bluuebunny/crossref_metadata_2025_split huggingface dataset:
Novel Approaches for Characterizing the Delamination Resistance of Organic Coatings
Authors: Rohwerder Michael , Dandapani Vijayshankar 
Published: February 2020

Based on the results of the pioneering work by Stratmann et al. [1, 2, 3, 4], it may be assumed that corrosion driven delamination of an organic coating should be mainly determined by a few key properties, such as its barrier properties against water, ions and oxygen, its resistance against cation diffusion/migration along its interface to the metal, its resistance against oxygen reduction at this interface and its resistance against radicals produced as side products of this oxygen reduction reaction. Especially the two last properties should define highly delamination resistant coatings. However, so far it was not possible to obtain information about the correlated reaction rates at the buried interface between the organic coating and the metal. Recently, we have developed a novel experimental approach that direct provides information about the oxygen reduction rate at the buried interface as well as on the interfacial degradation resistance [5]. The potential of this technique will be discussed for the case of selected examples.
[1] A. Leng, H. Streckel, M. Stratmann, Corros. Sci. 41 (1999) 547-578
[2] A. Leng, H. Streckel, M. Stratmann, Corros. Sci. 41 (1999) 579-597
[3] A. Leng, H. Streckel, K. Hofmann, M. Stratmann, Corros. Sci. 41 (1999) 599-620
[4] M. Rohwerder, M. Stratmann, MRS Bulletin 24 (1999) 43-47
[5] V. Dandapani, T.H.Tran, A. Bashir, S. Evers. M. Rohwerder, Electrochim. Acta 189 (2016) 111-117
Fundamental Investigation of E-Coat Systems for Next Generation Corrosion Control
Authors: Padash Fardin , Harb John N. 
Published: February 2020

Electrodeposition of coatings is widely used in the auto industry to protect against corrosion. Increased fundamental understanding is needed to enhance the effectiveness of coatings while decreasing the environmental risks associated with surface treatments and coatings, as well as the processes used to form them. In addition, the incorporation of fundamental understanding into modeling tools will help to improve the quality of predictions and ensure that the desired level of corrosion protection is achieved. Fundamentally based models can also provide insight to guide the development and use of new types of environmentally friendly surface pretreatments. Key parameters of interest to the present study include the coulombic efficiency (mass deposited per charge), the coating resistivity, bath conductivity, the degree of neutralization and the extent of amine substitution. The influence of operating conditions such as temperature and flow on these parameters is also critical. In this study, experiments are performed to investigate the influence of factors such as the degree of neutralization and the extent of amine substitution on the size of resin particles in solution and on the processes that render the resin insoluble, leading to deposition. Models are used to describe and quantify critical mechanisms. The impact of key parameters on the local deposition rate and on the coulombic efficiency is demonstrated. The ability to determine the local deposition rate is critical to the performance of large-scale systems and to our ability to predict that performance for a variety of bath compositions, operating conditions, and surface pretreatments.
Zinc Diffusion Coatings on Aluminium for Improved Pitting Resistance
Authors: Lunder Otto , Nordlien Jan Halvor , Lein John Erik 
Published: February 2020

