Mechanism Analysis of Discharge Energy in the Electrostatic-Field-Induced Electrolyte Jet Micro-EDM

The discharge energy determines the machining resolution, minimum processable feature size, and surface roughness, which makes it a hot research topic in the microelectrical discharge machining (EDM) field. In this paper, a kind of novel discharge-energy-generation method in micro-EDM is investigated. In this method, the opposite induced charges on the electrolyte jet and workpiece serve as the source of the discharge energy. The operating mechanism of this discharge energy is revealed by analyzing the equivalent discharge circuit. The unique discharge current and voltage between the electrolyte jet and the workpiece are sampled and investigated. In contrast with the pulsating energy in conventional EDM, this study shows that the direct current (DC) voltage source can automatically generate a continuously periodical pulsating discharge in the electrostatic-field-induced electrolyte jet (E-Jet) EDM process. After further analyzing the electric signals in a single discharge process, it can be found that the interelectrode voltage experienced a continuous sharp electric breakdown, a nearly unchanging process, and a fast exponential recharging process. The discharge frequency increases as the electrolyte concentration and interelectrode voltage increase but decreases as the interelectrode distance increases. The discharge energy per pulse increases with the increasing interelectrode distance and electrolyte concentration but with the decreasing interelectrode voltage. Finally, the electrostatic-field-induced discharge-energy generation and change mechanisms are revealed, which provides a feasible method for micro-EDM with continuous tiny pulsed energy only using the DC power supply.

Effect of Electrolyte Concentration on the Electrochemical Performance of Spray Deposited LiFePO4

LiFePO₄ is a common electrode cathode material that still needs some improvements regarding its electronic conductivity and the synthesis process in order to be easily scalable. In this work, a simple, multiple-pass deposition technique was utilized in which the spray-gun was moved across the substrate creating a "wet film", in which-after thermal annealing at very mild temperatures (i.e., 65 °C)-a LiFePO₄ cathode was formed on graphite. The growth of the LiFePO₄ layer was confirmed via X-ray diffraction, Raman spectroscopy and X-ray photoelectron spectroscopy. The layer was thick, consisting of agglomerated non-uniform flake-like particles with an average diameter of 1.5 to 3 μm. The cathode was tested in different LiOH concentrations of 0.5 M, 1 M, and 2 M, indicating an quasi-rectangular and nearly symmetric shape ascribed to non-faradaic charging processes, with the highest ion transfer for 2 M LiOH (i.e., 6.2 × 10^-9 cm²/cm). Nevertheless, the 1 M aqueous LiOH electrolyte presented both satisfactory ion storage and stability. In particular, the diffusion coefficient was estimated to be 5.46 × 10^-9 cm²/s, with 12 mAh/g and a 99% capacity retention rate after 100 cycles.

Ultra-Low Concentration Electrolyte Enabling LiF-Rich SEI and Dense Plating/Stripping Processes for Lithium Metal Batteries

The interface structure of the electrode is closely related to the electrochemical performance of lithium-metal batteries (LMBs). In particular, a high-quality solid electrode interface (SEI) and uniform, dense lithium plating/stripping processes play a key role in achieving stable LMBs. Herein, a LiF-rich SEI and a uniform and dense plating/stripping process of the electrolyte by reducing the electrolyte concentration without changing the solvation structure, thereby avoiding the high cost and poor wetting properties of high-concentration electrolytes are achieved. The ultra-low concentration electrolyte with an unchanged Li⁺ solvation structure can restrain the inhomogeneous diffusion flux of Li⁺ , thereby achieving more uniform lithium deposition and stripping processes while maintaining a LiF-rich SEI. The LiIICu battery with this electrolyte exhibits enhanced cycling stability for 1000 cycles with a coulombic efficiency of 99% at 1 mA cm^-2 and 1 mAh cm^-2 . For the LiIILiFePO₄ pouch cell, the capacity retention values at 0.5 and 1 C are 98.6% and 91.4%, respectively. This study offers a new perspective for the commercial application of low-cost electrolytes with ultra-low concentrations and high concentration effects.

Stabilizing the Nanosurface of LiNiO2 Electrodes by Varying the Electrolyte Concentration: Correlation with Initial Electrochemical Behaviors for Use in Aqueous Li-Ion Batteries

This study attempted to stabilize the nanosurface of LiNiO₂ (LNO) electrodes by varying the electrolyte concentration, significantly influencing its initial electrochemical behaviors for use in aqueous lithium-ion batteries. The charge/discharge capacities, reversibility, and cyclability of LNO were improved during initial cycles with an increase in the concentration of lithium bis(trifluoromethanesulfonyl)imide (LiTFSI). As determined by the galvanostatic intermittent titration technique, the superior diffusivity of Li⁺ ions in the LNO electrode is also obtained in the concentrated electrolyte. Nanoscale observation of the LNO surface revealed that its morphology is maintained relatively well in the concentrated electrolyte while it is destroyed in dilute electrolytes after the initial electrochemical cycles. These results are considered to be attributable to the variation of the interface condition in the electrical double layer with an increase in the electrolyte concentration, thus stabilizing the nanosurface of LNO by suppressing the dissolution of Ni ions from the surface. Additionally, in situ X-ray diffraction analysis demonstrated that LNO shows more stable phase transitions and volume changes as the electrolyte concentration increases, indicating that its structural changes in bulk can be directly related to the state of the nanosurface, which has a positive impact on the initial electrochemical behaviors in this system.

