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83 pages, 18468 KiB

Open AccessArticle

Thermionic Vacuum Discharges for Thin Film Depositions

by Ion Mustata, Cristian Lungu, Ionut Jepu and Corneliu Porosnicu

Coatings 2023, 13(9), 1500; https://doi.org/10.3390/coatings13091500 - 25 Aug 2023

Cited by 1 | Viewed by 844

The thermionic vacuum discharge method is very effective in that the films obtained using this technology are characterised by a very high degree of adhesion, density and purity because the deposition technique is carried out in high, very high or, if possible, in [...] Read more.

The thermionic vacuum discharge method is very effective in that the films obtained using this technology are characterised by a very high degree of adhesion, density and purity because the deposition technique is carried out in high, very high or, if possible, in ultra-very high vacuum conditions with no gas present. When the substrate is placed in vacuum, no heat transfer particles are present, the substrate being heated only by the ion incident on the surface. This advantage recommends the TVD method for deposits on plastics or other thermally sensitive materials. Additionally, this slow heat transfer reduces energy loss, making the deposition method industrially competitive. The paper aims to present theoretical aspects of this type of discharge, compared to typical or more popular plasmas but also to present the achievements of this method and its utility in the thin films production, layers that have specific imposed properties. The practical depositions and applications presented are in the nuclear fusion-related material science and also for obtaining materials for granular structures, used as magneto-resistive coatings. Full article

(This article belongs to the Special Issue State-of-the-Art on Coatings Research in Romania 2021-2022)

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25 pages, 12033 KiB

Open AccessArticle

Optimization of the Mung Bean Seed Coating with Alginate in a Bottom-Sprayed Wurster Fluidized Bed Coater

by Bogdan Trica, Naomi Tritean, Diana Constantinescu-Aruxandei and Florin Oancea

Coatings 2023, 13(3), 562; https://doi.org/10.3390/coatings13030562 - 06 Mar 2023

Cited by 1 | Viewed by 2231

Abstract

Seed coating is used to improve seed handling or target the delivery of different active ingredients: (micro)nutrients and biofortifying minerals, plant biostimulants, and plant protection compounds. One type of coating is based on using film-forming biopolymers. The coating could be applied using various [...] Read more.

Seed coating is used to improve seed handling or target the delivery of different active ingredients: (micro)nutrients and biofortifying minerals, plant biostimulants, and plant protection compounds. One type of coating is based on using film-forming biopolymers. The coating could be applied using various equipment, including the Wurster fluidized-bed coater. Deterministic models have been proposed to predict the coating process performance in the Wurster fluidized-bed coater. However, such deterministic models do not closely match real behavior. This paper proposes a statistical model approach to optimize the mung bean seed coating with a mixture of alginate/glycerol in a Wurster fluidized bed coating process. The process was optimized for a specific case through a factorial experimental design for the following parameters: the liquid flow rate, the mass of seeds, the backpressure period, and the nozzle pressure. The statistical analysis was done using Design-Expert 11^®. The formed film was analyzed by scanning electron microscopy. Finally, the germination percentage (GP), germination energy (GE), germination rate (GR), mean germination time (MGT), and vigor index (VI) were determined for the coated mung bean seeds. An algorithm is proposed to identify the optimal coating conditions in a bottom-spray Wurster fluidized-bed coater for any coating solution or seed pair. Full article

(This article belongs to the Special Issue State-of-the-Art on Coatings Research in Romania 2021-2022)

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20 pages, 18525 KiB

Open AccessFeature PaperArticle

Archaeometric Investigations of the Chalcolithic Pottery from Topolița—Neamț County, Romania

by Rodica-Mariana Ion, Vasile Diaconu, Gabriel Vasilievici, Lorena Iancu, Ramona Marina Grigorescu, Luiza-Andreea Mîrț, Elvira Alexandrescu, Anca Irina Gheboianu and Sofia Slamnoiu-Teodorescu

Coatings 2023, 13(3), 488; https://doi.org/10.3390/coatings13030488 - 22 Feb 2023

Cited by 1 | Viewed by 1305

Abstract

The current work deals with specific investigations on the ceramic fragment samples from the archaeological site of Topolița (Eastern Romania), which is essentially unexplored to date. X-ray diffraction (XRD) has shown that the ceramics contain quartz, berlinite, mica (muscovite), calcite, and opaque minerals, [...] Read more.