The automotive industry has replaced copper tube based heat exchangers with all-aluminium solutions during the past years in order to reduce weight, material costs and environmental impact. Conversely, the use of aluminium tubing in the HVAC&R (Heat, Ventilation, Air Conditioning and Refrigeration) heat exchanger market is limited due to the much more demanding lifetime requirements. One way of obtaining the required level of safety against failure of aluminium tubing in such applications is corrosion protection by surface modification. This work investigates the effect of surface alloying with zinc on the pitting resistance of heat exchanger tubes.
Pure zinc was applied on flat, thin-walled (≈ 400 µm) multi-port extruded Al-Mn alloy tubes by thermal arc spraying immediately after extrusion, resulting in a sub-micron thick metallic Zn layer on the surface. The tubes were subsequently heat treated to obtain various Zn-rich diffusion layers ranging up to about 70 µm into the alloy substrate. Zn depth profiles were determined by glow discharge optical emission spectroscopy (GD-OES). Corrosion testing was performed by exposure to a cyclic acidified (pH 3) synthetic seawater fog test (ASTM G85 annex A3), normally referred to as the SWAAT test. Open circuit potentials were measured on separate samples as a function of time during immersion in the SWAAT solution at 25 °C. The extent of corrosion as a function of time was determined by weight loss on samples retrieved from the salt spray cabinet at predetermined time intervals for a period of up to eight weeks. The maximum pit depth on each sample was measured by use of a light microscope with a micrometre focusing dial. Ten replicate samples (each 25 mm x 100 mm in size) for each substrate/coating combination were tested, allowing analysis of the maximum pit depth data from extreme value probability plots.
The open circuit potential of the Zn diffusion coated samples in artificial seawater solution was about -0.95 V (SCE), shifting only 10 mV in positive direction during 24 h of immersion. The corrosion potential of the Al-Mn alloy substrate remained constant at -0.74 V (SCE) under similar conditions. The cathodic protection provided by the Zn-rich diffusion layers effectively protected the Al-Mn alloy tubes against formation of deep pits during SWAAT testing. No pits deeper than about 50 µm had formed on the Zn diffusion coated samples after eight weeks of exposure, whereas pit depths exceeding 200 µm was observed on uncoated reference samples already after two weeks. However, weight loss measurements showed that the (uniform) corrosion rate of the anodic Zn-rich diffusion layer was nearly two orders of magnitude higher than that of the Al-Mn alloy substrate under the aggressive low pH conditions prevailing during SWAAT exposure. The results suggest that a lower Zn load than that realizable by thermal arc spraying is required to obtain optimal Zn diffusion profiles in terms of service life of the heat exchanger tubing.
Effectiveness of a TCP Conversion Coating at Inhibitiung Corrosion on AA2024-T3 during so2 Atmospheric Testing
Authors: Swain Greg M , Whitman Brandon 
Published: February 2020

Trivalent chromium process conversion coatings are being investigated as alternates for commonly used chromate conversion coatings on aerospace aluminum allloys. In our studies, the TCP coating is formed by immersion on a polished, degreased and deoxidized specimen. The ca. 100 nm-thick biphasic coating consists of a hydrated ZrO2 layer that is about 50 nm thick with an Al-O-F interfacial layer that is also approximately 50 nm thick. Cr(OH)3 is co-deposited within the hydrated ZrO2 layer at less than 5 at. %. There is a need to better understand the mechanisms by which these coatings inhibit corrosion on these alloys and how well the coatings perform during different accelerated degradation tests. In this presentation, we will report on the formation, chemical composition and electrochemical properties of one commercial TCP coating (Bonderite T5900) on AA2024-T3. The corrosion inhibition provided by the coating depends on the coating bath formulation as well as the physicochemical properties (roughness and elemental composition) of the aluminum alloy after degreasing and deoxidation. The coating provides both anodic and cathodic protection by serving as a barrier layer. In terms of the cathodic inhibition, the kinetics of the oxygen reduction reaction are reduced because the coating functions as a diffusional barrier and coating species chemisorb on Cu intermetallic sites to block O2 chemisorption. In this presentation, we will report on the electrochemical characterization of coated and uncoated AA2024-T3 before and after exposure to a 14-day SO2 atmospheric corrosion test (ASTM G87). SEM and EDXS, optical and stylus surface profilometry and weight loss measurements were used to assess the coating peformance. The results show that the TCP coating is stable on the alloy surface during exposure to the SO2/H2O environment and significantly reduces the corrosion damage and metal loss as compared to the uncoated controls.
Efficiency Potential of Future Generation Solar Cells
Authors: Yamaguchi Masafumi , Lee Kan-Hua , Araki Kenji , Nakamura Kyotaro , Kojima Nobuaki , Ohshita Yoshio 
Published: February 2020

