Investigations on Material and Mechanical Properties,Air‐Permeation Behavior and Filtration Performance of Mullite‐Bonded Porous SiC Ceramics

A theoretical relation between processing parameters and porosity (29–56%) of mullite‐bonded porous SiC ceramics was derived and validated with experimental data. Porosity‐dependent variation of fracture strength (9–34 MPa) and elastic modulus (7–28 GPa) was explained by the minimum solid area model. At room temperature, the Darcian, k₁ (1.2 × 10^?13–1.6 × 10^?12 m²) and the non‐Darcian, k₂ (4.6 × 10^?9–2.7 × 10^?7 m) permeability coefficients showed linear variation with porosity. Tests conducted up to 650°C indicated an increase in k₁ with temperature and a reverse trend for k₂. Airborne NaCl nanoparticle filtration tests showed good performance of SiC ceramics with fractional collection efficiency of >99% at 46–56% porosity levels.     

Porosity effect on microstructure,mechanical, and fluid dynamic properties of Ti2AlC by direct foaming and gel‐casting

In this study, Ti₂AlC foams were fabricated by direct foaming and gel‐casting using agarose as gelling agent. Slurry viscosity, determined by the agarose content (at a fixed solids loading), as well as surfactant concentration and foaming time were the key parameters employed for controlling the foaming yield, and hence the foam porosity after sintering process. Fabricated foams having total porosity in the 62.5‐84.4 vol% range were systematically characterized to determine their pore size and morphology. The effect of the foam porosity on the room‐temperature compression strength and elastic modulus was also determined. Depending on the amount of porosity, the compression strength and Young's modulus were found to be in the range of 9‐91 MPa and 7‐52 GPa, respectively. Permeability to air flow at temperatures up to 700°C was investigated. Darcian (k₁) and non‐Darcian (k₂) permeability coefficients displayed values in the range 0.30‐93.44 × 10^?11 m² and 0.39‐345.54 × 10^?7 m, respectively. The amount of porosity is therefore a very useful microstructural parameter for tuning the mechanical and fluid dynamic properties of Ti₂AlC foams.     

Effects of partial pressure of oxygen on sintering of a ZrO2-30 mol% Ti powder mixture

A powder mixture of ZrO₂-30 mol% Ti was sintered at 1500 °C/h under various controlled partial pressures of oxygen (PaO₂). The microstructure of each sintered sample was characterized using x-ray diffractometry and analytical transmission electron microscopy/energy-dispersive spectroscopy. TiO and highly oxygen-deficient zirconia were found after sintering at PaO₂ ~2.1×10⁻⁴ atm, which implies that the oxidation–reduction reaction is a controlling mechanism when there is a trace of residual oxygen. When the PaO₂ was increased to 1.05×10⁻¹ atm, the dissolution of residual oxygen and nitrogen in the chamber into the titanium led to the formation of TiO(N) with nitrogen in solid solution. It was inferred that the oxygen in TiO(N) was also supplied by zirconia since the zirconia became oxygen-deficient in the sintered composites. After sintering in air (PaO₂ ~2.1×10⁻¹ atm), TiO₂ and TiN were formed along with nearly stoichiometric zirconia, indicating that oxygen and nitrogen in air played a major role in the oxidation and nitridization reaction of titanium. The degree of oxygen deficiency x in ZrO_2−x decreased with increasing oxygen partial pressure, which led to an increased volume fraction of the monoclinic phase.     

Structure and Thermal Expansion of YSZ and La2Zr2O7 Above 1500°C from Neutron Diffraction on Levitated Samples

High‐temperature time‐of‐flight neutron diffraction experiments were performed on cubic yttria‐stabilized zirconia (YSZ, 10 mol% YO_1.5) and lanthanum zirconate (LZ) prepared by laser melting. Three spheroids of each composition were aerodynamically levitated and rotated in argon flow and heated with a CO₂ laser. Unit cell, positional and atomic displacement parameters were obtained by Rietveld analysis. Below ~1650°C the mean thermal expansion coefficient (TEC) for YSZ is higher than for LZ (13 ± 1 vs. 10.3 ± 0.6) × 10^?6/K. From ~1650°C to the onset of melting of LZ at ~2250°C, TEC for YSZ and LZ are similar and within (7 ± 2) × 10^?6/K. LZ retains the pyrochlore structure up to the melting temperature with Zr coordination becoming closer to perfectly octahedral. Congruently melting LZ is La deficient. The occurrence of thermal disordering of oxygen sublattice (Bredig transition) in defect fluorite structure was deduced from the rise in YSZ TEC to ~25 × 10^?6/K at 2350°C–2550°C with oxygen displacement parameters (U_iso) reaching 0.1 Å², similar to behavior observed in UO₂. Acquisition of powder‐like high‐temperature neutron diffraction data from solid‐levitated samples is feasible and possible improvements are outlined. This methodology should be applicable to a wide range of materials for high‐temperature applications.     

