Y2O3 Coatings Research Articles

Passivation effect on the surface characteristics and corrosion properties of yttrium oxide films undergoing SF6 plasma treatment

This study investigates the structures, compositions and fluorocarbon-plasma etching behaviors of yttrium oxyfluoride (YOF) passivation films fabricated on sputter-deposited yttrium oxide (Y2O3) by high-density SF6 plasma irradiation. High-resolution transmission electron microscopy and nano-beam electron diffraction confirmed a YOF passivation film containing multiple phases of (104) and (006) crystal planes was formed on the fluorinated Y2O3 surface. X-ray photoelectron spectroscopy revealed few changes in the chemical compositions and surface roughness of the YOF passivation film after fluorocarbon plasma etching, confirming the chemical stability of the SF6 plasma-treated Y2O3 sample. The etching depth was ∼20% lower on the SF6 plasma-treated Y2O3 film than on the commercial Y2O3 coating. These results showed that the SF6 plasma-treated Y2O3 films have an excellent erosion resistance properties compared to the commercial Y2O3 coatings.

Microstructure and Properties of 35.8%Fe-20%Ti-20%Al-24%Cr- 0.2%Y2O3 Coatings Prepared by Laser Cladding

Microstructure and Properties of 35.8%Fe-20%Ti-20%Al-24%Cr- 0.2%Y2O3 Coatings Prepared by Laser Cladding

Development of Silicon Carbide Interlayers for Plasma Spray Yttria Topcoat on Graphite for High-Temperature Applications

Abstract Plasma-sprayed yttria (Y2O3) coatings on commercial high-density graphite (HDG) as a chemical barrier coating are presently being explored for uranium-zirconium alloy melting crucibles in pyrochemical reprocessing of spent metallic fuel of future fast breeder reactors. The performance and durability of Y2O3 coatings for high-temperature exposure up to 1,823 K for multiple batch operations are critical to reducing solid active waste generation. However, plasma-sprayed Y2O3 coatings on HDG experience large thermal mismatch stresses due to the difference in the coefficient of thermal expansion (CTE) value of ∼8 × 10−6 K−1 for Y2O3 and ∼4 × 10−6 K−1 for HDG, combined with partial active oxidation of HDG interface leading to premature cracking and spallation of the coating. Silicon carbide (SiC) coating with intermediate CTE (∼6 × 10−6 K−1) offers superior oxidation protection for HDG, which can suitably be used as an interlayer to improve the durability of Y2O3 coatings. In the present work, SiC interlayer coating is developed on HDG substrates using conventional coating techniques such as pack cementation and chemical vapor deposition techniques for subsequent deposition of Y2O3 topcoat by plasma spraying. The thermal fatigue studies simulating uranium melting condition by isothermal hold at 1,723, 1,773, and 1,823 K for 1 h showed twofold improvements in the life of Y2O3 coatings with SiC interlayer. The evolution of thermal cycling damage and failure mechanisms are discussed. The role of interfacial microstructure, the stability of phases, and the underlying mechanisms for life enhancement in the presence of SiC interlayer for plasma-sprayed Y2O3 coating for high-temperature applications are highlighted.

Effects of laser power on microstructure and friction–wear performances of direct energy deposited ZrO2–8%Y2O3–NiCoCrAl coatings on Ti6Al4V alloy

To enhance the hardness and wear resistance performance of Ti6Al4V alloy (TA), ZrO2–8%Y2O3 (8YSZ) coatings with NiCoCrAl as bond coat (BC) were fabricated on TA by laser direct energy deposition (LDED). The morphologies, chemical elements, phases and hardness of obtained coatings were systematically analyzed, and the effects of laser power on the friction–wear performances of 8YSZ coatings were investigated using a high temperature wear tester, and the wear mechanism was also discussed in detail. The results show that the dendrite structures of 8YSZ coatings become small and the eutectic areas decrease with the increase of laser power, and the coating hardness is 933–1078 HV0.5 higher than the TA. The average coefficients of friction (COFs) of 8YSZ coatings decrease with the increase of laser power, which are attributed to the enhancement of coating hardness. The wear rates of 8YSZ coatings deposited at the laser power of 1200, 1500 and 1800 W are reduced by 92.58%–98.52% compared with the TA, and the wear mechanism is dominated by abrasive wear, accompanying with tiny adhesive wear.

