Alternative Materials Research Articles

Investigating the Role of Mixed Oxides for Oxygen Evolution Reaction on Iridium Oxide Electrocatalysts

Ongoing concerns over anthropogenic emissions, fossil fuel sustainability, and related geopolitical aspects point to an increasing need for cost-effective renewable fuel sources. A promising solution is the generation of hydrogen via the catalytic splitting of water, which can be achieved with the aid of proton exchange membrane (PEM) electrolyzers. Notably, the anode material in current commercially available PEM electrolyzers is typically iridium oxide. Despite its effectiveness in facilitating the oxygen evolution reaction (OER), the use of iridium oxide poses challenges due to the scarcity and high cost associated with this precious metal. As the quest for sustainable energy intensifies, ongoing research explores innovative approaches, such as the incorporation of alternative materials and catalysts, to enhance efficiency while addressing the economic and environmental concerns associated with iridium oxide. Studies have shown that incorporating mixed oxides and switching the supports for iridium oxide catalysts help lower the iridium loading while enhancing the OER performance.1,2 In this study, we investigate a series of different sputtered, mixed iridium oxides (Ta, Ti, Ir). We use a rotating disk electrode system to benchmark the catalytic activity of different loadings of mixed oxides. To measure the intrinsic activity of each catalytic active site, we use a home-built operando UV-Vis system to quantify the populations of surface species as well as track the kinetics of different redox transitions during OER. We incorporate nanoscale secondary ion mass spectrometry to probe the migration of different mixed oxide species before and after electrochemical cycling and use kelvin probe force microscopy to estimate the conductivity through the different films. In this study, we show the importance of cooperative effects between neighboring iridium oxide species and the coordination of iridium that are responsible for enhanced OER performance. These results indicate that doping modulates coverage dependent interactions at the surface, which affects both the binding energetics and populations of rate limiting intermediates. We believe this study will serve as a steppingstone for future designs of more cost-efficient PEM electrolyzers.(1) Oh, Hyung-Suk, et al. "Electrochemical catalyst–support effects and their stabilizing role for IrO x nanoparticle catalysts during the oxygen evolution reaction." Journal of the American Chemical Society 138.38 (2016): 12552-12563.(2) Zheng, Ya-Rong, et al. "Monitoring oxygen production on mass-selected iridium–tantalum oxide electrocatalysts." Nature Energy 7.1 (2022): 55-64.

Accelerated Discovery of Multi-Metallic Nanostructured Catalysts for Anion Exchange Membrane Water Electrolyzers: Oxygen Evolution Reaction

The current reliance on platinum group metals (PGMs) as electrocatalysts for the oxygen evolution reaction (OER) in proton exchange membrane (PEM) water electrolyzers, the current industry standard, presents a significant barrier to the widespread adoption of hydrogen as a clean energy carrier. The scarcity and high cost of PGMs necessitate the development of alternative materials and technologies that offer comparable performance at a reduced cost. In this context, anion exchange membrane (AEM) water electrolyzers have emerged as a promising alternative.This presentation addresses this imperative by focusing on the design and synthesis of nanostructured mesoporous multi-metallic catalysts for AEM water electrolyzers, leveraging earth-abundant materials as alternatives to the rare and expensive PGMs currently employed in PEM water electrolyzers. Transition metal oxides, sulfides, and phosphides are promising candidates to replace PGMs, given their abundance, low cost, and tunable catalytic properties conducive to high OER activity. The OER activity and durability of newly developed multi-metallic transition metal catalysts in an alkaline environment will be discussed in this presentation.Preliminary results demonstrate that the developed catalysts exhibit high OER activity, achieving a potential of <1.5 V versus RHE at a current density of 10 mA cm⁻² in 1.0 M KOH. Notably, this surpasses the performance of commercial OER catalysts in alkaline environments. Furthermore, the catalyst exhibits superior durability, with < 0.5 mV/h potential loss over 100 h durability test at 10 mA cm⁻² in 1.0 M KOH.AcknowledgmentsThis work was supported by the U.S. Department of Energy (DOE), Energy Efficiency and Renewable Energy, Hydrogen and Fuel Cell Technologies Office (HFTO) under the auspices of the Electrocatalysis Consortium (ElectroCat 2.0). Argonne is managed for the U.S Department of Energy by the University of Chicago Argonne, LLC, under Contract DE-AC-02-06CH11357 .

