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The electrochemical performance of mesocarbon microbeads (MCMB)-lithium manganese oxide (LMO) spinel cells is examined by cyclic voltammetry, galvanostatic cycling and electrochemical impedance spectroscopy. The loss in capacity in full-cells is attributed to occurrence of parasitic reactions at the two electrodes. The contribution of each electrode in full-cell degradation is ascertained through testing of MCMB and LMO half-cells, with the former exhibiting a faster rate of degradation as compared to the latter. Lithium diffusion coefficient of MCMB and LMO electrodes are determined using the galvanostatic intermittent titration technique at various stages of cycling. The experimentally measured parameters are used to simulate the electrochemical behavior of MCMB and LMO half-cells. The computed capacity and cell potential variation show good agreement with experimentally obtained data for half-cells at 1C and 2C currents. The MCMB half-cell simulations reveal that loss in discharge capacity occurs due to thickening of SEI film, increase in gas formation and loss in cyclable lithium. Simulations of LMO half-cells show that capacity loss with cycling is a result of reduction in active material, increase in surface resistance with inactive material deposition and loss in cyclable lithium.
Gastroesophageal carcinoma has a 5-year survival rate of 20%. Esophagogastrectomy is a significant life-altering operation which interferes with a patient’s ability to eat food as a normal social interaction. Dumping syndrome, delayed gastric emptying, and reflux are encountered after surgery. In addition, loss of appetite and body weight occurs. Fatigue is universally encountered. We conducted this study to evaluate whether a structured cancer nutrition and rehabilitation program has an effect on the symptoms and quality of life of patients with gastroesophageal cancer.
We report KFe(SO4)2 as a novel cathode material for potassium-ion batteries. The synthesis of phase-pure KFe(SO4)2 is confirmed through Rietveld refinement of X-ray diffraction data, and the ion diffusion path and possible positions of K+ ions in the crystal structure are verified using bond-valence sum analysis. In addition, the theoretical average voltage, ion diffusion paths, and associated activation barrier energies obtained by first-principles calculations predict feasibility of the KFe(SO4)2 as a robust cathode for potassium-ion batteries. . Experimentally, the average working voltage of KFe(SO4)2 is approximately 3.3 V (vs. K+/K) assisted by Fe3+/2+ redox pair, and the resulting specific capacity (94 mAh g−1) obtained at C/20 approaches to the theoretical capacity, 94 mAh g−1. In addition, the capacity retention of KFe(SO4)2 at 2C was approximately 80% of the initial capacity after 300 cycles, with a Coulombic efficiency of over 99%. X-ray absorption near-edge structure and operando synchrotron X-ray diffraction analyses reveals the reversible change of the crystal structure with a minimal volume difference (1.83%) by occurrence of Fe3+/2+ redox reaction during dis/charge. The demonstrated excellent structural stability of KFe(SO4)2 endorses feasibility of the KFe(SO4)2 as a sustainable cathode for potassium-ion batteries.
The understanding of volume change behavior of a silicon particle is necessary to design a new negative electrode using silicon active materials. Here, the drastic volume expansion behavior of a silicon particle with μm-size was in-situ observed in order to find apparent volume expansion ratio during the first lithiation in several kinds of electrolytes by using single particle measurement technique. This technique is very useful not only to find the intrinsic electrochemical properties but also to observe the volume change behavior of one electrode active materials particle. The apparent volume expansion ratio of a silicon particle was larger than theoretical expectation because the measured silicon particles were secondary particles which contained some space between the primary particles. In addition, the volume expansion behavior during the first charging was independent on the Li salt, solvents and the applied charging current density.
Electrochemical deposition and dissolution of magnesium (Mg) has been examined in triethylene glycol dimethyl ether (triglyme, G3) dissolving magnesium bis(triflouromethanesulfonyl)amide, Mg(TFSA)2. The voltammetric current responses at platinum (Pt) electrode in the G3-based electrolytes revealed that the Mg deposition/dissolution process depends on the Mg species in the solution phase. The addition of alkoxides, Mg(OC n H2n+1)2, was effective on the reversibility of the process in Mg(TFSA)2/G3. Higher anodic current corresponding to the electrochemical dissolution was observed in the electrolyte solution containing Mg(OC2H5)2 as the additive. The morphology of the Mg deposition at the Pt substrate also depended on the additive Mg-alkoxides. The resulting Mg(TFSA)2/G3 solutions containing Mg-alkoxides were found to be a possible electrolyte system for rechargeable Mg battery operating at ambient temperature.
