protective layers
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Author(s):  
Yonas Tesfamhret ◽  
Reza Younesi ◽  
Erik J. Berg

Abstract Transition metal (TM) dissolution from oxide cathode materials is a major challenge limiting the performance of modern Li-ion batteries. Coating the cathode materials with thin protective layers has proved to be a successful strategy to prolong their lifetime. Yet, there is a lack of fundamental understanding of the working mechanisms of the coating. Herein, the effect of the most commonly employed coating material, Al2O3, on suppressing hydrofluoric acid(HF)-induced TM dissolution from two state-of-the-art cathode materials, LiMn2O4 and LiNi0.8Mn0.1Co0.1O2, is investigated. Karl Fischer titration, fluorine selective probe and inductively coupled plasma optical emission spectrometry are coupled to determine evolution of H2O, HF and TM concentrations, respectively, when the active materials come in contact with the aged electrolyte. The coating reduces the extent of TM dissolution, in part due to the ability of Al2O3 to scavenge HF and reduce the acidity of the electrolyte. Delithiation of the cathode materials, however, increase the extent of TM dissolution, likely because of the higher vulnerability of surface TMs in +IV oxidation state towards HF attack. In conclusion, the current study evidences the important role of acid-base reactions in governing TM dissolution in Li-ion batteries and shows that coatings protect the cathode towards an acidic electrolyte.


2022 ◽  
pp. 134688
Author(s):  
Mangwei Cui ◽  
Boxun Yan ◽  
Funian Mo ◽  
Xiaoqi Wang ◽  
Yan Huang ◽  
...  

2021 ◽  
Vol 1 (4) ◽  
Author(s):  
Mehran Jaberi Zamharir ◽  
Mohammad Zakeri ◽  
Mansour Razavi

In this study, the UHTC-based composite layers where applied on the graphite substrates using SPS method to protect them against ablation. The protective layers had some defects and problems such as crack, fracture, separation, melting, and weak adhesion to the substrate. Several factors such as the thickness of composite layer, the number of protective layers, the SPS conditions (temperature, applied pressure, soaking time and mold), the chemical composition of the layers, the type of the substrate and the mismatch between the thermal expansion coefficients of the substrate and the applied layer(s) affected the quality and connection of the protective layer to the graphite substrate. The amount of additive materials influenced the melting phenomenon in the composite layer; for example, further MoSi2 in the layer led to more melting. The mismatch between the thermal expansion coefficients of the graphite substrate and the composite layer caused stresses during the cooling step, which resulted in cracks in the applied layer. Hence, proximity in the thermal expansion coefficients seems to be necessary for the formation of an acceptable adhesion between the layer and the substrate.


2021 ◽  
Vol 11 (6-S) ◽  
pp. 195-205
Author(s):  
Mandeep Singh ◽  
Dhruv Dev ◽  
D.N. Prasad

Delivery of the drug to the ocular area is blocked by the protective layers covering the eyes; it has always been a major problem to find effective bioavailability of the active drug in the ocular area due to the short duration of precorneal majority ocular stay. Direct delivery systems combine as well as oil, solution, and suspension, as a result, many delivery systems are not able to effectively treat eye diseases. Many works have been done and are being done to overcome this problem one of which is to use in-situ to build polymeric systems. Ocular In-situ gelling systems are a new class of eye drug delivery systems that are initially in solution but are quickly transformed into a viscous gel when introduced or inserted into an ocular cavity where active drugs are released continuously. This sol-to-gel phase conversion depends on a variety of factors such as changes in pH, ion presence, and temperature changes. Post-transplanting gel selects viscosity and bio-adhesive properties, which prolongs the gel's stay in the ocular area and also releases the drug in a long and continuous way unlike conventional eye drops and ointments. This review is a brief overview of situ gels, the various methods of in situ gelling systems, the different types of polymers used in situ gels, their gel-based methods, and the polymeric testing of situ gel. Keywords: In-situ gel, Polymers, and ion triggered in-situ gel, Mechanism, Evaluation parameters


Materials ◽  
2021 ◽  
Vol 14 (21) ◽  
pp. 6501
Author(s):  
Fatima Ghassan Alabtah ◽  
Elsadig Mahdi ◽  
Marwan Khraisheh

In this study, we report on the corrosion behavior of hybrid steel/glass fiber-reinforced polymer (GFRP) composite pipes under harsh corrosive conditions for prolonged durations. Specimens were immersed in highly concentrated solutions of hydrochloric acid, sodium chloride, and sulfuric acid for durations up to one year. Detailed qualitative analysis using scanning electron microscopy (SEM), X-ray diffraction analysis (XRD), and energy-dispersive X-ray spectroscopy (EDX) is presented. It is shown that the hybrid pipes have excellent corrosion resistance with a corrosion rate of less than 1% of the corrosion rate for conventional steel pipes. That low corrosion rate can be attributed to the formation of pores in the GFRP layer due to increased absorption and saturation moisture in the material with increased soaking time. This can be reduced or even prevented through a more controlled process for fabricating the protective layers. These promising results call for more utilization of GFRP protective layers in novel design concepts to control corrosion.


Author(s):  
Vladimir TRAVUSH ◽  
Yuri VOLKOV

With the development and simplification of The article describes the application of European norms in the domestic practice for the design of reinforced concrete structures using European norms Eurocode-2. For Eurocode-2, the number of nationally defined parameters is more than a hundred. These are different coefficients, shrinkage, creep of concrete, thickness of protective layers of concrete for steel fittings depending on the type, environment of operation, etc. Differ in the SNIP on the design of designs and individual Eurocodes, the size and shape of the samples tested to determine the strength (regulatory) characteristics of building materials, making it impossible to apply many of the calculation formulas directly. Addressing these issues is a rather capacious task. Many series of prototypes will be required only to determine statistically reliable transitional coefficients for the strength of the materials used in SNIP and Eurocodes.


2021 ◽  
Vol 4 (2) ◽  
Author(s):  
Daniel Kohls ◽  
Carlos Enrique Ninõ Bohorquez ◽  
Enori Gemilli ◽  
Majorie Anacleto Bernardo

With the use of laser welding, it is possible to join different steel, with different thicknesses, with or without the action of protective layers. The quality of laser radiation makes it possible to get certain characteristics that are impossible to get by other processes, such as high welding speeds, less metallurgical effects suffered by the heat-affected zone (ZAC), and this process also does not require filler metal, therefore it is free from possible contamination. Combined with traditional welding methods, laser welding produces narrower weld beads, allowing for better prevention of corrosion and thermal distortions. Although the process already has high industrial knowledge, some random defects, such as porosities and inconsistencies, are still found. This work presents a systematic study to determine the influence of laser welding parameters and how these parameters influence welding defects. For this, the experimental part was carried out in the welding laboratory - LABSOLDA, of the Federal University of Santa Catarina - UFSC, during the laser welding processes, a welding speed of 2.4 m/min was reached. For this experiment, argon was used as a shielding gas and 1020 steel was used as the base material.


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