Thin layer drying kinetics of Gundelia tournefortii L.

The literature surveyed revealed that the drying kinetics of Gundelia tournefortii has not been investigated. In this study, mathematical modeling of the thin layer drying kinetics of G. tournefortii is investigated for both the microwave and open sun drying conditions. Five different microwave power levels ranging from 90 to 800 W were used for the microwave drying. Solar radiation for the open sun drying varied from 350 to 1100 W/m². Drying took place in the falling rate period. Increasing the microwave power caused a significant decrease in drying time. The experimental moisture loss data were fitted to the 14 thin layer drying models. Among the models proposed, the Midilli model precisely represented the microwave drying behavior of G. tournefortii with the coefficient of determination higher than 0.996 and mean square of deviation (χ²), root mean square error (RMSE) and mean bias error (MBE) lower than 1.82 × 10^?4, 12 × 10^?3 and 1.4 × 10^?4, respectively for all the microwave drying conditions studied. Values of drying constant (k) were in the range of 0.0098–0.2943 min^?1 and the effective moisture diffusivities (D_eff) of G. tournefortii ranged from 5.5 × 10^?8 to 3.5 × 10^?7 m²/s. The values of k and D_eff increased with the increase of microwave power level. The logarithmic model was found to best describe the open sun drying kinetics of G. tournefortii. The effective diffusivity of G. tournefortii under the sun drying condition was determined as 2.48 × 10^?10 m²/s.     

Porous titanium dioxide supported on glass microbubbles to prepare a low-density photocatalyst for AR1 degradation

Low-density TiO₂(C)/GB hollow powders were synthesized by loading anatase TiO₂ onto glass microbubbles. CTAB (cetyltrimethyl ammonium bromide) was used to produce pores in the supported TiO₂. A TiO₂ layer with a thickness greater than 100 nm was tightly loaded onto the glass microbubbles. CTAB led to a slight expansion of the bandgap energy from 3.22 eV (TiO₂(0)/GB) to 3.41 eV (TiO₂(3.0)/GB). The E_CB and the E_VB values were ?0.32 and 2.91 V for the TiO₂(1.5)/GB, respectively. Both the average pore size (from 5.59 to 9.44 nm) and the total pore volume (from 0.0799 to 0.1283 cm³/g) of TiO₂(C)/GB increased with an increasing amount of CTAB. The hole-electron recombination efficiency was in the sequence of TiO₂(1.5)/GB< TiO₂(3.0)/GB< TiO₂(0)/GB. The AR1 degradation efficiency varied with the CTAB amount, and the maximum degradation efficiency was obtained for TiO₂(1.5)/GB. The TiO₂(C)/GB hollow powders were suspended in an AR1 solution during the degradation process, and TiO₂(C)/GB floated on the water surface after treatment to ensure fast solid-water separation. The reaction rate constants were 1.79 × 10^?2 and 1.21 × 10^?2 min^?1 for TiO₂(1.5)/GB and the unsupported TiO₂ powders, respectively. TiO₂(1.5)/GB had a stronger activity than the TiO₂ powders.     

Effect of preparation route on the microstructure and electrical conductivity of co-doped ceria

Dense Ce_0.8Sm_0.1Gd_0.1O_2?δ electrolytes were fabricated by sintering of CeO₂ solid solutions which were prepared from metal nitrates and NaOH using self propagating room temperature synthesis (SPRT). Three different routes were employed to obtain CeO₂ solid solution powders: (I) hand mixing of reactants, (II) ball milling of reactants and (III) ball milling of Ce_0.8Sm_0.2O_2?δ and Ce_0.8Gd_0.2O_2?δ solid solutions previously prepared by ball milling of corresponding nitrates and NaOH. Density measurements showed that ball milling, which is more convenient than hand mixing, is an effective way to obtain almost full dense samples after presureless sintering at 1550 °C for 1 h. These samples had larger grain size and consequently higher conductivity than the samples obtained by hand mixing. The highest conductivity of 2.704×10^?2 (Ω cm)^?1was measured at 700 °C in a sample prepared by route II. It was found that reduced grain size in samples obtained by hand mixing leads to a decrease in grain boundary conductivity and therefore decrease in the total conductivity. The results showed that mixing of single doped ceria solid solutions improved densification and inhibited grain growth.     