Improvement in the rate properties of orthorhombic LiVOPO4 was investigated and it was found that making a fine powder of LiVOPO4 by the mechanical milling pretreatment is effective for increasing the de-intercalation capacity of Li from LiVOPO4. The electrochemical de-intercalation capacity at high current density can further increase by optimizing the acetylene black amount as a conducting binder. The optimized acetylene black amount was 15wt.% and intercalation capacity of Li was achieved a value of 100 and 60mAhg−1 at high rate condition of C/5 (0.4mAcm−2) and 1C (2mAcm−2), respectively.
Executive functioning (EF) impairments are common in schizophrenia. There are two propositions regarding the causes of these impairments: (1) executive impairments are the result of the compounding effects of deficits in lower order cognitive skills (e.g. processing speed, attention) or (2) EF impairments exist in their own right regardless of lower order skills. It is difficult to examine the separable effects of lower order cognitive skills on EF given the overlap required to complete most neuropsychological measures. One battery designed to parcel out the contributions of lower order skills from EF is the Delis–Kaplan Executive Function System (D-KEFS). Inhibition and switching specifically were examined using the D-KEFS versions of the Stroop and Trails task. No group differences in task performance after controlling for lower level skills would provide evidence for a generalised cognitive deficit. Group differences remaining after controlling for these influences would suggest a disproportionate deficit. Results supported both propositions. On both tasks, group differences reflecting slowed reaction time in the schizophrenia group disappeared when lower order skills were controlled for. Differences between groups performance in errors were only evident on the most complex versions of each task with more errors made by the schizophrenia group. These results suggest that (1) both RT and error data are needed to provide a full picture of performance and (2) the relationship between lower order and EF is too complex to provide support for one or the other proposal.
The effect of surface palladium films on the electrochemical properties of hydride-forming metal alloys used as cathode materials in Ni-metal hydride cells has been studied. The results indicate that the presence of surface Pd improved the discharge capacity and rate capability of the hydride electrodes. The enhancement in performance may be explained on the basis of the electrocatalytic effect of Pd on the kinetics of the hydrogen absorption/desorption (hydriding/dehydriding) reactions.
Sulfonated poly(ether ether ketone) (C-SPEEK) membranes with pendent carboxylic acid groups are prepared and first investigated for vanadium flow battery (VFB) application. The introduction of carboxylic acid groups can effectively improve the ion conductivities of C-SPEEK membranes, while, keep their ion selectivities. The prepared C-SPEEK membranes exhibit excellent performance under VFB operating condition. VFB single cell assembled with C-SPEEK-50 membranes shows much higher energy efficiency (85% Vs 82%) and columbic efficiency (97.3% Vs 94.6%) than that assembled with Nafion 115. The membrane keeps a stable performance after more than 180 cycles charge–discharge test, showing good stability.
Methods of measuring current transients due to solid particle impingement are presented. The processes involved form the basis of slurry erosion–corrosion, whereby the rate of wastage of a metal is greater than the sum of the separate erosion rate and the corrosion rate, when under exposure to a flowing solid/liquid slurry. The measurements are electrochemical in nature, backed up by a coupled acoustic emission sensor to detect slurry impact on the metal surface. Evidence is shown that it is possible to measure a threshold energy of the impacting slurry above which the passivating surface oxide is ruptured by erosion, and below which it is not. Some consequences of depassivation are discussed, and it is shown that depassivation of stainless steels by the impacting slurry can stimulate the formation of metastable pits in a chloride containing environment.
