Ion-beam modification of track membrane surface

An ion-beam method to modify the track membrane surface is suggested. An ion gun based on a magnetron sputterer is developed. This gun provides ion energies in the range of 5 eV–1 keV, ion current density up to 0.8 mA/cm², and an ion beam aperture of 90 mm. After the track membrane surface has been irradiated by argon ions with an energy of 50–100 eV, the angle of surface-water contact decreases from 65°–75° to 10°–25°. If the irradiating ion energy is 300–800 eV, the angle of contact increases from 65°–75° to 90°–100°.     

Multi-element focused ion beams using compact microwave plasma ion source

Focused ion beams (FIB) are widely used for research and applications in nanoscience and technology. We have developed a compact microwave plasma based multi element FIB (MEFIB) system in order to widen the applications and overcome the limitations faced by conventional Liquid Metal Ion Source (LMIS) based FIB systems, that provide primarily Ga ions. The MEFIB source provides high density plasmas (∼1.5 × 10¹¹ cm⁻³) in a compact cross section. Recently the ion energy spread in the plasma meniscus from where the beams are extracted is found to be small (∼5 eV) [1–3]. The beam extraction and focusing are carried out using electrostatic multi electrode assembly. AXCEL INP and SIMION simulation codes are employed for the design of electrostatic Einzel lenses for beam focusing. The beam focal point is measured using a specially designed three slit Faraday cup and the spot size is measured by the micrography of craters formed by the focused ion beams impinging on copper and aluminium substrates. The initial experimental results show a focused beam spot size of ∼ 25 micron which is in good agreement with the simulations. By further reduction of electrode apertures and operating the second Einzel lens at higher potentials, submicron focused ion beams can be expected.     

Influence of the cathode and anode jets on the properties of a high-current electric arc

A study is made of the effects related to the formation of electrode jets in discharges in hydrogen and air at a current of 10⁵–10⁶ A, a current growth rate of 10¹⁰ A/s, an initial pressure of 0.1–4.0 MPa, and a discharge gap length of 5–40 mm. After secondary breakdown, jets are observed in a semitransparent discharge channel expanding with a velocity of (4–7)×10² m/s. The formation of shock waves in the interaction of the jets with the ambient gas and the opposite electrode is observed by the shadowgraphy method. Seventy microseconds after the beginning of the discharge, the pressure of the metal vapor plasma near the end of the tungsten cathode amounts to 177 MPa. The brightness temperature in this case is T=59×10³ K, the average ion charge number is [`(m)] = 3.1\overline m = 3.1 , and the metal vapor density is n=5.3×10<sup>19</sup> cm<sup>−3</sup>. After 90 μs, the average ion charge number and the metal vapor density near the anode end are [`(m)] = 2.6\overline m = 2.6 and n=7.4×10¹⁹ cm⁻³, respectively. Based on the experimental data, possible reasons for the abnormally high values of the total voltage drop near the electrodes (up to ∼1 kV) are discussed.     

The electrochemical behavior of Dy(III) in eutectic LiF-DyF<Subscript>3</Subscript> at W electrode

The electrochemical reduction process of Dy ion on tungsten electrode at 1103 K in Dy₂O₃-LiF-DyF₃ molten system was studied by cyclic voltammetry, chronoamperometry, and chronopotentiometry methods with a three-electrode system on the electrochemical workstation AUTOLAB. The results showed that Dy³⁺ could be deposited at around ?0.75 V on inert W electrode compared with platinum electrode. The reduction process of Dy ion on W electrode occurred in a single step with the exchange of three electrons because one reduction peak was observed, and the calculated transfer electron number was three. Chronoamperograms indicated that the nucleation process of dysprosium ions was instantaneous three-dimensional nucleation on a tungsten electrode. The cathode electrochemical process on the tungsten electrode was controlled by the diffusion of ions, and the diffusion coefficient was 1.159 × 10^?4 cm²/s, which was calculated from a chronopotentiogram.     