Synthesis and thermal expansion behaviors of spin-coated Sc2Mo3O12 thin films

Orthorhombic Sc₂Mo₃O₁₂ films have been successfully prepared via spin coating technique followed by annealing at 500–750 °C. The phase composition, microstructure, morphology and negative thermal behavior of the synthesized Sc₂Mo₃O₁₂ films were investigated. XRD and XPS analysis indicate that as-deposited film is amorphous. Orthorhombic Sc₂Mo₃O₁₂ films can be prepared after post-annealing at 500–750 °C for 1 h. The crystallinity of Sc₂Mo₃O₁₂ films gradually improved with the increase of post-annealing temperature. SEM analysis shows as-deposited film is smooth and compact, and the grain size of Sc₂Mo₃O₁₂ film grows up as the post-annealing temperature increases. Variable temperature XRD analysis demonstrates that the synthesized orthorhombic Sc₂Mo₃O₁₂ films show stable thermo-chemical and anisotropic NTE property in 25–700 °C. The corresponding coefficients of thermal expansion (CTEs) of the orthorhombic Sc₂Mo₃O₁₂ film in a, b and c directions are ?6.68 × 10^?6 °C^?1, 5.08 × 10^?6 °C^?1 and ?4.76 × 10^?6 °C^?1, respectively. The whole unit cell of the orthorhombic Sc₂Mo₃O₁₂ film shrinks and the volumetric CTE of the Sc₂Mo₃O₁₂ thin film is ?6.36 × 10^?6 °C^?1, and the linear CTE is about ?2.12 × 10^?6 °C^?1 (α_v = 3α_l).     

Effects of salicylate derivate on the competing reaction of chromium(III) complex [Cr(III)(R-SA)(en)2]Cl with apoovotransferrin

Four novel Cr(III) complexes, Bis(ethylenediamine-κ²N,N′)(R-SA-κ²O,O′)chromium(III) chloride (H₂SA = salicylic acid, R = 5-F, 5-Cl, 5-Br, 4-CH₃ ethylenediamine = en) have been synthesized and three of them are determined by X-ray crystallography. The competition reaction with EDTA and apoovotransferrin (apoOTf) was monitored by UV–Visible (UV–vis) and fluorescence spectra at 37 °C. The reaction with EDTA is only a simple competitive process and no specific selectivity was observed (k_EDTA/F410 = 4.07 × 10^?3–4.37 × 10^?3 M^?1 s^? 1). While for the reaction with apoOTf, an instable intermediate species (R-SA)–Cr(III)–OTf forms (k_OTf/F336 = 1.70 × 10^? 1–2.08 × 10^?1 M^?1 s^? 1), where R-SA^2? act as the role of synergistic anion. The intermediate is instable and the R-SA^2? ligand will then be released with the rate constants of 1.17 × 10^? 1 (5-F-SA^2?) ≈ 1.01 × 10^? 1 (4-CH₃-SA^2?) > 3.19 × 10^? 2 (5-Cl-SA^2?) > 3.25 × 10^? 3 (5-Br-SA^2?) M^?1 s^? 1. The substitutive groups R on SA have positive influence on charge density of O donor atom, which directly affect the stability of the (R-SA)–Cr(III)–OTf intermediate.     

Thermal expansion of EB-PVD yttria stabilized zirconia

Yttria stabilized zirconia (YSZ) layers, suited for thermal barrier coatings (TBCs) in turbine engines, were produced by electron-beam physical vapour deposition (EB-PVD) on metallic (Ni-based alloys) ceramic (Al₂O₃) substrates (typically at 1000 °C) using ingot compositions of about 4 mol% Y₂O₃–ZrO₂. Employing powdered samples, removed from the surface of the as-deposited YSZ layers, precision X-ray diffraction data sets were recorded between 60 and 900 °C and the lattice parameters of the metastable, tetragonal (t′) and the cubic (c) phases were refined using Rietveld's method. It was unambiguously verified that phase (c) was present in all investigated samples as a minority phase already in the as-deposited state.The thermal expansion coefficients of the tetragonal phase (t′) (α₁₁ = 9.3(2) × 10^?6 K^?1, α₃₃ = 10.8(1) × 10^?6 K^?1) and the cubic phase (c) (α₁₁ = 8.5(2) × 10^?6 K^?1) were evaluated from the refined temperature dependent lattice parameter values of this study, and turned out to be close to each other, but significantly different from the coefficient of the monoclinic phase (m) (α₁₁ = 9.0 × 10^?6 K^?1, α₂₂ = 1.2 × 10^?6 K^?1, α₃₃ = 11.9 × 10^?6 K^?1, α₁₃ = 0.0 × 10^?6 K^?1), which was derived from temperature dependent lattice parameter measurements published by Touloukian et al.⁵ The expansion coefficient of the monoclinic phase (m) exhibited a very pronounced anisotropy in contrast to the tetragonal phases (t′) and (t). Our values for (t′) and (c) were in excellent agreement with that of other tetragonal and cubic phases from the literature with quite different Y₂O₃ contents.     