Granule spray process for fabrication of adherent, low thermal conductivity ceramic coatings

This study proposes an effective strategy to fabricate ceramic thick films with controllable porosity but strong mechanical adhesion. The technique uses pre-heat-treated granules for a dry spray coating process, granule spray in vacuum. For proof-of-concept, Y2O3 spherical granules were prepared and subsequently pre-heat-treated at various temperatures to control their strength. During film deposition, hard granules (i.e., pre-heated at 1400 °C) caused damage to the substrate and pre-deposited film, owing to a strong hammering effect, which lead to limited film growth (1–2 μm). Contrarily, soft granules (i.e., pre-heated below 800 °C) produced a powder compact with low adhesion, resulting in delamination of some parts. This is attributed to the reduction in kinetic energy caused by the elastic cushioning effect during deposition. Regarding the granules with appropriate strength (i.e., pre-heated at 1000 °C), relatively porous (relative density: 74%) but mechanically well-adhering (adhesion strength: 41 MPa) thick films (~60 μm) were successfully coated on Al substrates. These films exhibited four times higher adhesion strength than those prepared with Y2O3 coatings using atmospheric plasma spraying. The films showed low thermal conductivities (~0.76 W/m·K at R.T.), suggesting potential application of our approach in the field of thermal insulation.

Simulation of the Residual Stress of the Y2O3/Al2O3 Composite Deuterium Permeation Barrier under Thermal Shock

A deuterium permeation barrier is an essential part in the core component of nuclear reactors. It can protect the structure made of steel from being penetrated by deuterium in a fusion reactor. However, residual stress induced in the operation would dramatically influence the mechanical endurance of the coating, threatening the safety of the facilities. In this paper, finite element analysis was conducted to investigate the residual stress in nanoscale Al2O3 and Y2O3 coatings and their composites under thermal shock, from 700°C to 25°C. The max principal stress is assumed as the cause of crack initiation in the coating, because ceramics are brittle and fragile under tensile stress. Max shear stress and max Mises stress in the systems are also analyzed, and the effect of thickness in the range 100 nm to 1000 nm was investigated. The max principal stress in Al2O3 coating reaches its maximum value, 1.33 GPa, when the thickness of coating reaches 450 nm. And the max principal stress decreases at a very low rate as the thickness increases exceeding 450 nm. The max principal stress in Y2O3 coating increases rapidly as the thickness increases when the thickness of the coating is below 250 nm, and the max principal stress is at about 0.9 GPa when the thickness exceeds 500 nm. The max principal stress in the Y2O3/Al2O3 (150 nm) composite coating occurs in the Al2O3 layer and shows no difference from the single layer of 150 nm thick Al2O3 coating. The max principal stress site of all three kinds of coating is located at the edge of the coating 25 nm away from the interface. The result shows that residual thermal stress in the coating increases as the thickness increases when the thickness of the coating is below 200 nm due to the stress singularity of the interface. And as the thickness exceeds 500 nm, the increase in thickness has little impact on the residual thermal stress in the coating. Coating an Y2O3 top layer will not introduce any more residual thermal stress under the thermal shock condition. The Y2O3 coating causes much less residual stress under thermal shock compared with Al2O3 owing to its much lower Young’s modulus. The max principal stress in the 300 nm thick Y2O3 coating is 0.85 GPa while that of the Al2O3 coating is 1.16 GPa. The max residual stress of the composite Y2O3/Al2O3 (150 nm) coating is determined by the Al2O3 layer.

Remote injection casting process with reduced material loss for fabrication of metallic fuels

The remote injection casting process was developed using a high-capacity casting system in a mockup facility to secure the key technology for the fabrication of transmutation metallic fuels in hot cells. Seventy-eight fuel slugs fabricated simultaneously through remote injection casting were confirmed to satisfy the fabrication specification. The reaction characteristics of the coating candidates for the reusable crucible were investigated by using sessile drop tests with U-10wt%Zr-5wt%RE at 1450 °C for 1 h and LaYO3 showed the smallest interaction width. The improvement in the adhesion of Y2O3 coatings on the inner walls of the quartz mold was effective in reducing the reaction between the melt and the mold. The mechanical and chemical cleaning processes were investigated to remove the surface contamination layer of the melt residue for recycling. Both cleaning methods were effective with the mechanical treatment favored owing to the operations in hot cells. The remote injection casting process equipped with fuel loss control components developed in this work will fabricate transmutation fuels in hot cells.

