Search Results (36)

Volatile organic compound (VOC) emissions have become a critical environmental concern due to their contributions to photochemical smog formation, secondary organic aerosol generation, and adverse human health impacts in the context of accelerated industrialization and urbanization. Catalytic oxidation over perovskite-type catalysts is an attractive technological approach for efficient VOC abatement. This review systematically evaluates the advancements in perovskite-based catalysts for VOC oxidation, focusing on their crystal structure–activity relationships, electronic properties, synthetic methodologies, and nanostructure engineering. Emphasis is placed on metal ion doping strategies and supported catalyst configurations, which have been demonstrated to optimize catalytic performance through synergistic effects. The applications of perovskite catalysts in diverse oxidation systems, including photocatalysis, thermal catalysis, electrocatalysis, and plasma-assisted catalysis, are comprehensively discussed with critical analysis of their respective advantages and limitations. It summarizes the existing challenges, such as catalyst deactivation caused by carbon deposition, sulfur/chlorine poisoning, and thermal sintering, as well as issues like low energy utilization efficiency and the generation of secondary pollutants. By consolidating current knowledge and highlighting future research directions, this review provides a solid foundation for the rational design of next-generation perovskite catalysts for sustainable VOC management. Full article

High-temperature conditions are harmful for carbon nanotube-based (CNT-based) composites, as CNTs are susceptible to oxidation. On the other hand, adding CNTs to ceramics with low electrical conductivity, such as 3YSZ, is beneficial because it allows the production of complex-shaped samples with spark plasma sintering (SPS). A shielding coating system may be applied to prevent CNT oxidation. In this work, the 8YSZ (yttria-stabilized zirconia) thermal shielding coating system was deposited by aerosol deposition (AD) to improve the composite’s resistance to CNT degradation without the use of bond-coat sublayers. Additionally, the influence of the annealing process on the mechanical properties and microstructure of the composite was evaluated by nanoindentation, scratch tests, scanning electron microscopy (SEM), X-ray diffraction (XRD), flame tests, and light microscopy (LM). Annealing at 1200 °C was the optimal temperature for heat treatment, improving the coating’s mechanical strength (the first critical load increased from 0.84 N to 3.69 N) and promoting diffusion bonding between the compacted powder particles and the substrate. The deposited coating of 8YSZ increased the composite’s thermal resistance by reducing the substrate’s heating rate and preventing the oxidation of CNTs. Full article

In this study, Y₂O₃ coating is used as an interlayer between Al₂O₃ substrate and a ceramic coating; this is in order to minimize the morphological distortion produced by a single deposition of the ceramic coating on the Al₂O₃ substrate, which is performed using the aerosol method. The interlayer coating, which comprises the Y₂O₃ phase, is deposited on the Al₂O₃ substrate using an e-beam evaporator. The crystal structure of the powder that was used to process the coating is identified as cubic Y₂O₃. In contrast, the crystal structure of the top-coating layer and interlayer indicates the presence of two kinds of Y₂O₃ phases, which possess cubic and monoclinic structures. The single Y₂O₃ coating without an interlayer exhibits microcracks around the interface between the coating and the substrate, which can be attributed to the stress that occurs during aerosol deposition. In contrast, no cracks are found in the aerosol-deposited Y₂O₃ coating and interlayer, which show a desirable microstructure. The single Y₂O₃ coating and the Y₂O₃ coating with an interlayer exhibit similar hardness and elastic modulus values. Nevertheless, the Y₂O₃ coating with an interlayer exhibits a higher level of adhesion than the single Y₂O₃ coating, with a value of 14.8 N compared to 10.2 N. Full article