Various solar cells and materials have great potential as future generation solar cells and materials including crystalline Si. Si tandem solar cells such as III-V/Si tandem, II-VI/Si tandem, Chalcopyrite/Si tandem and Perovskite/Si tandem solar cells are expected to have great potential of space and terrestrial application because of high efficiency, light weight and low cost potential. Quantum and Nano structures such as MQWs ‘(Multi Quantum Wells) and QDs (Quantum Dots) are also expected as high-efficiency solar cells. However, there are some problems to be solved. Because point defects in crystalline Si, high density of dislocations and interface recombination in Si tandem solar cell materials and interface recombination in MQWs and QDs affect on solar cell properties, understanding and controlling those defects are very important for realizing higher efficiency. This paper presents analytical results for high efficiency potential of single crystalline Si solar cells, Si tandem solar cells, and MQW and QD solar cells. Although 25.6% efficiency has been attained with hetero-junction and back contact structure and by using bulk minority-carrier lifetime of around 10 msec, high efficiency of more than 27.5% is expected to be realized by increasing bulk lifetime of more than 100 msec Si. Really, high bulk lifetime of around 100 msec has been obtained by the MCZ (Magnetic-field-applied Czochralski) method and decreasing carbon concentration to less than 1014 cm-3 in Si. Understanding behavior of point defects such as Cs-Oi and so forth in Si and decreasing those defects density are suggested for realizing higher bulk lifetime and higher efficiency Si solar cells of more than 27.5%. High efficiency potential of Si tandem solar cells such as III-V/Si tandem, II-VI/Si tandem, Chalcopyrite/Si tandem and Perovskite/Si tandem solar cells is also analyzed by using measure of external radiative efficiency: 43% for III-V/Si 3-J(Junction) tandem, 38% for III-V/Si 2-J tandem, 33% for II-V/Si 2-J tandem, 32% for Chalcopyrite/Si tandem, and 32% for Perovskite/Si tandem solar cells. Effects of dislocations upon minority-carrier lifetime in III-V/Si tandem solar cells are also presented. Our recent result for mechanically stacked InGaP/GaAs//Si 3-junction tandem solar cell with efficiency of 27.4% is shown. Although MQW and QD solar cells are expected as high efficiency solar cells, one of big problems is higher interface recombination near MQWs and QDs because of their lattice mismatching. Lattice mismatch (Δa/a0) dependence of interface recombination velocity (SI) in MQW and QD solar cells is analyzed. Open-circuit voltage drop by interface recombination in
MQWs and QDs and their efficiency potential is discussed.
High-Efficiency Dye-Sensitized Solar Cells with Molecular Copper Phenanthroline As Solid Hole Conductor
Authors: Freitag Marina , Pazoki Meysam , Sveinbjörnsson Kári , Zhang Jinbao , Daniel Quentin , Sun Licheng , Boschloo Gerrit , Hagfeldt Anders 
Published: February 2020

Until recently, there have been no viable alternatives for Spiro-OMeTAD as a hole-transport material (HTM) for dye-sensitized solar cells (DSSC).1 In this study we show that copper phenanthroline complexes in the solid phase can act as efficient molecular hole conductors in DSSCs. Normally, DSSCs utilize a liquid redox electrolyte, but there are significant advantages in replacing it by a solid state hole transport material (HTM): The use of an HTM prevents dye desorption, electrolyte leakage and evaporation problems, as well as making series connection between cells much easier.2 The photovoltaic performance of solid state-DSSCs is, however, usually much lower than its liquid counterparts.3 Here we present a new HTM alternative: bis(2,9-dimethyl-1,10-phenanthroline)copper(I/II) (Cu(dmp)2). This copper complex has a straightforward synthetic route from low cost starting materials.
We prepared solid-state DSSCs with the organic dye LEG44 and Cu(dmp)2 as HTM with a power conversion efficiency of 8.2% under 1000 W m-2AM1.5G illumination, having an open-circuit potential higher than 1.0 V. The successful application of a copper complex-based HTM paves the way for low-cost and efficient hybrid solar cells, as well as other optoelectronic devices. This type of material is anticipated to have large impact on current DSC and MSC research.
(1) Bach, U.; Lupo, D.; Comte, P.; Moser, J. E.; Weissortel, F.; Salbeck, J.; Spreitzer, H.; Gratzel, M. Nature
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(2) Hagfeldt, A.; Boschloo, G.; Sun, L.; Kloo, L.; Pettersson, H. Chem. Rev.
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(3) Bai, Y.; Yu, Q.; Cai, N.; Wang, Y.; Zhang, M.; Wang, P. Chem. Commun.
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(4) Yang, L.; Xu, B.; Bi, D.; Tian, H.; Boschloo, G.; Sun, L.; Hagfeldt, A.; Johansson, E. M. J. J. Am. Chem. Soc.
2013, 135, 7378.

