Rare Earth Metal Oxides Research Articles

Probing crystalline phase effect of rare earth metal oxides (REO) on Cu/REO (RE=Gd, Eu, Sm) catalysts for methanol steam reforming (MSR) to produce H2

In this work, to study the phase structure effect, three groups of Cu/REO catalysts were prepared with cubic and monoclinic Gd2O3, Eu2O3 and Sm2O3 supports for MSR reaction to produce H2. Based on CH3OH conversion and H2 yield, the reaction performance of the catalysts ranks as Cu/Sm2O3-M > Cu/Sm2O3–C > Cu/Gd2O3-M > Cu/Gd2O3–C > Cu/Eu2O3-M > Cu/Eu2O3–C. For the same kind of REO, Cu supported on the monoclinic support shows better performance than on the cubic one. Despite the phase structure difference, Sm2O3 is the best support among all the three kinds of REOs. Compared with Cu/REO catalysts prepared with cubic supports, the corresponding catalysts prepared with monoclinic supports generally possess more surface oxygen vacancies, which can generate more surface active oxygen (O2–) and moderate basic sites. Moreover, the contents of Cu + on the catalysts follow the same sequence. The reaction performance is positively related to the amount of these three types of surface sites. But metallic Cu0 species is necessary to maintain the Cu+ ↔ Cu0 redox cycle. Furthermore, on a catalyst with good performance, those vital surface reaction intermediates can be stabilized during the reaction. Cu/Sm2O3-M possesses the largest quantities of these surface sites, and has the appropriate amount of Cu+ and Cu0 after reduction, thereby displaying the optimal performance in all the catalysts. In conclusion, evident support crystal structure effect is observed for Cu/REO catalysts, and a monoclinic phase REO is a better support than the respective cubic phase one.

Comparative studies on promotional effect of Pr6O11, Nd2O3 and Sm2O3 on Ni–SiO2 for pressurized carbon dioxide reforming of methane

The 7 wt% rare earth metal oxide promoted Ni–SiO2 catalysts of Ni–7Pr6O11–SiO2, Ni–7Nd2O3–SiO2, and Ni–7Sm2O3–SiO2 were prepared by the complex-decomposition method, and were comparatively evaluated for pressurized carbon dioxide reforming of methane (CRM) under severe conditions of 750 °C, 1.0 MPa, CH4/CO2 = 1, and gas hourly space velocity of 53200 mL/(g·h). The addition of rare earth metal oxide does not affect the Ni dispersion, and all of the catalysts show similarly high Ni dispersion of 16.0% ± 0.2%. As a result, all of the catalysts are highly active for pressurized CRM, the initial CH4 conversions of which approach the thermodynamic equilibrium (47.0% ± 0.2%). In contrast, a clearly favorable effect of the added rare earth metal oxide on the stability of Ni–SiO2 was revealed from the CRM results for a time-on-stream of 50 h, and the highest stability without an observable decrease in the conversions of CH4 and CO2 was obtained over Ni–7Sm2O3–SiO2. Based on the characterization results of thermogravimetric differential scanning calorimetry (TG-DSC) and transmission electron microscopy (TEM), the improved stability of Ni–7Pr6O11–SiO2, Ni–7Nd2O3–SiO2, and Ni–7Sm2O3–SiO2 for pressurized CRM was manifested mainly as the suppressed formation of carbon nanotubes over the catalyst surface, the extent of which is dependent on the specific rare earth metal oxide. Moreover, the consecutive temperature programmed surface reaction of CH4, CO2, and O2 over Ni–7Sm2O3–SiO2 vigorously reveals that the addition of Sm2O3 into Ni–SiO2 inhibits the CH4 decomposition but enhances the oxidization of the carbon species by CO2, leading to the well-balanced rates for forming and removing the coke over Ni–7Sm2O3–SiO2. These findings are not only beneficial to deeply understanding the promotional effect of rare earth metal oxides on Ni-based catalysts for CRM, but also important for extending the application of the less studied rare earth metal oxides as promoters for the metal-supported catalysts.

