Addition Of Rare Earth Oxides Research Articles

Incorporation of neodymium, holmium, erbium, and samarium (oxides) in zinc-borotellurite glass: Physical and optical comparative analysis

Investigating the effect of different types of rare-earth oxides on zinc borotellurite glass is important to determine the potential application in optical devices. The addition of rare-earth oxides in zinc borotellurite glass is well-known to enhance the optical properties due to the effects of 4f-4f transitions. In this work, we aim to compare the effect of different rare-earth oxides on zinc borotellurite glass denoted as ZBTNd, ZBTHo, ZBTEr and ZBTSm. The glass samples were successfully fabricated via the melt-quenched technique. The physical investigation of the glasses has been done by measuring the density and molar volume. It was found that ZBTNd glass has the lowest density than the other glasses due to the small atomic radius in neodymium oxide. High-density value for ZBTHo glass shows potential to be used as radiation shielding properties. The high value of molar volume for ZBTNd glass is advantageous for fiber optics as ZBTNd glass has good performance in elasticity. It was found that ZBTEr has a lower refractive index than the other glasses due to low dispersion characteristics. However, ZBTEr glass has good performance to be used in optical communication applications. It was found that the optical absorption shifts to a longer wavelength beginning from ZBTEr > ZBTHo > ZBTNd > ZBTSm. The optical band gap energy for ZBTEr glass is higher than the other glasses due to the Coulomb repulsion energy for erbium which is greater than neodymium and samarium and slightly higher than holmium. The pattern of electronic polarizability for all glasses was found as follows ZBTSm>ZBTNd>ZBTEr>ZBTHo. The optical basicity for ZBTEr was found highest which indicates a higher acidity, meanwhile, the ZBTNd glass has the lowest value which corresponds to a higher basicity.

Multifunctional rare earth oxide/MBG composite microspheres as a carrier for bone tumor treatment

With the development of advanced composites, biomaterials have brought the field of tissue engineering and regeneration into a new era. Among them, composites of inorganic nonmetallic materials and rare earth oxides have unique structures and biochemical properties and have attracted widespread interest. In this work, rare earth oxides (CeO2)/inorganic nonmetallic materials (mesoporous bioactive glass, MBG) composite microspheres (CeO2/MBGs) were synthesized by a sol-gel method, and the in vitro biological effect of CeO2/MBGs was systematically studied. The filling of CeO2/MBGs in irregular bone tumor defects not only promoted osteogenic mineralization in MG63 cells but also had significant antibacterial effects on E. coli and S. aureus. CeO2 enters the MBG network as a network modifier, while doxorubicin (DOX) is adsorbed into the mesoporous structure through electrostatic interactions, which endows CeO2/MBGs with excellent bioactivity and controlled DOX release behavior. Moreover, the results of in vitro experiments showed that the proper addition of rare earth oxides had no toxic effect on normal cells, and the combination of rare earth oxides with antitumor drugs could slow the release of DOX through the use of an intelligent response design system, thus inducing the apoptosis of MG63 cells. This work suggested that combination chemotherapy and the design of a rare earth oxide/MBG composite microspheres may be potential therapeutic approaches for the postoperative repair of bone tumor defects. The construction of this multifunctional rare earth oxide/inorganic biocomposite provides a way to apply the material to bone tissue.

Effect of different rare earth fluoride doping on microstructure and ablation properties of C/C–ZrC–SiC composites prepared by molten salt assisted reactive melt infiltration

The effect of doping with rare earth elements of different ionic radii on the ablation resistance of C/C–ZrC–SiC composites was investigated and the ablative behavior and ablation resistance of C/C–ZrC–SiC composites with the addition of different rare earth elements was tested. Although rare-earth doped stabilized zirconia has been used for a long time in the field of thermal barrier coatings, the existing techniques are usually coating modifications with rare-earth oxide or boride additions, it is difficult to prepare coatings that can be used on the surface of carbon matrix materials due to the large difference in the coefficients of thermal expansion. Therefore, this study attempts to introduce rare earth components into the interior of C/C–ZrC–SiC composites for matrix modification. The results show that the addition of rare earth elements enhances the ablation performance of the composites, but the mechanism of enhancement is different: rare earth ions with a smaller radius difference from Zr4+ ions stabilize the crystal structure of ZrO2 by forming replacement solid solutions and stabilize the surface oxide film structure by preventing the homogeneous multiphase transformation of the oxide to achieve higher ablation performance; whereas rare earth ions with a larger radius difference from Zr4+ ions cannot stabilize ZrO2 by replacement solid solutions, but instead form high viscosity, low volatility liquid phase oxides to heal the surface defects of the oxide film and reduce liquid phase dissipation to enhance ablation performance.

