bluuebunny/crossref_metadata_2025 huggingface dataset:
Does DUAL Layer Cathode Increase the POWER Density of Lithium-ION Batteries ?
Authors: Asselah Islam Samah
Published: May 2020

Lithium-ion batteries is one of the most popular technological innovations for storing electrical energy also in the automotive field. They have many advantages due to lithium’s high storage capacity to weight ratio. Lithium also has the highest voltage and thus practical best energy density of all metals. One of the problems encountered with lithium-ion batteries in the automotive field is the poor power capability. Optimizing the lithium-ion battery performances is a trade-off between energy and power density. To increase the energy density, we need to increase the electrode density, the thickness and minimize redox inactive components. However, to improve power performance we must increase the electrolyte transport in the electrode, which entails lowering the active material fraction as well as the thickness. Moreover, combining several different active materials individually optimized for high power or high capacity may assist in attaining the optimal performance for a given application.

In this project, the main goal is to have an analytical handle on the performance of a cathode which is composed of a double layer LiFePO4 and LiNi1/3 Mn1/3 Co1/3 O2 and compare them to their respective single layer (figure1). We study their behavior separately within the double layer structure using a specific current density and their unique potential windows. For the characterization, we are using galvanostatic cycling, chronoamperometry and scanning electron microscopy to relate the electrode performance to their morphology. We also compared the dual layer performance with that of blended electrodes, i.e. a blended mixture of both materials rather than separate layers (figure1).

Figure 1
(Keynote) Nanomaterials for Printable Electronics
Authors: Malenfant Patrick R. L.
Published: May 2020

The National Research Council (NRC) is Canada’s premier organization for research and technology development. NRC’s Printable Electronics (PE) program develops materials and inks for additive manufacturing in order to enable a sustainable PE sector in Canada. Progress has been made over the last 20 years, yet many challenges remain at the materials, fabrication and integration level, limiting performance and commercialization. This presentation covers our progress in high purity semiconducting single-walled carbon nanotube (sc-SWCNT) enrichment and transistor fabrication via solution based processes as well as conductive molecular ink development [1-11]. I will highlight our recent progress in understanding sc-SWCNT enrichment using conjugated polymers (isolation of high purity sc-SWCNT), with special consideration given to the effects of solvent parameters and doping on the mechanism and yield/purity of the final product [2-4]. Removal of the wrapping polymer using a dry process on-wafer will also be described [5]. Challenges and advances associated with using polymer-based dielectrics and encapsulants will be discussed as well [6-7]. Such transistor packages have enabled the realization of fully inkjet-printed transistors as a result of the excellent electrical properties of sc-SWCNTs [8]. A demonstration of a fully additive process to make TFT backplanes via R2R printing will also be highlighted. Developments in conductive molecular inks and progress towards the commercialization of new applications such as in-mold electronicswill also be described [9-11]. The development of new functional nanomaterials and their successful integration into devices will enable additive manufacturing of TFT arrays and in-mold electronics.

[1] J. Lefebvre et al. Acc. Chem. Res. 50, 2479 (2017).

[2] J. Ouyang et al. ACS Nano 12, 1910 (2018).

[3] J. Ding et al. J. Phys. Chem. C 120, 21946 (2016).

[4] Z. Li et al. ACS Omega 3, 3413 (2018).

[5] Z. Li et al. Adv. Funct. Mater. 28, 1705568 (2018).

[6] J. Lefebvre et al. Appl. Phys. Lett. 107, 243301 (2015).

[7] F. Lapointe et al. Appl. Mater. Interfaces 11, 36027 (2019).

[8] C. Homenick et al. ACS Appl. Mater. Interfaces 8, 27900, (2016)

[9] A. J. Kell et al. ACS Appl. Mater. Interfaces 9, 17226 (2017).

[10] C. Paquet et al. Nanoscale 10, 17226 (2018).

[11] B. Deore et al. ACS Appl. Mater. Interfaces 11, 38880 (2019).
(Invited) Carbon Nanomaterials for Energy Applications
Authors: Bekyarova Elena
Published: May 2020

Bridging the performance gap between batteries and supercapacitors is an area of active research driven by the increased importance of effective solutions for energy storage. A promising trend in this area is the development of novel materials that afford design of architectures combining the advantages of both energy storage devices. Batteries, which operate based on Faradaic processes taking place in the bulk of the active electrode materials (chemical mechanism of storage), exhibit high energy, but suffer from slow charge and discharge rates. On the other hand, supercapacitors deliver high power at the cost of low energy storage by making use of surface ion adsorption (double-layer capacitance, physical mechanism of storage) and surface redox reactions (pseudo-capacitance). Carbon nanomaterials, including carbon nanotubes and graphene, are potential candidates for the preparation of electrodes operating at high current rates. This talk will discuss the performance of electrodes prepared from carbon nanomaterials and their specific benefits when assembled with nanostructured cathodes into full cells. The cells are characterized for energy density, power density, rate capability and cycling stability.
(Invited) Global Malaria Endemic and the Industrial Physics Challenge of Cost-Effective Nanoparticle Quantification
Authors: Menon Naresh , Lukaszewicz Agnes , Kyubwa Espoir
Published: May 2020