Role of rare-earth oxides, conjugated with [Formula: see text], in the enhancement of power conversion efficiency of dye sensitized solar cells (DSSCs).

Different rare-earth (RE) metal-oxides nano-particles (NPs) viz. Samarium (III) oxide (Sm2O3), Neodymium (III) oxide (Nd2O3), and Gadolinium (III) oxide (Gd2O3) were synthesized using co-precipitation route, and investigated by structural, optical, and morphological studies. Findings and supporting studies were presented to understand the role of RE-metal-oxides NPs as photo-anode material for dye sensitized solar cells (DSSCs) applications. Structural analysis of prepared RE-metaloxides, by X-ray diffraction (XRD), reveals the crystalline nature of the particles ranging from 24 to 37nm. Morphological study by field emission scanning electron microscopy (FESEM) supports the crystalline nature in the nano range of the prepared RE-metaloxides particles. The observed d values of each sample support the growth of Gd2O3, Nd2O3, and Sm2O3 material. The band-gap of prepared material was estimated from the UV-VIS absorption data and Tauc relation. The observed band gap values are 3.55eV, 3.31eV, and 3.52eV for Gd2O3, Nd2O3, and Sm2O3 respectively. These values are reasonably high compare to the bulk values, indicates the nanostructure formation. Optimized RE-metal oxides NPs employed in the form of TiO2 photo anode for the fabrication of DSSCs. FESEM confirms that the Gd2O3-based photo-anode shows more uniform and decent coverage with more porosity on the TiO2. The EIS measurements of prepared DSSCs also supported the improvement in the photovoltaic output for the modified photo-anode devices as cells with modified photo-anode exhibited less charge recombination at the photo-anode/dye/electrolyte interface with increased electron lifetime leading to improved device performance as compared to the unmodified-based DSSCs. The highest efficiency 5.51% was demonstrated by [Formula: see text]/[Formula: see text] photo-anode-based DSSCs compare to Sm2O3, and Nd2O3 activated photo-anode.

A universal multifunctional rare earth oxide coating to stabilize high-voltage lithium layered oxide cathodes

The interfacial instability and bulk structural degradation of the high-voltage lithium layered oxide (LLO) cathodes make them suffer from severe capacity and voltage decay. Here, a universal multi-electron surface engineering strategy has been developed to conquer the root causes of the instability of LLO. The Gd in Gd2O3 with rich high-orbit extranuclear electrons is selected as an exemplary coating material to enhance the lithium storage properties of the LiNi0.6Co0.05Mn0.35O2 (NCM). On one hand, the Gd2O3 coating tunes the H1-H2 phase transition from a two-phase to quasi single-phase reaction and weakens the harmful H3 phase transition, minimizing the mechanical degradation of NCM. On the other hand, the Gd2O3 coating increases the activation energy of surface lattice oxygen loss and delays the phase transition temperature, inhibiting the oxidative decomposition of electrolyte and harmful interface phase transition and enhancing the thermal stability of the material. Thanks to these benefits, the Gd2O3-coated NCM experiences a weaker discharge median voltage decay after 100 cycles, and an 88.1% capacity retention rate could be achieved after 400 cycles. Furthermore, the generalizability of the multi-electron surface engineering strategy is certified by all rare earth metal oxides with boosted electrochemical performance for NCM.

Tribological characterization of functionally gradient wind turbine brake pads reinforced with rare earth metal oxide

Copper-based brake pad materials with various fractions of praseodymium oxide and yttrium oxide are fabricated through the powder metallurgy processing technique. The influence of praseodymium oxide and yttrium oxide on the microstructure, microhardness, and tribological characteristics of the fabricated specimens are analyzed. The specimen with desired density, high hardness, wear resistance, and optimal friction coefficient is fabricated with gradient layers (pure copper at the brake pad – brake caliper interface and composite at the brake pad – brake disc interface). The result suggested that as the load gradually increases, the wear rate also increases. The surface morphology, elemental composition, and phase composition of the fabricated specimen and worn surface were characterized using advanced instrumental characterization.

