Cathode Samples Research Articles

Effect of Titanium Cathode Surface Condition on Initial Copper Deposition during Electrolytic Fabrication of Copper Foil

Recent demands for cheaper and more compact devices require electronic devices to have more added in printed circuit boards. To meet these demands, smooth copper foils that enable finer copper wiring has need to be fabricated. For achieving such wiring, the effect that the initial deposition of copper on a titanium cathode has on the smoothness of the resultant foil and the effect of physical polishing and chemical etching of the cathode surface on the initial deposition of copper were investigated. The morphology of the titanium surface was modified by chemical etching using dilute sulfuric acid and by physical polishing with emery paper. We confirmed that the initial deposition of copper considerably affects the smoothness of the copper foil and that smooth foil can be obtained by the etching and polishing processes. In cathode samples where physical and chemical treatments were performed on the surface, the amount of deposition on the cathode was found to be high. We also confirmed the possibility of fabricating fine copper foil with minimal surface roughness. Irregularities with a depth of approximately 0.1 µm and line defects were observed on the surface of the treated titanium cathode, and the atomic ratio of metallic titanium on the surface by a factor of increased 3 to 4 as compared to those without treatment. The surface of titanium is covered by oxides and can be exposed by chemical etching and physical polishing. It is thought that the exposed areas of metallic titanium, which has a low electrical resistivity, act as nucleation points for the initial copper deposits and are useful for obtaining smooth copper foil through uniform copper deposition.

Thermal diffusivity study of aged Li-ion batteries using flash method

Advanced Li-ion batteries with high energy and power density are fast approaching compatibility with automotive demands. While the mechanism of operation of these batteries is well understood, the aging mechanisms are still under investigation. Investigation of aging mechanisms in Li-ion batteries becomes very challenging, as aging does not occur due to a single process, but because of multiple physical processes occurring at the same time in a cascading manner. As the current characterization techniques such as Raman spectroscopy, X-ray diffraction, and atomic force microscopy are used independent of each other they do not provide a comprehensive understanding of material degradation at different length (nm 2 to m 2) scales. Thus to relate the damage mechanisms of the cathode at mm length scale to micro/nanoscale, data at an intermediate length scale is needed. As such, we demonstrate here the use of thermal diffusivity analysis by flash method to bridge the gap between different length scales. In this paper we present the thermal diffusivity analysis of an unaged and aged cell. Thermal diffusivity analysis maps the damage to the cathode samples at millimeter scale lengths. Based on these maps we also propose a mechanism leading to the increase of the thermal diffusivity as the cells are aged.

Structural changes and thermal stability of charged LiNi 1/3Co 1/3Mn 1/3O 2 cathode material for Li-ion batteries studied by time-resolved XRD

Structural changes and their relationship with thermal stability of charged Li 0.33Ni 1/3Co 1/3Mn 1/3O 2 cathode samples have been studied using time-resolved X-ray diffraction (TR-XRD) in a wide temperature from 25 to 600 °C with and without the presence of electrolyte in comparison with Li 0.27Ni 0.8Co 0.15Al 0.05O 2 cathodes. Unique phase transition behavior during heating is found for the Li 0.33Ni 1/3Co 1/3Mn 1/3O 2 cathode samples: when no electrolyte is present, the initial layered structure changes first to a LiM 2O 4-type spinel, and then to a M 3O 4-type spinel and remains in this structure up to 600 °C. For the Li 0.33Ni 1/3Co 1/3Mn 1/3O 2 cathode sample with electrolyte, additional phase transition from the M 3O 4-type spinel to the MO-type rock salt phase takes place from about 400 to 441 °C together with the formation of metallic phase at about 460 °C. The major difference between this type of phase transitions and that for Li 0.27Ni 0.8Co 0.15Al 0.05O 2 in the presence of electrolyte is the delayed phase transition from the spinel-type to the rock salt-type phase by stretching the temperature range of spinel phases from about 20 to 140 °C. This unique behavior is considered as the key factor of the better thermal stability of the Li 1−xNi 1/3Co 1/3Mn 1/3O 2 cathode materials.

