CeCl3 Solutions Research Articles

The Strong Protective Action of Ce3+/F- Combined Treatment on Tooth Enamel and Epithelial Cells.

We studied the toxic effects of cerium and fluoride species on human dental pulp stem cells and epithelial cells of Cercopithecus aethiops as a surrogate for the human oral mucosa. The sequential use of CeCl3 and NH4F solutions in equimolar sub-toxic concentrations enabled the possible toxic effects of individual components to be avoided, ensuring the preservation of the metabolic activity of the cells due to the formation of CeF3 nanoparticles. Cerium fluoride nanoparticles and terbium-doped cerium fluoride nanoparticles exhibited neither cytotoxicity nor genotoxicity to dental pulp stem cells, even at high concentrations (10−4 M). In millimolar concentrations (from 10−5–10−6 M), these nanoparticles significantly increased the expression of genes responsible for the cell cycle, differentiation and proliferation. The formation of cerium fluoride on the surface of the mucous membrane and teeth provided protection against the development of carious lesions, periodontitis, ROS attacks and other inflammatory diseases of the oral cavity. Luminescent CeF3: Tb nanoparticles enabled the visualization of tooth enamel microcracks.

Determination of Lifetime of Ce3+ Luminescence by Time-Correlated Single Photon Counting Method during Sonoluminescence from Aqueous CeCl3 Solution

Determination of Lifetime of Ce3+ Luminescence by Time-Correlated Single Photon Counting Method during Sonoluminescence from Aqueous CeCl3 Solution

A Study of the Localized Ceria Coating Deposition on Fe-Rich Intermetallics in an AlSiFe Cast Alloy.

Corrosion inhibiting conversion coating formation is triggered by the activity of micro-galvanic couples in the microstructure and subsequent local increase in pH at cathodic sites, which in the case of aluminium alloys are usually intermetallics. Ceria coatings are formed spontaneously upon immersion of aluminium alloys in a cerium conversion coating solution, the high pH gradient in the vicinity of intermetallics drives the local precipitation of ceria conversion compounds. Cu-rich intermetallics demonstrate a highly cathodic nature and have shown the local precipitation reaction to occur readily. Fe-rich intermetallics are, however, weaker cathodes and have shown varied extents of localized deposits and are in focus in the current work. Model cast Al-7wt.%Si alloys have been designed with 1 wt.% Fe, solidified at different cooling rates to achieve two different microstructures, with big and small intermetallics, respectively. Upon subjecting the two microstructures to the same conversion coating treatment (immersion in a 0.1 M CeCl3 solution) for a short period of 2 h, preferential heavy deposition on the boundaries of the big intermetallics and light deposition on the small intermetallics was observed. Based on these observations, a mechanism of localized coating initiation at these Fe-rich intermetallic particles (IM) is proposed.

Room-temperature detection of ammonia and formaldehyde gases by LaxBa1−xSnO3−δ (x = 0 and 0.05) screen printed sensors: effect of ceria and ruthenate sensitization

In the present work, gas sensing properties of the screen printed ceria and ruthenate-sensitized BaSnO3 (BSO) with La doping heterostructure sensors towards the detection of ammonia and formaldehyde gases at room temperature were studied. Adhered, porous screen printed films with different morphologies were obtained by depositing the LaxBa1−xSnO3−δ (x = 0 and 0.05) powder particles prepared by the polymerized complex method. Ceria and ruthenate sensitization for screen printed LaxBa1−xSnO3−δ (x = 0.05) film was processed through dip-coating in the 0.03 M aqueous solution of CeCl3 and RuCl3, respectively. La-doped BaSnO3 (LBSO) sensor with smaller crystallites, needle-like morphology and high concentration of oxygen vacancies exhibited superior gas response of 65 and 29 towards 50 ppm of ammonia and formaldehyde gases, respectively. Superabundant sensitization of ceria and ruthenate reduced the oxygen vacancy and structural open porosity in the LBSO sensor; therefore, the ammonia gas response was decreased from 65 to 14 and 3, respectively, whereas the formaldehyde gas response was reduced to less than 1/6th times the LBSO sensor. Limit of detection of LBSO sensors was estimated to be ~ 1 and ~ 2 ppm against ammonia and formaldehyde, respectively. The presence of fluorite structured phase ceria with high oxygen atoms storage capacity facilitates the rapid oxidization of analyte gases and caused the expeditious response (75 s) and recovery (60 s) in CeOx-sensitized LBSO sensor. This study might give a new insight into the development of doped and sensitized BSO-based gas sensors operating at ambient conditions.

