δ-MnO 2 nanofibers, synthesized by using a simple, low-cost solgel method, showed high electrochemical performance as a cathode for rechargeable Al-ion batteries (AIBs). δ-MnO 2 presented an initial discharge capacity of 59 mA h g À 1 and stabilized at 37 mA h g À 1 at a current rate of 100 mA g À 1 after 15 cycles and for more than 100 cycles with almost a 99 % coulombic efficiency. Different plateaus in charge/discharge curves, consistent with CV peaks, revealed the Al-ion insertion/ deinsertion and the electrochemical stability of the battery. Moreover, different rate CV measurements revealed the pseudocapacitive behavior of δ-MnO 2 in AIBs. The obtained charge/discharge capacities are ten times higher than previous studies performed with this material. Ex situ Raman and highresolution TEM measurements in different charge/discharge states revealed structural information of δ-MnO 2 upon Al-ion intercalation/deintercalation.

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A set of multiphase manganese‐oxide composite materials (Mn2O3@Mn3O4 and Mn3O4@Mn5O8), and a birnessite‐type KxMnO2 oxide are prepared and evaluated as cathodes for Zn‐ion batteries. The species formed when the electrodes are subjected to 2 V in aqueous solutions of MnSO4 and ZnSO4 are analyzed, suggesting an interphase activation leading to enhancement of electrochemical response. For the first time, it is shown that a Zn4(SO4)(OH)6.xH2O phase coats the composite‐type electrodes in the charging stage, contributing to extending the lifetime of the batteries. KxMnO2 electrode with layered birnessite structure shows long cycling life at low current densities (122 mAh g−1 at 30 mA g−1 after 50 cycles) and good efficiencies (ca. 99%) in the 0.1 Mn2+ electrolyte. In contrast, in the 0.5 m Mn2+ electrolyte, high values of specific capacity are delivered by the cell at higher rates, that is, 150 mAh g−1 at 600 mA g−1. In Mn5O8@Mn3O4 the good performance is due to the synergistic effect of the two compounds forming the composite. Thus, after more than 100 cycles this composite displays specific capacity values of 175 mAh g−1 at 2150 mA g−1 in the 0.1 m Mn2+/1 m Zn2+ electrolyte.

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This paper addresses the development of an equipment to teach control engineering fundamentals. The design requirements were determined by users that perform academic, research and industrial training tasks in the area of dynamic systems and process control. Such requirements include: industrial instrumentation; measurement of controlled and manipulated variables, and disturbances; process reconfigurability; different control technologies; several control strategies; appropriate materials for visualization; and compact shape to optimize lab space. The selected process is a tank system that allows one to choose among several dynamic behaviors: first, second, and third order, linear and nonlinear behavior, and dead time; the mathematical model that represents the dynamics of the system is presented. A traditional 3-stage design methodology that includes conceptual, basic and detailed design was followed. The developed equipment allows the user to select from three different technological alternatives to control the system: a PLC, an industrial controller, and a computer. With such flexibility, several control strategies can be implemented: feedback, feedforward, PID, LQG, nonlinear control (gain scheduling, sliding mode, etc.), fuzzy logic, neural networks, dynamic matrix control, etc. The developed system is being used to teach undergrad courses, grad courses, and industrial training. Additionally, the equipment is useful in research projects where grad students and researches can implement and test several advanced control techniques.

KxMnO2 materials with birnessite-type structure are synthetized by two different methods which make it possible to obtain manganese oxides with different degrees of crystallinity. The XPS results indicate that the sample obtained at high temperature (KMn8) exhibits a lower oxidation state for manganese ions as well as a denser morphology. Both characteristics could explain the lower capacity value obtained for this electrode. In contrast, the sample obtained at low temperature (KMn4) or by hydrothermal method presents a manganese oxidation state close to 4 and a more porous morphology. Indeed, in this case higher capacity values are obtained. At current density of 30 mA g−1, the KMn8, KMn4, and HKMn samples display a capacity retention of 88, 82, and 68%, respectively. The higher capacity loss obtained for the HKMn compound could be explained considering that the incorporation of Zn2+ in the structure gives rise to the stabilization of a ZnMn2O4 spinel-type phase. This compound is obtained in the discharge process but remains in the charge stage. Thus, when this spinel-type phase is obtained the capacity loss increases. Moreover, the stabilization of this phase is more favorable at low current rates where 100% of retention for all samples, before 50 cycles, was observed.

Electrochemical activity of different MnO2 phases as electrodes of aluminium-ion batteries (AIBs) is studied. For this purpose, different simple synthesis routes have been carried out to obtain different structures and morphologies: rod-like with tunnelled structure (α-MnO2) and hexagonal micro-pellets with lamellar structure (δ-MnO2). α-MnO2 showed an outstanding capacity (Q) of 120 mA h g-1 at current densities of 100 mA g-1, which remained stable after 100 cycles with efficiencies over 90%. δ-MnO2 showed a good Q of 80 mA h g-1 at current densities of 50 mA g-1 after 50 cycles with efficiencies over 95%. Moreover, cyclic voltammetry (CV) measurements at different rates allowed for a better understanding of the electrochemical behaviour and revealed the contribution relation of diffusive and capacitive-controlled mechanisms in the corresponding AIB system. In addition, cyclic voltammetry (CV) measurements at different rates allowed a kinetic study of the diffusive and capacitive-controlled mechanisms. Conclusions were obtained regarding the dimensionality of α-MnO2 (1D) and δ-MnO2 (2D) and their electrochemical behaviour in AIBs.

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