Acetic Acid Solution Research Articles

Integrated acetic acid and deep eutectic solvent pretreatment on poplar for co-production of xylo-oligosaccharides, fermentable sugars and lignin antioxidants/adsorbents

Efficient fractionation of lignocellulosic biomass in usable forms of hemicellulose, cellulose and lignin is very important for the sustainable lignocellulosic biorefinery. Herein, poplar sawdust was pretreated with an integrated process composed of acetic acid pre-hydrolysis (170 °C, 60 min) for xylo-oligosaccharides (XOS) production and mild deep eutectic solvent (90–130 °C, 60 min) post-delignification for recovering lignin fractions, resulting in easily hydrolyzed cellulose fraction. Results showed that, after integrated pretreatment and enzymatic hydrolysis, 51 % of xylan and 92 % of glucan in raw biomass could be converted to XOS (DP 2–6) and glucose, respectively, while 71 % of the original lignin could be recovered in DES solvent. The resulting XOS were proven to ensure the growth of probiotics, Bifidobacterium adolescentis. Besides, the lignin macromolecules recovered from DES solvent showed high-purity (around 95 %), low-molecular weight (Mw around 2000), small particle size (270–170 nm) and high-PhOH (3.08 mmol/g) content, which were likely relevant to the excellent antioxidant activity (RSI = 15.16) and adsorbent activity (Pb(II) 461.89 mg/g lignin). Finally, mass balance and energy analysis revealed that the integrated pretreatment could be used as a promising approach for the production of bio-based chemicals and materials from woody biomass.

Making Gelatin From Milkfish Bones (Chanos Chanos) and it Application in Soy Milk Pudding (Glycine Max)

Indonesia's dependence on imported gelatin is increasing. Based on the literature that as much 80% of imported gelatin uses non-halal raw materials in the form of pig skin, it is necessary to make innovations to produce gelatin from halal materials. The purpose of this study was to analyze the characteristics of gelatin from milkfish bones and produce soy milk pudding with characteristics that are acceptable to panelists. The research method consisted of making two types of gelatin using 3% acetic acid solution and 4% hydrochloric acid solution, then conducting physical analysis for gelatin and organoleptic, protein, and syneresis tests for soy milk pudding. The results showed that milkfish bone gelatin using 3% acetic acid solution had a gel strength of 181.5 g/bloom, a yield of 2.2%, and a pH of 7. Meanwhile, milkfish bone gelatin using 4% hydrochloric acid solution had a gel strength of 57.5 g/bloom, a yield of 13.97%, and a pH of 6. Then, the best results were obtained in soy milk pudding with the addition of milkfish bone gelatin in 3% acetic acid solution. In addition, milkfish bone gelatin using 3% acetic acid solution has almost the same structure as commercial gelatin based on FTIR results.

Microbiological activity of thiamphenicol and thiamphenicol glycinate acetylcysteinate against clinically significant microorganisms and their biofilms

Objective. To determine the minimum inhibitory concentrations of thiamphenicol and thiamphenicol glycinate acetylcysteinate against clinically significant microorganisms and determine their efficacy against microbial biofilms. Materials and Methods. This study included 48 clinical strains isolated from the sputum of patients with respiratory tract infections (16 S. pneumoniae, K. pneumoniae and S. aureus strains). Antimicrobial susceptibility testing was performed using broth microdilution method. Biofilm formation culturing with antibiotics, N-acetylcysteine and their combinations was assessed in Mueller-Hinton broth and brain heart broth in 96-well plates. Biofilms are fixed with 2,5% glutaraldehyde solution, stained with 0,25% crystal violet solution, which is extracted by 33% acetic acid solution. Results. The MIC of thiamphenicol and thiamphenicol glycinate acetylcysteinate (in terms of thiamphenicol) were the same for 87,5% of strains. Thiamphenicol and thiamphenicol glycinate acetylcysteinate have been confirmed high antimicrobial activity against S. pneumoniae strains (MIC50 0,5 mg/l, MIC90 1-2 mg/l). Cultivation with chloramphenicol, thiamphenicol, thiamphenicol glycinate acetylcysteinate, combination of chloramphenicol and thiamphenicol with N-acetylcysteine contributed to significant reduction in the optical density of S. pneumoniae biofilms. Thiamphenicol increased biofilm formation in some resistant S. aureus and K. pneumoniae. Combination based on N-acetylcysteine neutralized this effect. Conclusions. Potentiation of antibacterial activity of thiamphenicol by N-acetylcysteine against S. pneumoniae biofilms has been shown.