Pathfinding Process Development for the Realization of Atomic Precision Advanced Manufacturing (APAM)-Based Vertical Tunneling Field Effect Transistors for Enhanced Energy Efficiency

Since the end of Dennard scaling, where metal oxide semiconductor field effect transistor (MOSFET) operating frequency and energy efficiency improved with shrinking device dimensions [1], increasing transistor density is predicted to increase the total power consumption of a system [2]. A key limitation for MOSFETs is that the minimum rate of turn-on, or subthreshold swing (SS), is ~60 mV/decade at room temperature because of the Boltzmann statistics that dictate charge density. Thus, maintaining constant electric field without increasing energy consumption (i.e. gate bias) requires decreasing the SS by investigating alternative materials or device designs, like tunnel FETs (TFETs) [3]. Recent advances in atomic-scale control promise to provide control over quantum mechanical degrees of freedom which have hindered TFET performance in practice. These considerations make atomic precision advanced manufacturing (APAM) an appealing platform to realize a proof-of-concept TFET with atomic scale features [4,5].APAM can produce a 2D sheet of dopants in silicon beyond the solid solubility limit that can be patterned in-plane and capped with epitaxial silicon for strong carrier confinement in the out-of-plane direction (Figure 1). Indeed, improvements to planar TFETs that effectively have 1D channels with low on:off current ratios have been proposed by changing to a vertical geometry that leverages the carrier confinement afforded by 2D materials to create a 2D channel [6], though these materials are not typical in a silicon foundry. In contrast, APAM provides this carrier confinement while exclusively using materials and chemicals that are used in silicon foundries and with compatible processes [7]. In the APAM TFET (Figure 1.8.), a gate bias induces a layer of holes at the oxide/silicon interface that extends from the source, enabling tunneling between the 2D phosphorus-doped layer that comprise the drain and the 2D induced hole layer.As tunnelling occurs vertically through the epitaxial silicon cap, it becomes critical to determine the optimal growth temperature, to keep the dopants in a 2D sheet at low temperatures versus producing low-defect silicon at higher temperatures. Similarly, for optimal electric field control, it becomes critical to determine the optimal processing temperature to maintain the 2D dopant sheet and produce a low-defect gate oxide. The electronic thickness of the dopant layer can be measured using weak localization and the segregation of dopants out of the 2D sheet can be measured using secondary ion mass spectrometry. Our intial attemps at evaluating the electrical quality of the epitaxial silicon cap used PMOS transistors made with an ALD gate dielectric on APAM material without the buried phosphorus layer. Intuitively, we expect material grown at a higher temperature to produce a lower density of defects and therefore more performant PMOS, but find instead that the initial results demonstrate no systematic trend. These results potentially indicate there is an unknown variable obscuring the intentionally changed variable of growth temperature. Here, we propose several possible causes for this observation – both the variability from APAM processing or low-temperature microfabrication could mask an underlying trend.In summary, an APAM TFET provides a path toward increasing energy efficiency of transistors by decreasing SS compared to MOSFETs. The process tradeoffs that produce tightly confined 2D doped layers compared to low defect materials are starting to be explored using PMOS devices. Here, we report on the impact of process variability in drawing conclusions from these devices toward the realization of an APAM TFET.SNL is managed and operated by NTESS under DOE NNSA contract DE-NA0003525.[1] R. H. Dennard et al., “Design of ion-implanted MOSFET's with very small physical dimensions”, IEEE J. Solid-State Circuits 9, 256 (1974).[2] https://irds.ieee.org/[3] J. Koga et al., “Negative differential conductance in three‐terminal silicon tunneling device”, Applied Physics Letters, 69, 1435 (1996).[4] T.-M. Lu et al., “Path towards a vertical TFET enabled by atomic precision advanced manufacturing”, 2021 Silicon Nanoelectronics Workshop (2021).[5] X. Gao et al., “Modeling and Assessment of Atomic Precision Advanced Manufacturing (APAM) Enabled Vertical Tunneling Field Effect Transistor”, 2021 SISPAD, 102 (2021).[6] H. Lu et al., “Tunnel Field-Effect Transistors: State-of-the-Art”, IEEE J. Electron Device Society, 2, 44 (2014).[7] S. Misra et al., “Method of chemical doping that uses CMOS-compatible processes”, U.S. Patent 11,798,808. Figure 1

Exploring the Efficiency of Magnetic Separation and Gravity Concentration for Valorizing Pb-Zn Smelter Slag in a Circular Economy Framework.