The thermal stability of fully charged and discharged LiCoO 2 cathode and graphite anode in nitrogen and air atmospheres

The thermogravimetric (TG) and differential thermal analysis (DTA) were used to investigate the thermal stability of fully charged and discharged LiCoO 2 cathode and graphite anode in nitrogen and air atmospheres. The results showed that the weight of charged and discharged LiCoO 2 cathode samples exhibited an obvious decrease between 100 and 120 °C in two atmospheres. The exothermic decomposition reaction of fully charged LiCoO 2 cathode occurred at 250 °C in two atmospheres. A small decomposition reaction of the discharged LiCoO 2 cathode occurred at 300 °C. When the temperature of samples was elevated to 600 °C, the weight of fully charged and discharged LiCoO 2 cathode in air atmosphere did not change; while the weight of samples in nitrogen atmosphere decreased. This was because the Co 3O 4 as the decomposition product of the cathodes could be reduced to CoO by the carbon black above 600 °C in N 2 atmosphere. The solid electrolyte interphase (SEI) film of fully charged and discharged graphite anode was decomposed at 100–120 °C in two atmospheres, and the weight loss of fully charged graphite anode at 100–120 °C was obviously less than that of the fully discharged graphite anode. When the samples were heated to 300 °C, there was no fierce exothermic reaction for the lithiated graphite anode in N 2 atmosphere, whereas an exothermic reaction in air atmosphere occurred rapidly.

Mammalian Proteasome Subpopulations with Distinct Molecular Compositions and Proteolytic Activities

The proteasome-dependent protein degradation participates in multiple essential cellular processes. Modulation of proteasomal activities may alter cardiac function and disease phenotypes. However, cardiovascular studies reported thus far have yielded conflicting results. We hypothesized that a contributing factor to the contradicting literature may be caused by existing proteasome heterogeneity in the myocardium. In this investigation, we provide the very first direct demonstration of distinct proteasome subpopulations in murine hearts. The cardiac proteasome subpopulations differ in their molecular compositions and proteolytic activities. Furthermore they were distinguished from proteasome subpopulations identified in murine livers. The study was facilitated by the development of novel protocols for in-solution isoelectric focusing of multiprotein complexes in a laminar flow that support an average resolution of 0.04 pH units. Utilizing these protocols, the majority of cardiac proteasome complexes displayed an isoelectric point of 5.26 with additional subpopulations focusing in the range from pH 5.10 to 5.33. In contrast, the majority of hepatic 20 S proteasomes had a pI of 5.05 and focused from pH 5.01 to 5.29. Importantly proteasome subpopulations degraded specific model peptides with different turnover rates. Among cardiac subpopulations, proteasomes with an approximate pI of 5.21 showed 40% higher trypsin-like activity than those with pI 5.28. Distinct proteasome assembly may be a contributing factor to variations in proteolytic activities because proteasomes with pI 5.21 contained 58% less of the inducible subunit beta 2i compared with those with pI 5.28. In addition, dephosphorylation of 20 S proteasomes demonstrated that besides molecular composition posttranslational modifications largely contribute to their pI values. These data suggest the possibility of mixed 20 S proteasome assembly, a departure from the currently hypothesized two subpopulations: constitutive and immuno forms. The identification of multiple distinct proteasome subpopulations in heart provides key mechanistic insights for achieving selective and targeted regulation of this essential protein degradation machinery. Thus, proteasome subpopulations may serve as novel therapeutic targets in the myocardium.

Effect of TiB2 Coating on Evolution of Cathode Lining during the Process of Primary Aluminum Production

A modified Rapoport apparatus for sodium expansion was used to determine the sodium expansion of TiB2-coated carbon cathode samples with different TiB2 contents. It was shown that TiB2 coating played a role in slowing the sodium penetration rate to the carbon cathode lining, which resulted in reduced swelling and cracking of carbon cathode block and then extended the life of aluminum reduction cells. The TiB2 coating was applied to the carbon cathode in 160 kA prebake cells, and the characteristic of evolution of carbon cathode was observed.

