Mesoporous copper-doped δ-MnO2 superstructures to enable high-performance aqueous zinc-ion batteries.

Aqueous zinc-ion batteries (AZIBs) are competitive alternatives for large-scale energy-storage devices owing to the abundance of zinc and low cost, high theoretical specific capacity, and high safety of these batteries. High-performance and stable cathode materials in AZIBs are the key to storing Zn2+. Manganese-based cathode materials have attracted considerable attention because of their abundance, low toxicity, low cost, and abundant valence states (Mn2+, Mn3+, Mn4+, and Mn7+). However, as a typical cathode material, birnessite-MnO2 (δ-MnO2) has low conductivity and structural instability. The crystal structure may undergo severe distortion, disorder, and structural damage, leading to severe cyclic instability. In addition, its energy-storage mechanism is still unclear, and most of the reported manganese oxide-based materials do not have excellent electrochemical performance. Herein, we propose a copper-doped Cu0.05K0.11Mn0.84O2·0.54H2O (Cu2-KMO) cathode, which exhibits a large interlayer spacing, a stable structure, and accelerated reaction kinetics. This cathode was prepared using a simple hydrothermal method. The AZIB assembled using Cu2-KMO showed high specific capacity (600 mA h g-1 at 0.1 A g-1 after 75 cycles). The dissolution-deposition energy storage mechanism of Cu-KMO in AZIBs with double electron transfer was revealed using ex situ tests. The good electrochemical performance of the Cu2-KMO cathode fabricated by the doping strategy in this study provides ideas for the subsequent preparation of manganese dioxide using other strategies.

Study on the mechanism of carbon nanotube-like carbon deposition in tar catalytic reforming over Ni-based catalysts.

The use of Ni-based catalysts is a common method for eliminating tar through catalytic cracking. Carbon deposition is the main cause of deactivation in Ni/ZSM-5 catalysts, with filamentous MWCNTs being the primary form of carbon deposits. This study investigates the formation and evolution of CNTs during the catalytic process of biomass tar to explore the mechanism behind carbon deposition. The effect of the 9Ni/10MWCNTs/81ZSM-5 on toluene reforming was investigated through a vertical furnace. Gases produced by tar catalysis were evaluated through GC analysis. The physicochemical structure, properties and catalytic performance of the catalyst were also tested. TG analysis was used to assess the accumulation and oxidation reactivity of carbon on the catalyst surface. An analysis was conducted on the mechanism of carbon deposition during catalyst deactivation in tar catalysis. The results showed that the 9Ni/91ZSM-5 had a superior toluene conversion of 60.49%, but also experienced rapid and substantial carbon deposition up to 52.69%. Carbon is mainly deposited as curved filaments on both the surface and pore channels of the catalyst. In some cases, tip growth occurs where both carbon deposition and Ni coexist. Furthermore, specific surface area and micropore volume are reduced to varying degrees due to carbon deposition. With the time increased, the amount of carbon deposited on the catalyst surface increased to 62.81%, which gradually approached saturation, and the overall performance of the catalyst was stabilized. This situation causes toluene molecules to detach from the active sites within the catalyst, hindering gas release, which leads to reduced catalytic activity and further carbon deposition. It provides both a basis for the development of new catalysts and an economically feasible solution for practical tar reduction and removal.

Revealing the Deposition Mechanism of the Powder Aerosol Deposition Method Using Ceramic Oxide Core-Shell Particles.

The powder aerosol deposition (PAD) method is a process to manufacture ceramic films completely at room temperature. Since the first reports by Akedo in the late 1990s, much research has been conducted to reveal the exact mechanism of the deposition process. However, it is still not fully understood. This work tackles this challenge using core-shell particles. Two coated oxides, Al2 O3 core with a SiO2 shell and LiNi0.6 Mn0.2 Co0.2 O2 core with a LiNbO3 shell, are investigated. Initially, the element ratios Al:Si and Ni:Nb of the powder are determined by energy-dispersive X-ray spectroscopy (EDX). In a second step, the change in the element ratios of Al:Si and Ni:Nb after deposition is investigated. The element ratios from powder to film strongly shift toward the shell elements, indicating that the particles fracture and only the outer parts of the particles are deposited. In the last step, this work investigates cross-sections of the deposited films with scanning transmission electron microscopy (STEM combined with EDX and an energy-selective back-scattered electron (EsB) detector to unveil the element distribution within the film itself. Therefore, the following overall picture emerges: particles impact on the substrate or on previously deposited particle, fracture, and only a small part of the impacting particles that originate from the outer part of the impacting particle gets deposited.