The presented work offers an innovative process scheme for valorizing Pb-Zn slag, which involves crushing, grinding, and separation techniques to concentrate valuable components (non-ferrous metals). This methodology could have a significant impact on the global beneficiation of metallurgical slags since it is significantly more simple, environmentally friendly, and cost-effective than standard pyro- and hydrometallurgical procedures. According to previous physicochemical and mineralogical studies, Pb-Zn slag is a valuable secondary raw material. This inhomogeneous technogenic resource contains substantial amounts of non-ferrous metals (Pb, Zn, Cu, and Ag). However, laboratory tests have indicated that the Pb-Zn slag contains highly uneven amounts of valuable metals, ranging from several g/ton to tens of g/ton. The main issue is that traditional metallurgical procedures for releasing beneficial elements are not commercially viable since the elements are "trapped" within the amorphous aluminosilicates or intergrowths of alloy grains and glassy phases. Gravity concentration (Wilfley 13 shaking table) and magnetic separation (Davis separator and disk separator) were used to obtain the final concentrate following comminution and grindability testing. The gravity concentration proved more effective. Namely, magnetic separators could not process nor adequately separate beneficial non-ferrous elements because they were merged together with iron-bearing minerals and aluminosilicates in amorphous Pb-Zn slag grains. With the gravity concentration approach, 12.99% of the processed slag belonged to ∆T fraction (concentration of non-ferrous metal alloys), while remaining 87% corresponded to the tailings fraction (∆L). The total amounts of recovered Pb, Zn, Cu, and Ag from ∆T and ∆L fractions were 5.28%, 6.69%, 0.58%, and 76.12 ppm and 1.22%, 6.05%, 0.43%, and 15.26 ppm, respectively. This streamlined approach to valorizing Pb-Zn slag can reduce the need for hazardous chemicals used in hydrometallurgical refinement operations, as well as the extremely high temperatures required for pyrometallurgical processing. This is the first study to investigate the viability of this novel methodology, which involves the direct examinations of the Pb-Zn slag feed with various alternative technologies for separation and concentration. After extracting the valuable metals, the amorphous aluminosilicate part of the Pb-Zn slag can be reapplied as an alternative raw material in the building sector, adding to the circularity of the suggested approach.

Forensic identification of fingerprints on various substrates based on fluorescent carbon nanodots from date seeds assisted by Tracker software

Fingerprint identification is done by observing fingerprint patterns usually found on various surfaces at crime scenes. However, fingerprints are easily damaged, erased, and/or lost. Therefore, alternative materials are needed that can preserve fingerprint patterns. In this study, we use carbon nanodots (C-dots). This research aims to prepare and characterize C-dots made from date seeds, and then determine the robustness of the latent fingerprints using C-dots on various printed substrates assisted by Tracker software. This is experimental research of preparing and characterizing fluorescent C-dots from date seeds and printing fingerprints on various substrates. The C-dots were prepared using oven and microwave heating methods and characterized using an ultraviolet-visible (UV-Vis) spectrophotometer, photoluminescence (PL), X-ray diffraction (XRD), Fourier transform infrared (FTIR) spectroscopy, and particle size analyzer (PSA). The substrates used for printing the fingerprints were plastic, ceramic, paint, and glass. Based on the characterization results, the C-dots have i) an absorption peak at wavelength of 252.2 nm (core) and band gap energy of 3.27 eV, ii) an emission wavelength of 495 nm emitting cyan color, iii) an amorphous structure based on the diffraction pattern, iv) functional groups of C-H, CC, CC, and O-H, and v) particle sizes of 1.3 nm (< 10 nm). Moreover, the results of the fingerprint identification based on the visualization test were successful because a subject’s fingerprint pattern was formed and various patterns were identified. In the robustness test, the latent fingerprints lasted 30 days and then slightly faded in the whorls pattern.