A technique coupling the analyte electrodeposition followed by in-situ stripping with electrothermal atomic absorption spectrometry for analysis of samples with high NaCl contents

A technique coupling the analyte electrodeposition followed by in-situ stripping with electrothermal atomic absorption spectrometry has been developed for determination of lead and cadmium in samples with high salt contents. To separate the analyte from the sample matrix, the analyte was in-situ quantitatively electrodeposited on a platinum sampling capillary serving as the cathode (sample volume, 20 μL). The spent electrolyte containing the sample matrix was then withdrawn, the capillary with the analyte deposited was washed with deionized water and the analyte was stripped into a chemically simple electrolyte (5 g/L NH 4H 2PO 4) by reversing the polarity of the electrodeposition circuit. Electrothermal atomization using a suitable optimized temperature program followed. A fully automated manifold was designed for this coupled technique and the appropriate control software was developed. The operating conditions for determination of Pb and Cd in samples with high contents of inorganic salts were optimized, the determination was characterized by principal analytical parameters and its applicability was verified on analyses of urine reference samples. The absolute limits of detection for lead and cadmium (3 σ criterion) in a sample containing 30 g/L NaCl were 8.5 pg and 2.3 pg, respectively (peak absorbance) and the RSD values amounted to 1.6% and 1.9% for lead (at the 40 ng mL − 1 level) and cadmium (at the 4.0 ng mL − 1 level), respectively. These values (and also the measuring sensitivity) are superior to the results attained in conventional electrothermal atomic absorption spectrometric determination of Pb and Cd in pure solutions (5 g/L NH 4H 2PO 4). The sensitivity of the Pb and Cd determination is not affected by the NaCl concentration up to a value of 100 g/L, demonstrating an efficient matrix removal during the electrodeposition step.

Coarsening of Pt Nanoparticles in Proton Exchange Membrane Fuel Cells upon Potential Cycling

Two different Pt/C samples (Pt/Vulcan and Pt/C-high-surface- area) were subject to potential cycling between 0.6V and 1.0V vs. reversible hydrogen electrode, where significant platinum area loss was found. Both cycled MEA cathode samples were examined and compared in detail by glancing angle X-ray powder Diffraction and transmission electron microscopy (TEM) to reveal processes responsible for observed platinum loss. TEM data and analyses of pristine and cycled Pt/C catalyst and cross-sectional MEA cathode samples unambiguously confirmed that coarsening of platinum particles occurred via two different processes as reported recently1: i) Ostwald ripening on carbon at the nanometer- scale; and ii) diffusion of soluble platinum species in the ionomer phase at the micrometer-scale, chemical reduction of these species by cross-over H2 molecules and precipitation of platinum particles in the cathode ionomer phase.

Fuel Cell Catalyst Particle Size Growth Characterized by X-Ray Scattering Methods

X-ray diffraction experiments coupled with whole profile pattern refinement and Warren Averbach data analysis methods were used to quantify Pt electrode crystallite growth in polymer membrane fuel cell cathode samples. Both X-ray data analysis methods produced similar results for average particle sizes. The cycling of cathodes to cell potentials above 1 volt greatly increases the loss of Pt cathode surface area by Pt grain growth. The fuel cell anode catalysts exhibit little to no growth after potential cycling experiments. Changes in Pt to carbon peak integrated intensity ratios indicate carbon corrosion is occurring upon cycling to high potentials.

Contribution of the Structural Changes of LiNi0.8Co0.15Al0.05O2 Cathodes on the Exothermic Reactions in Li-Ion Cells

The exothermic reaction mechanism of the delithiated cathode in the presence of an electrolyte has been investigated. The contributions of the delithiated cathode and electrolyte to the overall thermal runaway mechanism were evaluated using an accelerating rate calorimeter and differential scanning calorimeter (DSC). The cathode was also chemically delithiated to evaluate the influence of each component of the composite cathode as well as the structural changes during the exothermic reaction. Thermogravimetric analysis results confirmed that delithiated lost its weight at elevated temperatures, varying with the state of charge. The X-ray diffraction and DSC studies show that the exothermic reaction of the delithiated cathode sample started very close to the onset temperature of the structural change in the delithiated cathode as detected by the X-ray powder diffraction. Based on the results of this study, a reaction mechanism leading to the thermal runaway of the delithiated cathode is also proposed.

Study on Electrochemical Performance of Fluorinated Graphite and Its Application in Alkaline Batteries

The electrochemical characteristics and performance of fluorinated graphites (FGs) and its application in conventional alkaline batteries were investigated. FG as a cathode additive in alkaline batteries can improve the discharge performance significantly. The discharge performances of alkaline batteries in which the cathode contained a different weight percentage of FG and those with a fixed weight percent of FG with different fluorine contents were measured. The storage stability of cells with various test cathodes was determined. XRD studies were carried out on different graphites, on FG, and on various types of cathode samples before and after discharge.

