bluuebunny/crossref_metadata_2025 huggingface dataset:
(Invited) Assembling Different Functional Molecules into Multifunctional, Crystalline, Molecular Solids
Authors: Wöll Christof
Published: February 2020

Metal-organic frameworks (MOFs) carry a huge potential with regard to assembling different types of function organic and metal-organic molecules into multifunctional,hybrid, molecular solids. The field is presently getting quite mature, as demonstrate by several applications exploiting the electrical, electronic and photophysical properties of this rich class of porous, crystalline materials [1]. Recent examples are MOF-based electrochemical [2,3], photo-electrochemical [4] and photovoltaic devices [5,6], as well as photon-upconversion [7]. We have developed a layer-by-layer method to produce well-defined, highly oriented and monolithic MOF thin films supported on different types of surfaces, also referred to as SURMOFs [1]. This procedure in particular allows the fabrication of hetero-multilayers. The fabrication of such well-defined model systems will be described, as well as the results of detailed, multi-technique investigations of electrical [8] and photophysical properties exhibited by empty and loaded MOFs, including cyclic voltammetry, atomic force microscopy, quartz crystal microbalance and UV-Vis spectroscopy. We will discuss the huge size of the chemical space spanned by MOFs can propose that by loading MOFs with nanoparticles or quantum dots the potential is further extended. SURMOFs offer particular advantages in this context, since the loading can be integrated in the layer-by-layer method, offering the potential to fabricate hetero-mulitlayers.

References:

[1] J. Liu, Ch. Wöll, Chem. Soc. Rev. 46, 5681 (2017)

[2] A. Dragässer, O. Shekhah, O. Zybaylo, C. Shen, M. Buck, Ch. Wöll, D. Schlettwein, Chem. Comm., 48, 663 (2012)

[3] J. Liu, M. Paradinas, L. Heinke, M. Buck, C. Ocal, V. Mugnaini, Ch. Wöll

Chem.Elektro.Chem., 3, 713 (2016)

[4] Lu Ye, J. Liu, Y. Gao, Ch. Gong, M. Addicoat, Th. Heine, Ch. Wöll, L. Sun, Mater. Chem. A, 4, 15320, (2016)

[5] J. Liu, W. Zhou, J. Liu, I. Howard, G. Kilibarda, S. Schlabach, D. Coupry, M. Addicoat, S. Yoneda, Y. Tsutsui, T. Sakurai, S. Seki, Zh. Wang, P. Lindemann, E. Redel, Th. Heine, Ch. Wöll, Angew. Chemie Intl. Ed., 54, 7441 (2015)

[6] J. Liu, W. Zhou, J. Liu, Y. Fujimori, T. Higashino, H. Imahori, X. Jiang, J. Zhao, T. Sakurai, Y. Hattori, W. Matsuda, Shu Seki, S. K. Garlapati, S. Dasgupta, E. Redel, L. Sun, Ch. Wöll, Journal of Mat. Chem. A, 4, 12739 (2016)

[7] M. Oldenburg, A. Turshatov, D. Busko, S. Wollgarten, M. Adams, N. Baroni, A. Welle, E. Redel, Ch. Wöll, B. S. Richards, I. A. Howard, Adv. Mater., 28, 8477 (2016)

[8] J. Liu, T. Wächter, A. Irmler, P.G. Weidler, H. Gliemann, F. Pauly, V. Mugnaini, M. Zharnikov, Ch. Wöll, ACS Applied Materials & Interfaces, 7, 9824, (2015)
Solid-Surface Modification with Two-Dimensionally Ordered Oriented Molecular Films
Authors: Fukushima Takanori
Published: February 2020

The surface properties of solid substrates have a considerable impact on many physical, chemical, and electrochemical events occurring at a materials interface, and thus the control of chemical and physical properties of solid surfaces (e.g., surface morphology and energy, wettability, and adhesiveness) provides a key technology in many practical applications. As a useful approach for this purpose, the formation of self-assembled monolayers (SAMs) has widely been used, which relies on specific bonding between polar functional groups of organic molecules and outermost surface elements of inorganic substrates. However, this approach cannot be applied for the modification of polymer substrate surfaces, which are devoid of any effective binding site against polar functional groups. Here we report a new type of organic surface modifier consisting of a paraffinic tripodal triptycene, which undergoes controlled self-assembly not only on inorganic substrates but also on polymer substrates, resulting in a completely oriented molecular thin film like SAMs. The formation of this molecular film does not rely on specific chemical bonding but on a unique assembling property of the molecular building block capable of forming 2D (hexagonal triptycene array) + 1D (layer stacking) structure regardless of the types of substrates. In this presentation, an application of this molecular film to organic electronic devices, which can enhance device performances, will also be described.
(Invited) Fabrication of Ordered Semiconductor Nanostructures for Energy Conversion Based on Anodization Processes
Authors: Masuda Hideki , Kondo Toshiaki , Yanagishita Takashi
Published: February 2020

High throughput fabrication of ordered nanostructures of semiconductors is an important subject for the preparation of the photo-energy devices with high conversion efficiencies1. Anodization process of metal is a promising candidate for the efficient fabrication of nanostructured semiconductors with controlled geometrical structures2. Anodic porous alumina, which is formed by anodization of Al in acidic solution, is a typical self-ordered material. The use of the anodic porous alumina as a starting structure allows the efficient preparation of the semiconductors with controlled geometrical structures, such as nanorods or nanodots arrays3. The anodization processes of appropriate metals can also generates the semiconductors with controlled geometrical structures. For example, the anodization of Ti in the electrolyte containing F- generates the porous TiO2 with controlled nanostructures4. In the present report, recent results concerning the fabrication processes for the semiconductors with ordered geometrical nanostructures for the photo-energy conversion will be described. The processes include the preparation of semiconductor nanorod arrays from anodic porous alumina templates and its application to organic photovoltaic solar cells. In addition, anodization process using pretextured Ti for the TiO2 with ideally ordered hole arrangement will be shown5. This process can be also applied to the fabrication of porous TiO2 with modified hole shapes6. The results of the efficient fabrication of ordered TiO2 will be also described. The obtained semiconductor nanostructures will be applied to various types of photo-energy conversion devices with high efficiency originated from precisely controlled geometrical structures.

