Papers by Keyword: High Temperature Stability

Abstract: Low specific contact resistivity and high-temperature reliability of the Ni (x)/Nb (100-x) (where x = 25, 50, 75 nm) ohmic contact to 4H-SiC were investigated. After the annealing process at 1000°C for 3 min in N₂ ambient, the I-V curves indicated that all the contacts exhibited the ohmic behaviors. Based on the transfer length method, the specific contact resistivity of the contacts were extracted. High concentration of Ni was responsible for low specific contact resistance of the Ni (75)/Nb (25)/4H-SiC sample by the formation of Ni₂Si compound after the fabrication process. However, this contact lost the ohmic behavior at low temperature of 150°C. Whereas, both Ni (50)/Nb (50)/4H-SiC and Ni (25)/Nb (75)/4H-SiC contacts remained the ohmic behavior for 100-hour aging at 400°C. Two-dimensional X-ray diffraction analyses showed that the presence of carbon agglomeration formed at the interface of the Ni (75)/Nb (25)/4H-SiC contact caused the degradation of this sample when being aged at high temperature environment. Meanwhile, higher concentration of Nb in the Ni (50)/Nb (50)/4H-SiC and Ni (25)/Nb (75)/4H-SiC samples improved the ability to collect the excess carbon atoms and thus enhanced the high temperature reliability of these contacts when operating in high temperature ambient. Considering both low specific contact resistivity and high temperature reliability, the Ni (50)/Nb (50)/4H-SiC contact can be a good candidate for harsh environment applications.

Abstract: The microstructure stability and the effect of microstructure evolution on the properties of Super304H steel aged at 750°C for different time were investigated. The results showed that the microstructure of the Super304H steel after aging at 750°C consists of primary matrix and large amount of precipitated phases. The main precipitates were Cu-rich phase, MX phase and M₂₃C₆ carbides in austenitic matrix during aging. The M₂₃C₆ carbides precipitate preferentially at grain boundaries, and then coarsening remarkably with increasing aging time. The MX phase was stable during the whole aging process. The Cu-rich particle is smaller than 10 nm at the initial aging stage, and then coarsen with increasing aging time. The strength and hardness increase obviously at the initial stage due to the interaction of Cu-rich phase, MX phase and M₂₃C₆ carbides precipitation strength, in which Cu-rich phase strengthen action is the dominant. Coarsening M₂₃C₆ carbides weaken the strength during aging.

Abstract: This review focuses on the recent developments of high temperature stable anatase TiO₂ photocatalyst. Eventhough TiO₂ exists in different forms anatase, rutile and brookite, anatase phase stabilization is often the key to obtain the highest photocatalytic performance for TiO₂, particularly for the use as an antibacterial and self-cleaning coatings in high temperature processed ceramics. Different methods available for the anatase stabilization in literature are critically reviewed and emphasis is placed on relatively recent developments. Currently available methods of anatase stabilizations are classified in to four categories viz (i) doping with metal ions (ii) doping with non-metal ions (iii) co-doping with metal and non-metal ions and (iv) dopant free stabilization by oxygen richness. Further to this, the application of these high temperature stabilized anatase TiO₂ photocatalyst on various ceramics substrates such as tile, glass and sanitary wares as self-cleaning and antibacterial coatings are also been briefly discussed.

Abstract: The stability of SiC and SiO₂ in helium with little water vapor is studied in this paper in order to confirm whether they can service as anti-oxidation layers on the surface of fuel elements of high temperature gas-cooled reactor (HTR) under water-ingress accident. Through thermodynamic analysis, it is found that the influence factor controlling the critical temperature of passive oxidation for SiC in He-H₂O is the partial pressure of H₂O; the critical temperature of passive oxidation for SiC increases with the partial pressure of H₂O. The influence factors controlling the critical temperature of decomposition for SiO₂ are the partial pressure of H₂O and the amount of H₂O in gas for 1 mol SiO₂, the critical temperature of decomposition for SiO₂ increases with the partial pressure of H₂O while it decreases with the amount of H₂O in gas for 1 mol SiO₂. SiO₂/SiC composite coating is more suitable than SiC coating in He-H₂O with little H₂O.

Abstract: Anti-rut agent, named RPS-3000,was added into AC-25 asphalt mixture and its effects on high temperature stability, low temperature cracking resistance, water damage resistance and fatigue life were investigated in this paper. Results showed that the high temperature stability and low temperature crack resistance of the asphalt mixture improved significantly, the water damage stability increase slightly due to the introduction of anti-rut agents. Besides, the result of fatigue life test presented that excess amount of anti-rut agent may lead a deterioration of fatigue life. Keywords: Anti-rut agent; High temperature stability; Asphalt mixture

Abstract: High temperature stability of asphalt mixture is one of asphalt pavement major performance which concerns the permanent deformation of the pavement. Four different gradations were used to detect the mixture high temperature stability, dynamic stability or short for rut distortion for regress time was obtained from regression for the data of rutting test, and the test indicates that either of these two indexes can better characterize high temperature stability of asphalt mixture.

Abstract: Three kinds of combination schemes were designed about SMA-13 asphalt mixture. They were basalt aggregate SMA, limestone aggregate SMA, basalt and limestone aggregate SMA. Through the study of low temperature and high temperature test of three kinds of combination, the low temperature performance of basalt and limestone aggregate SMA was better than that of the basalt aggregate SMA; and the high temperature performance was in between, thus providing important experimental data for the limestones replacing basalt in SMA pavement.

Abstract: The high temperature stability of SMA is affected by many factors. Some factors that may affect the high temperature stability of SMA (stone mastic asphalt) analyzed by the way of Marshall and rutting testing, in the laboratory. The results show that the high temperature stability of SMA is closely related to its gradation,asphalt content,testing temperature,the number of rolling. This paper will only discuss the above factors. Study results indicated that adding proper coarse aggregate (diameter4.75mm ) and mine dust contents would play occluding and wedging role in aggregate mixture. The rolling times of SMA asphalt mixture should be Strictly controled, in order to improve the compaction density. When the experiment temperature was increased up to 67°C, high-temperature stability of SMA can not meet the requirement of standards. The optimal dosage of asphalt in rutting test is 5.0%, which is more 0.3%~0.4% than that in marshell-test. Key words: road engineering; SMA; rutting testing; Marshell test; high temperature stability

Abstract: Rutting is one of the most hazardous damage form of asphalt pavement.But,owing to itself inherent in the viscoelastic characteristics of asphalt mixture,the diversity of factors influencing the high temperature of asphalt pavement anti-rutting performance and the complexity of rut formation,this three reasons make ruts become a worldwide problem.Starting from the mixture.This article analyzed the influence factors of the rutting resistance of asphalt mixture at high temperature.For asphalt mixture, through the experimental data, the research status at home and abroad, from the type of asphalt, asphalt content, grading of aggregates and air voids four aspects analysis and study the influence factors of the stability of asphalt mixture at high temperature.

Abstract: The pavement performance of AC-20 asphalt mixture added with certain polyester fiber or the anti-rut agent are studied in this paper. By analyzing the high temperature stability and water stability of asphalt mixture through the indoor test, it can be concluded that: after adding polyester fiber and anti-rut agent, the pavement performance of asphalt mixture has the remarkable enhancement, it can be better adapted to our heavy traffic requirements.