Malaria counts among the worst scourges of humankind, accounting for some 500 million clinical cases per year and more than one million deaths. Approximately half the world’s population lives in regions where malaria is endemic, amounting to an immense health burden and inhibiting economic prosperity in numerous countries. Currently, there is no point-of-care (POC) diagnostic test that meets the need of highly-sensitive malaria screening tool for low-resource settings. To address this global challenge, through funds from the NIH, we are developing a portable device for quantifying hemozoin in blood; a dichroic paramagnetic nanoparticle that is a byproduct of hemoglobin digestion by all malaria parasites. Hemozoin is an attractive target for developing drugs and is released into circulation during red blood cell lysis. It has been shown that parasitemia is proportional to hemozoin concentration in blood. While it has been shown that by exploiting the unique magnetic and optical anisotropy properties of hemozoin, as few as 30 malaria parasites per mL of blood could be identified. However, this process requires complex instrumentation and is not conducive for a cost effective, rugged, mobile, POC diagnostic system. In this presentation, we will discuss the challenge, how we are approaching it through a multi-science approach that includes physicists, biologists and chemists and our progress to date.
Corrosion Mitigation By Photocatalytic Effect of TiO2 Coating on Low Carbon Steel
Authors: Kao Wei-Sheng , Yeh Tsung-Kuang , Wang Mei-Ya
Published: May 2020

Titanium dioxide (TiO2) is one of the most commonly used photocatalyst at the field of environmental remediation and energy applications. TiO2 is an n-type semiconductor that can be excited by photon irradiation to generate electron-hole pairs in its space charge layer under UV illumination. The excited electrons in the conduction band are then transferred to the metal surface, leading to decrease in both the corrosion potential and the oxidation reaction rate of the metal.

In this study, the photoelectrochemical behavior of the carbon steel with TiO2 coating by sol-gel method were investigated to preventing or minimizing the atmospheric corrosion. Various oxide structure of carbon steel and the TiO2 annealing process were also investigated in this study.

The crystallinity of TiO2 was analyzed with grazing incident X-ray diffraction (GIXRD) and the interfacial oxide layer composition and thickness were analyzed via the Raman spectroscopy and SEM, respectively. Potential dynamic analyses and open circuit potential (OCP) measurement were carried out under a designated solution to evaluate the corrosion mitigation of the TiO2 coated carbon steel with or without UV illumination. These results indicated that the TiO2 treatment with UV illumination would effectively reduce the carbon steel corrosion rate in atmospheric environments.
Scanning Micropipette Contact Method Images Corrosion Related Electrochemical Activities on Al Alloy Surface
Authors: Li Yuanjiao , Mauzeroll Janine , Morel Alban
Published: May 2020

Scanning micropipette contact method (SMCM) is powerful in mapping electrochemical activities of a surface at a high spatial resolution and revealing the surface heterogeneities. Al alloys is heterogeneous in composition resulting in different corrosion rates over the surface. By approaching the electrolyte solution filled micropipette to the sample, a micro electrochemical cell can be formed on the predefined location upon the droplet at the end of pipette touches the surface, where electrochemical measurements including polarization test and Ecorr vs time could be conducted locally. SMCM maps can clearly reveal the locations and electrochemical properties of the inclusions which agree with the SEM images and EDX analysis.
Modeling and Experimental Validation of Critical Distance and the Maximum Depth of Galvanic Corrosion-Induced Pitting on the 2024-T3 with CFRP Joint
Authors: Yıldırım Mustafa Anıl , Erdogan Metehan , Karakaya Ishak
Published: May 2020

For today's aviation industry, reducing fuel consumption in aircrafts has become one of the most important goals. Therefore, the use of lightweight materials, such as CFRP (carbon fiber reinforced plastic), aluminum, magnesium, or titanium has increased. Different combinations of materials that may be electrically in contact with each other in the presence of moisture cause galvanic corrosion. Especially, pits caused by galvanic corrosion jeopardize the structural strength of an aircraft. Within the scope of this work, an experimental setup was developed for the validation of a finite element model (FEM) for simulating galvanic corrosion of 2024-T3 sheet and CFRP in a 5 wt% NaCl solution. Corrosion parameters of both materials were determined separately by potentiodynamic polarization experiments. The critical distance for galvanic corrosion-induced pitting on the aluminum alloy surface and the maximum pit depth were determined by FEM and confirmed by immersion tests in the same environment.
Microstructual and Chemical Analysis of Surface Treated Metal Foam Anode for Li Rechargeable Battery
Authors: Ahn Tae-Young , Choi Yu Song , Kim Jiyoun , Cho Jang-Hyeon
Published: May 2020

As the amount of power consumed by electronic products increases, a lot of studies focused on high capacity and miniaturization of batteries. In order to overcome the low capacity of carbon anode in Li rechargeable battery, researches on the development of high capacity anode material have been conducted. In particularly, it has been reported that pure lithium was adopted for high capacity of Li ion battery due to its light in weight and excellent theoretical capacity. However, when pure lithium is used, the capacity decreases rapidly as charging and discharging proceeded, which is reported to be formation of dendrite on the Li surface during charging/discharging. In order to suppress the growth of dendrite during charging/discharging, several researches have been focused on the Li impregnated metal foam for Li rechargeable battery. However, due to the poor wettability between metal foam and pure Li, adhesive materials had to be deposited by using expensive processes such as chemical vapor deposition to impregnate the Li into metal foam.