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Masuda and K. Fukuda, Science, 268, 1466 (1995).

Masuda, T. Kondo, T. Yanagishita, 231st ECS Meeting, 834 (2017).

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Kondo, S. Nagao, T. Yanagishita, N. T. Nguyen, K. Lee, P. Schmuki, H. Masuda, Electrochem. Commun., 50, 73 (2015).

Kondo, S. Nagao, T. Yanagishita, H. Masuda, J. Electrochem. Soc., 163, E206 (2016).
(Invited) Configuration of Organic Conjugated Molecular/Polymer Systems at the Interfaces and Under High Pressure: Non-Contact Assessment By Microwave Electrical Conductivity Measurements
Authors: Seki Shu
Published: February 2020

Tuning and optimization of charge carrier transport at interfaces is one of the most important subjects in the design of opto-electronic devices and materials. Charge carriers are injected or extracted through metal/semiconductor interfaces in most electronic devices, while carrier transport occurs at insulator/semiconductor interfaces rather than in the bulk in the major organic electronic devices.1,2 However, analytical techniques for evaluating such interfacial carrier transport phenomena are still limited, and this remains a challenging issue. We have recently reported a technique, referred to as time-resolved microwave conductivity (TRMC)3, and the system has been extended into field-induced TRMC that combines charge carrier injection via gate bias applied into working devices and microwave-based non-contact probing of intrinsic and local charge carrier motion. Using this technique, hole and electron mobilities were separately and quantitatively determined in a series Au/organic semiconductor/PMMA/SiO2/Au MIS devices,4,5 demonstrating that the non-contact, fully experimental evaluation of intra-domain carrier mobility at interfaces is quite unprecedented and is a characteristic feature of this system. Herein, we further report that the FI-TRMC technique can distinguish between mobile charge carriers at the interface and immobile charges trapped at defects, thus enabling quantification of both the charge carrier mobility and the density of trap sites at insulator-semiconductor interfaces.

References

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70, 469 (1991).

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39, 2643 (2010).

S. Seki, et al., Phys. Chem. Chem. Phys. 16, 11093 (2014); Acc. Chem. Res.
45, 1193 (2012); Nature Commun.
5, 3718 (2014); Nature Commun. 4, 2694 (2013); Nature Commun.
4, 1691 (2013)

Y. Honsho, T. Miyakai, T. Sakurai, A. Saeki, and S. Seki, Sci. Rep.
3, 3182 (2013).

W. Choi, Y. Tsutsui, S. Seki, et al., Appl. Phys. Lett.
105, 019430 (2014); Adv. Mater.
28, 7106 (2016); Appl. Phys. Lett.
110, 153303 (2017); Appl. Phys. Lett.
110, 203302 (2017)
Formation of Hydrogen-Bonded Supramolecular Hetero-Triads with a Diprotonated Porphyrin
Authors: Kojima Takahiko
Published: February 2020

Supramolecular assemblies based on intermolecular hydrogen bonding (H bonding) have been intensively investigated to develop functional materials. Along this line, we have developed supramolecular assemblies using protonated and saddle-distorted porphyrins as H-bonding electron acceptors to gain unique photofunctionality of the assemblies.1 In order to expand the possibility of structures and components of the assemblies, it is required to develop a strategy to construct H-bonded supramolecular assemblies involving different components. Herein, we present selective formation of unusual H-bonded hetero-triads.

We examined formation of hydrogen-bonded supramolecular assemblies using dodecaphenylporphyrin (H­2DPP) with various acids including carboxylic acids, sulfonic acids, and carboxylic acids with positively charged moieties. It was revealed that the stability of homo-assembly (H4DPPX2; X = conjugate base of an acid) can be controlled by the strength of the H bonding depending on the acidity of an acid used to protonate H2DPP and the electrostatic repulsion between the H4DPP2+ cation and the positively charged moiety of an acid used.2 By employing a carboxylic acid with a pyridinium moiety, the PF6
- salt of N-benzyl-4-carboxyphenylpyridinium (BnPy+-COOH•PF6
-) to react with H4DPPCl2 in chloroform, we succeeded in the formation and crystal structure determination of a supramolecular hetero-triad, [H4DPP2+(Cl–)(BnPy+-PhCOO–)](PF6
–).

S. Fukuzumi, T. Honda, T. Kojima, Coord. Chem. Rev.
2012, 256, 2488-2502.

W. Suzuki, H. Kotani, T. Ishizuka, Y. Shiota, K. Yoshizawa, T. Kojima, Chem. Commun.
2017, 53, 6359.
Supramolecular Chemistry of Cobalt-Corrins
Authors: Kräutler Bernhard
Published: February 2020

Cobalt corrins are chiral relatives of the cobalt porphyrins, in which the ligand is much less unsaturated and is also ‘contracted’ by one carbon. This type of ligand strongly affects the redox and coordination chemistry of the bound cobalt center. Some lipophilic artificial cobalt corrins have been prepared in tremendous synthetic efforts in the Eschenmoser labs. The natural analogues offer an apparently more straight forward chemical entry to cobalt corrins. However, the natural cobalt corrins are all hydrophilic and highly substituted at their periphery, and they are distantly related to heme and chlorophyll. Although these cobalt corrins are very soluble in water, their natural roles are intimately connected with their essential and rich organometallic chemistry, which is all cobalt-centered.[1]

In this lecture, means for specific supramolecular assemblies based on modified natural cobalt corrins are delineated, as well as consequences of the supramolecular restructuring on the organometallic and redox-chemistry. So far, in the excursions to be reported, the cobalt corrin core is not altered and its redox and spectral properties are largely conserved.