The healing effects of moderate exercise on acetic acid-induced gastric ulcer in male rats.

This study aimed to evaluate the effect of moderate exercise on the healing of acetic acid-induced gastric ulcers in male rats. Gastric ulcers include benign mucosal and submucosal lesions of the gastric wall. Exercise regulates a wide range of physiological processes. 48 male Wistar rats were randomly divided into three experimental groups (n=16 per group) as follows: control, which was left untreated after causing stomach ulcers; experimental group 1, the rats were first exercised and then received acetic acid; experimental group 2, the rats received acetic acid, and then exercised. The ulcer was caused by injecting 0.12 ml of a 60% acetic acid solution after 24 hours of not eating. The rats had a period of moderate treadmill activity either before or after the development of ulcers, lasting for a duration of 30 days. On the seventh and fourteenth days after the experiment, the rats were sacrificed, their stomach was removed, and the wound healing parameters, and wound depth were determined. Exercise before and after inducing gastric ulcers significantly decreased the depth of gastric ulcers in the experimental groups. The average number of PMN in the control group decreased in comparison to the seventh and fourteenth days following the experiment. Conversely, the number of fibroblasts, epithelialization, and new vessels increased. It seems that exercise before the appearance of ulcers has a greater effect on gastric ulcers compared to exercise after inducing gastric ulcers. Exercise can prepare the gastric mucosa for forthcoming injuries, and heal gastric ulcers. Moderate aerobic exercise has significant restorative effects on gastric ulcers caused by acetic acid and is recommended.

Determination of perchlorate and chlorate in drinks by ultra-performance liquid chromatography-tandem mass spectrometry

To establish a method for determination of perchlorate and chlorate in drinks by ultra-performance liquid chromatography-tandem mass spectrometry(UPLC-MS/MS) based on isotopic internal standard method. The perchlorate and chlorate residue in liquid drinks were extracted with methanol, in solid drinks with acetic acid solution, then centrifuged. The supernatant was cleaned-up with PSA/C18 cleanup tube. The separation of perchlorate and chlorate was carried out on a Acquity CSH fluorophenyl column(100 mm×2.1mm, 1.7 μm) and the detection was performed with tandem mass spectrometry with internal standard method for quantification. The peak area ratio of perchlorate and chlorate had a good linear relationship with their mass concentration within their respective linear ranges, with correlation coefficients(r) greater than 0.999. The limits of detection of perchlorate and chlorate were 0.2and 1 μg/L respectively and the limits of quantification were 0.5 and 3 μg/L respectively. The mean recoveries of two compounds were from 84.0% to 105.5% with relative standard deviations from 4.2% to 17.0% and 82.7% to 112.1% with relative standard deviations from 5.5% to 18.4%(n=6), respectively. The perchlorates in 11 kinds of beverage samples were 0.53-4.12 μg/L, chlorates were 3.27-61.86 μg/L. This method is simple, sensitive, accurate and reliable, which is suitable for the determination of perchlorate and chlorate in drinks.

The determination of underivatized chlormequat, fosetyl-aluminium and phosphonic acid residues in maize and soybean by LC-MS/MS.