In this study we focus on the heat treatment effect on the microstructure and Li-impregnation property of Ni metal foam. We oxidized the metal foam in a high temperature(500-900oC) for 5 min using the furnace to improve the wettability between the Lithium and Ni metal foam. Heat treated metal foam was dip into melted Li at 400 oC in a glove box. As a result, the rate of Li-impregnation in the heat treated metal foam was more than 10 times faster than that of the untreated Ni metal foam. The surface of heat treated Ni metal foam was characterized using transmission electron microscopy (TEM) equipped with energy dispersive X-ray spectroscopy(EDS). Figure. 1 shows the TEM image of the untreated and heat treated Ni metal foam surface. It reveals that an additional layer having a thickness of 200 nm was observed in the heat treated Ni foam. The additional layer was identified as polycrystalline NiOx by EDS and selected area diffraction pattern (SADP). It is believed that formation of NiOx was greatly contribute to improvement of the impregnation characteristics. In addition, the impregnation characteristics of Ni alloy foam will be discussed in this presentation.

Figure 1
Highly Enhanced Pseudocapacitive Performance of Vanadium-Doped Mxenes in Neutral Electrolytes
Authors: Gao Zhiwen , Lee Lawrence Yoon Suk
Published: May 2020

Two-dimensional (2D) titanium carbide (Ti3C2Tx MXene) has been recognized as a promising material for pseudocapacitor electrodes in acidic solutions, while the current studies in neutral electrolytes show much poorer performances. By a simple hydrothermal method, we prepared vanadium-doped Ti3C2Tx 2D nanosheets to tune the interaction between MXene and alkali metal adsorbates (Li+, Na+, K+) in the neutral electrolyte. Maintaining the 2D morphology of MXene, the co-existing V3+ and V4+ are confirmed to form surface V-C and V-O species. At a medium doping level of V:Ti = 0.17:1, the V-doped MXene exhibits the highest capacitance of 365.9 F g-1 in 2 M KCl (10 mV s-1) and excellent stability (5% loss after 5,000 cycles), compared to only 115.7 F g-1 of pristine MXene. DFT calculations reveal the stronger alkali metal ion-O interaction on V-doped MXene surface than unmodified MXene and a further capacitance boost to 404.9 F g-1 using Li+-containing neutral electrolyte is reported, which is comparable to the performance under acidic conditions.

Figure 1
Flexible Self-Chargeable Sodium-Ion Battery for Soft Electronics
Authors: Zhou Dan , Wang Ning
Published: May 2020

Exploring the concept of soft energy unit with improved sustainability and flexibility is critically important for the development of wearable electronics that comes into direct contact with human tissues. In this work, a flexible and self-chargeable sodium-ion full battery was developed by coupling elastic piezo-films with the separator of flexible sodium-ion batteries. This new device achieves excellent flexibility and self-charging performance. It can not only be charged to about 0.65 V under mechanical bending in 150 s or palm patting within 300 s, but also demonstrates interesting self-charging behavior even with quasi-static pressing. In the latter case, the self-charging rate increases with the rising of the applied static forces, which can be ascribed to the sound elasticity of the piezo-film. This work contributes to the development of flexible and self-chargeable electrochemical power devices for soft wearable electronics.

Reference

[1] D. Zhou, L.P. Xue, L. Wang, N. Wang, W.-M. Lau, X. Cao. Nano Energy 2019, 61, 435–441.

[2] N. Wang, W. Dou, S. F. Hao, Y. Cheng, D. Zhou, X. M. Huang, C. Jiang, X. Cao. Nano Energy 2019, 56, 868–874.

[3] D. Zhou, L.-P. Xue, N. Wang. J. Alloys Compd. 776 (2019) 912-918.

Figure 1
Effect of Zn2+ on Cathodic Reaction of Carbon Steel in Aqueous MgCl2 Solutions
Authors: Tada Eiji , Ooi Azusa , Nishikata Atsushi
Published: May 2020

We have shown that zinc dissolution is accelerated in relatively high concentrations of MgCl2 during the galvanic corrosion process consisting of zinc and carbon steel. In this study, in order to understand further the galvanic corrosion process of zinc and carbon steel in MgCl2, the cathode reaction on carbon steel was investigated in MgCl2 aqueous solution with and without Zn2+ which is generated during the galvanic corrosion process.

The sample used for the experiment was carbon steel SS400 (Fe-0.12C-0.60Mn-0.011P-0.019S) machined to a shape of 1.5 × 1.5 × 0.3 cm3. One side of this sample was ground up to #2000 grit with SiC abrasive papers and then degreased and washed in acetone before use in the following experiments. The test solutions were mixtures of 0.25 M MgCl2 and x mM ZnCl2 (x = 2.5, 5 mM, Mg / Zn molar ratio: 100, 50) and they were used at room temperature under a naturally aerated condition. As reference solutions, the mixtures of 0.5 M NaCl and y mM ZnCl2 (x = 5, 10 mM, Na / Zn molar ratio: 100, 50) with the same Cl- concentration were used. The cathodic polarization curve measurements were done by a conventional three-electrode method with a platinum wire as a counter electrode and an Ag / AgCl electrode (saturated KCl, SSE) as a reference electrode. The potential sweep rate was 0.5 mV/s

On the cathodic polarization curves for carbon steel measured in an aqueous MgCl2 solution containing Zn2+, the diffusion-limiting current region due to the cathodic reduction reaction of dissolved oxygen (ORR) was observed from -0.6 V to -0.8 V, and the magnitude of the limiting currents were almost the same regardless of the Zn2+ concentration. Furthermore, the cathodic polarization curves showed that an increase in the current due to the hydrogen evolution reaction (HER) occurred in the MgCl2 solution without Zn2+. By comparison with the cathodic polarization curve measured in the NaCl solution without Zn2+ showed a diffusion-limiting current of ORR was comparable to that in the MgCl2 solution, but the overvoltage of HER was increased by about 0.1 V. These results indicated that in the MgCl2 solution, HER on carbon steel was enhanced more than that in NaCl aqueous solution.

