Optimization of metal heating in plasma-mechanical treatment

Results are presented of an experimental investigation of the process of energy transfer to the anode of an arc in application to plasma-mechanical treatment of components.Notation Q_y energy introduced per unit mass of the layer being cut, W/kg - Q integral energy flux in the anode, W - I arc current, A - L spacing between the plasmotron nozzle exit and the component, m - h spacing between the plasmotron nozzle exist and the cathode, m - d plasmotron nozzle diameter, m - G gas consumption, kg/sec - q energy flux density in the anode spot, W/cm² - r spacing from the center of the anode spot to the point at which the energy flux density is calculated, cm - q_m energy flux density at the center of the anode spot, W/cm² - k_q concentration coefficient, cm^–2 - S_o degree of heat propagation, m - thermal diffusivity factor, m²/sec - time, sec - k spacing between the plasmotron and the cutter, m - v cutting rate, m/sec - coefficient of energy transmission to the anode - N electrical power of the arc, W Translated from Inzhenerno-Fizicheskii Zhurnal, Vol. 47, No. 1, pp. 138–143, July, 1984.     

Precision Rate Tables

The precision unit described can reproduce angular rates in the range 2·10^–4–20 rad/sec to within 2·10^–7–10^–6 rad/sec.     

Simulating gas-discharge processes at a single cold microscopic point

The development of ionization avalanches in nitrogen at atmospheric pressure near a single cold microscopic point on a cathode surface has been simulated under the conditions of E/P ≫ 1 kV/(cm Torr), where E is the electric field strength and P is the gas pressure. It is established that a layer of dense gas-discharge plasma with a density of ∼10¹⁶ cm⁻³ is formed within a period of ∼1 ps as a result of the gas ionization by electrons emitted from the cathode. The current of fast electrons, which appears due to gas ionization is more than ten times greater than the field emission current and can reach I ∼ 1 A for one microscopic point.     

State of the art with plasma current interruptors

The state of research is considered for high-power pulse generators based on inductive energy stores and plasma interruptors. The main attention is given to plasma interruptors in which the low-resistance state lasts about 10^–6 sec. Basic features are indicated and characteristic components in the theory with an indication of problems in using the devices and particular examples of existing equipment.High-Current Electronics Institute, Siberian Division, USSR Academy of Sciences, Tomsk. Translated from Inzhenerno-Fizicheskii Zhurnal, Vol. 62, No. 5, pp. 720–722, May, 1992.     

Photoelectronic device for measuring plasma temperatures

A photoelectronic device for measuring plasma temperatures with a time resolution on the order of 5·10^–4 sec is described. Certain results of measurements are presented.     

A simple model for the interaction of a low-current vacuum arc with a copper cathode

Experimental and theoretical studies of the arc-cathode region have been made for several decades, but the task is not yet complete, despite many efforts and much progress. In this work, a numerical model describing the arc-cathode region is developed. The arc is treated as a steady-state phenomenon. The model is then applied to a vacuum arc discharge interacting with a Cu cathode at low current of 4–50 A. The model yields the temperature and electric field strength at the cathode surface, density of the current of the electrons emitted, total current density, cathode spot radius, different kinds of power densities in heating and cooling the cathode, and the plasma electron density. The comparison with experimental results shows good agreement. Published in Inzhenerno-Fizicheskii Zhurnal, Vol. 80, No. 6, pp. 63–72, November–December, 2007.     

Measurement of the flux-flow velocity in superconducting films by a time of flight method

Flux has been pulsed in on the left side of a superconducting film with a transport current present. The current moves the flux tubes to the right, where their arrival is sensed with a movable pickup coil. The velocity has been defined by the slope of a plot of distance vs. arrival time. Velocities of 1–3 × 10⁵ cm/sec for the first onset and of 0.5–2.7 × 10⁵ cm/sec for the maximum of the flux field have been measured. The total amount of flux decreased approximately linearly with distance traveled.Supported in part by the National Science Foundation and in part by the Cryogenics Center through a grant from the DOD Themis program. Based in part on a thesis (J.K.) submitted to Stevens Institute of Technology in partial fulfillment of the requirements for the Ph.D. degree.     

