs (FGNPs) are thought to have greater adhesion properties to the surfaces of the metal substrates on account of their polar structures. In order to test this hypothesis, several pigment volume fractions were tested (ranging from 5% to 25% by weight and dispersed within a PVB system) using a standard SKP setup. Figures 1 and 2 are plots of both delamination time and delamination rate versus the respective FGNP loading, coated onto iron substrates. Both demonstrate that, at concentrations >15%, both functionalized groups show an increased delay to initiation and reduced delamination rates. Despite showing similar delamination rates, the NH2 functionality shows far slower initiation times, thought to be attributed to greater adhesion and keying to the iron substrate. The benefits that functionalization of GNPs provide to overall corrosion inhibition is discussed.
Fabrication and Characterization of Superhydrophobic Poly(vinylidene fluoride-co- hexafluoropropylene)/TiO2 Nanocomposite Coating for Corrosion Protection Applications
Authors: Bahgat Ahmed , Abdullah Aboubakr Moustafa , Mohamed Adel M. A. , Almaadeed Mariam 
Published: February 2020

Superhydrophobic surfaces have a strong potential for implementation in variety of fields, including self-cleaning surfaces, biomedical and coatings for corrosion protection. Preparation of superhydrophobic surfaces requires both an optimum roughness and low surface energy; therefore, these surfaces are conventionally prepared employing two steps: roughening a surface and lowering its surface energy.
In this study, the superhydrophobic Poly(vinylidene fluoride-co-hexafluoropropylene)/TiO2 nanocomposite coatings were fabricated using a simple one-step coating method on a carbon steel substrate to study the corrosion behavior in harsh environments. The surface wettability and morphology of the prepared coatings were characterized using the sessile droplet method and scanning electron microscopy, respectively. X-ray photoelectron spectroscopy and X-ray diffractometer were used to identify the elemental composition and chemical oxidation states of the prepared surface. The surface roughness of the coatings was measured using atomic force microscope. The chemical stability of the prepared coatings was inspected by immersion the specimens in different pH solutions. The results showed that stable superhydrophobic surfaces with high water contact angle and low contact angle hysteresis can be fabricated on the carbon steel surface. As well as, the corrosion resistant performance of the produced superhydrophobic surface on carbon steel was carried out by electrochemical impedance spectroscopy (EIS) measurements and potentiodynamic polarization in 3.5 wt % NaCl solution. The electrochemical corrosion tests revealed that the as-prepared superhydrophobic surface significantly improved the corrosion resistant of the C-steel substrate.
(Keynote) The Pretreatment of 2000 Series Al Alloy: In Situ Measurement of the Selective Dissolution & Film Formation
Authors: Ogle Kevin , Gharbi Oumaïma 
Published: February 2020

The surface conditioning of aluminum alloys frequently involves a sequence of alkaline and acid pretreatments. These steps ideally provide a homogeneous surface chemistry prior to subsequent anodization or conversion treatment. However, the electrochemical properties of the intermetallic phases - such as the S-phase (Al2CuMg) or the θ-phase (Al2Cu) - are sufficiently different from the matrix that certain alloy components will be enriched on the surface due to selective dissolution and / or redeposition. The aim of this study is to quantitatively measure the selective dissolution processes and characterize the residual films that form during these pretreatment steps.
To this end, we have developed an in situ measurement of elemental dissolution during a pretreatment sequence under simulated industrial conditions using atomic emission spectroelectrochemistry (AESEC). This follows previous work on the kinetics of dealloying of the pure S and θ- phase in sulfuric acid [1]. Through a mass balance, the elemental dissolution rates also yield the quantity of residual Cu and Mg. An example of the experimental technique is shown in Figure 1 for the exposure of an AA2024 T3 alloy to a 1.2 M NaOH electrolyte at 60 °C followed by a water rinse. Shown are the Al, Mg, and Cu dissolution rates as a function of time as well as the electrochemical potential. The Al dissolution rate rises rapidly to obtain a relatively stationary value. The Cu and Mg dissolution rates are detectable but are three orders of magnitude less intense, demonstrating the strongly selective dissolution of Al. The release of Cu and Mg rich intermetallic particles during this stage is indicated by the coincident spikes of Mg and Cu.
The excess residual Cu then dissolves, at least partially, in the subsequent HNO3 electrolyte reaction (not shown here) and the Al is passivated. These results will be combined with a microscopic analysis of the surface and with conventional electrochemistry to clarify the nature of the residual films formed and their effect on the electrochemical activity of the Al alloy under simulated corrosion conditions. Additional results with Al-Cu-Li alloys and pure S and θ- phase samples will also be presented.
1) S Lebouil, J Tardelli, E Rocca, P Volovitch, K Ogle, “Dealloying of Al2Cu, Al7Cu2Fe, and Al2CuMg intermetallic phases to form nanoparticulate copper films”, Materials and Corrosion 65 (2014)416-424.