Quantum dot-doped CeOx-NiB with modulated electron density as a highly efficient bifunctional electrocatalyst for water splitting.

Development of economical, efficient and durable non-noble metal electrocatalysts for the hydrogen/oxygen evolution reaction (HER/OER) holds great promise, but still faces great challenges. Herein, a strategy of doping metal borides with rare earth metal oxides and introducing silicon carbide (SiC) quantum dots has been explored to develop efficient bifunctional electrocatalysts. A novel electrocatalyst consists of SiC quantum dot-decorated CeOx-NiB supported on nickel foam via a one-step mild electroless plating reaction (denoted as CeOx-NiB/SiC@NF). Notably, the modulated electron density of the CeOx-NiB/SiC@NF electrode significantly boosts the electrochemically active surface area and electron transfer, and optimizes the hydrogen/water absorption free energy, which delivers current densities of 50 mA cm-2 and 10 mA cm-2 at overpotentials of only 131 mV and 234 mV for the HER and the OER, respectively. The target electrode requires only 1.43 V to provide 10 mA cm-2 for overall water splitting in 1.0 M KOH. Moreover, the electrode also exhibits good stability and durability at the industrial-grade current density (0.5-1 A cm-2). This work provides a new idea for the development of efficient and durable non-precious metal catalysts.

Synergistic effect of binary metal doping and nanotechnology to boost the light-harvesting properties of rare earth metal oxide

Material scientists are currently focusing on employing photocatalytic materials to detoxify household and industrial waste to tackle rising water pollution problems. Narrow-bandgap materials are more valuable than other photocatalysts due to their visible light-harvesting characteristics. In this research, binary metal-doped cerium oxide (3 mol % Cd, 5 mol % Zn–CeO2 = CZC-1 and 5 mol % Cd, 3 mol % Zn–CeO2 = CZC-2) photocatalysts were successfully prepared through the facile and affordable co-precipitation method. The crystal structure, chemical functionality, morphology, composition, and optical behavior of the as-prepared binary metal-doped cerium oxide samples were explored via advanced physiochemical techniques. UV–Vis spectroscopy revealed that the CZC-2 photocatalyst possessed a relatively lower bandgap (2.15 eV) than the counterpart (CZC-1); hence it could be used as a visible-light triggered catalyst. The binary metal-doped photocatalyst's dye and microbe degradation efficacies were compared using methylene blue and P. Vulgaris, respectively. The CZC-2 photocatalyst showed superior dye degradation activity and mineralized almost 97% dye after 60 min irradiation time. Even after five reuse cycles, the recyclability tests showed that the catalytic efficiency of CZC-2 NPs only dropped by 4.5%. The CZC-2 photocatalyst's high photocatalytic activity and long-term stability show that the CZC-2 nanoarchitecture can be used in practical ways to clean up the environment.

In English

A review of the works of the authors published in the period 2009–2022 and devoted to the study of the properties of nanosized structures containing contacting layers of Fe, Co, Ni, Fe2O3 / REM (Rare Earth Metal) oxide is carried out. The technology for the creation and structural features of these nanostructures are also considered. Physicochemical phenomena in the interface of contacting layers are very multidisciplinary. This is a consequence of their dependence on various conditions, primarily on the modes of technologies for their production and the properties of the initial components. The problem becomes much more complicated when studying magnetic nanostructures. To study effectively the properties of layered nanostructures containing ferromagnetic films, we used magnetic research methods. Using the EPR method, it has been found that between atoms with unfilled f- and d-electron sub-shells, which are part of the contacting layers, an f-d exchange interaction occurs, which orders the magnetic structure of the ferromagnetic layers. Using the method of the anomalous Hall effect, it is shown that the ordering of the magnetic structure leads to an increase in their magnetization. The enhancement of the galvanomagnetic properties in the Fe3O4/REМ оxide/Fe3O4 structures shows that the exchange interaction can have both f-d and d-d character. And this, in turn, leads to an increase in magnetization-dependent properties, such as galvanomagnetic, magneto-optical, and current-voltage properties. This can be used in nanotechnologies to enhance the above properties without energy consumption and the use of amplifying equipment.