In this study, a simple, rapid and sensitive method was developed for the simultaneous determination of chlormequat, fosetyl-aluminium and phosphonic acid residues in maize and soybean using liquid chromatography-triple quadrupole mass spectrometry (LC-MS/MS). Analytes were extracted with acetic acid solution, purified on an HLB column, and then filtered through a 0.2 μm hydrophilic microporous filter membrane. They were then separated on an IC column using a separation phase consisting of polyvinyl alcohol particles with quaternary ammonium groups. The mobile phase optimised with water was denoted as mobile phase A and that optimised with 200 mmol L-1 ammonium bicarbonate solution containing 0.05% ammonium hydroxide was denoted as mobile phase B. The residues were detected by tandem mass spectrometry with negative electrospray ionization in a multi-reaction monitoring mode. The correlation coefficient (R ≥ 0.997) showed good linear regressions for all analytes in water as well as in maize and soybean matrices with a wide dynamic range of 0.001 to 0.5 mg L-1 for calibration. The mean recoveries (RSDs) of the analytes were in the range 85.0-106.4% (5.5-14.9%), 81.7-109.5% (2.7-11.0%) and 74.7-104.4% (2.9-6.1%) at three concentration levels (0.05, 0.1 and 1 mg kg-1) for the interday test (n = 15). The limit of quantification (LOQ) and detection (LOD) of the method for different matrices were 0.01 and 0.003 mg kg-1, respectively. In conclusion, the established analytical approach has high sensitivity and good accuracy and precision and is suitable for monitoring chlormequat, fosetyl-aluminium and phosphonic acid residues in maize and soybean.

Kinetics of Electron Transfer Reaction Between Co(II) and Chlorate Ions: Isothermal Reactor Design and Experimental Validation

The Batch Stirred Tank Reactor (BSTR) has been commonly used for decades in the chemical process industries and even on a pilot plant or laboratory scale whenever expensive and delicate raw materials and products such as pharmaceuticals or fragile transition metal complexes are involved. This research article describes the details of isothermal BSTR and subsequent experimental validation of the rate law discovered in the previous paper of this series on the electron transfer reaction between Co(II) and chlorate ions in acetic acid solution. A Series of tests were performed to evaluate the efficiency of the BSTR at multiple temperatures and illustrate the differences between the theoretical and experimental conversion of potassium chlorate through relative error. The experimental conversions are calculated with the design equation. Theoretical and experimental conversions are correlated and proportional to the initial concentrations of the reactant and electron transfer reaction among the reactants. Based on the parameters of the design equation, a set with average parameters was chosen and tested over BSTR. The model was then validated for different temperatures and conversions. A design equation for the BSTR has been written and applied for the conversions of 25%, 50%, 75%, and 95%. The time interval is going to be predicted by the model to achieve the desired conversions. The percent relative error between predicted and experimental conversions clearly shows the modeland#39;s predictability, power, and reliability. The precision of the observed rate constant for the electron transfer reaction is found to be 2.2023and#215;〖10〗^(-2 )%

Rutting performance of asphalt mixtures containing treated RCA and reinforced by carbon fibers

This study examined the rutting performance of hot asphalt mixtures containing treated RCA and reinforced by carbon fibers. The methodology involved substituting RCA instead of coarse virgin aggregates in the several percentages (20, 40, 60, 80, and 100%) that were treated by being submerged for 24 hours in an acetic acid solution with a concentration of 0.1M. Carbon fibers were added in several percentages of 0.15, 0.25, and 0.35% by the entire weight of the mix to produce cylindrical specimens (4×2.5 inches) for evaluating the Marshall and volumetric properties, and rectangular slabs (30×40×5 cm) for evaluating rutting resistance. The study finds, that incorporating RCA and carbon fibers did not substantially affect the volumetric characteristics of asphalt mixtures, but Marshall's stability increased. The combination containing 60% RCA and 0.35% carbon fibers showed the greatest increase in Marshall stability, which was 35.81% over the control mixture. The addition of RCA led to a reduction in the rutting performance, whereas the addition of carbon fibers increased it, as seen by a decrease in rutting depth. The combination incorporating 40% RCA and 0.35% carbon fibers exhibited a minimum rutting depth of 40.64% lower than the control mixture. The combination incorporating 20% RCA and 0.35% carbon fibers exhibited the maximum level of dynamic stability, which was 1.64 times greater than the control mixture.

Copper-containing POM-based hybrid P2Mo22V4Cu4 nanocluster as heterogeneous catalyst for the light-driven hydroxylation of benzene to phenol.