Silk fibroin (SF) has been widely used in biomedical applications for the hydrophilicity modification of high molecular polymer materials. However, the challenge remains to immobilize SF with high structure stability and strong adhesion strength between SF and the substrate. Here, we propose an effective two-step process for modifying polyethylene terephthalate (PET) with SF: dipping PET film in SF solution and subsequently carrying out plasma-assisted deposition in SF aerosol. The structure and property analysis revealed that the SF-modified PET (PET-SF) prepared using the two-step method exhibited superior structural stability and stronger adhesion strength compared to the dip-coating method and the plasma-assisted deposition method. In addition, PET-SF prepared using the two-step method resulted in a higher concentration of SF and an increased content of active groups on its surface, enhancing its hydrophilicity compared to the other two methods. Additionally, the influence of dipping time and deposition time in the two-step method was investigated. The results demonstrated that the dipping time for 6 h and the deposition time for 3 min resulted in maximum SF grafting amount with a highly stable structure. Furthermore, the PET-SF exhibited satisfactory hydrophilicity when the deposition time was more than 3 min and showed the most hydrophilicity surface at 8 min. Full article

The Sahara Desert is the largest contributor of global atmospheric dust aerosols impacting regional climate, health, and ecosystems. The climate effects of these dust aerosols remain uncertain due, in part, to climate model uncertainty of Saharan source region contributions and aerosol microphysical properties. This study distinguishes source region elemental signatures of Saharan dust aerosols sampled during the 2015 Aerosols Ocean Sciences Expedition (AEROSE) in the tropical Atlantic. During the 4-week campaign, cascade impactors size-dependently collected airborne Saharan dust particulate upon glass microfiber filters. Inductively Coupled Plasma Mass Spectrometry (ICP-MS) analysis differentiated metal isotope concentrations within filter samples from various AEROSE dust sampling periods. Back-trajectory analysis and NOAA satellite aerosol optical depth retrievals confirmed source regions of AEROSE ’15 dust samples. Pearson correlational statistics of source region activity and dust isotope concentrations distinguished the elemental signatures of North African potential source areas (PSAs). This study confirmed that elemental indicators of these PSAs remain detectable within dust samples collected far into the marine boundary layer of the tropical Atlantic. Changes detected in dust elemental indicators occurred on sub-weekly timescales across relatively small sampling distances along the 23W parallel of the tropical Atlantic. PSA-2 emissions, covering the western coast of the Sahara, were very strongly correlated (R² > 0.79) with Ca-44 isotope ratios in AEROSE dust samples; PSA-2.5 emissions, covering eastern Mauritania and western Mali, were very strongly correlated with K-39 ratios; PSA-3 emissions, spanning southwestern Algeria and eastern Mali, were very strongly correlated with Fe-57 and Ti-48 ratios. The abundance of Ca isotopes from PSA-2 was attributed to calcite minerals from dry lakebeds and phosphorous mining activities in Western Sahara, based on source region analysis. The correlation between K isotope ratios and PSA-2.5 was a likely indicator of illite minerals near the El Djouf Desert region, according to corroboration with mineral mapping studies. Fe and Ti ratio correlations with PSA-3 observed in this study were likely indicators of iron and titanium oxides from Sahelian sources still detectable in Atlantic Ocean observations. The rapid changes in isotope chemistry found in AEROSE dust samples provide a unique marker of Saharan source regions and their relative contributions to desert outflows in the Atlantic. These elemental indicators provide source region apportionments of Sahara Desert aerosol flux and deposition into the Atlantic Ocean, as well as a basis for model and satellite validation of Saharan dust emissions for regional climate assessments. Full article