Solution-derived Ge–Sb–Se–Te phase-change chalcogenide films

Ge–Sb–Se–Te chalcogenides, namely Se-substituted Ge–Sb–Te, have been developed as an alternative optical phase change material (PCM) with a high figure-of-merit. A need for the integration of such new PCMs onto a variety of photonic platforms has necessitated the development of fabrication processes compatible with diverse material compositions as well as substrates of varying material types, shapes, and sizes. This study explores the application of chemical solution deposition as a method capable of creating conformally coated layers and delves into the resulting modifications in the structural and optical properties of Ge–Sb–Se–Te PCMs. Specifically, we detail the solution-based deposition of Ge–Sb–Se–Te layers and present a comparative analysis with those deposited via thermal evaporation. We also discuss our ongoing endeavor to improve available choice of processing-material combinations and how to realize solution-derived high figure-of-merit optical PCM layers, which will enable a new era for the development of reconfigurable photonic devices.

Residues from beneficiation of granite in porcelain stoneware: Effects on technological properties

Granite extraction waste represents an interesting alternative material for porcelain stoneware production, but information on its influence presents several gaps. For this reason, two different wastes were selected: a coarser iron-rich material from magnetic separation and a finer one from conveyance and abatement systems. Both were physically and chemically characterized. Batches were formulated by partial substitution of feldspar and technological behaviour of bodies was assessed by simulating the industrial manufacture at laboratory scale. Tiles were shaped by uniaxial pressure and fired by fast firing in electric roller kiln. The effect of waste addition was evaluated during the whole production process. Fired samples were characterized in terms of technological properties, mineralogical composition and microstructure evolution. The formulation optimization reduces firing temperature getting commercial technological constraints. A further increase of finer waste content affects compaction and mechanical strength. The presence of micaceous particles after the firing process may act as cracks initiation.

Resistive Gas Sensors Based on 2D TMDs and MXenes.

ConspectusGas sensors are used in various applications to sense toxic gases, mainly for enhanced safety. Resistive sensors are particularly popular owing to their ability to detect trace amounts of gases, high stability, fast response times, and affordability. Semiconducting metal oxides are commonly employed in the fabrication of resistive gas sensors. However, these sensors often require high working temperatures, bringing about increased energy consumption and reduced selectivity. Furthermore, they do not have enough flexibility, and their performance is significantly decreased under bending, stretching, or twisting. To address these challenges, alternative materials capable of operating at lower temperatures with high flexibility are needed. Two-dimensional (2D) materials such as MXenes and transition-metal dichalcogenides (TMDs) offer high surface area and conductivity owing to their unique 2D structure, making them promising candidates for realization of resistive gas sensors. Nevertheless, their sensing performance in pristine form is typically weak and unacceptable, particularly in terms of response, selectivity, and recovery time (trec). To overcome these drawbacks, several strategies can be employed to enhance their sensing properties. Noble-metal decoration such as (Au, Pt, Pd, Rh, Ag) is a highly promising method, in which the catalytic effects of noble metals as well as formation of potential barriers with MXenes or TMDs eventually contribute to boosted response. Additionally, bimetallic noble metals such as Pt-Pd and Au/Pd with their synergistic properties can further improve sensor performance. Ion implantation is another feasible approach, involving doping of sensing materials with the desired concentration of dopants through control over the energy and dosage of the irradiation ions as well as creation of structural defects such as oxygen vacancies through high-energy ion-beam irradiation, contributing to enhanced sensing capabilities. The formation of core-shell structures is also effective, creating numerous interfaces between core and shell materials that optimize the sensing characteristics. However, the shell thickness needs to be carefully optimized to achieve the best sensing output. To reduce energy consumption, sensors can operate in a self-heating condition where an external voltage is applied to the electrodes, significantly lowering the power requirements. This enables sensors to function in energy-constrained environments, such as remote or low-energy areas. An important advantage of 2D MXenes and TMDs is their high mechanical flexibility. Unlike semiconducting metal oxides that lack mechanical flexibility, MXenes and TMDs can maintain their sensing performance even when integrated onto flexible substrates and subjected to bending, tilting, or stretching. This flexibility makes them ideal for fabricating flexible and portable gas sensors that rigid sensors cannot achieve.

