bluuebunny/crossref_metadata_2025 huggingface dataset:
the Growth of Hierarchal Shape Tin Used As Catalysts Support Towards a Binder Free Fuel Cell Anodes
Authors: Schechter Alex , Teller Hanan , Subramanian Palaniappan , Ochanuna Shani
Published: February 2020

A novel catalyst support utilizing electrodeposited tin was investigated for direct liquid fuel cells. These materials were prepared by electrodeposition of tetragonal metallic Sn on Toray® carbon paper or gold electrodes under non-equilibrium conditions. Hierarchical shape branched dendrites of Sn were formed under selected experimental conditions (fig 1).  The growth process on these electrodes were rigorously investigated using potentiostatic or galvanostatic steps, in aqueous solutions containing sodium citrate, SDS, HTAB. Hydrogen evolution and mass balance calculations suggest that the columbic efficiency of Sn2+reduction is controlled by diffusion of the surfactant solvated ions.

Various morphologies of metallic Sn can be prepared by controlling the applied potential, duty cycle and the HCl additive. Hierarchal morphologies of Sn start to appear at an over potentials of more than 0.9V and is strongly influenced by hydrogen evolution competing reaction.

Characterization of the deposition the deposition and etching, passivation and activation processes were performed by EQCM. These results show that H2SO4 and HClO4, which were applied in the activation of SnO2 layer, prior to applying the catalyst, behave differently with the deposited metal. HClO4seems to prevent further acting of the oxide layer and provide the required functionality for metal deposition as well as good passivation required stable operation as anodes. 

Pt, PtSn and Ni catalysts were loaded on electrodeposited Sn supported on Toray® carbon paper by electroless or by electroplating processes. These binder free anodes were measured in methanol, methyl- formate acid solutions, and nickel-plated was applied in urea oxidation in alkaline solutions. Superior oxidation specific activity was observed on all Sn supported anodes with respect to Pt or Ni catalysts loaded on carbon XC72.

Figure 1. HRSEM of electrodeposited Sn in a “tree” like shape

Figure 1
Thermogalvanic Waste Heat Recovery System in Automobiles
Authors: Gunawan Andrey , Fette Nicholas W , Wilson Noah , Mujica Vladimiro , Buttry Daniel A , Phelan Patrick E
Published: February 2020

Waste heat recovery remains an inviting subject for research. Solid-state thermoelectric devices have been widely investigated, but their practical application remains challenging due to cost and inability to fabricate them in geometries that are easily compatible with heat sources. An alternative to such devices is thermogalvanic cells. Temperature difference between hot and cold electrodes creates a potential difference. Once they connect to a load, electric current and power are delivered, thus converting heat into electricity. Recent work in our laboratory has showed that an annular copper-copper sulfate thermogalvanic cell system, which was affixed conformingly onto a hot pipe to simulate car’s exhaust pipe, produced electricity in the order of tens of milliwatt per square meter. Therefore, the current study is essentially the continuation of that proof-of-concept work. We redesign and build new cells with increased electrodes’ surface area to generate more power. We also incorporate a flowing cell design to capture more waste heat from a car’s radiator. This study is a largely experimental approach to improve the power generation of the system, with the goal being to make possible future practical energy conversion devices for automotive industries.

Figure 1
High Rate Capability and Long Cycle Stability of Co3O4/CoFe2O4 nanocomposite As an Anode Material for High-Performance Secondary Lithium Ion Batteries
Authors: Pham Duong Tung , Vu Thi Trang , Gim Jihyeon , Song Jinju , Kim Sungjin , Jo Jeonggeun , Alfaruqi Muhammad Hilmy , Kim Seokhun , Park Sohyun , Kim Jaekook
Published: February 2020

