La2O3 Content Research Articles

Influence of La2O3 content on the structural, mechanical, and radiation-shielding properties of sodium fluoro lead barium borate glasses

The techniques of melt-quenching were used to manufacture 53B2O3–2NaF–27PbO– $$(20-x)$$ BaO– $$x$$ La2O3 $$(0\le x \ge 15)$$ glass system. To check the status of these samples, the XRD diffractometer procedure was used. The molar volume of the glass system is decreased while density is increased. The current glass sample's mechanical properties depend on the glass structure. Ultrasonic velocity and elastic modulus (experimental and theoretical) of glass samples were observed to be increased. FT-IR analysis shows that with the increase of La2O3 increases the changes of BO3 to BO4 and increases the degree of glass connectivity and the structural units of (BO3/2 F)− tetrahedra are formed. It has been noted that the MAC values of glass samples are decreased to 1 meV, apart from a small increase at 0.1 meV. At low energy, this significant decline and small peak are directly linked to the current photoelectric effect. The sample with the highest La2O3 content is owned the MAC's greatest values. It has been noted that the (HVL) and (TVL) increase with the increase in the photon energy and La2O3 content rendering to the achieved results. It has been noted that the Zeff has the largest values at lower energy and at lowering concentration of La2O3 content. It has been noted that EABFs and EBFs have originally lower values at low energy levels, because the photoelectric effect dominates and BaO is replaced by La2O3.

Oxidation behavior of different La2O3-content modified SiC ceramic at 1700 °C

Silicon carbide (SiC) ceramic specimens doped with different contents of La2O3 were prepared by hot pressing process to investigate the influence of La2O3 content on their anti-oxidation performance at 1700 °C. The result of the isothermal oxidation test reveals that La2O3-doped SiC ceramic showed better anti-oxidation performance than pure SiC ceramic, and the anti-oxidation performance of La2O3-doped SiC ceramic decreased as the content of La2O3 increased. Mulliken population analysis based on first-principle calculation indicates that the strength of Si–O bond was enhanced by adding a small amount of La dopant (~5 wt%) into SiO2, which is favorable to the thermal stability of the oxide scales. The coexistence of SiO2 and La2Si2O7 under a certain ratio makes the glass layer have proper viscosity to form a compact and smooth protective layer, thus leading to a better anti-oxidation performance at 1700 °C. However, the SiC ceramic doped with excessive La2O3 (10–15 wt%) showed poor anti-oxidation performance owing to the defective glass layer and the destruction of SiO2 structure. This work is beneficial to select which La2O3 content is suitable for the anti-oxidation SiC ceramic coating at 1700 °C.

X‐ray shielding parameters of lanthanum oxide added waste soda‐lime glass

Besides various materials, glass becomes very important, as it has started to be used in many applications. Thus, their radiation shielding properties should be determined for safely using in critical applications such as for medical purposes With this in mind, the present study investigated the radiation shielding parameters of waste soda‐lime (SLS) containing varying amounts of lanthanum oxide (La2O3). The La2O3 content was added as 0.005, 0.05 and 0.5 in wt% into waste SLS glass, and four different glass specimens (La‐0, La‐0.005, La‐0.05, and La‐0.5) were produced via conventional melting technique. The linear attenuation coefficient for glass samples was measured in the photon energies of 511,835 and 1,275 keV and the results were compared with the calculation done by XCOM. One can conclude that adding lanthanum oxide to waste glass is an effective way to improve radiation shielding properties of glass. That is, the sample of La‐0.5 could provide a higher linear attenuation coefficient while lower half‐value thicknesses. Further, the findings obtained both in calculation and experimental showed a good agreement for all types of glass and also for all energies.