Supported ionic liquids to purify microbial L-Asparaginase

L-Asparaginase (ASNase) is a versatile enzyme that converts L-asparagine into ammonia and aspartic acid. This enzyme has applications in the food industry and health sector. However, high purity ASNase is required, resulting in high production costs. Therefore, in this work, two supported ionic liquids (SILs), specifically silica modified with dimethylbutylpropylammonium chloride ([Si][N3114]Cl) or triethylpropylammonium chloride ([Si][N3222]Cl), were investigated as alternative adsorption materials to purify ASNase. Different conditions were evaluated to improve enzyme purity, including total protein content in the cell extract, contact time, and SIL/cell extract ratio (w/v). Under optimal conditions using [Si][N3114]Cl, a maximum ASNase purification of 6.1-fold is achieved in a single step, resulting from the preferential attachment of other proteins on [Si][N3114]Cl SIL. According to the results, hydrophobic interactions rule the selective adsorption of protein impurities from the cell extract by the SIL, thereby increasing the ASNase purification levels. This approach offers a significant advantage, not requiring the desorption and elution of the target enzyme, while envisioning the application of SILs in a flow-through elution approach. The protonation state of protein surface was calculated by computational analysis, revealing that positively charged amino acids such as arginine and lysine block the effective binding of the enzyme to the SILs. Overall, if properly designed, SILs are promising alternative supports for the downstream processing of ASNase from cell extracts.

Activating CoP via spontaneous atomic palladium doping for efficient hydrogen evolution

Electrocatalytic hydrogen evolution is an efficient and clean hydrogen production technology with simple process and high product purity. Searching for inexpensive alternatives to platinum will help popularize proton exchange membrane water electrolysis (PEMWE) technology. However, the alternative catalytic materials are essentially limited by low catalytic efficiency. Herein, we address this challenge through chemically activating cobalt phosphide (CoP) by doping a small amount of atomic palladium. Palladium substitution occurs at the cobalt site of CoP. Theoretical calculations manifest that the phosphorus atoms near the palladium sites exhibit almost zero hydrogen adsorption free energy. The final cobalt phosphide doped with only 2 wt% of palladium shows wonderful HER performance. Specifically, its overpotential at a current density of 10 mA cm−2 is only 37.5 mV in an acidic medium, and the corresponding Tafel slope is 56 mV dec−1. This work provides a reference for preparing high performance non-platinum catalysts.

Antimony nanoparticles encapsulated in interconnected nitrogen-doped carbon nanospheres for high performances PIBs

Antimony (Sb) has attracted significant attention as an anode material for potassium-ion batteries (PIBs) due to its high theoretical capacity and suitable working voltage. However, the severe volume variations of Sb during potassiation/depotassiation process lead to sluggish kinetics and poor cyclic stability for PIBs. In this study, Sb nanoparticles are confined within interconnected N-doped carbon nanospheres (Sb@NC) through an effective carbothermal reduction process. The potassium storage performances and mechanism are elucidated through electrochemical tests combined with ex-XRD analysis. When used as an anode for PIBs, the optimized Sb@NC-2 anode exhibits excellent cycle stability of 463.0 mAh g−1 at 200 mA g−1 over 100 cycles and superior rate capability of 113.4 mAh g−1 at a high current density of 2 A g−1. Besides, a full cell comprising an Sb@NC-2 anode and a PTCDA cathode is also tested to validate the practical feasibility of the anode. Furthermore, Density Functional Theory (DFT) calculations demonstrate that N-doped carbon can enhance the adsorption of K+ and improve the kinetics of electrochemical reactions. Therefore, the unique yolk-shell structure in this study effectively restricts volume expansion and aggregation of Sb particles while facilitating rapid electron/ion transfer. These findings provide a potential alternative anode material for advanced PIBs.

