Investigating the activity of Ca2Fe2O5 additives on the thermochemical energy storage performance of limestone waste.

Efficient and reliable energy storage systems are necessary to address the intermittency and variability of renewable energy sources. Thermochemical energy storage (TCES) has emerged as a promising solution for long-term renewable energy storage, with limestone being a widely studied material due to its abundance and high energy density. However, the practical implementation of limestone-based TCES systems faces challenges related to performance degradation upon multiple energy storage/release cycles, impacting their long-term viability and efficiency. In this study, we investigate the activity of Ca2Fe2O5 additives on the thermochemical energy storage performance of limestone waste. Ca2Fe2O5 additives were synthesized by a wet precipitation method using three different Ca/Fe molar ratios and added to limestone waste in a 5, 10, and 20 weight concentration. The synthesized samples were characterized using XRD, SEM, EDS, BET, and XPS techniques. The thermal properties and heat storage performance of the samples were evaluated through thermogravimetric analysis of calcination/carbonation cycling experiments. The results demonstrate the potential of Ca2Fe2O5 additives to improve the cycling stability and energy storage density of limestone-based TCES systems. The sample with 5 wt% of Ca2Fe2O5 additive having Ca : Fe molar ratio of 1 : 1 outperformed all samples with an effective conversion rate of 0.21 after 40 cycles, 1.31 times higher than limestone waste.

Femtosecond Laser Assisted Crystallization of Gold Thin Films.

We propose a novel low temperature annealing method for selective crystallization of gold thin films. Our method is based on a non-melt process using highly overlapped ultrashort laser pulses at a fluence below the damage threshold. Three different wavelengths of a femtosecond laser with the fundamental (1030 nm), second (515 nm) and third (343 nm) harmonic are used to crystallize 18-nm and 39-nm thick room temperature deposited gold thin films on a quartz substrate. Comparison of laser wavelengths confirms that improvements in electrical conductivity up to 40% are achievable for 18-nm gold film when treated with the 515-nm laser, and the 343-nm laser was found to be more effective in crystallizing 39-nm gold films with 29% improvement in the crystallinity. A two-temperature model provides an insight into ultrashort laser interactions with gold thin films and predicts that applied fluence was insufficient to cause melting of gold films. The simulation results suggest that non-equilibrium energy transfer between electrons and lattice leads to a solid-state and melt-free crystallization process. The proposed low fluence femtosecond laser processing method offers a possible solution for a melt-free thin film crystallization for wide industrial applications.

Crystallographic Characterisation of Ultra-Thin, or Amorphous Transparent Conducting Oxides-The Case for Raman Spectroscopy.

The electronic and optical properties of transparent conducting oxides (TCOs) are closely linked to their crystallographic structure on a macroscopic (grain sizes) and microscopic (bond structure) level. With the increasing drive towards using reduced film thicknesses in devices and growing interest in amorphous TCOs such as n-type InGaZnO 4 (IGZO), ZnSnO 3 (ZTO), p-type Cu x CrO 2 , or ZnRh 2 O 4 , the task of gaining in-depth knowledge on their crystal structure by conventional X-ray diffraction-based measurements are becoming increasingly difficult. We demonstrate the use of a focal shift based background subtraction technique for Raman spectroscopy specifically developed for the case of transparent thin films on amorphous substrates. Using this technique we demonstrate, for a variety of TCOs CuO, a-ZTO, ZnO:Al), how changes in local vibrational modes reflect changes in the composition of the TCO and consequently their electronic properties.

Importance of Local Bond Order to Conduction in Amorphous, Transparent, Conducting Oxides: The Case of Amorphous ZnSnOy.