Co3O4/CeO2/C As Electrocatalyst for Ethylene Glycol Oxidation Reaction

In recent decades, alkaline direct alcohol fuel cells have been interested due to their advantages over hydrogen fuel cell. Alcohols such as methanol and ethanol are the most common types of fuel used in direct liquid-feed fuel cells however alternative alcohols are increasingly being investigated. One of the choices for alkaline alcohol fuel cell is ethylene glycol. Ethylene glycol in an alkaline medium generates, as intermediates, oxalates, glyoxylate, glycolate, glycolaldehyde, glyoxal and carbon dioxide and it is considered an energy carrier for fuel cells. The importance of this fuel is attributed to several factors: low molecular weight, biomass origin, high energy density, high boiling point and lower toxicity than methanol.One more challenge is to find the most efficient electrocatalysts for various fuel oxidation reaction which could replace platinum in fuel cell anode materials in relation to its limited resources and high price.Lately, the most research is based on the development of different, new, rare earth metals and metal oxides compositions, the improvement of known materials such as carbon with various additives with the aim to reduce or completely refuse of noble metal and to find low cost, higher efficient and great performance catalysts.In this study, the Co3O4 was deposited onto the CeO2/C substrates prepared by two different ways. The substrates were prepared as follow: a) dry powder of CeO2 was mixed with carbon powder (mass ratio being 1:1) in a 2-propanol solution by ultrasonication for 30 min with further drying of the mixture (CeO2/C-1); b) CeCO3 were precipitated onto the carbon surface using the appropriate concentrations of CeCl3 and Na2CO3 solutions with stirring on a magnetic stirrer, followed by drying the mixture (CeO2/C-2). Then Co3O4 was deposited onto the CeO2/C-1 and CeO2/C-2 substrates using microwave irradiation and β–cyclodextrin as reducing agent. The synthesized Co3O4/CeO2/C-1 and Co3O4/CeO2/C-2 catalysts were characterized by Inductively Coupled Plasma Optical Emission Spectroscopy, Field Emission Scanning Electron Microscopy, Transmission Electron Microscopy and X-ray Diffraction. Electrocatalytic activity of the prepared catalysts was evaluated towards ethylene glycol oxidation reaction in an alkaline medium using cyclic voltammetry and chrono-techniques.It has been found, that the Co3O4 supported catalysts showed higher electrocatalytic activity for the ethylene glycol oxidation reaction than the pure CeO2/C substrates. Moreover, the preparation way of the substrate has had the influence on the electrocatalytic activity of prepared catalysts. It has been found that Co3O4/CeO2/C-2 catalyst where CeO2/C substrate was obtained from CeCl3 salt solution showed higher electrocatalytic activity towards ethylene glycol oxidation reaction than Co3O4/CeO2/C-1 catalyst where CeO2 was directly mixed with carbon powder.

New sonochemiluminescence involving solvated electron in Ce(III)/Ce(IV) solutions

The moving single-bubble sonoluminescence of Ce3+ in water and ethylene glycol solutions of CeCl3 and (NH4)2Ce(NO3)6 was studied. As found, a significant part of intensity of the luminescence (100% with cerium concentration less than 10–4 M) is due to the sonochemiluminescence. A key reaction of sonochemiluminescence is the Ce4+ reduction by a solvated (or hydrated in water) electron: Ce4+ + es (eaq) → *Ce3+. Solvated electrons are formed in a solution via electrons ejection from a low-temperature plasma periodically generated in deformable moving bubble at acoustic vibrations. Reactions of heterolytic dissociation of solvents make up the source of electrons in the plasma. In aqueous CeCl3 solutions, the Ce4+ ion is formed at the oxidation of Ce3+ by OH radical. The latter species originates from homolytic dissociation of water in the plasma of the bubble, also penetrating from the moving bubble into the solution. The sonochemiluminescence in cerium trichloride solutions are quenched by the Br− (acceptor of OH) and H+ ions (acceptor of eaq). In water and ethylene glycol solutions of (NH4)2Ce(NO3)6, the sonochemiluminescence also quenched by the H+ ion. The sonochemiluminescence in CeCl3 solutions is registered at [Ce3+] ≥ 10–5 M. Then the sonochemiluminescence intensity increases with the cerium ion concentration and reaches the saturation plateau at 10–2 M. It was shown that sonophotoluminescence (re-emission of light of bubble plasma emitters by cerium ions) also contributes to the luminescence of Ce3+ in solutions with [Ce3+] ≥ 10–4 M. If the cerium concentration is more than 10–2 M, a third source contributes to luminescence, viz., the collisional excitation of Ce3+ ions penetrating into the moving bubble.