Ternary composites of manganese dioxide/graphene nanosheets/carbon nanotubes (MnO2/GNS/CNTs) have been fabricated through a facile chemical method involving in situ growth of MnO2 particles on the surface of graphene oxide (GO)/CNT hybrid following by the chemical reduction of GO. The morphology and structure of the resulting materials are characterized using scanning electron microscopy (SEM), energy dispersive spectroscopy (EDS), ultraviolet/visible (UV/Vis) spectroscopy and X-ray diffraction (XRD). The supercapacitive behaviors of the sample electrodes are evaluated by cyclic voltammetry (CV), galvanostatic charge/discharge and electrochemical impedance spectroscopy (EIS) techniques in 1M Na2SO4 aqueous solution. The electrochemical measurements show that the specific capacitance of MnO2/GNS/CNT composite at the scan rate of 20mVs−1 (367Fg−1) is much higher than that of pure MnO2 (55.7Fg−1), binary MnO2/CNT (180Fg−1) and MnO2/GNS (310Fg−1) composites. In addition, the MnO2/GNS/CNT composite shows excellent rate capability, with 79.3% capacitance retention after a 5-fold increase in potential scan rate and better cycling stability, with 83% capacitance retention after 3000 cycles. These advances can be attributed to the synergistic effects of GNS and CNT in the composite structure, which facilitates electrolyte ions accessibility to the electrode material during electrochemical process as well as maintaining the mechanical strength.
Effects of the nonionic t-octyl phenoxy polyethoxyethanol (Triton X-100) on electrocrystallization of lead dioxide were investigated on titanium substrates in the bath containing nitric acid solutions and lead nitrate. Two series of samples were produced in the presence (modified samples: PTX) and in the absence of Triton X-100 (unmodified samples: PT) at bath temperatures ranging from 25–100°C. Higher current efficiencies, mechanical strength and more adhesion to Ti substrates were found for modified samples. Results confirm an increase in the overpotential for oxygen evolution during electrodeposition process in the presence of Triton X-100. It is suggested that the accumulation of oxygen species and the growth of crystals could be affected through the aqueous network of the self-assembled surfactants on the electrode surface. A higher overpotential for oxygen evolution reaction was also observed for electrodes made of PTX samples in sulfuric acid solution. Results of the voltammetric experiments and those from laboratory-designed test cells have confirmed a higher charge/discharge performance of modified samples towards the PbO2/PbSO4 transformation in aqueous sulfuric acid solutions. Scanning electron microscopy (SEM) has shown reduced morphological defects of PTX samples at all bath temperatures. This was in agreement with X-ray diffractograms, showing more crystalline appearance and regularity, compared to those of unmodified samples. The sample obtained under optimized conditions (synthesis in the presence of Triton X-100 at a bath temperature around 100°C), had a higher degree of crystallinity and electrochemical activity. The enhanced characteristics of this sample is attributed to its special morphology due to creation of large number of small micropores, strong incorporation of hydrogen species and enhanced proton diffusivity as confirmed by SEM, thermogravimmetric analysis (TGA) and Electrochemical Impedance Spectroscopy (EIS).
Anode active materials, high tap-density ZnO microspheres, with enhanced volumetric capacity and improved cycling performance for nickel-zinc rechargeable batteries have been synthesized via a novel complexing co-precipitation method. The physical and electrochemical properties of the obtained ZnO microsphere are investigated. Notably, tap-density of the resultant ZnO microspheres can reach 3.00g cm−3, three times higher than the commercial conventional ZnO. Compared with the conventional ZnO, the obtained ZnO microspheres have demonstrated superior electrochemical properties, including higher volume specific capacity, improved high-rate ability, and better cyclic stability. At rates of 0.2C and 2C, the obtained ZnO microspheres deliver volumetric capacities of ∼1450 and ∼1110mAhcm−3, respectively, which are about three times higher than those of the conventional ZnO. These performance improvements are attributed to its unique more dense spherical microstructure, thus leading to better reaction reversibility, excellent anti-corrosion ability, lower charge transfer resistance and better inhibiting effect on shape change of the material. Owing to its facile synthesis and outstanding electrochemical properties, this high-density spherical ZnO sample is a promising anode material for fabricating high performance Ni-Zn secondary batteries.
