Multicomponent Cathode Research Articles

Structural Transformations on the Surface of Al-Ti Cathodes Subjected to Vacuum Arc Heating

AlTiN nitride coatings on the surfaces of metal-working tools can greatly extend their service life. The coatings are deposited from plasma flows generated by vacuum arc burning on the cathode surface. The elemental and charge composition of the plasma flows, as well as the content of metal drops, depend on the cathode’s structure. In this paper, the microstructure, elemental, and phase compositions of the surface layer of Al-Ti cathodes subjected to vacuum arc heating were studied. These cathodes had similar elemental compositions (Ti + 50 at.% Al) but differed from one another in their phase composition and microstructure (grain size, porosity). The cathodes were studied by X-ray diffraction analysis, scanning electron microscopy, and electron probe analysis. It was found that during vacuum arc heating, surface fusion or thermal cracking of the cathode’s surface layer occurs. The thickness, structure, and phase composition of the modified layer were controlled by the thermal conductivity of the cathode material, which, in turn, depended on the phase composition and porosity of the cathodes. The maximum thickness of the modified layer (up to 400 µm) was observed on the surface of the sintered cathode due to the lower thermal conductivity of the porous structure of the cathode. The obtained results can be used for the development of coating deposition technology based on vacuum arc sputtering of multicomponent cathodes.

Formation of multi-component coatings of specified composition and required thickness by magnetron sputtering

The paper considers the possibility of obtaining multicomponent coatings of a given composition and required thickness by magnetron sputtering on the basis of controlling the stoichiometry of the target cathode used. A toolkit for preliminary estimation of thickness and stoichiometry of multicomponent coatings synthesized by magnetron sputtering taking into account condensation rate and concentration of components of the sputtered multicomponent cathode-target is proposed. A series of experiments on the formation of coatings based on titanium TiAlSiN and TiAlMoN by magnetron sputtering on the NNV 6.6-I1 unit using multicomponent cathodes obtained by spark plasma sintering was carried out, the results of which showed the coincidence of calculated and experimental values of the percentage content of elements and thickness of multicomponent coatings by more than 80 %.

Non-standard state thermodynamics of metal electrodeposition

The development of new high temperature electrolytes is hindered by lack of information about their thermodynamic solution properties, which must be determined through experiments or modeling. Current models, however, are unable to accurately predict the behavior of the complex multicomponent liquids that make up such electrolytes, and gathering sufficient experimental data for a full analysis is lengthy and expensive. Even if the properties of an electrolyte are well-determined, the link between their thermodynamics and the extent of codeposition that will occur during electrolysis remains unclear. Previous endeavors aimed at linking the difference in deposition potential ΔE of two elements to their codeposition behavior focused on binary cathode alloys that formed ideal solutions. Herein, this approach is generalized to multicomponent cathodes exhibiting real solution (ai≠xi) behavior. Through this methodology, targeted experimental data and classical Gibbs energy curves can be used in combination to map out the thermodynamic nature of complex electrolytes. To facilitate this effort, a new thermodynamic reference state for activity is derived that allows one to determine electrolyte activities directly from ΔE. The merits of this approach are tested against experimental case studies and compared to traditional standard state assumptions.

Ion Beam Generation in a Vacuum Arc Ion Source with a Multicomponent Cathode

Vacuum arc ion sources are widely used for modifying the properties of various surfaces using ion implantation. The use of cathodes consisting of multicomponent compounds in these sources makes it possible to obtain beams of complex compositions, which expands their technological capabilities. An ion beam generated in a vacuum arc ion source with a two-component cathode made of a copper-chromium composite is studied under the conditions of a magnetic field applied to the discharge gap. It is shown that the charge state distribution of copper and chromium ions in the beam depends on their ratio in the cathode material, and the fractions of these ions in the beam correspond to their atomic content in the cathode. It is shown that the ratio of copper and chromium ions in the plasma, and, accordingly, in the ion beam, is independent of the magnetic field and corresponds to their atomic ratio in the cathode.

Исследование генерации ионных пучков в вакуумном дуговом ионном источнике с многокомпонентным катодом

Исследование генерации ионных пучков в вакуумном дуговом ионном источнике с многокомпонентным катодом

(Invited) High-Throughput Synthesis, Evaluation, Analysis, and Data Visualization Technology for Exploring Multi-Components Functional Oxides Powder

