Electrochemical Impedance Tests Research Articles

Combined PEO and Spray Pyrolysis Coatings of Phosphate and ZnO for Enhancing Corrosion Resistance in AZ31 Mg Alloy

Oxide films produced from plasma electrolytic oxidation are porous in structure. While they have some passivating effect in Mg alloys, the pores still lead to corrosion over long periods of exposure. In this study, spray pyrolysis was used to seal the porous oxide layer developed through the plasma electrolytic oxidation method on Mg alloy AZ31. The PEO coating acted as a good base for the application of spray pyrolysis due to its morphology. Three different kinds of coatings were obtained using different precursors: zinc acetate for ZnO, phosphoric acid for phosphate (P), and a mixture of zinc acetate and sodium phosphate for ZnO+P. The corrosion performance of all three coatings was studied by performing electrochemical impedance and polarization tests on the samples. Mass loss over a duration of 1 week was measured in 3% NaCl solution using immersion gravimetry. The coating with only phosphate (P) was found to be most corrosion-resistant with 52 times lower rate of corrosion and 50 times more polarization potential. The chemical composition of the corrosion products was studied using XRD and SEM-EDS analysis. Mass loss in ZnO+P was the highest, at up to 1.4 and 5.1 times higher than ZnO and P, respectively.

Nano-Functionalization of SOFC Electrodes Via Inkjet Printing

Introduction The future of the international accord on mitigating the impact of climate change is linked to the successful commercialisation and implementation of renewable energy technologies. The latter is strongly dependent on finding commercially viable methods for successful dimensional nano-functionalization of the ceramic materials utilized in the fabrication of various energy devices either in energy generation (fuel cells) or storage (batteries, supercapacitors). Inkjet printing digital methods combining scalability and low equipment cost with high-resolution patterning can be a feasible solution for some of the shortcommings of the conventional fabrication technologies. 3D functionalization - Composite solid oxide fuel cells LSCF/CGO cathodes were nano-engineered via “dual” inkjet printing infiltration. The nano-decorated microstructure was found to extend the active three-phase boundary and to promote adsorbtion – dissociation - surface exchange reactions. Composite La0.6Sr0.4Co0.2Fe0.8O3-δ/Ce0.9Gd0.1O1.9 cathodes were subjected to “dual” inkjet printing infiltration of nitrate salt solutions in a single step procedure. After calcination in air at 700 oC the cathodes were decorated with Ce0.9Gd0.1O1.9 and CoxOy nano particles. The effects of as created nano-decoration on the electrochemical activity and the performance stabilty in the intermediate temperature range (500-700 oC) were investigated. The infiltration was found to extend the active three-phase boundary and to promote adsorbtion-dissociation- surface exchange reactions. Electrochemical impedance tests conducted on symmetrical cells showed a reduction in the polarisation resistance of between 1.5 and 7.0 times depending on temperature (500-700 oC). The nano-decoration led to substantially enhanced stability (0.7 Ω•cm2 at 550oC after 100 hours of aging for CGO:CoxOy infiltration). As the composite LSCF/CGO cathodes had already percolating ionic and electronic networks, a low level loading of nanoparticles was sufficient to lead to an efficient short-range extension of the TPB and the density of ORR reaction sites. The sequence of infiltration was shown to influence the efficiency of the ORR promotion. CoxOy:CGO infiltration expanded the available surface area and promoted the catalytical activity towards ORR reaction. The superior effect of CGO:CoxOy infiltration was assigned to the introduction of additional promotion mechanisms (see Fig. 1) resulting in better electrochemical performance at lower temperatures (<650 oC). Both infiltrations suppressed the Sr surface segregation but only CGO:CoxOy infiltrated cathodes showed substantially improved stability after 100 hours of aging. Scaling up - Single step inkjet printing infiltration with doped ceria Ce0.9Ye0.1O1.95 (YDC) and cobalt oxide (CoxOy) precursor inks was performed in order scale-up the modification of the doped ceria interlayer in commercial (50x50x1 mm size) anode supported SOFCs. The penetration of the inks through the mono-phase La0.8Sr0.2Co0.5Fe0.5O3-δ porous cathode to the Gd0.1Ce0.9O2 interlayer was achieved by optimization of inks rheology jetting parameters. The low temperature calcination resulted in densification of the Gd-doped ceria porous interlayer as well as decoration of the cathode scaffold with nano-particles (~ 20-50 nm in size). The I-V testing in pure hydrogen showed maximum power density gain of 20% at 700oC and 97% at 800oC for the infiltrated cells (see Fig. 1). The effect was largely assigned to the improvement in the interfacial Ohmic resistance. The EIS study of the polarization losses of the reference and the infiltrated cells revealed reduction in the activation and concentration polarizations losses at 700oC due to the nano-decoration of the La0.8Sr0.2Co0.5Fe0.5O3-δ scaffold surface. Such effect was not clearly detectable at 800oC where the drop of Ohmic losses was dominant. This work demonstrated that single-step inkjet printing infiltration, a non-disruptive low-cost technique, could produce significant and scalable performance enhancements in commercial SOFCs. Figure 1