On the other hand, in the MgCl2 solutions containing Zn2+, a shoulder was observed in the cathode polarization curve at around -0.95 V, and the the current due to HER was decreased with increasing the Zn2+ concentration. It was shown that HER was suppressed in MgCl2 solutions by the presence of Zn2+. This may be attributed to the precipitation of zinc corrosion products formed during cathodic polarization.
Analysis of Steel Samples Collected from Power Plant Water Cycles Using Electrochemistry and Electron Microscopy
Authors: Hall Derek M. , Shulder Stephen J. , Lvov Serguei N.
Published: May 2020

One aspect of effective steam/water cycle chemical treatment programs is their ability minimize corrosion and corrosion related failures. In this study, we examine how corrosion product layers on the surface of tubing samples impact corrosion rate for a series of test specimens prepared from boiler/steam piping provided from operating power plants. Corrosion rates were estimated using the following electrochemical techniques: linear sweep voltammetry (LSV), linear polarization resistance (LPR) and electrochemical impedance spectroscopy (EIS). Two sources of Tafel slopes were the standard assumptions used if the corrosion mechanism is not known and those obtained from LSV curves. In total, five variations of corrosion rate measurements were compared. For these corrosion tests, water chemistries representative of conditions that induced online hydrogen damage and offline pitting were used. Field emission scanning electron microscopy (FESEM) and energy dispersive X-ray spectroscopy (EDS/EDX) were the electron microscopy techniques applied to examine the corrosion product layers. Using these techniques, the microstructure and elemental composition of the tubing sample corrosion product layers were examined. These techniques could be utilized to evaluate the effectiveness or reduction in corrosion rates with the application of film forming products.
Analyzing Galvanic Corrosion Behavior of Metal Alloys Based on First-Principles Simulations
Authors: Wang Yaowei , Xie Tian , Luo Zhe , Zhu Hong , Zeng Xiaoqing
Published: May 2020

Galvanic corrosion behaviors of alloys have usually been investigated through experiments, where the measured polarization curves, the corrosion potential and current could differ a lot between different literature. Herein, we proposed a semi-empirical model based on the mixed potential theory and first principles calculation to analyze the galvanic corrosion of the metal alloys. Our model is further validated in the case of Mg-Ge alloys, which is composed of anode Mg matrix and cathode Mg2Ge second phase. The combination of the large anode equilibrium potential difference between Mg and Mg2Ge, and the Schottky barrier across the interface indicates that the Mg2Ge second phase can prevent the Mg grain from serving as the cathode and impede the electron transfer between the Mg grains. First principles calculations on the kinetics of hydrogen evolution reaction upon Mg2Ge reveal that the rate-determining step is the hydrogen adsorption, which is extremely energetically unfavored but an inevitable intermediate state. The estimated exchange current of the hydrogen evolution upon Mg2Ge is about 3 orders of magnitude smaller than that on pure Mg, indicating the depressed galvanic corrosion of the Mg-Ge alloys is also the result of the low hydrogen exchange current upon Mg2Ge. Moreover, some typical intermetallics, such as MgZn2 and MgSc, were selected to compare the corrosion properties of different Mg alloys, which is in close agreement with the experimental observations. Our model to predict the galvanic corrosion behavior provides a promising perspective for designing better corrosion-resistant metal alloys.
Composite Epoxy Coating Reinforced by Silane-modified Micro-Al2O3 Particles for Long-time Anti-corrosion Protection in Solution of Seawater Salinity
Authors: Lu Qingye , Yu Mingdong
Published: May 2020

Marine pipelines in subsea oil and gas production systems are exposed to very corrosive high salinity condition and demand high anti-corrosion coatings. Superhydrophobic particles have long been used to make the rough structure of the superhydrophobic surface for anti-corrosion protection. Epoxy coatings are considered to be one of the best protective method for metals because the epoxy resins have very good chemical resistance, strong adhesion to the substrate, good mechanical and insulating properties. However, the application of epoxy coatings has been limited in many cases due to their characteristics such as brittleness and sensitivity to micro-cracks owing to their three-dimensional network structure, low impact toughness, and poor fatigue property. In recent years, second phase particles for toughening the epoxy matrix have attracted a lot of attention. A noticeable increase in both the shear strength and adhesive peel strength appeared mainly due to high levels of dispersion of the high modulus nanoparticles and effective interfacial interactions with the epoxy matrix. Many studies have reached similar conclusions.

So far, numerous studies have been performed to determine the effect of adding reinforcement inorganic particles on the wear and erosion resistance of the epoxy coatings, and the electrochemical characterization of those particle-reinforced epoxy coatings was normally studied for short exposure time. However, no studies have been carried out on the corrosion resistance properties of superhydrophobic particle-reinforced epoxy coatings with long exposure time in corrosive solution.