In this report, reactive and nonreactive sputtering of amorphous ZnSnOy (a-ZnSnOy) was investigated, and extensive composition maps have been measured by X-ray photoelectron spectroscopy. The comprehensive analysis of the ((ZnO)x(SnO2)1-x) composition reveals that the best Zn/Sn ratio for high conductivity of the material can vary depending on the deposition technique utilized. Best conductivities of 225 S/cm were found to occur at x = 0.32 for reactive sputtering of a Sn target and x = 0.27 for nonreactive sputtering of a SnO2 target. These values correspond to unstable polymorphs of a-ZnSnOy, ZnSn2O5, and ZnSn3O7. Distinct local bonding arrangements have been confirmed by Raman spectroscopy.

Measurement of deposition rate and ion energy distribution in a pulsed dc magnetron sputtering system using a retarding field analyzer with embedded quartz crystal microbalance.

A compact retarding field analyzer with embedded quartz crystal microbalance has been developed to measure deposition rate, ionized flux fraction, and ion energy distribution arriving at the substrate location. The sensor can be placed on grounded, electrically floating, or radio frequency (rf) biased electrodes. A calibration method is presented to compensate for temperature effects in the quartz crystal. The metal deposition rate, metal ionization fraction, and energy distribution of the ions arriving at the substrate location are investigated in an asymmetric bipolar pulsed dc magnetron sputtering reactor under grounded, floating, and rf biased conditions. The diagnostic presented in this research work does not suffer from complications caused by water cooling arrangements to maintain constant temperature and is an attractive technique for characterizing a thin film deposition system.

Pulsed-Plasma Physical Vapor Deposition Approach Toward the Facile Synthesis of Multilayer and Monolayer Graphene for Anticoagulation Applications.

We demonstrate the growth of multilayer and single-layer graphene on copper foil using bipolar pulsed direct current (DC) magnetron sputtering of a graphite target in pure argon atmosphere. Single-layer graphene (SG) and few-layer graphene (FLG) films are deposited at temperatures ranging from 700 °C to 920 °C within <30 min. We find that the deposition and post-deposition annealing temperatures influence the layer thickness and quality of the graphene films formed. The films were characterized using atomic force microscopy (AFM), scanning electron microscopy (SEM), high-resolution transmission electron microscopy (HRTEM), Raman spectroscopy, X-ray photoelectron spectroscopy (XPS), and optical transmission spectroscopy techniques. Based on the above studies, a diffusion-controlled mechanism was proposed for the graphene growth. A single-step whole blood assay was used to investigate the anticoagulant activity of graphene surfaces. Platelet adhesion, activation, and morphological changes on the graphene/glass surfaces, compared to bare glass, were analyzed using fluorescence microscopy and SEM techniques. We have found significant suppression of the platelet adhesion, activation, and aggregation on the graphene-covered surfaces, compared to the bare glass, indicating the anticoagulant activity of the deposited graphene films. Our production technique represents an industrially relevant method for the growth of SG and FLG for various applications including the biomedical field.

Protection and functionalisation of silver as an optical sensing platform for highly sensitive SPR based analysis.

Silver thin films are well known as the most sensitive material for surface plasmon resonance (SPR) based analysis. However, the use of silver for this purpose is limited by three main issues, namely poor adhesion to plastic substrates, chemical instability in both air and aqueous environments and hence the difficulty in functionalizing the silver coated substrate for immobilizing biomolecular ligands by conventional liquid phase methods. In this work, we have successfully addressed these problems using gas-phase coating processes. We demonstrate highly adherent sputter-deposited silver coatings on low cost polymer substrates using a sputter-deposited thin gold adhesion layer. The problems of chemical instability and functionalisation have been addressed by using the gas phase process of plasma enhanced chemical vapour deposition (PECVD) to deposit thin films with a base SiO(x)C(y)H(z) layer (using tetraethyl orthosilicate precursor) functionalised with carboxylic acid (from sequential deposition with acrylic acid precursor). The resultant coating serves as a protective layer against degradation of the optical properties of silver under long term storage and use in ambient conditions. The reactive carboxyl functionality is used for the covalent immobilization of biomolecules. The successful stabilisation and functionalization of silver films on plastic sensor chips is demonstrated by mouse IgG immunoassays. The expected superior performance of the silver thin films over gold thin films for SPR analysis is demonstrated.