Effect of swift heavy ion irradiation on surface resistance of DyBa2Cu3O7−δ thin films at microwave frequencies

We report the observation of a pronounced peak in surface resistance at microwave frequencies of 4.88 GHz and 9.55 GHz and its disappearance after irradiation with swift ions in laser ablated DyBa2Cu3O7−δ (DBCO) thin films. The measurements were carried out in zero field as well as in the presence of magnetic fields (up to 0.8 T). The films were irradiated using 90 MeV oxygen ions at Nuclear Science Centre, New Delhi at a fluence of 3 × 10^13 ions/cm2. Introduction of point defects and extended defects after irradiation suppresses the peak at 9.55 GHz whereas no suppression is observed at 4.88 GHz. These results and the vortex dynamics in the films at microwave frequencies before and after irradiation are discussed

New low-cost, flow-through carbon electrodes characterized in brackish water

We propose a simple and low-cost flow-through electrode for electrochemical cells used for instance in capacitive desalination. We have coated macro-porous carbon fiber papers with various loads of carbon microporous particles to combine both a high surface area and an open structure for good fluid dynamics. In this first study, we restrict our investigation to the charging/discharging behavior, the identification of side reactions, and the effect of geometry on the diffusion of ions. The electrochemical performance was first investigated by cyclic voltammetry and galvanic charge-discharge techniques. The specific capacitance increases by three orders of magnitude upon adding the carbon particles. Then, electrochemical impedance spectroscopy revealed the presence of charge transfer phenomena and modification in the mass transport by the diffusion process for the coated electrode.Funding Agencies|Swedish Government Strategic Research Area in Materials Science on Advanced Functional Materials at Linkoping University; Linkoping University; [VR 2016-05990]; [KAW 2018.0058]; [P52023-1]; [2009-00971]</p

Dip-coated hydrotungstite thin films as humidity sensors

Thin films of a hydrated phase of tungsten oxide, viz. hydrotungstite,have been prepared on glass substrates by dip-coating method using ammonium tungstate precursor solution. X-ray diffraction shows the films to have a strong b-axis orientation. The resistance of the films is observed to be sensitive to the humidity content of the ambient,indicating possible applications of these films for humidity sensing. Ahome made apparatus designed to measure the d.c. electrical resistance in response to exposure to controlled pulses of a sensing gas has been employed to evaluate the sensitivity of the hydrotungstite films towards humidity

Enhanced thermoelectric figure of merit in nano-structured Si dispersed higher manganese silicide

Higher manganese silicide (HMS) is considered as a promising thermoelectric material at intermediate temperatures. Samples of Si-rich HMS were prepared by arc melting followed by ball milling combined with densification by an induction hot uni-axial pressing (HP) and spark plasma sintering (SPS), respectively. Powder X-ray diffraction, SEM and EPMA studies confirmed the presence of Si in HMS matrix. TEM micrographs on milled powders further confirmed the presence of Si particles with an average size of ~5–10 nm in HMS matrix. Microstructure investigations on densified samples revealed that SPS process seems to be a beneficial tool for embedding the nanostructures of Si (~20–50 nm) particles in HMS matrix. SPS also controls the grain growth of HMS during densification, which in turn reduces the total thermal conductivity from ~4.4 W/m.K to 2.10 W/m.K. On the other hand, samples processed by HP showed the value of ~2.44 W/m.K with similar sintering parameters as in SPS used for densification. Huge reduction in lattice thermal conductivity of about ~55%, and a considerable increase in Seebeck value was observed in Si-rich BMed HMS. However, reduction in electrical conductivity associated with insulating Si particles in HMS matrix limited the zT to ~0.26 at 725 K

Effect of co-substitution of Mn and Al on thermoelectric properties of chromium disilicide

CrSi2 was earlier reported to be an interesting thermoelectric material for high temperature applications because of its high oxidation resistance and good mechanical properties. In order to enhance its figure of merit, Mn at Cr site and Al at Si site were substituted into CrSi2. Our results indicate that Cr1-x Mn (x) Si2-x Al (x) solid solutions exhibit significantly lower thermal conductivity and a higher figure of merit than CrSi2

