This work investigates the microstructure evolution during the rotary friction welding (RFW) of Inconel 718 alloy. A cellular automata (CA) approach is implemented to evaluate a cylindrical component (at weld center and edge wall), predicting dynamic recrystallization (DRX) and grain size of friction welds. The input variables for RFW were rotational speed (500, 1000, and 1200 rpm), feed rate (2 mm/s), and feed distance (3.6 mm). The CA model is based on the Laasraoui-Jonas model and explains intricate grain transformation in terms of microstructure, temperature, strain, and strain rate. Calculated grain consists of very fine grain structure at the stir zone followed by the thermo-mechanical affected zone, where partial recrystallized microstructure was present. The average grain size was 2.5 µm, which is comparable to reported experimental values. The grain analysis revealed that temperature and strain are most affecting factors to attain a refined microstructure. The strain rates predicted for both center and edge locations of the weld were found to be higher as rotational speed increased. A steady strain distribution is noted at greater temperature for all the rotational speeds. The results of this work contribute toward the understanding of microstructure and mechanical response for RFW of Inconel 718.

VOPO ₄ ·2H ₂ O was synthesized and investigated as an electrode material for electrochemical supercapacitors. The electrochemical characterizations were performed in three different electrolytes (3M LiNO ₃ , 3M KOH and 3M LiOH). Ion intercalation is shown by extracting the charge of the double layer, pseudocapacitive and faradaic processes from cyclic voltammograms. This takes place across the entire applied potential window even at scan rates as high as 100 mV.s ⁻¹ . However, the amount of charge related to each mechanism depends on the nature of the electrolyte. The highest areal capacitance is 500 μ F cm ⁻² (70 Fg ⁻¹ ) in 3M LiOH. Moreover, after an initial fade the capacitance stabilizes at 90% of the starting value after 5000 cycles, thus opening a new use of transition metal phosphates as electrodes for energy storage devices.

Mn₅(H₂O)₄(PO₃OH)₂(PO₄)₂ with an open 3D network was prepared and studied as electrode material for electrochemical capacitors. The material exhibits a tunnel structure along the c axis, characterized by a hydrogen bond network formed by water molecules bonded to MnO₆ octahedra and PO₃-OH tetrahedra units, the latter containing an acidic proton. Electrochemical studies were conducted on both alkaline and neutral electrolytes, revealing a profile indicative of a rapid faradaic process coupled with pseudocapacitance and electrochemical double-layer capacitance. This study proposes a mechanism that involves the interaction between the acidic proton in the tunnel structure and OH⁻ ions from the electrolyte, which diffuse through the hydrogen bond network. The material achieved a maximum specific capacitance of 184 Fg⁻¹ at a scan rate of 5 mVs⁻¹, with an areal capacitance of 4600 µFcm⁻² in 3M KOH. This demonstrates its potential as a high-performance electrode for energy storage applications.

In the present work two layered vanadium phosphates were prepared, VOPO ₄ • CTAB and K _0.5 VOPO ₄ • 1.5H ₂ O as electrode materials for electrochemical capacitors. These materials contain different molecular species in their interlayer space leading to an electrochemical behavior that drastically differs from the crystalline phase VOPO ₄ • 2H ₂ O, with water molecules in the interlayer space. In the case of VOPO ₄ • CTAB, it was found that CTAB molecules block the pathway of electrolyte ions into the crystalline structure avoiding an intercalation/deintercalation process. In the case of K _0.5 VOPO ₄ • 1.5H ₂ O, the K ⁺ ions from the crystalline structure hinder the intercalation/deintercalation process leading around 73 and 71 percent of the charge arise from a capacitive process in 3 M LiOH and 3 M KOH, respectively.