Ce(OH)2Cl and lanthanide-substituted variants as precursors to redox-active CeO2 materials.

The cerium(iii) hydroxide chloride Ce(OH)2Cl crystallises directly as a polycrystalline powder from a solution of CeCl3·7H2O in poly(ethylene) glycol (Mn = 400) heated at 240 °C and is found to be isostructural with La(OH)2Cl, as determined from high-resolution synchrotron powder X-ray diffraction (P21/m, a = 6.2868(2) Å, b = 3.94950(3) Å, c = 6.8740(3) Å, β = 113.5120(5)°). Replacement of a proportion of the cerium chloride in synthesis by a second lanthanide chloride yields a set of materials Ce1-xLnx(OH)2Cl for Ln = La, Pr, Gd, Tb. For La the maximum value of x is 0.2, with an isotropic expansion of the unit cell, but for the other lanthanides a wider composition range is possible, and the lattice parameters show an isotropic contraction with increasing x. Thermal decomposition of the hydroxide chlorides at 700 °C yields mixed-oxides Ce1-xLnxO2-δ that all have cubic fluorite structures with either expanded (Ln = La, Gd) or contracted (Ln = Pr, Tb) unit cells compared to CeO2. Scanning electron microscopy shows a shape memory effect in crystal morphology upon decomposition, with clusters of anisotropic sub-micron crystallites being seen in the precursor and oxide products. The Pr- and Tb-substituted oxides contain the substituent in a mixture of +3 and +4 oxidation states, as seen by X-ray absorption near edge structure spectroscopy at the lanthanide LIII edges. The mixed oxide materials are examined using temperature programmed reduction in 10%H2 in N2, which reveals redox properties suitable for heterogeneous catalysis, with the Pr-substituted materials showing the greatest reducibility at lower temperature.

The Effect of Deposition Parameters on the Properties of CeCl3 and LaCl3 Conversion Coatings Deposited on Three Al-Based Substrates

Cerium and lanthanum conversion coatings were deposited from solution of CeCl3 and LaCl3 salts on three aluminum-based substrates: Al, AA2024-T3, and AA7075-T6 to investigate the effect of conversion temperature, conversion time, and addition of hydrogen peroxide. Coatings prepared under different conditions were then analyzed in terms of corrosion properties in 0.1 M NaCl, morphology, topography, and composition. Morphology and composition of the coatings were analyzed using scanning electron microscopy with energy dispersive x-ray spectrometry and x-ray photoelectron spectroscopy. Corrosion resistance, morphology, composition, and homogeneity of coatings were largely dependent on parameters of conversion treatment and type of substrates. Most corrosion resistants were Ce-based coatings produced at 60°C for 1 h in a bath containing CeCl3 and H2O2. La-based coating did not reach comparative resistance when deposited under the same conditions. Morphology of coatings ranged between individual deposits to thick, cracked coatings with nodular morphology. Ce-based coatings predominantly contained Ce(IV) hydroxide when formed with added H2O2. La-based coatings contained La(III) hydroxide mixed with Al(III) hydroxide.

Preparation of oxygen vacancy-controllable CeO2 by electrotransformation of a CeCl3 solution and its oxidation mechanism

CeO2 was successfully prepared by electrotransformation of CeCl3 solution in previous work. In this work, the oxidation mechanism of Ce3+ was determined by cyclic voltammetry and a potential-pH diagram, which indicated that Ce3+ was oxidized by oxygen during the electrotransformation, and the important role of the oxygen content in solution was confirmed. Thus, the influence of atmosphere (air/argon/oxygen) on CeO2 preparation was investigated by adjusting the gas type and flow rate. XRD patterns demonstrated the cubic fluorite structure and grain size of CeO2. With an increase in the gas flow rate, the grain size decreased, but the particle size increased. This result indicated that the smaller grains contained more lattice defects and higher surface energy, so the grains preferred to agglomerate together, forming larger particles. XPS spectra proved that Ce3+ and Ce4+ both existed in the CeO2 samples. Raman scattering revealed that more oxygen vacancies could be produced with an argon atmosphere and high gas flow.