Design of a PLD–grown Y2O3 protective barrier for fusion relevant applications

Advanced and innovative solutions are currently under investigations in order to solve the long-standing issues of materials constituting the breeding blanket of a future fusion reactor. Tritium permeation through steels, corrosion perpetrated by the breeding media, magnetohydrodynamic (MHD) effects and intense neutron irradiation hinder the realization of this technology. Recently, the employment of protective nanoceramic coatings has been considered as one of the few viable solutions. In particular, the pulsed laser deposition (PLD) technique allows to produce dense, compact and uniform coatings, which are the fundamental characteristics when designing a protective barrier. Yttrium oxide (Y2O3) is one of the most promising candidates given its superior stability when facing lithium-based heavy liquid metals and also its low nuclear activation yield, thus it was selected as subject of study and characterzation. PLD-grown Y2O3 coatings were then tested in order to assess their feasability as protective barriers at blanket relevant conditions. Basic characterization of the as deposited and annealed (450 °C) films was perfomed (scanning electron microscopy, atomic force microscope, grazing incident angle x-rays diffraction, nanoindenation). A coated sample was also exposed to static Pb-16Li at.% for 1000 h, showing optimal corrosion resistance and thermal stability at high temperature (550 °C). Finally, the electrical resistivity of this material was measured (up to 200 °C) in order to evaluate its ability to mitigate the MHD detrimental effects. To conclude, a preliminary characterization of the PLD-grown Y2O3 coatings proved the possibility to employ them as multifunctional protective barrier to enable the accomplishment of the breeding blanket technology.

Thermal barrier coatings formed by flame-spray with metal–EDTA

Nowadays, the selection of a suitable spray method to design the coating microstructure such as its porosity, is key to effectively improving the properties of the base materials. In this study, the microstructures and thermal insulation capability of chelate flame-sprayed erbium oxide (Er2O3) and yttrium oxide (Y2O3) coatings directly deposited on aluminum alloy (A5052) substrates were investigated. A rotation apparatus and cooling agent (liquid nitrogen) were used during the synthesis to cool the substrate and control the deposited particles’ shape or form during film deposition. The results show that the Y2O3 coatings had higher thermal insulation capability than the Er2O3 coatings. It is worth noting that the thermal insulation capacity of the Y2O3 and Er2O3 coatings synthesized by cooling the substrate with liquid nitrogen was improved. For thicknesses of 90–128 μm and cross-sectional porosities of 12%–33% of the Y2O3 coatings, a temperature drop (ΔTf = 37 °C) of the porous structure Y2O3 coating at 440 °C and an increase from 0.10 to 0.32 of ΔTf per unit micron (°C μm–1) were observed. This was due to the coating having a more undulated layer surface and more complicated microstructures. Therefore, it is a new idea with the chelate flame-spray method to synthesize thermal barrier coatings on low-melting-point-metal materials.

Microstructure and plasma corrosion behavior of yttria coatings prepared by the aerosol deposition method

AbstractParticle contamination arising from inner ceramic components of the plasma etching equipment has become a serious issue. Yttria (Y2O3) coatings prepared via aerosol deposition (AD) have demonstrated superior plasma resistance in the reduction of particle contamination. The superior particle contamination performance of Y2O3 coatings prepared by AD has been speculatively attributed to its unique microstructure; however, the relationship between the coatings’ microstructure and plasma corrosion behavior has been insufficiently clarified. Herein, we investigated the relationship between the microstructure and plasma corrosion behavior of Y2O3 coatings prepared by the AD method and compared the results with those for coatings prepared by other coating methods. When internal pores are present, these internal pores were selectively plasma corroded; plasma corrosion marks reflecting their pore shape were formed, and the surface roughness increased with increasing plasma exposure time. However, when no internal pores were present, as in the case of the AD coating, the surfaces were homogeneously corroded and maintained their initial surface. As the risk of particle contamination caused by the corrosion of the plasma‐resistant coatings is greatly increased with surface roughness, we concluded that the Y2O3 coating prepared via AD will contribute greatly to reducing particle contamination.