Corrosion inhibition effect of mebendazole on 5Cr pipeline steel in 1 M HCl solution

In this manuscript, the ability of (5-Benzoyl-1H-benzimidazol-2-yl) carbamicacidmethylester (mebendazole, MBD) as an inhibitor of corrosion on 5Cr pipeline steel in HCl medium was explored. Corresponding electrochemical tests, immersion tests and other experiments were designed, and at the same time, the ability of mebendazole to inhibit corrosion of 5Cr steel in HCl medium was screened and proved by means of molecular weight simulation calculation analysis process, and its possible anticorrosion mechanism was also revealed. Electrochemical test results show that mebendazole can successfully prevent 5Cr steel from dissolving in HCl medium, and the inhibition efficiency is particularly significant with the increase of mebendazole content. According to the electrochemical impedance test, the highest corrosion inhibition efficiency (η) can reach 94.4 %. The results of immersion weight loss experiment are highly consistent with the electrochemical test data and SEM electron microscope morphology. From the theoretical calculation results, it can be found that under neutral conditions and protonated mebendazole molecules have lower energy gaps and higher dipole moments in solvated and unsolvated environments, and can Parallel adsorption on the metal surface, which also corresponds to its efficient corrosion inhibition performance. In addition, through comparison, it is found that the protonated mebendazole molecule under solvation conditions has the highest binding energy, that is, it is the easiest to interact with 5Cr steel and presents the best anti-corrosion performance.

A novel Z-type heterojunction Bi3O4Cl/Bi4O5I2 photocatalytic composite with broad-spectrum antibacterial activity and degradation properties

At present, the sustainable development of humans is facing health problems and ecological imbalance caused by environmental pollution. To solve the bacteria, antibiotics and other pollutants in wastewater, Bi3O4Cl and Bi4O5I2 with appropriate bandgap width were selected to prepare Z-type heterojunction Bi3O4Cl/Bi4O5I2 photocatalytic materials by calcination method. Under LED light, the best sample Bi3O4Cl/Bi4O5I2-4 could completely inactivate Escherichia coli (E. coli) and Staphylococcus aureus (S. aureus) in 30 min, Bacillus subtilis (B. subtilis) and Pseudomonas aeruginosa (P. aeruginosa) in 20 min, and degrade 70.6% of tetracycline (TC) and 97.4% of Rhodamine B (RhB). Photocurrent and electrochemical impedance tests (EIS) confirmed the high photocurrent response and low charge transfer resistance in the Bi3O4Cl/Bi4O5I2. The photocatalytic antibacterial and degradation mechanism of Z-type Bi3O4Cl/Bi4O5I2 heterojunction was verified by capture experiments. Thus, this study provides a compact and efficient photocatalyst with broad-spectrum antibacterial activity and degradation properties.