Recovery of Rare Earth Element Cerium from Spent Automotive Exhaust Catalysts Using a Novel Method

This study developed a new method for the recovery of the rare earth element cerium (Ce) from spent automotive exhaust catalysts. The content of Ce was 5.31% (wt%) in the spent catalyst sample. Sulfuric acid (2 mol/L) and hydrofluoric acid (0.9 mol/L) were used as a mixed acid leaching agent to successfully decompose the ceria-zirconia solid solution of the catalyst, which is resistant to dissolve in acids. The leaching efficiency of Ce reached 99.25% under the optimal conditions of a catalyst particle size range of 76–96 µm, an S/L of 1/10 (w/v), a leaching temperature of 70 °C, a leaching time of 4 h, and 200 rpm. The Al3+ that was leached from the catalyst scrubbed F− in the leachate, allowing the separate extraction of Ce4+ using di-2-ethylhexyl phosphoric acid (D2EHPA) in sulfuric acid media. Potassium permanganate (KMnO4) with a concentration of 20% was added during the extraction to increase the oxidation rate of Ce and to diminish the reduction effect of the organic solution. The results indicated that 87.23% of Ce4+ was extracted into the D2EHPA-kerosene solution with a concentration of 0.8 mol/L D2EHPA, a stoichiometric quantity of KMnO4 of 175%, and contact for 15 min at room temperature. Reduction stripping was performed using hydrochloric acid (2 mol/L) with 3% H2O2 to obtain the CeCl3 solution. The recovered amount of Ce was 85.54% with high purity from the spent automotive exhaust catalyst.

Corrosion resistance of phytic acid / Ce (III) nanocomposite coating with superhydrophobicity on magnesium

By alternative immersion into the aqueous solutions of phytic acid (PA) and CeCl3 for n cycles, a nanocomposite coating coded as (PA/Ce)n was fabricated on the magnesium substrate. The Ce3+ ions were supposed to coordinate with the phosphate groups of the PA molecules and the (PA/Ce)n coatings adhered to the substrate firmly (5B according to the ASTM D 3359 method). Compared with the PA coating, the Ce3+ ions enhanced the corrosion resistance of the PA/Ce nanocomposite coating. To further improve the corrosion resistance, the (PA/Ce)n coatings were immersed into the ethanol solution of hexadecyltrimethoxysilane (HDMS) and followed by heating in air. The so-obtained sample coded as Mg-H2O-(PA/Ce)n-HDMS was superhydrophobic and possessed much better corrosion resistance as compared with the Mg-H2O-(PA/Ce)n sample due to the retained thin layer of air at the solid/water interface in the NaCl aqueous solution. For four cycles, the Mg-H2O-(PA/Ce)4-HDMS sample showed the most excellent superhydrophobicity with a contact angle of 167.3 ± 2.1° and a sliding angle of 2.7 ± 0.8° due to its hierarchical surface morphology. Moreover, for four cycles, the retained air was most durable and remained intact after immersion for 80 h; consequently, the corrosion resistance of the Mg-H2O-(PA/Ce)4-HDMS sample was found the best. In one word, the corrosion resistance of PA to the Mg substrate was improved by incorporating with Ce3+ ions and further modifying by HDMS molecules. The present study provided a new conversion coating by combining the synergistic anti-corrosion effect of PA, Ce3+ ions, and the surface superhydrophobicity.

Inhibition of hydrogen production reactions in the wet dust removal system using CeCl3 solutions

For treatment of aluminum dust, a wet dust removal system has been used worldwide. During treatment, aluminum dust is inhaled into a water tank of the dust collector. As hydrogen production reactions are likely to take place in the water tank, there exists a great risk of fire or explosion accidents associated with the wet dust removal system. Based on field research and laboratory experiments, Hydrogen Inhibition Method (HIM) by using CeCl3 solutions was proved capable of inhibiting reactions between aluminum dust and water. When the concentration of CeCl3 solutions reached 6.02 g/L, there was basically no hydrogen gas produced. SEM, EDS and XPS characterizations were used to assess the aluminum particles before and after being reacted with water or CeCl3 solutions, respectively. Shrinking core model was utilized to identify the corresponding chemical reaction kinetics. Additionally, a physicochemical mechanism was established to explain these phenomena.

