The Oxidation of Coated SOFC Interconnects in Fuel Side Environments

This study focuses on examining the effect of PVD coatings on the oxidation performance of interconnects in fuel (anode) side environments. A Fe‐22Cr ferritic steel was coated with (i) Ce 10 nm (ii) La 10 nm and (iii) Co 600 nm. The samples were exposed at 850 °C in Ar‐5% H₂‐3% H₂O in a tubular furnace over 500 h. Additionally, the effect of a pre‐oxidation step was investigated by exposure in air prior to the simulated fuel gas environment. Chemical analysis on the samples was subsequently performed with SEM/EDX and XRD. It was established that the Ce and La coatings brought about a factor 2–3 reduction (k_p values of 2.16 × 10⁻¹⁴ ± 3.6 × 10⁻¹⁵ g² cm⁻⁴ s⁻¹ for the La 10 nm coated steel compared to 7.72 × 10⁻¹⁴ ± 5.86 × 10⁻¹⁵ g² cm⁻⁴ s⁻¹ for the uncoated steel) in the oxidation rate while the Co coating disintegrated into metallic islands in and on the thermally grown oxide after exposure. Additionally, the La coating resulted in the formation of a continuous perovskite layer by reaction with the thermally grown oxide.     

Reaction-bonded robust SiC ceramic membranes sintered at low temperature with coal gangue

Herein, we report an in-situ reaction-bonded SiC membrane sintered at low temperature using a solid waste (i.e. coal gangue) as the sintering aid to form strong neck connections. The effects of sintering temperature and coal gangue proportion on their properties regarding pore size, open porosity, bending strength and pure water permeability were investigated. The single-channel tubular SiC membrane sintered at 1300 °C with a coal gangue proportion of 12 wt% was optimal, exhibiting an average pore size of 2.78 μm, a open porosity of 47.08%, a bending strength of 34.01 ± 1.3 MPa and a high water permeability of 83967 L m⁻² h⁻¹ bar⁻¹. The membrane could completely reject D₅₀ = 0.87 μm SiC solids and presented a steady-state water permeability of 458 L m⁻² h⁻¹·bar⁻¹. The SiC membrane could be regenerated through ultrasonication and its steady-state water permeability was almost unchanged for 3 cycles, proving its mechanical robustness. This work may appeal to the practical low-cost production of high-performance SiC membranes.     

Design and operational considerations of catalytic membrane reactors for ammonia synthesis

Production of ammonia using hydrogen derived from renewable electricity instead of hydrocarbon reforming would dramatically reduce the carbon footprint of this commodity chemical. Novel technologies such as catalytic membrane reactors (CMRs) may potentially be more compatible with distributed ammonia production than the conventional Haber–Bosch process. A reactor model is developed based on integrating a standard industrial iron catalyst into a CMR equipped with an inorganic membrane that is selective to NH₃ over N₂/H₂. CMR performance is studied as functions of wide ranges of membrane properties and operating conditions. Conversion and ammonia recovery are dictated principally by the ammonia permeance, and the benefits by using membranes become significant above 100 GPU = 3.4 × 10⁻⁸ mol m⁻² s⁻¹ Pa⁻¹. To be effective, the CMR requires a minimum selectivity for ammonia of 10 over both nitrogen and hydrogen and purity scales with the effective selectivity. Increasing the pressure of operation significantly improves all metrics, and at P = 30 bar with a quality membrane, ammonia is almost completely recovered, enabling direct recycle of unreacted hydrogen and nitrogen without need for recompression. Temperature drives conversion and scales monotonically without thermodynamic limitations in a CMR. Alternatively, the temperature may be reduced as low as 300°C while achieving conversion levels surpassing equilibrium limits at T = 400°C in a conventional reactor.     

