Spin-based magnetic random access memory is emerging as a key enabling low-power technologies, which have already spread over markets from embedded memories to the Internet of Things. In addition, spin devices can offer alternative solutions for unconventional computing and energy harvesting. We present an experimental Ising computer based on magnetic tunnel junctions, which successfully solves a 70-city travelling salesman problem (4761-node Ising problem) [1]. We also propose a spintronic artificial neuron based on the heavy metal (HM)/ferromagnet (FM)/antiferromagnet (AFM) [2], which can reset itself due to the exchange bias. Using our proposed neuron, we further implement a restricted Boltzmann machine (RBM) and stochastic integration multilayer perceptron (SI-MLP). By integrating the electrically connected eight spin--torque oscillators (STOs), we demonstrate the battery-free energy-harvesting system by utilizing the wireless RF energy to power electronic devices (such as LEDs) [3,4].

We present our perspective on spin device applications using emerging 2D materials [6]. Previous proposals for the field-free spin--orbit torque (SOT) switching of perpendicular magnetic anisotropy (PMA) require an additional magnetic field. Exploiting the out-of-plane spins could be a solution to this challenge [6]. Here, we experimentally demonstrate the field-free switching of PMA CoFeB at room temperature by utilizing out-of-plane spins from Weyl semimetals, TaIrTe₄ [7] and PtTe₂/WTe₂ [8]. Finally, we discuss magnon-mediated spin torques, which could minimize Joule heating and corresponding energy dissipation [9]. We demonstrate the magnon current-driven switching of PMA at room temperature and field-free operation [10].

[1] J. Si, et al., “Energy-efficient superparamagnetic Ising machine and its application to traveling salesman problems” Nat. Commun. (2024) 15, 3457.
[2] Q. Yang, et al., “Spintronic Integrate-Fire-Reset Neuron with Stochasticity for Neuromorphic Computing” Nano Lett. (2022) 22, 8437.
[3] R. Sharma et al., “Electrically connected spin-torque oscillators array for 2.4 GHz WiFi band transmission and energy harvesting” Nat. Commun. (2021) 12, 2924.
[4] R. Sharma et al., “Nanoscale spin rectifiers for harvesting ambient radiofrequency energy” Nat. Elec. (2024) 7, 653–661.
[5] H. Yang et al., “Two-dimensional Materials Prospects for Non-volatile Spintronic Memories” Nature (2022) 606, 663-673.
[6] Q. Yang, et al., “Field-free spin–orbit torque switching in ferromagnetic trilayers at sub-ns timescales” Nat. Commun. (2024) 15, 1814.
[7] Y. Liu, et al. “Field-free switching of perpendicular magnetization at room temperature using out-of-plane spins from TaIrTe₄” Nat. Electron. (2023) 6, 732-738.
[8] F. Wang, et al. “Field-free switching of perpendicular magnetization by two-dimensional PtTe₂/WTe₂ van der Waals heterostructures with high spin Hall conductivity” Nat. Mater. (2024) 23, 768-774.
[9] Y. Wang, et al. “Magnetization switching by magnon-mediated spin torque through an antiferromagnetic insulator” Science (2019) 366, 1125-1128.
[10] F. Wang, et al. “Deterministic switching of perpendicular magnetization by out-of-plane anti-damping magnon torques” Nat. Nano. (2024) https://doi.org/10.1038/s41565-024-01741-y.

Due to the widespread use of critical and toxic materials, the research community has begun prioritising next-generation materials based on various factors, including greener availability, low impact, recyclability, biodegradability, cost-effectiveness, and eco-friendliness.

Over the past few years, researchers have been on a quest for eco-friendly materials that can match the performance of traditional ones while reducing energy costs. In this pursuit, nature has been a rich source of inspiration. The natural micro and nanostructures found in beetles or butterflies, for instance, have evolved over millions of years, offering us a wealth of innovative possibilities.

One fascinating example of nature-based materials is cellulose nanocrystals (CNCs). These crystals, when dispersed in water, can form a chiral nematic liquid crystalline phase. As the water evaporates, the chiral order is preserved, resulting in solid films with 1D photonic crystal properties and iridescent colours. The unique left-handedness of these structures allows them to interact selectively with left and right-circular polarised light (LCPL and RCPL), leading to the formation of films with intriguing electronics and photonic properties.