A unique basis for specific supramolecular assemblies is then provided by the (organometallic) ligand itself, either, when attached to and bridging more than one metal center, or, when providing a structuring interface itself, for the build-up of supra-molecules. In a second general type of supramolecular assemblies the functional groups attached at the peripheral substituents of the natural corrinoids are used in a uniform way. By this means, the direct environment of the cobalt corrin moiety may be affected and structured in a global fashion, generating, e.g., a type of molecular micelles. A third type of supramolecular assembly makes selective use of single sites of the complex, but largely conserved sphere of the peripheral substituents, in order to generate specifically structured cobalt-corrins and their dimers. These latter ones may feature binuclear (organometallic) coordination chemistry, which would allow for synchronized redox processes in a highly structured, ‘second’ sphere around the metal centers.

I thank the Austrian Science Foundation (FWF, project P-28892 and earlier projects) for generous financial support.

References

[1] B. Kräutler, B. Puffer, in Handbook of Porphyrin Science, Vol. 25 (Ed.: K. M. Kadish, Smith, K. M., Guilard, R.), World Scientific, 2012, pp. 133-265.
Isolating O-O Bond Activation with Manganese Porphyrins
Authors: Dogutan Kiper Dilek , Passard Guillaume , Qiu Mengting , Costentin Cyrille , Nocera Daniel G
Published: February 2020

The oxygen reduction reaction (ORR) is catalyzed by manganese(II) tetraphenyl porphyrin (Mn(II)TPP) in the presence of Brønsted acids (HAs). Analysis of the catalytic wave in the cyclic voltammogram of the ORR reaction leads to the proposal two equivalents of HA drives the formation of the initial oxygen adduct, followed by oxygen-oxygen bond activation. An analogous hangman Mn(II) TPP compound has been prepared and characterized. For this ORR catalyst, an acidic proton is provided intramolecularly, and the HA order is reduced to one equivalent. Our data supports a model where one HA is used to stabilize the oxygen bound to the reduced hangman Mn(II) porphyrin platform; one HA is not needed as an internal hydrogen bond may be formed with the hanging acid group. The O–O bond cleavage requires an external HA for the rate-determining step, thus offering a rare example where the O–O bond activation of an ORR process is isolated and captured.
Porphyrin-Hexabenzocoronene Systems
Authors: Jux Norbert , Lungerich Dominik , Hölzel Helen , Ruppel Michael , Martin Max
Published: February 2020

We will present new architectures based on porphyrins and hexaarylbenzenes/hexabenzocoronenes. Special emphasis lies on crystal packing phenomena.

We report on the synthesis, characterization, and properties of some of these novel systems.[1-3]

References

[1] J. M. Englert, J. Malig, V. A. Zamolo, A. Hirsch, N. Jux, Chem. Commun. 2013, 49, 4827 – 4829.

[2] D. Lungerich, J. F. Hitzenberger, M. Marcia, F. Hampel, T. Drewello, N. Jux, Angew. Chem. Int. Ed..
2014,
53, 12231-12235.

[3] D. Lungerich, J. F. Hitzenberger, W. Donaubauer, T. Drewello, N. Jux, Chem. Eur. J.
2016, 22, 16755-16759.

Figure 1
Profiling Proteasome Activity By Porphyrins
Authors: Purrello Roberto
Published: February 2020

Inspired by some preliminary data and their versatile chemistry we have been investigating the ability of porphyrins to inhibit proteasome activity. Cationic porphyrins exhibit an amazing variety of binding modes and inhibition mechanisms. They may bind to the 20S proteasome gates hindering the entrance of the substrate into the catalytic chamber or, by functional connection between the α- and β-rings, allow for allosteric modulation. By contrast, anionic porphyrins may activate the core particle by facilitating the access of the substrate to the proteasome interior, likely regulating the “open”-“closed” allosteric equilibrium. In conclusion, the positioning of the charged substituents represents a sort of key code to fine-tuning porphyrins interference with proteasome gating.
Environmentally Friendly Coatings for Improved Stainless Steel Corrosion Resistance from Biorefinery Side Streams
Authors: Dastpak Arman , Yliniemi Kirsi , Monteiro Mariana , Höhn Sarah , Lundström Mari , Virtanen Sannakaisa , Wilson Benjamin Paul
Published: February 2020

Although metals are routinely used in medical implant applications, corrosion of these inserted materials is an issue that can potentially have significant health impacts. For example, Stainless steel (SS) 316L - one of the most commonly used implant substrates - undergoes corrosion under physiological conditions. Such material degradation leads to the release of various potentially carcinogenic ions (e.g. Fe, Cr, Ni1,2) and over 90% of SS 316L implant failures are estimated to as a result of corrosion2. Fortunately, many of these difficulties can be mitigated through the use of biocompatible coatings on implant surfaces.

