THE INFLUENCE OF PRECIPITATION PARAMETERS OF VACUUM- ARC NANOCRYSTALLINE COATING TI-MO-N ON NANOHARDNESS AND WEAR RESISTANCE OF PISTON RINGS

It has been investigated the influence of multi-layered vacuum-arc nanostructure coating Ti - Mo - N on wear resistance of piston rings. The influence of vacuum-arc coating parameters on nanohardness has been set

Emission tester for high-power vacuum tubes

A simple emission-testing circuit for high power vacuum tubes to check their output stability is described. With modification it may be useful in testing mercury-arc rectifiers

Outer planets probe testing

An atmospheric entry Probe is being developed by NASA Ames Research Center (ARC) to conduct in situ scientific investigations of the outer planets' atmospheres. A full scale engineering model of an MDAC-E Probe configuration, was fabricated by NASA ARC. Proof-of-concept test validation of the structural and thermal design is being obtained at NASA ARC. The model was successfully tested for shock and dynamic loading and is currently in thermal vacuum testing

Polyelectrolyte Adsorption

The problem of charged polymer chains (polyelectrolytes) as they adsorb on a planar surface is addressed theoretically. We review the basic mechanisms and theory underlying polyelectrolyte adsorption on a single surface in two situations: adsorption of a single charged chain, and adsorption from a bulk solution in $\theta$ solvent conditions. The behavior of flexible and semi-rigid chains is discussed separately and is expressed as function of the polymer and surface charges, ionic strength of the solution and polymer bulk concentration. We mainly review mean-field results and briefly comment about fluctuation effects. The phenomenon of polyelectrolyte adsorption on a planar surface as presented here is of relevance to the stabilization of colloidal suspensions. In this respect we also mention calculations of the inter-plate force between two planar surfaces in presence of polyelectrolyte. Finally, we comment on the problem of charge overcompensation and its implication to multi-layers formation of alternating positive and negative polyelectrolytes on planar surfaces and colloidal particles.Comment: 11 pages, 4 PS figures (Latex/RevTex), submitted to C.R. Acad. Sci (Paris

High-strength tungsten alloy with improved ductility

Alloy combines superior strength at elevated temperatures with improved ductility at lower temperatures relative to unalloyed tungsten. Composed of tungsten, rhenium, hafnium, and carbon, the alloy is prepared by consumable electrode vacuum arc-melting and can be fabricated into rod, plate, and sheet

Microhardness studies on thin carbon films grown on P-type, (100) silicon

A program to grow thin carbon films and investigate their physical and electrical properties is described. Characteristics of films grown by rf sputtering and vacuum arc deposition on p type, (100) silicon wafers are presented. Microhardness data were obtained from both the films and the silicon via the Vickers diamond indentation technique. These data show that the films are always harder than the silicon, even when the films are thin (of the order of 1000 A). Vacuum arc films were found to contain black carbon inclusions of the order of a few microns in size, and clusters of inclusions of the order of tens of microns. Transmission electron diffraction showed that the films being studied were amorphous in structure

Process for HIP canning of composites

A single step is relied on in the canning process for hot isostatic pressing (HIP) metallurgy composites. The composites are made from arc sprayed and plasma sprayed monotape. The HIP can is of compatible refractory metal and is sealed at high vacuum and temperature. This eliminates outgassing during hot isostatic pressing

Characterization of ISF-VAT performance in weak magnetic nozzle

Vacuum arc thruster performance in a magnetic nozzle configuration is experimentally characterized. Measurements are performed on a miniature coaxial thruster with an anode inner diameter of $1.8$ mm. The magnetic field B is produced by a single air coil, $18$ mm in diameter. Direct measurement of thrust, mass consumption and arc current are performed. To obtain statistically viable results $\approx 6000$ arc pulses are analyzed at each operational point. Cathode mass erosion is measured using laser profilometry. To sustain thruster operation over several measurement cycles, an active cathode feeding system is used. For $0< B \leq 0.2$ T performance increase over the non-magnetic case is observed with the best thrust to arc power ratio $T/P \approx 9$ $\mu$N/W obtained at $B \approx 0.2$ T. A parametric model is provided that captures the performance enhancement based on beam collimation and acceleration by the magnetic nozzle. For $B > 0.2$ T the arc discharge is shown to be suppressed nullifying any additional gains by the nozzle effect