Papers by Keyword: Vacuum

Abstract: A new welding technique has been developed for manufacturing large aluminum chambers for an ultra-high vacuum (UHV) system. Combined with appropriate manufacturing processes, the aluminum chambers have an oil-free interior surface finished for an ultra-high vacuum environment before aluminum welding. An automatic welding system, which comprises six welding torches to implement simultaneously two longitudinal side welds of the asymmetric chamber, is introduced. In traditional manual welding, the key success factors focus on elimination as much as possible the distortions of structural assemblies. The six-torch welding and a clamp-free approach together address the issue of reducing distortion and minimizing residual stresses with a novel one-step welding process. From the beginning of CNC machining to the end of vacuum component assembly, deformations through all process sequences are measured and controlled under 0.35 mm. In this paper, both the manufacturing sequences and statistical analysis of deformation control are presented in detail.

Abstract: The existing methodology for Front Opening Unified Pod (FOUP) cleaning, storage, and transfer is inherently flawed in three areas: a) equipment layout, b) intra-process wait time, and c) human handling. In each area, improved solutions are suggested and a new approach is developed and named In-line FOUP Cleaner (IFC). IFC is a new, singular approach accomplished via total integration of multiple equipment types including sorter, FOUP cleaner, stocker, particle counter, and the FDC monitoring system. Utilizing the IFC approach, significant improvements have been documented with respect to all three areas of concern. Overall cost savings, as well as a side benefit of improved fume removal, are carefully observed. It appears to be an interesting approach to solving the problems associated with FOUP cleaning, storage, and transfer for the next generation semiconductor fab.

Abstract: Titanium alloys processed by the powder metallurgy route (PM) are sintered in vacuum, the higher the better. This philosophy is carried over to MIM titanium alloys. In the MIM process a large amount of out gassing of binders takes place, which affects the vacuum level and hence the interstitial element pick up in the titanium. In this paper the effect of gaseous material in vacuum is discussed and an alternate method of debinding and sintering in argon is proposed. Three processing conditions are applied to MIM tensile bars made from Ti-6-4 materials. First they are debound and sintered under high vacuum, second debound under argon and sintered in high vacuum and third debound and sintered in flowing argon. The physical properties and interstitial element contents are presented and the effects of the material structures due to different processing on the properties are discussed.

Abstract: Based on the Sommerfeld free-electron model, the specifics of field emission from metal cathode covered by nanometer oxide layer into vacuum was theoretically studied by the example of systems «W-WO₃-vacuum» and «Al-Al₂O₃-vacuum». The significant influence of natural oxide on the current-voltage (CV) characteristics in the region of strong electric fields (more than 10⁷ V/cm) was investigated, where the transition to the faster current increase in the terms of Fowler-Nordheim (FN) coordinates occurs. At low electric fields (less than 10⁷ V/cm) the CV characteristics may be described by the FN formula for the emission current and can be used to estimate the effective barrier height, which is important in selecting a good cathode material.

Abstract: The aim of the presented work is to establish relationship of behavior of stress relaxation process in 5056 alloy in vacuum conditions for stress levels of 116 MPa, 83 MPa and 50 MPa and temperatures of 293 K and 353 K. Method of circular specimens with equal flexural strength was used as the main method for stress relaxation testing. Results of the studies allowed to develop the advanced methodology for evaluation of stress relaxation, which increases measurement accuracy up to 0.04 MPa. Increase of accuracy was achieved using the proposed new shape of a specimen of equal flexural strength, its manufacturing technology and developed design of accessories for precision marking. It was established that for studied temperatures stress relaxation in vacuum is occurring more intensively independently from level of initial stress. That fact can be explained by increase of influence of dislocation mechanism on stress relaxation. The results of the presented studies serve as a basis for increase of reliability and consistency of dimensions of elements of aircraft's structure and their parts and components, which are operating in vacuum conditions.

Abstract: In Pb-free Al-Sn welding of electrolytic parts, single-crystal Sn whiskers easily form and can cause problems such as short circuits. Here we report that the growth of Sn whiskers in the weld zone of Al electrolytic condenser leads was suppressed in a vacuum environment. We examined the effect of the environment and weld metal microstructure in order to understand how to control and prevent whisker growth. In vacuum, the weld zone did not form whiskers after more than 100 h, whereas in air, whiskers grew within several hours. This suggests that whiskers require oxygen to form. The growth can be explained by the energy balance between the potential energy of the weld metal and the surface energy of the whisker. Our results will contribute to developing techniques for suppressing the formation of Sn whiskers during the percussion welding of Al electrolytic capacitor leads.

Abstract: The consolidation of the painting layer or plane and carved gildings which represent different types of detachments is an essential operation for the preservation and restoration of the cultural goods of polychrome wood. Our paper focuses on testing a new type of acrylic binder applied on cracks with blind detachments with an OMRON nebulizer with NE-C28P compressor which sprays microparticles of 3 μm under a hermetic film that covers the operated surfaces. The experiments have been performed on samples of old gilded wood. The results are compared to those obtained by using the traditional process of peliculization of the acrylic binder over the detached surfaces and with the process of spraying. The analysis techniques used are the optical microscope and SEM-EDX.

Abstract: In this paper, the calculation software HSC indium mine under vacuum carbothermal reduction reaction during the Gibbs free energy. The result show that when the pressure of 10-100Pa and temperature is 380-449K, In₂O₃ and C reaction to reaction thermodynamic conditions under pressure from the same system, material In₂O₃: C mole ratio is 1:3, needed to generate elemental In reaction temperature is the lowest. In₂O₃ generated In₂O thermal decomposition, with the loss of the system pressure, the initial reaction temperature from 1247K to 10Pa for 423K; Intermediate In2O pyrolysis generating elemental In, when the system pressure drop to 10 Pa, starting temperature dropped to 781K; InO reaction with products CO, as the system pressure is reduced, the gibbs free energy increase, therefore, step-down to InO reaction with CO. This study to provide experimental evidence for preparation of indium by carbothermic reaction of indium ore in vacuum. Keywords: Indium ore;Carbon thermal reduction;Vacuum; Thermodynamics;Introduction

Abstract: In this paper, TiC powders have been prepared under vacuum condition using titanium dioxide powders and charcoal powders as raw materials. The impacts of temperature and holding time on TiC were studied. The results show as follows: the products will absorb lots of heat and transform into titanium oxide with lower valence with the increasing of holding time at the same temperature and at last be converted into titanium carbide. At a higher temperature, the time of the product transforms into single-phase titanium carbide is shorter.

Abstract: TiC powders have been prepared with titanium dioxide and charcoal powders as raw materials by vacuum carbothermal reduction technique. Meanwhile the as-prepared TiC powders were characterized by acid corrosion resistance test and oxidizability test. The results show as follows: the acid corrosion resistance of titanium carbide powders prepared at the optimum experiment conditions is better than that of industrial powders. It hardly dissolves in HCl, H₂SO₄, HNO₃, HF, HClO₄ and aqua regia, and slightly dissolves in mixed solution HF+HNO₃. The TiC powders are gradually oxidized at 352°C~917°C at air atmosphere and the product may be titanium dioxide and titanium oxides with lower valence. When the temperature rises to 546°C, a large quantity of titanium carbide powders are oxidized. And when the temperature rises to 688°C, besides the titanium carbide powders are oxidized to release heat, the free carbon is also oxidized and transformed into CO₂ gas to escape.