Effect of Sulfonation Level on Lignin/Carbon Composite Electrodes for Large-Scale Organic Batteries

The key figure-of-merit for materials in stationary energy storage applications, such as large-scale energy storage for buildings and grids, is the cost per kilo per electrochemical cycle, rather than the energy density. In this regard, forest-based biopolymers such as lignin, are attractive, as they are abundant on Earth. Here, we explored lignin as an electroactive battery material, able to store two electrons per hydroquinone aromatic ring, with the targeted operation in aqueous electrolytes. The impact of the sulfonation level of lignin on the performance of its composite electrode with carbon was investigated by considering three lignin derivatives: lignosulfonate (LS), partially desulfonated lignosulfonate (DSLS), and fully desulfonated lignin (KL, lignin produced by the kraft process). Partial desulfonation helped in better stability of the composite in aqueous media, simultaneously favoring its water processability. In this way, a route to promote ionic conductivity within the lignin/carbon composite electrodes was developed, facilitating the access to the entire bulk of the volumetric electrodes. Electrochemical performance of DSLS/C showed highly dominant Faradaic contribution (66%) towards the total capacity, indicating an efficient mixed ionic-electronic transport within the lignin-carbon phase, displaying a capacity of 38 mAh/g at 0.25 A/g and 69% of capacity retention after 2200 cycles at a rate of 1 A/g

Thermoelectric properties of chromium disilicide prepared by mechanical alloying

CrSi and Cr1-x Fe (x) Si particles embedded in a CrSi2 matrix have been prepared by hot pressing from CrSi1.9, CrSi2, and CrSi2.1 powders produced by ball milling using either WC or stainless steel milling media. The samples were characterized by powder X-ray diffraction, scanning, and transmission electron microscopy and electron microprobe analysis. The final crystallite size of CrSi2 obtained from the XRD patterns is about 40 and 80 nm for SS- and WC-milled powders, respectively, whereas the size of the second phase inclusions in the hot pressed samples is about 1-5 mu m. The temperature dependence of the electrical resistivity, Seebeck coefficient, thermal conductivity, and figure of merit (ZT) were analyzed in the temperature range from 300 to 800 K. While the ball-milling process results in a lower electrical resistivity and thermal conductivity due to the presence of the inclusions and the refinement of the matrix microstructure, respectively, the Seebeck coefficient is negatively affected by the formation of the inclusions which leads to a modest improvement of ZT

Self-Discharge in Batteries Based on Lignin and Water-in-Polymer Salt Electrolyte

Lignin, the most abundant biopolymer on earth, has been explored as an electroactive material in battery applications. One essential feature for such lignin-based batteries to reach successful usage and implementation, e.g., large-scale stationary grid applications, is to have slow self-discharge characteristics on top of the essential safety and life-cycle properties. Water-in-polymer salt electrolytes (WIPSEs) have been demonstrated as an attractive route to solve this issue; however, little has been done to understand the fundamentals of actual self-discharge mechanisms. Herein, the impact of some critical chemical and physical parameters (pH, dissolved oxygen, viscosity, and cutoff potential) on self-discharge of batteries based on WIPSE and lignin has been investigated. The pH range is crucial as there is an interplay between long-term stability and high energy density. Indeed, lignin derivatives typically store relatively more charge in acidic media but later promote corrosion affecting device stability. A robust and high-performing organic battery, incorporating potassium polyacrylate as WIPSE, is demonstrated, which expresses good self-discharge behavior for a broad range of pH and with little impact on the atmosphere used for manufacturing. It is believed that the investigation will provide critical insights to the research community to promote the advancement of printed large-scale energy storage devices.Funding Agencies|Knut and Alice Wallenberg (KAW) foundation [KAW 2019.0344, KAW 2020.0174]; Swedish Research Council [2016-05990]; Swedish Government Strategic Research Area in Materials Science on Functional Materials at Linkoping University [2009-00971]; KAW</p