Effects of rare earth oxide additions on the corrosion resistance of TiC-based cermets

TiC-based cermets have inadequate corrosion resistance despite wide use in high-performance applications. Rare earth dopants like Nd2O3 and Yb2O3 aim to improve cermet properties, but their impacts on corrosion are unclear. This work prepared 0.7 wt% Nd2O3- and Yb2O3-doped TiC cermets via vacuum sintering. Experimental results revealed that Nd2O3 doping enhances corrosion resistance by promoting α-FeOOH in corrosion products, while Yb2O3 doping has little effect. First-principles calculations confirmed that Nd promotes α-FeOOH formation. By elucidating contrasting dopant impacts on corrosion, this study provides new insights to guide optimization of rare earth-containing cermet compositions for superior corrosion resistance.

Thermal activation energy on electrical degradation process in BaTiO3 based multilayer ceramic capacitors for lifetime reliability

For a high capacitance and high lifetime reliability of multilayer ceramic capacitors for automotive applications, the activation energy on thermal activation process can typically be calculated by using Arrhenius based Prokopowicz–Vaskas equation as a method for lifetime prediction. In this study, it is clearly observed that the activation energy shows to be constant in the range of ~ 1.5 eV for the prototype MLCCs, higher than the activation energy values of ~ 1.0 eV related to the motion or diffusion of oxygen vacancies reported in the previous literature. The activation energy value of ~ 1.5 eV for three prototype MLCCs is close to a half the energy band gap (Eg/2 ≈ 1.6 eV) of BaTiO3 obtained from specific environment, where oxygen vacancies are stabilized by external containment such as the effect of rare earth oxide additives. Due to an obvious difference in activation energy values, it difficult to explain the conduction mechanism for failure by only oxygen vacancy migration. Therefore, the concepts of electronic processes and oxygen vacancy should be considered together to understand conduction mechanism for failure of BaTiO3-based MLCCs in thermal activation processes. It can be useful as an indicator for future MLCC development with high lifetime reliability.

On issue of effect of rare-earth metals on microhardness and microfragility of borated layers obtained by liquid electrolysis-free boriding on multi-alloy steels

The structure and properties of borated layers obtained on differently alloyed steels in melts with various additions of rare-earth oxides are studied. It is shown that the presence of a rare-earth oxide additive increases depth of borated layers, and also makes it possible to reduce their microhardness from standard values of 1900...2100 HV 0.1 to 1600...1800 HV 0.1 and microfragility: the values of the microfragility index for all studied samples decreased by more than 2 times.

Study on the Effect of Rare Earth Oxide Addition on the Microstructure and Properties of Ni60/WC-Ni Coatings Prepared by Laser Cladding

Rare earth oxides have been proven for their ability to refine grains and have high melting points. In this paper, different contents of rare earth oxide La2O3 were added into the Ni60/WC-Ni composite coating, in order to study its effect on the coating properties. SEM observation confirmed that the grain was refined significantly after the addition of La2O3. Energy Dispersive Spectroscopy (EDS) was applied to investigate the composition and X-Ray Diffraction (XRD) was used to measure the residual stress in the coating samples. In addition, the microhardness and wear resistance of the samples were tested. The results showed that the dilution ratio of coatings with different additions of La2O3 was in the range of 2.4 to 9.8%, and the sample with 1.0% addition of La2O3 exhibited the highest hardness of 66.1 HRC and best wear resistance with a wear volume of 9.87 × 106 μm3, and the residual stress increased from 159.4 MPa to 291.0 MPa. This implies that the performance of the coating has been obviously improved after the addition of La2O3.

