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Large emissions of nitrogen dioxide (NO2) pose a significant threat to human health, Monitoring its content and implementing timely measures are crucial. Utilizing oxide semiconductors, such as tin dioxide (SnO2), has proven to be an effective way to detect and analyze NO2. The design and preparation of sensing materials with high sensitivity and excellent selectivity is the key to improve the detection efficiency. SnO2 nanopowders with small and uniform particle size, large specific surface area, adjustable defect content, and no impurities were prepared by a new plasma spraying method. The SnO2 nanopowders exhibit outstanding performance in detecting NO2 at a low temperature of 100 °C, the response to 5 ppm of NO2 reaches 48, and the material demonstrates rapid response and recovery times, coupled with excellent selectivity. The exceptional gas-sensitive properties can be attributed to the superior morphology and structure of SnO2. It provides more reaction sites for gas sensitive reactions, fast electron transport, a large number of charge carriers, and improved adsorption of the material to the target gas. This study provides valuable insights into nanomaterial preparation and the enhancement of gas-sensitive properties for SnO2.

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As protective coatings for the thermal parts of aero-engines, AlCoCrFeNi coatings have good application prospects. In this study, atmospheric plasma spraying (APS) was used to prepare AlCoCrFeNi high-entropy coatings (HECs), which were oxidized from 650 °C to 1000 °C. The mechanism of the oxide layer formation and the internal phase transition were systematically investigated. The results show that a mixed oxide scale with a laminated structure was formed at the initial stage of oxidation. The redistribution of elements and phase transition occurred in the HECs' matrix; the BCC/B2 structure transformed to Al-Ni ordered B2 phase and Fe-Cr disordered A2 phase.

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Photocatalytic coatings can degrade volatile organic compounds into non-toxic products, which has drawn the attention of scholars around the world. However, the pollution of dust on the coating adversely affects the photocatalytic efficiency and service life of the coating. Here, a series of TiO2-polyfluoroalkoxy (PFA) coatings with different contents of PFA were fabricated by suspension plasma spraying technology. The results demonstrate that the hybrid coatings contain a large number of circular and ellipsoidal nanoparticles and a porous micron-nano structure due to the inclusion of PFA. According to the optimized thermal spraying process parameters, TiO2 nanoparticles were partially melted to retain most of the anatase phases, whereas PFA did not undergo significant carbonization. As compared to the TiO2 coating, the static contact angle of the composite coating doped with 25 wt.% PFA increased from 28.2° to 134.1°. In addition, PFA strongly adsorbs methylene blue, resulting in a greater involvement of methylene blue molecules in the catalyst, where the catalytic rate of hybrid coatings is up to 95%. The presented nanocomposite coatings possess excellent photocatalytic and self-cleaning properties and are expected to find wider practical applications in the field of photocatalysis.

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In this study, silicon coating was deposited on melt-infiltrated SiC composites using atmospheric plasma spraying and then annealed at 1100 and 1250 °C for 1-10 h to investigate the effect of annealing on the layer. The microstructure and mechanical properties were evaluated using scanning electron microscopy, X-ray diffractometry, transmission electron microscopy, nano-indentation, and bond strength tests. A silicon layer with a homogeneous polycrystalline cubic structure was obtained without phase transition after annealing. After annealing, three features were observed at the interface, namely ß-SiC/nano-oxide film/Si, Si-rich SiC/Si, and residual Si/nano-oxide film/Si. The nano-oxide film thickness was ≤100 nm and was well combined with SiC and silicon. Additionally, a good bond was formed between the silicon-rich SiC and silicon layer, resulting in a significant bond strength improvement from 11 to >30 MPa.

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High-performance microwave absorption coatings are critically required in the stealth defense system of military platforms. Regrettably, just optimizing the property but neglecting the application feasibility seriously inhibits its practical application in the field of microwave absorption. To face this challenge, the Ti4O7/carbon nanotubes (CNTs)/Al2O3 coatings were successfully fabricated by a plasma-sprayed method. For the different oxygen vacancy-induced Ti4O7 coatings, the enhanced ε' and ε'' values in the frequency of X-band is due to the synergistic manipulation of conductive path, defects and interfacial polarization. The optimal reflection loss of Ti4O7/CNTs/Al2O3 sample (0 wt% CNTs) is -55.7 dB (8.9 GHz of 2.41 mm), while the electromagnetic interference shielding effectiveness of Ti4O7/CNTs/Al2O3 sample (5 wt% CNTs) increases to 20.5 dB as the enhanced electrical conductivity. In special, the flexural strength of Ti4O7/CNTs/Al2O3 coatings first increases from 48.59 MPa (0 wt% CNTs) to 67.13 MPa (2.5 wt% CNTs) and then decreases to 38.31 MPa (5 wt% CNTs), demonstrating that an appropriate amount of CNTs evenly dispersed in the Ti4O7/Al2O3 ceramic matrix can effectively play the role of CNTs as the strengthening phase of the coatings. This research will provide a strategy by tailoring synergistic effect of dielectric loss and conduction loss for oxygen vacancy-mediated Ti4O7 material to broaden the application of absorbing or shielding ceramic coatings.

