Thin Zr films were deposited using a vacuum arc with a refractory graphite anode and a water-cooled Zr cathode. The deposition rate was obtained from the film thickness, measured by profilometry, and time of exposure to the arc plasma. The deposition rate increased with the arc current, gap distance, and arcing time before substrate exposure to Zr plasma. The measured deposition rate reached $0.9 ~\mu \text{m}$ /min for an arc current of 225 A for time before substrate exposure of 90 s and the rate tends to about $1 ~\mu \text{m}$ /min with further this time.

Thin films were deposited using a vacuum arc with a refractory anode. The arc was sustained between a water cooled Zr cathode and a graphite anode. Both electrodes with diameter 32 mm and 30 mm length, with a gap of 10 mm between them. The distance from the arc axis to the substrate was 110 mm. The arc was operated either 40 or 60 s before a glass substrate was exposed to the plasma for 15 s. The film thickness was measured by profilometry. The deposition rate was obtained from the film thickness and exposition time. The visual radiation emitted by the plasma plume was photographed with a digital camera. The highest measured deposition rate was 0.71 μm/min, for an arc current of 225 A and time before exposure of 60 s.

The work reports on the interaction of the photo electrodes with the electrolytes and dyes since it is imperative to investigate the degradation behavior of the transparent conducting electrodes in terms of structural, optical and electrical properties along with the corrosion resistance behavior. Three electrodes, one indium tin oxide (ITO) and two aluminium doped zinc oxide (AZO), two dyes (Eosin Yellow and Ruthenium Red), and two electrolytes, potassium iodide (KI) and lithium iodide (LiI) were used in this investigation. Twelve solar cells were fabricated with the aforementioned combination of electrodes, dyes and electrolytes. Open circuit voltage (V-oc) of the fabricated cells as a function of time (for 30 days) were recorded. Changes in the structure and elemental composition of the electrodes after interaction with the dye and electrolyte were analyzed using X-Ray Diffraction and EDX, respectively. Transparency and sheet resistance of the electrodes before and after interaction with electrolytes and dyes was observed. Corrosion behavior of the three electrodes was studied using an electrochemical analyzer with KI and LiI electrolytes.

Thin film deposition using hot anode vacuum arcs developed in the last decade is described. Two configurations were used: (i) with an open gap—the hot refractory anode vacuum arc (HRAVA) and (ii) with a closed gap—the vacuum arc with black body assembly (VABBA). In both configurations, the anode was heated by the arc with current I = 145–340 A, and a relatively dense plasma plume of cathode material (Cu, Ti, Cr, Al, Sn, Mo, Nb), was formed by re-evaporation of cathode material from the hot (2000–2500 K) anode, which was fabricated from graphite, Mo, Ta, or W. A steady state mode was reached when the anode was sufficiently hot and a plasma plume expanded, either radially (HRAVA) or directly from the front hot anode surface. As an example, the deposition rate measured in 300 A HRAVAs at distances of 80 mm from the arc axis, to be 3.6; 1.4 and 1.8 μm/min for Cu, Cr and Ti cathodes respectively. Interconnector trenches (100 nm wide ×300 nm deep) on microelectronic wafers were filled using a Cu HRAVA at a rate of 0.5 µm/min.

The hot refractory anode vacuum arc (HRAVA) plasma source was previously developed with a consumed cathode and a refractory anode to reduce the macroparticle (MP) contamination in vacuum arc deposited films. The HRAVA had open cylindrical electrodes and demonstrated that it not only reduced MP sizes and numbers but also converted MP material to plasma, and thus increased the deposition rate. This paper presents a new HRAVA configuration with a double arc between a common water-cooled Cu cathode with two active surfaces and two refractory graphite or tungsten anodes, with the aim of depositing film over a wider area. The arc current in each of the two arcs was 125 A for graphite and 150 A for tungsten. The radially expanding plasma plumes from each of the cathode-anode gaps merged, forming a wider common plasma. Cu films were deposited and over a 150 mm length parallel to the arc axis, while the corresponding length from a single-HRAVA source was only 75 mm.

Vacuum arcs are used as metallic plasma sources to deposit thin films, but conventional arcs also produce macroparticles (MPs) which degrade film quality. To reduce the MPs, the Hot Refractory Anode Vacuum Arc (HRAVA) plasma source was developed with a consumed cathode, which supplies the coating material, and a refractory anode. To obtain a wider deposition area, this work presents a new configuration with a double-arc between a common cathode and two refractory anodes. Experiments were conducted using two anodes from graphite or tungsten and a water-cooled consumable Cu cathode with two active surfaces. Cu film depositions were obtained over a length of 150 mm, in contrast to the deposition from a single BRAVA that produced a deposition length of 75 mm.

