Arc Plasma Spraying Research Articles

Developments of MIC circulators from 1 to 40 GHz

Techniques and geometries for MIC circulators employing ferrite discs embedded in dielectric substrates have been developed extensively at frequencies ranging from 1 to 40 GHz. This form of fabrication, in which fit of the ferrite disc and finish are important, has proved reliable in use and to be of low cost. At high microwave frequencies microstrip to waveguide transitions are used with quartz substrates, whilst at low frequencies conductor geometry may be modified to reduce overall size of circulators and matching sections. Medium power loads using inserts of barium ferrite have been developed which can be incorporated into the microwave ferrite disc. For extreme environments circulator inserts may be deposited by arc plasma spraying of ferrite powder.

X-Band Microstrip-Inserted Puck Circulator Using Arc-Plasma-Sprayed Ferrite (Short Papers)

Experimental circulators using ferrite pucks which have been sprayed into cavities in dielectric substrates by an arc-plasma spray (APS) process are described.

Production of Resistors by Arc Plasma Spraying

Arc plasma spraying (APS) is an accepted method of producing coatings for many engineering applications. The wide range of materials that can be used to form the thick film coatings make this technique interesting as an alternative method of producing electrical components and circuits.The manufacturing procedure is outlined and the potential advantages of this method of making thick film resistors are listed.The effect on the physical and electrical properties of the films produced by variation of the arc plasma gun current, gas flow rate and powder particle size are reported together with the effect of varying gun/substrate distance and the topography of the substrate surface.It is shown that using a mixture of NiO and Fe3O4powders with a particle size range of 1–20μm it is possible to produce films on a glass substrate with sheet resistivities from 5–500 Ω/sq; temperature coefficients of resistance vary from +20 to −8 × 10−4per ℃, depending on resistor composition and film thickness.The results given for a 10,000 hour life test carried out at 150℃ in air show a mean charge in resistance of ~−5%.It is concluded that APS offers a viable method of producing thick film resistors and conductors on low cost substrates.

Events

‘The process of surface coating involves the deposition of a layer of one material on to another’. Such a definition embraces a wide variety of technologies, based in a number of different scientific disciplines, which have grown up to meet specific problems in particular industries. For example, the process of sputter‐deposition grew from physics through the electronics industry as a means of depositing thin films of metals, semiconductors and ceramics, but it is now finding increasing application in engineering industries generally, for coating of mechanical components. Similarly, arc plasma spraying was developed in the metals industry as a means of coating bearings and the like; it is now being explored as a means of producing thick films for electronics applications. The coating of metals with plastic films for corrosion protection draws on organic and inorganic chemistry and has grown into a considerable technology applicable in a wide variety of industries.

Polycrystalline Ferrite Films for Microwave Applications Deposited by Arc-Plasma

The arc-plasma spray deposition has been successfully applied to fabrication of planar ferrite microwave integrated circuits. Powdered commercial sintered microwave ferrites were deposited at rates up to 2 mils/min on 1 sq in. dielectric substrates by arc-plasma spray deposition. Process controls produced densities >99% theoretical and also maintained stoichiometric agreement between deposited films and starting material. Annealing expanded <0.1 μ grains to useful sizes of 1 to 20 μ and controlled cation distribution. Special annealing techniques were necessary for ferrites having volatile products such as Ni–Zn compounds. Magnetic and microwave properties of several deposited Mg–Mn ferrites and CeYIG agreed closely with bulk values. Remanence ratios up to 0.87 were noted. Practical application of arc-plasma deposition required material compatibility studies at high temperature. These considerations often superseded microwave properties as criteria for material section.

Chemical vapour deposition of aluminium oxide on steel

Oxides in general, by reason of their chemical inertia in oxidising atmospheres, high melting point and high mechanical strength, afford a suitable protective coating at high temperatures. Aluminium oxide in particular also has good thermal shock resistance, good impact resistance at high temperatures, and moderate self‐sealing properties. Hitherto it has been applied to turbojets, space components and rocket jets by flame spraying or arc plasma spraying. Since the characteristic properties of the coating, and hence its efficiency, are directly associated with its degree of structural perfection, the application technique has great importance; in this sense it may be thought, that chemical vapour deposition, allowing the ‘construction’ of the coating atom by atom or molecule by molecule, could produce a material having chemical and physical properties close to the theoretical. For this and other reasons the authors have already had the idea of studying the possible application of this technique for the preparation of a coating of aluminium oxide.

ARC Plasma Spraying—An analysis

ARC Plasma Spraying—An analysis

Tungsten Fabrication by Arc Spraying

This paper is concerned with the development of the plasma-arc spray process for the fabrication of free-standing tungsten bodies and its projection from the laboratory into the production of full-scale hardware.