Mixed simultaneous barrier and passivation mechanisms by Cloisite 30B and cerium conversion coating to reinforce the epoxy coating’s adhesion and anti-corrosion properties

Increasing the corrosion resistance and adhesion of the organic coatings is always a desire in industrial properties. Thus, in this research, the corrosion resistance properties of epoxy/nanoclay nanocomposites were investigated for their application in organic coatings on metal surfaces. The results demonstrated that the sample containing 1.5 wt% of nanoclay exhibited the highest impedance modulus (1.22 ×108 ohm.cm2) after 4 weeks of immersion in a 3.5 wt% NaCl electrolyte environment. Subsequently, a cerium conversion coating was applied to the surface of st-37 steel under optimal conditions. Electrochemical tests revealed that the corrosion resistance of the surface improved with the application of the cerium conversion coating, resulting in an increase in charge transfer resistance from 1041 to 1742 ohm.cm2. Moreover, the polarization test showed a decrease in current density from 24.9 to 5.4 μA/cm2. Pull-off, salt spray, and electrochemical impedance tests demonstrated that the cerium conversion coating enhanced the adhesion and corrosion resistance of the organic coating system. The epoxy/nanoclay nanocomposite, in its optimal state, was applied to the steel surface modified by the cerium-based conversion coating, confirming the improvement of the optimal coating system. Quantitative results indicated that after 7 weeks of immersion in a corrosive electrolyte, the impedance modulus of the epoxy coating containing 1.5 wt% nanoclay combined with the cerium conversion coating was equal to 1.51 × 1010 ohm.cm2.

Corrosion inhibition performance of Punica granatum L extract on Q235 steel in H2SO4 environment: Electrochemical, morphological, and quantum chemical studies

The corrosion inhibitor used in this experiment was the extract of Punica granatum L (PGLE), which was obtained using the pure water extraction method. The inhibition performance of PGLE on Q235 steel in H2SO4 environmental was investigated using electrochemical methods, morphology studies and quantum chemical calculation. The corrosion inhibition properties of PGLE were found to be excellent, with a corrosion inhibition efficiency of approximately 95% at 200 mg/L, and it exhibits characteristics of a mixed-type corrosion inhibitor. The electrochemical impedance (EIS) test revealed a remarkable increase in the charge transfer resistance with the increment of PGLE concentration, and the surface of Q235 steel was covered by a tight and well-organized protective layer of PGLE. The surface morphology test indicates a noticeable decrease in the average surface roughness upon the adsorption of PGLE extract onto the Q235 steel. According to the adsorption isotherm analysis, the adsorption behavior of PGLE on Q235 steel conformed to the Langmuir adsorption. Additionally, adsorption might be physical or chemical. Quantum chemical calculations also showed that PGLE has excellent corrosion inhibition properties.

Corrosion behavior and tribological-microstructural characterization of Al/ZrO2-Gr hybrid composite fabricated via Friction Stir Processing

The present study investigates the microstructural evolution, tribological properties, and corrosion behavior of hybrid metal matrix composites reinforced by a combination of graphite (Gr) and zirconia (ZrO2) particles fabricated by Friction Stir Processing (FSP). To do so, microstructural characterization was carried out by optical microscopy (OM) and electron backscatter diffraction (EBSD) analysis. In addition, pin-on-disk, microhardness measurement, potentiodynamic polarization, and electrochemical impedance tests were conducted to evaluate the tribological and corrosion behavior of the samples. Results showed that employing four passes of FSP led to significant grain refinement in stir zones because of dynamic recrystallization (DRX), particle-stimulated nucleation (PSN), and Zener pinning effect. Furthermore, the EBSD results illustrated that the average grain size area has significantly decreased from ∼115 µm2 in the only FSP-treated specimen to ∼1.2 µm2 in the hybrid composite. Also, the presence of the secondary phase particles caused an increase in the fraction of the high-angle grain boundaries (HAGBs) compared to the only FSP-treated specimen. The results of the pin-on-disk test revealed that the wear resistance improved in the particle-reinforced composites and, on the other hand, decreased in the FSP-treated sample compared to the base metal (BM). Furthermore, the lubricant effect of the Gr particles contributed to a pronounced reduction in the coefficient of friction (COF) and weight loss in the Gr-containing composites such that the COF of the hybrid composite and Gr-reinforced mono-composite dramatically decreased by ∼0.52 and ∼0.37, respectively. The corrosion behavior of the FSP-treated sample demonstrated better resistance compared to the BM. In addition, the particle-reinforced composites exhibited better corrosion resistance than the FSP-treated sample and BM, especially the Al/Gr mono-composite which had the minimum corrosion rate and the most positive pitting potential (Epit), making it the most pitting-resistant sample in comparison to other specimens.