A facile and cost-effective urea-assisted autocombustion strategy has been designed for the fabrication of Co3O4/CoFe2O4 nanocomposite and pure CoFe2O4 anode materials followed by annealing at 700 and 900 °C for 6 h, respectively. To confirm the exact structure, Rietiveld analysis was performed on the Synchrotron XRD pattern of both the CoFe2O4 samples annealed at 700 and 900 °C. The results clearly depicts the formation of two phases (Co3O4:CoFe2O4) with the ratio of [76.3(5):23.6(3)%] in the sample annealed at 700 °C sample, while single phase CoFe2O4 formation was observed for the sample annealed at 900 °C. It has also been found that the designed nanocomposite sample is composed of small nanoparticles (50–100 nm), while the size of pure CoFe2O4 particles is in the range from 600 nm to 1 μm. When applied as an anode material, the obtained Co3O4/CoFe2O4 nanocomposite electrode exhibits high reversible capacity as well as excellent cycling stability and better rate capability in comparison to a pure CoFe2O4 electrode. The enhanced electrochemical performance of the nanocomposite can be attributed to the intimate interconnection between Co3O4 and CoFe2O4, along with the nanosize range of particles and high surface area, which not only favor fast kinetic properties facilitating electron transportation and Li+ ion insertion/deinsertion but also relieve the stress caused by volume changes during the numerous charge/discharge cycles and suppress the degradation of the material.
All Solid State Supercapacitors Based on Ionic Liquid/Crosslinked PEO-PPO Tetrablock Copolymer Electrolytes
Authors: Han Jae Hee , Kim Tae-Ho , Hong Young Taik
Published: February 2020

Supercapacitors are widely recognized as an important class of energy storage devices, because they can provide a high specific power, long cycle life. Compared with the conventional supercapacitors using liquid electrolyte, all-solid state supercapacitors have many advantages such as lightweight, high flexibility, high safety and environmentally benign nature, which are suitable for flexible and portable electronics. The realization of high performance all solid state supercapacitors strongly depends on the electrical properties and mechanical integrity of constitutive materials and their controlled assembly of electrode and solid electrolyte. 

In this work, we designed and prepared novel ionic liquid (IL)-doped crosslinked PEO-PPO tetrablock copolymer electrolytes. Triethoxysilane-endcapped precursors were first prepared by reacting the terminal hydroxyl groups of the corresponding Tetronic® (BASF) copolymers with 3-isocyanatopropyl triethoxysilane. Then, the IL-doped and crosslinked electrolytes were fabricated via in situ sol-gel reactions of the triethoxysilane end groups of the precursors and subsequent solution casting process in the presence of IL. Despite large IL doping up to 200 wt%, solid and transparent film could be obtained mainly due to the crosslinked structure. The resulting electrolytes were denoted as cTPL-TPE-A-B, where A and B indicate the codename of Tetronic® and the content of IL doped, respectively. It was confirmed that cTPL-TPE-A-Bs possessed completely amorphous structure and non-fusible property from the XRD and DSC experiments. The Ionic conductivity of a cTPL-TPE-90R4-200 with 200 wt% BMIM-BF4 reached 3.65×10-3 S/cm at room temperature and 2.73×10-2 S/cm at 80 °C (see Figure 1). These values were more than 10 times higher than those of the PEO electrolyte with the same range of BMIM-BF4 content thanks to the entirely amorphous structure of cTPL-TPE-A-Bs.

 All-solid-state supercapacitors were fabricated assembling cTPL-TPE-A-Bs as electrolytes with graphene sheets (prepared from a kneading method) as electrodes. Consequently, the device exhibited high electrochemical performance such as high operating voltage of 3.7 V, high specific capacitance of 157.4 F/g, and an energy density of 55.3 Wh/kg (@ 10 mA/g).

