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Abstract With the aim of developing fuel cell applications that are capable of generating efficient electrical energy, much of the attention should be given to exploring new catalysts that could be less costly and more abundant than the most commonly used catalyst, platinum. This work explores nickel-based layered double hydroxide (Ni-LDH) as a fuel cell’s affordable catalyst for Oxygen Reduction Reaction (ORR). Ni-LDH was prepared and drop coated onto a Glassy Carbon Electrode (GCE) to conduct a 3-way electrode cyclic voltammetry using an oxygen-saturated aqueous sodium hydroxide (NaOH) solution as electrolyte. The electroanalytical study of the GCE-modified Ni-LDH working electrode showed an enhancement of both anodic and cathodic peaks because of the presence of oxygen at low temperatures. Data obtained from this experiment will serve as a reference for fuel cell systems in which Ni-LDH modified working electrodes are scaled up for comparison of area-specific properties. 

Abstract In this study, a novel deposition technique that utilizes diethylzinc (C₄H₁₀ZnO) with H₂O to form a ZnO adhesion layer was proposed. This technique was followed by the deposition of vaporized nickel(II) 1-dimethylamino-2-methyl-2-butoxide (Ni(dmamb)₂) and H₂gas to facilitate the deposit of uniform layers of nickel on the ZnO adhesion layer using atomic layer deposition. Deposition temperatures ranged from 220 to 300 °C. Thickness, composition, and crystallographic structure results were analyzed using spectroscopic ellipsometry, scanning electron microscopy (SEM), X-ray photoelectron spectroscopy (XPS), and X-ray diffraction (XRD), respectively. An average growth rate of approximately 0.0105 angstroms per cycle at 260 °C was observed via ellipsometry. Uniform deposition of ZnO with less than 1% of Ni was displayed by utilizing the elemental analysis function via SEM, thereby providing high-quality images. XPS revealed ionizations consistent with nickel and ZnO through the kinetic and binding energies of each detected electron. XRD provided supplemental information regarding the validity of ZnO by exhibiting crystalline attributes, revealing the presence of its hexagonal wurtzite structure. 

Abstract The majority of power consumption nowadays goes to heating. Global warming, air and water pollution caused by burning fossil fuel for heating encourage researchers and engineers to focus more on renewable energy. The solar system is one of Earth’s primary sources of clean power. Apart from photovoltaic panels and their effectiveness of power generation contribution, solar heaters are primarily used in different applications to recover heating needs in residential and commercial buildings. This paper focuses on an experimental study to generate heat by a solar system using metallic strips immersed in cement inside a solar vacuum tube. Heat can be transferred from inside the tube to the outside using metallic strips with high conductivity. Then, the metallic strips can be used as a heater to heat water or air in an isolated tank by direct contact between the hot strips and the fluid. In order to keep the system providing heat after the absence of sun’s rays, cement is used in this experiment as a heat repository. 

Abstract Homes relying on traditional heating systems such as furnaces, stoves, boilers, and similar mechanisms typically have a common requirement: the use of fossil fuels. Since fossil fuel prices are prone to fluctuations, it is crucial to explore alternative options. In the ongoing transition towards more sustainable solutions, solar energy emerges as an environmentally friendly choice due to its renewable nature. A pivotal device in harnessing solar energy for heating purposes is the solar air heater. This study presents a numerical analysis conducted using the CFD simulation software ANSYS, focusing on the performance characteristics of a pumpless solar room air heater that incorporates sectioning. The aim was to optimize the dimensions, specifically the pitch or distance between the turbulator features, and predict the heat exchanger’s thermal performance by measuring the associated head loss. To validate their findings, the researchers compared the predicted results from the CFD simulation with the calculated results using an Excel solver. Throughout the calculations, the impact of design variations (sectioning the pipe at different lengths relative to head loss) and the Reynolds number on stream aerodynamics and heat exchange processes were considered. The findings revealed a linear relationship between temperature and distance between the turbulators, with the heat-transfer measurements increasing alongside this distance. 