Wide gas-ion beam source based on an arc discharge in a nonuniform magnetic field

The construction of an ion source based on a low-pressure arc with a screened cathode spot is described. The source is ignited by an auxiliary glow discharge in a magnetron electrode system. Ions are extracted from the plasma of the anode part of the arc, generated in a reflective electrode system. The effect of the magnetic induction and the emitter electrode potential on the parameters of the anode plasma was investigated, and the conditions required for generation of a dense uniform plasma, ion emission from which gives beams of ions of nitrogen, argon, oxygen, other gases with cross section 100 cm², current density 10 mA/cm² and nonuniformity of the plasma distribution in the beam cross section 10%, were determined. The formation of wide and converging beams with ion energies up to 50 keV by multiple-aperture ion-optic systems were examined. The source operates in the periodic-pulse mode. The repetition frequency of 1-msec pulses can be regulated from 0 to 50 sec^–1 giving an average beam current of up to 50 mA. It is intended for use in technologies for modification of the surface properties of materials and deposition of thin films. A cold cathode makes possible prolonged operation of the source with chemically active gases.Institute of Electrophysics, Ural Branch of the Russian Academy of Sciences. Translated from Izvestiya Vysshykh Uchebnykh Zavedenii, Fizika, No. 3, pp. 66–75, March, 1994.     

Pseudo-capacitive properties of LiCoO<Subscript>2</Subscript>/AC electrochemical capacitor in various aqueous electrolytes

LiCoO₂ particles were synthesized by a sol-gel process. X-ray diffraction analysis reveals that the prepared sample is a single phase with layered structure. A hybrid electrochemical capacitor was fabricated with LiCoO₂ as a positive electrode and activated carbon (AC) as a negative electrode in various aqueous electrolytes. Pseudo-capacitive properties of the LiCoO₂/AC electrochemical capacitor were determined by cyclic voltammetry, charge–discharge test, and electrochemical impedance measurement. The charge storage mechanism of the LiCoO₂-positive electrode in aqueous electrolyte was discussed, too. The results showed that the potential range, scan rate, species of aqueous electrolyte, and current density had great effect on capacitive properties of the hybrid capacitor. In the potential range of 0–1.4 V, it delivered a discharge specific capacitance of 45.9 Fg^–1 (based on the active mass of the two electrodes) at a current density of 100 mAg^–1 in 1 molL^–1 Li₂SO₄ aqueous electrolyte. The specific capacitance remained 41.7 Fg^–1 after 600 cycles.     

Effect of the electron beam and ion flux parameters on the rate of plasma nitriding of an austenitic stainless steel

The method of nitriding of metals in an electron beam plasma is used to change the current density and energy of nitrogen ions by varying the electron beam parameters (5–20 A, 60–500 eV). An electron beam is generated by an electron source based on a self-heated hollow cathode discharge. Stainless steel 12Kh18N10T is saturated by nitrogen at 500°C for 1 h. The microhardness is measured on transverse polished sections to obtain the dependences of the nitrided layer thickness on the ion current density (1.6–6.2 mA/cm²), the ion energy (100–300 eV), and the nitrogen-argon mixture pressure (1–10 Pa). The layer thickness decreases by 4–5 μm when the ion energy increases by 100 V and increases from 19 to 33 μm when the ion current density increases. The pressure dependence of the layer thickness has a maximum. These results are in conflict with the conclusions of the theory of the limitation of the layer thickness by ion sputtering, and the effective diffusion coefficient significantly exceeds the well-known reported data.     

Characteristics of an ion source with a plasma cathode and a multipole magnetic system for confining fast electrons

Parameters and ion-emission characteristics of the plasma generated in the anode stage of an ion source with a hollow glow-discharge plasma cathode are studied. To decrease the minimum operating gas pressure to 5×10³ Pa, a multipole magnetic system was installed on the surface of the hollow cathode and the peripheral magnetic field was enhanced in the anode stage of the source. The effect of the gas pressure, the plasma-cathode current, and the voltage between the electrodes of the anode stage on the value of the ion current extracted from the plasma is investigated. It is found that the size of the exit aperture of the hollow cathode substantially affects the efficiency of ion extraction. The potential (1–5 V) and the electron temperature (1–8 eV) of the anode-stage plasma are measured by the probe method. The conditions are determined that ensure the maximum ion-emission current from the plasma at low gas pressures.     