The electric force on ions in plasma and the momentum flux carried by the mixed ion-neutral flow were measured and found to be equal. The experiment was performed in a direct-current gas discharge of cylindrical geometry with applied radial electric field and axial magnetic field. The unmagnetized plasma ions, neutralized by magnetized electrons, were accelerated radially outward transferring part of the gained momentum to neutrals. Measurements were taken for various argon gas flow rates between 13 and 100 Standard Cubic Centimeter per Minute, for a discharge current of 1.9 A and a magnetic field intensity of 136 G. The plasma density, electron temperature, and plasma potential were measured at various locations along the flow. These measurements were used to determine the local electric force on the ions. The total electric force on the plasma ions was then determined by integrating radially the local electric force. In parallel, the momentum flux of the mixed ion-neutral flow was determined by measuring the force exerted by the flow on a balance force meter (BFM). The maximal plasma density was between 6 × 1010 cm−3 and 5 × 1011 cm−3, the maximal electron temperature was between 8 eV and 25 eV, and the deduced maximal electric field was between 2200 V/m and 5800 V/m. The force exerted by the mixed ion-neutral flow on the BFM agreed with the total electric force on the plasma ions. This agreement showed that it is the electric force on the plasma ions that is the source of the momentum acquired by the mixed ion-neutral flow.

ZrO2-Al2O3 coatings were deposited on a floating substrate at a temperature of 370°C. Various coating compositions, ranging from pure zirconia to 50at.% alumina content, were deposited by reactive pulsed-DC magnetron sputtering using 51mm diameter Zr and Al targets. The coating had a Zr-Al-O solid solution structure that was composed of nano-size cubic-ZrO2 grains (20±5nm) with aluminum cations distributed inside them. The deposited coatings were annealed up to 1350°C and their structural changes were studied using Differential Scanning Calorimetry (DSC), X-ray diffraction (XRD), High Resolution Transmission Electron Microscopy (HRTEM) and Vickers hardness measurement. Two exothermic annealing events were observed. The first event appeared at 700–750°C and was contributed to aluminum segregation to the grain boundaries, and the formation of a nanocomposite-ZrO2/amorphous-Al2O3 structure. The second event appeared at 1000–1200°C and was related to coarsening (“Ostwald ripening”) of the ZrO2 grains. The coating hardness after the first event was stabilized to 19.5±1.1GPa because of the segregation, which hindered grain growth. However, after a second DSC cycle of the coating, only one sharp endothermic transformation peak was observed at onset temperature of 1060±5°C. This was associated with grain growth accompanied with zirconia transformation from the cubic to the monoclinic phase.

The anode in a vacuum arc with a blackbody assembly was measured as a function of time. A 30-mm-diameter Cu cathode and a hollow Ta anode, 50 mm in diameter, were used for a plasma cavity. Cu plasma was ejected through an array of 250 holes of 0.6 mm diameter in the anode. The arc currents were I = 175, 200, and 225 A and the arc duration was 160 s. The anode temperature was measured using high-te...

Pulsed submerged arc (SA) treatment of aqueous methylene blue (MB) solutions was studied in the reactor with multiple mobile iron (Fe) based electrodes. The discharges were carried out between these electrodes, which are repetitively brought into collision contact with fixed electrodes, connected to the power supply. The new reactor allows electrical discharges and MB decomposition in a large (600ml) volume of liquid. The effects of alternating filtration, electrode type, arcing energy, vibration, aging of the solutions after arcing and the added H2O2 concentration on MB decomposition were studied. The ratio between the number of milliliters of the treated solution that reached complete removal of MB to the time required for this is greater by factor of 7.5 than this ratio for two electrode system obtained for the same SA conditions. The treatment efficiency in multi electrode reactor is explained by the numerous collisions of multiple electrodes leading to the formation of eroded nano-particles with the surface catalytically active towards MB oxidation.

Anode temperature in a Vacuum Arc with a Black Body Assembly (VABBA) was measured as a function of time. The arc was ignited in an electrode assembly operated as a black body for the macroparticles (MPs). The cathode was a 30 mm diameter Cu rod and the refractory anode was 50 mm in diameter, and constructed from Ta. Plasma was ejected through an array of 250 holes of 0.6 mm diameter in the anode. The arc currents were I=175 & 225 A and the arc duration was 180 s. The anode temperature was measured using high-temperature thermocouples at two points (TC-top, TC-side) inside the anode body. The observed anode temperature increased sharply during a transient time of ∼90 s and then it slightly increased with time up to 180 s reaching at TC-top 1650K (I=175 A) and 1850K (I=225 A). The anode temperature at the top surface exceeded that at side surface by ∼150–200C.