This work aims the development of superhydrophobic micro-Al2O3 as reinforced particles for epoxy coating under long-time exposure to solution of seawater salinity, and comparison of the effects of using hydrophilic and superhydrophobic micro-Al2O3 as reinforced particles on the protection property of epoxy coating. Epoxy composites filled with both silane functionalized Al2O3 (SF-Al2O3) and unfunctionalized Al2O3 (UF-Al2O3) were fabricated at a filler loading of 26 vol.% micro-particles. The SF-Al2O3 particles exhibited a water contact angle of 156.5°. Electrochemical testing including open circuit potential, impedance and phase angle measurements showed that SF-Al2O3 epoxy have better corrosion resistance as compared to pure epoxy after 144 d immersion in solution of seawater salinity (3.5 wt% NaCl), while the coatings with UF-Al2O3 showed failure after 36 d immersion. Scanning electron microscope analysis revealed a very good condition of the SF-Al2O3 epoxy coating after 144 d immersion. It is clearly observed that silane-modified particles were very effective on the anti-corrosion protection property of composites in high salinity solution. The results may have important implications for the design of particles reinforced polymeric composite coatings.
The SCC Behavior of E690 Welded Joint in Thin Electrolyte Film Containing Sulfur Dioxide
Authors: Ma Hongchi
Published: May 2020

E690 steel, as a newly-developed high strength steel in recent years, is of great potential to be widely used in offshore platforms in the near future. Since the stress corrosion cracking (SCC) susceptibility of high strength steel increases sharply with the strength, E690 may experience risks of stress corrosion cracking (SCC) and therefore catastrophic failures when used in marine environment, especially in polluted marine atmosphere containing SO2. In general, the welded joints have lower mechanical strength compared to the majority of the steel structure and are considered more vulnerable to corrosion and stress corrosion cracking. In this study, slow strain rate tests (SSRT) and electrochemical measurements, combined with metallographic analysis and micro-hardness tests, were employed to investigate the behavior and mechanism of SCC in the E690 welded joint. The metallographic observation revealed at least three different microstructure types in the heat affected zone (HAZ) of E690 welded joint, including coarse grained heat affected zone (CGHAZ), fine grained heat affected zone (FGHAZ) and intercritical heat affected zone (ICHAZ). CGHAZ exhibited the highest micro-hardness. FGHAZ showed a little lower micro-hardness than base metal (BM). And the micro-hardness of ICHAZ was equal to or even lower than that of BM. The results showed that the E690 welded joint had a very high SCC susceptibility in thin electrolyte film containing sulfur dioxide. From the fracture morphologies, distinct characteristics of brittle fracture were observed. The plasticity index in SO2 atmosphere was significantly decreased compared to that in air, showing the loss percentage of elongation and area reduction up to 30.0 % and 36.9 %, respectively. After etching, the morphology of the cross-section indicated that ICHAZ of the welded joint was the most susceptible location to SCC due to its more negative potential and higher corrosion current density from the electrochemical measurements. Fracture morphology showed that stress corrosion cracks were more likely to initiate and extend along the interface of martensite-austenite (M-A) island and adjacent ferrite.
Photoelectrochemical Cathodic Protection Effect of Bi2S3/TiO2 nanorod Array Composite Film for Stainless Steel
Authors: Du Rong-Gui , Hu Juan , Jin Piao
Published: May 2020

TiO2 nanomaterials have long been a topic of interest for applications in various fields due to their special photoelectrochemical properties. However, there are some problems for practical applications of a pure TiO2 film. TiO2 can only be excited by ultraviolet light and its photoelectric conversion efficiency is low due to the high electron-hole recombination rate. In order to overcome these problems, many methods have been developed to modify TiO2 films for improving their photoelectrochemical properties.

In this work, we fabricated a Bi2S3 modified rutile TiO2 nanorod array film on FTO conductive glass for achieving a good photoelectrochemical cathodic protection effect on 403 stainless steel (403SS) in a NaCl solution.

A single crystalline rutile TiO2 nanorod array film was prepared by a typical hydrothermal reaction method. A FTO substrate (10 mm × 15 mm × 2.2 mm) was immersed in a TiCl4 solution and thermally treated in an electric oven at 70 ℃ for 30 min. After that, the FTO specimen was annealed at 550 ℃ in air for 1 h. Then the specimen with the TiO2 seed layer was immersed a mixed aqueous solution of TiCl4 and HCl, and heated in an electric oven at 150 ℃ for 10 h. Bi2S3 nanoparticles was prepared on the TiO2 ﬁlm by a typical chemical bath deposition method. The TiO2 ﬁlm sample was alternately immersed in the Bi(NO3)3 ethylene glycol solution and the Na2S aqueous solution for 1 min. After each immersion, the film sample was dried at 80 ℃ for 5 min. This operation cycle was repeated for 15 times. Finally, the film sample was annealed at 240 ℃ for 4 h in a N2 atmosphere.

The prepared films were characterized by scanning electron microscopy (SEM), X-ray diffraction (XRD) and X-ray photoelectron spectroscopy (XPS), and their photoelectrochemical properties and photocathodic protection effects were investigated.

The results indicated that the prepared TiO2 film was composed of the nanorod array. The TiO2 in the film was highly crystallized and agreed well with the rutile phase, and Bi2S3 nanoparticles were successfully deposited on the TiO2 film. The photoresponse of the Bi2S3/TiO2 composite film was extended into the visible light region, and its photoelectrochemical properties were enhanced. Under white light illumination, the Bi2S3/TiO2 composite film as a photoanode could make the potential of 403SS in a 0.5 M NaCl solution decrease by 695 mV (relative to its corrosion potential), showing a more effective photoelectrochemical cathodic protection effect than the pure rutile TiO2 nanorod film, which is of significance for environmentally friendly corrosion control of metals.