Rare-earth oxides modified Mg-Al layered double oxides for the enhanced adsorption-photocatalytic activity

Mg-Al layered double oxides (LDO) nanosheets were modified by rare-earth oxides such as La2O3, Sm2O3, and Er2O3 (M/Mg-Al, M = La, Sm, and Er) via a one-pot hydrothermal route for the solar-light induced adsorption-photocatalytic degradation of tetracycline hydrochloride (TCH). These rare-earth oxides can greatly enhance the adsorption-photocatalytic activity of Mg-Al based composites, especially La2O3. It’s attributed to the efficient adsorption of vacant sites and the rapid transfer and separation of charge carriers at the junction interface. The La2O3 content, pH value, and inorganic ions intensively affect the adsorption-photocatalytic performance of La/Mg-Al. The optimal 2-La/Mg-Al with the La2O3 content of 4.35 % exhibits the best removal efficiency of TCH and the excellent photocatalytic durability. The removal efficiency of TCH (100 mg L−1) is 99.87 % within 110 min, and reduces to 95.88 % after five cycle times. The adsorption isotherms and kinetic behaviors of M/Mg-Al (M = La, Sm, and Er) for TCH removal are well described by Langmuir isotherm and second-order model, respectively. The active radicals such as OH and O2− are responsible for the solar light driven photocatalytic degradation of TCH.

CO2 Assisted Oxidative Dehydrogenation of Propane to Propylene over Fluidizable MoO3/La2O3-γAl2O3 Catalysts

Abstract This study investigated the catalytic performance of a novel fluidizable MoO3 supported on La2O3-γAl2O3 composite for oxidative dehydrogenation (ODH) of propane to propylene with and without CO2. The La2O3-γAl2O3 composites were synthesized by a coprecipitation method, while the active MoO3 was deposited by an incipient wetness impregnation approach. The incorporation of La2O3 controlled both the acidity and reducibility of the catalysts, as revealed by NH3-TPD and H2-TPR analysis, respectively. The N2 adsorption/desorption isotherms analysis indicated the mesoporous pore size distribution of the catalysts. The ODH of propane experiments were developed in a fluidized CREC Riser Simulator by feeding propane with or without CO2. The performance of the synthesized catalysts was found to be a function of the La2O3 content of the support. In general, the propane conversion declined slightly, while propylene selectivity increased with the increasing La2O3 content. It was hypothesized that the presence of basic La2O3 reduced the acidity and the non-selective sites of γ-Al2O3, which were responsible for deep oxidation of propylene and propane. Among the studied catalysts, MoO3/La2O3-γAl2O31:2 displayed the highest propylene yield of 28.2 % at 600 ℃ in the absence of CO2. However, a superior yield of 35.2% was achieved over the same catalyst by the introduction of CO2-admixture in the feed at 550 ℃.

Metallurgical Effect of Rare-Earth Lanthanum Fluoride and Boride in the Composite Coating of Wires in the Arc Welding of Bainitic-Martensitic and Austenitic Steel

For arc welding of high-strength and cold-resistant steels, the author developed an advanced design of steel wire with a micro-composite coating of a nickel matrix and nanoparticles of LaF3 and LaB6, which improves the metallurgical influence of rare-earth elements (REE) and forms refractory sulphides and oxides of REE, as well as boron nitride. The addition of 0.1–0.3 wt% La in the weld pool leads to an increase in the content of the refractory compounds La2O3, LaO2, and LaS, and to the reduction in the content of the low-melting and brittle oxides and sulphides SiO2, SiO, MnO, MnS, and SiS. The use of steel wire with the composite coating of LaF3 and LaB6 allows for microstructural refinement when welding S960QL bainitic-martensitic steel and X70 API bainitic steel, and increases the impact toughness of the welds by 1.17–1.6 times.

