A Study on Surface Roughness of Curved Silicon Crystal Spectrometer Fabricated by Plasma Chemical Vaporization Machining
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We propose the application of open-air type numerically controlled plasma chemical vaporization machining (NC-PCVM) to fabricate a doubly curved crystal (DCC) substrate. Since PCVM utilizes only a chemical reaction to remove the work piece surface, there is no degradation of the crystallographical properties of the work piece material. In our previous study, we succeeded in fabricating a curved Si (111) crystal substrate with a curvature radius error of 0.08 %. Rocking curve measurement results revealed that there was no lattice strain on the processed surface. However, surface roughness degraded after PCVM figuring. To reduce the surface roughness, we modified the structure of the electrode unit, which generates plasma, to be able to supply a shielding gas. By supplying helium with a flow rate of 0.5 L/min as the shielding gas, rms surface roughness of the silicon was reduced from 0.73 nm to 0.42 nm. Excessive supply of helium (> 1 L/min) and/or supply of argon caused deterioration of the surface roughness. These results indicate that appropriate supply of the shielding gas is effective in reducing roughness in the open-air type PCVM process.Keywords:
Vaporization
Crystal (programming language)
The lifetime curves of a single droplet impinging on heated surfaces of ceramics and stainless steel were investigated. The experiments were carried out while concentrating mainly on the temperature region in which the time for vaporization could be shortened. We observed and examined thoroughly the behavior of the droplet, taking photographs with a 16 mm high-speed camera and recording on videotapes. For materials such as ceramics having low thermal conductivity and a characteristic surface, the vaporization modes were different from those on stainless steel or other metal surfaces. The significant difference between them was in the existence of the wide temperature range yielding minimum vaporization times and short lifetimes. The ceramic surface facilitates rapid vaporization of a droplet over a wide temperature range.
Vaporization
Atmospheric temperature range
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A DC transfer type plasma with a maximum output of 60 kW was used to melt 10 kg of carbon steel and 3 kg of granular oxide mixtures ( Fe 2 O 3 , Al 2 O 3 , SiO 2 and CaO) containing non-radioactive cesium nitrate, for measuring Cs vaporization. These materials are the main components of low level miscellaneous solid wastes. The vaporization rate constant values obtained by approximating Cs vaporization by a first order reaction rate formula were in the range of (4.01–7.1)×10 -6 (m/s). The vaporization rate constant of Cs did not depend on the initial Cs content, and increased with the increase of slag basicity ( %CaO/%SiO 2 ). Since the vaporization rate constant was unaffected by the viscosity of the slag on which the Cs transfer rate in the slag depends, the Cs vaporization phenomenon from the slag can be estimated to be controlled by the vaporization step from the slag surface.
Vaporization
Slag (welding)
Caesium
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A simplified, direct approach is presented to the description of complex equilibria involving vaporization into vacuum. Emphasis is on the basic problem-solving process and on modification of existing techniques. Sequential solutions are presented to problems involving purification of a melt by vaporization into vacuum. The effects of concentration of melt and oxygen partial pressures on vaporization rates are demonstrated.
Vaporization
Sous vide
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Vaporization
Atmospheric temperature range
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Vaporization
Crystal (programming language)
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Vaporization
Volatilisation
Pyramid (geometry)
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Vaporization
Electric arc
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Vaporization
Thermogravimetric analysis
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Abstract Abstract – Adiabatic spray vaporization is investigated by analyzing the coupled problem of the vaporization of an ensemble of droplets in a gaseous medium whose properties are continuously being modified by the vaporization process. A criterion on the mixture properties for achieving complete spray vaporization is established. By further showing that the droplet emperature rapidly approaches a constant, characteristic, value after vaporization is initiated, simplified solutions are obtained for the transport of monodisperse, as well as polydisperse, sprays in quasi-one-dimensional chambers.
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Dispersity
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