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Glossary of MinSE


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E

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Energy dispersive analysis by X-rays.   An electron beam (≈20-30 KeV) is focused onto a the sample surface, which must be electrically conducting; among the many surface effects, X-rays, of characteristic energy are produced.   An optimal sample-electron beam distance is used to assure X-rays of sufficient intensity are brought to focus at a solid-state detector, chilled to liquid nitrogen temperature.   The detector is frequently isolated from the microscope vacuum chamber by a Beryllium window.   X-rays with an energy in the range of 1 to 20 keV are efficiently detected allowing the simultaneous detection of all elements heavier than boron, using at least one of the principal K, L, or M emission lines.   Some modern devices have ultra-thin windows or offer windowless detectors allowing the detection of elements down to Li.  However, it should be appreciated that the detection of low atomic elements below oxygen, is accompanied by a poor signal to noise ratio, making even semi-quantitative analysis difficult.   Quantification of heavier elements is easier; nowadays this is achieved routinely by dedicated computer software.  The method is very rapid.   EDX is an excellent tool for gaining an immediate idea of chemical composition.   Elemental mapping, in conjunction with secondary electron imaging is also a useful feature of this method.    For high accuracy chemical composition analysis, however, EDS is inferior to WDX.   The latter method is significantly better for light element analysis

Hungary flag EDX

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The techniques of forming coatings via electroplating or electrophoresis.

Hungary flag Elektro-bevonatolás

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A high power density beam generated by a device termed an electron gun.  This comprises a pair of anular electrodes and a resistively heated tungsten filament which emits electrons via thermionic emission.  The electrons are accelerated by respectively passing them through the centres of an anular cathode and anode.   After exiting the gun, the electrons are focussed by an electromagnetic field, generated by a solenoid.  Very high accelerating voltages can be used (≈500 KeV) and power densities of 106 to 107 W/cm2 are easily achieved.   Higher power densities are achievable by operating in pulse-mode; a similar principle to that deployed in Nd-YAG and excimer lasers.   In surface engineering an eletron beam is complimentary to a laser.    It is used as an evaporation device, e.g., in ion plating, or for surface alloying and transformation hardening of metallic materials.   Energy coupling to metallic surfaces is outstanding, but elelctron beams have the disadvantage of not been applicable to non-conducting surfaces, like dielectric ceramics (e.g., Al2O3).   Despite development devices that have demonstrated the feasibility of operation at atmospheric atmosphere (e.g, see Y. Arata: 'Plasma, Electron & Laser Beam Technology'; 1986, Ohio, American Society for Metals), the routine industrial use of electron beams remains restricted to the confines of a vacuum chamber (minimum pressure ≈10-4 torr).

Hungary flag Elektron sugár

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Carburising involving electron beam heating of surfaces into the austenitic range.  The carbon can be supplied as a gaseous hydrocarbon, but more readily as a pre-placed graphitic surface coating.   During electron beam heating, the carbon dissolves into the austenite and the structure is allowed to self-quench by conducton into the relatively cool core.  Treatment depths are relatively shallow <50 µm.   The technique is not widely used.

Hungary flag sugras cementálás

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An electron beam treatment applied to a metallic surface which is momentarily surface melted to enable the encapsulation of preplaced or injected ceramic powder particles.   The treatment is applicable to ferrous or non-ferrous metals and alloys.  There has been a lot of interest in recent years in applying such treatments to aluminium and titanium alloys because both suffer from the disadvantage of responding poorly to conventional thermochemical diffusion treatments, i.e., they develop very shallow treatments, if any.   Electron beam cladding offers the possibility to develop deeply hardened surfaces, up to 1 mm.   The process is analogous to laser cladding.

Hungary flag Elektron sugaras bevonatolás

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An ion plating or vacuum evaporation process that uses an electron beam (eb) to vapourise the metallic source constituent(s) of a coating.  It is requirement of such devices that the electron beam should be housed in a differentially pumped vacuum chamber attached to the main vessel.   This enables the electron beam to operate at the preferred pressure of 10-4 torr while allowing a glow discharge plasma to be created at higher pressure, ≈10-2 torr, in the main deposition vessel (diagram).     The electron beam is steered into the main chamber, via a small aperture, using a system of electromengnets.   Sufficient power density is available to vapourise even refractory metals like tungsten and molybdenum.   Also see ion plating.

Hungary flag Elektron sugaras párologtató PVD

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An electron beam treatment aimed at producing an amorphous/glassy surface layer.  It involves electron beam heating a surface with power densities ≈ 105 to 107 W/cm2 and interaction times ≈ 10-3 to 10-7 seconds; subsequently the surface rapidly solidified at cooling rates exceeding 105 K/s, which suppresses the nucleation and crystallisation processes, thereby promoting vitrification/amorphortisation.   Less widely practised than laser glazing.

Hungary flag Elektron sugaras polírozás

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A process involving electron beam heating of the surface layer of a steel into the austenitic temperature range followed by rapid self-quenching by conduction into the relatively cool core.  The process produces relatively low distortion.  It is claimed to be more economic than laser transformation hardening.

Hungary flag  Elektron sugaras felület edzés

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Any heat treatment utilising an electron beam as the principal heat source. 

Hungary flag Elektron sugaras kezelés

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The electrodeposition of thin adherent layers of metals or alloys onto a metallic substrate, thereby creating a composite material whose surface properties are dominated by those of the coating.   Chromium and nickel plating are probably the two commonest forms of electroplating.   Developments in electroplating technology include: pulse plating, modulated current plating, superimposed current plating and periodic reverse current electroplating.

Hungary flag fémbevonás


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