Method of recording CMOS IC parameters after a destabilizing pulse

The techniques presented for recording the parameters of a CMOS IC make it possible to determine the pulse transient response function of an integrated circuit and to observe the behavior of the IC during a destabilizing pulse and just after it for 10^–5–10^–4 sec.Translated from Izmeritel'naya Tekhnika, No. 4, pp. 51–52, April, 1995.     

Fabrication of carbon nanotubes by electrical breakdown of carbon-coated Au nanowires

A carbon nanotube has been generated by the electrically-induced breakdown of a carbon-coated Au nanowire. Under high current density the Au in the nanowire migrates towards both the anode and cathode resulting in a free-standing carbon nanotube and a 73% reduction in resistance. The resistivity of the carbon nanotube was < 8 × 10^− 5 Ω m and it could cope with a current density > 1.8 × 10¹¹ A/m², indicating a structural change from amorphous to graphitic carbon. The dimensions of carbon nanotubes produced in this way have an internal diameter controlled by the parent metal nanowire template.     

The emission effect of metal-tip removal in carbon nanotubes by bias-assisted ICPHFCVD

This paper presents a technique for the preparation of vertically grown carbon nanotubes (CNTs) by bias-assisted inductively coupled plasma hot-filament chemical vapor deposition. Purification of the CNTs using r.f. plasma in a one-step process, based on the different etching property of the metal tip is also discussed. The Ni at the tip of the CNTs was effectively removed by using r.f. plasma based on the different etching property. After purification CNTs show the multi-walled and hollow-type structure. The measured critical current density on CNTs with a Ni tip was 3.52×10^–7 A cm^–2 at 2.47 V m^–1 turn-on field and 6.6×10^–4 A cm^–2 at 4.8 V m^–1 of the critical field. On the other hand, the critical current density on purified CNTs after Ni removal by an r.f. source was 1.36×10^–7 A cm^–2 at 2.1 V m^–1 turn-on field and 1.5×10^–3 A cm^–2 at 6 V m^–1 of the critical field, respectively.     

Proton transport mechanism in ammonium dihydrogen phosphate

Coulometric, transient ionic current, electrical conductivity and IR investigations on polycrystalline and single crystal of ammonium dihydrogen phosphate (ADP) have been carried out. During coulometry, gases evolved both at the cathode (mostly H₂) and at anode (O₂) indicating the electrolysis of the H-O-H bridge. Transient ionic current study suggests the likely presence of two types of mobile ionic charge carriers (H⁺ and O^2–) with mobilities of 1.3×10^–4 and 3.3×10^–5 cm² V^–1 sec^–1. A comparative study of the IR spectra of the original and the electrolysed samples also supports the idea of possible electrolysis. The temperature dependence of the electrical conductivity have also been studied and interpreted in terms of possible deammoniation reaction and phase transformation. Finally, a mechanism for ionic transport in ADP is suggested.     

Velocity of the electric arc in a plasmatron discharge chamber

An experimental investigation of the velocity of a high-current arc with air injection in the discharge chamber of a coaxial sectioned plasmatron is described. The experiments showed that the velocity of the cathode spot on the electrode surface depends on the arc current and on the external magnetic field strength. The air flow rate in the plasmatron chamber was 7.1 g/sec.Translated from Inzhenerno-Fizicheskii Zhurnal, Vol. 17, No. 3, pp. 570–574, September, 1969.     

Material surface modification by pulsed ion beam

A new technique utilizing a high-power-density pulsed ion beam for modification of material surfaces is presented. The power density of the pulsed ion beam ranges between 10⁴ and 10⁷ wcm^–2, the kinetic energy is 1 to 5 KeV, the deposition energy is of the order of 1 to 10Jcm^–2 and the pulsed duration is about 60sec. The post-treatment samples were analysed using Auger electron spectroscopy, scanning electron microscopy, X-ray diffractometry, and Vicker's microhardness tester. It is found that the concentration of the injected particles has a Gaussian distribution. The thermal zone induced by the fast heating-cooling process forms a white-bright layer, indicating that there are new carbides and nitrides produced in the surface layer, which increases the microhardness of the surface.     