This work was supported by the National Natural Science Foundation of China (Nos. 21573182, and 21173177).
Corrosion Protection of 6061 Aluminum Alloy By Cerium Electrodeposition Using a Deep Eutectic Solvent
Authors: Aldana-González Jorge , Díaz de León Oscar , Sánchez William , Sánchez-Vite Enrique , Montes de Oca Yemha María Guadalupe , Romero-Romo Mario Alberto , Arce-Estrada Elsa , Palomar-Pardavé Manuel
Published: May 2020

In this work, a study of the electrodeposition of Ce onto an aluminum 6061 alloy was carried out from Ce salt dissolution in a deep eutectic solvent formed by choline chloride and urea at 70 °C, to increase the alloy’s corrosion protection in saline media (3.5% NaCl). In order to corroborate that the deposit is formed by metallic Ce, surface characterization was carried out by SEM and EDX, which allowed verification that up to 41.33% Ce was deposited on the Al alloy after applying a potential of -1.45 V for 3000 seconds. Electrochemical impedance spectroscopy (EIS) led to determining the corrosion resistance of the modified material and the corrosion inhibition efficiency of 92%, with respect to the blank in 3.5% NaCl.

Figure 1
Kinetics of Pyrite Oxidation in Simulated Mine Tailings Pond Conditions
Authors: Nablo Geoffrey Ray Laviste
Published: May 2020

Pyrite oxidation is the predominant source of acid mine drainage (AMD), which is one of the severe environmental impacts of mining. AMD destroys flora and fauna in the nearby ecosystem, and it causes grave health problems to the people. To further the understanding and help in the mitigation of AMD, this electrochemical study investigates the effect of the type and concentration of oxidant, and the presence of impurity (chalcopyrite) to the rate of pyrite oxidation, while simulating the conditions in tailings ponds.

Open Cell Potential (OCP) and Electrochemical Impedance Spectroscopy (EIS) analysis were done using a three-electrode cell set-up, which is composed of a pyrite rotating disc electrode (RDE), mercury/mercurous sulfate reference electrode in saturated potassium sulfate, and a platinum counter electrode, with a sulfuric acid working electrolyte. Polarization resistance obtained after fitting an electrical circuit to the EIS data was related to the rate of pyrite oxidation, while OCP was used to describe its oxidation mechanism. It was found out that the oxidation of pyrite by ferric ions preferentially occurred rather than by dissolved oxygen. The parameter setting with the lowest relative oxidation rate were: electrolyte with no ferric addition, and with nitrogen purging; and RDE with 10 % chalcopyrite addition. Reaction orders calculated for the effect of ferric ions and dissolved oxygen were equal to 1; but ferric has a higher slope value in the plot. Presence of chalcopyrite in the RDE caused the preferential oxidation of chalcopyrite instead of the pyrite due to their galvanic interaction. To minimize pyrite oxidation, ferric and dissolved oxygen concentration should be minimized, and chalcopyrite impurities should be increased.

Keywords: Electrochemical Impedance Spectroscopy, Acid Mine Drainage, Kinetics, Rotating-Disc Electrode, Pyrite
Addition of Functionalized Graphene Oxide in Smart Cataphoretic Coating
Authors: Rossi Stefano , Calovi Massimo , Benedetti Luca , Deflorian Flavio , Dirè Sandra , Ceccato Riccardo
Published: May 2020

Graphene is a particular type of material, made of a single crystal lattice layer of two dimensional honey-comb structure with excellent electrical, thermal and mechanical properties.

Graphene oxide (GO) has been subjected to several studies in recent years. One of its possible applications concerns the production of composite coatings, to improve the protective properties of the coating itself together with other functional properties such as a remarkable conductivity.

The cataphoretic electrodeposition process allows to obtain a coating with uniform thickness also with complex geometry, good adhesion properties, in a simple and economic way. To get good properties it is important to have a uniform distribution of graphene flakes, avoiding cluster formation, together with good adhesion between graphene particles and organic matrix.

In this work, the effect of the graphene flakes addition in the organic coating was studied.

The graphene flakes have been subjected to nitric acid oxidation treatment and functionalized with organosilane, to get a good dispersion in the acrylic cataphoretic bath.

The deposits’ morphology was observed under optical and electronic microscope, to study the possible defectiveness of the coatings. The corrosion protection properties were evaluated by salt spray exposure test following the ASTM B117 standard and by electrochemical impedance spectroscopy measurements in chloride solution. The process parameters, as well as the concentration of functionalized graphene oxide inside the cataphoretic bath, have been optimized, obtaining composite coatings with excellent corrosion resistance properties. It has been verified that the presence of graphene in the cataphoretic coating allows to obtain a better behavior in an aggressive environment and corrosion protection of the metallic substrate. Finally, deposit conductivity was measured following ASTM D 257-07 standard.
Cerium Conversion Coating for Corrosion Protection of Medium-Entropy Alloy
Authors: Chen Li-An , Lu Yi-Sheng , Yen Hung-Wei , Lee Yueh-Lien
Published: May 2020