Fig. 1 Al, Cu, & Mg dissolution rates (expressed as equivalent currents) and the electrochemical potential during the exposure of AA2024 T3 alloy to a 1.2 M NaOH at 60 °C. Intermetallic Cu and Mg rich particles detach from the surface giving rise to the spikes in the Cu and Mg signals.

Figure 1
Al2O3 Coatings Deposited By ALD on Al Alloys
Authors: Marcus Philippe , Tao Jun , Swiatowska Jolanta , Zanna Sandrine , Seyeux Antoine , Harkonen Emma , Ritala Mikko 
Published: February 2020

The key question that was addressed in this work is the following: would a uniform surface layer of aluminium oxide on aluminium alloys be protective against corrosion despite the presence of intermetallic Al-Cu particles?
To answer this question, well defined aluminium oxide coatings were deposited by atomic layer deposition (ALD) on the surface of a model binary aluminium-copper alloy (Al-Cu5%wt.) in which copper-rich particles were produced by ageing.
The corrosion resistance of uncoated, mechanically polished aluminium alloy samples covered by a native oxide layer was compared with the one of aluminium alloy samples protected by a 20 nm thick Al2O3 layer deposited by Atomic Layer Deposition (ALD). Detailed surface analysis was performed by X-ray Photoelectron Spectroscopy (XPS), Time-of-Flight Secondary Ion Mass Spectrometry (ToF-SIMS) and Scanning Electron Microscopy (SEM) on the samples before and after immersion in 0.01M NaCl + 0.3 % vol. H2O2 (pH=6.2).
The polished Al-Cu alloy with a thin native oxide layer (around 5 nm, as measured by XPS), exhibits a copper enrichment at the oxide/Al alloy interface, clearly evidenced by ToF-SIMS depth profiling. The ToF-SIMS chemical images and EDX analysis confirmed the presence of copper-rich intermetallics (Al2Cu) in the interfacial oxide/substrate region. A short immersion (~7 min) of this alloy in a near neutral NaCl solution lead to severe surface modifications: formation of mixed aluminium-copper oxide layer rich in CuO and Cu(OH)2 (as shown by XPS), and formation of an inhomogeneous, thick aluminium oxide deposit (as shown by SEM and ToF-SIMS imaging). Localized corrosion in the vicinity of the intermetallic particles (well known as trenching around particles) is clearlyobserved by SEM and ToF-SIMS imaging.
A significant improvement on corrosion resistance was observed after deposition of the 20 nm-thick Al2O3 ALD coating. Despite the presence of intermetallics at the oxide/substrate interface (observed in the SEM) no significant corrosion occurred in the chloride solution, the Al2Cu particles remained intact, and no trenching around them was observed.
In conclusion, the formation of a good quality alumina layer on the Al-5%Cu alloy is beneficial for its corrosion resistance. The coating can be deposited by ALD without prior removal of the intermetallic particles.
Atmospheric Corrosion of Zinc Coated Steel- Results from a Worldwide Outdoor Exposure Program
Authors: Thierry Dominique , Persson Dan 
Published: February 2020