The current work deals with specific investigations on the ceramic fragment samples from the archaeological site of Topolița (Eastern Romania), which is essentially unexplored to date. X-ray diffraction (XRD) has shown that the ceramics contain quartz, berlinite, mica (muscovite), calcite, and opaque minerals, such as hematite. All evidence indicates the use of raw materials with a low limestone content (poor Ca clays) for the manufacture of these ceramics (Ca < 3.6%). The wavelength dispersive X-ray fluorescence (WDXRF) measurements indicated the presence of Al, Si, Fe, Ca, Zn, P, and K. All these data are well correlated with energy dispersive spectroscopy (EDS), which is used as an additional technique of scanning electron microscopy (SEM). Through thermogravimetry and porosimetry, some information have been obtained, with the results being correlated with the chromatic parameters that characterize the samples after burning: Various shades of color (red color with sparkles and partially or totally black interior), differently colored engobes, white pigment encrusted with white color from calcite, gypsum, clays, and quartz, as well as carbon deposits in the pores of the pottery, all specific to the Chalcolithic ceramics from this region. The recorded FTIR spectra of these samples led to the identification of calcite, quartz, gypsum, and aluminum phosphate, present as berlinite in all the pottery specific to this area. In addition, the presence/absence and the amount of specific chemical elements in the white pigments (e.g., calcium, aluminum, phosphorus, silicon, sulfur) could be used as indicative for the identified mineral compounds (XRD and FTIR). Calcite and silica-rich sediments as the primary decoration pigments, have been identified in this case. Full article

(This article belongs to the Special Issue State-of-the-Art on Coatings Research in Romania 2021-2022)

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18 pages, 2748 KiB

Open AccessArticle

Deuterium Retention in Mixed Layers with Application in Fusion Technology

by Paul Dinca, Cornel Staicu, Corneliu Porosnicu, Bogdan Butoi, Oana Gloria Pompilian, Ana Maria Banici, Flaviu Baiasu, Ion Burducea and Cristian P. Lungu

Coatings 2022, 12(7), 951; https://doi.org/10.3390/coatings12070951 - 05 Jul 2022

Cited by 1 | Viewed by 1589

Abstract

Formation of Be-W mixed layers in thermonuclear fusion reactors can potentially alter the retention of hydrogen isotopes and affect the retention and release properties of these isotopes. This paper reports on the retention and release characteristics of D from reference Be, W layers [...] Read more.

Formation of Be-W mixed layers in thermonuclear fusion reactors can potentially alter the retention of hydrogen isotopes and affect the retention and release properties of these isotopes. This paper reports on the retention and release characteristics of D from reference Be, W layers as well as three Be-W mixed layers with well-defined atomic concentrations (2:1, 1:1, 1:2). The layers resulted from the sputtering of Be and W materials in Ar:D (1:1) mixture at 2 Pa using DC magnetron sputtering. The mixed layers’ deposition parameters were varied to adjust accordingly the deposition rate for each material in order to obtain the desired concentrations. Scanning electron microscope images showed that morphology is independent of composition for samples deposited on silicon substrates. In contrast, layers deposited on tungsten revealed a textured surface and morphological changes with W concentration variation. X-ray diffraction patterns of mixed layers evidenced the presence of a polycrystalline tungsten phase. Additionally, the degree of crystallinity is highly influenced by the plasma parameters and enhanced amorphization is evidenced by a decrease of crystalline size by a factor of 10 for mixed layers compared to the W reference layer. The release behavior of D from the layers is affected by the trapping contribution of both Be and W. Compared with implanted layers, presented in literature studies, the co-deposited layers show a high D occupancy of low energy trapping states, the majority of the D retained in the samples being released at temperatures below 623 K. High energy trapping becomes more pronounced for layers with a high Be concentration. The oxygen contamination observed for Be layers points to a mitigation of D retention in low energy trapping states and shifts the desorption chart towards a higher temperature due to enhanced retention in BeO associated traps. The D retention presents a linear decrease of W concentration in the sample. Full article