Influence of Electrolyte Concentration on Single-Molecule Sensing of Perfluorocarboxylic Acids

Perfluorocarboxylic acids (PFCAs) are an emerging class of persistent organic pollutants. During the fabrication process, it is unavoidable to form PFCA homologs or isomers which exhibit distinct occurrence, bioaccumulation, and toxicity. The precision measurement of PFCAs is therefore of significant importance. However, the existing characterization techniques, such as LC-MS/MS, cannot fully meet the requirement of isomer-specific analysis, largely due to the lack of authentic standards. Single-molecule sensors (SMSs) based on nanopore electrochemistry may be a feasible solution for PFCAs determination, thanks to their ultra-high spatiotemporal resolutions. Hence, as a first step, this work was to elucidate the influence of electrolyte concentration on the four most critical indicators of nanopore measurements, and furthermore, performance of nanopore SMSs. More specifically, three of the most representative short-chain PFCAs, perfluoropentanoic acid (PFPeA), perfluorohexanoic acid (PFHxA) and perfluoroheptanoic acid (PFHpA), were adopted as the target analytes, aerolysin nanopore was employed as the sensing interface, and 2, 3 and 4 M KCl solutions were used as electrolytes. It was found that, when the concentration of KCl solution increased from 2 to 4 M, the conductance of aerolysin nanopore increased almost linearly at a rate of 0.5 nS per molar KCl within the whole voltage range, the current blockade of PFPeA at -50 mV increased from 61.74 to 66.57% owing to the enhanced steric exclusion effect, the maximum dwell time was more than doubled from 14.5 to 31.5 ms, and the barrier limited capture rate increased by 8.3 times from 0.46 to 3.85 Hz. As a result, when using 4 M KCl as the electrolyte, over 90% of the PFPeA, PFHxA and PFHpA were accurately identified from a mixed sample, and the calculated limit of detection of PFPeA reached 320 nM, more than 24 times lower than in 2 M KCl. It was thus clear that tuning the electrolyte concentration was a simple but very effective approach to improve the performance of nanopore SMSs for PFCAs determination.

Poorly Soluble 2,6-Dimethoxy-9,10-anthraquinone Cathode for Lithium-Ion Batteries: The Role of Electrolyte Concentration

In this work, a 9,10-anthraquinone (AQ) derivative functionalized by two methoxy groups, 2,6-dimethoxy-9,10-anthraquinone (DMAQ), was synthesized and its electrochemical performance was comprehensively studied with different electrolyte concentrations. Density functional theory (DFT) calculations demonstrate that there exists a conjugation effect between oxygen atoms of methoxy groups and the AQ skeleton, which could extend the conjugate plane and increase intermolecular interaction. As a result, DMAQ shows considerably reduced solubility in ether solvent/electrolyte and greatly enhanced cycling performance compared with those of AQ. Interestingly, it is found that the electrolyte concentration plays an important role in determining the electrochemical performance. Cycling under a relatively low (2 M) or high (6 M) concentration electrolyte of lithium bis(trifluoromethanesulfonyl)imide in a mixture solvent of 1,3-dioxolane and 1,2-dimethoxyethane (1/1, v/v) displays unsatisfied cell performance. While a moderate electrolyte concentration of 4 M delivers the highest initial capacity and the best cycling stability. The work would shed light on the rational molecular structure design and electrolyte concentration optimization for achieving the high electrochemical performance of organic electrode materials.

Relationships between Electrolyte Concentration and the Supercapacitive Swing Adsorption of CO2

We quantitatively investigate the influence of the NaCl electrolyte concentration on the adsorptive and energetic characteristics of supercapacitive swing adsorption (SSA) for the separation of CO₂ from a simulated flue gas mixture containing 15% CO₂ and 85% N₂. The investigated concentrations were that of deionized water, 0.010, 0.10, 1.0, 3.0, and 5.0 M NaCl. We find that the energetic metrics strongly improve with the increasing NaCl concentration, whereas the adsorptive metrics improve by a comparatively small degree. The CO₂ adsorption capacity increases up to 1.0 M NaCl and then remains constant. The adsorption rate remains near constant for all concentrations, except that it is somewhat smaller for deionized water. The charge efficiency also remains near constant for all experiments with 30 min potentiostatic holding steps but near doubles for pure water when the potential holding step is doubled, because the chemical adsorption equilibrium is reached only after 60 min. The results can be most satisfactorily explained by assuming that both ionic and nonionic adsorption mechanisms contribute to the SSA effect.