Figure 1
Study on Electrochemical Performance of Thin Film C60 As an Anode Material for Lithium Secondary Batteries
Authors: Halim Martin , Lee Joong-Kee
Published: February 2020

Lithium ion batteries are gaining more attention these days since it is being used in many application, ranging from portable devices to electric vehicles due to their superior energy density and cycleability over the other energy storage technologies. Among those applications, microrobotics is also getting more attention since it can be used for exploration in small and/or dangerous environment, finding survivor in the disaster site, and defense department needs. However, there is crucial shortage from these microrobotics, which are its power source limitation. In order to overcome this limitation, special attempts should be done by designing the energy storage cell as small as possible. In order to achieve this, carbon based thin film might be one of the plausible alternative. To this end, we made a carbon based thin film using the plasma enhanced thermal evaporation deposition. Since the available commercial graphite and graphene have extremely high melting point (ca. 3600 oC and ca. 3900 oC for graphite and graphene, respectively), these materials are not applicable when used as the precursor for thin film deposition process [1]. It has been already investigated that carbon with the structure of C70 and C60 has significantly low sublimation point of ca. 850 oC and 600 oC, respectively [2]. In our experiment scope, we made the carbon based thin film electrode using C60powder.

The deposition of C60 thin films were deposited by plasma enhanced thermal evaporation. The samples were prepared under following conditions: a working pressure of 25 mTorr and deposition time of 1 min. The film thickness and RF power were varied. The film thickness was varied by introducing different amount of C60powder of 0.01 g, 0.02 g, and 0.04 g. The RF power variation was 100 W, 200 W, and 300 W.

The results show that thicker C60 thin film would result in lower volumetric capacity. This might be related to the characteristic of C60 that intrinsically high resistance. Thus, increasing the thickness might increase the resistance of the film and might also lead to longer distance for lithium to diffuse into the C60electrode. Meanwhile, the investigation of plasma power variation shows that lower plasma power results in higher volumetric capacity. These phenomena would be the focus of our detail discussion.

Reference

1. J. H. Los, K. V. Zakharchenko, M. I. Katsnelson, and A. Fasolino, Physical Review B 91, 045415 (2015).

2. Eiji Osawa (2002). Perspective of fullerene nanotechnology. Springer. pp. 275.

Figure 1
Current Response at Grain and Grain Boundaries in LiFePO4 Thin Films By Nano-Scanning Electrochemical Cell Microscopy
Authors: Kumatani Akichika , Takahashi Yasufumi , Inomata Hirotaka , Watanabe Tetsuya , Yamamoto Kuniko , Haruta Masakazu , Shiraki Susumu , Shiku Hitoshi , Hitosugi Taro , Matsue Tomokazu
Published: February 2020

Creation of high performance electrodes in rechargeable lithium-ion batteries (LIBs) is one of urgent demand to store unused energy towards low-carbon emission society. To satisfy this demand, a facile characterization technique is required for analyzing electrochemical response related to lithium-ion transport via crystal orientation or crystal boundaries in the electrodes. Recently, we have developed a single-channel nano-scanning electrochemical call microscopy (nanoSECCM).1 The nanoSECCM can obtain current response related to ion transport only as in-situ measurement with nanometer resolution. In this study, we have applied nanoSECCM to characterize the current repose at grain and grain boundaries on the LiFePO4 thin film electrode. The film is multi-domain structure with sub-micrometer grains including [010] crystal orientation, confirmed by SEM and XRD analyses. The inhomogeneity of the response at grains was visualized from nanoSECCM mapping. The response at particular grain with higher response presumably indicates that it possesses [010] crystal orientation which is known as higher current response in LiFePO4.2 We show that this analysis is a sensitive and facile measure of the influence for crystal orientation and boundaries in electrodes of LIBs.

[1] Y. Takahashi, A. Kumatani et al., Nat. Communi. 5:5450 (2014).

[2] D. Morgan et al., Electrochem. Solid State Lett. 7, A30 (2004).
Fullerene Biomaterials for PDT or MRI: Effects of Derivatization on Activities
Authors: Yamakoshi Yoko , Tiu Elisha Gabrielle V. , Aroua Safwan
Published: February 2020