In the last decades, numerous national or international exposure programs have been launched to collect data on atmospheric corrosion rates and to establish prediction tools for atmospheric corrosion of metallic structures [1]. Most commonly, carbon steel, zinc, copper and aluminum samples are exposed in selected locations for a year or more. Based on weight loss measurements, dose-response functions and corrosivity maps have been compiled [2,3]. A major limitation of most previous studies is that data have been acquired mainly for bulk metals while studies on metallic coatings are rare. Similarly, the evolution of corrosion products with exposure time has been studied for bulk zinc [4] but few studies on zinc coated steel is reported.
This work is a part of a larger research program were steel with different zinc coatings are exposed on a worldwide basis on well characterized exposure sites in Europe, Asia and North America, see table 1. Corrosion rates of HDG were determined after exposure under different climatic conditions. Corrosion rates for HDG after two years exposure have been measred. Uniformity of the coating corrosion and performance at cut edges was evaluated. The effect of sample orientation and sheltering was investigated. Correlation of data on mass loss with environmental data collected at the exposures sites enabled the derivation of dose-response function HDG.
The formation and development of corrosion products was followed by detailed analysis of samples exposed 0.5, 1 and 2 years using XRD, FTIR-spectroscopy and SEM-EDS. The main corrosion products formed on HDG on the different sites are Zn5(OH)6(CO3)2, NaZn4(SO4)(OH)6Cl·6H2O, (Zn(OH)2)3 ZnSO4·5H2O and Zn5(OH)8Cl2·H2O. The type and relative amounts of different corrosion products were related to the location and type of exposure site but no systematic changes were observed with the time of exposure.
Table 1. Test sites in the exposure program

Code

Name

Country

Distance to Sea(m)

A

Brest
France
<5

B

Bohus-Malmön (I)
Sweden
<5

C

Bohus-Malmön (II)
Sweden
300

D

Ijmuiden
Netherlands
2600

E

Cadiz
Spain
750

F

Jiangjin
China
̴900 km

G

Ostrawa
Czech Republic
̴500 km

H

Dubai
UAE
2000

I

Daytona Beach
USA
100

J

Quindao
China
10

K

Wanning
China
100

L

Bangkok
Thailand
35 km

M

Sattahip
Thailand
10

N

Singapore
SIngapore
10

References
1- D. Knotkova, V. Kucera, P. Boschek: ASTM STP 1421 Outdoor Atmospheric Corrosion, pp.107, 2002

2- A. Mikhailov, J. Tidblad and V. Kucera: Protection of Metals, 40(6),pp 541-550, 2004

3- M. Morcillo, E. Almeida, B. Chico, D. De la Fuente Analysis of ISO Standard 9223
(Classification of Corrosivity of Atmospheres) in the Light of Information Obtained in the Ibero-American Micat, ASTM STP 1421 Outdoor Atmospheric Corrosion, 2002, pp. 59.
4. I. Odnevall, C. Leygraf, Atmospheric Corrosion, ASTM STP 1239, ASTM, Philadelphia, 1995, pp. 215–229
Corrosion Protection of Low Carbon Steels By Electrodeposited Aluminum Alloys
Authors: Bund Andreas , Ispas Adriana , Vlaic Codruta Aurelia , Foerg Andrea , Masset Patrick J. 
Published: February 2020

This paper will discuss recent results from the authors' labs on the corrosion protection of low carbon steels using aluminum alloys. Aluminum based layers were electrodeposited from room temperature molten salts such as mixtures of 1-ethyl-3-methyl imidazolium chloride ([EMIm]Cl) and AlCl3. These layers are promising candidates for the replacement of cadmium in aerospace applications. The effect of various process parameters (current density, alloying elements, etc.) on the microstructure and corrosion properties of the coatings will be discussed. As an example uniform and smooth deposits were obtained at current densities of approx. 6 mA/cm² from a bath containing 0.2 mol/L MnCl2. The resulting Al-Mn alloy contained 20 at-% Mn and showed excellent corrosion protection of the low carbon steel substrate.