Investigation of the Ga-Sb-S chalcogenide glass with low thermo-optic coefficient as an acousto-optic material

In this study, two series of Ga_xSb_40-xS₆₀ (x = 4, 6, 8, 10 mol%) and Ga_ySb₃₆S_64-y (y = 3, 5, 6 mol%) glasses were prepared and the relationship between their compositional and acousto-optic (AO) properties was investigated systematically for the first time. In the Ga_ySb₃₆S_64-y system, the AO figure of merit (M₂) increased as the Ga increased, and the maximum M₂ of the Ga₆Sb₃₆S₅₈ glass was 455.78 × 10^?18 s³/g, which is ～301 times greater than that of fused silica and ～2.5 times greater than that of As₂S₃ chalcogenide (ChG) glass at 1550 nm. However, its thermo-optic coefficients (dn/dT) varied greatly (32.1 × 10^?6 °C^?1–57.2 × 10^?6 °C^?1), and acoustic attenuations (α) at 10 MHz were high, from 5.446 dB/cm to 7.274 dB/cm. In the Ga_xSb_40-xS₆₀ glass system, the M₂ value and α at different ultrasonic frequencies gradually decreased with the improvement of Ga. Compared with the Ga_ySb₃₆S_64-y system, the Ga_xSb_40-xS₆₀ glass system had lower α (at 10 MHz) and dn/dT, which are 5.001 dB/cm–5.563 dB/cm and 17.3 × 10^?6 °C^?1–55.6 × 10^?6 °C^?1, respectively. These results provide a significant reference for the further development of novel ChG glasses and help expand their application fields.     

Evaluation of Air Permeation Behavior of Porous SiC Ceramics Synthesized by Oxidation‐Bonding Technique

Porous SiC ceramics were synthesized by oxidation bonding of compacts of commercial α‐SiC powder at 1300°C. Different volume fractions of petroleum coke powder were used for variation of porosity of ceramics from 36% to 56%. The material exhibited variations of pore size from 3 to 15 μm, flexural strength from 5.5 to 29.5 MPa, and elastic modulus from 3.3 to 27.6 GPa. Air permeation behavior was studied at 26–650°C. At room temperature Darcian (k₁) and non‐Darcian (k₂) permeability parameters vary from 1.64 to 18.42 × 10^?13 m² and 0.58 to 2.95 × 10^?7 m, respectively. Temperature dependence of permeability was explained from structural changes occurring during test conditions.     

Study on drying kinetics of calcium oxide doped zirconia by microwave-assisted drying

Ca–ZrO₂ is an essential structural and functional material, which is commonly used in refractories, electronic ceramics, and functional ceramics. The properties of Ca–ZrO₂ materials are depending on the quality of Ca–ZrO₂ powders. The main factors affecting the quality of powder are sintering temperature and the drying effect. This paper applied modern microwave drying technology to dry Ca–ZrO₂ powder. The impact of initial mass, microwave heating power, and initial moisture content on the drying of Ca–ZrO₂ were explored. The results showed that the average drying rate increased with the rise of initial mass, microwave heating power, and initial moisture content. Wang and Singh, Page, and Quadratic Model were applied to fit Ca–ZrO₂ with an initial moisture content of 5.6%, mass of 30 g, and microwave output power of 400 W. The results displayed that the Page model had a better fitting effect. It was also applicable to other different initial moisture content, original mass, and microwave heating power. The diffusion coefficient calculated by Fick's second law displayed that with the increase of initial mass, initial moisture content, and microwave heating power of Ca–ZrO₂, the effective diffusion coefficient increased first and then declined. When the Ca–ZrO₂ of microwave heating power was 640 W, mass was 30 g, and the moisture content was 5.65%, the effective diffusion coefficients of zirconia were 1.42533 × 10^?13, 2.91806 × 10^?13, 5.652.2471 × 10^?13 m²/s, respectively. To determine the activation energy of microwave dried zirconia, using the relationship between microwave power and activation energy, the activation energy of microwave dried zirconia was calculated to be ?23.39 g/W. This paper aims to rich experimental data for the industrial application of microwaves to strengthen dried zirconia and propose a theoretical basis.     

