Search Results (7)

Electrochromism induces reversible changes of coloration in specific organic and inorganic materials through electrical charge/discharge reactions. When processed into thin films, electrochromic metal oxides can be integrated into glazing applications such as displays, rearview mirrors, goggles and, most notably, smart windows in energy-efficient buildings. Over the years, the use of spray coating as a liquid-based approach has been acknowledged for its cost-efficient, high-throughput samples production with a low volume consumption. It represents an interesting alternative to vacuum processes and to other wet methods, suitably responding to the current limitations of electrochromic thin films production by offering improved control over deposition parameters and capacities of up-scaling, together with lowered energetic and economic costs. The present review summarizes the main theoretical and practical aspects of spray coating, notably distinguishing room-temperature methodologies from pyrolysis-based, under heating protocols. The main families of functional electrochromic metal oxides are then screened and discussed, establishing how spray processing can challengingly lead to higher levels of optical contrast, commutation kinetics, coloration efficiency and cycling durability, and how low-toxic and environment-friendly precursors can be favored while sustaining large deposition areas. Full article

In this paper, we design a kind of negative pressure vacuum recovery hood, arranged at the front of the spray gun nozzle by CFD simulation; this addresses the paint mist pollution problem of the robot spraying on the outer plate of the ship, and the nozzle is arranged at the center of the recovery hood. Three vacuum recovery hood schemes are designed as follows: Scheme A, a hemispherical recovery hood with a diameter of 1.2 m; Scheme B, with a diameter of 1.6 m; Scheme C, with a diameter of 2.0 m. The recovery vacuum suction holes of the three recovery hoods are arranged differently. Firstly, a mathematical model of the spraying jet for the case of 0.48 mm diameter nozzle was established, and the established nozzle jet flow field model was verified to be feasible through case simulation analysis and experimental comparison. Secondly, a detailed discussion and analysis of the simulation process was conducted focusing on Scheme A. During the simulation of Scheme A, it was found that: the air velocity at the inlet surface and the kinetic energy of the paint mist had a large impact on the simulation effect, so it is necessary to try to further improve the structure of the recovery hood. Finally, the further simulation analysis of Scheme B and Scheme C shows that Scheme C > Scheme B > Scheme A in terms of the paint mist recovery effect. It can be seen that the use of Scheme C as a shipyard robotic spray paint mist recovery shows better results, which provides a theoretical scheme for shipyards to achieve paint mist anti-fouling as soon as possible. Full article

This work shows that the powder aerosol deposition (PAD) method allows the formation of films in powder quantities of less than 60 mg, rather than the large amounts that are typically required for conventional powder aerosol deposition systems. This was achieved by changing the operation mode to a discontinuous one, resulting in operation times of several seconds. Semiconducting strontium titanate ferrate SrTi_0.65Fe_0.35O_3−δ (STF35) was used as the powder to prove the equal behavior in terms of adhesion, film quality and electric conductivity compared to conventional powder-aerosol-deposited films. Full article

The powder aerosol deposition method (PAD) is a vacuum-based spray coating technology. It allows for production of highly dense coatings at room temperature, especially of brittle-breaking materials. This yields new options for coating substrate materials that even melt at low temperatures. The film formation mechanism is called room temperature impact consolidation (RTIC). The occurrence of this mechanism is strongly linked to the gas jet used in the process. The velocity and direction of the particles in the gas jet forming between the nozzle orifice and the substrate are the main factors influencing the quality of the coating. This dependency aimed to be elaborated with a measurement setup and coating experiments and is shown in this work. We investigated the gas jet formation using a shadow optical imaging system. Regions of different gas density are visualized by this technique. Several parameter sets, in particular gas flow rates and chamber pressures, were investigated. In addition, coatings were produced on glass substrates with the same parameters. As a coating material, the superconducting ceramic-like magnesium diboride (MgB₂) was chosen. A correlation between shadow images and thickness profiles of the coatings shows how the gas jet formation affects the uniformity of thickness. Shadow optical images provide valuable information on the flight direction of the particles and allow validation of simulation results. Full article

The Aerosol Deposition (AD, also known as gas kinetic spraying or vacuum deposition) method is a rather novel coating process to produce dense thick films directly from dry ceramic (or metal) powders on a variety of substrates without any heat treatment. Because of the similarity of the up to now used powders and lunar regolith, it is imaginable to use AD systems for future in situ resource utilization missions on the Moon planned by several space agencies. To test the feasibility of such an endeavor, the processability of lunar mare simulant EAC-1 by the AD method has been examined in this study. Three regolith films with an area of 25 × 10 mm², and thicknesses between 2.50 µm and 5.36 µm have been deposited on steel substrates using a standard AD setup. Deposited films have been investigated by Laser Scanning Microscopy (LSM) and Scanning Electron Microscopy (SEM). Moreover, the roughness and Vickers hardness of the deposited films and the underlying substrates have been measured. It has been shown that dense consolidated films of regolith simulant can be produced within minutes by AD. The deposited films show a higher roughness and, on average, a higher hardness than the steel substrates. Since on the Moon, naturally available regolith powders are abundant and very dry, and since the required process vacuum is available, AD appears to be a very promising method for producing dense coatings in future Moon exploration and utilization missions. Full article

A few-layer graphene nano-flake thin film was prepared by an affordable vacuum kinetic spray method at room temperature and modest low vacuum conditions. In this economical approach, graphite microparticles, a few layers thick, are deposited on a stainless-steel substrate to form few-layer graphene nano-flakes using a nanoparticle deposition system (NPDS). The NPDS allows for a large area deposition at a low cost and can deposit various metal oxides at room temperature and low vacuum conditions. The morphology and structure of the deposited thin films are alterable by changing the scan speed of the deposition. These changes were verified by field emission scanning electron microscopy (FE-SEM), transmission electron microscopy (TEM), X-ray diffraction (XRD), and Raman spectroscopy. The electrochemical performances of the supercapacitors, fabricated using the deposited films and H₃PO₄–PVA gel electrolytes with different concentrations, were measured using a 2-electrode cell. The electrochemical performance was evaluated by cyclic voltammetry, galvanostatic Charge–discharge, and electrochemical impedance spectroscopy. The proposed affordable fabricated supercapacitors show a high areal capacitance and a small equivalent series resistance. Full article

The pulsed polarization technique on solid electrolytes is based on alternating potential pulses interrupted by self-discharge pauses. Since even small concentrations of nitrogen oxides (NO_x) in the ppm range significantly change the polarization and discharge behavior, pulsed polarization sensors are well suited to measure low amounts of NO_x. In contrast to all previous investigations, planar pulsed polarization sensors were built using an electrolyte thick film and platinum interdigital electrodes on alumina substrates. Two different sensor layouts were investigated, the first with buried Pt electrodes under the electrolyte and the second one with conventional overlying Pt electrodes. Electrolyte thick films were either formed by aerosol deposition or by screen-printing, therefore exhibiting a dense or porous microstructure, respectively. For screen-printed electrolytes, the influence of the electrolyte resistance on the NO_x sensing ability was investigated as well. Sensors with buried electrodes showed little to no response even at higher NO_x concentrations, in good agreement with the intended sensor mechanism. Electrolyte films with overlying electrodes, however, allowed the quantitative detection of NO_x. In particular, aerosol deposited electrolytes exhibited high sensitivities with a sensor output signal ΔU of 50 mV and 75 mV for 3 ppm of NO and NO₂, respectively. For screen-printed electrolytes, a clear trend indicated a decrease in sensitivity with increased electrolyte resistance. Full article