(This article belongs to the Special Issue State-of-the-Art on Coatings Research in Romania 2021-2022)

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24 pages, 11068 KiB

Open AccessArticle

SiC- and Ag-SiC-Doped Hydroxyapatite Coatings Grown Using Magnetron Sputtering on Ti Alloy for Biomedical Application

by Iulian Pana, Viorel Braic, Alina Vladescu, Raluca Ion, Anca Constantina Parau, Nicolae Catalin Zoita, Mihaela Dinu, Adrian Emil Kiss, Anisoara Cimpean and Mariana Braic

Coatings 2022, 12(2), 195; https://doi.org/10.3390/coatings12020195 - 02 Feb 2022

Cited by 5 | Viewed by 1717

Abstract

SiC- and Ag-SiC-doped hydroxyapatite (HA) coatings were deposited via magnetron sputtering aiming at increased corrosion protection of Ti-10Nb-10Zr-5Ta alloy in simulated body fluid environment and superior mechanical properties compared to plain hydroxyapatite. The coatings had a total thickness of about 350 nm. The [...] Read more.

SiC- and Ag-SiC-doped hydroxyapatite (HA) coatings were deposited via magnetron sputtering aiming at increased corrosion protection of Ti-10Nb-10Zr-5Ta alloy in simulated body fluid environment and superior mechanical properties compared to plain hydroxyapatite. The coatings had a total thickness of about 350 nm. The X ray diffraction patterns indicate that HA coatings are polycrystalline with a hexagonal structure and the addition of SiC determined the coating amorphization. All coatings presented a lower roughness compared to the Ti alloy and were hydrophilic. Ag-SiC-HA coating presented the best corrosion resistance and tribological parameters. All coatings were biocompatible, as ascertained via indirect cytocompatibility studies conducted on Vero cells. Full article

(This article belongs to the Special Issue State-of-the-Art on Coatings Research in Romania 2021-2022)

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15 pages, 4098 KiB

Open AccessArticle

Effect of Doping Element and Electrolyte’s pH on the Properties of Hydroxyapatite Coatings Obtained by Pulsed Galvanostatic Technique

by Elena Ungureanu, Diana Maria Vranceanu, Alina Vladescu, Anca Constantina Parau, Mihai Tarcolea and Cosmin Mihai Cotrut

Coatings 2021, 11(12), 1522; https://doi.org/10.3390/coatings11121522 - 10 Dec 2021

Cited by 9 | Viewed by 2342

Abstract

Hydroxyapatite (HAp) is the most widely used calcium phosphate as a coating on metal implants due to its biocompatibility and bioactivity. The aim of this research is to evaluate the effect of the pH’s electrolyte and doping element on the morphology, roughness, chemical, [...] Read more.

Hydroxyapatite (HAp) is the most widely used calcium phosphate as a coating on metal implants due to its biocompatibility and bioactivity. The aim of this research is to evaluate the effect of the pH’s electrolyte and doping element on the morphology, roughness, chemical, and phasic composition of hydroxyapatite-based coatings obtained by pulsed galvanostatic electrochemical deposition. As doping elements, both Sr and Ag were selected due to their good osseoinductive character and antibacterial effect, respectively. The electrolytes were prepared at pH 4 and 5, in which specific concentrations of Sr, Ag, and Sr + Ag were added. In terms of morphology, all coatings consist in ribbon-like crystals, which at pH 5 appear to be a little larger. Addition of Sr did not affect the morphology of HAp, while Ag addition has led to the formation of flower-like crystals agglomeration. When both doping elements were added, the flowers like agglomerations caused by the Ag have diminished, indicating the competition between Sr and Ag. X-Ray Diffraction analysis has highlighted that Sr and/or Ag have successfully substituted the Ca in the HAp structure. Moreover, at higher pH, the crystallinity of all HAp coatings was enhanced. Thus, it can be said that the electrolyte’s pH enhances to some extent the properties of HAp-based coatings, while the addition of Sr and/or Ag does not negatively impact the obtained features of HAp, indicating that by using pulsed galvanostatic electrochemical deposition, materials with tunable features dictated by the function of the coated medical device can be designed. Full article