Fullerene-based water-soluble materials have been considered as seed compounds for photosensitizers in photodynamic therapy (PDT) and contract reagents in magnetic resonance imaging1 (MRI). We have been working on the development of new biocompatible fullerene (C60, C70 and Gd3N@C80
2) materials by complexation with or by covalent attachment of water-soluble polymers such as poly(vinylpyrrolidone) (PVP) and polyethylene glycol (PEG). Initial studies on the C60/ or C70/PVP complex provided sufficient water-solubility and efficient generation of superoxide (O2•–).3  But a subsequent study on C60-PVP or C70-PVP copolymers (uncontrolled) resulted in slightly better water-solubility provided and improved generation of 1O2.  It appears that bioactivity of the C60 or C70 is different due to the formation of water-soluble materials in aqueous medias.  In this study, we discuss on the effect of derivatization of fullerene cores on the bioactivities including reactive oxygen species generation from bis-, tris-adducts of C60 and M3N@C80 (Figure) and well-defined fullerene-PVP copolymers that we have recently prepared5 using Prato reactions.6

(1) Zhang, J. F.; Fatouros, P. P.; Shu, C. Y.; Reid, J.; Owens, L. S.; Cai, T.; Gibson, H. W.; Long, G. L.; Corwin, F. D.; Chen, Z. J.; Dorn, H. C. Bioconjugate Chem.
2010, 21, 610.

(2) Stevenson, S.; Rice, G.; Glass, T.; Harich, K.; Cromer, F.; Jordan, M. R.; Craft, J.; Hadju, E.; Bible, R.; Olmstead, M. M.; Maitra, K.; Fisher, A. J.; Balch, A. L.; Dorn, H. C. Nature
1999, 401, 55.

(3) Yamakoshi, Y.; Umezawa, N.; Ryu, A.; Arakane, K.; Miyata, N.; Goda, Y.; Masumizu, T.; Nagano, T. J. Am. Chem. Soc. 2003, 125, 12803.

(4) Oriana, S.; Aroua, S.; Söllner, J. O. B.; Ma, X.; Iwamoto, Y.; Yamakoshi, Y. Chem. Comm. 2013, 49, 9302.

(5) a) Aroua, S.; Schweizer, W. B.; Yamakoshi, Y. Org. Lett. 2014, 16, 1688-1691. b) Aroua, S.; Garcia-Borràs, M.; Bölter M. F.;, Osuna, S.; Yamakoshi, Y. J. Am. Chem. Soc. 2015, 137, 58-61. c) Aroua, S.; Tiu, E. G. V.; Ayer, M.; Ishikawa, T.; Yamakoshi, Y. Polymer Chem. 2015, 6, 2616–2619.

(6) Maggini, M.; Scorrano, G.; Prato, M. J. Am. Chem. Soc.
1993, 115, 9798.

Figure 1
Preparation and Characterization of Porous CNTs@Fe-C Pellets
Authors: Hao Su-ju , Hao Yue-jun , Hao Hua-qiang , Jiang Wu-feng , Zhang Yu-zhu
Published: February 2020

Iron-carbon internal electrolysis method is an effective and low cost way for treating organic wastewater, but it will generate rust connection which leads failure. In order to solve the problem, CNTs have been in situ synthesized within the porous Fe-C pellets using acetone as carbon source, prepared porous CNTs@Fe-C pellets. The effects of temperature and acetone amount on the quality of CNTs in porous CNTs@Fe-C pellets have been studied. The as-prepared porous CNTs@Fe-C pellets were characterized by field emission scanning electron microscopy (FE-SEM), energy dispersive X-ray spectroscopy (EDS), X-ray diffraction (XRD) and transmission electron microscopy (TEM). The results have shown that the porous CNTs@Fe-C pellets are composed of carbon nanotubes, sponge iron and activated carbon. The proper condition that conducive to the growth of CNTs is at 700 ℃ and the ratio of acetone and porous Fe-C pellets is 3ml/g. The growth mechanism of CNTs in the pellets is for top growth model.
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.
Graphene Synthesis on Electrodeposited Substrates and Its Integration in MEMS for Sensor Applications
Authors: Pedrazzetti Lorenzo , Bernasconi Roberto , Nobili Luca , Magagnin Luca
Published: February 2020