In this research, the effect of a lignin-based coating on SS 316L corrosion resistance was investigated. Two distinct types of lignin (from Soft and Hardwood) were dissolved in solvent and spin-coated on SS 316L. Subsequent surface characteristics were analysed by different techniques (AFM, FTIR) and the corrosion resistance of the obtained surfaces were studied by electrochemical methods. Results show that the presence of a lignin coating leads to an increase in surface wettability, whilst decreasing the measured corrosion current density of the metal by 2-3 orders of magnitude.

Overall, this research clearly highlights the potential of lignin from Biorefinery side streams as a sustainable and environmentally friendly coating for corrosion protection.

Keywords: Lignin, organic coatings, spin coating, SS316L corrosion

The authors acknowledge the Technology Industries of Finland Centennial/Jane and Aatos Erkko Foundations “Future Makers: Biorefinery Side Stream Materials for Advanced Biopolymer Materials (BioPolyMet)” project for funding this research. In addition, this work made use of facilities provided by the RawMatTERS Finland Infrastructure (RAMI) at Aalto University, which is supported by Academy of Finland.

References

Shih C, et al. Growth inhibition of cultured smooth muscle cells by corrosion products of 316L stainless steel wire. J Biomed Mater Res. 2001;57(2):200-207

Douglas CH. Metal corrosion in human body: The ultimate bio-corrosion scenario. The Electrochemical Society INTERFACE. Summer 2008;17(2):31
Enhanced Corrosion Mitigation of TiO2 coated Stainless Steels Under UV Illumination
Authors: Sathasivam Kamalasekaran , Yeh Tsung-Kuang , Wang Mei-Ya
Published: February 2020

Austenitic stainless steels are commonly used as the structural material for dry-storage canisters in nuclear power plants because of their excellent corrosion resistance and mechanical properties. Dry-storage canisters are often exposed to chloride containing atmosphere near seashores, which could induce localised stress corrosion cracking in these stainless steels near the welded regions. TiO2 coatings applied on stainless steel substrates (i.e. Type 304 stainless steels) along with ultraviolet (UV) irradiation have been proposed as a mitigation measures against the corrosion in canister materials.

In this study, TiO2 coatings were applied on stainless steel samples using a sol-gel dip-coating method. The corrosion characteristics of the coated samples were studied under the conditions of different coating treatments, annealing temperatures, annealing atmospheres and UV illumination durations. The corrosion mitigation performance of the coated samples with and without UV illumination was evaluated by electrochemical polarization analyses and open-circuit potential measurements. The surface morphologies of the samples were studied by scanning electron microscopy (SEM), energy dispersive X-ray spectroscopy (EDX), and laser Raman spectroscopy. In addition, the photocatalytic responses of these coatings exposed to various acidic and alkaline aqueous solutions under aerated and deaerated conditions were also studied. The results indicated that the TiO2 coating not only could lead to low electrochemical potentials of the stainless steel samples during UV illumination, but could also maintain the low electrochemical potentials even after the cut off of UV illumination. Results from Electrochemical polarization analyses further support the superior corrosion resistance under UV-illumination conditions.

Keywords: Stainless steel, TiO2 coating, ultraviolet illumination.
Advancing Reliability of Membrane-Based Corrosion and Environmental Sensor in Simulated Natural Gas
Authors: Duffy Timothy , Hall Derek M. , Ziomek-Moroz Margaret , Lvov Serguei N.
Published: February 2020

Monitoring simultaneously water-content and corrosion rates in low conductivity natural gas pipeline systems) is carried out using membrane-based electrochemical sensors. An ion conducting membrane improves conductivity in humid natural gas in which electrochemical measurements can be performed. In this study, we monitor corrosion rate and humidity of a gas pipeline through the use of commercial Nafion™ membranes, whose conductivity depends on the partial pressure of water vapor in the gas stream. To improve the accuracy, consistency, and reproducibility of data collection, sensor designs vary between electrode preparation using platinum wires versus nanofabricating flat electrode surfaces and configuration. Data for humidity and corrosion rates within various environments is collected using electrochemical impedance spectroscopy and linear polarization resistance tests. Data for 2-, 3-, and 4-electrode cell tests are presented to compare experimental artefacts among sensor designs.
Microstructural and Electrochemical Characterization of Friction Stir Welded Aluminum Alloys
Authors: Magnani Marina , Gonçalves Haroldo Marques , Benedetti Assis Vicente , Fugivara Cecilio Sadao
Published: February 2020

Aluminum alloys of 2000 and 7000 series containing cooper and zinc, respectively, as the main alloying element are extensively used in aircraft structures. However, these classes of aluminum alloys are difficult to join by conventional fusion welding techniques because the dendritic structure formed in the fusion zone can seriously compromise the mechanical and corrosion resistance properties of the joint. Friction Stir Welding (FSW) is attractive for joining high strength aluminum alloys since there is far lower heat input during the process compared with conventional welding methods. FSW is produced by rotating and plunging a specially-designed cylindrical, shouldered tool with a small diameter pin into the joint line between two butted plates. Frictional heat causes the metal to soften and allows the tool to traverse along the joint line [1]. The FSW process generates three distinct microstructural zones: the nugget, the thermomechanically affected zone (TMAZ) and the heat-affected zone (HAZ). These microstructural modifications generally interfere in the performance of the corrosion resistance of welded alloys. In the present study, FSW was used to join two dissimilar aluminum alloys, AA2024-T3 (Al-Cu-Mg) and AA7475-T651 (Al-Cu-Mg-Zn) and the effect of this process on the corrosion resistance of the welded joints and on the microstructure of the alloys was evaluated. Microstructural characterization was carried out by optical microscopy, scanning electron microscopy and atomic force microscopy. The weld zone regions showed significant microstructural changes. Electrochemical impedance spectroscopy (EIS) and Electrochemical noise measurements (ENM) were used to evaluate the corrosion resistance of the different zones of the weld in NaCl solution. Local electrochemical measurements using an electrochemical microcell were carried out across the transverse cross section of the welds. The cell containing the solution, counter and reference electrodes is attached to the carousel of an optical microscope. The electrochemical results showed that the corrosion behavior of the AA2024-T3 / AA7475-T651 alloy is dominated by the electrochemical activity within the intermetallics (IMs). The weld zone regions containing copper IMs have a more noble character than the regions containing Zn and Mg IMs. Therefore, the results showed an increased susceptibility of welded joints to these forms of corrosion in comparison to the unaffected base metal by a more severe attack related to AA7475-T651 alloy.

