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Electroless coating brings the advantage of providing films on the complex geometry of additively manufactured components. However, there is a knowledge gap about the impact of AM part surface and postprocessing parameters on the quality of electroless coating. This study explores the application of three solution-based surface finishing techniques on the microstructure and surface hardness of additively manufactured stainless steel components coated with electroless nickel films. Given that AM techniques for metal parts often yield surfaces with inherently rough textures and differences in properties along the different planes, we investigated their relationship with nickel coating. To mitigate the impact of surface irregularities on electroless nickel coating quality, this research evaluated the effectiveness of chemical polishing (CP) and Electropolishing (EP) as post-processing treatments for AM stainless steel. Characterization of the treated samples was conducted using the analytical Digital Microscope, Scanning Electron Microscope (SEM), and scratch tester. Additionally, the study incorporated an instant segmentation machine learning algorithm to overcome image analysis challenges. The findings indicate that EP and CP significantly improve surface smoothness, decreasing the arithmetical mean height (Ra) by as much as 4 µm and 10 µm, respectively. Furthermore, the nickel-coated AM samples demonstrated an enhancement in scratch resistance, exhibiting up to a two-fold increase in surface hardness compared to their as-built counterparts. Taguchi design of the experiment was applied to investigate the effect of process parameters. This study provides insights for developing improved surface quality and acquiring new properties via the coating process to make AM parts suitable for challenging environments and novel applications. 

The study focuses on the observation of the photovoltaic (PV) effect on Si/AlOx/FM semiconductor–insulator–ferromagnetic metal (SIFM) structure. Utilization of ∼10 nm NiFe film as the top ferromagnet (FM) layer was permeable for sufficient light radiation necessary for reaching the silicon substrate for the generation of electron–hole pairs upon photoexcitation. The effect of light intensity and magnetic field was studied on the SIFM’s PV response. We also investigated the role of silicon doping and the AlOx tunnel barrier between Si and FM in exploring suitable band bending necessary for separating the electron–hole pairs. Increasing the dopant density in Si and a damaged AlOx tunnel barrier quenched the PV effect. Ferromagnet/Insulator/Ferromagnet (FMIFM) was also studied to gain deeper mechanistic insights into the spin-dependent photovoltaic effect observed on FM/AlOx/FM tunnel junction-based molecular spintronics devices. Bridging of magnetic molecules between the Si and FM electrodes of SIFM increased the overall device current by establishing additional parallel conduction channels along with the AlOx tunnel barrier. However, SIFM with molecular conduction channels did not produce a PV effect. This study reported the PV effect on well-designed SIFM and opened possibilities for exploring new systems. More importantly, this paper provided insights into the role of molecule-induced exchange coupling in transforming an ordinary, cheap, and widely available ferromagnet into a semiconductor-like material capable of showing PV.

 

In this paper, electroless nickel plating is explored for the protection of binder-jetting-based additively manufactured (AM) composite materials. Electroless nickel plating was attempted on binder-jetted composites composed of stainless steel and bronze, resulting in differences in the physicochemical properties. We investigated the impact of surface finishing, plating solution chemistry, and plating parameters to attain a wide range of surface morphologies and roughness levels. We employed the Keyence microscope to quantitatively evaluate dramatically different surface properties before and after the coating of AM composites. Scanning electron microscopy revealed a wide range of microstructural properties in relation to each combination of surface finishing and coating parameters. We studied chempolishing, plasma cleaning, and organic cleaning as the surface preparation methods prior to coating. We found that surface preparation dictated the surface roughness. Taguchi statistical analysis was performed to investigate the relative strength of experimental factors and interconnectedness among process parameters to attain optimum coating qualities. The quantitative impacts of phosphorous level, temperature, surface preparation, and time factor on the roughness of the nickel-plated surface were 17.95%, 8.2%, 50.02%, and 13.21%, respectively. On the other hand, the quantitative impacts of phosphorous level, temperature, surface preparation, and time factor on the thickness of nickel plating were 35.12%, 41.40%, 3.87%, and 18.24%, respectively. The optimum combination of the factors’ level projected the lowest roughness of Ra at 7.76 µm. The optimum combination of the factors’ level projected the maximum achievable thickness of ~149 µm. This paper provides insights into coating process for overcoming the sensitivity of AM composites in hazardous application spaces via robust coating.

 

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.

 

The intra-molecular coupling within multiple units of paramagnetic molecules can produce various effects on molecular spintronics devices (MSD). This paper focuses on double-segmented molecules as the device element to advance understanding of the Impact of internal molecular structure on magnetic tunnel junction-based MSD (MTJMSD). We performed Monte Carlo simulations (MCS) to fill the knowledge gap about the intramolecular coupling role in the magnetic properties of the MTJMSD. This study explored a double-segmented molecule containing two atomic sections, each with a net spin state interacting via Heisenberg exchange coupling within molecules and with ferromagnetic electrodes at different thermal energies, magnetic fields, and coupling strengths. This study also investigated the effect of magnetic field on the double-segmented molecule-based cross-junction-shaped MTJMSD. We also compared the effect of the magnetic field on the mono and double-segmented molecules when connected to two ferromagnetic electrodes. In the strong coupling regime, the intramolecular coupling and molecule coupling with the two ferromagnetic electrodes dominated the MTJMSD response near the molecular junction area. This study provides insight for evaluating the Impact of molecular nanostructure internal connectedness on the integrated MSD. 

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.

 

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.

 

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.

 

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.

 

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.