NanoCeO2/conducting polymer based composite electrodes for high performance supercapacitor

Abstract The present research paper reports the structural, morphological and electrochemical properties of cerium oxide doped polythiophene nanocomposite. Polythiophene was first polymerized using the chemical oxidation polymerization method and further, it was mixed with an equal amount of cerium oxide (CeO2) nanoparticles by mechanical mixing. The initially generated polythiophene sample exhibited an amorphous character according to X-ray diffraction investigation, however the PTh–nCeO2 polymer nanocomposite displayed good crystallinity. The vibration bands of the PTh and PTh–nCeO2 polymer nanocomposites were further examined using Fourier-transform infrared spectroscopic studies. The morphology and elemental composition of the prepared samples were investigated using scanning electron microscope and energy dispersive X-ray analysis. The electrochemical performance of PTh and PTh–nCeO2 polymer nanocomposite was studied by cyclic voltammetry, Galvanostatic charge–discharge and electrochemical impedance spectroscopy measurements. The PTh–nCeO2 polymer nanocomposites demonstrated a high specific capacitance of 161 F g−1 at a current density of 1 A g−1 among the produced samples. The Nyquist plot (low-frequency area) and Bode plot (phase angle) electrochemical impedance tests revealed excellent capacitive performance. The PTh–nCeO2 polymer nanocomposites may be a good option for high-performance super capacitors, according to the findings.

The effects of cinnamon, ginger and sesame oils on in-situ solvothermal reduction of multi-layered graphene oxide in epoxy to improve hydrophobicity and corrosion resistance

An effective and green method including in-situ solvothermal reduction of multi-layered graphene oxide (MLGO) using a mixture of acetonitrile and sesame, ginger and cinnamon oils, was investigated for preparing a hydrophobic and corrosion-resistant epoxy coating. The efficiencies of the oils as green reducing agents with synergistic effect by acetonitrile in the solvothermal reduction of MLGO at a temperature of 70 °C were compared with each other. FT-IR, TGA, Raman, and Mapping-EDAX analysis showed that the solvothermal reduction process of MLGO in acetonitrile/cinnamon oil mixture was successfully performed. The results of long-term salt spray and electrochemical impedance tests showed that epoxy-RMLGO (acetonitrile/cinnamon oil) nano-coating had a significant improvement in corrosion resistance (after10 months, the impedance value was 8.1 × 108 Ω cm2) compared with the other coatings. Also, the value of the water contact angle for the nano-coating was 102.80° and based on Mapping-EDAX analysis, the C/O ratio was 54.45.

Effect of Process Parameters on Electrodeposition Process of Co-Mo Alloy Coatings

Plating bath composition, temperature, current density, and pH have a great influence on the properties of a Co-Mo alloy coating. However, these conclusions are obtained from the perspective of test results. Most of the factors that affect the properties of the coating operate by interfering with the electrodeposition process. Therefore, it is of great significance to study the kinetics of the electrodeposition process. To further study the influence of process parameters on the deposition process of Co-Mo alloy coatings, cyclic voltammetry (CV), scanning linear voltammetry (LSV), and electrochemical impedance testing (EIS) were used to study the deposition kinetics of Co-Mo alloy coatings. The results show that with the increase in sodium molybdate content in the plating solution, more Mo elements are involved in the deposition process. At the same time, a higher Mo element content can reduce the dissolution of the coating as the anode and improve the service life of the coating, but too high a Mo element content will lead to cracks on the surface of the coating. The deposition temperature will affect the processes of reduction deposition and oxidation dissolution of the coating. The pH of the plating bath will directly affect the reduction reaction process of MoO42− ions in the plating bath. With the increase in the pH value, the reduction reaction rate of MoO42− ions decreases, and the cathodic reduction reaction current density decreases. At the same time, the peak current density of anodizing decreases with the decrease in the pH value of the plating solution, indicating that the alkaline plating solution has an inhibitory effect on the plating dissolution process.