The ZrO 2 -Al 2 O 3 coatings were deposited at various coating compositions, ranging from pure zirconia to 50% alumina content, by a reactive pulsed-DC magnetron sputtering technique using two 50 mm diameter Zr and Al targets. The coating with a Zr-Al-O solid solution structure was composed of cubic-ZrO 2 and alumina distributed in the nano-size ZrO 2 grains (10-20 nm depending on the aluminum content). The deposited coatings were studied using high temperature Differential Scanning Calorimetry (DSC) up to 1350oC, X-ray diffraction (XRD) and High Resolution Transmission Electron Microscopy (HRTEM). It was found that after annealing, two exothermic events were observed. The first event appeared at 600°C and was completed at 800°C leading to alumina segregation from the solid solution phase into the grain boundaries, and the formation of the nc-ZrO 2 /a-Al 2 O 3 structure; while the second event appearing at 1000-1200oC was related to grain growth and transformation of the coating from a stabilized cubic to a monoclinic phase. The coating hardness after the first event was stabilized to 19.5±1.1 GPa value because of the segregation effect, which hindered the grain growth. However, after a second DSC cycle of the coating only one sharp endothermic transformation peak was observed at 1100°C which was attributed to zirconia transformation from monoclinic to tetragonal phase. The results show that in the case of zirconia-alumina coatings, the formation of the nc-ZrO 2 /a-Al 2 O 3 structure (nc-nanocomposite, a-amorphous) is governed by the driving force of the Al 2 O 3 segregation because of the immiscibility of the two phases.

Graded Ti/C composite films with carbon topcoats are prepared on bendable stainless steel foils by hybrid cathodic arc / glow discharge plasma-assisted chemical vapor deposition to simulate cardiovascular stents. Strong adhesion between the stainless steel substrate and carbon topcoat is achieved due to the graded Ti/C interface and it is further improved by increasing the pulse voltage. Moreover, the graded coating is more hydrophilic than the stainless steel substrate. (C) 2016 Elsevier B.V. All rights reserved.

Low voltage, low energy submerged pulsed arcs with a pulse repetition rate of 100 Hz, energy of 48 mJ and duration of 20 mu s were used to determine the electrode erosion rate during treatment of 10 mg l(-1) methylene blue (MB) dissolved in 40 ml of deionized water, with and without the addition of 0.5% H2O2. Anode/cathode pairs of Fe/Fe, Ti/Ti, Cu/Cu, Cu/Fe, Fe/Cu, Ti/Fe, Fe/Ti, Cu/Ti and Ti/Cu were used. Smaller cathode erosion was measured, in the solutions without H2O2, with copper cathodes than with other cathodes. Smaller anode erosion in the same conditions was demonstrated by using pairs with a Ti anode than with other anodes and larger erosion was found for Cu anodes. By adding H2O2 to the treated solution, smaller cathode erosion was measured by using pairs with a Ti cathode than with other cathodes and larger rates were measured for Fe cathodes. The largest anode erosion was observed for a Cu anode. The erosion of the anode and cathode depends on material combination of the electrode pairs, i.e. on the thermo physical properties of the electrode materials. The correlations of anode/cathode erosion ratio (G(a)/G(c)) with ratio (q(am)/q(cm)) for various electrode materials were found, where q(am) and q(cm) are heat fluxes in the body of the anode and cathode, respectively. The experimental data were fitted by curves described with equation G(a)/G(c) = A(q(a)/q(c))(-b) where A and b are experimental constants.

Erbium oxide (Er 2 O 3 ) coatings were deposited using filtered vacuum arc deposition (FVAD) and their structure and thermal stability were studied as a function of fabrication parameters. The coatings were deposited on silicon wafer and tantalum substrates with an arc current of 50 A and a deposition rate of 1.6 ± 0.4 nm/s. The arc was sustained on truncated cone Er cathodes. The influence of oxygen pressure ( P = 0.40-0.93 Pa), bias voltage ( V b = -20, -40 or grounded) and substrate temperature (room temperature (RT) or 673K) on film properties was studied before and after post deposition annealing (1273K for 1 hour, at P ~ 1.33 Pa). The coatings were characterized using X-ray diffraction (XRD), optical microscopy, scanning electron microscopy (SEM), X-ray photoelectron spectroscopy (XPS) and Knoop Hardness. Optical microscope images indicated that the coatings had very low macroparticle concentration on their surface. The macroparticle diameters were less than 2.5 I¼m. The coatings were composed of only Er 2 O 3 without any metallic phase under all deposition parameters tested. The coatings deposited on RT substrates were XRD amorphous and had a featureless cross-section microstructure. However, the coatings deposited on 673K heated substrates had a C -Er 2 O 3 structure with (222) preferred orientation and weak columnar microstructure. The coating hardness varied with deposition pressure and substrate bias, and reached a maximum value of 10 GPa at P = 0.4 Pa and V b = -40 V. The post-deposition annealing caused crystallization, and the coatings hardness dropped to 4 GPa with thermal treatment. However, after post-deposition annealing, no peeling or cracking appeared at the coating surface or the interface with the substrate.