Graphene has become a promising material for many different applications, such as nanoelectronic devices, physical, chemical and biochemical sensors, transparent conductive films, clean energy scavenging and storage devices, and nanocomposite formulations. This great variety of possibilities is determined by the exceptional charge transport, optical, and mechanical properties of the material. Recently gas sensing, as a critical application in intelligent systems, is receiving increasing attention between the possible applications in both industry and academy. Sensing applications using graphene sheets as transducers have experienced a surge of activities in recent years, especially for gas sensing platforms and electrochemical sensing, because of the high electrical conductivity and high surface area of graphene. The most intriguing feature of graphene based sensors is that a proper functionalization of graphene enables enhanced selectivity and improved performances. Moreover, by combining graphene electronic and mechanical properties monolithic sensors with superior sensitivity can be developed. Despite the significant amount of work on graphene electronic devices such as the field effect transistor, its use in sensors, actuators or micro and nano-electromechanical systems (MEMS/NEMS) in general is relatively less explored. In this work the synthesis of graphene by precursor decomposition at different temperatures onto free standing electrodeposited substrates is investigated, allowing therefore to study the effects of electrochemically produced substrates onto graphene quality. The production of porous structure obtained dealloying the electrodeposited NiCu substrates will be discussed for the synthesis of porous graphene layers. The specific area of the structure obtained is therefore greatly enhanced, improving in this way the sensing capacity. The growth of good quality graphene layers is also discussed in terms of the role played by grain boundaries and diffusion at the grain boundaries. Finally, graphene coated substrates as electrodes for electrochemical sensor and the integration of graphene layers into MEMS for microsensor production will be presented.
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.
Photocathodic Protection of TiO2 Composite Material on 304 Stainless Steel
Authors: Wang Xiutong , Li Hong , Wei Qinyi , Zhang Qiaoxia , Hou Baorong
Published: February 2020

TiO2 and other semiconductor materials were found to have photocathodic protection effect for the metal coupled with these semiconductors film, as the potential of the metal shifted to a more negative value than its corrosion potential and the corrosion of the metal was prevented. TiO2 has been one of the most important semiconductors because of its good environmental friendliness and chemical stability. However, due to the wide band gap of TiO2 (3.2 eV) and the recombination of the photogenerated electron-hole (e–-h+) pairs, it can only absorb the light with the wavelength less than 380 nm, and it is hard to maintain the cathodic protection in the dark. In this paper, CdSe and other materials were applied to improve the photocathodic protection property.

TiO2 nanotubes was prepared by anodization method, and CdSe was deposited on the TiO2 nanotube arrays by cyclic voltammetry method, and the optimum condition was selected from different cycles. The surface morphology and crystal phase of the composite was investigated by scanning electron microscopy (SEM), X ray diffraction (XRD) method.

The photocathodic protection property of the composite material for 304 stainless steel in seawater was investigated by the electrochemical method including open circuit potential (OCP), electrochemical impedance spectroscopy (EIS) and the tafel polarization curves method. The experimental results showed that open circuit potential of 304 stainless steel decreased from -190mV to -500mV when the light was turned on, and the electrode potential slowly rises to about -250mV after the light was turned off. The composite material still could maintain the protective effect on stainless steel after the light was turned off.

The work was supported by the Project of National Development and Reform Commission, the Nantong Science Project (BK2014008), and National Basic Research Program of China (2014CB643304).
Hydrogen Evolution Behavior of Dissolving Magnesium Investigated By EIS and Gas Chromatography
Authors: Takemiya Rie , Hoshi Yoshinao , Shitanda Isao , Itagaki Masayuki
Published: February 2020

