High-throughput channel arrays for inhibitor testing: Proof of concept for AA2024-T3

A high-throughput test has been developed for screening aqueous corrosion inhibitors on aluminium AA2024-T3. The method adapts basic microfluidic technology to create multiple channels in polydimethylsiloxane, which allow solutions to flow over the surface of the alloy, causing severe corrosion within hours if no inhibitor is present. In three-channel experiments under various channel conditions, corrosion rates were accelerated up to 15 times when compared to standard immersion tests. In addition, 10-channel experiments were conducted to simultaneously test 10 different inhibitors, and the results were compared visually and to actual corrosion results obtained quantitatively via solution analyses.     

Direct decomposition of nitrogen monoxide over Cu-MFI containing rare-earth elements: Sm and Gd as promoter

The decomposition activities of nitrogen monoxide (NO) were investigated for the copper ion-exchanged ZSM-5 zeolites (Cu-MFI) containing the rare-earth elements: La, Ce, Pr, Nd, Sm, and Gd. It was found that Sm and Gd acted as promoter for NO decomposition over Cu-MFI with 60–70% of the exchange level of copper ion, while the addition of the other rare-earth elements to Cu-MFI showed no positive effect on NO decomposition activity. The introduction of Sm and Gd to Cu-MFI had little influence on the effectiveness of each copper ion for NO adsorption in the MFI zeolite. The presence of Sm and Gd stabilized Cu⁺ as an active center.     

Impact of the A-site rare-earth ions (Ln3+ – Sm3+, Eu3+, Gd3+) on structure and electrical properties of the high entropy LnCr0.2Mn0.2Fe0.2Co0.2Ni0.2O3 perovskites

High entropy perovskites LnCr_0.2Mn_0.2Fe_0.2Co_0.2Ni_0.2O₃ ceramics were produced by solid-state reactions from oxides. The B-site chemical composition was fixed (Cr_0.2Mn_0.2Fe_0.2Co_0.2Ni_0.2) and A-site composition was varied by the rare-earth ions (Ln = Sm³⁺, Eu³⁺ and Gd³⁺). The entropy of B-sublattice mixing was 1.609R J/(mol*K). The dependences of the lattice parameters, microstructure features, and electrical properties were discussed as function of the A-site rare-earth ions. The correlation of the lattice parameters with the nature of the A-site rare earth ions was demonstrated. Impact of the rare-earth ions in A-site on microstructural parameters was observed. Charge conduction mechanisms were discussed in details for a wide range of temperatures.     

Influence of rare-earth doping on the microstructure and conductivity of BaCe0.9Ln0.1O3−δ proton conductors

Doped barium cerates BaCe_0.9Ln_0.1O_3−δ containing earth-rare dopants with different ionic radii, Ln = La, Nd, Sm, Gd, Yb, Tb and Y, have been investigated as candidate materials for fuel cells and other electrochemical applications. The synthesis of these materials was performed using a precursor method based on freeze-drying, which allows a precise control of the homogeneity of the ceramic powders. Dense ceramic pellets were obtained at 1400 °C under identical sintering conditions. The microstructure of the ceramics exhibits similar features with relative density higher than 95% and the grain size decreasing as the ionic radius of the dopant decreases. Impedance spectroscopy measurements were performed to study separately the different contributions to the total conductivity. The bulk, grain boundary and total conductivities depend on the ionic radius of the dopant, reaching a maximum for Gd-doped samples with a value of 0.02 S cm⁻¹ for the total conductivity at 600 °C.     

Tm3+ doped Ga–As–S chalcogenide glasses and fibers

Tm³⁺ doped Ga–As–S chalcogenide glass samples were produced using As₂S₃ pure glass as starting materials. Their photoluminescence properties were characterized and strong emission bands were observed at 1.2 μm (¹H₅ → ³H₆), 1.4 μm (³H₄ → ³F₄) and 1.8 μm (³F₄ → ³H₆) under excitation wavelengths of 698 nm and 800 nm. The thulium and gallium concentrations were optimized to achieve the highest photoluminescence efficiency. From the optimal composition, a Tm³⁺ doped Ga–As–S fiber was drawn and its optical properties were studied.     

Rare-earth oxide–Li0.3Ni0.9Cu0.07Sr0.03O2-δ composites for advanced fuel cells

Recent development on electrolyte-free fuel cell (EFFC) holding the same function with the traditional solid oxide fuel cell (SOFC) but with a much simpler structure has drawn increasing attention. Herein, we report a composite of industrial grade rare-earth precursor for agriculture and Li_0.3Ni_0.9Cu_0.07Sr_0.03O_2-δ (RE–LNCS) for EFFCs. Both structural and electrical properties are investigated on the composite. It reveals that the RE–LNCS possesses a comparable ionic and an electronic conductivities, 0.11 S cm^?1 and 0.20 S cm^?1 at 550 °C, respectively. An excellent power output of 1180 mW cm^?2 has been achieved at 550 °C, which is much better than that of the conventional anode/electrolyte/cathode based SOFCs, only around 360 mW cm^?2 by using ionic conducting rare-earth material as the electrolyte. Engineering large size cells with active area of 25 cm² prepared by tape-casting and hot-pressing gave a power output up to 12 W. This work develops a new functional single layer composite material for EFFCs and further explores the device functions.     