In this work, a reliable and robust in situ non-matrix-matched calibration method is proposed for element composition determination in scheelite samples. With external calibration against the silicate glass standard reference material NIST SRM 610, the concentrations of both major elements (Ca and W) and trace elements (Si, Fe, Mo, Y, rare earth elements, etc.) in scheelite are determined using an ArF 193 nm excimer nanosecond laser ablation-inductively coupled plasma mass spectrometer (LA-ICP-MS). Here, the ablation was performed by hole drilling under a helium (He) environment using a laser spot size of 35 μm and a laser repetition of 5 Hz, and the aerosols were then transported to a quadrupole ICP-MS by a mixture of He and make-up gas argon (Ar) with a total gas flow rate of 1.6 L/min. Results showed that there was no apparent matrix effect between the NIST SRM 610 and scheelite by this proposed method. With internal standardization against W, the obtained concentrations of CaO and WO₃ were found to yield an average matrix CaO/WO₃ mass fraction ratio of 0.245 (2σ = 0.003, n = 19), which agreed well with the value of 0.243 (2σ = 0.002, n = 15) from electron probe microanalysis (EPMA). Furthermore, the accuracy of trace element analyses with this proposed non-matrix-matched calibration in situ method was evaluated by comparing the concentration results with those from bulk analysis by solution nebulizer ICP-MS (SN-ICP-MS). It was found that the quantification results from LA-ICP-MS and SN-ICP-MS were comparable, in particular showing a relative concentration bias of the total ∑REE+Y contents of less than 2%. This confirmed that scheelites can be accurately analyzed in situ by LA-ICP-MS without matrix-matched calibration standards. By using this developed in situ method, the element compositions in a series of scheelite samples from different W-associated deposits in China were successfully quantified, promising further genetic process investigation and associated geologic activities of the polymetallic resources. Full article

Currently, there is considerable interest in seeking an environmentally friendly technique that is neither thermally nor organic solvent-dependent for producing advanced polymer films for food-packaging applications. Among different approaches, plasma polymerization is a promising method that can deposit biodegradable coatings on top of polymer films. In this study, an atmospheric-pressure aerosol-assisted plasma deposition method was employed to develop a poly(ethylene glycol) (PEG)-like coating, which can act as a potential matrix for antimicrobial agents, by envisioning controlled-release food-packaging applications. Different plasma operating parameters, including the input power, monomer flow rate, and gap between the edge of the plasma head and substrate, were optimized to produce a PEG-like coating with a desirable water stability level and that can be biodegradable. The findings revealed that increased distance between the plasma head and substrate intensified gas-phase nucleation and diluted the active plasma species, which in turn led to the formation of a non-conformal rough coating. Conversely, at short plasma–substrate distances, smooth conformal coatings were obtained. Furthermore, at low input powers (<250 W), the chemical structure of the precursor was mostly preserved with a high retention of C-O functional groups due to limited monomer fragmentation. At the same time, these coatings exhibit low stability in water, which could be attributed to their low cross-linking degree. Increasing the power to 350 W resulted in the loss of the PEG-like chemical structure, which is due to the enhanced monomer fragmentation at high power. Nevertheless, owing to the enhanced cross-linking degree, these coatings were more stable in water. Finally, it could be concluded that a moderate input power (250–300 W) should be applied to obtain an acceptable tradeoff between the coating stability and PEG resemblance. Full article

Among the different applications of TiO₂, its use for the photocatalytic abatement of organic pollutants has been demonstrated particularly relevant. However, the wide band gap (3.2 eV), which requires UV irradiation for activation, and the fast electron-hole recombination rate of this n-type semiconductor limit its photocatalytic performance. A strategy to overcome these limitations relies on the realization of a nanocomposite that combines TiO₂ nanoparticles with carbon-based nanomaterials, such as rGO (reduced graphene oxide) and fullerene (C₆₀). On the other hand, the design and realization of coatings formed of such TiO₂-based nanocomposite coatings are essential to make them suitable for their technological applications, including those in the environmental field. In this work, aerosol-assisted atmospheric pressure plasma deposition of nanocomposite coatings containing both TiO₂ nanoparticles and carbon-based nanomaterials, as rGO or C₆₀, in a siloxane matrix is reported. The chemical composition and morphology of the deposited films were investigated for the different types of prepared nanocomposites by means of FT-IR, FEG-SEM, and TEM analyses. The photocatalytic activity of the nanocomposite coatings was evaluated through monitoring the photodegradation of methylene blue (MB) as a model organic pollutant. Results demonstrate that the nanocomposite coatings embedding rGO or C₆₀ show enhanced photocatalytic performance with respect to the TiO₂ counterpart. In particular, TiO₂/C₆₀ nanocomposites allow to achieve 85% MB degradation upon 180 min of UV irradiation. Full article