High gas permeability and directional channels of mullite porous ceramics prepared by pectin-based freeze-drying method

New gel system for preparing mullite porous ceramics by gel-casting freeze-drying was proposed, using pectin as gel source and alumina and silica as raw materials. Directional channels were formed due to sublimation of water during freeze-drying and decomposition of pectin during high temperature sintering to prepare porous mullite ceramic membranes. Effects of solid content on the properties of mullite ceramics in terms of phase composition, microstructure, apparent porosity, bulk density, pore size distribution, compressive strength, thermal conductivity, pressure drop, and gas permeability were investigated. It was found that prepared porous mullite possessed high apparent porosity (56.04%–75.34%), low bulk density (.77–1.37 g/cm³), uniform pore size distribution, relatively high compressive strength (.61–3.03 MPa), low thermal conductivity (.224–.329 W/(m·K)), high gas permeability coefficient (1.11 × 10⁻¹⁰–4.73 × 10⁻¹¹ m²), and gas permeance (2.18 × 10⁻²–9.32 × 10⁻³ mol⋅m⁻²⋅s⁻¹⋅Pa⁻¹). These properties make prepared lightweight mullite ceramic membranes promising for application in high temperature flue gas filtration. Proposed gel system is expected to provide a new route to prepare porous ceramics with high porosity and directional channels.     

Preparation and characterization of new tubular kaolino-illitic ceramic membrane used for dairy wastewater treatment

Low cost asymmetric tubular ceramic membrane was developed from kaolino-illitic clay collected from the region of Medenin (Tunisia). The obtained membrane was designed to be used for ultrafiltration. The effect of pore forming agent on the plasticity, porosity, pore size distribution, mechanical strength, and permeability was evaluated. The support was performed by extrusion using the raw clay and olive pomace (OP) as pore forming agent. The effect of the use of OP was noticeable; it improved the plasticity of the paste. Also it helped to ameliorate both permeability and porosity of the obtained supports. Top layer was prepared using acid activated clay suspension. The obtained membrane had gas permeability of about 13 cm³.s⁻¹.cm⁻².bar⁻¹ at a pressure of 1.5 bar and water flux of 1700 L.h⁻¹.m⁻² at a pressure of 1 bar. The final membrane was successfully used to eliminate the fat present in a solution containing 10% of milk. Regeneration of the used membrane was carried out by calcination at 550°C. The performances of the used membrane were recovered by 97% after regeneration.     

Synthesis and characterization of ternary layered i-MAX (Mo2/3Y1/3)2AlC ceramics fabricated by spark plasma sintering

In this paper, the i-MAX phase (Mo_2/3Y_1/3)₂AlC ceramic with high purity of 98.29 wt% (1.13 wt% Y₂O₃ and 0.58 wt% Mo₂C) and high relative density of 98.59% was successfully synthesized by spark plasma sintering (SPS) at 1500°C with the molar ratio of n(Mo):n(Y):n(Al):n(C) = 4:2:3.3:2.7. The positions of C atoms in the crystal of (Mo_2/3Y_1/3)₂AlC were determined. Microstructure and physical and mechanical properties of (Mo_2/3Y_1/3)₂AlC ceramic were systematically investigated. It was found that the obtained (Mo_2/3Y_1/3)₂AlC ceramic had an average grain size of 32.1 ± 3.1 μm in length and 14.2 ± 1.7 μm in width. In terms of physical properties, the measured thermal expansion coefficient (TEC) of (Mo_2/3Y_1/3)₂AlC was 8.99 × 10⁻⁶ K⁻¹, and the thermal capacity and thermal conductivity at room temperature were 0.43 J·g⁻¹·K⁻¹ and 13.75 W·m⁻¹·K⁻¹, respectively. The room temperature electrical conductivity of (Mo_2/3Y_1/3)₂AlC ceramic was measured to be 1.25 × 10⁶ Ω⁻¹·m⁻¹. In terms of mechanical properties, Vickers hardness under 10 N load was measured as 10.54 ± 0.29 GPa, while flexural strength, fracture toughness, and compressive strength were determined as 260.08 ± 14.18 MPa, 4.51 ± 0.70 MPa·m^1/2, and 855 ± 62 MPa, respectively, indicating the promising structural applications.     

Cassava bagasse as a reinforcement agent in the polymeric blend of biodegradable films

The objective of this work was to develop biodegradable films using fibrous residue from the extraction of cassava starch and to investigate its effect as a reinforcement agent in polymeric films. Micrographs (SEM) showed that the obtained films presented smooth surfaces with no cracking. The addition of fibers affected the properties of the films significantly (p < 0.05), reducing water vapor permeability values (from 8.63 ± 0.15 × 10⁻¹¹ g.m.m⁻².s⁻¹.Pa⁻¹ to 3.33 ± 0.16 × 10⁻¹¹ g.m.m⁻².s⁻¹.Pa⁻¹) and increasing the maximum tensile strength (from 1.23 ± 0.15 MPa to 7.78 ± 0.83 MPa). These results encourage the use of cassava bagasse as a reinforcement in the production of green composites as packaging. © 2018 Wiley Periodicals, Inc. J. Appl. Polym. Sci. 2019 , 136, 47224.     