Effect of rare earth oxide (Y2O3) addition on wear characteristic of TiB2 ceramic reinforced Mo-based composite coating fabricated by Argon shielded Arc cladding

In this study, Mo-based composite coatings with 1 wt.% of rare Earth oxide (Y2O3) contents were successfully manufactured on AISI SS304 (stainless steel) by argon shielded arc (ASAC) cladding method. The effect of Y2O3 on phase composition, microstructure, mechanical and tribological properties of Mo-based coatings were investigated by x-ray diffraction (XRD), Field emission scanning electron microscopy (FESEM) with energy dispersive x-ray spectrometer (EDS), micro-Vickers hardness apparatus and pin-on-disc type wear tester. The result demonstrates that the upper surface of composite coating with and without addition of Y2O3 were mainly comprised of TiB2, Ni3Ti, Fe3Mo, MoNi4, NiTi, Mo2B, Y2TiO7, Cr2Ti, Fe3B, Y2O3, and MoNi4 appeared. The constituent phase components in the coated layer were found to be beneficial for the enhancement of the microhardness and wear resistance. The maximum value of average micro-hardness and wear resistance was observed in samples having 1 wt.% of Y2O3 as a precursor. The average microhardness of Mo-based coatings with Y2O3 addition was in the range of 1599 to 2170.4 HV0.1 and wear resistance increases from 1.41 to 6.36 × 10−8 g/N-m. The pronounced effect of Y2O3 addition on microhardness and wear resistance of coatings were consistent with the calculation results of applied multivariate statistical analysis. Thus, it can be concluded that the addition of Y2O3 is effective and achievable way to solidate hardness and wear resistance of Mo-based coatings.

Densification Behavior, Microstructural Development and Mechanical Properties of Spark Plasma Sintered α/β-Silicon Nitride Ceramics with Different Rare Earth Oxide Additives

ABSTRACT Monolithic Si3N4 ceramics were fabricated by spark plasma sintering at 1750°C for 15 min under 50 M Pa applied pressure using α-Si3N4 powder with 2 wt% Y2O3, 2 wt% Dy2O3, 2 wt% Eu2O3 and 8 wt% Y2O3 as single rare earth oxide additives. It aimed to investigate the effects of the composition and content of rare earth oxide additives on densification, microstructural development, and mechanical properties of α/β-silicon nitride ceramics via XRD and SEM analyses, temperature and displacement curves obtained through spark plasma sintering and mechanical tests. Addition to 2 wt% Y2O3 as an additive into composition resulted in high relative density (98%), hardness (14.9 GPa), and fracture toughness (9.8 M Pa.m1/2). The use of Dy2O3 instead of Y2O3 decreased β-Si3N4 phase ratio and densification rate. This behavior continued further with Eu2O3 addition. The increment of Y2O3 content to 8 wt% provided the same relative density and fracture toughness (98% and 9.8 M Pa.m1/2), whereas hardness was reduced to 12.6 GPa. As a result, densification was achieved only by Y2O3 addition regardless of additive content, and both high hardness and fracture toughness were obtained using only 2 wt% Y2O3 as a single additive.

Effect of Rare Earth Oxide Addition on Regenerated Cemented Carbide

Effect of Rare Earth Oxide Addition on Regenerated Cemented Carbide

A study of Ni–P electroless coating modified by rare earth oxide (La2O3, Y2O3 and Ce2O3) on pre-phosphorized zirconium alloy

Electroless Ni–P coatings are successfully deposited on the surface of pre-phosphorized zirconium alloy from plating baths containing various concentrations of rare earth oxide (Re Y2O3, Ce2O3 and La2O3). The surface morphology, elementary composition, and structure of coatings are characterized by scanning electron microscopy, energy dispersive X-ray spectrometer and X-ray diffraction, respectively. Gravimetrical method is used to calculate the deposition rate. Electrochemical corrosion resistance of coatings is analyzed using electrochemical workstation. Results revealed that a small amount addition of rare earth oxides does not change the original cauliflower-like morphology and amorphous structure of coatings. When the amount of addition is moderate, the deposition rate and microhardness increase with the increment of the amount of addition, while P content decreases. However, excessive addition can lead to poisoning of the plating bath. Electrochemical corrosion data indicates that the addition of rare earth oxide in the plating solution has little influence on the corrosion resistance of the coating.