Electrochemical reduction of solid GeO2 has been investigated in the mixed CaCl2-NaCl melt at 1023K for developing a more efficient process for preparation of Ge. Cyclic voltammetry and potentiostatic electrolysis were applied to study the GeO2-loaded metallic cavity electrode. In addition, porous GeO2 pellets were reduced by potentiostatic and constant cell voltage electrolysis with a graphite anode, and the electrolysis products were analyzed by powder X-ray diffraction, scanning electron microscopy and energy-dispersive X-ray spectrometry, focusing on understanding the reduction mechanism and the impact of electrode potential on the product purity. It was found that the reduction of GeO2 to Ge occurred at a potential of about -0.50V (vs. Ag/Ag+), but generating various calcium germanates simultaneously, whose reduction was a little more difficult and needed a potential more negative than -1.00V. However, if the cathode potential exceeded -1.60V, Ca (or Na) - Ge intermetallic compounds might form. These results gave an appropriate potential range between -1.10 and -1.40V for the production of pure germanium. Rapid electrolysis of GeO2 to pure Ge has been realized at a cell voltage of 2.5V with a current efficiency of about 92%.
MoS2 is a promising anode material for sodium ion batteries owing to its two-dimensional layered structure and high specific capacity. But it still exhibits a poor cycle stability and limited rate capability for Na+ storage because of its poor electrical conductivity and structural instability. In this work, MoS2/graphite composite is fabricated by mechanically delaminated and restacked MoS2 and graphite to form two-dimensional composite layers. The graphite sheets will improve electrical conductivity and prevent the aggregation as well as structure collapse of the MoS2 layers during charge–discharge process. The MoS2/graphite composite exhibits excellent Na+ storage properties. It delivers a high discharge specific capacity of 358.2 mAh/g at a current density of 100 mA/g in the first discharge process and with capacity retention of 68.1% after 800 cycles (retains 244 mAh/g). The average discharge specific capacities retain 250.9 and 225.4 mAh/g corresponding to the current densities of 100 and 1000 mA/g, showing excellent rate capability. The improved electrochemical performance is attributed to the improved electrical conductivity and structural stability after composition of graphite sheets. The study demonstrates a new research strategy for improving sodium ion storage properties of MoS2.
Zinc selenide (ZnSe; mineral name: stilleite) and its nanostructured composite (ZnSe/C) are prepared by simple solid-state synthetic routes, and their potential as electrode materials for rechargeable Li-ion batteries is investigated. The reaction mechanism between ZnSe and Li is demonstrated using ex situ X-ray diffraction and extended X-ray absorption fine structure analyses. The X-ray diffraction patterns and high-resolution transmission electron microscopy observations confirm that ZnSe nanocrystallites in ZnSe/C are uniformly distributed within an amorphous carbon matrix. The nanostructured ZnSe/C composite electrode exhibit excellent electrochemical performances such as a high capacity and long cycling behavior of ca. 705 mAh g−1 over 300 cycles.
The fabrication of an ideal electrode architecture consisting of robust three dimensional (3D) nanowire networks have gained special interest for energy storage applications owing to the integrated advantages of nanostructures and microstructures. In this work, 3D MoO2 nanotextiles assembled from highly interconnected elongated nanowires are successfully prepared by a facile stirring assisted hydrothermal method and followed by an annealing process. In addition, a methylbenzene/water biphasic reaction system is involved in the hydrothermal process. When used as an anode material in Li ion batteries (LIBs), this robust MoO2 nanotextiles exhibit a high reversible capacity (860.4 mAh g−1 at 300 mA g−1), excellent cycling performance (89% capacity retention after 160 cycles) and rate capability (577 mAh g−1 at 2000 mA g−1). Various synthetic factors to the fabrication of 3D nanotextiles structure are discussed here and this design of 3D network structures may be extended to the preparation of other functional nanomaterials.
A photovoltaic (PV) system using multilevel boost converter (MBC) and line commutated inverter (LCI), operating in both grid-connected mode and stand-alone mode has been analysed. This proposed system extracts and feeds the maximum power to a single phase utility grid and stand-alone system simultaneously. The duty ratio of the MBC is estimated from the theoretical analysis of the proposed system, for extracting maximum power from PV array. The proposed system tracks the maximum power with the determined duty ratio which remains the same for all irradiations, for a fixed firing angle of LCI. The flexibility of supplying required proportion of extracted power to grid and stand-alone load and the elimination of a separate MPPT controller are the major benefits of the proposed system under normal grid conditions. In addition to it, the grid issues like voltage swell, blackout and brownout are considered and necessary remedial measures have been taken in the proposed system. Based on the issues, either the firing angle of LCI is adjusted or LCI is disconnected and replaced by a battery. Simulation studies have been carried out and the dynamic response of the system is observed. A laboratory prototype is built and experimental investigations have also been carried out. The theoretical analysis, simulation and experimental results are found to be closely associating with each other proving the efficacy of the proposed configuration.