Generation of thermonuclear energy by fusing hydrogen and lithium atoms

A method of designing a thermonuclear reactor based on the modified Cockroft-Walton accelerator, where the lithium-proton fusion was first observed, is considered. It is proposed that the reactor have the form of a spherical capacitor with a point lithium cathode used as the inner electrode and a spherical anode, as the outer electrode. The interelectrode space is filled with hydrogen. A high-voltage electric pulse applied to the electrodes is used as a driver. The reactor parameters providing an ion temperature of 100 keV and a proton flux of 8.6×10¹⁵ W/cm² to the cathode are determined. The basic elements of a system generating thermonuclear fusion energy, including those of the energy conversion chamber with a fusion chamber inside, are listed, and possible applications of the system are indicated.     

Spectral components that form UV absorption spectrum of Ce3+ and Ce(IV) valence states in matrix of photothermorefractive glasses

We have measured the UV absorption spectra of photothermorefractive glasses of the system Na₂O-ZnO-Al₂O₃-NaF-SiO₂ doped by cerium oxide in the range of (2.8–5.0) × 10⁴ cm⁻¹ (360–200 nm). The spectra have been processed by the method of dispersion analysis based on the analytical convolution model for the complex dielectric function of glasses. We show that the absorption band centered at 3.3 × 10⁴ cm⁻¹ (∼303 nm) that is attributed to the transition 2F _5/2 → 5d in the Ce³⁺ ion, is an envelope of three spectral components. The broad absorption range (3.5–4.7) × 10⁴ cm⁻¹ (200–270 nm) that is commonly interpreted as a charge transfer band of the Ce(IV) valence state, is an envelope of at least three spectral components.     

Improvement of the efficiency of a glow discharge-based ion emitter with oscillating electrons

Ion emission from the plasma of a low-pressure (≈5×10⁻² Pa) glow discharge with electrons oscillating in a weak (≈1 mT) magnetic field is studied in relation to the cold hollow cathode geometry. A hollow conic cathode used in the electrode system of a cylindrical inverted magnetron not only improves the extraction of plasma ions to ≈20% of the discharge current but also provides the near-uniform spatial distribution of the ion emission current density. The reason is the specific oscillations of electrons accelerated in the cathode sheath. They drift in the azimuth direction along a closed orbit and simultaneously move along the magnetic field toward the emitting surface of the plasma. A plasma emitter with a current density of ≈1 mA/cm² over an area of ≈100 cm² designed for an ion source with an operating voltage of several tens of kilovolts is described.     

Europium-sensitized Chemiluminescence of System Tetracycline–H<Subscript>2</Subscript>O<Subscript>2</Subscript>–Fe(II)/(III) and Its Application to the Determination of Tetracycline

Chemiluminescence (CL) of the reaction system tetracycline–H₂O₂–Fe(II)/(III)–Eu(III) was used for the determination of tetracycline hydrochloride in water, pharmaceutical preparations, and honey. The CL spectrum registered for this system shows emission bands typical of Eu(III) ions, with a maximum at λ ∼ 600 nm, corresponding to the electronic transitions of ⁵D₀ → ⁷F₁ and ⁵D₀ → ⁷F₂. A strong chemiluminescence intensity characteristic of europium(III) ions in the system tetracycline–H₂O₂–Fe(II)/(III)–Eu(III), as contrasted to the emission of the system tetracycline–H₂O₂–Fe(II)/(III) without Eu(III), proves that the Eu(III) ion plays the role of a chemiluminescence sensitizer, accompanying tetracycline oxidation in the Fenton system (H₂O₂–Fe(II)/(III)). A linear dependence was observed for the integrated CL light intensity on the tetracycline concentration in the range of 2 × 10⁻⁷ to 3 × 10⁻⁵ mol l⁻¹ with the detection limit of 5 × 10⁻⁸ mol l⁻¹ in aqueous solution.     