Besides electronics and photonic applications, cellulosic materials and other natural polymers are particularly interesting for energy storage devices. Their chemical structure differences influence, for instance, the ionic conductivity of the electrolytes and can also be used as precursors for active anode materials. This presentation will address the use of nature-based materials to prepare biopolymeric electrolytes and biopolymer matrices that act as the host polymer that might incorporate the electrolyte and various ionic dopants to increase their ionic conductivity further.

Nanotechnology could improve pediatrics. It could be used to tackle special pediatric medical difficulties, as typical medication delivery systems often lack selectivity, resulting in inferior outcomes and side effects. Nanotechnology can also be used to precisely deliver drugs to children's illness sites. Nanotechnology, such as targeted gene therapy, can help children with congenital and genetic illnesses.

Diagnostics in pediatrics can also be revolutionized through nanotechnology. Early and accurate diagnosis is crucial to prevent long-term complications and improve outcomes. Nanotechnology-enabled tools, such as nanoparticle-based imaging agents and biosensors, provide heightened sensitivity and specificity, allowing for early disease detection and precise monitoring. However, there are concerns about the safety and long-term effects of nanoparticles in children, whose developing bodies might react differently than those of adults. Ethical considerations of using advanced technologies in young populations also need careful attention.

Nanotechnology’s significance in pediatrics is profound, as it can help to address specific needs that distinguish children from adults. Pediatric patients’ ongoing growth and developmental stages present unique challenges. Nanoparticles ensure targeted drug delivery, improving therapeutic outcomes while minimizing side effects, which is crucial for conditions like pediatric cancers. Innovations in diagnostics brought by nanotechnology are equally significant, enabling early detection and timely interventions for better prognoses.

Another groundbreaking application is in vaccines. Nanoparticles can enhance vaccine safety and efficacy by ensuring targeted delivery and controlled release, which is particularly important for infants with developing immune systems. Nanotechnology also offers potential solutions for treating neurological conditions by bypassing the blood–brain barrier, a significant obstacle in drug delivery to the brain.

While nanotechnology promises vast improvements in pediatric medicine, it is essential to apply it safely and ethically. This overview highlights nanotechnology’s transformative potential in pediatrics, along with the challenges and considerations that must be addressed to ensure its safe and effective implementation.

In welding, the heat-affected zone (HAZ) refers to the region of the base metal that has been subjected to a temperature change during the welding process. The HAZ is a critical area in welding because it can have significant impacts on the mechanical properties and overall quality of the welded joint. Microwave welding is a technique of joining metals through susceptor heating which is extensively used by researchers. However, limited studies have been reported studying the HAZ in microwave-welded joints.

In the present study, lap joints between SS202 and SS304 were developed through a novel selective microwave hybrid heating (SMHH) process utilizing nickel powder as the filler. Study of the HAZ was carried out through electron back-scattered diffraction (EBSD) analysis. EBSD is a SEM-assisted technique used to reveal the crystallographic data within the microstructural data of a specimen. Different locations were considered for the EBSD scans, moving towards the joint. For the upper plate (SS202), P1, P2, P3, P4 and P5 were the designated locations, whereas for the lower plate (SS304), R1, R2, R3, R4, and R5 were the designated locations.

A fine-grain heat-affected zone (FGHAZ) was observed at the P3 and P4 locations. For the upper plate, the length of the FGHAZ was approximately 30 mm, whereas for the lower plate, no such FGHAZ was observed. Further, for location P4, the average grain size diameter (AGSD) increased significantly to 19.974 µm, characterizing it as a coarse-grain heat-affected zone (CGHAZ). A relatively high fraction of the average angle from 0.4 to 0.8˚ for the KAM histograms corroborates the presence of residual stresses. Increased KAM values at locations P2, P3 and R2 were revealed, pointing towards the evolution of slip lines at different locations. The rapid thermal cycling caused a significant increase in the average KAM values at locations P2, P3 and R2.