(This article belongs to the Special Issue State-of-the-Art on Coatings Research in Romania 2021-2022)

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19 pages, 5552 KiB

Open AccessFeature PaperArticle

Corrosion Improvement of 304L Stainless Steel by ZrSiN and ZrSi(N,O) Mono- and Double-Layers Prepared by Reactive Cathodic Arc Evaporation

by Mihaela Dinu, Anca Constantina Parau, Alina Vladescu, Adrian Emil Kiss, Iulian Pana, Emile S. Massima Mouele, Leslie Felicia Petrik and Viorel Braic

Coatings 2021, 11(10), 1257; https://doi.org/10.3390/coatings11101257 - 15 Oct 2021

Cited by 10 | Viewed by 2230

Abstract

Zr-based nitrides and oxynitrides were deposited by reactive cathodic arc evaporation in monolayer and double-layer structures with the aim of increasing the corrosion protection of 304L stainless steel (SS) in a biomedical aggressive environment. All coatings had a total thickness of 1.2 µm. [...] Read more.

Zr-based nitrides and oxynitrides were deposited by reactive cathodic arc evaporation in monolayer and double-layer structures with the aim of increasing the corrosion protection of 304L stainless steel (SS) in a biomedical aggressive environment. All coatings had a total thickness of 1.2 µm. Compared to the bare substrate, the surface roughness of the coated samples was higher, the presence of microdroplets being revealed by scanning electron micrography (SEM). The X-ray diffraction investigation of the ZrN phases revealed that the peaks shifted towards lower Bragg angles and the lattice constants increased as a result of Si and O₂ inclusion in ZrN lattice, and of the ion bombardment characteristic of the cathodic arc method, augmented by the applied bias substrate. SS/ZrSiN/ZrSi(N,O) showed the best corrosion performance in an acidic environment (0.9% NaCl and 6% H₂O₂; pH = 4), which was ascribed to the blocking effect of the interfaces, which acted as a corrosion barrier for the electrolyte ingress. Moreover, the aforementioned bilayer had the highest amount of Si and O in the composition of the top layer, forming a stable passive layer with beneficial effects on corrosion protection. Full article

(This article belongs to the Special Issue State-of-the-Art on Coatings Research in Romania 2021-2022)

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9 pages, 2087 KiB

Open AccessArticle

Functionalized Carbon Nanotubes for Chemical Sensing: Electrochemical Detection of Hydrogen Isotopes

by Stefan-Marian Iordache, Eusebiu Ilarian Ionete, Ana-Maria Iordache, Ioan Stamatin, Nicolae Catalin Zoita, Arcadie Sobetkii and Cristiana Eugenia Ana Grigorescu

Coatings 2021, 11(8), 968; https://doi.org/10.3390/coatings11080968 - 14 Aug 2021

Viewed by 1772

Abstract

In this study, we propose a palladium-functionalized CNT composite working as a sensitive material to evaluate the deuterium concentration in aqueous samples. The sensitive material was prepared by the deposition of Pd nanoparticles onto MWCNT–OH by the micellization process. A modified electrode was [...] Read more.

In this study, we propose a palladium-functionalized CNT composite working as a sensitive material to evaluate the deuterium concentration in aqueous samples. The sensitive material was prepared by the deposition of Pd nanoparticles onto MWCNT–OH by the micellization process. A modified electrode was prepared by drop casting 60 μL of Pd-decorated MWCNT suspension on a clean glassy carbon electrode surface. The sensing behavior was investigated in a series of deuterium-enriched solutions ranging from 25 to 10,000 ppm. We performed cyclic voltammetry and impedance spectroscopy studies on the samples. The process is quasi-reversible with the reduction curve more pronounced than the oxidation curve, which indicates a low tendency to desorption for the hydrogen atoms. Full article

(This article belongs to the Special Issue State-of-the-Art on Coatings Research in Romania 2021-2022)

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