Diffusion study of <Superscript>15</Superscript>N implanted into α-Ti using the nuclear resonance technique

The diffusion of ¹⁵N in α-Ti was studied in the 673–1023 K temperature range by using the ion implantation and nuclear resonance techniques. The measurements show that the diffusion coefficients follow an Arrhenius behavior D(T)=D₀ ^-Q/RT, where D₀=(1.1±0.8)×10^-7 m² s^-1 and Q=(183±2) kJ/mol. A comparison with previous results is also given. PACS 66.30.Jt; 85.40.Ry     

Electrochemical properties of a proton conducting polymer

Electrochemical, optical and thermal characterisation of a proton conducting polymer system based on poly(2-acrylamido-2 methyl-propane-sulfonic acid) (Poly-AMPS) for use in electrochromic windows is reported. The polymer electrolyte has been obtained by cross-linking branched poly(ethylene imine) with the 2-acrylamido-2 methyl-propane-sulfonic acid. The conductivity of the poly-AMPS films is influenced by the water content in the membrane and can vary between 10⁻⁴ and 10⁻⁷ Ω⁻¹ cm⁻¹. A minimum activation energy of 17±3 kJ/mol is estimated by a simple Arrhenius model. Poly-AMPS is very sensitive to the humidity in the surroundings and electrochromic windows should be sealed if poly-AMPS is used. Temperatures above 45–50 °C give increasing cracks in the polymer and loss of adhesion to the electrode surface. Paper presented at the 4th Euroconference on Solid State Ionics, Renvyle, Galway, Ireland, Sept. 13–19, 1997     

Zn-Co oxide electrodes with excellent capacitive behavior for using supercapacitor application

In the present study, super-capacitive behavior of spinel Zn-Co oxides (with different Zn⁺²/Co⁺² mol ratio) has been thoroughly investigated. The spinel of transition metal oxides with different morphologies has been synthesized with hydrothermal method on Ni foam as substrate layer. The specific capacitance of the Zn-Co oxide electrode prepared at 180 °C for 5 h with different Zn⁺²/Co⁺² mol ratios of 1:0, 2:1, 1:1, 1:2, 0:1 were investigated and measured 405, 842, 726, 1237, 705 F g^?1, respectively at 50 mV s^?1 scan rate. Zn-Co oxide with Zn⁺²/Co⁺² mol ratio of 1:2 was also synthesized at two different temperatures of 120 and 150 °C for 5 h with the specific capacitance of 1147, 917 F g^?1 at 50 mV s^?1 scan rate, respectively. Among the obtained data, the sample with Zn⁺²/Co⁺² mol ratio of 1:2 prepared at 180 °C for 5 h possessed highest specific capacitance. The cyclic life of this electrode showed 92% capacitance retention after 1000 cycle of charge-discharge. All results revealed that Zn-Co oxides had excellent supercapacitive properties due to multiple oxidation states and fast ion/electron transfer at the surface of electrode which could be offered as suitable devices for energy storage applications.     

Radiation damage of material surfaces under prolonged irradiation with He+ and Ar+ ions with broad energy spectra

The results of studying the redistribution of Be, Al, Ti, Fe, Cu, Zr, Mo, and W atoms incorporated in polycrystalline metal samples under irradiation with He⁺, (He⁺ + Ar⁺), and Ar⁺ ion beams with a broad energy spectrum and an average energy of 10 keV at irradiation doses of 1 × 10²¹ ion/cm² are studied. It is discovered that irradiation at doses exceeding 1 × 10¹⁹ ion/cm² results in local small-crystal formations being produced in a near-surface substrate layer. Their typical dimensions are less than 1–5 μm, and their the density is up to 1–100. They contain incorporated atoms and impurity atoms with a concentration of 0.1–10 at %. Subsequent irradiation at a dose of 1 × 10²⁰ ions/cm² or more leads to disappearance of these formations, mainly because of sputtering processes.     