Dielectric Properties and AC Conductivity of Chitosan-La2O3 Nanocomposite

In this study, polymeric films based on chitosan (CS) doped with Lanthanum oxide nanoparticles at different weight percentages (5, 10, 15, and 20% La2O3/CS) were prepared using the simple solution cast transformation. The dielectric constant increases with increasing the La2O3 content, and this could be attributed to the induced defects, as a result more dipoles are produced in the polymer matrix. Also, the values of Z′ and Z″ increase with La contents. On other hand, we noticed that the plot of the normalized-imaginary electric modulus versus the frequency shows a clear peak at high frequency for all samples. This peak is associated with ionic conduction. The AC conductivity increased by increasing the La2O3 content. Furthermore, AC conductivity increases with frequency because the absorbed energy from the electric field can increase the number of charge carriers that are participating in the electric conduction. Moreover, the values of the universal exponents were larger than the unity and increase with increasing temperatures which means that the conduction process may be pertinent to reorientational (or localized) mechanism.

Enhancement of the laser emission efficiency of Yb:Y2O3 ceramics via multi-step sintering method fabrication

Highly transparent 5.0 at.% Yb:Y2O3 ceramics were successfully fabricated by using an optimal content of La2O3 and ZrO2 sintering additives and multi-step sintering method. The sintering process of the ceramics was based on a combination of two-step sintering in air followed by vacuum sintering. In-line optical transmission reached 78.5% at 1100 nm and 80% at 2000 nm. The absorption cross-section at 978 nm and the stimulated emission cross-section at 1032 nm were determined to be 2.23 × 10−20 cm2 and 1.42 × 10−20 cm2, respectively. Laser emission at 1.03 μm with a high slope efficiency of 33% was obtained from a 1.5 mm thick Yb:Y2O3 uncoated ceramic medium under quasi-continuous wave pumping at 971 nm with a fiber-coupled diode laser.

Effects of Lanthanum Incorporation on Stability, Acidity and Catalytic Performance of Y Zeolites

A better understanding of the roles of rare earth (RE) in heterogeneous catalysts is crucial for improving the properties of catalysts in petro-chemical industry. Fluid catalytic cracking (FCC) catalysts containing RE-incorporated Y zeolites with excellent stability and activity are continuously used to improve the conversion of heavy oil into transportation fuels. In this paper, the effect mechanism of Lanthanum (La) on stability and acidity of Y zeolites are elucidated in conjunction with their influences on catalytic performance. The improvement on stability of La-incorporated Y zeolites can be attributed to the La incorporation which bonds strongly with framework O2 and O3 atoms and strengthens the interaction between framework Al and its neighbouring O atoms. It is the enhanced stability restrains the release of framework Al and the formation of extra-framework Al, hence leads to a decrease of total L acid amount and an increase of total B acid amount, especially a clear increase in medium strength B acid amount (with 31P NMR/TMPO chemical shifts at 62 and 58) and a significant decrease in strong B acid amount (with 31P NMR/TMPO chemical shifts at 70 and 65) with the incorporation of La into Y zeolites. However, the total acid amount decreases significantly when La2O3 content is high. The increase of B acid amount and improved stability of LaHY zeolites, boost the conversion ability and isomerization ability of heavy oil, while resulting in poor olefins selectivity and coke selectivity caused by the enhancement of hydrogen transfer reactions. Therefore, Y zeolite containing appropriate La2O3 content should be considered to enhance heavy oil cracking ability while boosting light olefins production and optimizing coke selectivity.

The effects of La2O3 addition on mechanical and nuclear shielding properties for zinc borate glasses using Monte Carlo simulation