The paper presents the results of research on the tool manufacturing process with a working layer obtained through 3D printing technology, using the L-PBF method, from M300 tool steel made on a steel substrate, intended for the plastic forming of sheet metal. In the first stage, model shapes were made using the L-PBF method, using various printing parameters, including laser power, distance between scanning lines, layer thickness, scanning speed and type. The shapes were tested for geometry, microstructure, phase analysis, texture, porosity, microhardness and wear resistance, coefficient of friction and surface roughness in contact with a selected range of sheets made of Ni, Fe and Al alloys. Additionally, the shapes were subjected to heat treatment and HIP, as well as laser burnishing and surface remelting. In the next stage, a plate with a threaded hole and threaded steel rolls were used, which were screwed into the plate, and layers of M300 steel with a thickness of 0.5-6 mm were made on their surface, using the L-PBF method, using selected, optimal 3D printing parameters. The obtained tool elements with working layers made of M300 steel were subjected to similar tests to those of the fittings. Then, comparative laboratory and industrial tests of sheet metal forming were performed using conventional tools and tools with layers obtained using the L-PBF method.

Polycrystalline silicon carbide (SiC) has been significantly used as a susceptor material during microwave-based material processing owing to its excellent microwave absorption properties. However, the interaction of microwaves with polycrystalline SiC at an atomic level has not been explored experimentally or theoretically. This work investigates the microwave heating characteristics of polycrystalline cubic 3C-SiC through molecular dynamics (MD) simulation using the Vashishta interatomic potential. The effect of change in electric field strength and frequency on the structural evolution and thermo-physical properties of polycrystalline 3C-SiC has been studied. The study revealed that the presence of grain boundaries in polycrystalline 3C-SiC structures plays a critical role in enhancing microwave absorption efficiency. Microwave exposure to polycrystalline 3C-SiC beyond 2830 K significantly increases total energy; consequently, a solid-to-liquid transition occurs in the 3C-SiC structure, initiated from the grain boundaries. Further, an increase in microwave exposure time results in a reduction in grain size due to rapid microwave absorption at grain boundaries. The phase transition temperature of polycrystalline 3C-SiC was observed to be 14% lower than that of the single-crystal 3C-SiC.

The main aim of this research wasto improve the mechanical and tribological properties of epoxy by adding nano-graphitic carbon nitride (g-C3N4). The nanoparticles were infused into epoxy resin with an ultrasonic system with various weight percentage ratios of the nanoparticle. Indirect tension testing was adopted to measure the tensile properties of the present nanocomposites. The micro-hardness test was conducted with the impact test to compare the the neat epoxy with filler one. Pin-on-ring wear testing was also performed to examine the wear performance of epoxy g-C3N4 nanocomposite. The addition of nanoparticles from g-C3N4 improves all the characteristics of epoxy, but in different proportions according to the quantity of the additive.

The growing interest in replacing synthetic colorants with natural alternatives stems from a growing concern for the environment, with natural colorants generally perceived as less harmful and more environmentally friendly due to their greater biodegradability. The present study focuses on exploring the aerial parts of Reseda Luteola L. as a potential source of natural yellow dye for wool dyeing. Microwave- and ultrasound-assisted extraction methods were used to extract the dyes, compared to the traditional reflux heating method. Extraction process parameters, such as time and solvent composition, were optimized to maximize dye yields from Reseda Luteola L..

Analytical methods, such as UHPLC-PDA, FTIR, XRD, UV-VIS, SEM-EDX, DSC, ¹H NMR and TGA, are applied to characterize the compounds present in the extracted dye, combining analyses of composition, molecular structure and thermal properties.

Dyeing was carried out using an alum-based mordant to prepare the wool, which was then dyed with the optimized dye extract. Each dyed material was then characterized using FTIR to analyze its chemical composition and functional properties. The color of each dyed material was also evaluated in terms of CIELAB values (L*, a* and b*) and color intensity value (K/S) to fully understand the chromatic variations induced by the dyeing process. The fabrics were assessed for their ability to protect against harmful UV rays and their antibacterial properties.