It was found that Fe50Mn30Co10Cr10 medium entropy alloy (MEA) had superior mechanical properties higher than those of CoCrFeMnNi high entropy alloys (HEA). However, poor corrosion due to the higher manganese content is one of the main challenges restricting the further application of Fe50Mn30Co10Cr10 MEA. In order to improve the corrosion resistance of MEA, a new cerium chemical conversion coating based on a mixed solution of Ce(NO3)3．6H2O and H2O2 has been first proposed in this study. The electrochemical behavior of bare and coated samples was evaluated by using potentiodynamic polarization and electrochemical impedance spectroscopy (EIS). In addition, Field Emission Scanning Electron Microscope (FE-SEM), Transmission Electron Microscope (TEM), Auger Electron Spectroscopy (AES) and X-ray Photoelectron Spectroscopy (XPS) were utilized to characterize the microstructure and composition of the coatings. The preliminary results showed that, from the potentiodynamic curves, the corrosion potential increases and the corrosion current density decreases by one order of magnitude for Ce-coated sample. Also, the cerium conversion process improves the pitting potential of the Fe50Mn30Co10Cr10 MEA. The AES result revealed that the thickness of cerium conversion film formed on the surface of Fe50Mn30Co10Cr10 MEA is around 25 nm.
Performance Optimization Based on Modeling of a Molten Carbonate Direct Carbon Fuel Cell
Authors: Song Datong , Xie Zhong , Zhang Xinge , Qu Wei , Wang Qianpu
Published: May 2020

A direct carbon fuel cell (DCFC) converts the chemical energy in the carbon fuel directly into electricity without gasification and is considered as one of the most promising and highly efficient technologies in power generation, CO2 capture and sequestration. A molten carbonate direct carbon fuel cell uses solid carbon as fuel and molten carbonate as electrolyte. Modeling simulation, as a powerful complementary tool, can provide insights or guidance on where and how DCFC performance can be improved. In this work, a unit cell model for a molten carbonate DCFC is first presented. Second, a mathematical description of the performance optimization problem for the molten carbonate DCFC is proposed in which the working current density under a specified voltage is taken as the objective function and some geometrical parameters, such as porosity, solid material volume fractions, are taken as the optimization variables. The mathematical optimization problem is solved by using MATLAB software. The optimal volume fractions of solid electric conducting material and liquid electrolyte are obtained under different operation temperatures and bubble velocities.
Printing –Based Manufacturing of Flexible Ferroelectric Devices for Energy Harvesting Applications
Authors: Sundriyal Poonam , Bhattacharya Shantanu
Published: May 2020

Flexible ferroelectric devices have attracted enormous interest in recent years due to their excellent energy harvesting performance.[1, 2] Most of the existing ferroelectric devices have rigid nature and therefore are incompetent for flexible/ wearable electronic applications.[3] Here, we report a flexible ferroelectric device developed by printing the ferroelectric device components on flexible substrates. The 3- D structures of graphene oxide (GO) and poly(vinylidene fluoride- trifluroethylene) [PVDF- TFE] were printed with different designs and configurations to develop an optimum device. The thickness of the printing layers and size of the components were optimized to achieve better device performance. This device exhibits excellent energy harvesting performance with outstanding device flexibility. The better performance of the hybrid material may be due to the high mechanical strength, excellent Young’s modulus, and high dielectric constant of GO. This study suggests the new manufacturing methods and better device design for further development of piezoelectric energy harvesting devices.

References:

1. Chen, X., X. Han, and Q.D. Shen, PVDF‐Based Ferroelectric Polymers in Modern Flexible Electronics. Advanced Electronic Materials, 2017. 3(5): p. 1600460.

2. Bhavanasi, V., et al., Enhanced piezoelectric energy harvesting performance of flexible PVDF-TrFE bilayer films with graphene oxide. ACS applied materials & interfaces, 2015. 8(1): p. 521-529.

3. Dagdeviren, C., et al., Recent progress in flexible and stretchable piezoelectric devices for mechanical energy harvesting, sensing and actuation. Extreme mechanics letters, 2016. 9: p. 269-281.
(Invited) Reliability and Scaling Perspectives of HfO2-Based OxRAM
Authors: Cagli Carlo , Sandrini Jury , Sassine Gilbert , Robayo Diego , Hammad Ismail , Molas Gabriel , Gaillard Fred
Published: May 2020

Hafnium oxide OxRAM (Oxide Random Access Memory) is a non-volatile memory technology that has been widely investigated over the last 15 years. Its working mechanism relies on the formation and rupture of a tiny conductive filament through a HfO2 layer sandwiched between an active (Ti) and inert (TiN) electrodes. This causes the electrical resistance to very over three orders of magnitudes between a low resistance state (LRS) and a high resistance state (HRS).

OxRAM is a strong candidate to replace embedded Flash technology at scaled nodes. This is justified by several considerations but mainly driven by the low cost of integration and very high compatibility with standard CMOS technology. Yet OxRAM faces tremendous challenges in terms of reliability, variability and scaling.

In this paper we first show our latest findings in terms of reliability on a Ti/HfO2(5nm)/TiN cell. Controlling LRS and HRS resistance distributions can be achieved with a proper write/erase algorithm design (see Fig. 1) and it is a key point to enable large array integration. A proper write/erase sequence ensures long bit endurance up to 107 cycles. Data retention is then evaluated at four different temperatures (125, 165, 200 and 260 °C) to extract a 10 years retention temperature of 85°C.

Next, we discuss OxRAM scaling perspectives. In this context, it is essential to take into account both the resistive cell and its selector (most typically a MOS transistor). As recently shown [2], so far the OxRAM scaling has been mainly limited by the programming current, which determines the MOS selector size. Even if the OxRAM cell is integrated in the BEOL above its selector, the bitcell size is mostly determined by the underlying transistor. In addition, the OxRAM programming voltage dictates the transistor EOT and challenges the transistor reliability for scaled nodes. We demonstrated our OxRAM cell integration with a thin gate oxide FDSOI transistor (GO1/SG) and we show how this paves the OxRAM integration in a 28nm node.