Characterization of erbium oxide doped HP-HVOF deposited carbide ceramic coating on martensitic steel

Rare earth elements (REEs) are known as the “vitamin or nutrients” of metals. The addition of rare earth in a limited quantity can enhance the properties of materials. This article elucidates the effect of doping of rare earth oxide (0.9 wt.% Er2O3) on the mechanical and surface behavior of tungsten carbide (WC-10Co-4Cr) based coatings developed using high pressure high velocity oxygen fuel (HP-HVOF) thermal sprayed techniques on martensitic stainless steel (SS410). With the addition of rare earth oxides, the result shows that the hardness of the deposited coating (HV1261.17) is far higher than the substrate (HV193.47). The modulus of elasticity and flexural strength is enhanced for the coated sample as compared to the substrate. The porosity level of the coating is found to be less than 1% and the static water contact angle for coated surface (≈125.1°) shows the coated sample is hydrophobic in nature. The surface characterization was done using the scanning electron microscope attached with energy dispersive X-ray analysis which has identified the presence of various elements on the surface including rare earth. The surface of coated samples has various phases of rare earth oxides such as monoclinic and cubic rare earth oxides. Moreover, its compounds such as Co3W3C were confirmed by X-ray diffraction measurements. After comparing previous literature with current results can conclude that the addition of rare earth oxides (0.9 wt.% Er2O3) on carbide coatings enhanced the various properties of materials.

Effect of Rare-Earth Oxides on Reaction Sintered Non-Stoichiometric Magnesium Aluminate Spinel

Non-stoichiometric spinel compositions with molar ratio of MgO:Al2O3 = 1:2 and 2:1, were prepared via single-stage reaction sintering technique at 1550°-1600°C using commercial grade oxide reactants. The effect of different rare-earth oxides, viz. CeO2, La2O3 and Y2O3 at 2 wt% level on the properties of different spinel batches was studied. Y2O3 was found to favour densification in both the spinel batches while CeO2 and La2O3 were found to favour densification only in the MgO-rich spinel compositions. Phase analysis revealed that Y2O3 containing Al2O3-rich spinel has a secondary phase with similar crystal structure to spinel (both cubic) and improved densification, while in the MgO-rich condition, Y2O3 remained as secondary phase and assisted in densification. CeO2 and La2O3 in Al2O3-rich samples formed secondary phases with different crystal structures and resulted in reduced densification. While in MgO-rich condition, CeO2 (cubic) did not react with Al2O3 and La2O3 formed a secondary phase with similar crystal structure as that of spinel and therefore assisted in densification. Addition of rare-earth oxides led to improvement in strength of MgO-rich spinels and maximum improvement in strength was observed with the addition of yttria.

Effect of rare earth oxide microparticles on mechanical, corrosion, antibacterial, and hemolytic behavior of Mg-Hydroxyapatite composite for orthopedic applications - A preliminary in-vitro study.

The current study focused on developing a multifunctional Mg-based biodegradable composite that mitigates the trade-off between strength, antibacterial, and cytotoxicity behavior for orthopedic bone implants. The composite has been reinforced with natural mineral-based Hydroxyapatite and rare earth oxide (REO): Neodymium oxide. The effect of different concentrations of REO on the mechanical, antibacterial, and corrosion properties was analyzed. The antibacterial properties were assessed against gram-positive B. Subtilis and gram-negative E. Coli bacterial pathogens. Moreover, the cytotoxicity of the composites was assessed via Hemolysis percentage calculations. In addition, the microstructure characterization was performed via FESEM, XRD, and EDS techniques, and different intermetallic phase formations were recorded. Contact angle measurements were done via the sessile drop method to analyze the impact of rare earth oxide on the surface properties of the synthesized composites and their relationship with bacterial adhesion. The corrosion studies and swelling rates were performed under PBS and DMEM solutions. The composite with the addition of 1.5% REO outperformed the experiments with a compressive strength of 126.4MPa, and a corrosion rate less than 0.2 mm/yr. The corrosion rates and degree of swelling were seen to be more stable in DMEM solution as compared to PBS. Improved antibacterial rates were observed against both pathogens after the addition of REO along with a hemolysis percentage less than 5% for Mg-HA-1.5Nd2 O3 . The composites showed increased hydrophobicity (>75%) by the addition of 1.5% REO. Hence, it was concluded that REO (Nd2 O3 ) addition to the Mg-Hydroxyapatite composite is a feasible choice as a biomaterial for bone implant applications.