A green chemistry approach (hydrothermal microwave irradiation) has been used to deposit manganese oxide on nickel foam-graphene. The 3D graphene was synthesized using nickel foam template by chemical vapor deposition (CVD) technique. Raman spectroscopy, X-ray diffraction (XRD), scanning electron and transmission electron microscopies (SEM and TEM) have been used to characterize structure and surface morphology of the composite, respectively. The Raman spectroscopy measurements on the samples reveal that 3D graphene consists of mostly few layers with low defect density. The composite was tested in a three electrode configuration for electrochemical capacitor, and exhibited a specific capacitance of 305Fg−1 at a current density of 1Ag−1 and showed excellent cycling stability. The obtained results demonstrate that microwave irradiation technique could be a promising approach to synthesis graphene based functional materials for electrochemical applications.
Composite electrodes (∼9 μm in thickness) composed of 5V-class electrode of LiNi0.5Mn1.5O4 (LNM) and high Li+ conductive crystalline-glass solid electrolyte (LATP, Ohara Inc.) were prepared at room temperature by aerosol deposition (AD) on platinum sheets. The resultant LNM-LATP composite electrodes were combined with LiPON and Li, and 5V-class bulk-type all-solid-state rechargeable lithium batteries (SSBs) were prepared. The crystallnity of the LNM in the LNM-LATP composite electrode was improved by annealing. Both thermogravimetry-mass spectroscopy analysis and XRD analysis clarified that the side reactions between the LNM and the LATP occurred over 500 °C with oxygen release. From these results, annealing temperature of the LNM-LATP composite electrode system was optimized at 500 °C due to the improved crystallinity of the LNM with avoiding the side-reactions. The SSBs with the composite electrodes (9 μm in thickness, 40 vol% of the LNM) annealed at 500 °C delivered 100 mAh g−1 at 10 μA cm−2 at 100 °C. Degradation of the discharge capacity with the repetition of the charge-discharge reactions was observed, which will originate from large volume change of the LNM (∼6.5%) during the reactions.
Publisher Summary Fire protection engineers interface with architectural engineering including locations of buildings, exposures to buildings, sizes of buildings and sizes of fire areas, building layout, combustibility of building finishing materials, and security issues. Areas of concern to fire protection engineers that interface with chemical engineering includes: materials hazards, materials storage, process hazards evaluation, and process utilities. Fire protection engineering interfaces with electrical engineering in the following areas: building system controls, fire detection and alarm systems, extinguishing system control, electric motor-driven fire pumps, emergency lighting, backup power supplies, electrical equipment for hazardous locations, and electrical protection systems. Fire protection systems that interface with the mechanical discipline include: piped fire protection systems, fire protection water supplies, pneumatic power and control systems, building HVAC systems, smoke control and smoke management systems, and area ventilation systems. Natural calamities like earthquakes, flood, cyclones, tornadoes, and hurricanes can damage fire protection systems. Building codes contain the structural design features for flood, earthquakes and wind, as well as for snow, ice, and other loads.
Calculations are made of the ionization potential (IP) and the oxidation potential (E ox) values of 108 organic molecules that are potential electrolyte additives for the overcharge protection of lithium-ion batteries (LIBs). The calculated E ox values are in close agreement with the experimental ones, where the root-mean-square deviation is 0.08V and the maximum deviation is 0.15V. The molecules exhibiting high E ox (>4.5V) show one of the following two features: (1) IP>7.70eV or (2) IP<7.70eV with a relatively large molecule size. Consideration of bulk solvent effects, in particular the electrostatic attraction between solute and solvent, is crucial in determining E ox. Considering its accuracy and reliability, the density functional calculation is recommended as a useful tool for screening electrolyte additives for LIBs.