Effect of Lateral Laser-Cladding Process on the Corrosion Performance of Inconel 625

This study aimed to evaluate the corrosion properties of different samples coated by the laser-cladding method to find the optimal laser parameters. Thereby, potentiodynamic polarization (Tafel) and electrochemical impedance tests were performed to assess the corrosion resistance of coated samples. Consequently, the corrosion morphology of tested samples was inspected by scanning electron microscopy. The results demonstrated that the laser power directly correlates with pitting corrosion and defects on the surface of the samples. Moreover, when molybdenum and chromium ions are increased in the electrolyte solution, the passive and protective layers are more durable, as the ions are sited within the holes and defects, reducing the surface corrosion rate.

A new insight on the mechanisms of corrosion deactivation of a typical Ti/IrO2 + RuO2 +TiO2 coating in the presence of Ta2O5 in chlor-alkali medium

Mixed metal oxide (MMO) anodes are commonly used in chlor-alkaline industry. They have a longer lifetime than conventional graphite anodes due to the presence of valuable and expensive metal oxides such as iridium and ruthenium. However, they can suffer from pitting corrosion. This makes them to lose their stability, which necessitates the application of stabilizers to delay this process as one of the most accepted preventive measures. Hence, this study to aims to increase the life of MMO anodes, by altering corrosion mechanisms from localized to uniform corrosion. To achieve this objective, electrodes of different nominal compositions were prepared by adding 2 and 5 wt% of tantalum oxide into the base coating composition (Ti/(38IrO2-36RuO2-(26-X)TiO2-XTa2O5)). Accelerated lifetime and electrochemical impedance tests were employed in order to evaluate the corrosion pathways at different time intervals. Furthermore, morphological properties and composition of the anode were addressed via scanning electron microscopy (SEM), energy dispersive spectroscopy (EDS), and X-ray diffraction (XRD) analysis. In addition, cyclic voltammetry test was performed to investigate electrochemical properties. It was understood that the addition of tantalum oxide leads to increment in active surface area and current density of the anode reaction. More importantly, tantalum oxide was found to be an effective inhibitor of the pitting corrosion while altering the dominant corrosion pathway from pitting to uniform dissolution in ternary coatings. However, it resulted in the service life of the anode to be reduced in the accelerated life test.

Effect of Cr and La co-doping on the photocatalytic hydrogen production performance of Sr1-xLaxTi1-xCrxO3 nanofibers

The Sr1-xLaxTi1-xCrxO3 (x = 0–0.05) nanofibers were synthesized by electrospinning based on Pechini sol-gel method. The prepared Sr1-xLaxTi1-xCrxO3 nanofibers were analyzed by XRD, Raman, UV–vis spectra, XPS, SEM, TEM, transient photocurrent, electrochemical impedance and photocatalytic hydrogen evolution tests. The results showed that CrLa co-doped can expand the light absorption region of SrTiO3 from the ultraviolet region to the visible light, and significantly narrowed its band gap. Under visible light irradiation, Sr1-xLaxTi1-xCrxO3 nanofibers exhibited the best hydrogen evolution activity at x = 0.03, and the hydrogen evolution rate reached 106.2 μmol∙g−1∙h−1. This may be the result of the combined effect of the intermediate band gap and the band gap variation due to Cr doping.

Room Temperature Columnar Liquid Crystalline Perylene Bisimide as a Novel Corrosion Resistant Surface Film for Mild Steel Surface

The corrosion process can be seen as a widespread phenomenon, which is both pervasive and unstoppable. This is an undesirable phenomenon that reduces the life of materials and takes away their beauty. Potentiodynamic and electrochemical impedance tests are used to explore the corrosion inhibition abilities of a room temperature columnar liquid crystalline perylene bisimide (PBIO10) on mild steel (MS) samples in 1 M HCl. The inhibitor PBIO10 was demonstrated to be an outstanding corrosion inhibitor, with a maximum inhibition efficiency of 76%. In light of potentiometric polarization results, corrosion inhibition was achieved as the inhibitor getting adsorbed on the metal, and they fit into the category of anodic inhibitors. The protective layer was examined from SEM to confirm the protective coating generated on the MS surface. The increase in contact angle confirms the formation of a uniform layer on the MS surface. Analysis of the optical textures observed in POM, the nature of the mesophase under examination to columnar rectangular (Colr) phase. From the TGA, it was found that PBIO10 exhibits higher thermal stability u to 370 ℃. The density functional theory (DFT) and Monte Carlo simulation approach were used to investigate the relationship between molecular structure and inhibitory efficacy. The thermal behavior of PBIO10 was investigated by polarizing optical microscopy (POM), differential scanning calorimetry (DSC), thermogravimetric analysis (TGA), and X-ray diffraction (XRD) studies. The phase transition from crystal to LC phase was at first examined with the help of POM observation.Graphical