Mitigation of thallium threat in paddy soil and rice plant by application of functional biochar

Thallium (Tl) is a highly toxic metal, and its contamination in soils entails high risks to human health via food chain. It remains largely unknown of the effects of applying biochar on Tl uptake in paddy systems despite that few studies have shown that biochar exhibits great potential for decreasing Tl bioavailability in soils. Herein, we examined the mitigating effects of the application of biochar (5 and 20 g/kg pristine biochar; 5 and 20 g/kg Fe/Mn-modified biochar) on Tl uptake in paddy soil and rice plant after an entire rice growth period. The results suggested that the application of Fe/Mn-modified biochar (FMBC) considerably mitigated the accumulation of Tl in different tissues of rice plants. Specifically, total Tl content in rice plants treated with FMBC-20 decreased by over 75% compared with control experiment. In addition, the amendment of FMBC in Tl-rich paddy soils can enhance the communities of microorganisms (Actinobacteria and Proteobacteria). Further analysis of the soil microbial symbiosis network revealed that FMBC promotes the living microorganisms to play modular synergistic interactions, which is crucial for FMBC-induced Tl stabilization in soils. All these findings indicated that FMBC is an efficient and environmentally friendly Tl-immobilization alternative material and can be potentially used in the remediation of Tl-contaminated paddy soils and/or cropland.

Aluminosilicate-based material fabricated from fly ash for energy harvesting application

A triboelectric nanogenerator (TENG) is an emerging energy harvesting technology that utilizes the combination of triboelectrification and electrostatic induction to collect wasted mechanical energy and convert it into electricity. In this work, an aluminosilicate (AS)-based composite, considered as a potential alternative to cement material, has been developed for the fabrication of TENGs. Herein, the AS material is synthesized through the alkali activation of fly ash using a mixture of sodium hydroxide (NaOH) and sodium silicate (Na2SiO3) solutions as activating agents. The electrical output of AS TENGs can be optimized by tuning the liquid-to-solid powder (L/S) ratio during the fabrication of AS composites. The AS composites fabricated at different L/S ratios exhibit the variations in dielectric properties, surface morphology and microstructure. It is found that a high dielectric constant is not the only requirement for achieving optimal TENG output performance. The contribution of dielectric properties and microstructures of the AS composites on TENG performance is discussed. The AS composite with an optimal L/S ratio of 0.5 results in the highest TENG power output density of 2.78 W/m2. Additionally, the versatility of AS TENG to harvest mechanical energy and its application as a power source for portable electronic device are demonstrated. This research has proposed the promising aspect of AS composites as alternative construction materials capable of harvesting mechanical energy, which is essential for the development of green and sustainable power sources.

A novel diamond-like carbon based photocathode for PICOSEC Micromegas detectors

The PICOSEC Micromegas (MM) detector is a precise timing gaseous detector based on a MM detector operating in a two-stage amplification mode and a Cherenkov radiator. Prototypes equipped with cesium iodide (CsI) photocathodes have shown promising time resolutions as precise as 24 picoseconds (ps) for Minimum Ionizing Particles. However, due to the high hygroscopicity and susceptibility to ion bombardment of the CsI photocathodes, alternative photocathode materials are needed to improve the robustness of PICOSEC MM. Diamond-like Carbon (DLC) film have been introduced as a novel robust photocathode material, which have shown promising results. A batch of DLC photocathodes with different thicknesses were produced and evaluated using ultraviolet light. The quantum efficiency measurements indicate that the optimized thickness of the DLC photocathode is approximately 3 nm. Furthermore, DLC photocathodes show good resistance to ion bombardment in aging test compared to the CsI photocathode. Finally, a PICOSEC MM prototype equipped with DLC photocathodes was tested in muon beams. A time resolution of around 42 ps with a detection efficiency of 97% for 150 GeV/c muons were obtained. These results indicate the great potential of DLC as a photocathode for the PICOSEC MM detector.

Low-cost porous transport layers for water electrolysis cells with polymer electrolyte membranes

Proton exchange membrane (PEM) water electrolysis has advantages over other methods of producing green hydrogen such as its excellent response to power input fluctuations; wide operating range of current density; ease of production of high-pressure, high-purity hydrogen; and high durability. However, the conventional precious metal coatings used on the bipolar plates (BPPs) and porous transport layers (PTLs) of the PEM water electrolysis cell to prevent their oxidation are problematic because of their high cost; indeed, the BPPs and PTLs combined are the largest contributor (50%–70%) to the total cost of PEM water electrolysis stacks. Here, the Pt-coated PTL on the oxygen electrode side of a PEM water electrolysis cell was replaced with one with an alternative low-cost material coating (Ti4O7 or NiTiP), and the water electrolysis characteristics of the system were evaluated. We found that Ti4O7, but not NiTiP, functioned as a conductive, corrosion-resistant PTL coating in the PEM water electrolysis cell.