Effects of La2O3 addition on the mechanical and nuclear shielding properties of zinc borate glasses with the form (55-x)ZnO-45B2O3-xLa2O3: x = 0, 2, 5, and 10 mol% labelled as LZB1-LZB4, respectively were investigated. Bond compression (BC) model and Geant4 simulation code were utilized to achieve these objectives. The value of the bulk modulus (KBC) decreased from 153.116 GPa for LZB1 glass sample to 136.662 GPa for LZB4 glass sample corresponding to an increment of La2O3 from 0 to 10 mol%. Longitudinal modulus (LBC) decreased from 280.729 GPa to 249.610 GPa and the Young's modulus (EBC) also decreased from 238.11 GPa to 211.03 GPa for LZB1 to LZB4 glasses. Poisson's ratio (σBC) increased from 0.240 to 0.243 with the increase of La3+ ions in the LZB-glasses. Hardness of LZB-glasses was decreased from 16.578 GPa to 14.572 Gpa. The nuclear radiation shielding properties of the LZBx glasses were explored by utilizing Geant4 Monte Carlo simulations and different theoretical approaches such as ESTAR and XCOM platforms. The obtained values of mass attenuation (MAC) increased in the glasses in the order: LZB1< LZB2 < LZB3 < LZB4. The maximum values of MAC obtained at energy of 15 keV were 39.157, 40.117, 41.356 and 43.019 cm2g-1 for LZB1, LZB2, LZB3, and LZB4 respectively. Calculated values of fast and thermal neutron macroscopic cross sections varied from 0.1143 to 0.1156 cm-1 and 1.9378 to 27,786 cm-1 as La2O3 varied from 0 to 10 mol% in the glasses. Also, the electron attenuation capacity of the LZBx glasses improved as La2O3 content increased. The observed promising properties of LZBx glasses is an indication that they can be useful for several applications including shielding against photons, electrons, and fast/thermal neutrons.

Anti-ablation performance of La2O3-modified ZrB2 coating on SiC-coated carbon/carbon composites

La2O3-modified ZrB2 coating was prepared on SiC-coated C/C composites by supersonic atmospheric plasma spraying (SAPS) with the aim of improving the anti-ablation performance of C/C composites. The effect of La2O3 contents on the anti-ablation performance were investigated. The results indicated that the 10 vol % La2O3–ZrB2 coating shows excellent anti-ablation performance. After ablation for 120 s under low heat flux oxyacetylene flame (2400 kW/m2), the linear ablation rate and mass ablation are only −0.0167 μm/s and −0.558 mg/s, respectively. After ablation for 30 s under high heat flux of oxyacetylene flame (4200 kW/m2), the coating still remains intact. The addition of 10 vol % La2O3 is capable of enhancing the anti-ablation performance of the ZrB2 coating. The La2O3 and La2Zr2O7 phases will be soften and melting during ablation, which can form a barrier to cover the surface and effectively prevent the erosion of oxyacetylene gas. Meanwhile, the generated ZrO2 particles play the role of pinning the molten layer, thus weakening the coating exfoliation by airflow erosion.

Microstructure and properties of in situ La2O3 and SiC co-doped WC-10 wt%Ni cemented carbides prepared by microwave sintering

In this work, composite powders of in situ La2O3 and 0.5 wt% SiC co-doped WC-10 wt% Ni cemented carbides were prepared by ball milling in conjunction with a surfactant-assisted hydrothermal method. The composite powders were compacted and then microwave sintered at 1450 °C, 1475 °C and 1500 °C. The composition, microstructure and mechanical properties of the prepared samples were investigated by X-ray diffraction (XRD), scanning electron microscopy (SEM) and mechanical properties tests. The effects of the in situ La2O3 contents on the microstructure and mechanical properties of the fabricated samples were studied in detail. The results indicated that the addition of a small amount of La2O3 to the WC-10 wt% Ni cemented carbides enhanced the sintering, inhibited the WC grain growth, refined the WC grains and improved the mechanical properties. The average WC grain size decreased with an increasing amount of the added La2O3. For the La2O3 content of 0.5 wt%, the relative density, hardness, bending strength, and fracture toughness (KIC) of the WC-10 wt%Ni-0.5SiC-0.5La2O3 cemented carbides prepared at 1475 °C reached their maximum values of 99.75%, 1955 HV, 2114.3 MPa and 16.19 MPa⋅m1/2, respectively. It was also revealed that grain refinement, crack deflection, crack bridging and microcrack toughening were the strengthening and toughening mechanisms of the carbides. Additionally, the corrosion resistance of the WC-10 wt%Ni-0.5 wt%SiC-xLa2O3 cemented carbides in 3.5% NaCl aqueous solution was improved with in situ La2O3 doping and the best corrosion resistance was obtained for the WC-10Ni-0.5SiC-0.5La2O3 cemented carbides. The present results show that La2O3 and SiC co-doped WC-10 wt% Ni cemented carbides had excellent and comprehensive performances.