Revealing the Dominance of the Dissolution-Deposition Mechanism in Aqueous Zn-MnO2 Batteries.

Zn-MnO2 batteries have attracted extensive attention for grid-scale energy storage applications, however, the energy storage chemistry of MnO2 in mild acidic aqueous electrolytes remains elusive and controversial. Using α-MnO2 as a case study, we developed a methodology by coupling conventional coin batteries with customized beaker batteries to pinpoint the operating mechanism of Zn-MnO2 batteries. This approach visually simulates the operating state of batteries in different scenarios and allows for a comprehensive study of the operating mechanism of aqueous Zn-MnO2 batteries under mild acidic conditions. It is validated that the electrochemical performance can be modulated by controlling the addition of Mn2+ to the electrolyte. The method is utilized to systematically eliminate the possibility of Zn2+ and/or H+ intercalation/de-intercalation reactions, thereby confirming the dominance of the MnO2 /Mn2+ dissolution-deposition mechanism. By combining a series of phase and spectroscopic characterizations, the compositional, morphological and structural evolution of electrodes and electrolytes during battery cycling is probed, elucidating the intrinsic battery chemistry of MnO2 in mild acid electrolytes. Such a methodology developed can be extended to other energy storage systems, providing a universal approach to accurately identify the reaction mechanism of aqueous aluminum-ion batteries as well.

Routes to Electrochemically Stable Sulfur Cathodes for Practical Li-S Batteries.

Lithium-sulfur (Li-S) batteries have been investigated intensively as a post-Li-ion technology in the past decade; however, their realizable energy density and cycling performance are still far from satisfaction for commercial development. Although many extremely high-capacity and cycle-stable S cathodes and Li anodes are reported in literature, their use for practical Li-S batteries remains challenging due to the huge gap between the laboratory research and industrial applications. The laboratory research is usually conducted by use of a thin-film electrode with a low sulfur loading and high electrolyte/sulfur (E/S) ratios, while the practical batteries require a thick/high sulfur loading cathode and a low E/S ratio to achieve a desired energy density. To make this clear, the inherent problems of dissolution/deposition mechanism of conventional sulfur cathodes are analyzed from the viewpoint of polarization theory of porous electrode after a brief overview of the recent research progress on sulfur cathodes of Li-S batteries, and the possible strategies for building an electrochemically stable sulfur cathode are discussed for practically viable Li-S batteries from the authors' own understandings.

Particle Deposition in Large-Scale Human Tracheobronchial Airways Predicted by Single-Path Modelling.

The health effects of particles are directly related to their deposition patterns (deposition site and amount) in human airways. However, estimating the particle trajectory in a large-scale human lung airway model is still a challenge. In this work, a truncated single-path, large-scale human airway model (G3-G10) with a stochastically coupled boundary method were employed to investigate the particle trajectory and the roles of their deposition mechanisms. The deposition patterns of particles with diameters (dp) of 1-10 µm are investigated under various inlet Reynolds numbers (Re = 100-2000). Inertial impaction, gravitational sedimentation, and combined mechanism were considered. With the increasing airway generations, the deposition of smaller particles (dp < 4 µm) increased due to gravitational sedimentation, while that of larger particles decreased due to inertial impaction. The obtained formulas of Stokes number and Re can predict the deposition efficiency due to the combined mechanism in the present model, and the prediction can be used to assess the dose-effect of atmospheric aerosols on the human body. Diseases in deeper generations are mainly attributed to the deposition of smaller particles under lower inhalation rates, while diseases at the proximal generations mainly result from the deposition of larger particles under higher inhalation rates.

Numerical and Experimental Investigations of Cold-Sprayed Basalt Fiber-Reinforced Metal Matrix Composite Coating.