Performance of pseudo-specific cryogel in lysozyme purification from chicken egg white

The application of cryogels for biomolecule purification has expanded due to their adsorption efficiency and operational advantages. In this study, polyacrylamide cryogels functionalized with l -phenylalanine (cryogel-Phe) via the glutaraldehyde method were designed for lysozyme adsorption. Cryogel functionalization was confirmed by Fourier-transform infrared spectroscopy and Kjeldahl analysis, indicating the immobilization of 458.65 mg_{phenylalanine} g_cryogel⁻¹. Cryogel-Phe showed high porosity (0.95) and a Young's modulus of 526.71 kPa. Thermogravimetric analysis indicated that thermal degradation occurred above 200°C. Differential scanning calorimetry and X-ray diffraction confirmed that the cryogel material was amorphous. In addition, the column presented a hydraulic permeability of 4.15 × 10⁻¹³ m², axial dispersion ranging from 10⁻⁷ to 10⁻⁶ m² s⁻¹, and a height equivalent to a theoretical plate ranging from 0.10 to 0.21 cm. The highest adsorption of lysozyme (67.65 mg g⁻¹) was obtained using sodium thiocyanate saline solution (0.025 mol L⁻¹, pH 5.0). The ability of the cryogel-Phe column to capture and purify lysozyme was confirmed by high enzymatic activity (1294.17 U ml⁻¹), purity (87.92%), purification factor (11.49), and sulphate-polyacrylamide electrophoresis gel (SDS-PAGE) electrophoresis gel.     

Investigation of water kinetics in zeolite Linde-Type-A crystals by a concentration-swing frequency response

A new concentration-swing frequency response system was developed to evaluate water kinetics in non-binder containing zeolite Linde Type A ( LTA ) crystals with frequencies up to 1 Hz. For commercial micron-sized 3A crystals, the mass transfer rate is too fast to be determined accurately due to reduced sensitivity near the system limits. Larger LTA crystals (~15 μm) were synthesized in house and ion exchanged to three potassium concentrations (0, 48, and 77 wt%) to aid in the accurate determination of mass transfer mechanism and rates. Micropore diffusion with parallel sites, not a surface barrier, described all the data well, consistent with the bimodal distribution of crystal sizes from scanning electron microscope images. The transport diffusivity for water in zeolite 3A crystals near saturated loadings at 25°C is about 1 × 10⁻¹² m²/s, 10 times slower than 4A crystals around 10⁻¹¹ m²/s, both supporting fast micropore diffusion time constants >1 s⁻¹ for micron-sized crystals.     

Plasmonic organic bulk–heterojunction solar cells based on hydrophobic gold nanorod insertion into active layers

In this work, we fabricated plasmonic organic bulk–heterojunction solar cells by inserting hydrophobic gold nanorods (GNRs) into the active layers. Power conversion efficiency was improved from 7.43% to 8.22% because the plasmonic effect of GNRs improved the light harvesting efficiency. Maximum exciton generation rate was increased from 1.35 × 10⁻²⁶ to 1.51× 10⁻²⁶m⁻³ s⁻¹, and the electron mobility was also increased from 8.6 × 10⁻⁵ to 1.5× 10⁻⁴cm⁻² V⁻¹ s⁻¹. As a result, the short circuit current density was improved from 15.5 to 16.7 mA cm⁻²—the dominant reason for performance enhancement. The open circuit voltage and fill factor were improved simultaneously. The plasmonic device showed a highest PCE of 8.43%, indicating that doping GNRs into active layers is a simple and effective way to fabricate high‐performance organic solar cells. © 2017 Wiley Periodicals, Inc. J. Appl. Polym. Sci. 2018 , 135, 45920.     