The current traditional phenol production process has many shortcomings, and the efficient and clean photocatalytic one-step oxidation to phenol is gradually attracting attention. Heteropolyacids (PMo10V2) with high-density Lewis acid active sites and excellent photoelectron transfer ability are ideal choices for catalytic reactions. In this study, a copper-modified isolated dimeric hybrid nanocluster, [Cu(pyim)2]2[Cu(pyim)2(P2MoVI20MoV2VIV4O82)]2·(H2O) (pyim = [2-(pyridin-2-yl)imidazole]), was synthesized by a convenient hydrothermal method. The structural analysis demonstrated that the compound was composed of metal-organic complexes containing pyim ligands, Keggin-type heteropolyacids, and transition metal copper ions. Remarkably, this not only solves the difficulty that the heteropolymeric acid cannot be recovered by dissolving in the solvent but also introduces the copper atom as a second active center. The catalyst exhibited a benzene conversion of 15.6% and a selectivity of 85.2% in a mixed solution of acetonitrile and acetic acid under optimal reaction conditions. After four catalytic cycles, the PXRD pattern proved that the catalyst was still stable. This study provides a good idea for photocatalytic reactions and other environmental applications.

An iron-containing POM-based hybrid compound as a heterogeneous catalyst for one-step hydroxylation of benzene to phenol.

It is a major challenge to perform one-pot hydroxylation of benzene to phenol under mild conditions, which replaces the environmentally harmful cumene method. Thus, finding highly efficient heterogeneous catalysts that can be recycled is extremely significant. Herein, a (POM)-based hybrid compound {[FeII(pyim)2(C2H5O)][FeII(pyim)2(H2O)][PMoV2MoVI9VIV3O42]}·H2O (pyim = 2-(2-pyridyl)benzimidazole) (Fe2-PMo11V3) was successfully prepared by hydrothermal synthesis using typical Keggin POMs, iron ions and pyim ligands. Single-crystal diffraction shows that the Fe-pyim unit in Fe2-PMo11V3 forms a stable double-supported skeleton by Fe-O bonding to the polyacid anion. Remarkably, due to the introduction of vanadium, Fe2-PMo11V3 forms a divanadium-capped conformation. Benzene oxidation experiments indicated that Fe2-PMo11V3 can catalyze the benzene hydroxylation reaction to phenol in a mixed solution of acetonitrile and acetic acid containing H2O2 at 60 °C, affording a phenol yield of about 16.2% and a selectivity of about 94%.

Isolation and Characterization of Active Alkaloid Compounds from Cinnamomum Verum Cortexes and Proof of their Medicinal Efficacy against Pathogenic Fungus Alternaria Alternate Causing Upper Respiratory Tract Inflammatory Disease

Six alkaloid compounds were isolated (the discovery of a natural drug, which is a combination of the six alkaloid compounds). Alkaloids viz., 1,3,5-Triazine-2-carboxylic acid, 4-amino-6-methyl; 1,2,4-Triazino[5,6-E][1,2,4]-triazine-3,6-dione, hexahydro; 2-(4,5-Dihydro-3-methyl-5-oxo-1-phenyl-4-pyrazole)-5-nitrobenzoic acid; 4-metyl-3,4-dihydro-[1,2,3] trizolo [4,5-d] pyrimidine-5,7-dione; Propanoic acid-3-(perhydro-2,5-dioxo-imidazol [4,5-d] imidazole-1-yl) and 1,2,3-Triazolo[4,5-f] benzotriazole- 4,8(4H,8H)-dione, were isolated from Cinnamomum verum cortexes by using ethanolic acetic acid, sulphuric acid, and ammonia solvents, and they were characterized by using preliminary qualitative tests, gas chromatography-mass spectrumGC-MASS. The medicinal efficacy was studied for these six alkaloidic compounds theoretically by using the Autodock program and the results showed the presence of high efficacy of the compounds. Then the medicinal efficacy was measured biologically for the six compounds mixture in vitro depending on the synergistic interaction principle by using various concentrations (5, 10, 15, 20, and 25 mg/ml) by using of agar diffusion technique. The results showed that the six alkaloidic compounds’ mixture is biologically active against Alternaria alternate fungus, where the inhibition zone diameters were recorded equal to 27, 33, 41, 45, and 49 mm respectively towards the pathogenic fungus. Also, cytotoxicity tests for the different concentrations of six active alkaloid compounds mixture proved there is no toxic effect belonging to them towards red blood cells, and no hemolysis effect appeared in blood cells. Therefore, six alkaloid compounds isolated from Cinnamomum verum cortexes can be used as active drugs for the treatment of various diseases especially those caused by pathogenic fungi represented by Alternaria alternate, without any side effects.