In the sessions of Materials Genome Initiative (MGI) and Materials Informatics (MI) at recent international and domestic conferences, majority of research presentations are on material prediction using a combination of computational chemistry and machine learning. On the other hand, the contents incorporating high-throughput synthesis and evaluation experiments are only occasionally seen. It is also true that the number of samples that can be handled per hour is small compared to the former data science.However, if a series of experimental processes linked to synthesis, evaluation, and analysis is made user-friendly and high-throughput, it is possible to efficiently generate multi-condition and multi-component data in a unified experimental environment such as starting materials. As a result, even when creating a data set by extracting text from a paper, the data shortage can be supplemented with experimental data.Unlike thin films and polymers, powder synthesis is a heterogeneous reaction that requires the use of a wet process to perform high-throughput experiments. We have hitherto developed powder synthesis apparatus equipped with a micropump for solution dispensing, and high-throughput exploration system for powder and thin-film library based on electrostatic spray deposition consisted by combining multiple syringe pumps and a high-voltage power supply. By using these system, we have been exploring multi-component cathode materials for lithium ion battery and thermoelectric materials. In addition, recently, high-throughput experiments in a high-pressure environment of 200 MPa and 500ºC are possible.If the time required for physical property evaluation and data analysis is the same as before, even if only the synthesis based on experiments becomes high throughput, the attractiveness of MI will be weakened. Therefore, it is necessary to continue to develop jigs and software for efficient evaluation and analysis of huge libraries obtained in high-throughput experiments.In this presentation, we will introduce the exploration for A-site and B-site substitutes of perovskite-type CaMnO3, which is expected as an n-type thermoelectric material. In the preliminary search, it was confirmed that Ca1-x Bi x Mn1-y Ni y O3 contributes to the improvement of thermoelectric power by substituting elements at each site. As the next step, the amount of Bi substitution was determined to be within 10% from the combination of high-throughput synthesis and high-throughput Seebeck coefficient measurement. Synchrotron XRD and XAFS measurements were used to investigate the correlation between physical properties and crystal structure. We have succeeded in collecting data without filling the capillaries and making pellets by developing special tools. Synchrotron XRD and XAFS measurements were used to investigate the correlation between physical properties and crystal structure. We have succeeded in collecting data without filling the capillaries and making pellets by developing special tools. We also developed software that automates Rietveld analysis, although we need basic knowledge to set up an initial structural model. As a result, we have made it easier to generate data sets for visualizing crystallographic data and physical property data at once. In the obtained Bi-substituted CaMnO3 powder, when Bi was 8% or less, the conductivity and power factor increased due to the increase in carrier concentration. At Bi8% and higher, PF reaches its limit value, which involves a large change in the MnO6 octahedral plane bond distances Mn-O1 (1) and Mn-O1 (2), that is, a significant increase in octahedral distortion. High-throughput experiments including the collection of crystallographic information through the development of these technologies are expected to be an effective tool for future machine learning.

A novel facile synthesis of hollow multi-component Li1.4Mn0.6Co0.2Ni0.2O2+δ spheres via controlling the porosity of precursor

The self-sacrificial template approach based on Kirkendall effect in crystal growth has been widely employed in fabrication of hollow inorganic micro/nanostructures in recent years. Nevertheless, almost all reported works so far are limited only to unitary or binary template methods to achieve hollow multi-component materials. In this work, we describe a new ternary self-template method to fabricate hollow multi-component Li1.4Mn0.6Co0.2Ni0.2O2+δ (LMCN) micro/nano-spheres, which further simplifies the synthetic process and facilitates the homogenization of all metal elements to improve the performance. By a facile process of adjusting the values of NH4HCO3 precipitant to prepare spherical carbonate precursor, metal oxides with different porous can be developed after the heat treatment of the precursor. It is proved that the metal oxide with more porosity is beneficial for the formation of hollow structured multi-component cathode material treated at the same temperature. When tested in lithium-ion batteries, the hollow structured LMCN exhibits outstanding electrochemical performance comprising prominent rate capabilities (151.3 mAh g−1 at a high rate of 10 C) and greatly prolonged cyclic lifespan (87.8% of capacity retention over 200 cycles at 2 C) in contrast to solid counterpart. The excellent performance can be attributed to the hierarchical macro/nano-porous hollow structures, which are controllably synthesized by easily adjusting the values of NH4HCO3 precipitant based on the ternary self-template method.

Empowering multicomponent cathode materials for sodium ion batteries by exploring three-dimensional compositional heterogeneities

Three-dimensional compositional heterogeneities can yield stable sodium layered oxide cathode materials.

On plasma jet formation in vacuum arc with composite cathode

This paper deals with the computer modeling of vacuum arc with composite multicomponent cathode. This arc is typical for certain kind of ion sources, plasma generator and vacuum interrupters. The described hybrid model treats the electrons as an inertialess fluid and ions as macroparticles. The macroparticle dynamic is calculated with the use of particle-incell method. Ion-ion Coulomb collision is considered with the use of Monte Carlo method. The model can simulate vacuum arc as a whole including separate cathode plasma jets, mixing zone, and common plasma column. The dependence of ion angular current distribution on the cathode composition reproduced with the help of developed model agrees well with experimental results.