Analysis on three-sublattice model of magnetic properties in rare-earth iron garnets under high magnetic fields

In this paper, based on the molecular field theory, a new and improved three-sublattice model on studying the magnetic properties of ferrimagnetic rare-earth iron garnet in high magnetic fields is introduced. Here, the effective exchange field is described as H_i = λM = λχH_e, where λ is the coefficient associated with the molecular field, χ is the effective magnetic susceptibility, and H_e is external magnetic fields. As is known, the magnetic sublattices in rare-earth iron garnets can be classified three kinds labeled as a, c and d, in our calculations, whose magnetizations are defined as M_a, M_c and M_d, respectively. Then, using this model, the temperature and field dependences of the total magnetization in Dy₃Fe₅O₁₂ (DyIG) are discussed. Meanwhile, the magnetizations of the three kinds of magnetic sublattices are analyzed. Furthermore, our theory suggests that the coefficients α_i associated with λ and χ in DyIG show obvious anisotropic, temperature-dependence and field-dependence characteristics. And, the theoretical calculations exactly fit the experimental data.     

Effects of ultraviolet excitation on the spectroscopic properties of Sm3+ and Tb3+ doped aluminophosphate glasses

Li₂O–BaO–Al₂O₃–La₂O₃–P₂O₅ glasses optically activated with rare earth ions with the 4f⁵, and 4f⁸ electronic configuration (Sm³⁺ and Tb³⁺, respectively) were analyzed by Raman spectroscopy, absorption, excitation photoluminescence, decay curves and temperature dependent photoluminescence. The spectroscopic characteristics of the as-prepared and heat treated samples at temperatures below and above T_g were studied as well as their room temperature photometric properties under ultraviolet excitation. All the doped glasses exhibit typical signatures of the lanthanides in their trivalent charge state. For the samarium doped glass heat treated at 250 °C (<T_g) the Sm²⁺ luminescence was also observed. The analysis of the luminescence efficiency was performed in the interval range of 14 K to room temperature, where the integrated intensity of the luminescence was found to decrease for the Sm³⁺ and Tb³⁺ ions in the studied temperature range. Luminescence decay curves were found to be non-exponential for the ⁴G_5/2 → ⁶H_7/2 and ⁵D₃ → ⁷F₄ transitions of the Sm³⁺ and Tb³⁺ ions, respectively. The results strongly suggest the occurrence of energy transfer processes through cross relaxation phenomena, mediated by dipole–dipole interaction in all the studied samples. The decay of the ⁵D₄ → ⁷F₅ emission of the Tb³⁺ ions was found to be single exponential with a time constant of ∼3.1 ms. Based on the spectroscopic characteristics, models for recombination processes are proposed. The room temperature luminance photometric properties with ultraviolet excitation show that the samarium doped glasses have much lower luminance intensity (around 0.3 Cd/m²) when compared with the 6–7 Cd/m² observed for the terbium doped ones.     

Thermal properties of Er:Li2TiGeO5 ferroelastic ceramics

Micron-grained (2–11 μm), erbium-doped, polycrystalline lithium titanium germinate ceramics were fabricated out of the heat-treated of the presintered samples at a temperature of 970 °C. X-ray diffraction showed a high crystallinity of the synthesized ceramics and confirmed formation of the natisite type structure with the P4/nmm symmetry. FE-SEM analysis revealed that the microstructure of obtained ceramics depends on dopant concentration. The number of pores increases with increasing the dopant dose. The specific heat measurements showed that the temperature of the ferroelastic phase transition was significantly reduced for Li₂TiGeO₅ ceramics (222 K) compared to the bulk (233.5 K). The investigations of the thermal conductivity showed its untypical behavior, proportional to the square of temperature, for a dielectric at low temperatures which could be explained by the microstructure of the samples.     

Microstructure and thermal properties of inflight rare-earth doped thermal barriers prepared by suspension plasma spray

Rare-earth doped yttria-stabilized zirconia (YSZ) coatings with lower thermal conductivity have been fabricated via suspension plasma spray by dissolving rare-earth nitrates into YSZ powder-ethanol suspensions prior to plasma spraying. The effect of dopant concentration and dopant type on properties of the coatings was determined by comparing two coatings containing different concentrations of the same dopant pair (Nd₂O₃/Yb₂O₃), and three coatings having similar concentrations of different dopant pairs (Nd₂O₃/Yb₂O₃, Nd₂O₃/Gd₂O₃, and Gd₂O₃/Yb₂O₃). The porosity content of the coating was found to increase with increased total rare-earth dopant concentration but did not significantly change with dopant pairs. The cross-sectional morphology of every coating displayed a cauliflower-like structure. However, the most heavily doped coating exhibited a larger surface roughness and feathery features in the columnar structures. The thermal conductivity measurement showed that the thermal conductivity decreased with increased Nd₂O₃/Yb₂O₃ concentration. Among coatings containing different dopant pairs, the Gd₂O₃/Yb₂O₃ doped coating exhibited lowest conductivity.