Reference

[1] M. Jariyaboon et al. Corrosion Science 49 (2007) 877–909.

[2] J.-Q. Su et al. Acta Materialia 51 (2003) 713–729

Acknowledgement: Fapesp 2013/132356
Hybrid Silicone-Epoxy Coating Reinforced with Silanized Graphene Oxide Nanosheets with Improved Anti-Corrosion Performance
Authors: Chen Xia , Yue Zhufeng , Yuan Xin , Wen Shifeng , Liu Ziqiang , Feng Tao
Published: February 2020

Silane coating is a frequently applied strategy to promote the adhesion between a substrate and an organic coating. However, the corrosion protection properties of this coating are not sufficient. Incorporation of various additives and nano-fillers into the coating is a promising way to improve the coating barrier property. In this paper a new nano-filler based on graphene oxide (GO) is fabricated with the silane-functionalized grapheme oxides (SF-GO). The graphene oxide is silanized in the first step through a sol–gel route by using aminopropyl triethoxysilane (ATPES) 、Triethoxyvinylsilane （VTES）and tetraethyl orthosilicate (TEOS). Then, it is employed in an organic-inorganic hybrid coating based on the mixture of TEOS and silicone-epoxy coating. The GO functionalization was characterized by Fourier transform infrared spectroscopy (FT-IR) and X-ray photoelectron spectroscopy (XPS). The hybrid coating filled with silanized and untreated GO were also characterized by FT-IR, X-ray diffraction (XRD) and scanning electron microscopy (SEM). The results obtained from different characterizations showed successful silanization and dispersion of SF-GO in the hybrid coating. The hybrid silicone-epoxy coating containing SF-GO showed superior corrosion protective performance compared to the unfilled silane coating in electrochemical impedance spectroscopy (EIS) and polarization measurements, indicating the considerable corrosion barrier effect of the nano-filler. Moreover, the bonding strength of the composites was strengthened and the deformation were identified and evaluated.
Mesoscale Modeling of Inelastic Deformation and Stress in High Temperature Oxidation of Metals
Authors: Cheng Tian-Le , Wen You-Hai , Hawk Jeffrey A.
Published: February 2020

Metal oxidation mostly involves significant volume change that cannot be accommodated by elastic deformation alone. Consequently, during the growth of oxide there are various elastic/inelastic deformation in the matrix, oxide, and slip along phase boundaries and grain boundaries. Due to the microstructural complexity, it is difficult to model inelasticity in oxidation from the dislocation level. Here we develop a mesoscale phase-field approach, based on Khachaturyan’s close-form solution for microelasticity, to solve the inelastic deformation coupled with mass transport and microstructure evolution. The model incorporates both classical J2
plasticity and crystal plasticity to accommodate inelastic deformation of a polycrystal with interfacial sliding. The model is validated by a series of analytical solutions and by comparing with other numerical simulations. Finite deformation is approached by an incremental realization algorithm. The model is also applied to simulate incoherent interfaces and coherency loss. During internal oxidation, isolated oxide particles are usually coherent when they are small while they gradually lose coherency during the growth.
Utilizing the FeCrAl Alloys Oxidation Properties in Water, Air, and Steam
Authors: Gupta Vipul K. , Larsen Michael , Rebak Raul B.
Published: February 2020

The demonstrated interest of using iron-chrome-aluminum (FeCrAl) ferritic alloys as accident tolerant fuel (ATF) cladding in light water reactors has recently resurfaced the interest in FeCrAl, which have been used for other purposes for more than eight decades. The main interest for ATF is that FeCrAl alloys are many orders of magnitude more resistant to attack in super-heated steam (>1200°C) than zirconium alloys. Recent research has shown that FeCrAl is also resistant to corrosion in high temperature (~300°C) reactor normal operation conditions hydrogenated water since it develops a protective chromia rich oxide film on its surface. Under accident conditions in superheated steam the surface oxide becomes alumina. If an alumina protected tube is flooded with fresh water after the quenching in accident, the surface oxide returns to chromia. The oxide protection versatility of FeCrAl alloys will be discussed on the several situations that may be encountered in a light water reactor both under normal operation conditions and under the unlikely situation of an accident.
Corrosion Mechanisms of a Turbine Blade from Shipboard Engine Service
Authors: Meisner Kevin J. , Opila Elizabeth J.
Published: February 2020

Failed turbine blades from a marine diesel turbine engine were characterized to identify corrosion mechanisms. The blade materials were a Mar-M247 substrate with a CoNiCrAl coating. The blades were subject to a variety of damage mechanisms including oxidation/hot corrosion assisted cracking, internal corrosion by FeCMAS deposits in cooling channels, and hot corrosion pitting of the coating that reached and consumed the substrate. Scanning Electron Microscopy (SEM) and Energy-Dispersive Spectroscopy (EDS) were used to characterize the morphology and composition of the failed material. Inductively-Coupled Plasma Optical Emission Spectroscopy (ICP-OES) was used to confirm the composition of deposits. The different corrosion modes are summarized and insights into their mechanisms are discussed.
Thermal Oxidation-Induced Self-Healing on Yttrium Silicate Composites Dispersed with Silicon Carbides
Authors: Nanko Makoto , Dinh Vu Huy
Published: February 2020