Synthesis and characterization of pyrochlore-type lanthanum cerate nanoparticles: Electrochemical determination of antibiotic drug sulfadiazine in biological and environmental samples

In recent eras, antibiotic drugs are essential for humans and the veterinary health system. However, the improper discarding of their residues are simply contaminating the food products and environmental samples. Here, pyrochlore-type lanthanum cerate nanoparticles (LaCe NPs) were prepared through a simple co-precipitation route and used as effective electrocatalyst for the detection of antibiotic drug sulfadiazine (SDZ). The structural investigations of prepared material were carried out using XRD, FT-IR, XPS, SEM, HR-TEM, and EDX along with Elemental mapping analysis, which confirm the good formation of pyrochlore type LaCe in the form of particle-like morphology with well-crystalline nature. A nanosized LaCe revealed superior electrochemical activity towards SDZ owing to the large surface area, facilitating mass and ionic transport and chemical stability phenomena. The as-prepared LaCe NPs demonstrated an excellent electrochemical performance towards SDZ determination with a low LOD (50 nM), a wide dynamic range of 0.04–1525 μM, and an acceptable sensitivity of 1.92 μA μM−1 cm−2. Furthermore, the LaCe NPs/GCE revealed excellent reproducibility, storage stability, and selectivity parameters. Additionally, the proposed sensor achieves a good SDZ recovery in milk and human urine samples. The results strongly suggest that the rare earth metal oxide of lanthanum cerate is an efficient catalyst for portable detection of SDZ.

Electrochemical methods, quantum chemical, and molecular dynamics methods to analyze the corrosion inhibition mechanism of phytic acid/praseodymium composite conversion coating on the AZ31B magnesium alloy

AZ31B has the advantages of high specific strength, low melting point and good toughness, but one of the significant disadvantages is poor corrosion resistance. This topic designed and prepared a corrosion-resistant composite coating of organic polymer phytic acid and rare earth praseodymium salt based on this characteristic. The test results show that the corrosion resistance of the PA/Pr composite coating is more potent than that of a single phytic acid conversion coating, and the surface of the composite layer is clustered particles with good compactness. The conversion coating mainly consists of praseodymium hydroxide, oxide and some phytate compounds. In addition, density functional theory (DFT) was used to analyze the inhibition mechanism of phytic acid; Molecular dynamics (MD) was used to evaluate the adsorption characteristics of phytic acid on metal substrates and rare earth metal oxides.

Improvement in the thermal conductivity and stability of rare-earth metal oxide nanofluids using the stabilizing action of nano CaCO3 in comparison with the stabilizing action of sodium dodecyl sulphate

The stabilizing action of inorganic CaCO3 nanoparticles to increase the thermal conductivity of nanofluids containing nanoparticles of yttrium oxide (Y2O3), zirconium oxide (ZrO2), and yttria-stabilized zirconia (YSZ) prepared from their respective micron size metal oxide precursor through gel combustion method is reported in this work. The nanoparticles obtained through the gel-combustion method after calcination yield nano-size rare earth metal oxide particles. The morphology and composition of the constituents’ nanoparticles thus prepared were explored through XRD, FESEM with EDX, and elemental mapping analysis to confirm the purity and the particle sizes. Thermal conductivities of the nanofluids prepared using the above-mentioned nanoparticles were found to be superior to that of the base fluid, but their stabilities were lesser. Commercially available stabilizers like sodium dodecyl sulphate (SDS) were used to improve the stability but their addition reduces the thermal conductivity of the nanofluids. The nano-CaCO3 particle as a stabilizer provides better stability than SDS was reported. The stability of all the nanofluids was evaluated through the results obtained from zeta potential measurements and the mixture with the highest stability was evaluated. Based on the visual inspection and through UV–vis spectral measurements, the settling ability of the nanoparticles present in the nanofluid was also evaluated. Remarkably, Y2O3 + CaCO3 suspended nanofluid exhibits a commendable thermal conductivity of 29.18 % higher than the base fluid. Such fluids possessing higher stability with good thermal conductivity can be effectively utilized in heat exchanger applications.