Study of kinetics in the biosorption of lead onto native and chemically treated olive stone

In this research, olive stone was used as precursor for the development of new biosorbents for lead ions. Chemical treatments were analyzed in terms of their effects on physical–chemical properties and kinetics of lead removal. A kinetic study of the biosorption of lead ions by olive stone was analyzed according to six different kinetic models (pseudo first, pseudo second, pseudo n-order, Elovich, solid diffusion and double exponential models). The biosorption kinetic data were successfully described with pseudo-nth order and double exponential models for all biosorbents. The double exponential model allowed estimating the values of external and internal mass transfer coefficients. The values of external mass transfer coefficient (k_e) ranged from 42.62 × 10⁻⁶ to 508.3 × 10⁻⁶ m min⁻¹ and the internal mass transfer coefficient (k_i) from 3.76 × 10⁻⁶ to 73.4 × 10⁻⁶ m min⁻¹. On the other hand, the analysis of experimental data showed that chemical treatments of the biomass led to increase biosorption capacity of the native biomass.     

Permeability of porous gelcast scaffolds for bone tissue engineering

The permeability of metallic and ceramic open-cell foams prepared by the gelcasting technique was assessed by fitting of Forchheimer’s equation to experimental pressure drop curves. The ceramic composition was based on pure hydroxyapatite, while the metallic composition was based on titanium metal. Experimental Darcian (k ₁) and non-Darcian (k ₂) permeability constants displayed values in the range 0.40–3.24 × 10^?9 m² and 3.11–175.8 × 10^?6 m respectively. Tortuosity was evaluated by gas diffusion experiments and ranged from 1.67 to 3.60, with porosity between 72 and 81% and average hydraulic pore size between 325 and 473 μm. Such features were compared to data reported in the literature for cancellous bones and synthetic scaffolds for bone graft. A detailed discussion concerning the limitations of Darcy’s law for fitting laboratory data and for predicting fluid flow through scaffolds in real biomedical applications is also performed. Pore size was obtained by image analysis and was also derived from permeation-absorption-diffusion experiments. In both cases, values were within the range expected for porous scaffolds applications.     

Electrospinning synthesis and negative thermal expansion of one-dimensional Sc2Mo3O12 nanofibers

Orthorhombic Sc₂(MoO₄)₃ nanofibers have been prepared by ethylene glycol assisted electrospinning method. The effects of annealing temperature, precursor concentration, spinning distance and solvent on the preparation of Sc₂(MoO₄)₃ nanofibers were characterized by XRD, SEM, HRTEM, EDX and high-temperature XRD. XRD analysis shows as-prepared nanofibers are amorphous. Orthorhombic Sc₂(MoO₄)₃ nanofibers can be fabricated after annealing at different temperatures in 500–800 °C for 2 h. The crystallinity of Sc₂(MoO₄)₃ nanofibers improves and the nanofiber diameter decreases gradually as the annealing temperature increases. However, the nanofiber structure was destroyed at the annealing temperature above 700 °C. Higher precursor concentration results in a slight increase of diameter and decrease in destroying temperature of Sc₂(MoO₄)₃ nanofibers. Spinning distance also affects the diameter of nanofibers, and the nanofiber diameter decreases as the distance increases. One-dimensional orthorhombic Sc₂(MoO₄)₃ nanofibers exhibit anisotropic negative thermal expansion. In 25–700 °C, the coefficients of thermal expansion (CTE) of α_a, α_b and α_c are ?5.81 × 10^?6 °C^?1, 4.80 × 10^?6 °C^?1 and -4.33 × 10^?6 °C^?1, and the α_l of Sc₂(MoO₄)₃ nanofibers is ?1.83 × 10^?6 °C^?1.     