Abstract This paper explores nanoscale energy sensors and absorber metamaterials that can be used in various applications, such as solar cells and infrared detectors. It is possible to gain highly efficient and adjustable energy absorption, creating absorber metamaterials at the nanoscale that enhance the performance of solar cells. These metamaterials are based on molecular spintronics devices (MSD) and magnetic tunnel junctions (MTJ). The pillar shaped MTJs are made of two ferromagnetic metals separated by an insulating barrier, such as aluminum oxide (AlOx). The manufacturing process includes photoresist spin coating on a silicon wafer, photolithography, thin film sputtering, and liftoff. Following fabrication, the top and bottom electrodes are covalently bonded by a single molecule magnet (SMM) on the exposed side edges for strong magnetic coupling that changes the magnetic properties of both ferromagnetic metals. This study has considered different thin film deposition materials, configurations, and thicknesses. Magnetic field resonance and light reflectance measurements have been performed before and after molecule attachment to understand the molecule effect on the metamaterials’ energy absorption behavior. The Electron Spin Resonance (ESR) test revealed that the devices shifted following molecule attachment in both acoustic and optical modes. Moreover, due to molecule attachment, there have been significant alterations in the MTJ’s electromagnetic wave absorption characteristics with about 49% less reflectance. This metamaterial has various potential applications in aerospace, renewable energy, sensing, imaging, and communication. It is also a cheaper alternative to traditional solar cells and can inspire the development of smart metamaterials with selective absorption and tunable response. 

Abstract Understanding the magnetic molecules’ interaction with different combinations of metal electrodes is vital to advancing the molecular spintronics field. This paper describes experimental and theoretical understanding showing how paramagnetic single-molecule magnet (SMM) catalyzes long-range effects on metal electrodes and, in that process, loses its basic magnetic properties. For the first time, our Monte Carlo simulations, verified for consistency with regards to experimental studies, discuss the properties of the whole device and a generic paramagnetic molecule analog (GPMA) connected to the combinations of ferromagnet-ferromagnet, ferromagnet-paramagnet, and ferromagnet-antiferromagnet metal electrodes. We studied the magnetic moment vs. magnetic field of GPMA exchange coupled between two metal electrodes along the exposed side edge of cross junction-shaped magnetic tunnel junction (MTJ). We also studied GPMA-metal electrode interfaces’ magnetic moment vs. magnetic field response. We have also found that the MTJ dimension impacted the molecule response. This study suggests that SMM spin at the MTJ exposed sides offers a unique and high-yield method of connecting molecules to virtually endless magnetic and nonmagnetic electrodes and observing unprecedented phenomena in the molecular spintronics field. 

Abstract The current study investigates electroless nickel plating and surface finishing techniques such as ChemPolishing (CP) and ElectroPolishing (EP) for postprocessing on additively manufactured stainless-steel samples. Existing additive manufacturing (AM) technologies generate metal components with a rough surface that typically exhibit fatigue characteristics, resulting in component failure and undesirable friction coefficients on the printed part. Small cracks formed in rough surfaces at high surface roughness regions act as a stress raiser or crack nucleation site. As a result, the direct use of as-produced parts is limited, and smoothening the Surface presents a challenge. Previous research has shown that CP ChemPolishing has a significant advantage in producing uniform, smooth surfaces regardless of size or part geometry. EP Electropolishing has a high material removal rate and an excellent surface finishing capability. Electropolishing, on the other hand, has some limitations in terms of uniformity and repeatability. On additively manufactured stainless-steel samples, electroless nickel deposition has a higher plating potential. Nickel has excellent wear resistance, and nickel-plated samples are more robust as scratch resistant than not plated samples when tested for scratch resistance. This research uses medium-phosphorus (6–9% P) and high-phosphorus (10–13% P). The L9 Taguchi design of experiments (DOE) was used to optimize the electroless nickel deposition experiments. The mechanical properties of as-built and nickel-coated additive manufacturing (AM) samples were investigated using a standard 5 N scratch test and the adhesion test ASTM B-733 thermal shock method. The KEYENCE Digital Microscope VHX-7000 was used to examine the pre- and post-processed surfaces of the AM parts. The complete scratch and Design of Experiment (DOE) analysis was performed using the Qualitek-4 software. This work is in progress concerning testing the optimum conditions, completing measurements, and analyzing the results. 

Abstract GaAs is well known for its extremely high electron mobility and direct band gap. Owing to the technological advances in silicon-based technology, GaAs has been limited to niche areas. This paper discusses the application of GaAs in molecular electronics and spintronics as a potential field for considering this amazing but challenging material. GaAs is challenging because its surface is characterized by a high density of surface states, which precludes the utilization of this semiconducting material in mainstream devices. Sulfur(S)-based passivation has been found to be significantly useful for reducing the effect of dangling bonds and was researched thoroughly. GaAs applications in molecular spintronics and electronics can benefit significantly from prior knowledge of GaAs and S interactions because S is a popular functional group for bonding molecular device elements with different semiconductors and metals. In this article, the problem associated with the GaAs surface is discussed in a tutorial form. A wide variety of surface passivation methods has been briefly introduced. We attempted to highlight the significant differences in the S-GaAs interactions for different S passivation methods. We also elaborate on the mechanisms and atomic-scale understanding of the variation in surface chemistry and reconstruction due to various S passivation methods. It is envisioned that GaAs and thiol-terminated molecule-based novel devices can exhibit innovative device characteristics and bring the added advantage of S-based passivation. 