The effect of citric and acetic acid treatment on gelatin production from catfish skin

The demand for halal gelatin is increasing, but the supply is decreasing. One solution to this problem is to produce halal gelatin from fishing waste, particularly catfish skin. A study was conducted to determine the impact of adding acid to the gelatin extraction process. Citric and acetic acid were used at concentrations of 0.05%, 0.075%, and 0.1%. The yield of gelatin varied from 14.97% to 24.1% depending on the concentration of acid used. The highest yield was obtained using a concentrated solution of acetic acid. Gelatin extracted using a citric acid concentration of 0.075% had the lowest water content. The pH of the solution ranged from 4 to 5, and the viscosity ranged from 10 to 14 MPa. The resulting gelatin exhibited a strength of between 200 and 259 blooms. The production process that used acetic acid on immersion was the most efficient because it resulted in high quantities of gelatin, low water content and viscosity, and good gel strength.

The anti-inflammatory effects of antidepressants on colitis.

Clomipramine (tricyclic antidepressant), Risperidone (a non-typical antidepressant), and Escitalopram (selective serotonin reuptake inhibitor antidepressant) might be good candidates for investigating the anti-colitis activity. The incidence of depression with ulcerative colitis in patients has led to the use of antidepressants in their treatment. In addition to the antidepressant effect of these drugs, anti-inflammatory effects have also been reported. In this study, 36 rats were used 2 ml of 3% acetic acid solution rectally to show the colitis. Then, Clomipramine (25 mg/kg), Escitalopram (10 mg/kg), Prednisolone (5 mg/kg), Risperidone (2 mg/kg), and normal saline as the control was administered orally for six days. The levels of Tumor Necrosis factor-alpha (TNF-α), Interleukin-6 (IL-6), and myeloperoxidase (MPO) were measured by Enzyme-linked immune sorbent assay (ELISA), and changes in the tissue pathology were investigated. IL-6 level was significantly reduced after the administration of clomipramine and Prednisolone (p=0.025). Risperidone has significantly reduced MPO activity in colonic tissue (P=0.006). We did find no statistical decrease in MPO activity and TNF-α and IL-6 levels after consumption of Escitalopram (p>0.05). Clomipramine showed the best anti-inflammatory effect compared to Escitalopram and Risperidone. Therefore, clomipramine showed the best relieving effect on inflammation of ulcerative colitis in rats.

Molecular Dynamics of the Norbornyl Cation in Solution and Its Generation in Winstein-Trifan Solvolysis: The Timing of Sigma Bridging.

Molecular dynamics simulations were performed on the solvolyses of exo- and endo-norbornyl brosylate and for the "nonclassical" σ-bridged norbornyl cation in an acetic acid solution. This computational modeling of the original Winstein-Trifan experiment confirms that exo-solvolysis is accompanied by σ-bridging in the transition state, while endo-solvolysis is not; σ-bridging eventually occurs in a dynamically stepwise fashion. Simulations of the norbornyl cation in solution show typical vibrations due to zero-point and thermal vibrations but no tendency to sample localized "classical cation" geometries.

Electrical conductivity of heterogeneous ion exchange membranes in solutions of mono-, di- and tricarboxylic acids and its effect on the process of electrodialysis of solutions containing organic acids