Lead borate glasses and synergistic impact of lanthanum oxide additive: optical and nuclear radiation shielding behaviors

Composition of (50 − x) B2O3–30PbO–20ZnO–xLa2O3 (x = 0, 1.5, 3, 4.5, and 6) wt% glass system were synthesized using quench melt technique and simulated for their nuclear radiation shielding properties. Moreover, UV–visible absorption spectrum among 190–1100 nm and the glass optical parameters were measured. The optical energy gap (Eg), the single-oscillator energy (Eo), the dispersion energy parameter (Ed), refractive index (n), and refractive dispersion index (no) were estimated. The obtained results indicated that (Eg) was decreased with increasing La2O3 content, but the refractive index (n) was increased. The addition of La2O3 to glass network could provide preferable shielding features. The chosen amount of La and another metal oxide has been added to the glass. Shielding parameters such as half-value layer (HVL), mean free path (MFP), mass attenuation coefficient (MAC), and exposure rate in the photon energy range 15–300 keV have been simulated by MicroShield software. These results illustrate that the La5 glass sample has the best radiation shielding properties, among other investigated glasses. This type of glass sample can utilize for the construction of the monitoring screening windows in radiation areas, plats, or screening windows in X-ray diagnostic and for the walls of CT-scanner rooms.

One-pot synthesis of La2O3-decorated Mg-Al oxides nanosheets for solar-light driven photocatalytic activity

La2O3-decorated Mg-Al layered double oxides (La2O3/Mg-Al) nanosheets were prepared by a one-pot hydrothermal route for the visible light induced photo-degradation of methylene blue (MB). La2O3 is favorable for enhancing the adsorption-photocatalytic activity of Mg-Al oxides. Effects of La2O3 content, pH values, and inorganic ions on the removal efficiency and photocatalytic kinetics of MB were well discussed. The optimal 3-La2O3/Mg-Al with a La2O3 content of 4.32 % presents the best adsorption-photocatalysis capacity and stability for MB in visible light region. The removal efficiency of MB is 98.06 % within 100 min, and the corresponding photocatalysis kinetic constant of 3-La2O3/Mg-Al is 0.051 min−1. The combined effect of La2O3 and Mg-Al oxides and the oxygen vacancies are likely to enhance the charge transfer and the separation of charge carriers. OH and O2− radicals are vital for the photocatalytic activity of 3-La2O3/Mg-Al under visible light irradiation.

Linear, nonlinear optical and photon attenuation properties of La3+ doped tellurite glasses

Abstract Linear and nonlinear optical features of La3+ doped tellurite glasses in the form 75TeO2–10ZnO –5Li2O –(10-x)Nb2O5 –xLa2O3: x = 0, 0.5, 1.0, 1.5, 2.0, and 2.5 in mol% (abbreviated as La0.0. La0.5, La1.0, La1.5, La2.0, and La2.5) were investigated. Also, the γ-photons attenuation parameters were tested utilizing Geant4 simulation code. Results revealed that the molar polarizability (αmolar) takes values from 8.685 × 10−24 to 7.933 × 10−24 cm3, while the molar refraction (Rmolar) changes from 21.886 to 20.219 (cm3/mol) for La0.0 to La2.5 glasses. The static dielectric constant (estatic) varies from 6.368 to 5.191, whereas optical electronegativity (χ*) varies from 0.690 to 0.852 for La0.0-La2.5 glasses. Non-linear optical susceptibility (χ3) decreases from 5.675 × 10−12 to 2.109 × 10−12 (esu) with increment La2O3 content in the glasses, while non-linear refractive index ( n 2 o p t i c a l ) decreases from 8.472 × 10−11 to 3.488 × 10−11 (esu). The radiation attenuation characteristics for the tested glasses were investigated with the help of Geant4 code. The mass attenuation coefficient (μm) was simulated between 0.284 and 2.506 MeV. The influnce of La2O3 on the shielding parameters was examined. Among the studied glasses, La2.5 posseses the highest μm values. Also, La2.5 sample has the lowest transmission fraction, which implies that more photons can be attenuated with La2.5 glass using a thin glass layer. From the transmission fraction results, we found that thick glasses are needed to attenuate gamma rays coming at high energies. At 0.511 MeV, the half value layer (HVL) value of the La0.0 glass is 1.49 cm while, at the same energy, the HVL value of the La2.5 glass is 1.44 cm.

