Papers by Keyword: Cyclic Stability

Abstract: In the past few years Prussian Blue Analogues (PBAs), as advanced metal organic framework compounds, have gathered a lot of attention due to its three-dimensional structural network and properties. PBAs are famous for their multitasking ability as they have shown an efficient role in scientific research and development with their excellent performance in various fields like, electrochemical sensors, photocatalysis, electrocatalysis, and energy storage applications. Apart from their high-tech productivity, PBAs also have some other advantages associated to them such as benign nature, economical and facile synthesis, extensive surface properties, higher theoretical capacity and exceptional electrochemical behavior which makes it more promising material for energy storage application. To further tune its properties according to the application of interest, the chemical modification by metal incorporation is the most commonly adopted strategy. For this purpose, the major research is done in the synthesis of bimetallic PBAs. The presence of metal atoms with different oxidation states can bring about dramatic reinforcements like finer microstructures with better crystallographic features, ultimately giving rise to more stable electrochemical behavior. In this article, we aim to list out all the bimetallic PBAs with focus on the synergistic effect of more than one metal within the structure of PBA and thorough analysis of their Electrochemical properties in energy storage applications.

Abstract: Shape memory alloys (SMAs) find use in myriad medical and engineering applications. In these applications, the functional characteristics of the materials are capitalized on. SMAs are used repeatedly over a long period of time in service. With continued usage degradation occurs in their functional properties, leading to a change in recovery strain, recovery stress, phase transformation temperatures and hysteresis. The change in the functional characteristics of the alloys is known as functional fatigue. Functional fatigue affects the performance of the alloys with the alloys losing their intended functionality. This problem is to be addressed if the alloys are to be used effectively and efficiently throughout their lifespan. It is especially important when using the alloys within the human body, where such degradation can affect the performance of the biomedical devices and, in turn, human health and life. Till date not too many researchers have explored this area in greater detail. In order thereforeto better understand this behavior, in the present study, an Ni₅₀Ti_44.7Cu_5.3 alloy wire with a d=1.43 mm and a l=100 mm was cycled (10,000) under constant stress (55 MPa) between its transformation temperatures, which were determined by DSC (without load). The effect of cycling on the shape memory properties (strain recovery, hysteresis, and transformation temperatures) after a specified number of cycles at regular intervals are considered. The results show that there is considerable difference in the properties obtained and are interpreted and discussed in detail in the paper.

Abstract: Using Co₃₅Ni₃₅Al₃₀ (at.%) single crystals the effects of crystals axis orientation and ageing at 673 K for 0.5 h in free state on superelasticity responses in compression are investigated. Ageing of these single crystals is found to result in strengthening of the high-temperature В2 phase and L1₀ martensite, twofold increasing of temperature interval of SE response and weakening of the orientation dependence and improving the cycle stability of superelasticity response. In [011]- and [123]-oriented single crystals the values of the stress hysteresis decrease a nearly threefold as compared to the quenched state. The combination of high-strength [001] crystal axis orientation and precipitation of coherent nanoscale particles leads to the best stability of SE response in aged Co₃₅Ni₃₅Al₃₀ single crystals.

Abstract: The effect of annealing treatment on the structure and electrochemical properties of LaNi4.5Co0.25Al0.25 alloy was studied by X-ray diffraction (XRD), scanning electron microscopy (SEM) and electrochemical measurement. XRD results show that the matrix phases are still LaNi5 (hexagonal CaCu5 type structure) but the intensity peaks become sharper after heat treatment. Electrochemical experiments at 301 K indicate that annealing treatment can significantly improve the discharge capacity and cyclic stability of LaNi4.5Co0.25Al0.25 alloy at suitable treatment condition. The alloy has the best discharge capacity (324.4 mAg-1) due to its composition homogenization after heat treatment at 1373 K/8 h, while the best capacity retention is about 80.12 % because of lower expansion rate and better anti-pulverization ability after heat treatment at 1273 K/8 h.

Abstract: With the increase of interest in using ultra-fine and nano-grained metals for structural purposes, the need to build on the knowledge pool regarding the response and behaviour of those metals under a mechanical load becomes more vital. However, it is well known that, especially for this type of materials such as the ECAPed and ARBed materials, the thermo-mechanical history affects the mechanical behaviour of the product strongly. Although ECAP and ARB are different techniques under the category of severe plastic deformation, similarities in their cyclic deformation response is observed from time to time. Specifically, the microstructural mechanisms involved in accommodating cyclic plastic strain in these two types of materials is seemingly comparable. The similarities arise from the similar microstructures in the majority of the volume of the bulk. In this report, the cyclic deformation response, and the related microstructural mechanisms of ECAPed copper will be discussed first and those of ARBed second. A comparison between ECAPed copper and ARBed copper will then be performed. Furthermore, the differences due to the unique features of ARBed material will be discussed. Lastly, the reasons behind the observed similarities in cyclic deformation behaviour and the related micro-mechanisms for metals process with the two different techniques will also be explored.