In this study, the electrical conductivity of cation-exchange and anion-exchange membranes was studied in solutions containing both strong (sodium chloride and acetate) and weak (acetic, succinic and citric acids) electrolytes. The results obtained indicate that the concentration dependence of the electrical conductivity of membranes in weak electrolytes differs significantly from that observed for solutions of strong electrolytes. In the case of an acetic acid solution, the electrical conductivity of the membranes is higher than that of the equilibrium solution over the entire range of concentrations that were studied. It has been shown that existing models of the transport and structural organization of membranes allows describing the structural parameters of ion-exchange membranes in contact with strong electrolytes. In sodium chloride and sodium acetate solutions, the obtained dependences were processed within the framework of microheterogeneous and three-wire models to establish the influence of the nature of the electrolyte on the transport and structural characteristics of the membranes. The dependence of electrical conductivity on the concentration of a weak electrolyte solution does not allow the use of either microheterogeneous or extended three-wire models for the description of the structure-property relationship of ion-exchange materials. It has been shown that in acetic acid and partially succinic acid solutions, the solution provides the main contribution to the resistance of the electromembrane system. Based on the results obtained from measuring electrical conductivity, changes in the design of a laboratory electrodialyzer were proposed and experiments were carried out on desalting a solution of acetic acid. It has been shown that the use of thinner intermembrane separators in the desalting chamber leads to an increase in the integral current efficiency (from 0.32 to 0.44 at 0.6 A/dm2 and the same degree of desalination) and a reduction in specific energy consumption (from 3.0 to 1.9 kWh/mol at 0.6 A/dm2) during desalination of acetic acid. The results obtained can be further used to improve the parameters of the process of obtaining weak acids by bipolar electrodialysis.

Study of the effectiveness of inhibiting corrosion processes in mineralized water-oil environments

Corrosion is a phenomenon that strongly affects many industries. Everything related to metallurgy, shipbuilding, or the oil industry is negatively affected by corrosion processes. This is a big problem, because the number of industrial accidents due to corrosion reaches more than 75%. Therefore, in this work, the effectiveness of inhibition of corrosion processes in mineralized water-oil environments was investigated in detail. The main goal of the article is to study the regularity of corrosion processes in water-oil media of different composition and at different temperature regimes for effective selection of the inhibition mechanism and type of corrosion inhibitor.
 An effective method of reducing the impact of corrosion processes today is the use of inhibitors. This is expedient not only from the point of view of the effectiveness of the action, but also from the point of view of economic expediency. Inhibitors are added to corrosive environments in order to stop or reduce corrosion processes. They can be used as protective barriers that form a protective layer, and as absorbers that prevent oxidation processes. In the future, the type of inhibitor is selected depending on the type of metal and the conditions of the reactions responsible for the occurrence and course of corrosion.
 Currently, the use of corrosion inhibitors is recognized as the most effective way to reduce the intensity of corrosion destruction of metal structures. At the same time, it is impossible to obtain a universal inhibitor that meets the requirements of high efficiency, manufacturability, toxicological safety, and at the same time is obtained in an economically feasible way. Among various corrosion inhibitors, organic ones have shown their effectiveness in protecting low-alloy steels of oil industry equipment.
 Metal samples of St20 steel, the most widely used for the manufacture of oil pipelines and oil production equipment, were used as corroding materials in the study. The pH was changed by adding a solution of acetic acid. The degree of corrosion was determined by the massometric method. The volume of the test solution was 150 cm3, the pH of the solution was adjusted with a 5% acetic acid solution. Alkylimidozoline was used as an inhibitor.
 Judging by the research results, the mineral composition of the aqueous solution largely affects the rate of corrosion. The presence of oil significantly reduces the rate of corrosion due to both blocking the access of oxygen to the system by the oil film and due to the corrosion inertness of the chemical components of the oil. However, it was also found that with an increase in the content of carboxylic acids, the presence of oil does not affect the corrosion rate in any way. Arguably, the alkylamidazoline inhibitor showed a high degree of protection at room temperature, in contrast to studies at high temperatures.