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Due to its excellent biocompatibility and corrosion resistance, tantalum demonstrates versatility as an implant material. However, limited studies investigated the role of tantalum coated titanium-based dental implants. This study aimed to investigate the potential application of micro-nano porous structured tantalum coating on the surface of titanium dental implant. In the present study, micro-nano porous structured tantalum coating was prepared by vacuum plasma spraying (VPS) under selected optimum parameters, various characteristics of tantalum coating (Ta/Ti), including the morphology, potential, constituent, and hydrophilia, were investigated in comparison with its respective control groups, sandblasted titanium (Ti) and titanium coating (Ti/Ti). The adhesion, proliferation, and osteogenic differentiation ability of rat bone marrow mesenchymal cells (BMSCs) on different materials were assessed in vitro. Then the osseointegration capacity of Ti, Ti/Ti, Ta/Ti, and Straumann implants in canine mandible was evaluated with micro-CT, histological sections, and energy dispersive X-ray spectroscopy. These results demonstrated that micro-nanostructured, uneven, and granular tantalum coating was successfully prepared on titanium substrate by VPS with pore size ranging from 50 nm to 5 µm and thickness ranging from 80 to 100 µm. Tantalum coating revealed the highest surface potential, best hydrophilia, and most protein adsorption among Ta/Ti, Ti/Ti, and Ti. Furthermore, Ta/Ti surfaces significantly promoted the adhesion, proliferation, and osteogenic differentiation of BMSCs. In vivo, Ta/Ti implants displayed positive osseointegration capability associated with increased bone mineral density and formation of new bone around implants without tantalum particles released. Together, these findings indicate that tantalum-coated titanium dental implants may serve as a new type of dental implant.

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The microstructural characteristics and phase composition of solution precursor plasma-sprayed (SPPS) titania-based coatings using a catalyst-free precursor are reported in this work. An ethanol-based solution containing titanium isopropoxide was used to deposit TiO2 coatings. The thermal behavior of the solution precursor changed as its phase transformation temperature increased when the molar concentration was increased from 0.3 M to 0.6 M. Scanning electron micrographs showed that the surface of the coatings was composed of nano- and submicron-sized spherical particles (<1 µm) with sintered and melted particles. The cross-sections showed a porous structure using lower concentrations and dense coating formation with micropores using higher concentrations, with thicknesses of about 5 µm-8 µm. Moreover, the coatings when the number of spray passes was increased were 16 µm-20 µm thick, giving an average layer thickness of 0.6 µm deposited per spray pass in all cases. Phase analysis revealed the presence of both the anatase and rutile phases of TiO2 in coatings sprayed with various concentrations at various stand-off distances. More detailed discussion is presented with respect to the effects of the solution concentration, stand-off distance, and number of spray passes on the coating's phase composition and microstructure.

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The present paper presents a study of the behaviour of Fe3Al intermetallic powders particles based on 86Fe-14Al, 86Fe-14(Fe5Mg), and 60.8Fe-39.2(Ti37.5Al) compositions obtained by mechanochemical synthesis at successive stages of the plasma spraying process: during transfer in the volume of the gas stream and deformation at the moment of impact on the substrate. The effect of the change in current on the size of powder particles during their transfer through the high-temperature stream and the degree of particle deformation upon impact with the substrate was determined. It was found that during transfer through the plasma jet, there was an increase in the average size of sputtering products by two-three times compared to the initial effects of mechanochemical synthesis due to the coagulation of some particles. In this case, an increase in current from 400 to 500 A led to a growth in average particle size by 14-47% due to the partial evaporation of fine particles with an increase in their heating degree. An increase in current also led to a 5-10% growth in particle deformation degree upon impact on the substrate due to the rising temperature and velocity of the plasma jet. Based on the research, the parameters of plasma spraying of mechanically synthesized Fe3Al intermetallic-based powders were determined, at which dense coatings with a thin-lamellar structure were formed.