Increasing DHA and EPA Concentrations Prolong Action Potential Durations and Reduce Transient Outward Potassium Currents in Rat Ventricular Myocytes

The goal of this study was to determine the mechanisms of n-3 polyunsaturated fatty acids (n-3 PUFA) on anti-arrhythmias and prevention of sudden death. The calcium-tolerant Sprague–Dawley rat ventricular myocytes were isolated by enzyme digestion. Effects of docosahexaenoic acid (DHA) and eicosapentaenoic acid (EPA) on action potentials and transient outward potassium currents (I _to) of epicardial ventricular myocytes were investigated using whole-cell patch clamp techniques. Action potential durations (APDs) and I _to were observed in different concentrations of DHA and EPA. APD₂₅, APD₅₀, and APD₉₀ with 0.1 μmol/L DHA and EPA were prolonged less than 15% and 10%. However, APDs were prolonged in concentration-dependent manners when DHA and EPA were more than 1 μmol/L. APD₂₅, APD₅₀, and APD₉₀ were 7.7 ± 2.0, 21.2 ± 3.5, and 100.1 ± 9.8 ms respectively with 10 μmol/L DHA, and 7.2 ± 2.5, 12.8 ± 4.2, and 70.5 ± 10.7 ms respectively with 10 μmol/L EPA. I _to currents were gradually reduced with the increased concentrations of DHA and EPA from 1 to 100 μmol/L, and their half-inhibited concentrations were 2.3 ± 0.2 and 3.8 ± 0.6 μmol/L. The results showed APDs were prolonged and I _to current densities were gradually reduced with the increased concentrations of DHA and EPA. The anti-arrhythmia mechanisms of n-3 PUFA are complex, however, the effects of n-3 PUFA on action potentials and I _to may be one of the important mechanisms.     

Deformation behavior and joining of a MgF2 optical ceramic

Compressive deformation behavior of a polycrystalline magnesium fluoride (MgF₂) ceramic was investigated at temperatures ranging from 760 to 830 °C in an argon atmosphere at strain rates between 2 × 10⁻⁶ and 4 × 10⁻⁵ s⁻¹. Steady-state flow stresses increased with increasing strain rates and ranged between 2 and 38 MPa. Stress exponents of ≈1.4 ± 0.2 were determined at temperatures >760 °C, indicative of a viscous diffusion-controlled deformation mechanism. Activation energy, determined from flow stress as a function of temperature, at a constant strain rate, was ≈476 ± 60 kJ/mol. Self-joining by plastic deformation of MgF₂ was demonstrated at 830 °C at a strain rate of 5 × 10⁻⁶ s⁻¹. The joined samples were characterized by optical transmission measurements and their transmittivity was ≈80% of the unjoined sample in the 2.5–8 μm wavelength range.     

Thin Layer Modelling of Recirculatory Convective Air Drying of Curd (Indian Yoghurt)

Dahi is one of the most popular fermented milk products consumed in India with excellent therapeutic properties. The initial moisture content of dahi is approximately 5.7 kg water kg dry solid⁻¹. The shelf life of dahi is limited and hence the long term storage is possible in the form of dahi powder which can further be used as a base for formulation of health drink mix. Dahi was dried in a laboratory scale recirculatory convective air dryer to a final moisture content of 0.04 kg water kg dry solid⁻¹. Drying characteristics of dahi were investigated under varying conditions of dahi thickness (0.003 m, 0.004 m and 0.005 m) and drying air temperatures (45°C, 50°C and 55°C) and velocities (1.5 m s⁻¹, 2.0 m s⁻¹ and 2.5 m s⁻¹). Different drying models were used to simulate the observed drying data. The mathematical models were compared based on R-square and reduced chi-square values. The drying characteristics were satisfactorily described by Page, modified page, logarithmic and Midilli et al. models. The Midilli et al. model followed by modified page model provided the best representation of data. Effective moisture diffusivity computed on the basis of Fick's law varied between 2.52 × 10⁻¹⁰ m² s⁻¹ and 1.3 × 10⁻⁹ m² s⁻¹ under experimental drying air temperatures and sample thicknesses at air velocity 2.5 m s⁻¹. The temperature and thickness dependence of effective moisture diffusivity was expressed by an Arrhenius type of equation. The equation showed best fit for diffusivity data at 2.5 m s⁻¹ and varying temperatures and sample thickness.     