Facile synthesis of porous LaFeO3 hexagons for acetone sensing

Acetone is a colourless volatile organic compound naturally occurs in the environment in plants and animals, tobacco smokes, vehicle exhausts, volcanic gases and landfills etc. But getting exposed to acetone can cause irritation in eyes, nose or skin leading to acetone poisoning. Besides, acetone detection is considered as a biomarker in the field of clinical diagnosis for the detection of type-1 diabetics. Therefore, various materials have been tested for a long time for the detection of acetone. LaFeO3, a rare-earth composite metal oxide semiconductor material has shown good chemical stability and physical response towards acetone sensing. In this work, sol–gel method has been used to synthesize LaFeO3 perovskite by taking different molar ratios of lanthanum and iron precursors, using the cationic surfactant Cetyl Tetramethyl Ammonium Bromide (CTAB) as the structure directing agent. X-ray diffraction studies (XRD) and scanning electron microscopy (SEM) were employed to study morphology and composition of the synthesized material. XRD patterns confirms the effective preparation of single-phase perovskite (LaFeO3) without any crystalline impurities like Fe2O3 or La2O3 and the crystallinity nature increases with the increasing temperatures at which the three different samples of LaFeO3 were calcined (700 °C, 800 °C and 900 °C). SEM results confirm that the shape of all the particles in the samples is almost hexagonal and porous in nature. Taking the samples of LaFeO3, calcined at different temperatures, thin films were deposited on glass substrate for the study of their electrical properties by Hall effect characterization and also current–voltage (I-V) characteristic study to understand the principle behind acetone detection for a temperature range of 300 K to 373 K.

Synthesis and characterization of the two magnetic nanocomposites based on polyaniline and doped with cerium and terbium

In this study, two new quadripartite nanocomposites, containing conductive polymer, expanded and functionalized graphene sheets and magnetic parts were synthesized in a simple procedure at room temperature. These compounds were synthesized to investigate the efficacy of contiguity of magnetic oxide, conductive polymer, and rare earth metal oxide. The synthesized compounds were identified by Fourier transform infrared (FTIR), X‐ray diffraction (XRD), field emission scanning electron microscopy (FE‐SEM), and energy‐dispersive X‐ray spectroscopy (EDX) and their electrochemical and magnetic properties were also investigated. The results showed that the presence of cerium oxide instead of terbium oxide reduces the magnetic property and increases the current density.

Influence of Pd and Rare Earth Metals Oxides (Ce, La) as Modifying Additives in the Co,Ni-Oxide Catalyst Compositions on the Process of Methane Oxidation

Influence of Pd and Rare Earth Metals Oxides (Ce, La) as Modifying Additives in the Co,Ni-Oxide Catalyst Compositions on the Process of Methane Oxidation

Facile fabrication of a novel SPME fiber based on silicone sealant/hollow ZnO@CeO2 composite with super-hydrophobicity for the enhanced capture of pesticides from water

Herein, a novel solid phase microextraction (SPME) fiber coating based on silicone sealant/hollow ZnO@CeO2 composite with super-hydrophobicity was designed, which could capture rapidly and determine efficiently-six pesticides combined with high-performance liquid chromatography (HPLC). The synthesis mechanism of ZnO@CeO2 with core–shell structure was discussed. Under the optimized conditions, the developed method showed a wide linear range (0.026–200 µg/L) with good linearity (R2 greater than 0.9988), low detection limits (0.008–0.353 µg/L, S/N = 3), and quantification limits (0.026–1.175 µg/L, S/N = 10) for six pesticides. The relative standard deviations (RSD) of single fiber and different batches of fibers were 0.4–4.8 % and 0.6–5.3 %, respectively. In addition, compared with the commercial SPME fiber, the fiber showed better enrichment ability and extraction efficiency for pesticides, which might be due to the solid π-π accumulation, hydrophobic interaction, abundant adsorption sites, and hydrogen bonding between the coating and the target analyte. Besides, the hollow structure of the composite material, the rare earth metal oxide CeO2 on the surface of the coating, and the silicone sealant all played a crucial role in the extraction process. Finally, the method had been successfully applied to determine the pesticides in real water samples, with the recovery rate ranging from 80.1 % to 108.2 % and RSD < 5.67 %. The experimental results showed that the Ss/ZnO@CeO2 with a hollow core–shell structure had great application potential as a composite coating for solid-phase microextraction.

