Papers by Keyword: Degradation Mechanism

Abstract: Shift reactors are widely used in the petroleum and chemical industries, and especially in the coal chemical plants. The degradation of the reactor is critical to the safe operation of coal chemical plant. In this paper, a shift reactor after 8 year service was chosen. The test block taken from the reactor cylinder with the stainless steel clad plate was used and the test samples from the test block were prepared. And then, chemical composition analysis, metallographic examination, tensile and hardness tests were performed. The scanning electron microscopy (SEM), energy dispersive spectroscopy (EDS) and X-ray diffraction (XRD) method were used to study the degradation and degradation mechanism of the reactor. The metallographic analysis results show that there were a large number of carbides segregated in the grain boundary and the intergranular cracks were observed for the samples in the weld zone of the stainless steel clad plate. The SEM and EDS results indicate that the corrosion medium (i.e. polythionic acid) was found in the fracture surface of the samples from the weld zone of the stainless steel clad plate. The XRD test results show that the tensile residual stress occurred for the welding of the stainless steel clad plates. It is found that the degradation mechanism of the shift reactor was due to the polythionic acid stress corrosion cracking.

Abstract: F, the most electronegative element, is easy to catch the electrons in the bonds to form the stabilized C-F. Perfluorinated acids have high chemical stability which can tolerate acid, alkali, etc. Inhibition effect was observed in the complex pollution system in which 7 kinds of perfluorinated acids existed simultaneously. The formation of hydrated electrons was the rate-limiting step in complex pollution system, and the inhibition was increased as the carbon chain increasing. Compared the reduction rate of perfluorinated acids by photo-induced hydrated electrons in the complex pollution system with the single rate, the results showed that there were positive linear correlations between the degradation rate and photo-induced hydrated electrons. The degradation multiples of perfluorinated acids were studied, it concluded that, because of the competition among the 7 kinds of perfluorinated acids, the degradation rates were influenced.

Abstract: To solve the problem of the limitation to improve device performance in standard Si integration technologies and to develop radiation-harsh devices, the irradiation effects of Si_1-xC_x source/drain (S/D) n-type metal oxide semiconductor field effect transistors (n-MOSFETs) have been investigated. It is shown that the drain current and the maximum electron mobility of Si_1-xC_x n-MOSFETs decrease by electron irradiation. The reduction of the device performance can be explained by the radiation-induced lattice defects in the devices. However, the electron mobility enhancement effect by adding C remained after an electron irradiation up to 5×10¹⁷ e/cm².

Abstract: Cement Asphalt Mortar (CAM) layer is the key to the structure of slab track in the high-speed railways. In the running of high-speed railways, the CAM layer must bear the action of temperature change, initial defects and trains loading, it will lead to the degradation of CAM. This paper designed the experiments to study its mechanical property under confining pressure or water erosion, tensile property, fatigue property, interface stress of CAM and concrete roadbed; it will help us to establish the failure criterion and degradation model of CAM layer. Preliminary experiment chose three confining pressures to study the mechanical property of CAM; the results indicate that peak stress and ductility of CAM greatly increase with increase of confining pressure.

Abstract: A new polytriazoleimide (PTAI) was prepared from 1,2,3-triazole-containing diamine and 4,4’-(hexafluoroisopropylidene) diphthalic anhydride by polycondensation. The thermal stability was investigated. The PTAI was pyrolyzed at 400 °C and 750 °Cseparately and the pyrolysis was traced by the Py/GC/MS combined technique. Nitrogen and related compounds which result from the cleavage of C-N and N-N bonds in the polymer are found in the pyrolysis products at 400 °C. The further decomposition of PTAI would take place at imide rings and the chain units between imide rings at 750 °C. A degradation mechanism of the PTAI is proposed.

Abstract: Due to the drought climate and over grazing, the grassland degrades severely recently, which not only influences local environment, but also threatens ecology safety of northern areas. Urgently control of degraded grassland and prevent advanced deterioration are needed. Recently, irrigation plays vital role on the recovery of degraded grassland in northern pastoral areas. Different amount irrigation experiment (adequate and moderate irrigation) was carried out from 2007 to 2009 on Xilamuren Grassland, Inner Mongolia. The experiment plots vegetation quantitative characteristics were investigated during 2007～2011. Compared with no irrigation plot, it’s concluded that: ① Different irrigation amount have the same effect on improving the production and biodiversity during irrigation. ② When stopped irrigation, the production and biodiversity of the two ever irrigated plots degraded more and faster than the non irrigation plot equally. ③ Moderate irrigation can save more water while recovering degraded grassland satisfactorily. To keep stable, the irrigation amount and times should be decreased gradually.

Abstract: Under ultraviolet radiation, the photocatalytic degradation mechanism of Butyl enzyl phthalate ester (BBP) was studied with TiO₂ as the catalyst. As a result, BBP could be degraded efficiently, and the efficiency was 85% after 6h degradation. During the degradation process, the acidity of the degradation system changed obviously. The initial pH of the solution was 6.0, and it increased to 6.23 after 15min degradation, however it decreased to 3.89 after 6h degradation. Some photodegradation intermediates in the different photocatalytic steps were examined and analyzed by means of GC-MS. For the BBP, the photocatalytic degradation firstly reacted on the benzyloxy chain, and new material occured by the recomposition of the educts in the degradation.

Abstract: In our country, corn straw is byproduct of agricultural products and its output is quite great. So, through microbial technology, degradation of corn straw which has high fiber and lignin has important economical values and environmental significance. This paper summarizes general regulations of biodegradation of corn straw, through several main microflora.

Abstract: Other than open micropipes (MP), overgrown micropipes do not necessarily lead to a^significantly reduced blocking capability of the affected SiC device. However they can lead to a degradation of the device during operation. In this paper the physical structure of overgrown micropipes will be revealed and their contribution to the leakage current will be shown. The possible impact of the high local power dissipation in the surrounding of the overgrown micropipe will be discussed and long term degradation mechanisms will be described. Failure simulation under laboratory conditions shows a clear correlation between the position of overgrown micropipes and the location of destructive burnt spots.

Abstract: Carbon nanotubes have attracted considerable attention because their high aspect ratio leads to a large electric field enhancement and a low operating voltage. The dependence of environmental gases such as Ar, O2 on the emission current from carbon nanotube emitters was examined in this study. Based on our experiments, the current density is decreased in single-wall carbon nanotubes (SWNTs), but is increased in multi-wall carbon nanotubes (MWNTs) as the vacuum level decreases from 10-7 Torr to 10-4 Torr by the inflow purging gases. The current density subsequently recovered as the vacuum level increased to 10-7 Torr when gas inflow stopped. From those results, we conclude that the MWNTs have completely different degradation characteristics in comparison to SWNTs. The increased current density of an MWNT in the high-pressure range of 10-4 Torr is a significant finding and would be widely applicable to low cost vacuum packages.