Charge transfer resistance of nitro substituted dibenzalacetone on mild steel against acid attack

Corrosion of metals is a serious industrial problem due to its impact on economic losses and irresistible structural damage. In this work, dibenzalacetone derivatives 1, 5-bis (2-nitrophenyl)-1, 4- pentadien -3-one (BPDO) are employed as controlling agents on mild steel in 1 M H2SO4. The effect of BPDO on reducing corrosion of mild steel was analyzed using electrochemical and non-electrochemical methods. From experimental results, it is proved that the protection efficiency increases with enhance in BPDO concentration and diminishes with enlarge in temperature. BPDO is an effective corrosion inhibitor with a 98.64% inhibition efficiency at only 300 ppm concentration. IE diminishes as exposure time increases due to a decrease in the stability of the adsorbed BPDO on the metal surface. The results of Tafel polarization measurements revealed that BPDO acts as a mixed type inhibitor. In both the polarization and Electrochemical Impedance tests, 308K and 300 ppm of BPDO were used, yielding maximal inhibition efficiencies of 98.41% and 97.57% respectively. Langmuir adsorption isotherm is found to be the most suitable way to explain the adsorption of BPDO on the surface of mild steel. Physisorption is proposed from the values of ΔGads. Formation of a protective layer on mild steel surface was affirmed by various spectroscopic studies.

Preparation of Rare Earth Metal Electrode Material by In-situ Polymerization for Supercapacitor Application

This is a comparative study of supercapacitor performance of CeO2/PANI composite electrode prepared by two different synthesis methods, namely, in situ polymerization and solution mixing. The chemical composition of materials was confirmed by X-ray diffraction (XRD). The electrochemical studies such as cyclic voltammetry (CV), charge–discharge, electrochemical impedance and cyclic test of the composite were studied in two symmetrical electrode systems in an aqueous electrolyte medium. The CeO2/PANI (CP10) composite prepared by in situ polymerization has resulted in better specific capacitance than solution mixing in an aqueous electrolyte (0.5[Formula: see text]M H2SO4) with the capacitance value of 240[Formula: see text]F/g at 0.5[Formula: see text]A/g. The in-situ polymerization method evenly spreads polyaniline (PANI) all over the cerium oxide (CeO2) material and reduces charge transfer resistance ([Formula: see text]) which is lacking in the solution mixing method. After 4000 cycles at 5[Formula: see text]A/g, the CP10 composite retained 72.8% of capacitance retention and energy density of 33.33[Formula: see text]Wh/Kg at power density of 249.87[Formula: see text]W/Kg.

Enhanced high-rate cycling performance of LiMn2O4 cathode materials by coating nano-TiO2

Abstract LiMn2O4 has the advantages of low cost and no pollution, and is widely regarded as a large-scale lithium battery cathode material. However, the capacity decays rapidly, which seriously affects the application of LiMn2O4 cathode materials. Therefore, improving the cycling performance of LiMn2O4 is the focus of current research. LiMn2O4 precursors were prepared by chemical precipitation and the precursors were coated to prepare LiMn2O4/TiO2 composites. X-ray diffraction and scanning electron microscopy showed that LiMn2O4 had been successfully combined with TiO2. Electrode charge–discharge and electrochemical impedance tests showed that LiMn2O4/TiO2 had the best cycle performance at high rates. The initial discharge capacities of LiMn2O4/TiO2 reached 106.4 mAh·g−1 at 0.2 C. After 100 cycles, the 2 C capacity retention rates was 76.3 %, compared to only 66.5 % for pristine LiMn2O4. The improved electrochemical performance was attributed to the nanoscale oxides hindering the reaction between the electrolyte and the electrode, which effectively improved the stability of the material during high current charge and discharge.