Drying strategies for maximizing polyhydroxybutyrate recovery from microalgae cultivated in a raceway pond: A comparative study

Polyhydroxybutyrate (PHB) derived from microalgae are considered a promising alternative bioplastic material to replace synthetic plastics. This study evaluated the effects of various drying techniques (sun, freeze, oven and air drying) on PHB recovery from microalgae. Freeze drying recovered the maximum PHBs (6.2%) followed by sun drying (5.2%), air drying (2.3%), oven drying (2%), and the lowest in wet biomass (1.2%). The most energy-intensive drying method was freeze drying (26.83kW) followed by oven drying (3kW) while the other methods did not require energy. The minimum time requirement for drying was oven drying (6 hours), followed by freeze drying (24 hours), sun drying (48-72 hours), and air drying (96-120 hours) while wet biomass did not require time. In terms of PHB yield per unit time, oven (0.33%/h) is a more effective drying technique than freeze drying (0.25%/h) which produces 24.24% higher PHB yield per unit time. Fourier transform infrared spectroscopy (FTIR), thermogravimetric analysis (TGA) and differential scanning calorimetry (DSC) confirmed PHB structure and thermal stability up to 300°C from dried biomasses compared to wet biomass at 200°C. This study indicated that drying techniques significantly influence the PHB recovery from microalgae biomass. Findings also revealed that the oven dried technique can be efficiently scaled up for PHB recovery.

Nitrogenation of Nd(Fe,Mo)12 powders for sintered magnets

The intermetallic Rare Earth-Fe12 (REFe12) compounds are considered as the strongest candidates for alternative high-performance permanent magnet material, thanks to the combination of high magnetocrystalline anisotropy, high Curie temperature and moderate saturation magnetization. However, the NdFe12 based compounds suffer from a weak uniaxial magnetocristalline anisotropy at room temperature. The insertion of light elements, like nitrogen, induces a strong uniaxial anisotropy and an increase of the Curie temperature as well. Nevertheless, the nitrogenation of these compounds have proved to be tricky, as the reaction kinetics is very slow at moderate temperatures, whereas the decomposition of the 1-12 phase occurs at higher temperatures. In the present study the aim is to develop nitrogenated powders suitable for the manufacture of Nd(Fe,Mo)12N-based sintered magnets, starting from Nd(Fe,Mo)12 precursors prepared by strip-casting. The nitrogenation of Nd(Fe,Mo)12 powders was undertaken to analyze the mechanisms of reaction and to determine the experimental conditions allowing to avoid both the formation of α-Fe and the nitrogenation of the Nd-rich intergranular phase. Structural and magnetic investigations are performed on the parent alloys and the nitrogenated powders, allowing to identify the mechanism of the solid-gas reaction and to determine, for the first time to our knowledge, the nitrogen thermodynamic equilibrium pressure between the 1-12 phase and its nitride.

Exploring Eco-Friendly Novel Charge Transport Materials for Enhanced Performance of Tin based Perovskite Solar Cell

This pioneering simulation study explores the potential of perovskite materials, particularly the non-toxic methyl ammonium tin iodide (MASnI3), in solar cell technology. The investigation focuses on eco-friendly, solution-processed compounds—specifically, WO3 and In2S3 as Electron Transport Layers (ETL) and MoO3 and WSe2 as Hole Transport Layer (HTL)—to develop planar n-i-p MASnI3 perovskite solar cell (PSC) devices. WO3 is chosen for its solution processing and high electron mobility, while In2S3 offers n-type properties, superior carrier mobility, non-toxicity, and thermal durability. MoO3 and WSe2 are selected as HTLs for their efficient charge transport capabilities. Utilizing the solar cell capacitance simulator (SCAPS-1D) software, the study systematically evaluates alternative charge-selective materials, considering various parameters such as thickness (0.1µm to 1.5µm for absorber and 0.1µm to 0.35µm for CTLs), doping concentration (3.2E10 to 3.2E16 for absorber and E16 to E20 for CTLs), defect density, and energy band offset for MASnI3 PSCs. Four distinct n-i-p device structures are optimized, yielding impressive PCE improvements ranging from 14.63% to 25.34%, a significant 3% enhancement compared to initial results. Notably, the WO3/MASnI3/WSe2 configuration exhibits limitations in electrical performance, while the other optimized structures demonstrate substantial efficiency gains. Further analysis investigates the impact of reflecting coatings (10% to 90%), varying contact work functions (5.2 to 5.8eV), and temperature (300 to 400K) on photovoltaic parameters. Critical factors including energy band offset, recombination current profile, and built-in potential, are meticulously examined, laying the groundwork for advanced PSC implementation. The study culminates in the In2S3/MASnI3/MoO3 device configuration, which achieves a peak efficiency of 25.34%, showcasing superior thermal stability and an enhanced fill factor, thus propelling all-inorganic PSCs towards practical implementation.