Anionic polymerization of styrene in triglyme-benzene mixtures

Living anionic polymerization of styrene was kinetically investigated in triglyme-benzene mixtures. At low concentrations of triglyme the overall propagation rate constant, k_p, was much larger than at the same concentration of monoglyme (DME) in DME-benzene mixtures. The Szwarc-Schulz plot did not have negative slopes for lithium and sodium salts at triglyme contents of 5～20vol%, and no contribution of free anions to the propagation was observed for the sodium salt. The sodium ion pair was more highly reactive than the lithium ion pair; thus at 25°C, the ion pair rate constant, k′_p, for the lithium salt was 43, 102, 135 and 165 M^?1sec^?1 at triglyme concentrations of 5, 10, 15, and 20%, respectively, while that for the sodium salt was 410, 920, and 1460 M^?1sec^?1 in 5, 10, and 15% triglyme, respectively. The dissociation constant, K, for the lithium salt was 2·4×10^?11, 1·9×10^?10 and 1·3×10^?9 M in 10, 15, and 20% triglyme, respectively and the free ion rate constant, k″_p, was 2～2·5×10⁴ M^?1sec^?1 for the lithium salt.     

Structure and microwave dielectric properties of Li(Al1-xLix)SiO4-x ceramics

Li(Al_1-xLi_x)SiO_4-x (x = 0.005, 0.01, 0.015, and 0.02) ceramics were synthesized via a traditional solid phase reaction method with different sintering temperatures. To determine the positions occupied by Li⁺ in the lattice, the defect formation energies and total energies of various sites of LiAlSiO₄ (LAS) occupied by Li⁺ were examined, and the energy of LAS systems were calculated using density functional theory of first-principle with the CASTEP module. The results demonstrated that the Al-sites occupied by Li⁺ had the lowest formation energies and total energy, so Li ⁺ should substitute Al³⁺. The impacts of replacing Al³⁺ with Li⁺ on the bulk density, sintering properties, phase composition, microstructure, and microwave dielectric properties of Li(Al_1-xLi_x)SiO_4-x (0 = x ≤ 0.02) ceramics were thoroughly studied. With Li⁺-doping, the sintering temperature decreased from 1300 °C (x = 0) to 1175 °C (x = 0.02), while the Q × f and τ_f values of LAS ceramics significantly increased. The Li(Al_0.99Li_0.01)SiO_3.99 ceramic was fully sintered at 1250 °C for 10 h to obtain excellent microwave dielectric properties: ε_r = 3.49, Q × f = 51,358 GHz, and τ_f = ?51.48 × 10^?6 °C^?1.     

Ca-doped PrBa1-xCaxCoCuO5+δ (x = 0–0.2) as cathode materials for solid oxide fuel cells

Ca-doped perovskite oxides PrBa_1-xCa_xCoCuO_5+δ (PBCCCO, x = 0–0.2) were prepared and investigated as SOFC cathode materials. PBCCCO samples are single perovskite structure with P4/mmm space group. Pr, Cu and Co ions in PBCCCO samples exist in the form of Pr³⁺/Pr⁴⁺, Cu²⁺/Cu⁺ and Co³⁺/Co⁴⁺ multi-valence states. The average TECs of PBCCCO samples were reduced from 17.4 × 10^?6 K^?1 (x = 0) to 16.7 × 10^?6 (x = 0.1) and 16.1 × 10^?6 K^?1 (x = 0.2) whin RT-900°С. The electrical conductivity and electrochemical catalytic activity of PBCCCO perovskites was enhanced obviously by Ca doping. The ASR values decreased by 60.1% (@650 °C), 68.9% (@700 °C), 71.0% (@750 °C) and 72.8% (@800 °C) respectively when Ca doping content increased from x = 0 to 0.2. These results suggest PBCCCO sample with Ca doing content x = 0.2 can be a promising cathode for IT-SOFC.     

Nonlinear Absorption of Submicrometer Grain‐Size Cobalt‐Doped Magnesium Aluminate Transparent Ceramics

Transparent cobalt‐doped magnesium aluminate spinel (Co:MgAl₂O₄) ceramics with a submicrometer grain size were prepared by spark plasma sintering. For the first time, the nonlinear absorption of Co:MgAl₂O₄ transparent ceramics was experimentally demonstrated. Both ground state absorption (σ_GSA) and excited state absorption (σ_ESA) were estimated using the solid‐state slow saturable absorber model based on absorption saturation measurements performed at 1.535 μm. σ_GSA and σ_ESA for 0.03 at.% Co:MgAl₂O₄ were found to be 4.1 × 10^?19 cm² and 4.0 × 10^?20 cm², respectively. In the case of 0.06 at.% Co:MgAl₂O₄ ceramics, σ_GSA = 2.6 × 10^?19 cm² and σ_ESA= 5.3 × 10^?20 cm² were determined.