Modification of barium titanate sintering via rare earth oxides addition: Dilatometric and microstructural study

In this paper, the effect of rare-earth dopants (RE: Ce, Eu, Tb, Dy, and Er) in barium titanate (BT) on the shaping, sintering and microstructure was studied aimed mainly at selecting appropriate dopant for densification delaying while preserving optimal BT characteristics. The addition of dopant oxides into suspension resulted in the reduction of the deposition kinetics. The relative density of doped green bodies was lower than pure BT and decreased with dopant concentration. Only Ce enhanced green density up to 2%. The sintering process was studied using high-temperature dilatometry. The hindering densification caused by dopants was observed, but only 5 wt % of Tb and Er in BT shifted the onset of sintering to higher temperatures that has the potential applicability of these materials in layered ceramic harvesters. The significant positive impact of doping on the microstructure was attained almost in all cases manifesting themselves in higher sintered densities and markedly lower mean grain size compared to pure BT. The XRD and Raman spectroscopy analyses confirmed incorporation of the dopants into the perovskite structure and no significant existence of RE-enriched secondary phases in the microstructure.

Deposition mechanisms and characteristics of nano-modified multimodal Cr3C2–NiCr coatings sprayed by HVOF

Abstract Nano-modified multimodal and conventional Cr3C2–NiCr coatings were fabricated by high-velocity oxygen-fuel spraying deposited on CuCrZr substrates. Results showed that individual nano-modified multimodal Cr3C2–NiCr particles were composed of nano (25−180 nm), submicron (200 nm to 0.5 μm), and micron (2–4.5 μm) Cr3C2 grains, NiCr binder phases, and a tiny amount of rare earth oxide additives. The nano-modified multimodal Cr3C2–NiCr coatings maintained a unique structure: submicron Cr3C2 grains embedded in the voids formed by micron Cr3C2 grains, NiCr binder phases and nano Cr3C2 grains imbedded in the voids formed by submicron and micron Cr3C2 grains, and nano Cr3C2 grains are dispersed in NiCr metal binder phases. A few discontinuous elongated amorphous and nanocrystalline phases existed in them. The mechanical interlocking was the dominant bonding mechanism accompanied by local metallurgical bonds. Compared to the conventional coating, the multimodal coating was uniform and dense (porosity was 0.3 ± 0.12%) as well as not obvious lamellar structures, the adhesive strength was 75.32 ± 1.21 MPa, exhibiting a 65 pct increase, and the microhardness was increased by about 18%. The lower porosity and higher strength of nano-modified multimodal structure coating were mainly related to dispersion distribution and synergistic coupling effects of Cr3C2 hard grains with different scales.

Effect of rare-earth oxide additives on transparency and fluorescence of α-SiAlON ceramics

Recently, novel transparent and fluorescent materials are in demand for various optical applications such as lasers, scintillators, and solid-state lighting. α-SiAlON, which has excellent thermal and mechanical properties, also exhibits photoluminescence depending on the stabilized doped rare-earth ions. Its transparency and fluorescence depend on the rare-earth oxide added as a raw material, particularly in conventional powder processing. In this study, we fabricated α-SiAlON ceramics by adding various rare-earth oxides to elucidate their effects on the transparency and fluorescence of these ceramics. High-transparency α-SiAlON ceramics were fabricated by adding rare-earth oxides whose rare-earth ions have small ionic radii: Y2O3, Ho2O3, Er2O3, Tm2O3, Yb2O3, and Lu2O3. Because the fraction of α-SiAlON was high, the relative density was high, and the microstructure was composed of fine grains. In particular, α-SiAlON ceramics prepared by adding Ho2O3 showed lower light scattering than the other fabricated α-SiAlON ceramics because of the smaller α-SiAlON grains, resulting in higher in-line transmittance (48% at 600 nm). Furthermore, these transparent α-SiAlON ceramics exhibited fluorescence corresponding to the activated rare-earth ions: Ho3+, Er3+, Tm3+, and Yb3+ or Yb2+.