SiC/SiC composites are expected as new generation of gas turbine materials. However, SiC is remarkably oxidized in the combustion gas atmosphere due to existence of water vapor to lead to evaporation of SiO2 scale. In order to protect SiC/SiC composites from water vapor in the combustion gas, environmental barrier coatings (EBCs) system was proposed. Protective coating from water vapor in the EBCs system consists of oxide materials such as mullite, LaBaSiO2, Y2SiO5/Y2Si2O7, and Yb2SiO5/Yb2Si2O7. However, EBCs system loses productiveness for water vapor when EBCs were cracked penetrating into the substrate SiC/SiC composites.

Nowadays, many self-healing ceramics have been developed such as SiC/Al2O3, SiC/mullite and Ni/Al2O3. In these ceramics, non-oxide dispersoids are oxidized on the crack surface to fill the crack with the oxidation product. In any cases, the oxidation product is formed to fill the crack via diffusion of cations through the matrix oxide.

In this report, self-healing EBCs system is proposed with Y2SiO5 and Y2Si2O7 composites dispersed with SiC particles. Self-healing effectiveness of the composites was evaluated with crack-disappearance by high-temperature oxidation in air. In order to fit the CTE of EBCs system to that of SiC/SiC composites, mixture of Y2SiO5 and Y2Si2O7 was used. SiC/(Y2SiO5+Y2Si2O7) composite is also investigated on its self-healing effectiveness on the surface cracks.

Y2SiO5 and Y2Si2O7 were prepared by reaction of powder mixture of Y2O3 and SiO2 at 1400°C in air. Powder mixture of yttrium silicates with 5 vol% of SiC powder was consolidated by using the pulsed electric current sintering at 1500°C for 5 min under 70 MPa in vacuum. In the mixture matrix composites, mixture of 30 vol% Y2SiO5 and 70 vol% Y2Si2O7 was prepared. Surface cracks (200 mm in surface length) was introduced into polished surface of the composite samples with the Vickers indentation. Figure 1 shows the surface cracks of (a) SiC/Y2SiO5, (b) SiC/Y2Si2O7 and (c) SiC/(Y2SiO5+Y2Si2O7). Thermal oxidation experiments were conducted in air at temperature of 1300°C for 1 and 6 h. Crack-disappearance after thermal oxidation was evaluated by crack length before/after thermal oxidation.

Figure 2 shows surface appearance of (a) SiC/Y2SiO5 and (b) SiC/Y2Si2O7 for 1 h. Surface cracks are filled by the oxidation product Surface cracks was completely disappeared by thermal oxidation for both of SiC/Y2SiO5 and SiC/Y2Si2O7 at 1300°C for 1 h. Figure 3 shows surface appearance of SiC/(Y2SiO5+Y2Si2O7) at 1300°C for 1 h. Surface cracks of SiC/(Y2SiO5+Y2Si2O7) was completely disappeared. Self-healing effectiveness of SiC/(Y2SiO5+Y2Si2O7) is similar with the monolithic matrix composites.

The authors wish to express their gratitude to the Japan Science and Technology Agency for supporting partially this study through the Advanced Low Carbon Technology Research and Development Program.

Figure 1
Hydrogen Interaction Properties of Cr2O3 Passive Films upon Helium Ions Irradiation
Authors: Ling Yunhan , Wu Dehui , Xin Zhiyuan
Published: February 2020

Controlled nuclear fusion is a new way to produce ideal energy utilising hydrogen isotopes as fuel, where deuterium and tritium undergo a nuclear reaction at extremely high temperatures to form helium and a neutron. A growing interest in hydrogen permeation barriers is driven by approaches aimed at reducing hydrogen embrittlement on structural materials as well as radiological isotope leakage induced hazards during the service of fusion reactor. Cr2O3 is one of the potential surface coatings to improve the hydrogen resistance of stainless steel substrates, but so far the irradiation effect of high energy particles as well as the helium created by radioactive decay on the hydrogen permeation properties are far from clear. Herein, nanoscale Cr2O3
passive film formed on electroplated chromium coating and then oxidized by oxygen-poor plasma was used to investigate the influence of irradiated helium on the hydrogen permeation behaviors. Passive films have been irradiated with 300 keV helium ions at the fluence of 1×1016 ions·cm-2 prior to exposure of hydrogen at 350oC. The interactions between the embedded helium and hydrogen were analyzed by comprehensive surface analyses. The depth of ion implantation has been simulated by SRIM, microstructural evolution of these irradiated passive films has been estimated by using the non-destructive conductive atomic force microscopy, the chemical states and defect characteristics of sample were measured by X-ray photoelectron spectroscopy and electrochemical impedance spectroscopy. Measurements indicate that He induced defects are formed in the passive film and lead to enhanced diffusion of hydrogen of the sample surface.
Investigation of Surface Interactions between Volatile Chromium Species and Ceramics
Authors: Tatar Greg , Gannon Paul , Dansereau Spencer , Remington Emily
Published: February 2020