Plasma Electrolytically Surface-Engineered SS316L Bipolar Plates for PEM Fuel Cells

The proton exchange membrane fuel cell (PEMFC) technology is one of the clean energy technologies with advantages like, quick start-up, low working temperature (60-90 oC), high specific energy and specific power, and high reliability. Stainless steel bipolar plates for PEMFC offer many advantages over conventional graphite and graphite composites. Some of them have superior mechanical properties over graphite, the possibility to fabricate in thin cross sections, and easy formation of flow fields by stamping, which is more economical when compared with the grooving of the graphite counterparts. Despite these advantages, metallic bipolar plates are prone to corrosion in fuel cell working conditions which is often overcome by oxide layer formation on the surface. But the interfacial ohmic loss between the metallic bipolar plate and membrane electrode assembly due to oxide formation decreases the overall performance of PEMFC. For combating these problems, there are different surface engineering techniques like chemical vapor deposition, physical vapor deposition, sputtering, thermal nitridation, etc. Among all methods, plasma electrolytic processing has advantages like less processing time, use of environmentally friendly electrolytes, economical process, easy scale-up for mass production and etc.The 316L stainless steel was surface-engineered using the cathodic plasma electrolytic process in two different aqueous electrolytes containing urea and acetic acid, which acted as a nitrogen and carbon source, respectively. The processed samples were characterized using a scanning electron microscope to study surface morphology and for qualitative chemical analysis. It revealed the diffusion of nitrogen and carbon into the surface in respective electrolytes. The electrochemical performance of as-received/bare 316L and surface-engineered samples were evaluated in a simulated fuel cell environment (half-cell conditions). The electrolyte comprised 0.5 M H2SO4 with 2 ppm HF at 80 oC, and it was purged with N2 or air to simulate anodic and cathodic conditions, respectively. The potentiodynamic polarization studies revealed similar active-passive behavior for bare 316L and surface-engineered samples. Different electrochemical parameters like corrosion current density (icorr), corrosion potential (Ecorr), and passive current density (ipassive) were deduced. The corrosion potentials for the bare sample were observed to have -0.306 V and -0.316 V in cathodic and anodic conditions, respectively. After surface modification, corrosion potentials shifted to more noble values, i.e., -0.234 V, -0.250 V for samples processed in urea solution and -0.219 V, -0.198 V for samples processed in the acetic acid solution for anodic and cathodic conditions, respectively. But the surface-modified samples showed higher passive current densities for both anodic and cathodic conditions than the bare sample, suggesting inferior passivation ability.Also, long-term potentiostatic studies for 8 hours were conducted to understand the samples' behavior. The current densities at the end of the test were -28.7 µA cm-2 (anodic condition) and 7.5 µA cm-2 (cathodic condition) for bare samples. While the samples processed in urea solution showed 27.4 and 9.0 µA cm-2, and the samples processed in acetic acid solution had -115.5 and 89.8 µA cm-2 of current densities in anodic and cathodic conditions, respectively. At different loads, the interfacial contact resistance measurements between the samples and the gas diffusion layer for all samples were determined. At a load of 140 N cm-2, the bare SS316L and samples processed in urea and acetic acid solution showed values of 118.82, 26.78, and 10.97 mΩ cm2, respectively. These studies suggest plasma electrolytically processed SS316L in acetic acid solution offers the least interfacial contact resistance of 10.97 mΩ cm2 and almost satisfies the Department of Energy target of 10 mΩ cm2 for metallic bipolar plates. A scale-up of coating in a 4×4 cm area and its performance in a single-cell setup will be highlighted.

Hydrogen Video Imaging System for Visualizing Microstructure-Dependent Hydrogen Diffusion Behaviors in Polycrystalline Metals