The aluminum-basalt fiber composite coating was prepared for the first time with basalt fiber as the spraying material by cold-spraying technology. Hybrid deposition behavior was studied by numerical simulation based on Fluent and ABAQUS. The microstructure of the composite coating was observed on the as-sprayed, cross-sectional, and fracture surfaces by SEM, focusing on the deposited morphology of the reinforcing phase basalt fibers in the coating, the distribution of basalt fibers, and the interaction between basalt fibers and metallic aluminum. The results show that there are four main morphologies of the basalt fiber-reinforced phase, i.e., transverse cracking, brittle fracture, deformation, and bending in the coating. At the same time, there are two modes of contact between aluminum and basalt fibers. Firstly, the thermally softened aluminum envelops the basalt fibers, forming a seamless connection. Secondly, the aluminum that has not undergone the softening effect creates a closed space, with the basalt fibers securely trapped within it. Moreover, the Rockwell hardness test and the friction-wear test were conducted on Al-basalt fiber composite coating, and the results showed that the composite coating has high wear resistance and high hardness.

Effect of Substrates Performance on the Microstructure and Properties of Phosphate Chemical Conversion Coatings on Metal Surfaces.

Phosphate chemical conversion (PCC) technology has attracted extensive attention for its ability to regulate the surface properties of biomedical metals. However, titanium (Ti)-based alloys exhibit inertia because of the native passive layer, whereas zinc (Zn)-based alloys show high activity in acidic PCC solutions. The substrate performance affects the chemical reaction in the phosphating solution, which further leads to diversity in coating properties. In this work, the zinc-phosphate (ZnP) coatings are prepared on Ti alloy (TA) and Zn alloy (ZA) substrates using the PCC method, respectively. The coatings prepared herein are detected by a scanning electron microscope (SEM), X-ray diffractometer (XRD), laser scanning confocal microscope (LSCM), universal testing machine, contact angle goniometer, and electrochemical workstation system. The results show that the substrate performance has little effect on the phase composition but can significantly affect the crystal microstructure, thickness, and bonding strength of the coatings. In addition, the ZnP coatings improve the surface roughness of the substrates and show good hydrophilicity and electrochemical corrosion resistance. The formation mechanism of the ZnP coating is revealed using potential-time curves, indicating that the metal-solution interfacial reaction plays a dominant role in the deposition process.

Cloudwater Deposition Process of Radionuclides Based on Water Droplets Retrieved from Pollen Sensor Data.

Radionuclides released during the Fukushima Daiichi nuclear accident caused altitude-dependent surface contamination in the mountainous areas of Japan. To explore the possible cloudwater deposition that formed a distinctive contamination profile, data from pollen sensors deployed nationwide were analyzed. Utilizing the polarization of scattered light, Cedar pollen and water droplets were distinguished. On March 15, when surface contamination was simulated in previous studies, dense clouds with high droplet number concentrations were observed outside the 137Cs surface deposition areas, indicating that the sensor sites were immersed amid cloud layers. In contrast, cloud droplets with moderate number concentrations were measured at altitudes of approximately 570-840 m, which overlapped with the surface contamination areas. Considering the existing knowledge on vertical gradients of cloudwater composition, these suggest that contaminated cloud droplets were localized near the cloud base where a moderate number concentration of cloud droplets was measured. A formation process was proposed for the observed vertical distribution, that is, surface contamination occurred intensively at the contact line between the cloud base and mountain slopes via cloudwater deposition, and the descending cloud base formed the contamination zone. This study sheds light on the deposition processes of radionuclides, which have not previously been clarified.

Metallization on Sapphire and Low-Temperature Joining with Metal Substrates.

To meet the packaging requirements of sapphire in special electronic components, there is an urgent need for a joining process that can realize a good connection between sapphire and dissimilar metals at a low temperature. In this work, the surface of a sapphire substrate was successfully catalytically activated and metallized by an electroless nickel plating process. Moreover, the solderability and interconnection of metallized sapphire with Sn-based solders were evaluated and investigated at 250 °C, and the wetting angle of the Sn-based solders on sapphire on sapphire without and with metallization was 125° and 51°, respectively. The interfacial microscopic morphology and element distribution in the Cu/Sn-Ag solder/sapphire solder joints were analyzed. It was found that the middle solder layer has diffused during the reflow process, inferring good adhesion between sapphire and Cu substrate with the aid of the Ni-P deposition. Thus, a sapphire welding method with a simple process suitable for practical applications is demonstrated.

Modeling of Electron-Transfer Kinetics in Magnesium Electrolytes: Influence of the Solvent on the Battery Performance.