Morphology‐Controllable Preparation of CeO2 Materials for CO2 Adsorption

AbstractThree morphology controllable CeO2 crystals were successfully synthesized via the thermal decomposition of CeCO3OH precursors, which was newly prepared on the basis of a simple and template‐free hydrothermal reaction between CeCl3 solution and a CO2‐storage material (CO2SM). In the formation processes of three CeCO3OH precursors, the CO2SM could be newly used as raw material and structural director. Meanwhile, the results presented the wider pH values (5.24‐8.35) for isoelectric point of CeCO3OH precursors. After the CeCO3OH precursors were isolated, the filtrate could be recycled to absorb CO2 again and prepare CeCO3OH precursors with two special polymorphs. Three as‐prepared CeO2 crystals by annealing three CeCO3OH precursors at 500 °C for 4 h showed the maximum adsorption amounts of 23.5, 18.7 and 20.5 mg/g for 8% CO2/N2 mixture. As a result, this work provided the wider pH values for isoelectric point of CeCO3OH precursors and a simple method for the preparation of CeO2 crystals with a short time and CO2 adsorption properties.

Cerium Chloride Application Promotes Wound Healing and Cell Proliferation in Human Foreskin Fibroblasts.

This study investigated the effect of cerium chloride (CeCl3) on cell migration and gene expression of human foreskin fibroblasts (HFF). HFF were exposed to three different CeCl3 solutions (1%, 5% and 10%, w/v %) for three different time durations (1, 5 and 10 min). 72 h after exposure to CeCl3, cell viability was assessed by MTT test. A scratch-wounded assay determined the cell migration and the width of the wound, measured at 24 h. Gene expression patterns for cyclins B1, D1 and E1 were analyzed by RT-PCR (p < 0.05, t-test). The viability proliferation increased at 1- and 5-min exposures for all CeCl3 concentrations, in contrast to no treatment (p < 0.05 at 24 h). No influence of CeCl3 was found after 10 min. The scratch assay showed increased cell migration up to 60% at 1 and 5 min after 24 h at 5% and 10%. Cyclin B1, D1 and E1 all showed upregulation, confirming an increase in cell proliferation. This study demonstrates that exposure time and concentration of CeCl3 may have a positive effect on fibroblast viability and migration. Application of CeCl3 may be beneficial as a cell-stimulating agent leading to therapeutic tissue fibrosis or more resistant tissue around teeth, when warranted, during different periodontal therapies.

TH-AB-207A-07: Radiation Dose Simulation for a Newly Proposed Dynamic Bowtie Filters for CT Using Fast Monte Carlo Methods

Purpose: Dynamic bowtie filter is an innovative design capable of modulating the X-ray and balancing the flux in the detectors, and it introduces a new way of patient-specific CT scan optimizations. This study demonstrates the feasibility of performing fast Monte Carlo dose calculation for a type of dynamic bowtie filter for cone-beam CT (Liu et al. 2014 9(7) PloS one) using MIC coprocessors. Methods: The dynamic bowtie filter in question consists of a highly attenuating bowtie component (HB) and a weakly attenuating bowtie (WB). The HB is filled with CeCl3 solution and its surface is defined by a transcendental equation. The WB is an elliptical cylinder filled with air and immersed in the HB. As the scanner rotates, the orientation of WB remains the same with the static patient. In our Monte Carlo simulation, the HB was approximated by 576 boxes. The phantom was a voxelized elliptical cylinder composed of PMMA and surrounded by air (44cm×44cm×40cm, 1000×1000×1 voxels). The dose to the PMMA phantom was tallied with 0.15% statistical uncertainty under 100 kVp source. Two Monte Carlo codes ARCHER and MCNP-6.1 were compared. Both used double-precision. Compiler flags that may trade accuracy for speed were avoided. Results: The wall time of the simulation was 25.4 seconds by ARCHER on a 5110P MIC, 40 seconds on a X5650 CPU, and 523 seconds by the multithreaded MCNP on the same CPU. The high performance of ARCHER is attributed to the parameterized geometry and vectorization of the program hotspots. Conclusion: The dynamic bowtie filter modeled in this study is able to effectively reduce the dynamic range of the detected signals for the photon-counting detectors. With appropriate software optimization methods, the accelerator-based (MIC and GPU) Monte Carlo dose engines have shown good performance and can contribute to patient-specific CT scan optimizations.