Abstract This research investigates the feasibility of electroless nickel deposition on additively manufactured stainless steel samples. The prevalent additive manufacturing techniques for metal components generate a surface with rough characteristics, which can result in a higher likelihood of fatigue and the initiation of cracks or fractures in the printed part. As a result, using as-manufactured components in the final product is impractical, which requires post-processing to create a smoother surface. This study assesses chempolishing (CP) and Electropolish (EP) techniques for post-processing additively manufactured stainless steel components. CP is a purely chemical process that involves continuous anodization of the sample, resulting in oxidation-reduction. CP has a significant advantage in creating a uniform and smooth surface, irrespective of the size or geometry of the component. Conversely, EP is an electrochemical process that necessitates an electric current to facilitate polishing. EP produces an exceptionally smooth surface that reduces surface roughness to a sub-micrometer level. We observed that EP and CP techniques reduced the surface roughness’s arithmetical mean height (Ra) by up to 4 μm and 10 μm, respectively. In this study, we investigate the application of electroless nickel deposition on additively manufactured (AM) components using different surface finishing techniques, including electro-polishing (EP), chemo-polishing (CP), and as-built components. Electroless nickel plating aims to enhance the surface hardness and resistance of manufactured components to withstand harsh environmental conditions. The electroless nickel plating process is less complicated than electroplating and does not require using an electric current through the chemical bath solution for nickel deposition. For this study, we used low-phosphorus (2–5% P), medium-phosphorus (6–9% P), and high-phosphorus (10–13% P) nickel solutions. We used the L9 Taguchi design of experiments (TDOE) to optimize these Ni deposition experiments, which consider solution content, surface finish, geometry plane, and bath temperature. The pre- and post-processed surfaces of the AM parts were analyzed using the KEYENCE Digital Microscope VHX-7000 and Phenom XL Desktop SEM. We apply a machine learning-based instance segmentation technique to improve the identification of nickel deposition and surface topology of microscopic images. Our experiments show that electroless nickel deposition produces uniform Ni coating on the additively manufactured components at up to 20 μm per hour. Mechanical properties of as-built and Ni-coated AM samples were evaluated using a standard 10 N scratch test. It was found that the nickel-coated AM samples were up to two times more scratch-resistant than the as-built samples. Based on our findings, we conclude that electroless nickel plating is a robust and viable option for surface hardening and finishing AM components for various applications and operating conditions. 

Abstract Magnetic tunnel junction-based molecular spintronics device (MTJMSD) may enable novel magnetic metamaterials by chemically bonding magnetic molecules and ferromagnets (FM) with a vast range of magnetic anisotropy. MTJMSD have experimentally shown intriguing microscopic phenomenon such as the development of highly contrasting magnetic phases on a ferromagnetic electrode at room temperature. This paper focuses on Monte Carlo Simulations (MCS) on MTJMSD to understand the potential mechanism and explore fundamental knowledge about the impact of magnetic anisotropy. The selection of MCS is based on our prior study showing the potential of MCS in explaining experimental results (Tyagi et al. in Nanotechnology 26:305602, 2015). In this paper, MCS is carried out on the 3D Heisenberg model of cross-junction-shaped MTJMSDs. Our research represents the experimentally studied cross-junction-shaped MTJMSD where paramagnetic molecules are covalently bonded between two FM electrodes along the exposed side edges of the magnetic tunnel junction (MTJ). We have studied atomistic MTJMSDs properties by simulating a wide range of easy-axis anisotropy for the case of experimentally observed predominant molecule-induced strong antiferromagnetic coupling. Our study focused on understanding the effect of anisotropy of the FM electrodes on the overall MTJMSDs at various temperatures. This study shows that the multiple domains of opposite spins start to appear on an FM electrode as the easy-axis anisotropy increases. Interestingly, MCS results resembled the experimentally observed highly contrasted magnetic zones on the ferromagnetic electrodes of MTJMSD. The magnetic phases with starkly different spins were observed around the molecular junction on the FM electrode with high anisotropy.