Effect of reduced graphene oxide addition on cathode functional layer performance in solid oxide fuel cells

Solid oxide fuel cells (SOFCs) operating at high temperatures are highly efficient electrochemical devices since they convert the chemical energy of a fuel directly into heat and electrical energy. The electrochemical performance of an SOFC is significantly influenced by the materials and microstructure of the electrodes since the electrochemical reactions in SOFCs take place at three/triple phase boundaries (TPBs) within the electrodes. In this study, graphene in the form of reduced graphene oxide (rGO) is added to cathode functional layer (CFL) to improve the cell performance by utilizing the high electrical properties of graphene. Various cells are prepared by varying the rGO content in CFL slurry (1–5 wt %), the number of screen printing (1–3) and the cathode sintering temperature (900–1100 °C). The electrochemical behavior of the cells is evaluated by electrochemical performance and impedance tests. It is observed that there is a ∼26% increase in the peak performance of the cell coated with single layer CFL having 1 wt % graphene and 1050 °C sintering temperature, compared to that of the reference cell.

Accumulative extrusion bonding of Mg-Mn-Ca/FA+GNP hybrid biocomposite: On microstructure evaluation, mechanical and corrosion properties

Mg alloys have limitations for biomedical applications due to high corrosion rate and low strength. In this study, magnesium alloy (Mg-0.5Ca-0.8Mn (wt.%)) and it's composite reinforced to fluorapatite (FA) and graphene nanoplate (GNP) were produced through several stages including pre-dispersion, mechanical stirring, re-melting under Ar atmosphere, and accumulative extrusion bonding at 120º channels (AEB process). Mechanical properties such as tensile strength and corrosion behavior were investigated by electrochemical impedance tests and hydrogen release in simulated body fluid (SBF). Microstructural variations such as reinforcement dispersion and grain size were assessed by optical microscopy and scanning electron microscopy (FESEM). The results indicated an improvement in dispersion and uniform distribution of the reinforcement particles as well as a homogenous microstructure with increasing the AEB passes. With adding reinforcements and after 3-pass of AEB process, the average grain size of the base alloy and its composite decreased from 450 and 175 µm to 1.55 µm and 851 nm, respectively. So, the yield and ultimate strengths of the composite increased from 63 and 172 MPa to 270 and 386 MPa compared to the base alloy, as contribution of adding reinforcements in strengths increase was almost 26% and 14%, respectively. The corrosion resistance of the homogenized alloy was improved from 1.1 to 4.02 KΩ.Cm 2 with addition of reinforcements and a considerable increase to 18.55 KΩ.Cm 2 was obtained with a special improvement in corrosion rate (0.057 mm/year) after 3-pass of AEB process.

Silver nanoparticles-glycine-functionalized graphene platform for ultra-sensitive determination of bergenin

Herein, an efficient method for in-situ assembly of silver (Ag) nanoparticles on glycine functionalized graphene (Gly-Gr) has been proposed, which only requires a simple one-step hydrothermal reaction. The microstructure of the material (Ag-Gly-Gr) was characterized by a series of methods, such as FT-IR, XRD, and TEM. For comparison, glycine functionalized graphene (Gly-Gr) was prepared by the same way without adding silver nitrate. The electrochemical sensor (Ag-Gly-Gr/GCE or Gly-Gr/GCE) was prepared by coating the glassy carbon electrode (GCE) surface with dispersive droplets of the related material. The outcomes of the electrochemical impedance test showed that the charge transfer resistance of Ag-Gly-Gr/GCE was less than that of Gly-Gr/GCE and GCE. Compared with the other two sensors, Ag-Gly-Gr/GCE showed a more sensitive response for bergenin. By studying the influence of the pH and sweep rate on the peak potential, the dynamics parameters were discussed to understand the electrochemical reaction mechanism of bergenin. The strategy for quantitative analysis of bergenin was further established at the working potential of 0.8 V (vs SCE). The peak current of bergenin displayed a linear dependence for concentration in 0.01–1 μM with a detection limit of 3.0 nM. Additionally, the analytical availability of Ag-Gly-Gr/GCE was demonstrated by determining bergenin in real-life samples.