Influence of buffering on the spontaneous deposition of cerium conversion coatings for corrosion protection of AA2024-T3 aluminum alloy

Cerium-based conversion coatings were spontaneously deposited on AA2024-T3 alloy at 60 °C using buffered and non-buffered CeCl3 solutions in the presence of H2O2. Malonic acid or amino-acetic acid (glycine) was used as buffering additives. The deposition process and the properties of the coatings obtained were followed by linear voltammetry and electrochemical impedance spectroscopy. The surface morphology was studied by scanning electron microscopy. It was found that buffering complicates the conversion process and hampers the deposition rate. The coatings deposited using buffered baths had lower barrier ability and corrosion durability in 3.5 % NaCl corrosive medium compared to those deposited in the absence of buffers.

Electrochemistry of CeCl3 in molten LiCl-KCl eutectic

The electrochemical properties of CeCl3, dissolved in LiCl-KCl eutectic melt, were investigated by electrochemical techniques, such as cyclic voltammetry and square wave voltammetry on Mo electrode. It was shown that Ce(III) is reduced to Ce(0) based on a three-step mechanism. In a temperature range of 833–923 K, the diffusion coefficient of Ce(III) is lgD Ce(III)= −2.49–1704/T determined by means of the Berzins-Delahay equation with two different expressions under reversible and irreversible conditions. The apparent standard potential of a Ce(III)/Ce(0) red-ox system is $E_{Ce^{3 + } /Ce^0 }^{0*} $ =3.551+0.0006132T(K) vs. Cl2/Cl−. Some thermochemical properties of CeCl3 solutions were also derived from the electrochemical measurements, such as the enthalpy, entropy, Gibbs free energies and the activity coefficients of Ce(III). The Gibbs free energy of a dilute solution of CeCl3 in this system was determined to be $\Delta G_{CeCl_3 }^{0*} $ /(kJ·mol−1)= −1027.9+0.178T(K) And the activity coefficients, $\gamma _{CeCl_3 } $ , range between (7.78–9.14)×10−3. Furthermore, the standard rate constant of kinetic reaction was calculated to be (4.94–9.72)×10−3 cm2/s and the reaction was regarded as a quasi-reversible reaction under the present experimental conditions at 833 K.

Volta potential of clad AA2024 aluminium after exposure to CeCl3 solution

AA2024 clad with AA1050 was immersed in CeCl3 solution to promote deposition of cerium species. The deposition occurs on the entire sample surface for the alkaline etched substrate, while it is very limited for the degreased substrate. The surface potential (Volta potential) was investigated by scanning Kelvin probe force microscopy after different immersion times in CeCl3 solution. The preferential deposition of Ce compounds at Al–Fe intermetallic sites progressively reduces their Volta potential difference relative to the matrix in the alkaline etched substrate. This reduces the susceptibility to localized attack of the intermetallics as proven by potentiodynamic polarization measurements.

Luminescence properties, centroid shift and energy transfer of Ce3+ in aqueous chloride solutions

This paper focuses upon three themes: all related to aqueous cerium chloride solutions.First, the features in the absorption spectra of CeCl3 solutions do not shift noticeably with concentration and are at similar energies to bands in the solid-state absorption spectrum of Ce(H2O)93+, with the exception of the weak band at 297nm which is due to Ce(H2O)83+. The broad emission band in solution is only due to [Ce(H2O)83+]⁎ and the emission quenches at concentrations >0.06M. Bands in the excitation spectra of aqueous CeCl3 solutions apparently change position with increasing concentration, due to absorption by Ce(H2O)93+ which does not contribute to emission. At concentrations above 1M, there is total extinction of incident radiation for wavelengths shorter than 310nm.Second, this system is chosen to illustrate the revised calculation of centroid shift, by taking into account the vibronic nature of spectral features, in contrast with the pure electronic transition of the free ion. Similar calculations are applicable to other Ce3+ systems.Thirdly, excitation spectra are employed to demonstrate the energy transfer occurring from Ce3+ to Tb3+ and Eu3+ in aqueous chloride solutions, which is an unusual energy transfer, occurring from 5d to 4f states and between hydrated lanthanide ions in solution.

Localized corrosion inhibition by cerium species on clad AA2024 aluminium alloy investigated by means of electrochemical micro-cell

AA2024 clad with AA1050 was immersed in CeCl3 solutions under aerated and O2 saturated conditions to promote the deposition of cerium species. The Ce deposition occurs on the entire sample surface. The amount of Ce detected on the intermetallics is larger than on the matrix. The deposition is activated by alkaline etch of the substrate. The breakdown potential in potentiodynamic polarization curves becomes more positive due to the Ce deposition both on the areas containing Fe-rich intermetallics and on the matrix. Characterization by micro-cell indicates that the overall electrochemical behaviour is improved by the Ce deposition.