Binder and Conductive Diluents Free NaVPO4F Based Free-standing Positive Electrodes for Sodium-Ion Batteries

Herein, we report a carbon-fiber based freestanding electrode for NaVPO4F cathodes in sodium-ion batteries. The replacement of conventional aluminum foil with a carbon fiber mat-based current collector results in significant improvement in capacity at high rates and charge-discharge cycle stability. Petroleum-pitch (P-Pitch) has dual functions. P-pitch is used as a binder to bind NaVPO4F particles onto the carbon fiber mat, which helps to eliminate typical organic binders. At the same time, P-Pitch acts as a conducting precursor to coat onto NaVPO4F particles. The amount of P-pitch required to achieve stable electrochemical performance is optimized. As a result, 15 and 20 % of P-pitch in the composite NaVPO4F electrodes (15P_NVPF@CF and 20P_NVPF@CF) shows stable electrochemical performances. A reversible capacity of 120 and 119 mAh g−1 are observed for 15P_NVPF@CF and 20P_NVPF@CF, with 97 and 98 % retention in capacity after 300 cycles, respectively. Further, at a 0.5 C current rate, 15P_NVPF@CF and 20P_NVPF@CF electrodes show 86 and 87 % capacity retention after 1000 cycles. The significant electrochemical performance of these freestanding electrodes is ascribed to the interlinked carbon matrix with NaVPO4F particles and carbon-fiber mat, which provides a continuous path for electronic conduction and faster kinetics of NaVPO4F particles

Cyclic Tension Induced Pattern Formation on [001] Single-Crystal Aluminum Foil

Cyclic tension of (100)[001]-oriented single-crystal aluminum foils with the frequency 5 Hz forms a tweed pattern. Its period is several microns and increases by a factor of 1.5 in the temperature range 233–363 K. A model is proposed for structural relaxation of the medium on spatial and time meso- and macroscales under cyclic loading. Conditions under which a steady pattern forms are found based on the analysis of kinetic equations. The number of bands in the steady pattern is found to be related to the strain rate. The process activation energy is determined.

Paper-based Triboelectric Nanogenerator and Activities of Salt Ions

This work presents a triboelectric nanogenerator (TENG) fabrication using polytetrafluoroethylene, aluminum foil, and cellulose paper. Mechanical interactions lead to atomic defects that stimuli the delocalized electrostatic charge carriers and kinetic energy. The addition of ionic salt’s microdroplets improved the TENG’s performance. Eventually, surface charge activities have escalated the electrical signals. Further, studied spontaneously increased charge transport performance at the steady-state condition in the presence of NaCl ionic droplets. We considered that these ionic activities actively participated in detecting salt ions.

Ultrasonic Tomography Study of Metal Defect Detection in Lithium-Ion Battery

Lithium-ion batteries are widely used in electric vehicles and energy storage systems. Sudden fire accident is one of the most serious issue, which is mainly caused by unpredicted internal short circuit. Metal particle defect is a key factor in internal short circuit it will not show an obvious abnormal change in battery external characteristic just like mechanical and thermal abuse. So, a non-destructive testing of battery internal metal defect is very necessary. This study is first time to scan and analyze different types of defects inside a battery by using ultrasonic technology, and it shows the detection capability boundary of this methodology. A non-contact ultrasonic scanning system with multi-channel was built to scan the battery sample with aluminum foil, copper foil and copper powder defects. The position and shape of those defects were clearly shown by using tomography methodology. It was found that the acoustic properties difference between metal defects and battery active materials has a strong influence on detection sensitivity. Compared with aluminum foil, copper foil and copper powder are easier to be detected and change the ultrasonic signal greatly, they will produce an obvious shadowing artifacts and speed displacement phenomena in tomography images. Ultrasonic tomography technology is an effective method for non-destructive testing of lithium-ion batteries.

Improving the Specific Surface Area of Etched Aluminum Foil by Fabricating the Micro/Nano Structure

Aluminum foil with micro/nano structure has been prepared by electrochemical DC etching and a subsequent anodization treatment followed by removal of the alumina film. When the micron-sized tunnels were generated on the etched aluminum foil, the size and distribution of the nano-concave formed on the sidewall of the etched tunnels varied with the anodized time in H2SO4 and C4H6O6 electrolyte. The optimal value of the specific surface area for the aluminum foil with micro/nano structure is approximately four times larger than that of the only etched aluminum foil. It is indicated from the chronoamperometry and BET measurements that the specific capacitance of aluminum foil with micro/nano structure can be significantly improved by suitable anodization in H2SO4 electrolyte, in comparison with a comparatively small increasement in C4H6O6 electrolyte. This can be attributed to the fact that the tardy anodization process will consume a considerable amount of aluminum substrate, resulting in the aggravation of the merged tunnels.