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Carbon fiber (CF) composites performance enhancement is a research hotspot at present. In this work, first, a sandwich structure composite, CF@(carbon nanotube/Fe3O4)/epoxy (CF@(CNT/Fe3O4)/EP), is prepared by the free arc dispersion-CFs surface spraying-rolling process method, herein, CFs in the middle layer and (CNT/Fe3O4)/EP as top and substrate layer. Then, CF@(CNT/Fe3O4)/EP (on both sides) and CFs (in the middle) are overlapped by structure design, forming a multilayer CF@(CNT/Fe3O4)/EP-CFs composite with a CFs core sheath. A small amount of CNT/Fe3O4 is consumed, (CNT/Fe3O4)/EP and CFs core sheath realize thermal and electrical anisotropy and directional enhancement, and multilayer sandwich structure makes the electromagnetic interference (EMI) shielding performance better strengthened by multiple absorption-reflection/penetration-reabsorption. From CF-0 to CF-8, CNT/Fe3O4 content only increases by 0.045 wt%, axial thermal conductivity (λ‖) increases from 0.59 W/(m·K) to 1.1 W/(m·K), growth rate is 86%, radial thermal conductivity (λ⟂) only increases by 0.05 W/(m·K), the maximum λ‖/λ⟂ is 2.9, axial electrical conductivity (σ‖) increases from 6.2 S/cm to 7.7 S/cm, growth rate is 24%, radial electrical conductivity (σ⟂) only increases by 0.7 × 10-4 S/cm, the total EMI shielding effectiveness (EMI SET) increases by 196%, from 10.3 dB to 30.5 dB. This provides a new idea for enhancing CFs composite properties.

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Lithium-ion solid-state batteries with spinel Li4Ti5O12 (LTO) electrodes have significant advantages, such as stability, long life, and good multiplication performance. In this work, the LTO electrode was obtained by the atmospheric plasma spraying method, and a composite solid electrolyte was prepared by in situ ultraviolet (UV) curing on the LTO electrode. The composite solid electrolyte was designed using a soft-hard combination strategy, and the electrolyte was prepared into a composite of a poly(vinylidene fluoride-co-hexafluoropropylene) (PVDF-HFP) flexible structure and high-conductivity Li1.3Al0.3Ti1.7(PO4)3 (LATP) hard particles. The composite electrolyte exhibited a good ionic conductivity up to 0.35 mS cm-1 at 30 °C and an electrochemical window above 4.0 V. In situ and ex situ electrolytes were assembled into LTO//electrolyte//Li solid-state batteries to investigate their impact on the electrochemical performance of the batteries. As a result, the assembled Li4Ti5O12//in situ electrolytes//Li batteries exhibited excellent rate of performance, and their capacity retention rate was 90% at 0.2 mA/cm2 after 300 cycles. This work provides a new method for the fabrication of novel advanced solid-state electrolytes and electrodes for applications in solid-state batteries.

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An usual material, EN-GJL-250 cast iron, used for automotive braking systems, was covered with a ceramic material (105NS-1 aluminium oxide) using an industrial deposition system (Sulzer Metco). The main reason was to improve the corrosion and wear (friction) resistance properties of the cast-iron. Samples were prepared by mechanical grinding and sandblasting before the deposition. We applied two and four passes (around 12-15 µm by layer) each at 90° obtaining ceramic coatings of 30 respectively 60 µm. The surface of the samples (with ceramic coatings) was investigated using scanning electron microscopy (SEM), dispersive energy spectroscopy (EDS) and X-ray diffraction (XRD). Scratch and micro-hardness tests were performed using CETR-UMT-2 micro-tribometer equipment. The better corrosion resistance of the base material was obtained by applying the ceramic coating. The results present a better corrosion resistance and a higher coefficient of friction of the coated samples.

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In this work, the microstructure and mechanical properties of atmospheric plasma-sprayed coatings of Al0.5CoCrFeNi2Ti0.5, prepared using gas-atomized powders at varying spray powers, are studied in as-sprayed and heat-treated conditions. Gas-atomized powders had spherical shapes and uniform element distributions, with major FCC phases and metastable BCC phases. The metastable BCC phase transformed to ordered and disordered BCC phases when sufficient energy was applied during the plasma-spraying process. During the heat treatment process for 2 hrs, disordered BCCs transformed into ordered BCCs, while the intensity of the FCC peaks increased. Spraying power plays a significant role in the microstructure and mechanical properties of plasma sprayed because at a high power, coatings exhibit better mechanical properties due to their dense microstructures resulting in less defects. As the plasma current was increased from 500 A to 700 A, the coatings' hardness increased by approximately 21%, which is directly proportional to the decreased wear rate of the coatings at high spraying powers. As the coatings experienced heat treatments, the coatings sprayed with a higher spraying power showed higher hardness and wear resistances. Precipitation strengthening played a significant role in the hardness and wear resistances of the coatings due to the addition of the titanium element.