Volatile chromium species are formed when chromium containing materials are exposed to high temperature (>500°C) oxidizing environments. These volatile species are often accompanied by detrimental effects, such as cathode poisoning in solid oxide fuel cells and condensation of toxic hexavalent chromium species. The reactive vaporization of chromium species and their detrimental effects are well understood, but less is known about how these species interact with and condense onto various materials. This study investigates how volatile chromium species interact with ceramics over a range of temperatures and exposure times. Preliminary work performed on aluminosilicate fibers suggests that chromium speciation depends on factors such as temperature, chromium loading of a surface, and what material the volatile chromium is interacting with. Additionally, the color of condensed chromium species on these fibers has been linked with the oxidation state of chromium, allowing inferences to be made to known chromium compounds such as chromate, chromium trioxide, and chromia. To extend this work, volatile chromium was generated by flowing humidified air over chromia powder at various temperatures up to 900°C for various time intervals up to 100 hours. Vapor collection materials, including pure and mixed silica and alumina ceramic fibers and coupons, were placed downstream at temperatures ranging from 50-900C. Post exposure characterization of ceramic surfaces was performed using x-ray photoelectron spectroscopy, x-ray diffraction, inductively coupled plasma mass spectroscopy, and colorimetry to obtain information about chromium speciation in the form of oxidation states and phase formation. Results will be presented and discussed in context of advancing fundamental understanding of condensation mechanisms for volatile chromium species.
Electrodeposited Inconel and Stellite like Coatings for Improved Corrosion Resistance in Biocombustors
Authors: Hall Timothy D , Vijapur Santosh H. , Wang Dan , Taylor E. J. , Inman Maria , Snyder Stephen , Brady Michael
Published: February 2020

Biomass embodies tremendous potential as a renewable energy resource. According to the biomass thermal Energy Council (BTEC), biomass energy is renewable, carbon neutral, domestic and technologically mature. In addition, the low cost per BTU of wood chips and pellets relative to fossil fuels makes biomass an attractive thermal energy source. Furthermore, ~7% of global energy consumption comprises small-scale biomass combustion,[1] representing a tremendous market for technologies that facilitate enhanced biomass utilization. However, a major challenge associated with utilization of biomass is its combustion behavior. The moisture content, chemical composition, and combustion efficiency varies depending on the source of biomass. Small scale biomass combustors (Figure 1), which for cost reasons are often constructed of mild or low-alloy steels, during operation are subjected to corrosive environments that include alkali halides (borne, e.g., by fly ash particulates), mineral/halogen acids and water; as well as various others such as sulfur and nitrogen oxides. There is a need to create more efficient, longer lasting, cleaner, and cost effective cookstoves for use in burning biomaterials. The materials used for cokstoves must improve burning efficiency, must be able operate at higher temperatures, and should be low cost material systems to durably perform in the corrosive environments. Within this context, Faraday Technology is working on developing low cost and high value corrosion-resistant alloy coatings for existing bio-combustors or lower cost steels with the goal of increasing their functional lifetime, while reducing the component cost. The manufacturing process involves electrodeposition of binary/ternary/quaternary alloys consisting of [Ni/Co]-Cr-[Mo/Fe] onto a low cost substrate and subsequent accelerated high temperature corrosion evaluation. A wide array of electrolytes and processing parameters were evaluated in order to understand these effects on the deposit composition, structure, and high-temperature corrosion resistance properties towards the goal of developing an ideal alloy coating. Specifically, 60 wt% Ni – 40 wt% Cr (NiCr) binary and 25 wt% Ni – 20 wt% Cr – 55 wt% Co (NiCoCr) ternary alloy coatings demonstrated enhanced corrosion resistance when exposed to an aggressive environment (~700°C, 1000 hr, coating surface salted with ~3 mg/cm2 every 100 hours). When compared to the SS base material the NiCr and NiCoCr alloy coatings exhibited a 70% lower weight loss and 3.4 times lifetime improvement over its base material.

Acknowledgements: The financial support of DOE Contract No. DE-SC0013870 is acknowledged.

[1] Biomass Production Now 10 Percent of World Energy, http://www.realclearenergy.org/charticles/2013/09/26/biomass_production_now_10_percent_of_world_energy_107257.html. Accessed 12 Jan 2015.

Figure 1
Electrolytic Reduction of Cerium Oxide
Authors: Rodriguez David , Monreal Marisa , Jackson Matt , Weisbrod Kirk
Published: February 2020

Abstract

Since the early 2000s, when the Fray-Farthing-Chen (FFC, direct reduction) and the Ono-Suzuki (OS, indirect reduction) processes on titanium oxide were elucidated, several additional metal oxides (Zr, Ta, Cr, and Nb) have been reported to electrolytically reduce to their metallic state in molten CaCl2-CaO.1-3 However, the electrolytic reduction of cerium oxide has resulted in mixed degrees of success. As such, the goal of this study is to identify side reactions that occur that are parasitic to the overall reaction of producing cerium metal and correlate that to the composition of the salt. Previous reports indicate that the reaction pathway from CeO2 to Ce0 is not direct and includes side reactions that result in the formation of Ce2O3, CeOCl and CeCl3.3-5 Our efforts to use cyclic voltammetry to identify side reactions, which allowed for the determination of approximate concentrations of side reaction products as well as Ce0 produced as a result of electrolysis, will be presented.

Acknowledgements

For financial support of this work, we acknowledge the U.S. Department of Energy through the LANL LDRD Program (Mission Foundations Research Project #20170558ER).

References

1 Chen, G. Z., Fray, D. J. & Farthing, T. W. Direct electrochemical reduction of titanium dioxide to titanium in molten calcium chloride. Nature
407, 361-364 (2000).

2 Suzuki, R. O., Ono, K. & Teranuma, K. Calciothermic reduction of titanium oxide and in-situ electrolysis in molten CaCl2. Metallurgical and Materials Transactions B
34, 287-295, (2003).

