What Happens to MnO2 When It Comes in Contact with Zn2+? An Electrochemical Study in Aid of Zn/MnO2-Based Rechargeable Batteries

In the science and technology of electrochemical energy storage, different allotropes of MnO2, fabricated with a variety of methods, are assembled into electrodes, playing the role of cathode or oxygen reduction reaction (ORR) electrocatalyst. Often, MnO2-based cathodes are combined with Zn anodes into different types of batteries, resulting in contact between MnO2 and its electrochemical reaction products, and Zn2+. Awareness is growing that this interaction adversely affects the functional performance of MnO2, but no definitive understanding has been reached for this issue. This study contributes, through electrochemical measurements accompanied by microscopy and Raman spectroscopy, to a better understanding of the way the electrochemical behavior of two technologically representative types of manganese dioxide - hydrothermally grown α-MnO2 and electrodeposited γ-MnO2 (EDM) - is degraded when these materials are exposed to neutral and alkaline aqueous solutions, containing Zn2+. Specifically, we highlighted different types of irreversible changes in electrochemical response, which can be interpreted with phase-formation processes. Such changes result in the deactivation of α-MnO2 as ORR electrocatalyst, and of both α-MnO2 and EDM as zinc-ion battery (ZIB) cathodes. The electroactivity of EDM for ZIB operation can be restored if Mn2+ is added to the neutral electrolyte, because a phase, active in discharge, is electrodeposited during charging

PROCESS AND APPARATUS FOR THE MEASUREMENT OF THE HARDNESS AND FOR THE SELECTION OF AGRICULTURAL PRODUCTS

Method for measuring the hardness of agricultural products comprising the operations of: - implementing a test program suitable for identifying and selecting one or more indices (S3, S4) which can be measured with a non-destructive test on a respective product/fruit, correlated with the hardness (Du) of the same product/fruit, measured by a respective penetration test; - calculating the coefficients that define the straight line representative of the linear correlation between said indices and the hardness for the respective product. The method is implemented with the operations of: - applying on the product a dynamic force, preferably of impulsive type; - detecting the mechanical reaction through at least a piezoelectric transducer capable of generating an electric signal based on the application or transmission of said dynamic force through the respective kiwi fruit; - analyzing said electric signal relative to the fruit, and measuring the crossing time of said dynamic force through the same kiwi fruit; - calculating the value of the index S4 of said dynamic force through the fruit. It was found that the S4 index has a very significant correlation with the hardness of the respective kiwi fruit, and that the coefficients of the relative correlation straight line are respectively a = -1.5084, and b = 0.0072

Piezoelectric transducers for real-time evaluation of fruit firmness. Part I: Theory and development of acoustic techniques

This paper presents a non-destructive method for evaluating the firmness of fruits. Three novel stiffness indexes based on acoustic methods and involving Young's modulus and sound propagation velocity are proposed. The theoretical background leading to their formulation from physical considerations is presented. The effectiveness of the considered indexes is tested by means of an experimental setup built with two piezoelectric transducers contacting several samples of kiwifruits during their ripening process. The dependency on the geometrical position of the contact and the robustness against simplifying assumptions, such as uniform density or roundness, is investigated. The obtained experimental results show that stiffness indexes based on propagation delays are more rapid and reliable than those based on fruit resonance in assessing the ripeness degree

Piezoelectric transducers for real-time evaluation of fruit firmness. Part II: Statistical and sorting analysis

This paper presents a statistical method for the calibration of an acoustic technique for the real-time evaluation of fruit firmness. The technique uses an experimental setup based on two standard piezoelectric transducers and exploits two novel stiffness indexes developed in the first part of this paper. Extensive experimental measurements show good correlation (r = 0.930, R^2 = 0.865) between the proposed non-destructive test and the traditional destructive Magness-Taylor test. An evaluation of the statistical significance (t-test) of the obtained regression model parameters has been performed and validates the method. The presented sorting analysis complements the physical detection techniques presented in the first part of the paper, allowing to classify individual kiwifruits with high accuracy and high prediction rate ( 3c90%). The technology is suitable for industrial real-time and in-line applications aiming to improve warehouse stock management and market stock uniformity