Comparison of adsorption behaviors of Fe-La oxides co-loaded MgO nanosheets for the removal of methyl orange and phosphate in single and binary systems

Abstract Fe-La oxides co-loaded MgO (Fe-La/MgO) nanosheets were prepared for the adsorption of methyl orange and phosphate in single and binary systems. The Fe-La oxides content, concentration ratio of methyl orange to phosphate, inorganic ions, and pH values greatly affect the competitive adsorption performance of Fe-La/MgO in binary system. Among these obtained Fe-La/MgO composites, Fe-La/MgO-2 with a total Fe-La oxides content of 4.0 wt% and a Fe/La molar ratio of 1:1 presents the best adsorption capacity of phosphate (38.82 mg g−1) within 120 min, and La2O3/MgO with a La2O3 content of 2.0 wt% exhibits the highest adsorption activity of methyl orange (30.38 mg g−1) within 40 min in single system. However, the adsorption capacities of Fe-La/MgO-2 for phosphate and methyl orange in binary system are respectively 39.51 mg g-1 and 16.52 mg g−1 within 40 min due to the competitive adsorption between phosphate and methyl orange. The low pH is favorable for the separation of phosphate and methyl orange in binary system. Langmuir isotherm and second-order model can well fit with the adsorption isotherms and kinetics in single system. In addition, these adsorption processes of Fe-La/MgO-2 for methyl orange and phosphate in single system are the physisorption and chemisorption governed by the intra-particle diffusion and external mass transfer, respectively.

Relationship between leaching behavior and glass structure of calcium-aluminoborate waste glasses with various La2O3 contents

We investigated the correlation between the structures of 4-component glasses (B2O3–CaO–Al2O3–La2O3) and their leaching behaviors. We used a FT-IR and a MAS-NMR to analyze the structures of ground as-prepared and leached glasses for 7 and 28 days. Elemental releases represent that the leaching was incongruent. After leaching 28 days, BO4 structure dramatically decreased and AlO6 ratio increased compared to the glasses before the leaching test. That might be because these structures in the glasses were broken or released into solution during the leaching test. The addition of La3+ into the glass stabilizes the formation of BO4 and more highly charged AlO5 and AlO6.

Effect of the Addition of La2O3 on the Properties of ZrO2-Al2O3 Ceramic Composites for Coatings in Aerospace Turbines

Ceramic matrix composites have attracted the interest of turbine manufacturers for use in coating hot sections because of their higher capacity to withstand high temperatures and because they have a lower requirement for air cooling. One of the most commonly used ceramic coatings is zirconia-yttria. However, its main disadvantage is the inherent fragility of ceramics, which limits the use of these materials in mechanical structures and industrial applications. Ceramics are generally reinforced with the incorporation of additives to reduce their brittleness and increase their mechanical strength and toughness. It is known that La2O3 which are potential source for stabilization of zirconia composites. In this context, ZrO2-Al2O3-La2O3 based ceramic matrix composites were developed for deposition of a thermal barrier coating on the substrate of exhaust nozzles of aerospace turbines varying the content of La2O3 by 5, 7 and 10 wt%. The composites were produced by a thermomechanical process and sintered at 1385 °C. The properties of these composites were studied by X-ray diffraction, relative density, scanning electron microscopy, and Vickers microhardness tests. The results indicate that the composite with 10% La2O3 has great potential for use as ceramic coatings of turbine exhaust nozzles in the aerospace industry.