Nucleation control of diamond synthesized by microwave plasma CVD on cemented carbide substrate

Diamond was coated on to cemented carbide substrate by microwave plasma CVD, in which nucleation control of diamond crystals was investigated under constant deposition conditions; total pressure 30 torr, CH₄ flow rate 1 ml min^–1, H₂ flow rate 199 ml min^–1 and microwave power 550 W. Nucleation tends to occur selectively on the edge part of WC grains of the cemented carbide substrate with coarse WC grain size of about 1 m, where the nucleation density was 9×10⁶ cm^–2. The density increased to about 5×10⁷ cm^–2 when using a finegrained substrate (WC grain size 0.5 m). A considerably enhanced nucleation was observed by introducing a number of fine microflaws on to the substrate surface. Microflawing treatment with diamond fine powder (grain size 0–1/4 m) suspended in an ultrasonic cleaner bath was effective for increasing the diamond nucleation density up to 5×10⁸ cm^–2. The grain size of grown diamond crystals decreased with increasing microflawing time.     

An investigation of the features of development of high-velocity localized shear in metal

An experimental method of shear tests of metals with loading rates up to 10 m/sec has been developed. The results of shear tests of AMg6 alloy with a loading rate of up to 5 m/sec and a deformation rate of up to 10⁵ sec^–1 are presented. Deformation curves and values of critical shear deformations are given. Features of the kinetics of development of high-velocity localized shear in AMg6 alloy are investigated.Translated from Problemy Prochnosti, No. 3, pp. 41–45, March, 1995.     

Influence of current pulses on the mobility and multiplication of dislocations in Zn

For the purpose of clarification of the mechanisms of the electron-plastic effect the influence of current pulses with a length of 2·10^–4 sec and a density of more than 20 MA/m² on the mobility of pyramidal dislocations in Zn single crystals in the area of thermally activated movement at 77 and 293 K and also on their multiplication was studied by the method of selective etching. It was shown that the increase in the rate of movement of dislocations under the action of current pulses is accompanied by multiplication of the dislocations with current densities of more, than 10² MA/m². The rules established are discussed taking into consideration the pondermotive forces, thermal effects, electron-dislocation interaction, and the work of the Frank-Reid effect under the action of the electron wind.S. Ordzhonikidze Siberian Metallurgical Institute, Novokuznetsk. Translated from Problemy Prochnosti, No. 10, pp. 48–53, October, 1989.     

Wavelength measurements on lasers

Conclusions We developed a method which allows comparisons of the wavelengths emitted by two lasers with an accuracy of about 6·10^–6.The method and the setup are very advantageous for the infrared wavelength range, because the methods which are characterized by high measurement accuracy in the infrared region cannot be employed, and conventional methods cannot provide an accuracy better than 1·10^–5 (for the range 3–10). One can use photodiodes or photoresistors as the converting elements which can be operated without cooling and are characterized by a sufficiently high sensitivity.Translated from Izmeritel'naya Tekhnika, No. 6, pp. 42–43, June, 1971.     

Quantitative theory for the quantum interference effect in the transverse magnetoresistance of pure magnesium

A new quantitative theory is developed to calculate from first principles the transverse magnetoresistance of Mg for the special case in whichH is parallel to a [10 0]-type axis andJ is parallel to a [11 0]-type axis. For this case, magnetic breakdown produces a multiply coupled network of interfering electron trajectories which generate large-amplitude quantum oscillations in the transverse magnetoresistance. It is shown that two distinct regimes of quantum transport exist for these oscillations and that this theory can be used to derive the electron quantum state lifetime from experimental data. The sensitivity of this effect to extends the experimentally accessible range by four orders of magnitude from about 10 ^–12 to 10 ^–8 sec. In addition, since the quantum interference oscillations are essentially insensitive to the temperature dependence of the Fermi-Dirac distribution function, this effect is ideally suited to study the quantum state lifetime dependence on electron-electron scattering.Supported by NSF Grant GH-39932.     

Heat and mass transfer during condensation of water vapor from moist air in narrow channels

The results of an experimental investigation of heat and mass transfer during condensation of water vapor in narrow channels at pressures P=(0.133–1.0) · 10⁵ N/m² and velocities of the moist gas v_max=(0.5–10) m/sec are presented.Translated from Inzhenerno-Fizicheskii Zhurnal, Vol. 21, No. 1, pp. 71–74, July, 1971.     

Grid-controlled current switching in cathode-spot discharge

The first results of an investigation of the complete current switching (initiation and quenching) using a fine-mesh grid in discharge with a cathode spot on liquid cesium are reported. Experimental data show the possibility of using this method of control at current densities within 5–25 A/cm² in the grid plane.