Graded composite layers containing metal and plasma polymer components were deposited using a cathodic arc in conjunction with plasma immersion ion implantation. Using a bias potential throughout, pure metal was deposited initially using the cathodic arc alone and then acetylene was added to the process to increase the fraction of the plasma polymerized carbon film. To test adhesion, the substrate and film were strongly deformed by folding the substrate inward and outward with a small radius of curvature. Strong adhesion between the metal surface and the deposited layers was achieved by the use of the graded layers as inferred from the SEM observations of the deformation region. Strong adhesion of biologically active protein molecules to the surface of the graded layer was confirmed by detergent washing and colorimetric enzyme activity assays. These characteristics suggest that the coatings may be suitable for cardiovascular stent applications.

Ternary zirconia-alumina coatings with different compositional ratios, ranging from pure zirconia to 50% alumina content, were deposited by reactive sputtering from two targets, Zr and Al, in argon-oxygen mixtures. The coating composition was controlled by the Zr/Al target power ratio provided by two pulsed-DC power supplies. The coatings were ~1 µm thick and they were deposited on floating potential substrates at a temperature of 650±3K. XRD indicated that the pure zirconia coatings possessed a monoclinic structure with a grain size of 35-40 nm. Adding alumina to the zirconia coating stabilized the cubic zirconia phase and decreased the grain size to 10-15 nm. The alumina phase in the coatings remained amorphous. The hardness of the nanocomposite structure increased from 11.6±0.5 GPa to 16.1±0.5 GPa for an alumina content of 17%. At higher alumina concentrations, the zirconia phase became amorphous and the hardness decreased to 10-11 GPa. Structure stability of the zirconia-alumina coatings was studied by measuring the coating structure and hardness after annealing at temperatures up to 1173 K. Pure zirconia (m-ZrO2) coatings had low structure stability; the hardness reached a maximum value of 18±1 GPa after annealing at a temperature of 773-873K; however, at higher annealing temperatures the hardness decreased, reaching a minimum value of 12.3±0.6 GPa after annealing at 1173K. The hardness of the nanocomposite ZrO2/Al2O3 coating with various compositions increased with annealing temperature. The hardness of a coating with an alumina content of 17% reached a high value of 19.2±0.5 GPa after annealing at 1073-1173 K. Measurements of post annealing XRD analyses indicated that the stabilization of the coating structure with c-ZrO2/a-Al2O3 phases is the reason for the higher structure stability. From the analyses of phase stability and hardness before and after annealing, we conclude that adding alumina to the zirconia phase promotes the formation of nanocomposite c-ZrO2/a-Al2O3 coatings with a markedly higher stability than single-phase m-ZrO2. Highlights: 1. ZrO2/Al2O3 nanocomposite coatings were deposited by co-sputtering from Zr and Al targets. 2. Adding alumina to the zirconia coating stabilized the cubic zirconia phase. 3. ZrO2-17% Al2O3 coatings had a grain size of 10-15 nm and a hardness of 16.1±0.5 GPa. 4. ZrO2/Al2O3 coatings maintained a high hardness after annealing at 1173K with a high value of 19 GPa for alumina content of 17%. 5. The ZrO2/Al2O3 nanocomposite coatings were crack-free after annealing at 1173K.

Vacuum arc cathode spot motion was investigated on a “roof-shaped” aluminum cathode. This roof geometry included flat roof-top and four sloped sides, inclined by an angle α. A high speed camera was used to observe cathode spot motion in an external axial magnetic field. The spot velocity on the slopes and the distribution of cathode spots between the roof and slopes was determined. It was obtained that under a magnetic field the spot motion on the roof was slow (<;1m/s) and mainly random, while on the slopes fast retrograde motion was observed. This velocity increased linearly with the magnetic field, and decreased slightly with α. The general behaviour of the spot motion agreed with previously published data.