Figure 1
Feasible Strategy Towards Low Temperature Fabrication of Flexible Perovskite Solar Cells
Authors: MA Tingli , Wang Kai 
Published: February 2020

Recent years, organic-inorganic halide perovskite is an increasingly popular and promising candidate as a photovoltaic material for third-generation solar cells.Due to their low cost and considerable charge mobility, inorganic n-type semiconductors such as TiO2, ZnO,and SnO2 are strong ESL candidates and have been used extensively to fabricate highly efficient PSCs. Usually, the compact inorganic ESL films are typically prepared in two steps. The first step involves the spin-coating of the precursor colloidal sol on a conductive substrate, and the second step uses high-temperature annealing to eliminate organic components and to achieve comparable crystallinity. Nevertheless, high-temperature annealing increases production cost and energy payback time significantly; more importantly, such a process is unsuitable for the fabrication of flexible PSCs based on plastic substrate. Hence, it is of great significance to exploit some advanced materials or new technologies for the low-temperature fabrication of inorganic Tungsten oxides (WOx) are common oxide semiconductors with high electron mobility and other special electronic properties. In our previous work, we prepared amorphous WOx at 150 °C as ESL material for PSCs.Nevertheless, when pure WOx was used, the inherent charge recombination and Fermi level (which is lower than that of TiO2) prevents the realization of high photovoltage and PCE. In the present study, we report one facile solution route to successfully fabricate inorganic, amorphous, and WOx-based composite ESLs at the extremely low temperature of 70 °C (or even at room temperature) for efficient planar PSCs. Our sample preparation method requires only two processes: the spin-coating of a precursor solution and drying at low temperature. We will present our latest photoelectrochemical performace of these perovskite solar cells.
Direct Observation of Ferroelectricity and Charge Separation Process in CH3NH3PbI3 Perovskite Solar Cell
Authors: Wang Peiqi 
Published: February 2020

In recent years, organometallic trihalide perovskites has attracted more and more attention for the application of solar cells. In particular, methylammonium (MA) lead triiodide (CH3NH3PbI3 or MAPbI3) has attracted the most attention and undergoes rapid development since it was first applied as light absorber in mesoscopic solar cells. Up to now, it has been demonstrated that the power conversion efficiency of MAPbI3 based solar cells can reach 20%, which is directly related to the favorable direct band gap, high carrier mobilities and long carrier diffusion length. To further improve the performance of MAPbI3 based solar cell, researchers have been focused on studying the otpical, electronic, and optoelectronic properties of MAPbI3 perovskites extensively. However, there is not a systematic study of its ferroelectric properties and the correlation between its ferroelectricity and its optoelectronic properties.
Here, we report our direct observation of the ferroelectric domain structure in MAPbI3 thin film using piezoresponse force microscope (PFM). A strong evidence of the intrinsic ferroelectricity is that the ferroelectric domain structure has no correlation to its crystal domain structure, as shown in figure 1. Besides, we also observed the characteristic butterfly loop and hysteresis loop from pointwise experiment, to further verify the ferroelectricity. In addition to using PFM, we also directly observed the charge separation process by measuring the surface potential with Kelvin probe force microscope (KPFM). Under laser illumination when the charge carriers are generated, the surface potential will either decrease or increase depending on the device structure (p-i-n or n-i-p), which can be probed with KPFM and correlated with the surface topography as well. Our preliminary study shows that with AFM’s capability of localized probing, both the ferroelectric property and the optoelectronic properties can be measured and correlated to the structure, which can help us better understand the role of ferroelectricity in the high performance of organometallic trihalide perovskites.