(Digital Presentation) Synthesis and Promoting Activity of Gd2O3 for Methanol Electro-Oxidation on Pt/C

One of the challenges in electrocatalysis is to design either an efficient non-noble electrocatalyst or improve the electrocatalytic activity of Pt/C by incorporating promoters such as metal oxides, carbides and nitrides. Rare earth metal oxides such as CeO2 have been explored to promote methanol electro-oxidation on Pt/C electrocatalyst. It has been noted that the synthesis method has profound effect on the physiochemical and in turn electrochemical properties of metal oxide promoted Pt/C electrocatalysts. This concept is tested on Gd2O3 promoted Pt/C. Gd2O3 is prepared by precipitation (GdO-PC) method and polymer assisted method (GdO-PL). The oxygen storage capacity (OSC) of this oxide is correlated with the electrochemical activity of Gd2O3-Pt/C. GdO-PC has higher OSC and can release surface oxygen much easier as compared to GdO-PL for methanol electro-oxidation on Pt. The Gd2O3-Pt/C catalysts are prepared with Gd2O3, Vulcan carbon and Pt-salt (equivalent to 20 wt% Pt) using microwave assisted polyol reflux method. The electrocatalytic activity of Gd2O3-Pt/C towards methanol oxidation has been carried out by cyclic voltammetry, CO stripping experiments, chronopotentiometry, and chronoamperometry methods in acidic media. The measurements show that Pt-GdO-PC/C performs better than Pt-(GdO-PL)/C) and commercial Pt/C. This indicates that the synthesis route of Gd2O3 particles is crucial for promoting methanol electro-oxidation. The first principle calculations show that there is a charge transfer from Gd2O3 to Pt. (GdO-PC). It is concluded that higher OSC and charge transfer from Gd2O3 to Pt work in tandem to weaken the Pt-CO bond and oxidise CO to CO2, thus reducing the CO poisoning and enhancing the activity of the oxide promoted electrocatalyst. Figure 1

Thermoluminescence yield of neutron irradiated Gd:Mg-Doped silica glass

The thermoluminescence yield of silica glass doped with Gd2O3 and MgO is investigated as a potential material for neutron dose measurement. The dosimetric materials used herein were prepared via the sol-gel route with concentration of rare earth metal oxides varying from 1 to 10 mol%. Reactor irradiations were made at 750 kW thermal power, producing thermal, epi-thermal and fast neutron fluxes of 5.61 × 1012, 2.51 × 1012, 2.58 × 1012 n/cm−2.s−1, respectively. It has been found that 1 mol% Gd:Mg doped SiO2 exhibits excellent dosimetric response over the entire dose range investigated, obtaining a regression coefficient in excess of 96%. The thermoluminescence (TL) glow curves have been deconvolved, at best fit yielding a total of six peaks, the associated activation energies and frequency factors also being obtained. The results indicate sol-gel Gd:Mg doped SiO2 to offer promising performance as a low-cost passive radiation dosimeter, with utility for both radiotherapy and industrial applications.

Direct Z-scheme mediated SmVO4/UiO-66-NH2 heterojunction nanocomposite for the degradation of antibiotic tetracycline hydrochloride molecules under sunlight.