Hydrogen diffusion in polycrystalline metals is known to depend on microstructure. The hydrogen-microstructure interactions have been extensively studied last decades, but the microstructure-dependent hydrogen diffusion behavior is still unclear. To clarify the hydrogen diffusion behavior, it is necessary to visualize the time variations of the microscopic hydrogen distribution in polycrystalline metals. Thus, we developed a hydrogen video imaging system (HVIS) in this study to analyze the hydrogen distribution in polycrystalline metals with sub-micrometer spatial and video-rate time resolutions. The inexpensive and atmospheric-control-free system is expected to be widely used as a versatile approach for analyzing the hydrogen-microstructure interaction in detail.Pure polycrystalline Ni (thickness: 125 µm) was used as a specimen. The specimen was electrochemically polished at a constant voltage of 50 V in a mixed solution of perchloric acid and acetic acid. The thickness was approximately 110 µm after polishing. Subsequently, a polyaniline layer (PANI) was polymerized on one side of pure Ni. The specimen was set to the acrylic cell, which is used to preserve a 0.1 M NaOH aqueous solution. So, only the bare Ni side of the specimen was exposed to the 0.1 M NaOH solution. Electrochemical hydrogen charging was conducted at the bare Ni side of the specimen at a constant current density of -10 A / m2. An inverted optical microscope was used to observe the color distribution of the PANI side. In our previous studies,1-3) it has been clarified that PANI changes its color due to the reaction with hydrogen in metals. Thus, the distribution of hydrogen permeated through pure polycrystalline Ni can be observed as a color distribution of PANI during hydrogen charging.The color of PANI was purple before the hydrogen charging. After 20 h of hydrogen charging, the color of PANI partially turned white. If PANI reacts with hydrogen, the color changes from purple or dark blue to yellow or transparent.1,2) Therefore, the local whitening of PANI is thought to be caused by the reaction with atomic state hydrogen permeated through pure polycrystalline Ni. The number of color changed areas increased with time during hydrogen charging. After 120 h of hydrogen charging, the specimen was immersed in a 1 M NaOH aqueous solution to remove PANI. Subsequently, the microstructure of pure polycrystalline Ni was analyzed using FE-SEM and EBSD. It was found that the color changed area of PANI corresponded to the grain boundaries (GBs) of pure Ni. This suggests that the GBs in pure Ni are preferential hydrogen diffusion paths. Furthermore, the clear color change of PANI was observed at the random GBs, while the whitening scarcely occurred at the Σ3 GBs, indicating that the preferential hydrogen diffusion mainly occurred at the random GBs. The results showed that HVIS can clarify the microstructure-dependent hydrogen diffusion in polycrystalline metals.

An optical fiber chlorogenic acid sensor using a Chitosan membrane coated bent optical fiber probe

Hydrogel polymers have hydrophilic function groups bonded on the polymer's backbone network. Water molecules and compounds soluble in aqueous solution can permeate into hydrogel's network. This property was employed in this work in developing an optical fiber chemical sensor for detecting chlorogenic acid (CGA). A Chitosan membrane was coated on a bent optical fiber probe (BOFP) by simply dipping the BOFP into a Chitosan solution, which was made by dissolving solid Chitosan in a 2 % acetic acid solution, and pulling out. When such a Chitosan-coated BOFP was exposed to CGA in an aqueous sample solution, CGA molecules permeate into the Chitosan membrane, and were detected through monitoring the compound's intrinsic optical absorption signal at 400 nm. Chitosan has one amine group on each of its glucose rings, which helps the membrane concentrating CGA (a weak acid) from aqueous sample solution. Therefore, the sensor shows high sensitivity in detecting CGA with a detection limit of 0.018 μg/mL. The sensor's response to CGA is reversible, because CGA permeation into/out of the polymer network is a reversible process. The effectiveness of the developed sensor for detecting CGA was verified though analyzing CGA in green coffee extract products. The analytical results obtained with the developed sensor agree well with results obtained with a traditional UV/Vis optical absorption spectrometric method. The effectiveness of the sensor for analyzing CGA in green coffee extract samples was also verified through standard addition and recovery experiment with obtained recovery rate ranging from 97 % to 100 %.

High-Power Impulse Magnetron Sputter-Deposited Chromium-Based Coatings for Corrosion Protection

The use of high-power impulse magnetron sputtering (HIPIMS) to deposit chromium-based thin films on brass substrates for the purpose of corrosion-protective coating was investigated. By varying the process parameters (pulse frequency, pulse width and N2 flow rate) and structure design, including single-layer and multilayer structures, the obtained results revealed that the Cr-N films deposited through the use of HIPIMS exhibited higher film density and corrosion resistance compared to traditional direct-current magnetron sputtering. Based on the results of a field test using copper-accelerated acetic acid solution, the Cr-N film with a multilayered structure can further extend the time to corrosion onset. This is because the bottom layer in the multilayer structure can block structural defects in the layer above it, effectively reducing the penetration of corrosive agents into the substrate. The high bias voltage, coupled with increased temperature during deposition, led to a dezincification effect, resulting in the reduced adhesion of the film to the substrate and decreased overall corrosion resistance.