Surface Analysis of Surface Finished Aluminum Alloys with a Low Outgassing Property
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Optimized mechanical grinding (OMG) was developed as a low outgassing surface finishing for aluminum alloys (A5052). Surface morphology and depth profile for aluminum alloys with four types of surface finishes, i.e. conventional mechanical grinding (MG), mechanical grinding with optimized process (OMG), combination of mechanical grinding and chemical polishing (MG+CP) and combination of optimized mechanical grinding and chemical polishing (OMG+CP), were investigated using Atomic force microscopy (AFM) and X-ray photoelectron spectroscopy (XPS). The surfaces of MG and MG+CP were rough, whereas OMG and OMG+CP were smooth. The composition of the surface layer of MG was composed of Al2O3 and γ–AlOOH, whereas OMG, MG+CP, and OMG+CP was composed of Al2O3. Therefore, OMG was considered to have low outgassing property due to the smooth surface and thin surface oxide layer compose of Al2O3, which were originated from the small surface alteration by the processing.Keywords:
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This paper aims at studying the effect of polishing parameters on surface roughness by using the cloth wheel polishing process. Stainless steel was used as a specimen in this study. The investigation firstly accounted for the comparison between two polishing compounds, and the best one was used to be applied in a set of experiment. The effect of spindle speed, current and polishing time on the surface roughness of stainless steel was examined, and the results showed that polishing time and current played the significant role in degree of roughness. The optimum condition under the range of parameters considered in this work was determined, whose surface roughness was about 0.0466 μm.
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Our earlier studies centered on understanding the incipient failure mechanism in polyethylene (PE) as an insulation material. The results simulated conditions not measured in routine manufacturing or electric utility test procedures. These findings indicated that detectable changes with pure PE can occur on the surface of cavities (artificially produced), as observed by X-ray photoelectron spectroscopy (XPS). Because the prior studies were done with pure PE and cavities that were made for easy XPS analysis, the question remained "would the findings from the earlier inquiry be relevant to materials used by the electrical utilities?" To answer this question PE insulation was analyzed from a series of commercial type cables that had undergone long-term testing. Occasionally oxygen was found by XPS on the interior surfaces of the more highly stressed PE cable samples. The estimated amount of oxygen was lower than that often found previously. The oxygenated carbon species were similar to those found previously, i.e., alcohols and/or ethers and carbonyls. Some outgassing, probably hydrocarbons, of the FE was observed. The role, if any, of these outgassing components on the failure of PE as an insulation material is unclear.
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Carbon fibers
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This paper presents a new outgassing test facility based on the difference method, which is a rarely used modified throughput technique. Furthermore, the experimental approach presented is validated based on new measurement data for three relevant materials. The facility allows to measure at a good resolution thermal outgassing rates at variable temperatures between room temperature and 300 °C. The measurement approach is discussed, the facility is described, and the measurement uncertainty is evaluated. Three materials were measured to demonstrate the new experimental approach and to compare the results obtained for stainless steel 316L and two polymers, Viton® and Vespel®. For stainless steel 316L, the influence of different pretreatments was analyzed. It was found that by baking in vacuum as well as in air (400 °C, 100 h), the outgassing rate can be reduced by almost a factor of ten, in line with predictions based on outgassing theory. The polymers were investigated, as they represent materials with quite large outgassing rates. This was confirmed, especially when they were measured as received, without baking. In general, the difference method for measuring thermal outgassing was found to work well in a wide range of outgassing rates.
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Processing of many materials at high temperatures requires a high purity environment. The outgassing from hot surfaces of the processing chamber or the heating elements is a potential problem. The total amount of outgassing as well as the time- and temperature- dependent outgassing rates are important. The outgassing from Haynes Alloy 214 has been studied experimentally under a vacuum in the temperature range from room temperature to 600 °C. In addition to the outgassing rates, the composition of the outgassed species was determined through mass spectrometric analysis. Alloy surface composition was determined by x-ray photoelectron spectroscopy. Changes in surface composition before and after heating can be accounted for by the outgassed species.
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The outgassing of packaging materials is one of the direct threats to the vacuum acquisition and maintenance of vacuum electronic devices, so its accurate measurement is of great significance to improve the quality and life of devices. However, the background leakage and outgassing of the sample chamber have a non-negligible impact on the measurement results. The outgassing rate that can be measured by traditional testing devices is generally high, and it is difficult to accurately measure the vacuum outgassing rate of packaging materials with low outgassing rates. In order to solve this problem, we develop an apparatus for measuring the vacuum outgassing rate of materials based on constant conductance method and symmetrical measurement structure, and propose a background outgassing compensation method to extend the lower limit of the outgassing rate that can be measured.
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Vacuum level
Ultra-high vacuum
Leakage (economics)
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Outgassing, the evolution of gas from the material in a vacuum, is not only a source of micro contamination in a semiconductor or the flat display panel production process, but it also a limitation factor in the ultra clean process of nano-technology. The outgassing from the materials of satellites and spacecrafts must be controlled for increased safety and function because space is also a vacuum environment. Several methods are used in outgassing measurement in general, but there is no one method suitable for obtaining all outgassing data. The most suitable method for a particular application must be chosen by the experimenter or user. Three types of outgassing measurement systems were fabricated and characterized, ‘Throughput method,’ ‘Rate of Rise method’ and ‘Mass Loss Measurement method’. The outgassing rates of many kinds of materials were measured and characterized using these systems.
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Sections of solar panel and reflector were charged in a 25-keV electron beam. The measured outgassing and discharge rates varied coincidentally, indicating that outgassing is a contributing cause of discharges. Some dependence of outgassing on ESD (electrostatic discharge) was observed during the test. Large discharges resulted in sharp instantaneous increases in the outgassing rate. Outgassing then quickly stabilized to its predischarge level and continue to follow a downward trend. This suggests that outgassing depends on ESD on a short-term (transient) basis and that the overall outgassing pattern is not changed by ESD. These facts led to the conclusion that outgassing is likely to be the cause rather than the effect of the discharge.< >
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Ultra-high vacuum
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