The use of tetracycline hydrochloride (TCH) for veterinary, human therapy, and agriculture has risen in the past few decades, making it to become one of the most exploited antibiotics. However, TCH residue in the environment is causing issues related to the evolution of antibiotic-resistant bacteria. To address such a problem, photodegradation offers a potential solution to decompose these pollutants in wastewater and thereby mitigates negative environmental impacts. In this context, the research focuses on the use of the rare-earth metal oxide samarium orthovanadate (SmVO4) with nanorod structure, coupled with UiO-66-NH2 for the photocatalytic degradation. Their photocatalytic activity to degrade antibiotic TCH molecules is explored under simulated solar light irradiation. The integration of UiO-66-NH2 with SmVO4 enhanced the light absorption, recombination resistance, carrier lifetime (from 0.382 to 0.411ns) and specific surface area (from 67.17 to 246m2/g) of the composite system as confirmed from multiple analyses. The obtained results further indicated that SmVO4/UiO-66-NH2 nanocomposites could form a direct Z-scheme based heterojunction. Such mechanism of charge transfer leads to the effective degradation of TCH molecules up to 50% in 90min under solar light, while it is degraded only 30% in the case of bare-SmVO4 nanorods. In this work, the incorporation of UiO-66-NH2 positively influences photoelectrochemical properties and improves the overall photoredox properties of SmVO4 for the degradation of complex compounds like antibiotic TCH molecules. Therefore, UiO-66-NH2 can be proposed as an effective material to sensitize the rare-earth based photocatalytic material.

Development of Tungsten Electrode for TIG Welding

Tungsten Inert Gas (TIG) welding process is mostly applied to high alloy steel pipes including stainless steels because of superior welding quality and gap bridge-ability than other welding processes. However, it has poor productivity due to low welding speed and deposition rate. In order to improve TIG welding productivity, high performance TIG welding with higher arc temperature, automation and high deposition rate system including hot wire have been developed. Higher arc temperature and longer welding time damage tungsten electrodes of TIG welding. It causes welding defect such as tungsten inclusion and short replacement cycle of tungsten electrodes. Various types of tungsten electrodes containing rare earth metal oxides (thorium, lanthanum, cerium, etc) were introduced to improve electrode erosion resistance and arc stability. In this study, their operation characteristics, arc starting performance, tip development, and electrode consumption were reviewed.

Composite TiO2 films modified by CeO2 and SiO2 for the photocatalytic removal of water pollutants.

TiO2 particles of high photocatalytic activity immobilised on various substrates usually suffer from low mechanical stability. This can be overcome by the utilisation of an inorganic binder and/or incorporation in a robust hydrophobic matrix based on rare-earth metal oxides (REOs). Furthermore, intrinsic hydrophobicity of REOs may result in an increased affinity of TiO2-REOs composites to non-polar aqueous pollutants. Therefore, in the present work, three methods were used for the fabrication of composite TiO2/CeO2 films for photocatalytic removal of dye Acid Orange 7 and the herbicide monuron, as representing polar and non-polar pollutants, respectively. In the first method, the composition of a paste containing photoactive TiO2 particles and CeCl3 or Ce(NO3)3 as CeO2 precursors was optimised. This paste was deposited on glass by doctor blading. The second method consisted of the deposition of thin layers of CeO2 by spray coating over a particulate TiO2 photocatalyst layer (prepared by drop casting or electrophoresis). Both approaches lead to composite films of similar photoactivity that of the pure TiO2 layer, nevertheless films made by the first approach revealed better mechanical stability. The third method comprised of modifying a particulate TiO2 film by an overlayer based on colloidal SiO2 and tetraethoxysilane serving as binders, TiO2 particles and cerium oxide precursors at varying concentrations. It was found that such an overlayer significantly improved the mechanical properties of the resulting coating. The use of cerium acetylacetonate as a CeO2 precursor showed only a small increase in photocatalytic activity. On the other hand, deposition of SiO2/TiO2 dispersions containing CeO2 nanoparticles resulted in significant improvement in the rate of photocatalytic removal of the herbicide monuron.