3 Claux, B., Serp, J. & Fouletier, J. Electrochemical reduction of cerium oxide into metal. Electrochimica Acta
56, 2771-2780, (2011).

4 Zhao, B. et al. Direct electrolytic preparation of cerium/nickel hydrogen storage alloy powder in molten salt. Journal of Alloys and Compounds
468, 379-385, (2009).

5 Castrillejo, Y., Bermejo, M. R., Pardo, R. & Martı́nez, A. M. Use of electrochemical techniques for the study of solubilization processes of cerium–oxide compounds and recovery of the metal from molten chlorides. Journal of Electroanalytical Chemistry
522, 124-140, (2002).
(Invited) Optical Properties of All-Inorganic Perovskite Nanocrystals
Authors: Gregorkiewicz Tom
Published: February 2020

All-inorganic cesium lead halide perovskite nanocrystals (CsPbX3 NCs, X = Cl, Br, I) have attracted much attention recently due to their high photoluminescence quantum yields (50-90%) and narrow emission bands with wide tunability. They combine the advantages of perovskites and quantum dots creating an exceptional material for low-cost optoelectronic and photovoltaic devices. Conducting low-voltage electron energy loss spectroscopy (EELS) on individual NCs, we provide novel insights regarding three important aspects of their microscopic behavior: (i) we explicitly demonstrate the relation between NC size and shape with their bandgap, and that the effective coupling between proximal NCs causes band structure modifications [1]; (ii) the synthesis of CsPbX3 NCs inevitably yields simultaneous formation of other nanostructures, insulating Cs4PbBr6 nanohexagons and hybrid nanospheres [2]; and (iii) drop-casted NCs merge spontaneously at room conditions by seamless stitching of aligned NCs, it can be accelerated by humidity and mild-temperature treatments, while arrested with electron beam irradiation [3]. Further, by using high-resolution induced absorption and emission spectroscopies, we obtain detailed information on carrier dynamics in perovskite NCs [4], their water-resistant encapsulation [5], and on energy exchange within their ensembles [6]. Finally, we will also report on the on-going quest of carrier multiplication in these materials.

[1] J. Lin et al. Nano Lett. 2016, 16, 7198.

[2] C. de Weerd et al. C 2017, 121, 19490.

[3] L. Gomez et al. Adv. Energy Mater. 2017, under consideration.

[4] E. M. L. D. de Jong et al. J. Phys. Chem. C 2017, 121, 1941.

[5] L. Gomez et al. Nanoscale 2017, 9, 631.

[6] C. de Weerd et al. J. Phys. Chem. C 2016, 120, 13310.
Color Pure Green and Blue Electroluminescence Using Colloidal Quantum Confined Perovskites
Authors: Jagielski Jakub , Kumar Sudhir , Shih Chih-Jen
Published: February 2020

Hybrid lead halide perovskites, described by a formula ABX3, recently emerged as a new class of semiconducting materials for various optoelectronic devices. Especially, colloidal perovskites exhibit numerous favorable properties, such as high photoluminescence quantum yield (PLQY), tunable bandgap, defect tolerance, high charge carrier mobility, large exciton binding energy (EB
), outstanding color purity (FWHM < 25 nm) and low cost of production, for high efficiency solution-processed light-emitting diodes (LEDs).[1] Analogously to conventional, inorganic quantum dots (QDs), quantum confinement effects could be observed upon forming colloidal perovskite nanoplatelets (NPLs) with thicknesses below ~10 unit cells (n < 10). Taking MAPbBr3 for example, we demonstrate a facile synthetic route to obtain monodisperse colloidal solutions of layered perovskites with precise control from n = 1 to n = 7-10 layers.[2] These layer controlled perovskite NPLs not only offer a color-tunable emission, but also enhance the EB
. The resultant high EB
is crucial to enable efficient radiative recombination of excitons. Most interestingly, our layer controlled NPLs also showed record high solid-state PLQYs (50-85%) for blue and green emission. With this approach we were able to demonstrate efficient pure-blue electroluminescence at room temperature using colloidal 2D perovskites. On the other hand, in order to meet the requirement for ultrapure green emission which targets the Rec.2020 recommendation, FAPbBr3 perovskite NPLs were utilized. Through dielectric quantum well (DQW) engineering high exciton binding energy of 162 mV was achieved which further resulted in superior PLQY value of 92%. The optimized active layer LEDs exhibited a maximum current efficiency of 13 cd/A but most importantly with its CIE 1931 color coordinates (0.168, 0.773) it represents the “greenest” LED ever reported.[3] Motivated by harsh market requirements, we were able to further improve the performance of ultrapure green device over 2-fold through compositional engineering. Using colloidal, ultrapure green emitting perovskite nanocrystals such result has never been reached so far. This opens an avenue towards low-cost and high-throughput production of solution-processed LEDs.

[1] J. Jagielski, S. Kumar, W.-Y. Yu, C.-J. Shih, Journal of Materials Chemistry C
2017, 5, 5610.

[2] S. Kumar, J. Jagielski, S. Yakunin, P. Rice, Y.-C. Chiu, M. Wang, G. Nedelcu, Y. Kim, S. Lin, E. J. G. Santos, M. V. Kovalenko, C.-J. Shih, ACS Nano
2016, 10, 9720.

[3] S. Kumar, J. Jagielski, N. Kallikounis, Y.-H. Kim, C. Wolf, F. Jenny, T. Tian, C. J. Hofer, Y.-C. Chiu, W. J. Stark, T.-W. Lee, C.-J. Shih, Nano Letters
2017, 17, 5277.