The requirements of nanocomposite thin films, having non-aggregated nanoparticles homogeneously dispersed in the matrix, have been realized using a new method of Direct Liquid Reactor-Injector (DLRI) of nanoparticles. In this approach, unlike conventional aerosol-assisted plasma deposition, the nanoparticles are synthesized before their injection as an aerosol into plasma. In our experiments, we have used two different plasma reactors, namely an asymmetric low-pressure RF plasma reactor and a parallel plate dielectric barrier discharge at atmospheric pressure. Our results have shown that DLRI can be easily coupled with various plasma processes as this approach allows the deposition of high-quality multifunctional nanocomposite thin films, with embedded nanoparticles of less than 10 nm in diameter. Hence, DLRI coupled with plasma processes meets the specifications for the deposition of multifunctional coatings. Full article

The spread of bacterial, fungal, and viral diseases by airborne aerosol flows poses a serious threat to human health, so the development of highly effective antibacterial, antifungal and antiviral filters to protect the respiratory system is in great demand. In this study, we developed ZnO-modified polycaprolactone nanofibers (PCL-ZnO) by treating the nanofiber surface with plasma in a gaseous mixture of Ar/CO₂/C₂H₄ followed by the deposition of ZnO nanoparticles (NPs). The structure and chemical composition of the composite fibers were characterized by SEM, TEM, EDX, FTIR, and XPS methods. We demonstrated high material stability. The mats were tested against Gram-positive and Gram-negative pathogenic bacteria and pathogenic fungi and demonstrated high antibacterial and antifungal activity. Full article

The lifetime of mirrors in outdoor conditions is crucial in the correct operation of any concentrating solar power (CSP) installation. In this work, the corrosion behavior of two types of metallized surfaces was studied. The first was made of a flexible polymer having a deposited reflective silver metallic film. The second was made of the same surface type with a dielectric SiO₂ protection coating by an atmospheric pressure plasma jet. Polycarbonate sheets were used as substrates on which metallic silver was deposited by the Dynamic Chemical Deposit technique. This electroless technique allowed producing the mirror finishing under environmental conditions by sequentially spraying; as aerosols projected towards the substrate surface, the activation and reducing-oxidizing solutions with rinsing after each one. The silver coatings were about 100 nm thick. Environmental and accelerated weathering degradation and salt and sulfide fogs were carried out. XPS analyses show that the corrosion products formed were Ag₂S, AgCl, and Ag₂O. It was observed that the tarnishing was initiated locally by the formation of Ag₂S columns as eruptions on the surface. Subsequently, the ions diffused through the protective layer and into the silver reflective layer, chemically reacting with the silver. The main atmospheric agents were H₂S, chloride particles, and HCl. High reflectance was initially obtained of about 95%. The obtained results suggest mechanisms for the degradation of exposed silver surfaces to moisturized atmospheres with corrosive compounds. Full article

To improve plasma and chemical resistance on various vacuum components used for semiconductor manufacturing equipment, various ceramic coating techniques have been applied. Among these methods for ceramic coating, the well-known atmospheric plasma spray (APS) is advantageous for providing thick film (100 µm or more) deposition. However, there are problems associated with the phase transition of the coating film and poor film quality due to formation of voids. To solve these problems, the aerosol deposition (AD) method has been developed. This method provides nice ceramic film quality. However, the coating rate is quite slow and has difficulty producing thick films (>30 µm). To overcome these limitations, microwave plasma-assisted aerosol deposition (μ-PAD) is applied at low vacuum conditions without the AD nozzle. This method uses a microwave plasma source during the AD process. After enduring a long-term durability test, as a trial run, μ-PAD has been applied on the actual process site. With the Al₂O₃ powder, μ-PAD shows a coating rate that is 12 times higher than the AD method. In addition, the formation of a thicker film (96 µm) deposition has been demonstrated. On the other hand, the coating film hardness, porosity, adhesion, and withstand voltage characteristics were confirmed to be less than the AD method. Full article