Synthesis and characterization of PES/PSF/PEG by immersion precipitation for Mediterranean seawater desalination by FO membrane

In the present study, a simple, inexpensive, nontoxic, and environmentally friendly polyethylene glycol (PEG) polymer was used to enhance the hydrophilicity of the forward osmosis (FO) membrane using various PEG concentrations as a pore forming agent in the casting solution of polyethersulfone/polysulfone (PES/PSF) blend membranes. A nonwoven PES/PSF FO blend membrane was fabricated via the immersion precipitation phase inversion technique. The membrane dope solution was cast on polyethylene terephthalate (PET) nonwoven fabric. The results revealed that PEG is a pore forming agent and that adding PEG promotes membrane hydrophilicity. The membrane with 1 wt% PEG (PEG1) had about 27% lower contact angle than the pristine blend membrane. The PEG1 membrane has less tortuosity (which reduces from 3.4–2.73), resulting in a smaller structure parameter (S value) of 277 μm, due to the presence of open pores on the bottom surface structure, which results in diminished ICP. Using 1 M NaCl as the draw solution and distilled water as the feed solution, the PEG1 membrane exhibited higher water flux (136 L m⁻² h⁻¹) and lower reverse salt flux (1.94 g m⁻² h⁻¹). Also, the selectivity of the membrane, specific reverse salt flux, (J_s/J_w) showed lower values (0.014 g/L). Actually, the PEG1 membrane has a 34.6% higher water flux than the commercial nonwoven-cellulose triacetate (NW-CTA) membrane. By means of varied concentrations of NaCl salt solution (0.6, 1, 1.5, and 2 M), the membrane with 1 wt% PEG showed improved FO separation performance with permeate water fluxes of 108, 136, 142, and 163 L m⁻² h⁻¹. In this work, we extend a promising gate for designing fast water flux PES/PSF/PEG FO blend membranes for water desalination.     

Luminescence properties of AgTb(WO4)2 doped with Ce3+: Experimental determination of the Stern-Volmer quenching constant

Scheelite-like AgTb(WO₄)₂ doped Ce³⁺ were synthesized by ceramic method. Efficient characteristic bands of Tb³⁺ were observed in AgTb(WO₄)₂ compounds. However, the presence of Ce³⁺ quenched the emission band of Tb³⁺ which can be caused by metal-to-metal charge transfer between Tb³⁺/Ce³⁺. The quenching is more efficient at high temperature which can be attributed to more overlaps of wave functions of Ce³⁺-W⁶⁺-Tb³⁺ at high temperature. The experimental Stern-Volmer quenching rate constant at room temperature and liquid nitrogen temperature were measured as (376±4)·10⁻³ μs⁻¹ (x content/mol)⁻¹ and (45±4)·10⁻³ μs⁻¹ (x content/mol)⁻¹ respectively. In excitation spectra, evident blue shift of charge transfer band in the case of liquid nitrogen temperature was observed. In addition, the blue shift of CT band also occurred with increasing concentration of Ce³⁺. The shifting of charge transfer band can be interesting to the design of solar cells and tunable excitation sources and detectors.     

Linear Alkylbenzenes Sulfonation: Design of Film Reactor and its Influence on the Formation of Deactivating components

Linear alkylbenzene sulfonic acid (ABSA) is a valuable product of inorganic chemistry that is used to obtain linear alkylbenzene sulfonates. The current method for industrial production of ABSA includes sulfonation of linear alkylbenzene (LAB) with sulfur trioxide in tubular falling film reactors. In this work, we analyze the dependence of the dynamics of the deactivating components formation (tetralines and sulfones) on the structural parameters for a multi-tube film sulfonation reactor. To achieve this, we used an unsteady-state mathematical model that considers the feedstock composition and the change in the reaction medium activity. We determined that the film sulfonation reactor of optimal construction has 40 tubes of diameter of 43 mm. It was revealed that with an increase of the LAB supply to the reactor tube, the mass transfer coefficient also increases. For LAB flows of (95∙10⁻⁵) and (2.86∙10⁻⁵) m³ s⁻¹ per tube, the mass transfer coefficient is (1.73∙10⁻²) m s⁻¹ and (2.08∙10⁻²) m s⁻¹, respectively.     

