Papers by Keyword: Thermal Aging

Abstract: Investigating the dielectric characteristics and structural alterations in XLPE composites, commonly employed in the insulation of covered conductors, stands as a pivotal research focus. In this study, we examined the variation in dielectric loss (tanδ) concerning frequency and voltage, influenced by thermal aging in XLPE insulation. To achieve this, the samples underwent aging at 120°C for six periods, a total of 450 hours. Furthermore, we conducted PD tests, FTIR, and SEM assessments on the insulation both before and after the aging process. A comprehensive analysis of the material's property changes during thermal aging was performed by comparing the PD test results with the tanδ measurements. In order to delve deeper into the interpretation of these findings because of thermal aging, we explored both internal and surface structural modifications, which directly impact tanδ and PD values, utilizing FTIR and SEM techniques.

Abstract: The aim of the article is to highlight the effect of the environment on the properties of a polycarbonate (PC). It consists in aging this material under Ultra-violet (UV) combined with temperature for different periods of time, and to reveal the physicochemical and mechanical changes caused by aging. PC is a highly valued technical material for its various important characteristics and low cost. It finds its application in various fields but mainly in those whose requirements are the transparency and the impact resistance. The physicochemical and mechanicals characterizations of the marketed polycarbonate are necessary in order to highlight its intrinsic properties and to develop strategies that can improve its lifespan. In this work, we highlight the physicochemical and mechanical characteristics of virgin and aged polycarbonate. For this, analytical techniques and mechanical tests were used. A comparison of the characteristics revealed the combined effects of temperature and ultraviolet rays.

Abstract: In this paper, the influence of some ingredient concentrations such as SBR ratio, DCP/S, CBS/DPG accelerator, EPDM-g-AM and cord surface on mechanical, thermal aging properties and adhesion between rubber compounds and cord have been investigated. The results showed that with suitable ingredients loading such as EPDM/SBR is 85/15 phr, DCP/S is 2.0/1.5 phr and EPDM-g-AM content is 2.0 phr with respect to rubber, the vulcanizates had good mechanical properties, thermal stability and adhesion level to the zinc/copper galvanized cord. The highest tensile strength, elongation at break and pull out strength reached 18.1 MPa, 432% and 60.3 N/mm respectively, and the highest retention after thermal aging at 150°C for 168 hours was about 0.76.

Abstract: The cleanness of the wafer backside is vital in improving process quality and device yield for advanced technology nodes, 10, 7 nm, and beyond [1,2]. Defects such as particles and scratches on the wafer backside could be sources of local deformation of a wafer [2], causing the photolithography hotspot generation [3], the local variation of film thickness, wafer breakage, so on. The micron-size particle defects are easily generated during deposition, etch, CMP processes, and they can be easily transferred to subsequent processing tools. The particles will be exposed to various process conditions such as high compressive stress and high temperature, and it can be seen on the end-effector and wafer chuck in the process chamber. In order to make the wafer backside clean, we need to understand the behavior of particle adhesion and removal, especially at high temperature. In this paper, the adhesion behavior of aged particles at high temperature and the footprint of them were studied.

Abstract: Electron beam welding produces very narrow and deep penetration therefore it finds application where welding of thick materials is required. AISI 321 is susceptible to intergranular corrosion when it is used in high temperature and harsh conditions, owing to the Titanium depletion in the weld zone. However, the heat affected zone formed in electron beam welding extends to a narrow region across the weld pool. In the present study electron beam welding of austenitic 321 stainless steel is done to examine the mechanical and metallurgical properties of the joints. Microhardness tests along and across the weld bead were carried out. Tensile and impact tests were performed to analyze mechanical properties. The microstructures of the weld zone, fusion zone and base metals were also captured. Skeletal ferrites were seen in the weld metal. The aging treatment of 700°C for 24 hours which resulted in a change in morphology of the grains from skeletal to vermicular and promoted the formation of Ti-rich carbides on the grain boundaries. The maximum impact toughness at sub-zero temperature i.e. -40°C was recorded as 129.3 J in as-welded samples and it got reduced to 119.5 J after aging treatment. The average ultimate tensile strength was 582 N/mm² and it got decreased to 481 N/mm² after aging treatment.