Microstructure and Properties of Al2O3–ZrO2–Y2O3 Composite Coatings Prepared by Plasma Spraying

Al2O3–ZrO2–Y2O3 composite coatings were prepared by plasma spraying Al2O3–ZrO2 composite powder with varying amounts of Y2O3. The effects of Y2O3 on the microstructure and properties of the plasma-sprayed Al2O3–ZrO2 composite coatings were investigated, and the results showed that the composition of the composite powder had a significant influence on the microstructure and properties of the Al2O3–ZrO2–Y2O3 coatings. The Al2O3–ZrO2 and Al2O3–ZrO2–Y2O3 coatings were composed of yttria-stabilized zirconia (YSZ), α-Al2O3, and γ-Al2O3. The Al2O3–ZrO2–Y2O3 coating had a lower friction coefficient and wear rate compared with the Al2O3–ZrO2 coating. The Al2O3–ZrO2–Y2O3 coating showed the most uniform and compact microstructure, highest microhardness, good toughness, and adhesive strength when 3 wt.%Y2O3 was added. This method of adding rare-earth Y2O3 to improve the overall performance of Al2O3–ZrO2 coatings has potential application value.

Special Issue Editorial: Functional Oxide Based Thin-Film Materials

Protective oxide coatings, such as Al2O3 and Y2O3 coatings, are widely used in semiconductor industries because of their hardness, high wear resistance, dielectric strength, high corrosion resistance, and chemical stability for plasma chambers [...]

Nonselective Paul ion trap loading with a light-emitting diode

We demonstrate a simple nonisotope-selective method for ion trap loading, which is based on the irradiation of trap electrodes precoated with materials with a low work function by a light-emitting diode (LED). Photoelectrons emitted from the electrode surface and accelerated in the trap electric field ionize the atomic beam inside the trap, which results in the trap loading. We studied Y2O3 and Mg coatings for the trap electrodes and experimentally demonstrated trapping of single 24Mg+ ions as well as large ion crystals composed of up to 103 particles using a 400 nm LED. This method can be readily implemented in a variety of applications where simplicity, compactness, and robustness are critical, such as in portable ion frequency standards and commercial ion-based devices, for example. Possible modifications of this technique aimed for selective loading, reduction of induced electric stray fields, and getting rid of atomic oven are also discussed.

Contamination Particle Behavior of Aerosol Deposited Y2O3 and YF3 Coatings under NF3 Plasma

The internal coatings of chambers exposed to plasma over a long period of time are subject to chemical and physical damage. Contamination particles that are produced by plasma damage to coatings are a major contribution to poor process reliability. In this study, we investigated the behavior of contamination particles produced from plasma damage to Y2O3 and YF3 protective coatings, which were applied by an aerosol deposition method. The coating materials were located at the powered electrode, the grounded electrode, and the grounded wall, which were exposed to a NF3 plasma. The mass loss at the powered electrode, which was exposed to the NF3 plasma etching under an applied bias, showed that the YF3 etching rate was higher than that of Y2O3. Conversely, the mass of coating increased at the grounded electrode and the grounded wall, which were exposed to NF3 plasma etching under zero bias. The mass of the Y2O3 coating increased more than that of the YF3 coating. X-ray photoelectron spectroscopy analysis showed that the Y2O3 coating corroded to YOxFy in the NF3 plasma, and YF3 existed as YFx. Light scattering sensor analysis showed that the YF3 coating produced fewer contamination particles than did the Y2O3 coating.

Fabrication of Y2O3 coatings by cold-spray

Fabrication of Y2O3 coatings by cold-spray

Contamination Particles and Plasma Etching Behavior of Atmospheric Plasma Sprayed Y2O3 and YF3 Coatings under NF3 Plasma

Yttrium oxide (Y2O3) and yttrium oxyfluoride (YO0.6F2.1) protective coatings were prepared by an atmospheric plasma spraying technique. The coatings were exposed to a NF3 plasma. After the NF3 plasma treatment, the mass loss of the coatings showed that the etching rate of YO0.6F2.1 was larger than that of the Y2O3. X-ray photoelectron spectroscopy revealed that YO0.5F1.9 was present in the Y2O3 coating, whereas YO0.4F2.2 was present in the YO0.6F2.1 coating. Transmission electron microscope analysis conducted on contamination particles generated during the plasma etching showed that both coatings were mainly composed of YFx. The contamination particles estimated by in-situ particle monitoring sensor revealed that the YO0.6F2.1 compared with the Y2O3 coatings produced 65% fewer contamination particles.