The performance of rechargeable magnesium batteries is strongly dependent on the choice of electrolyte. The desolvation of multivalent cations usually goes along with high energy barriers, which can have a crucial impact on the plating reaction. This can lead to significantly higher overpotentials for magnesium deposition compared to magnesium dissolution. In this work we combine experimental measurements with DFT calculations and continuum modelling to analyze Mg deposition in various solvents. Jointly, these methods provide a better understanding of the electrode reactions and especially the magnesium deposition mechanism. Thereby, a kinetic model for electrochemical reactions at metal electrodes is developed, which explicitly couples desolvation to electron transfer and, furthermore, qualitatively takes into account effects of the electrochemical double layer. The influence of different solvents on the battery performance is studied for the state-of-the-art magnesium tetrakis(hexafluoroisopropyloxy)borate electrolyte salt. It becomes apparent that not necessarily a whole solvent molecule must be stripped from the solvated magnesium cation before the first reduction step can take place. For Mg reduction it seems to be sufficient to have one coordination site available, so that the magnesium cation is able to get closer to the electrode surface. Thereby, the initial desolvation of the magnesium cation determines the deposition reaction for mono-, tri- and tetraglyme, whereas the influence of the desolvation on the plating reaction is minor for diglyme and tetrahydrofuran. Overall, we can give a clear recommendation for diglyme to be applied as solvent in magnesium electrolytes.

Growth Mechanisms and the Effects of Deposition Parameters on the Structure and Properties of High Entropy Film by Magnetron Sputtering.

Despite intense research on high entropy films, the mechanism of film growth and the influence of key factors remain incompletely understood. In this study, high entropy films consisting of five elements (FeCoNiCrAl) with columnar and nanometer-scale grains were prepared by magnetron sputtering. The high entropy film growth mechanism, including the formation of the amorphous domain, equiaxial nanocrystalline structure and columnar crystal was clarified by analyzing the microstructure in detail. Besides, the impacts of the important deposition parameters including the substrate temperature, the powder loaded in the target, and the crystal orientation of the substrate on the grain size and morphology, phase structure, crystallinity and elemental uniformity were revealed. The mechanical properties of high entropy films with various microstructure features were investigated by nanoindentation. With the optimized grain size and microstructure, the film deposited at 350 °C using a power of 100 W exhibits the highest hardness of 11.09 GPa. Our findings not only help understanding the mechanisms during the high entropy film deposition, but also provide guidance in manufacturing other novel high entropy films.

Gadolinium Deposition in the Brain: Current Updates.

Gadolinium-based contrast agents (GBCAs) are commonly used for enhancement in MR imaging and have long been considered safe when administered at recommended doses. However, since the report that nephrogenic systemic fibrosis is linked to the use of GBCAs in subjects with severe renal diseases, accumulating evidence has suggested that GBCAs are not cleared entirely from our bodies; some GBCAs are deposited in our tissues, including the brain. GBCA deposition in the brain is mostly linked to the specific chelate structure of the GBCA: linear GBCAs were responsible for brain deposition in almost all reported studies. This review aimed to summarize the current knowledge about GBCA brain deposition and discuss its clinical implications.

Fabrication and characterization of Ni-decorated h-BN powders with ChCl-EG ionic liquid as addition by electroless deposition.

Ni-decorated h-BN powders are fabricated with ChCl-EG as additive via electroless plating in the paper. As comparison, the different additive concentration of choline chloride-ethylene glycol (ChCl-EG) ionic liquid (0 g l-1, 30 g l-1, 60 g l-1, 90 g l-1) is presented. The effects of ChCl-EG concentration are studied, including the surface morphologies, phase analysis of Ni-decorated h-BN powders and the residual Ni2+ concentration is measured in electroless plating bath. It is demonstrated that the deposition phenomena of nickel particles on h-BN surface is changed with the addition of ChCl-EG. When the concentration of ChCl-EG is 30 g l-1, the Ni particles on h-BN surface are in dispersed and spheroid state with the average size of 10-1000 nm. It can be found that 30 g l-1 ChCl-EG is conducive to the arise of deposition phenomena, which is the formation of the single nickel particle on h-BN surface. Besides, more Ni particles are deposited on h-BN surface with the increase of nickel plating times, which is characterized with scanning electron microscope and transmission electron microscope. Furthermore, the deposition phenomenon and growth mechanism are proposed without and with ChCl-EG as additive to further elaborate the formation of Ni particles on h-BN surface.