Reference electrode formation in potentiometric CO2 sensors with alkali ion conducting alumosilicate glasses as solid electrolytes

Potentiometric CO₂ gas sensors with Li conducting glasses/glass ceramics of the system Li₂O-Al₂O₃-SiO₂ (different nominal composition) as solid electrolytes have been investigated. Li₂CO₃ was used as CO₂ and O₂ sensitive auxiliary electrode. During the sensor test measurements, the CO₂ partial pressure was varied between 1×10⁻³ and 1×10⁻¹ bar at a constant O₂ partial pressure of 2.1×10⁻¹ bar whereas N₂ was used as carrier gas. Comparative measurements were accomplished with sensors comprising Na and K ion conducting glasses. A metastable reference electrode was formed at the contact zone between the Au metal electrode and the former Li glasses of definite nominal composition by crystallization processes taking place, which lead to stable, reproducible CO₂ dependent EMF signals for more than 90d. The thermodynamically expected EMF difference and the observed EMF difference agree quite well between 500 and 600 °C. At 600 °C, the drift of sensors with glasses as solid electrolytes and direct Au glass/glass ceramics contact as reference electrode amounts typically 0.32 mV/d (p(CO₂)=1×10⁻³ bar, p(O₂)=2.1×10⁻¹ bar at the measuring electrode), if a metastable multiphase equilibrium is formed. At identical partial pressures of CO₂ and O₂, the signal reproducibility of these sensors with different solid electrolyte glasses of the same nominal composition lies within 30 mV at 600 °C. Paper presented at the 3rd Euroconference on Solid State Ionics, Teulada, Sardinia, Italy, Sept. 15–22, 1996     

A neutron and x-ray diffraction investigation of intermediate range structure in silver borate glasses

The ion diffusion mechanism in ion conducting glasses has in many reports been suggested to be linked to the structure. However, in most cases the structures of the glasses are not very well known. We have investigated the structure of the glass system (AgI)_x (Ag₂O-2B₂O₃)_1−x, with x=0, 0.6 by neutron and x-ray diffraction experiments. AgI doping produces an intense peak in the neutron data at an anomalously low Q-value (0.8 Å⁻¹) that indicates increased intermediate range ordering. Only a weak peak is observed at a similar Q-value in the x-ray structure factor. By comparing the different neutron and x-ray weighting factors the origin of the anomalous peak is unambiguously attributed to correlations within the B-O network. The experimental results have been used to model the glasses by Reverse Monte Carlo simulations to obtain more detailed views of the structures. Paper presented at the 1st Euroconference on Solid State Ionics, Zakynthos, Greece, 11 – 18 Sept. 1994     

Circular ion diode with self-magnetic insulation

The results of a study of the generation of a gigawatt-level pulsed ion beam formed by a diode with an explosive-emission potential electrode in self-magnetic insulation mode are presented. The experiments have been performed on the TEMP-4M ion accelerator operating in double-pulse formation mode: the first pulse is negative polarity (300–500 ns, 100–150 kV) and the second is positive (150 ns, 250–300 kV). The ion current density is 20–40 A/cm²; the beam consists of protons and carbon ions. To increase the efficiency of the ion current generation, a circular geometry diode is proposed. It is shown that with the new design, the plasma is effectively formed over the entire working surface of the graphite potential electrode. During ion beam generation, magnetic insulation of the electrons is achieved over the entire length of the diode (B/B _cr ≥ 3). Because of the high drift velocity, the transit time of electrons in the anode-cathode gap is 3–5 ns, whilst the transit time of C⁺ carbon ions exceeds 8 ns. This indicates low efficiency self-magnetic insulation for this geometry of diode. At the same time, it has been observed experimentally that during ion current generation (the second pulse), the electron component of the total current is suppressed by a factor of 4–5. A new mechanism of limiting the electron emission, which explains the decrease in the electron component of the total current in the circular diode with self-magnetic insulation, is proposed.