Determination of Galendo’s Shelf Life on Various of Storage Temperatures by Arrhenius Method

This study aims to estimate the shelf life by applying the Arrhenius formula model to "galendo" which is vacuum packed and stored at various temperatures. Estimation of the shelf-life limit of galendos was carried out by measuring the peroxide number and sensory values ​​of galendos which were deliberately kept open without being packed at room temperature (25 ○C). The sensory values ​​used as the threshold for consumer rejection of the level of galendo's rancid odor were achieved on the 27th day of storage and the current peroxide count value was 42.2724 meq/kg. Galendo which was vacuum packed with aluminum foil and stored at various temperatures of 15 ○C, 25 ○C, and 35 ○C, then the shelf life was determined using the Arrhenius and Q10 models based on the parameters of the total peroxide number (TPN) and the total microbial content. Based on the experiment in this study, the estimation results of galendo's shelf life based on the total peroxide number (TPN) test parameter show that storage at 15 ○C has a shelf life of 83 days with a deterioration rate (k) of 0.0207, storage at 25 ○C shelf life 67 days with a deterioration rate (k) 0.0247, and storage at a temperature of 35 ○C for 58 days with a deterioration rate (k) 0.0286. The rate of quality degradation with a value of Q10 (15 oC - 25 oC) of 1.23 and a value of Q10 (25 oC - 35 oC) of 1.16. The higher the storage temperature, the higher the microorganism content.

Electrochemical Improvement of the MWCNT/Al Electrodes for Supercapacitors

An original technique of chemical deposition (CVD) by catalytic pyrolysis of ethanol vapor was used to directly grow multiwall carbon nanotubes (MWCNTs) layers on aluminum foil. The grown nanotubes had excellent adhesion and direct electrical contact to the aluminum substrate. This material was perfect for use in electrochemical supercapacitors. In this work, the possibility of a significant increase in the specific capacity of MWCNTs by simple electrochemical oxidation was investigated. The optimal conditions for improving the characteristics of the MWCNT/Al electrodes were found. Electrochemical treatment of MWCNT/Al electrodes in a 0.005 M Na2SO4 solution at a potential of 4–5 V for 20–30 min increased the specific capacity of MWCNTs from 30 F/g to 140 F/g. The properties of modified nanotubes were investigated by X-ray photoelectron spectroscopy, cyclic voltammetry (CV), and impedance spectroscopy. A significant increase in the concentration of oxygen-containing functional groups on the surface of MWCNTs was found as a result of electrochemical oxidation. The modified MWCNT/Al electrodes maintained excellent stability to multiple charge–discharge cycles. After 20,000 CVs, the capacity loss was less than 5%. Thus, the results obtained significantly expanded the possibilities of using MWCNT/Al composite materials obtained by the method of direct deposition of carbon nanotubes on aluminum foil as electrodes for supercapacitors.

Experimental Study of the Behavior of Phase Change Materials during Interrupted Phase Change Processes

This research article explores the behavior of a phase change material (PCM) when it undergoes interrupted melting and freezing, through experimental investigations using a heat flow meter apparatus. A fatty acid-based organic PCM, encapsulated within polyethylene and thin aluminum foil layers, was experimentally tested in this study. Experiments were designed to represent multiple interrupted phase change scenarios that could occur within PCMs applied in buildings. The experimental results were analyzed and compared with previously reported assumptions in numerical models dealing with PCM hysteresis and interrupted phase change processes. These comparisons indicated that the assumptions used in the different numerical models considered can capture the interrupted phase change phenomena with varying degrees of accuracy. The findings also highlighted the need for additional experimental research on different phase change processes that can occur in building applications of PCMs.

Structure and characteristics of a thin-layer "aluminum - carbon nanotubes" sandwich structure

The study describes a way to produce thin-layer sandwich structures containing layers of aluminum foil and an interlayer filler of carbon nanotubes (CNTs). To obtain a homogeneous structure of the composite, induction heat treatment was used combined with a device providing primary compression of the assembly. To determine the functional characteristics of sandwich structures, the homogeneity of their microstructure and surface conductivity were studied. It was found that the use of CNTs allowed increasing the surface conductivity by a factor of 8.3–9.5 compared to the sandwich structure without filler.