Altitudinal characteristics of atmospheric deposition of aerosols in mountainous regions: Lessons from the Fukushima Daiichi Nuclear Power Station accident.

To understand the formation process of radiologically contaminated areas in eastern Japan caused by the Fukushima Daiichi Nuclear Power Station (FDNPS) accident, the deposition mechanisms over complex topography are the key factors to be investigated. To characterize the atmospheric deposition processes of radionuclides over complex mountainous topography, we investigated the altitudinal distributions of the radiocesium deposited during the accident. In five selected areas, altitudinal characteristics of the air dose rates observed using airborne surveys were analyzed. To examine the deposition mechanisms, we supplementarily used vertical profiles of radiocesium deposition in each area calculated in the latest atmospheric dispersion model. In southern Iwate, the vertical profile of the observed air dose rate was uniform regardless of altitude. In western Tochigi, the areas with the highest levels of contamination were characteristically distributed in the middle of the mountains, while in southern Fukushima, the areas with the highest contamination levels were enhanced near the summits of mountains. In central Fukushima, high air dose rates were limited to the bottoms of basin-like valley. In the region northwest of FDNPS, the air dose rate was the highest at the bottom of valley topography and decreased gradually with altitude. The simulation results showed that calculated wet deposition and observed vertical profiles of total deposition were similar in areas of southern Iwate and northwest of FDNPS qualitatively, suggesting that the dominant deposition mechanism was wet deposition. In contrast, the atmospheric dispersion model failed to reproduce either the timing of precipitation events or vertical profiles of radiocesium deposition in three other areas. Although it was difficult to elucidate the deposition mechanisms in these areas due to uncertainties of the present model results, potential mechanisms such as cloud water deposition were still proposed based on circumstantial evidences of limited meteorological data during the early stage of the accident.

Deposition and Adhesion of Polydopamine on the Surfaces of Varying Wettability.

Mussel-inspired chemistry, particularly the versatile coating capability of polydopamine (PDA), has received much research interest as a promising strategy for fabricating functional coatings in numerous fields. However, the understanding of deposition mechanisms and adhesion behaviors of PDA on different substrates still remains incomplete, significantly limiting the related fundamental research and its practical applications. In this work, a colloidal probe atomic force spectroscopy technique was employed to quantify the interaction forces and adhesion between the PDA coatings and the substrate surfaces with different wettabilities. The surface force measurements and thermodynamic analysis of interaction energy indicate that the surface wettability has a significant influence on the adhesion, deposition behaviors, and morphologies of PDA coatings. Compared with the hydrophilic surfaces, the hydrophobic surfaces exhibit stronger adhesion with the PDA coatings. Furthermore, for the first time, this work demonstrates that ethanol has the capability of effectively displacing the trapped air/vapor layer or the so-called "hydrophobic depletion layer" on the hydrophobic substrate to allow the intimate contact between PDA and the substrate, thus enhancing the adhesion and facilitating the PDA deposition. This work provides new insights into the fundamental PDA deposition mechanism as well as the design and development of versatile mussel-inspired coatings on the substrates of varying hydrophobicity.

Effect of the SiCl4 Flow Rate on SiBN Deposition Kinetics in SiCl4-BCl3-NH3-H2-Ar Environment.

To improve the thermal and mechanical stability of SiCf/SiC or C/SiC composites with SiBN interphase, SiBN coating was deposited by low pressure chemical vapor deposition (LPCVD) using SiCl4-BCl3-NH3-H2-Ar gas system. The effect of the SiCl4 flow rate on deposition kinetics was investigated. Results show that deposition rate increases at first and then decreases with the increase of the SiCl4 flow rate. The surface of the coating is a uniform cauliflower-like structure at the SiCl4 flow rate of 10 mL/min and 20 mL/min. The surface is covered with small spherical particles when the flow rate is 30 mL/min. The coatings deposited at various SiCl4 flow rates are all X-ray amorphous and contain Si, B, N, and O elements. The main bonding states are B-N, Si-N, and N-O. B element and B-N bonding decrease with the increase of SiCl4 flow rate, while Si element and Si-N bonding increase. The main deposition mechanism refers to two parallel reactions of BCl3+NH3 and SiCl4+NH3. The deposition process is mainly controlled by the reaction of BCl3+NH3.