Study of respective roles of anodic and cathodic reactions in acoustic emission recorded during crevice corrosion of 304L austenitic stainless steel

The contributions of anodic and cathodic reactions to the acoustic emission recorded during crevice corrosion of 304L austenitic stainless steel have been investigated. During the experiments, crevice propagation was localised on an anodic sample, whereas the cathodic reactions were isolated on a separate specimen. The application of shot-peening to the anodic and/or cathodic sample surfaces allowed control over the distribution of anodic and cathodic reactions on both specimens. The shot-peening treatment led to an increased crevice propagation rate, due to an increase in the cathodic current density. It has been established that the most energetic acoustic emissions originate from cathodic reactions, whereas anodic processes are associated with more numerous but shorter AE signals. During crevice development, the cathodic reactions begin with the reduction of O2 and/or H2O2 on the cathodic specimen, but later involve H+ reduction in the so-called 'anodic' confined area. The involvement of proton reduction within the crevice as a driving force for crevice propagation has been confirmed by analysis of the acoustic emission data.

Instability of Pt ∕ C Electrocatalysts in Proton Exchange Membrane Fuel Cells: A Mechanistic Investigation

Equilibrium concentrations of dissolved platinum species from a electrocatalyst sample in 0.5 M at 80°C were found to increase with applied potential from 0.9 to 1.1 V vs reversible hydrogen electrode. In addition, platinum surface area loss for a short-stack of proton exchange membrane fuel cells (PEMFCs) operated at open-circuit voltage was shown to be higher than another operated under load . Both findings suggest that the formation of soluble platinum species (such as ) plays an important role in platinum surface loss in PEMFC electrodes. As accelerated platinum surface area loss in the cathode (from 63 to in ) was observed upon potential cycling, a cycled membrane electrode assembly (MEA) cathode was examined in detail by incidence angle X-ray diffraction and transmission electron microscopy (TEM) to reveal processes responsible for observed platinum loss. In this study, TEM data and analyses of catalyst and cross-sectional MEA cathode samples unambiguously confirmed that coarsening of platinum particles occurred via two different processes: (i) Ostwald ripening on carbon at the nanometer scale, which is responsible for platinum particle coarsening from to on carbon, and (ii) migration of soluble platinum species in the ionomer phase at the micrometer scale, chemical reduction of these species by crossover molecules, and precipitation of platinum particles in the cathode ionomer phase, which reduces the weight of platinum on carbon. It was estimated that each process contributed to of the overall platinum area loss of the potential cycled electrode.

Cathode units with a carbon fiber field emitter

We have developed a carbon fiber field emitter (CFFE) with a diameter of 7 μm and a bullet shape at the top. We found that a micro-pit on the top of the fiber can focus the emitted electron beam, so that the beam is inside a small solid angle around the axis of symmetry. Our investigations show that due to this effect the fiber emitter with optimized dimensions of the micro-pit has good emission stability, good reproducibility for different cathode samples and high electron optical brightness. The CFFE with micro-pit on the top has been successfully used for 14 years in the “Cwikscan-50A” electron microscope instead of the conventional tungsten field emitter.

Low jitter metal vapor vacuum arc ion source for electron beam ion trap injections

We describe a metal vapor vacuum arc (MeVVA) ion source containing eight different cathodes that are individually selectable via the control electronics which does not require moving components in vacuum. Inside the vacuum assembly, the arc plasma is produced by means of a 30μs pulse (26kV,125A) delivering 2.4mC of charge to the cathode sample material. The trigger jitter is minimized (<200ns) to improve the capture efficiency of the ions which are injected into an ion trap. During a single discharge, the over-damped pulse produces an ion flux of 8.4×109ions∕cm2, measured by an unbiased Faraday cup positioned 20cm from the extractor grid, at discharge rates up to 5Hz. The electronic triggering of the discharge is via a fiber optic interface. We present the design, fabrication details, and performance of this MeVVA, recently installed on the National Institute of Standards and Technology electron beam ion trap (EBIT).