Eventually we discuss the ultimate scaling perspective of an OxRAM array in a Cross-Point architecture. To enable such architecture the development of a BEOL selector is mandatory and we focused on Ovonic Threshold Switching device (OTS) for this scope. The OTS works switching between a low-conductive state and a metastable conductive one, which is voltage-triggered. We demonstrated (see Fig. 3) a 1S1R (one selector one resistor) OxRAM cell where the HfO2 memory is co-integrated with a series Ge-Sb-Se-N (GSSN) OTS. We eventually discuss the limits of this architecture showing that a trade-off exists between the half pitch of the Cross-Point array metal lines and the size of the memory bank.

REFERENCE

[1] G. Sassine et al., 2018 IEEE International Reliability Physics Symposium (IRPS).

[2] J. Sandrini et al., 2019 IEEE Electronic Device Meeting (IEDM).

[3] D. Alfaro Robayo et al., 2019 IEEE 11th International Memory Workshop (IMW).

Figure 1
Whether Ge-Rich ZrO2 and Ge-Rich HfO2 Materials Have Similar Reaction on Annealing Treatment?
Authors: Khomenkova Larysa , Lehninger David , Agocs Emil , Petrik Peter , Portier Xavier , Korsunska Nadiia , Melnichuk Oleksandr , Gourbilleau Fabrice , Heitmann Johannes
Published: May 2020

Usually, HfO2 and ZrO2 are considered as twin-oxides that have to demonstrate similar reaction on their doping with group IV elements as well as stable tetragonal “high-k” phase. However, in most cases the films produced with different approaches were compared. In this work, both Ge doped HfO2 and Ge-doped ZrO2 films were prepared using the same equipment that allows the same Ge content in both materials to be achieved via monitoring of deposition conditions. Thus, the effect of Ge content and thermal treatment on optical and structural properties of these films was studied to obtain direct experimental confirmation whether the formation of corresponding solid solutions and their phase separation stimulated by thermal treatment is similar for both oxides.

The films were grown on 6-inch Si wafers by confocal magnetron sputtering using the deposition unit with installed Ge, HfO2 and ZrO2 targets simultaneously. After the deposition, the wafers with the films were cut on smaller samples and rapid thermal annealing in nitrogen atmosphere was performed at 300-900ºC during 30 s. The samples were investigated by means of spectroscopic ellipsometry, Raman scattering, FTIR and TEM methods.

As-deposited pure ZrO2 and Ge-ZrO2 films as well as those annealed at TA≤600°C were found to be amorphous and homogeneous. Annealing at higher TA stimulates a phase separation and a formation of Ge nanoclusters (Ge-ncs). They crystallize at TC=640-700°C showing the tendency to the TC decrease with Ge content rise. An appearance of tetragonal ZrO2 phase in Ge-rich films was observed at TC=680-700°C. Such behavior of ZrO2 host shows the possibility to form Ge-ncs in amorphous matrix at TA=640-680°C that offers success application of such films.

Contrary to pure ZrO2 films, as-deposited pure HfO2 films were found to be crystalline. Their doping with [Ge]≥5at% reduces the degree of film crystallinity towards amorphous structure that was found to be stable for TA£600°C. At higher TA the formation of Ge-ncs and tetragonal HfO2 phase was detected. However, this latter was found to be formed at TC=600-670 °C, while the Ge-ncs crystallize at TC=700-800°C. Note that the formation of larger Ge-ncs in Ge-ZrO2 films than that in Ge-HfO2 ones at the same annealing conditions was observed.

Obtained results support the theoretical consideration about stability of tetragonal “high-k” phases in annealed films. However, they show also the difference in the reaction of Ge-HfO2 and Ge-ZrO2 materials on thermal treatment followed by phase separation. Its mechanism will be discussed in details.
The Effect of Carbon Coatings on the Electrochemical Performance of Composite Electrodes
Authors: Gonzalez Gabriel , Gonzalez Ramiro , Zuniga Luis , Chipara Mircea , Alcoutlabi Mataz
Published: May 2020

This work focuses on the effects of sample preparation and particle size on the dielectric properties of polymer nanocomposites. A comparison between the dielectric permittivity and dielectric loss of Polymethyl methacrylate (PMMA) samples, prepared by solution casting and compression molding, has been achieved. A Time Domain Spectrometer and an Agilant (HP) 4284A LCR precision meter, were furbished and used to measure the dielectric properties of insulating nanocomposite materials. The cast samples have shown different dielectric responses from the melt-pressed samples. These differences diminish with lengthening the dry time of the cast samples under vacuum. In addition, nanocomposite and microcomposite samples were prepared by solution casting of PMMA solution and Titanium dioxide (TiO2) particles. The dielectric properties of the nanocomposites were different from the polymer samples where a decrease in the dielectric permittivity of the nanocomposite has been observed. These differences in the dielectric response of the PMMA sample and the nano/micro composite samples might be due to many issues such as, sample preparation or the aggregation of the TiO2 nanoparticles in the polymer matrix. Furthermore, polymer-blends samples of PEO and PMMA have been prepared by solution casting method. The results reported in this work show similar trend compared to those reported in the literature.