The development of earth-abundant catalysts for the electrochemical oxygen evolution reaction (OER) represents a significant challenge in the context of water splitting and hydrogen (H₂) economy.^1,2 For this purpose, various transition metal-based hydroxides or layered double hydroxides (LDHs) containing Fe/Co/Ni as OER active centers have emerged and have been proposed as an alternative to noble metal oxides (IrO₂ or RuO₂).^1,2 In this work, NO₃^- ion-containing deposition bath and pulse electrodeposition (PED) methods were employed for the synthesis of Fe_xHf_y and Ni_xHf_y double hydroxides. The composition of the electrodeposition bath and PED parameters such as pulse on/off potentials and the duration of pulse were tuned to achieve Fe_xHf_y/Ni_xHf_y double hydroxides with controlled Fe/Ni to Hf atomic ratios. For the Fe and Hf ion-containing bath, no PED occurred at the deposition potential of ≥ -1.4 V vs. SCE, whereas the PED at -1.6, -1.7, and -1.8 V demonstrated the deposition of Fe_xHf_y double hydroxides on graphite foils (G). It is revealed that the amount of double hydroxide deposition can be tightly controlled by controlling the time-on (T_on) parameter of PED at -1.8 V. In most of the deposition potentials, the EDX analysis showed a 1:1 atomic ratio of Fe:Hf in the materials with some impurities from the electrolyte. All the Fe_xHf_y double hydroxides produced in this study were found to be catalytically active for OER in alkaline medium. The PED (-1.8 V and T_on = 0.25 s)-synthesized Fe_xHf_y double hydroxide required only 440 mV overpotential to reach the OER current density of 10 mA cm^-2. Further studies on the OER activities of these materials are in progress. This study, for the first time, revealed a new set of double hydroxide catalysts for the oxygen evolution reaction.

Acknowledgment:

This research is part of project No. 2021/43/P/ST5/02281, co-funded by the National Science Centre and the European Union Framework Programme for Research and Innovation Horizon 2020 under the Marie Sklodowska-Curie grant agreement no. 945339.

Reference:

1. M. S. Burke, M. G. Kast, L. Trotochaud, A. M. Smith and S. W. Boettcher, J. Am. Chem. Soc. 2015, 137, 3638-3648.
2. M. Görlin, P. Chernev, J. F. Araújo, T. Reier, S. Dresp, B. Paul, R. Krähnert, H. Dau and P. Strasser, J. Am. Chem. Soc. 2016, 138, 5603-5614.

Wide-bandgap (WBG) perovskites, with energy bandgaps ranging from 1.5 to 2.3 eV, have been extensively investigated as the photoactive layer in the top cell of tandem photovoltaic devices. These perovskites have gained prominence in photovoltaic applications due to their high absorption coefficient, tunable bandgap, and ease of fabrication. The WBG perovskites are realized by the substitution of bromide ions in place of iodide ions in the traditional APbI₃ perovskites (where A represents a monovalent organic or inorganic cation), allowing precise control over the bandgap within the aforementioned range [1]. However, these WBG perovskites suffer from intrinsic phase instability and halide segregation under light exposure, particularly when a critical bromine content (~ 20%) is surpassed [2]. A high concentration of bromine accelerates the perovskite crystallization due to the lower solubility of bromide salts. This results in perovskite films with higher defect density and reduced crystallinity. This then leads to high V_oc losses and devices with reduced stability [3]. In this study, we investigate the impact of a chloride additive in inhibiting the formation of intermediate phases (2H/4H polytypes) in the 1.72 eV FACsPbIBr wide-bandgap perovskite films. The chloride ions forced the crystallization kinetics to improve the crystallinity of the target perovskite films, as revealed by the X-ray diffraction and scanning electron microscopy measurements. In situ photoluminescence measurements conducted during the spin-coating of the films revealed the initial nucleation stage through bromide ions in control films (PL peak: 701-719 nm). This is subsequently replaced by nucleation through chloride ions (PL peak: 690-695 nm), resulting in halide homogenization in the target films. Temperature-dependent XRD measurement also confirms the elimination of the 2H/4H intermediate phases in the target films. This additive engineering strategy improved the photostability of the films by reducing the defect density in the perovskite bulk, thus significantly improving the photovoltaic performance of the WBG perovskite devices. The PCE of the devices increased from 15% for the control samples to 18% for the target samples with a high V_oc of 1.224 V.

References:

1. Oliver, R.D., et al., Understanding and suppressing non-radiative losses in methylammonium-free wide-bandgap perovskite solar cells. Energy & Environmental Science, 2022. 15(2): p. 714-726.
2. Hoke, E.T., et al., Reversible photo-induced trap formation in mixed-halide hybrid perovskites for photovoltaics. Chemical Science, 2015. 6(1): p. 613-617.
3. Hang, P., et al., Highly efficient and stable wide‐bandgap perovskite solar cells via strain management. Advanced Functional Materials, 2023. 33(11): p. 2214381.