Lanthanum-Modified MCF-Derived Nickel Phyllosilicate Catalyst for Enhanced CO2 Methanation: A Comprehensive Study.

For the traditional preparation method, it is challenging to fabricate a supported nickel catalyst with fine size at high loading. In this work, a group of La-modified mesostructured cellular foam (MCF)-derived nickel phyllosilicates was designed and synthetized by a hydrothermal method followed by an impregnation-modification of La2O3, whose Ni contents varied from 25.3 to 32.2 wt %. Both the special property of phyllosilicate and the addition of a La2O3 modifier played significant roles in achieving high Ni dispersion and excellent catalytic performance. The formed nickel phyllosilicate was beneficial to obtain small Ni nanoparticles (<5 nm) due to its strong metal-support interaction and high specific surface area; the addition of the La2O3 modifier could further reduce the Ni particle size and decrease the reduction difficulty of the fabricated samples. On the contrary, a large Ni particle size of 13.0 nm was observed on the impregnated Ni/MCF (N/M-Im) catalyst with a Ni content of 31.7 wt %. As a result, the nickel phyllosilicate catalyst showed higher catalytic activity than the impregnated one, and the La modifier could further improve the catalytic activity especially at low temperature (<400 °C). Among all catalysts, the modified phyllosilicate catalyst N/M-P-32-5L with 180 °C-32 h-hydrothermal treatment and La2O3 content of 5 wt % was the best owing to its small-sized Ni particles, high H2 and CO2 chemisorption capacity, large turnover frequency (TOF) value, and low activation energy of 69.83 kJ mol-1. In addition, the intermediates of formate and CO were detected through in situ diffuse reflectance infrared Fourier transform spectroscopy (DRIFTS) analysis. In a 100 h-lifetime test under harsh conditions and 600 °C-steam treatment, N/M-P-32-5L showed both high sintering resistance of Ni particles and high thermal stability without the collapse of pores as well as decrease of catalytic activity, which was attributed to the special physical and chemical properties of MCF-derived nickel phyllosilicate, strong metal-support interaction over the catalyst, and the promotion of the La2O3 modifier.

Improving sealing properties of CaO-SrO-Al2O3-SiO2 glass and glass-ceramics for solid oxide fuel cells: Effect of La2O3 addition

The La2O3-doped CaO-SrO-Al2O3-SiO2 glasses were prepared by the melting method. The main IR absorption peaks shift to the low wavenumber direction after the introduction of La2O3, which indicates that the amount of non-bridged oxygen in the glasses increases and the glass network depolarizes. With the increase of La2O3 content, the micro-hardness, glass transition temperature, and crystallization temperature show an increasing trend. The mass loss of acid and alkali resistance is less than 0.5 wt%, which does not affect the sealing effect of the fuel cells. The glasses were nucleated at 850 °C for 2 h and crystallized at 1050 °C for 1 h. The precipitated crystal phases of the glass-ceramics were mainly composed of SrAl2Si2O8, Ca2Al2SiO7, and CaSrAl2SiO7. As the amount of La2O3 reaches 2.5 mol%, the new crystal phase Ca3La6(SiO4)6 appears in the glass-ceramic. Ca3La6(SiO4)6 crystals liberate much more SiO2 (in comparison to other crystals) leaving Al2O3 on the border that can results in CTE increase since Al2O3 has a significantly higher CTE in compare to SiO2. The CTE of the glass-ceramics varies within the range of 9.3–11.3 ± 0.1 × 10-6 °C-1. Generally, the La2O3-doped 25CaO-20SrO-10Al2O3-45SiO2 sealing glasses have the thermal expansion coefficients similar to that of other SOFCs components.