Charge state, angular distribution, and kinetic energy of ions from multicomponent-cathodes in vacuum arc devices

We present research results on vacuum arc plasma produced with multicomponent cathode made of several different elements. The ion mass-to-charge-state spectra of the plasmas were studied by time-of-flight spectrometry. The angular distributions of different ion species were measured, and the kinetic energy of their directed (streaming) motion was determined. It is shown that the fractional composition of ions of different cathode components in the plasma flow from the cathode spot closely matches the fractional content of these components in the composite cathode. The charge states of ions of the various cathode components are determined by the average electron temperature in the cathode spot plasma. The angular distribution of lower mass ions in the plasma from a multicomponent cathode is less isotropic and broader than for the plasma from a single-component cathode of the same light element. The directed kinetic energies of the ions of the different components for plasma from a multicomponent cathode are lower for lighter elements and greater for heavier elements compared to the ion directed energy for plasmas from single-component cathodes made of the same materials. The physical processes responsible for these changes in the ion charge states in multicomponent-cathode vacuum arc plasma are discussed.

Producing multicomponent SHS-compacted cathodes based on refractory titanium compounds for vacuum-arc coatings

The technological features of and a device for manufacturing multicomponent cathodes of arc evaporators using SHS compaction are considered. Physically, an SHS-compacted cathode is a four-layer function-gradient product and consists of a metallic base in the form of a water-cooled bottom part of a regular cathode, an evaporating operating layer, an intermediate layer, and the SHS solder layer required for joining the synthesized material with the base. Compositions and weight characteristics of layers that allow us to produce defect-free multicomponent SHS-compacted cathodes based on stainless steel are presented.

A stationary multi-component cathode modeling and ion trajectories for an inertial electrostatic confinement fusion device

A new cathode modeling with stationary multi-component cathode approach is suggested for an inertial electrostatic confinement fusion device and some preliminary simulation studies based on the potential function of this cathode have been presented. The ions are accelerated due to the Coulomb force on a 2D plane and the central grid is assumed to have 6 point-wise and negatively charged at the middle. The model includes a repulsive force that stems from the screening effect of atoms at the vicinity of cathode. The simulations have proven that the particle trajectories are highly complex in the new potential well; in fact, the prediction of the particle route is observed to be strictly dependent on the control parameters such as the grid radius, ion current, voltage and initial position of the ion. Copyright © 2010 John Wiley & Sons, Ltd.

Hydrogen production in a microbial electrolysis cell with nickel-based gas diffusion cathodes

Gas diffusion cathodes with Ni alloy and Ni catalysts manufactured by chemical deposition were tested for H 2 production in a microbial electrolysis cell (MEC). In a continuous flow MEC, multi-component cathodes containing Ni, Mo, Cr, and Fe, at a total catalyst load of 1 mg cm −2 on carbon support demonstrated stable H 2 production at rates of 2.8 – 3.7 L L R − 1 d − 1 with only 5% methane in the gas stream. Furthermore, a Ni-only gas diffusion cathode, with a Ni load of 0.6 mg cm −2, demonstrated a H 2 production rate of 4.1 L L R − 1 d − 1 . Overall, H 2 production was found to be proportional to the Ni load implying that inexpensive gas diffusion cathodes prepared by chemical deposition of Ni can be successfully used for continuous production of H 2 in a MEC.

Structural and phase transformations in Ni3Fe during high-dose ion implantation

The results are given for experimental studies of the structural-phase state formed in the surface and nearsurface layers of a disordered polycrystalline Ni3Fe alloy during high-dose ion implantation. The studies used Auger electron spectroscopy, transmission electron microscopy, x-ray structural analysis, and microhardness measurements. The ion implantation was done using the “Raduga” vacuum arc source with a multicomponent cathode of composition Zr (89.5 wt. %)+C+N+O with an acceleration voltage of 50 kV. The implanted ion dose was varied in the range (6.0·1016–6.0·1017) ions/cm2. It was established that in the surface layer which is alloyed during ion implantation there is amorphization with simulataneous formation of finely dispersed ZrO2 particles whose dimensions increase with increasing implanted ion dose; this is accompanied by an increased internal mechanical stress. Beyond the ion-implanted layer a sublayer about 10 μm thick with a high dislocation density is formed (the “long-range action” effect). The results of microhardness measurements correlate with the data from structural studies.

Growth and characterization of cathodic arc evaporated CrN, (TiAl)N and (TiZr)N films

Nitride films have been grown using newly developed chromium, titanium-aluminum and titanium-zirconium targets by the cathodic arc evaporation process. Special alloy processing produced cathodes that overcame conventional problems associated with evaporation of multicomponent cathodes. Single and multilayer films of the various nitride compositions were analysed using X-ray photoelectron spectroscopy (XPS) and their electrochemical polarization behaviour was tested using polarization corrosion methods. From the XPS data, it was determined that the atomic ratio of the metallic constituents in the alloy cathodes was unity and the ratio of the cations to the anions in the nitride films was also unity. The Ti 2p, Al 2p and Zr 3d binding energies from the nitride films were 0.8–1.0 eV higher than in the corresponding target material. The XPS results strongly suggest that the (TiAl)N films are made up of distinct TiN and AlN phases and the (TiZr)N films of similarly distinct TiN and ZrN phases. In addition, electrochemical studies showed that the rest potential and polarization behaviour of the nitride films were influenced by the composition and integrity of the surface film.