Advancements in carbon fibre reinforced ultra-refractory ceramic composites: Effect of rare earth oxides addition

Continuous carbon fibre ceramic matrix composites capable of tolerating multiple thermal-shock cycles and resisting ablation are needed for aerospace and hypersonic systems. Carbon fibre around 50 vol% and ultra-refractory matrices are fundamental parameters. The influence of rare earth (RE) oxides on the microstructure and mechanical properties of carbon fibre-ZrB2/SiC composites was investigated. Materials were produced by slurry infiltration and hot pressing. The addition of Y2O3, La2O3 and CeO2 led to the formation of lamellar boro-carbides that improved the densification, while Sc2O3 promoted the formation of (Zr,Sc)B2 solid solutions in the matrix. All these composites exhibited improved mechanical properties compared to a RE-free baseline, with room temperature strengths and toughness above 330 MPa and 9 MPa m0.5, respectively, and strengths above 600 MPa at 1500 °C. The lamellar phase was identified as a fibre by-product with general formula REB2C2. Only CeO2 was detrimental on the long run due to its high reactivity with humidity which induced swelling and jeopardized the structural stability of the composite.This study revealed new fundamental insights into the microstructure evolution of carbon-fibre refractory composites and its impact on the mechanical properties, which will contribute to the development of new generation of reusable ceramic matrix composites for harsh environments.

Achieving an unprecedented strength-ductility balance of molybdenum alloy by homogeneously distributing yttrium-cerium oxide

Rare earth (Y/Ce) were homogeneously distributed in molybdenum alloys by liquid-liquid doping and powder metallurgy method, and the molybdenum alloys plates were obtained after rolling. The results show the rare earth form nanoscale Y2O3 and CeO2 particles which were concomitant in molybdenum matrix. The rare earth oxides particles significantly refine microstructure and improve mechanical properties of the rolled molybdenum plate. The adding of 0.8%Y2O3 and 0.12%CeO2 made the micro fringe spacing in microstructure of rolled molybdenum alloy reduce 52.43%. The newly developed molybdenum alloys have an unprecedented strength-ductility balance compared with previous other molybdenum alloys. And high tensile strength and elongation were obtained simultaneously. The tensile strength of the rolled Mo-0.8%Y2O3-0.12%CeO2 alloy plate reaches 917 MPa with a 13.9% elongation, increased by 21.9% and 55.5% over a pure molybdenum plate, respectively. The strength-elongation product of the new molybdenum alloy annealed at 1200 ℃ could reach 2.4 times that of pure molybdenum. The addition of the nanoscale rare earth oxides to the Mo-alloy introduces Orowan strengthening and fine grain strengthening which changes fracture mode, resulting in excellent strength-ductility balance.

Development and characterization of alumina-toughened zirconia (ATZ) ceramic composites doped with a beneficiated rare-earth oxide extracted from natural ore

This work analysed the effect of the addition of rare-earth mixed oxide (RE2O3), a solid solution of Y2O3 and other rare earths benefited from a Brazilian natural ore called Xenotime, on the sintering and properties of a commercial nanopowder composed of Ce-tetragonal polycrystal zirconia (TZP) + 15 wt.% Al2O3. Powder mixtures were prepared, adding 10 wt.% of Y2O3 or 10 wt.% RE2O3 in Ce-TZP/Al2O3 powder, which were compacted and sintered at 1500 °C for 2 h. Sintered samples were characterized by X-ray diffraction, scanning electron microscopy, and relative density. Structural analyses and phase quantification were performed using the Rietveld refinement method. Mechanical characterization - Vickers hardness and fracture toughness - of the samples was carried out by Vickers indentation. The results indicated that the RE2O3 is composed of a solid Y2O3 solution with lattice parameters slightly lower than those of pure Y2O3 due to the presence of other oxides such as Yb2O3 (19.7%), Er2O3 (13.9%), or Dy2O3 (10.2%). During sintering, the oxides added to the composite were completely consumed by the Ce-TZP/Al2O3 matrix to form two different crystalline phases: ZrO2-Cubic and Y3Al5O12. As a consequence, multi-phase composites with relative density of 93.8 ± 1.2 (Y2O3 reinforced) and 94.5 ± 1.7 (RE2O3 reinforced), average hardness in the order of 10.5 GPa, and fracture toughness of 7.1–8.5 MPa m1/2 were obtained. The high fracture toughness observed was a consequence of the presence of different coupled toughening mechanisms resulting from the multiphase characteristic of these composites.