Micro-recycling of spent Ni-Cd batteries for the obtention of electrocatalytic coatings

A micro-recycling approach was explored to produce catalytic metallic coatings for the hydrogen evolution reaction (HER). For this aim, discarded Ni-Cd batteries were employed as raw material. After dismantling the batteries, the active powder material, containing Cd and Ni compounds, was leached in a solution containing citric acid and hydrogen peroxide. The dissolved metals were electro-deposited on copper plates using a two electrodes cell at the following potentials (mV): -1900, -2000, and -2100 mV. The CdNi coating produced at -2000 mV, contained 92.6 % Cd and 7.4 % Ni. This coating was studied by cyclic voltammetry (CV) and potentiodynamic analysis in two different KOH solutions (0.1 M and 1.0 M). The CV analysis showed that the CdNi electrode was electrochemically stable in a wide operating voltage range (between oxygen evolution reaction and HER). Using an uncompensated resistance correction, the Tafel slopes for HER were obtained. The potentiodynamic analysis revealed that the synthesized CdNi electrode showed a catalytic activity for HER just 25.5 % smaller than the correspondent response of a standard pure Ni electrode. Our results serve as a proof of concept about the application of micro-recycling of spent batteries to produce sustainable electroactive catalytic materials for hydrogen production.

Enhanced Field Emission of Single-Wall Carbon Nanotube Cathode Prepared by Screen Printing with a Silver Paste Buffer Layer

A high emission current with relatively low operating voltage is critical for field emission cathodes in vacuum electronic devices (VEDs). This paper studied the field emission performance of single-wall carbon nanotube (SWCNT) cold cathodes prepared by screen printing with a silver paste buffer layer. The buffer layer can both enforce the adhesion between the SWCNTs and substrate, and decrease their contact resistance, so as to increase emission current. Compared with paste mixing CNTs and screen printed cathodes, the buffer layer can avoid excessive wrapping of CNTs in the silver slurry and increase effective emission area to reduce the operating voltage. The experimental results show that the turn-on field of the screen-printed SWCNT cathodes is 0.9 V/μm, which is lower than that of electrophoretic SWCNT cathodes at 2.0 V/μm. Meanwhile, the maximum emission current of the screen-printed SWCNT cathodes reaches 5.55 mA at DC mode and reaches 10.4 mA at pulse mode, which is an order magnitude higher than that of electrophoretic SWCNTs emitters. This study also shows the application insight of small or medium-power VEDs.

Light/electric modulated approach for logic functions and artificial synapse behaviors by flexible IGZO TFTs with low power consumption

In recent years, low power electronic devices have attracted more and more interests. Here, flexible thin-film transistors(TFTs) with In-Ga-Zn-O (IGZO) as semiconductor channel material were fabricated on polyethylene terephthalate (PET) substrates. The device exhibits good electrical properties at low operating voltage, including high on/off ratio of ~ 7.8 × 106 and high electron mobility of ~ 23.1 cm2V-1s-1. The device also has excellent response characteristics to visible light. With the increase of visible light intensity, the threshold voltage of IGZO TFTs decreases continuously, but the electron mobility increases gradually. Based on the unique response ability of the device to light, we proposed and demonstrated that a single thin-film transistor can realize different logic operations under the light/electricity mixed modulation, including “AND” and “OR”. In addition, we also simulated some basic artificial synaptic behaviors, including excitatory postsynaptic current and paired-pulse facilitation. Thus, IGZO TFTs operating at low voltages not only have the potential to construct multifunctional optoelectronic devices, but also provide a new idea for simplifying the design of programmable logic circuits.

Estimation of minimum operating voltage in fully depleted SOI SRAM cells using gamma distribution

Minimum operating voltages (Vmin) of every cell on a 32kb fully-depleted (FD) SOI static random access memory (SRAM) macro are successfully measured. The competing Vmin distribution models, which include the gamma and log-normal distribution, are approximated using the generalized gamma distribution (GENG). It is found that Vmin of the cells follow the gamma distribution. This finding gives a simple method to estimate worst Vmin of an SRAM macro by measuring few samples and make linear extrapolation from the gamma distribution.

Scaling behavior of ferroelectric FET with reduction in number of domains in ferroelectric layer

With the gate-length scaling, the number of domains in FeFET is reduced to a few or a single domain. In this paper, we investigate the effect of multi-domains versus few/single-domain behavior in FeFET. The abrupt polarization switching behavior of a single-domain is obtained by modifying the Preisach model in which the difference between saturation and remnant polarization (PsPr) is reduced. We show that for the same program/erase voltage, a two-times higher memory window can be achieved with single/few-domains FeFET than the multi-domain FeFET. Further, at fixed program/erase voltage, the scaling behavior shows improved variability due to increased polarization-induced vertical field with single-domain FeFET. We present an optimized device with a single-domain FeFET having a low operating voltage of ±2.4 V but with the same device performance that can be achieved for multi-domain FeFET having a higher operating voltage of ±5 V, which is highly promising for low power applications.

Design and Fabrication of a New MHD Micropump for Continuous Subcutaneous Infusion to Thalassemia Major Patients

Background: In recent decades, reducing the size of the drug delivery systems along with precise control of the amount of drug pumped, has attracted the attention of many researchers. Objectives: The slow subcutaneous infusion of the deferoxamine in thalassemia major patients during day is of vital importance either for the drug effectiveness. However, this is difficult to achieve due to the large size of the conventional infusion pumps and their high weight. Therefore, size and weight reduction of the infusion pumps are very important issues that must be well addressed. Methods: A biomedical micropump for drug solution infusion to human body based on the magnetohydrodynamic (MHD) concept is and designed, and its performance experimentally is investigated in this research. The key challenge in the fabrication of the micropump is its size, weight, bubble generation, and high operating voltage. Results: The present design is well responded to these problems. The final design operates with a 1.2 v without any bubble generation, while its size and weight are 20 × 40 × 50 mm3 and 90 grams, respectively. The size of the micropump is about 1/3 size of conventional micropump, while its weight is half of them. Conclusions: Therefore, the newly designed micropump has the ability to inject the drug solution to thalassemia major patients with a sufficient infusion rate during the day without disturbing them, so it can increase their quality of life and increase their life expectancy.