Insights into different marine aquaculture infrastructures from a life cycle perspective

Aquaculture facilities represent an often-neglected process in environmental impact studies. This study focus on the environmental impact assessment of alternative net materials in Mediterranean marine aquaculture. A Life Cycle Assessment was conducted using primary and secondary data from specific databases and literature. Three baseline scenarios were compared: copper alloy net cages with 100% of recycled material (CAN100), 75% of recycled material (CAN75), and polyethylene net (PEN) System boundaries include manufacturing and disposal of cages, nets, and mooring system. The use and emissions of antifouling paints and CAN were considered. Sensitivity analysis of the most impacting sub-processes and Uncertainty analysis were also conducted.The use of CAN is advantageous in terms of environmental impact, but only considering a complete recyclability of the net at the end of its service life. Moreover, when considering a reduced service life of the PEN due to the detrimental effect of biofouling, the advantage of the CAN is even more evident. To counteract the negative effect of biofouling, copper-based antifouling paints are generally used in marine aquaculture. These products are a main environmental hotspot in PEN systems. Therefore, a higher consumption of such products could determine an environmental burden shifting from CAN to PEN ones. So far, CAN are not widespread in the aquaculture industry, mainly due to the high cost of initial investment compared to traditional PEN. Considering operational and environmental advantages, CAN cages could represent an affordable and resilient solution for aquaculture enhancing environmental, economic, and social performances of this industry.

Low-density granite-based geopolymer for well cementing: The role of burnt lime in enhancing early strength

In the pursuit of sustainable solutions within the oil and gas industry, the environmental and mechanical limitations of Ordinary Portland Cement (OPC) have led to the evaluation of more sustainable alternative materials for oilwell cementing applications. Particularly in shallow-depth cementing operations, where low-density slurries are essential to prevent formation breakdown, current solutions fall short in balancing environmental impact with the industry's performance requirements. Geopolymers, known for their reduced carbon footprint and comparable mechanical properties, have been seen as a promising alternative. However, increasing water content to lower the slurry density remains a challenge for geopolymers due to the weakening effect and prolonged reaction. The specific role of burnt lime (CaO) has the potential to enhance the early strength of low-density geopolymers yet remains under-explored for this particular case. This study aims to fill this gap by examining the effects of two different reactivities of CaO on a low-density granite-based geopolymer at low temperatures and investigate the potential of CaO to enhance the early strength of low-density geopolymers, aiming to provide a sustainable alternative to traditional cementing materials in oil well operation. The investigation consists of viscosity measurements, pumpability tests, and compressive strength evaluations. Additionally, isothermal calorimetry, TGA, XRD, and SEM were conducted to gain a deeper understanding of the behavior of each sample. Supplementary tests were conducted to evaluate the effect of varying CaO concentrations and the impact of mud contamination on the performance of low-density geopolymers. The investigation revealed that calcium oxide did not significantly impact the initial viscosity of the slurry however, it affects gelation and rate of the reaction. Short-term strength was shown to be affected by CaO at two different temperatures, yet negligible effects were seen in the long-term period for geopolymers with a high water-to-solid ratio. The findings suggest that CaO can significantly enhance the early strength of geopolymers, which are crucial properties for cementing operations in oil and gas wells. This could contribute to accelerate the possibility of geopolymers as a viable sustainable replacement for Portland cement especially in shallow and low-temperature well-cementing applications.