Abstract: In this paper, the influence of paraffinic oil on the physical mechanical, thermal and adhesion properties of three blends of EPDM Buna EP T.6465, Keltan 5260Q and Keltan 6160 D and CIIR have been investigated. The results showed that the tensile strength values and elongation at break of keltan 5260Q/CIIR and keltan 6160 D/CIIR with 10 wt.% paraffinic oil represent the improvement of 57.8%, 57.6% and 71% to 81% respectively, compared with one without oil. The mean peel force of EPDM keltan 6260D with 10% oil loaded is about 36% and 32.5% higher than that of EPDM keltan 5260Q and EP.T 6465 blends respectively. With suitable oil content, in this case is 10% wt., the thermal resistance of keltan 5260 Q and 6160D seems to be higher than that of without processing oil and suitable for thermal resistance rubber application.

Abstract: The microstructure evolution during aging at high temperatures is usually used to thermodynamically simulate those cases of aging at low temperatures but for a very long time for P92 steel, because high temperature can accelerate the microstructure process. Therefore, in the present research, in order to comprehensively understand the microstructure evolution mechanisms during aging at especially high temperatures, the as-tempered P92 steel was exposed at 790 °C. Optical microscopy (OM), scanning electron microscopy (SEM) and transmission electron microscopy (TEM) were employed to characterize the microstructures. The dominant mechanisms at the four stages in microstructure evolution process during thermal exposure are (I) dislocation annihilation, (II) lath broadening and equiaxed subgrain nucleation, (III) equiaxed subgrain growth, (IV) recrystallization nucleation and growth. The martensitic lath broadening is dominated by both the motion of “Y”-type lath boundary and the combination of parallel lath boundary. The subgrain growth is by virtue of both the combination of the equiaxed subgrain and the bowing out of subgrain boundary.

Abstract: The stress corrosion cracking (SCC) sensitivity of aged Z3CN20.09M stainless steel (SS) was investigated by scanning electrochemical microscopy (SECM), nanoindenter and slow strain rate tensiometer (SSRT). The results indicated that the hardness and modulus of the samples increased with increasing aging time at 475 °C, which increased about 80% and 15% respectively after aging for 1000h. After immersed in NaCl+HCl solution (pH=2) for 7 h, the pitting corrosion point appeared of specimen aged for 1000h. While it was not found even for 24 h of as-received (AR) and aged for 500 h specimens at the same condition. The SCC sensitivity was increased about one time of the specimen aged for 1000 h tested in 300 °C high temperature water. The combined effect associated the embrittlement of mechanical properties and the decrease of corrosion resistance is regarded as the main reason for the increasing of SCC sensitivity.

Abstract: The UK Advanced Gas Cooled nuclear reactor fleet adopted CO₂ gas as the heat transfer medium. Over the plant service life carbon diffuses into the stainless steel components as part of the overall oxidation process. This carbon enrichment promotes carbide precipitation and changes overall microstructure, thereby altering temperature deformation and fracture behaviour. Due to difficulties of replicating the high temperature/high pressure CO₂ service environment, many tests are conducted under simulated CO₂ conditions. We compare the role of a range of surrogate atmospheres on steel test specimens to one which failed in service to establish the influence of testing atmosphere on creep deformation and fracture characteristics.

Abstract: The present study was conducted to obtain a better understanding of the variation rule of mechanical properties of laminated neoprene bridge bearing pads under thermal aging condition using compression tests. A total of 5 specimens were processed in a high-temperature chamber. After that, the specimens were tested subjected to axial load. The parameter mainly considered time of thermal aging processing for specimens. The results of compression tests show that the specimens after thermal aging processing are more probably brittle failure than the standard specimen. Moreover, the exposure of steel plate, cracks and other failure phenomena are more serious than the standard specimen. The compressive capacity, ultimate compressive strength, compressive elastic modulus of the laminated neoprene bridge bearing pads decreased dramatically with the increasing in the aging time of thermal aging processing. The attenuation trends of ultimate compressive strength, compressive elastic modulus of laminated neoprene bridge bearing pads under thermal aging condition accord with power function. The attenuation models are acquired by regressing data of experiment with the least square method. The attenuation models conform to reality well which shows that this model is applicable and has vast prospect in assessing the performance of laminated neoprene bridge bearing pads under thermal aging condition.