We report on the aerosol-assisted atmospheric-pressure plasma deposition onto a stainless-steel woven mesh of a thin nanocomposite coating based on TiO₂ nanoparticles hosted in a hybrid organic–inorganic matrix, starting from nanoparticles dispersed in a mixture of hexamethyldisiloxane and isopropyl alcohol. The stainless-steel mesh was selected as an effective support for the possible future technological application of the coating for photocatalytically assisted water depollution. The prepared coatings were thoroughly investigated from the chemical and morphological points of view and were demonstrated to be photocatalytically active in the degradation of an organic molecule, used as a pollutant model, in water upon UV light irradiation. In order to optimize the photocatalytic performance, different approaches were investigated for the coating’s realization, namely (i) the control of the deposition time and (ii) the application of a postdeposition O₂ plasma treatment on the pristine coatings. Both strategies were found to be able to increase the photocatalytic activity, and, remarkably, their combination resulted in a further enhancement of the photoactivity. Indeed, the proposed combined approach allowed a three-fold increase in the kinetic constant of the degradation reaction of the model dye methylene blue with respect to the pristine coating. Interestingly, the chemical and morphological characterizations of all the prepared coatings were able to account for the enhancement of the photocatalytic performance. Indeed, the presence of the TiO₂ nanoparticles on the outmost surface of the film confirmed the accessibility of the photocatalytic sites in the nanocomposite and reasonably explained the enhanced photocatalytic performance. In addition, the sustained photoactivity (>5 cycles of use) of the nanocomposites was demonstrated. Full article

Hydroxyapatite is a widely used material used for the bioactivation of an implant’s surface. A promising hydroxyapatite coating approach is the kinetic deposition of powder particles. The possibility of solid-state deposition improvement through the merging of Aerosol Deposition and Low Pressure Cold Spraying techniques is a promising prospect for improving the deposition efficiency and the quality of coatings. The objective of the paper is to study the possibilities of hydroxyapatite coating structure modification through changes in the coating process and post-heat treatment. The novel Aerosol Cold Spraying system joining Low Pressure Cold Spraying and Aerosol Deposition was used for the deposition of coatings. The coating’s post-processing was conducted using two techniques: Spark Plasma Sintering and Pressureless Sintering. The coating’s structure was examined using scanning, transmission, and light microscopy, and X-ray diffraction. Substrate–coating bond strength was assessed using a tensile test. Homogenous buildup using Aerosol Cold Spraying of hydroxyapatite was achieved. Various pores and microcracks were visible in the sprayed coatings. The deposition process and the thermal post-processing did not lead to significant degradation of the hydroxyapatite phase. As a result of the Spark Plasma Sintering and Pressureless Sintering at 800 °C, an increase in tensile adhesion bond strength and crystal size was obtained. Full article

TiO₂ is a promising photocatalyst, but its large bandgap restricts its light absorption to the ultraviolet region. The addition of noble metals can reduce the bandgap and electron-hole recombination; therefore, we prepared TiO₂-Ag nanoparticle composite films by plasma-enhanced chemical vapor deposition (PECVD) using a mixture of aerosolized AgNO₃, which was used as a Ag nanoparticle precursor, and titanium tetraisopropoxide, which acted as the TiO₂ precursor. Notably, the use of PECVD enabled a low process temperature and eliminated the need for pre-preparing the Ag nanoparticles, thereby increasing the process efficiency. The structures and morphologies of the deposited films were characterized by ultraviolet (UV)—visible spectroscopy, X-ray diffraction, X-ray photoelectron spectroscopy, scanning electron microscopy, transmission electron microscopy and energy-dispersive X-ray spectroscopy, and the effects of the AgNO₃ concentration on the photocatalytic activity of the deposited films were determined by assessing the degradation of methylene blue under UV light irradiation. The Ag ions were successfully reduced to metallic nanoparticles and were embedded in the TiO₂ film. The best photocatalytic activity was achieved for a 1 wt% Ag-loaded TiO₂ composite film, which was 1.75 times that of pristine TiO₂. Full article