Preparation of Mg–Li–Al–Zn Master Alloy in Air by Electrolytic Diffusing Method

Electrolytic diffusing method was conducted at 500°C to prepare Mg–Li–Al–Zn master alloy in air. It was also explored for the melting and casting of Mg–Li alloy in air, as the Mg–Li–Al–Zn master alloy used as raw material. A mixture of 45 mass% lithium chloride (LiCl) and 55 mass% potassium chloride (KCl) was employed as the electrolyte. Mg–9 mass%Al–1 mass% Zn (AZ91) alloy was used as cathode material while graphite selected as anode. Experimental results showed that the electrolysis current linearly depended on the applied working voltage. Deposition of lithium occurred on the cathode surface. After the electrolysis experiments, Mg–12 mass% Li–9 mass% Al–1 mass% Zn alloy sheet can be obtained. At working voltage of 4.2 V and one hour electrolysis, the hexagonal-closed-pack AZ91D sheet (1.5-mm thickness) was fully converted to body-centered-cubic Mg–Li–Al–Zn alloy. The formation of Mg–Li phase during electrolysis was studied by inductively coupled plasma-atomic emission spectrometer (ICP), X-ray diffraction, and optical microscopy. It is diffusion rather than deposition rate (electrolysis current) that controlled the depth of Mg–Li phase formed in the cathode sample. The Mg–Li–Al–Zn alloy used as master alloys could be melted and casted in air without ignition. However, the content of lithium in the as-cast block was reduced to 3.77 mass%, properly due to oxidation of lithium metal during melting.

Field emission measurement techniques for the optimisation of carbon nanotube cathodes

We have developed advanced measurement techniques for the investigation of the field emission (FE) properties of high-technology materials. Flat samples up to 30 mm in diameter can be optimised either for strong or weak electron emission, i.e., cold FE cathodes operating at field levels below 10 V/μm or high-voltage vacuum devices preventing FE up to 200 V/μm. The integral measurement system with luminescent screen (IMLS) provides a quick overview of the microscopic distribution and long- and short-term stability of the emission current, and facilitates a controlled conditioning of cold cathode samples at various pressures. The field emission scanning microscope (FESM) is incorporated within a UHV surface analysis system and enables high-resolution emitter distributions and local FE investigations down to the nanoscale. Exemplary results on carbon nanotube samples will be given to demonstrate that the combination of both instruments yields a very effective means for an improved understanding and tailoring of materials for cold cathode applications.

Multi-component material sputtering by hollow cathode discharge

The investigation of Bi1.8Pb0.4Sr2Ca2.2Cu3.2O10-y material sputtering in hollow cathode discharge is presented. The ICP-OES analysis is used for quantitative analysis of the cathode sample and the deposit on a substrate, situated in front to the cathode hole. We suggest using spectral coefficients, which connect the relative spectral intensity with the relative concentration of the deposited elements. These coefficients, once obtained, are typical for every element in the multi-component material and for its chosen spectral line. The above-mentioned spectral coefficients can be used for relative concentration obtaining and for “in-situ” concentration, control during the sputtering of this kind of ceramics.

Calculation of cathode heating in analytical glow discharges

The temperature of the cathode (sample) in analytical glow discharges is calculated as a function of depth in the sample, by means of a one-dimensional heat conduction equation. The energy input is determined by the energetic ions and atoms bombarding the cathode. Calculations are performed for a Cu sample, under various conditions, ranging from perfect cooling from the backside, to the limit of no cooling. The effect of the discharge conditions (voltage–pressure–current) is also investigated. Finally, simulations are carried out for various cathode materials. It is found that the efficiency of cooling has a very important effect on the cathode surface temperature. Moreover, different cathode materials can give rise to great differences in the cathode surface temperature for the same power input, due to a different thermal conductivity.

A simple glow discharge ion source for direct solid analysis by on-axis time-of-flight mass spectrometry

A simple and small-sized direct current glow discharge (dc-GD) ion source has been designed and constructed for direct analysis of solid samples. The glow discharge (about 100 mm3 of internal volume) was coupled to a commercial on-axis time-of-flight mass spectrometer (TOFMS) for fast simultaneous multielement-selective detection. The commercial TOFMS used was originally coupled to an inductively coupled plasma (ICP) ion source. Therefore, the GD source presented in this study was designed aiming at being easily exchanged with the ICP source of a commercial ICP-TOFMS instrument (LECO Corporation). The distance between the cathode (sample) and the sampler cone was kept at about 4 mm.The proposed source is able to analyse planar conducting samples of different sizes with good long-term stability (better than ±5% when isotope ratioing techniques were applied). The spectral mass resolving power was about 1520 (at mass 120 u).Finally, the expected benefits of the fast simultaneous multielemental capabilities of TOFMS detection to carry out direct depth profile analysis of solid samples are demonstrated and discussed.