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Titanium (Ti) alloys show excellent fatigue and corrosion resistance, high strength to weight ratio, and no toxicity; however, poor osseointegration ability of Ti may lead to implant loosening in vivo. Plasma spraying of hydroxyapatite [HA, Ca10 (PO4)6 (OH)2] coating on Ti surfaces is commercially used to enhance osseointegration and the long-term stability of these implants. The biological properties of HA can be improved with the addition of both cationic and anionic dopants, such as zinc ions (Zn2+) and fluoride (F-). However, the hygroscopic nature of fluoride restricts its utilization in the radiofrequency (RF) plasma spray process. In addition, the amount of doping needs to be optimized to ensure cytocompatibility. We have fabricated zinc and fluoride doped HA-coated Ti6Al4V (Ti64) to mitigate these challenges using compositional and parametric optimizations. The RF induction plasma spraying method is utilized to prepare the coatings. Multiple parametric optimizations with amplitude and frequency during the processing result in coating thicknesses between 80 and 145 µm. No adverse effects on the adhesion properties of the coating are noticed because of doping. The antibacterial efficacy of each composition is tested against S. aureus for 24, 48, and 72 h, and showed that the addition of zinc oxide and calcium fluoride to HA leads to nearly 70 % higher antibacterial efficacy than pure HA-coated samples. The addition of osteogenic Zn2+and F- leads to 1.5 times higher osteoblast viability for the doped samples than pure HA-coated samples after 7-days of cell culture. Zn2+ and F- doped HA-coated Ti64 with simultaneous improvements in anti-bacterial efficacy and in vitro biocompatibility can find application in load-bearing implants, particularly in revision surgeries and immune-compromised patients.

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The TriplexPro™-210 plasma spray torch (Oerlikon Metco) is a three-cathode plasma generator. It became a kind of workhorse for the wide range of tasks handled at the Jülich Thermal Spray Center (JTSC). Compared to conventional single-cathode torches, the cascaded design of the nozzle suggests low fluctuations of the arc and thus high stability. However, after a certain time, degradation sets in even with such a torch, impairing the reliability of the process. It is therefore important to detect indications of performance loss in time and not only during the inspection of the deposited layer. In this study, standard samples of YSZ thermal barrier coatings were sprayed regularly over a period of two years. Operational data and feedstock characteristics were collected and correlated with the area-specific mass deposition. It turned out that the measured substrate surface temperature showed a distinct correlation. Searching for the reasons for the temperature variations, several process parameters could be ruled out as they are monitored by calibrated sensors, controlled, and their time course is recorded by the control unit. Moreover, there are other parameters, which can have a considerable impact such as the robot alignment or the substrate cooling conditions. However, the purposeful experimental variation of such variables resulted in a variability of the mass deposition being considerably smaller than observed over the two years. Thus, it can be concluded that torch degradation had a pronounced effect, too. The substrate surface temperature can be used as indicator for the torch status and the reliability of the spray process.

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The aim of this work was to develop a new coating material based on Ni20Cr alloy modified with up to 50%wt. rhenium. The modification was carried out by the mechanical mixing of the base powder and ammonium perrhenate with the subsequent thermoreduction in an H2 atmosphere. The obtained powder consists of a nickel-chromium core surrounded by a rhenium shell. The characterization of the powders-including their microstructure, phase and chemical composition, density, flowability, particle size distribution, and specific surface area-was performed. The influence of plasma current intensity and hydrogen gas flow on in-flight particle temperature and velocity were investigated. The results indicate that there is interdiffusion between the base Ni20Cr and the rhenium shell, resulting in intermediary solid solution(s). The modified powders have a higher specific surface area and a lower flowability, but this does not prevent them from being used as feedstock in plasma spraying. In-flight measurements reveal that increasing the content of rhenium allows for the higher temperature of particles, though it also reduces their speed.