Figure 1
First-Principles Study of Ion Diffusions in CH3NH3PbI3 and (NH2)2CHPbI3 for Perovskite Solar Cells
Authors: Haruyama Jun , Sodeyama Keitaro , Han Liyuan , Tateyama Yoshitaka 
Published: February 2020

Perovskite solar cells (PSCs), which photo-absorbing layer consists of organometal halide perovskites, have gotten much attention because of their rapidly increasing power conversion efficiencies (3.8% in 2009, but nowadays over 22% cell has appeared). [1, 2] Especially, lead halide perovskites such as CH3NH3PbI3 (MAPbI3) and (NH2)2CHPbI3 (FAPbI3) show remarkable properties for solar cell applications, e.g. high optical absorption coefficients and long diffusion lengths of both charge carriers. However, the current−voltage (J−V) curve of PSCs often depends on voltage sweep rates and sweep directions, [3, 4] which make the evaluation of conversion efficiency difficult. Recently, the rate-dependent J−V hysteresis, which is due to a slow process continued about seconds, was attributed to ionic diffusions in MAPbI3. [5]
In this study, we calculated activation barriers of ion diffusions in tetragonal MAPbI3 and trigonal FAPbI3 by first-principles calculations. The vacancy migrations of I− anions in both perovskites show low barriers of 0.3 to 0.45 eV, which values indicate that MAPbI3 and FAPbI3 are ion conductors. Furthermore, MA+ and FA+ cations have rather low barriers c.a. 0.6 eV. The results strongly suggest that the not only anions but also molecular cations can migrate in the perovskites when a bias voltage is applied. Based on the dilute diffusion theory, we can expect that small vacancy concentrations suppress these ion conductions. In addition, we suggest that replacement of MA molecule with larger one is also able to reduce MA migrations and to prevent the degradation of PSC photo absorbers. [6]
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[2] Best Research-Cell Efficiencies, National Renewable Energy Laboratory. http://www.nrel.gov/ncpv/images/efficiency_chart.jpg
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(Invited) Resistive Switching in Mott Insulators: From Fundamentals to Mott Memories
Authors: Tranchant Julien , Janod Etienne , Corraze Benoit , Querré Madec , Besland Marie-Paule , Cario Laurent 
Published: February 2020

The application of short electrical pulses on narrow gap Mott insulators gives rise to a new phenomenon of resistive switching. This transition is volatile above threshold electric fields of a few kV/cm and stabilizes into a non-volatile RS for higher electric fields. Our works have shown that this phenomenon is driven by the electric field, which triggers an electronic avalanche [1]. This avalanche provokes the collapse of the Mott insulating state at the nanoscale [2] and generates the formation of granular conductive filaments. The resulting non-volatile transition is reversible and these materials have the ability to switch back and forth between two resistance states with possible intermediate levels. This phenomenology was first evidenced on the family of chalcogenide compounds AM4Q8 (A=Ga,Ge; M=V,Nb,Ta,Mo; Q=S,Se), either on single crystals or on thin films [3]. We have recently demonstrated that these properties are actually universal to all canonical Mott insulators such as (V1-xCrx)2O3 or NiS2-xSex [4]. In the V2O3:Cr system, these new results indicate that, beyond temperature for V2O3 and pressure for (V1-xCrx)2O3, a third tuning parameter, electric field E, is prone to induce an reversible Insulator to Metal transition. This is particularly interesting since these E-induced transitions can occur at room temperature and are hence suitable for applications. Our last results demonstrate that (V1-xCrx)2O3 thin films can be deposited by reactive magnetron co-sputtering [5]. We show that this deposition technique allows controlling the Cr content, oxidation degree and crystallinity after ex-situ annealing. Our last results demonstrate that (V1-xCrx)2O3 thin films can be deposited by reactive magnetron co-sputtering [5]. We show that this deposition technique allows controlling the Cr content, oxidation degree and crystallinity after ex-situ annealing. Our first results on metal-insulator-metal (MIM) devices show that we retrieve the electric-field-induced resistive switching on these TiN/(V1-xCrx)2O3/TiN symmetric ReRAM cells. The characterization of these Mott memory single cells demonstrate very competitive performances which place narrow gap Mott insulators as promising candidates for ReRAM and memristor applications [6].
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