Magneto-optical,thermal, and mechanical properties of polycrystalline Tb3Al5O12 transparent ceramics

Terbium aluminum garnet (Tb₃Al₅O₁₂, TAG) ceramics have become a promising magneto-optical material owing to the outstanding comprehensive performance, including the magneto-optical, thermal, and mechanical properties. Fine-grained TAG ceramics with high optical quality and mechanical properties have attracted much attention. In this study, TAG ceramics with fine grains and high optical quality are fabricated successfully by a two-step sintering method from co-precipitated nano-powders. After pre-sintered at 1525°C in vacuum and hot isostatic pressed at 1600°C, the in-line transmittance of TAG ceramics reaches 81.8% at 1064 nm, and the average grain size is 7.1 μm. The Verdet constant of TAG ceramics is −179.6 ± 4.8 rad T⁻¹ m⁻¹ at 633 nm and −52.1 ± 1.9 rad T⁻¹ m⁻¹ at 1064 nm, higher than that of commercial Tb₃Ga₅O₁₂ crystals. The thermal conductivity of TAG ceramics is determined from 25 to 450°C, and the result is 5.12 W m⁻¹ K⁻¹ at 25°C and 3.61 W m⁻¹ K⁻¹ at 450°C. A comparison of mechanical properties between large- and fine-grained TAG ceramics fabricated under different conditions is conducted. The fine-grained TAG ceramics possess a bending strength of 226.3 ± 16.4 MPa, which is 9.7% higher than that of the large-grained ceramics. These results indicate that reducing the grain size on the premise of high optical quality helps improve the comprehensive performance of TAG ceramics.     

Effect of processing parameters on microstructure and ablation behavior of SiC/ZrB2 coating for graphite

In this research, a SiC/ZrB₂ coating was produced on graphite by reactive melt infiltration and plasma spraying method. The coating characterization was performed using XRD analysis, electron microscopy equipped with energy dispersive spectrometer (EDS), and supersonic flame ablation test at 2073 K. The results indicated that the dense C/SiC coating with good ablation resistance can be obtained at 1873 K. The coating thickness decreased with increasing infiltration temperature. The results of ablation test showed that by increasing the infiltration temperature and holding time, weight loss and mass ablation rate decreased from 22.63% to 9.83% and 3.63 × 10⁻³ g cm⁻² s⁻¹ to 1.34 × 10⁻³ g cm⁻² s⁻¹, respectively. The results showed that by using the ZrB₂ as outer coating the ablation resistance improved remarkably. The weight loss and mass ablation rates for the SiC/ZrB₂ coating were 12.79% and 1.857 × 10⁻³ g cm⁻² s⁻¹, respectively.     

The decrease of depolarization temperature and the improvement of pyroelectric properties by doping Ta in lead-free 0.94Na0.5Bi0.5TiO3-0.06BaTiO3 ceramics

Ta-doped lead-free 0.94NBT-0.06BT-xTa (x=0.0–1.0%) ceramics were synthesized by a conventional solid-state route. XRD shows that the compositions are at a morphotropic phase boundary where rhombohedral and tetragonal phases coexist. The depolarization temperature (T_d) shifted to lower temperature with the increase of Ta content. The pyroelectric coefficient (p) of doped ceramics greatly enhanced compared with undoped material and reached a maximum of 7.14×10⁻⁴ C m⁻² °C⁻¹ at room temperature (RT) and 146.1×10⁻⁴ C m⁻² °C⁻¹ at T_d at x=0.2%. The figure of merits, F_i and F_v, also showed a great improvement from 1.12×10⁻¹⁰ m v⁻¹ and 0.021 m² C⁻¹ at x=0.0 to 2.55×10⁻¹⁰ m v⁻¹ and 0.033 m² C⁻¹ at x=0.2% at RT. Furthermore, F_i and F_v show the huge improvement to 52.2×10⁻¹⁰ m v⁻¹ and 0.48×10⁻¹⁰ m v⁻¹ respectively at T_d at x=0.2%. F_C shows a value between 2.26 and 2.42 ×10⁻⁹ C cm⁻² °C⁻¹ at RT at x=0.2%. The improved pyroelectric properties make NBT-0.06BT-0.002Ta ceramics a promising infrared detector material.