An air battery is expected as a power source for the automobile and disaster battery because it has a high energy density and charge voltage. Since the magnesium is the less noble material, it is expected as a negative electrode active material of air battery. It is well known that the cathodic reaction of hydrogen evolution was occurred at magnesium surface during anodic polarization measurement of magnesium (1).  Petty et. al (1) suggested that the fraction of dissolving magnesium enters the solution as univalent magnesium (Mg+), where it is oxidized by water. Samaniego et. al (2) reproduced the  experiment performed by Petty et. al (1) and supplemented with modern in situ Raman spectroscopy. They concluded that the existence of univalent magnesium was not established by Petty et. al (1). Frankel et. al (3) suggested that the ability of magnesium to support the cathodic reaction is enhanced during the anodic dissolution as the result of an increase on the exchange current density for the hydrogen reaction. Although the mechanisms of hydrogen evolution on the magnesium surface have been suggested, reactions of the hydrogen evolution have not been clarified in detail yet. In this study, the relation between the anodic dissolution of magnesium and the hydrogen evolution occurred during anodic polarization of magnesium is investigated by the simultaneous measurements of electrochemical measurement and gas chromatography. The hydrogen evolution of the dissolving magnesium was examined by the 3D impedance measurement in 0.5 M NaCl. The amount of the hydrogen gas during anodic polarization of magnesium was detected by the gas chromatography.

References:

1. R. L. Petty, A. W. Davidson and J. Kleinberg, Journal of the American Chemical Society, 76, 363 (1954).

2. A. Samaniego, B. L. Hurley and G. S. Frankel, Journal of Electroanalytical Chemistry, 737, 123 (2015).

3. G. S. Frankel, A. Samaniego and N. Birbilis, Corrosion Science, 70, 104 (2013).
Dealloying of Magnesium Alloys
Authors: Wingersky Ashlee , Handler Allison , Fisher Julia , Weiss Anna , Sieradzki Karl
Published: February 2020

The corrosion behavior of cast Mg-Al alloys such as AZ91D and AM60B is strongly dependent on the alloy composition and microstructure.  Alloy grain size, area fraction of phases and spatial distribution of the phases are important factors governing both full immersion and atmospheric corrosion behavior. Mg-Al alloy systems can be broadly characterized as being composed of a primary a-Mg matrix (grains) containing Al in solid solution and b-phase intermetallic particles mainly distributed within and adjacent to grain boundaries.  Heat treatment of the as-cast alloys significantly modifies the microstructure altering grain size, phase amounts and distribution as well as the a-Mg phase composition.

The general scenario that we envision evolving during corrosion of cast Mg-Al alloys is the following. In near-neutral electrolytes containing chloride, second phase particles such as the Mg17Al12 b-phase serve as cathodes for water reduction resulting in increases in pH.  The corresponding dissolution reaction involves the dealloying of Mg from a-matrix grains resulting in enrichment and redistribution of solid solution Al as well as impurities (such as Fe) that may be present within the grains.  The redistributed Al will form Al clusters on the surface of the now dealloyed a-phase that can also serve as cathodes. If the pH rises to ~ 9-9.5, the a-phase will begin to passivate and the b-phase can in principle dealloy (selective dissolution of Al) since the corrosion potential (~1.5V vs. SCE) is high enough for this to occur.  At this elevated pH, aluminum may dissolve as the soluble aluminate and will tend to precipitate on to the dissolving alloy surface. Thus, owing to these pH changes local cathodes can become anodes and vice versa. The degree to which these processes affect corrosion behaviors depends on the spatial density (mean separation) of existing and evolving surface cathodes and how this length scale compares to the thickness of a electrolyte diffusion boundary layer or condensed liquid layer (atmospheric corrosion) and grain size.

Given this hypothesis for corrosion behavior, we have been examining dealloying of AZ91D and AM60B as well the constituent a- and b-phases. Instead of relying on a technique such as EDS to characterize the time-dependent change in Al concentration on a corroding surface we developed an electrochemical assay involving Li underpotential deposition (UPD) that measures the electrochemically active surface area (ECSA) of Al. We show results comparing the new assay protocol yielding the ECSA of Al to that obtained from EDS. Anodic dissolution behaviors of the alloys and constituent phases have been measured in an ionic liquid electrolyte (neat1:2 molar ratio of choline chloride:urea) which allows for accurate determination of the evolving surface composition as a function of well-defined anodic dealloying rates. We discuss these results together with some preliminary Kinetic Monte Carlo modeling of corrosion processes of the constituent a-phase.