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A higher density of large-angle grain boundaries in palladium membranes promotes hydrogen diffusion whereas small-angle grain boundaries suppress it. In this paper, the microstructure formation in 10 µm thick palladium membranes is tuned to achieve a submicronic grain size above 100 nm with a high density of large-angle grain boundaries. Moreover, changes in the grain boundaries' structure is investigated after exposure to hydrogen at 300 and 500 °C. To attain large-angle grain boundaries in Pd, the coating was performed on yttria-stabilized zirconia/porous Crofer 22 APU substrates (intended for use later in an ultracompact membrane reactor). Two techniques of plasma sprayings were used: suspension plasma spraying using liquid nano-sized powder suspension and vacuum plasma spraying using microsized powder as feedstock. By controlling the process parameters in these two techniques, membranes with a comparable density of large-angle grain boundaries could be developed despite the differences in the fabrication methods and feedstocks. Analyses showed that a randomly oriented submicronic structure could be attained with a very similar grain sizes between 100 and 500 nm which could enhance hydrogen permeation. Exposure to hydrogen for 72 h at high temperatures revealed that the samples maintained their large-angle grain boundaries despite the increase in average grain size to around 536 and 720 nm for vacuum plasma spraying and suspension plasma spraying, respectively.

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Applying antibacterial coatings to dental implant materials seems reasonable but can have negative influences on desired cell adhesion and healing. In this study, zirconia abutment specimens interacting with gingival tissue were used. The aim was to compare the influence of machined or coated zirconia surfaces on the adhesion and proliferation of human gingival fibroblasts (HGF-1). Surface modifications were performed using atmospheric plasma coating with hydroxyapatite, zinc, and copper. Zirconia specimens were divided into four groups: hydroxyapatite, hydroxyapatite with zinc oxide (ZnO), hydroxyapatite with copper (Cu), and an untreated machined surface. After the characterization of the surface conditions, the morphology of adhered HGF-1 was determined by fluorescence staining and subjected to statistical evaluation. The visual analysis of cell morphology by SEM showed flat, polygonal, and largely adherent fibroblast cells in the untreated group, while round to partially flat cells were recorded in the groups with hydroxyapatite, hydroxyapatite + ZnO, and hydroxyapatite + Cu. The cell membranes in the hydroxyapatite + ZnO and hydroxyapatite + Cu groups appeared porous. The results show that HGF-1 adhere and proliferate well on machined zirconia, while plasma coating with hydroxyapatite or hydroxyapatite mixtures does not lead to increased adhesion or proliferation.

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In this study, Ni-Cu-W graded coatings are produced by atmospheric plasma spraying and subsequently remelted by laser. The surface morphology, hardness, compositional fluctuations and corrosion resistance of the Ni-Cu-W coating are investigated. The coatings after laser remelting are densified and become more homogenous with an excellent corrosion resistance and high hardness, which can be used to explore the new materials.

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In situ synthesis feasibility of ZrB2-SiC-ZrC composite coatings on ZrC ceramics by reactive plasma spraying (RPS) was investigated. To help to understand the phase evolution during plasma spraying process, reaction behavior in the ZrH2-Si-B4C system was explored carefully by differential scanning calorimetry. The results indicated that the phase transformation sequence in the ZrH2-Si-B4C system could be described as ZrH1.66, Zr3O, ZrC, ZrB2, Zr2Si, ZrSi, and SiC. The prior formation of ZrC was due to high diffusion rate of C atoms from B4C. ZrB2 was produced above 1100 °C. As the temperature increased, SiC were finally formed by the reaction of ZrC with ZrSi and B4C. The RPS composite coatings mainly consisted of ZrB2, SiC, and ZrC phases, except for a small fraction of ZrO2 phase. The microstructural characterization exhibited more dense melted splats, which appears to increase gradually with the increase in spraying currents and distances. The coatings had typical lamellar structure and adhered to the substrate well. The microhardness values were higher than 1000 HV1, but there were few variations with varying spraying currents and distances.

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High entropy alloys (HEAs) are multi-elemental alloy systems that exhibit a combination of exceptional mechanical and physical properties, and nowadays are validating their potential in the form of thermal sprayed coatings. In the present study, a novel synthesis method is presented to form high entropy alloy coatings. For this purpose, thermal sprayed coatings were deposited on Stainless Steel 316L substrates using atmospheric plasma spraying technique with subsequent annealing, at 1000 °C for 4 h, to assist alloy formation by thermal diffusion. The coatings in as-coated samples as well as in annealed forms were extensively studied by SEM for microstructure and cross-sectional analysis. Phase identification was performed by X-ray diffraction studies. The annealed coatings revealed a mixed BCC and FCC based HEA structure. Potentiodynamic corrosion behavior of SS316L sprayed as well as annealed coatings were also carried out in 3.5% NaCl solution and it was found that the HEA-based annealed coatings displayed the best corrosion resistance 0.83 (mpy), as compared to coated/non-annealed and SS 316 L that showed corrosion resistance of 7.60 (mpy) and 3.04 (mpy), respectively.