Manufacturing and Macroscopic Properties of Y2O3 Coating Layer on Ceramic (AlN) Substrate Fabricated by Aerosol Deposition

Manufacturing and Macroscopic Properties of Y2O3 Coating Layer on Ceramic (AlN) Substrate Fabricated by Aerosol Deposition

Phase composition, structural, and plasma erosion properties of ceramic coating prepared by suspension plasma spraying

AbstractY3Al5O12 (YAG), Y2O3, and Al2O3 ceramic coatings were manufactured to investigate the plasma erosion properties. The X‐Ray Diffraction (XRD) analysis confirmed that YAG coating was synthesized successfully by Y2O3 and Al2O3 mixture suspension using the plasma spraying method. Meanwhile, metastable phases were found in Y2O3 and Al2O3 coatings due to the quenching in cooling process of melted droplets. The coating surface morphology and microstructure of cross sections were characterized by SEM. The results reveal that coatings are composed by ultrafine splats and exhibit dense lamellar structure. The plasma erosion properties were evaluated at different etching test power under Ar/CF4/O2 plasma gas. The experimental results clarify that both of YAG and Y2O3 coatings show the better plasma erosion resistance than Al2O3 coatings. The formation of fluorination layer surface prevents the coatings from further erosion with plasma gas. Moreover, the etching rate of coatings depended on the fluorination and removing rate of fluoride layer.

Comparisons of NF3 plasma-cleaned Y2O3, YOF, and YF3 chamber coatings during silicon etching in Cl2 plasmas

Optical emission spectroscopy was used to investigate the effect of Y2O3, YOF, and YF3 chamber wall coatings on the relative number densities of gaseous species during etching of Si in Cl2/Ar inductively coupled plasmas. Etching plasmas were alternated with NF3/Ar plasma chamber-cleaning steps. Small differences were found for the three materials. Si-to-Cl emission ratios were similar for Y2O3 and YOF, and somewhat larger for YF3. SiClx=1–3 emissions were similar for the Y2O3 and YOF-coated liners, but significantly less stable with time for YF3. Compared with Cl2/Ar plasmas, Cl2/O2/Ar plasmas produced nearly time-independent and much more consistent Cl number densities during etching. This takes place despite a consistent upward drift in SiClx=0–3 emissions for all three materials. A conditioning procedure for the YOF coating was shown to reduce drift during Si etching in Cl2 plasmas. Specifically, a Cl2/O2/Ar plasma pretreatment was briefly operated with substrate bias, generating SiClx etching products that rapidly remove F from the liner surface. When the O2 flow was extinguished, etching continued with much less changes in Cl and SiClx relative number densities.

The effect of the deposition sequence of sol-gel SiO2-Al2O3, CeO2 and Y2O3 coatings on the corrosion resistance of the FeCrAl alloy during cyclic high-temperature oxidation

The surface of a ferritic FeCrAl alloy was covered with three-layer ceramic coatings by the sol-gel method. The SiO2-Al2O3, Y2O3 and CeO2 layers would be deposited in different sequences. The obtained material would be subjected to cyclic oxidation at a temperature of 900 °C. It was found that the sequence in which the layers are deposited affects the morphology and chemical composition of the scale. After 20 oxidation cycles (each lasting 12 h) the thickness of the building up oxide film amounted to 2.3–4.2 μm. Gravimetric analyses showed the parabolic character of the weight gain-oxidation time interdependence. The first layer deposited on the metallic surface determines the distribution of yttrium and cerium in the scale and in the alloy core. The scale building up on the samples in which yttrium oxide formed the first layer was found to have the most advantageous protective properties. After 20 oxidation cycles the FeCrAl alloy coated in turn with the layers: Y2O3, CeO2 and SiO2-Al2O3 showed the smallest relative change in weight. In comparison with the uncoated substrate the protection effectiveness of the deposited coatings amounts to 12–37%.