Optimization of electrochemical reaction for nitrogen removal from biological secondary-treated milking centre wastewater

In order to remove the residual nitrogen from the secondary-treated milking centre wastewater, the electrochemical reaction including NH4-N oxidation and NOx-N reduction has been known as a relatively simple technique. Through the present study, the electrochemical reactor using the Ti-coated IrO2 anode and stainless steel cathode was optimized for practical use on farm. The key operational parameters [electrode area (EA) (cm(2)/L), current density (CD) (A/cm(2)), electrolyte concentration (EC) (mg/L as NaCl), and reaction time (RT) (min)] were selected and their effects were evaluated using response surface methodology for the responses of nitrogen and colour removal efficiencies, and power consumption. The experimental design was followed for the central composite design as a fractional factorial design. As a result of the analysis of variance, the p-values of the second-order polynomial models for three responses were significantly fit to the empirical values. The nitrogen removal was significantly influenced by CD, EC, and RT (p < .05), whereas colour removal was significantly governed by EA, CD, RT, the interaction of EA and EC (p < .05). For higher efficiency of nitrogen removal over 90%, the combination of [EA, 20 cm(2)/L; CD, 0.044 A/cm(2); EC, 3.87 g/L as NaCl; RT, 240 min] was revealed as an optimal operational condition. The investigation on cathodic reduction of NOx-N may be required with respect to nitrite and nitrate separately as a future work.

Electrochemical treatment of cork boiling wastewater with a boron-doped diamond anode

Anodic oxidation at a boron-doped diamond anode of cork boiling wastewater was successfully used for mineralization and biodegradability enhancement required for effluent discharge or subsequent biological treatment, respectively. The influence of the applied current density (30-70 mA/cm2) and the background electrolyte concentration (0-1.5 g/L Na2SO4) on the performance of the electrochemical oxidation was investigated. The supporting electrolyte was required to achieve conductivities that enabled anodic oxidation at the highest current intensities applied. The results indicated that pollutant removal increased with the applied current density, and after 8 h, reductions greater than 90% were achieved for COD, dissolved organic carbon, total phenols and colour. The biodegradability enhancement was from 0.13 to 0.59 and from 0.23 to 0.72 for the BOD/COD ratios with BOD of 5 and 20 days' incubation period, respectively. The tests without added electrolyte were performed at lower applied electrical charges (15 mA/cm2 or 30 V) with good organic load removal (up to 80%). For an applied current density of 30 mA/cm2, there was a minimum of electric conductivity of 1.9 mS/cm (corresponding to 0.75 g/L of Na2SO4), which minimized the specific energy consumption.

Effect of disjoining pressure on terminal velocity of a bubble sliding along an inclined wall

The influence of salt concentration on the terminal velocities of gravity-driven single bubbles sliding along an inclined glass wall has been investigated, in an effort to establish whether surface forces acting between the wall and the bubble influence the latter's mobility. A simple sliding bubble apparatus was employed to measure the terminal velocities of air bubbles with radii ranging from 0.3 to 1.5 mm sliding along the interior wall of an inclined Pyrex glass cylinder with inclination angles between 0.6 and 40.1°. Experiments were performed in pure water, 10 mM and 100 mM KCl solutions. We compared our experimental results with a theory by Hodges et al. which considers hydrodynamic forces only, and with a theory developed by two of us which considers surface forces to play a significant role. Our experimental results demonstrate that the terminal velocity of the bubble not only varies with the angle of inclination and the bubble size but also with the salt concentration, particularly at low inclination angles of ∼1-5°, indicating that double-layer forces between the bubble and the wall influence the sliding behavior. This is the first demonstration that terminal velocities of sliding bubbles are affected by disjoining pressure.

Diuretic activity of leaves of Plectranthus amboinicus (Lour) Spreng in male albino rats

The shade-dried powder of leaves of Plectranthus amboinicus (Lour) Spreng was subjected to successive extraction using the various solvents (petroleum ether, chloroform, ethanol and water) in increasing order of polarity. The preliminary phytochemical analyses were carried out for all the extracts. The analyses of the leaves revealed the presence of alkaloids, carbohydrates, glycosides, proteins, amino acids, flavonoids, quinine, tannins, phenolic compounds and terpenoids. Since the phytoconstituents present in the ethanolic and aqueous extracts were similar, both the extracts were selected for further study. The diuretic properties of ethanolic and aqueous extracts were evaluated by determination of urine volume and electrolyte concentration in male albino rats. Furosemide (10 mg/kg) was used as standard while normal saline (0.9%) was used as control. Both ethanolic and aqueous extracts (500 mg/kg) have shown significant increase in the volume of urine and urinary concentration of Na, K and Cl ions. Thus, from the is study it may be concluded that the leaves of P. amboinicus (Lour) Spreng possess diuretic activities.