Tape casting of strontium and cobalt doped lanthanum chromite suspensions

Lanthanum chromite (LaCrO₃) is currently the most widely studied material as interconnector layers for solid oxide fuel cells (SOFC). The complexity of microstructures and geometries of SOFC devices, which are usually built-up by lamination of the different constitutive layers, make it necessary a precise control of processing parameters to achieve the desired combination of properties. Much effort has been devoted to the processing of electrodes and electrolytes but the other layers, such as that of interconnecting material, have received scarce attention. This work deals with the preparation and optimisation of the rheological behaviour of concentrated suspensions of Sr- and Co-doped LaCrO₃ and the subsequent tape casting to produce homogeneous thin sheets to be used in the SOFC stack.The starting powder was produced by combustion synthesis from the corresponding nitrates and urea as a fuel, and had a final composition of La_0.80Sr_0.20Cr_0.92Co_0.08O₃. These powders were dispersed in ethanol with commercial copolymers (Hypermer, KD6) to solids loading of up to 58 wt%. The binding system (BS) consisted of a mixture of a binder, polyvinyl butyral-co-vinyl alcohol-co-vinyl acetate (PVA-PVAc), and two plasticizers, polyethyleneglycol (PEG400) and benzylbutylphthalate (BBP). The effect of the binding system content and the binder-to-plasticizer ratio on the tape casting performance and the characteristics of the green and the sintered tapes, were studied, as well as the influence of the casting parameters (casting speed and blades height).     

Novel carbon-ceramic composite membranes with high cation exchange properties for use in microbial fuel cell and electricity generation

Actually, there are different configurations used in microbial fuel cells (MFCs) with presence or absence of an ion exchange membrane between their electrodes. Specifically, MFCs that use membranes have the objective of avoiding the diffusion of oxygen and substrate between the anodic and cathodic compartment, and to achieve a correct transfer of protons from one chamber to another. In this regard, the current study seeks to prepare and characterize new composite membranes using as precursors three types of carbonaceous materials such as bone char, coconut shell activated carbon and bituminous activated carbon and natural clay. The composite membranes of bituminous activated carbon and clay showed more promising specific conductivity (42%) than the one made with pure clay. The physicochemical properties of the membranes and their precursors were elucidated by SEM/EDX analysis, IR spectroscopy, nitrogen adsorption isotherms at 77 K and optical microscopy. Further, membranes performance was assessed using microbial fuel cells (MFCs) where the composite membranes prepared with clay-bituminous carbon reached the highest voltage values (0.95–1.02 V) in open circuits, while that reached a maximum power density of 0.699 W/m³ at a current density of 4.012 A/m³ in closed circuit. This behavior is associated with the high content of silicon and aluminum in bituminous activated carbon, which favored the proper functioning of membranes in the MFCs. Specifically, with this type of cells, energy recovery of 0.0057 kWh/m³ and 0.1322 kWh/kg chemical oxygen demand (COD) removed, which indicates an extra economic income of the order of $0.0025/kg COD. Finally, the produced power was demonstrated in prototypes to power LED and four digital clocks. This novel clay-bituminous activated carbon showed promising cost-effectiveness and sustainable energy generation, which may be suitable for wastewater treatment.     

Selective separation of salicylic acid from aqueous solutions using molecularly imprinted nano-polymer on wollastonite synthesized by oil-in-water microemulsion method

Highly effective molecularly imprinted nano-polymer on wollastonite (nano-WMIP) was prepared by imprinting technique using oil-in-water emulsion polymerization in the presence of salicylic acid (SA) as template. The adsorption behavior of nano-WMIP including adsorption kinetic, isotherms, selective adsorption, recognition, and effects of initial pH, ionic strength, initial concentration, adsorption temperature, and amount of adsorbents were investigated in detail. Moreover, the selective recognition of nano-WMIP was further investigated by HPLC toward analogs of SA. The relative selectivity coefficients for p-HB, MS, and MP were 113.4, 8.049, and 6.239, respectively, showing that much higher selectivity of SA on nano-WMIP was obtained than that of wollastonite-based non-imprinted polymer (nano-WNIP).     

Wear and friction of 6061-T6 aluminum alloy treated by laser shock processing

Laser shock processing (LSP) is becoming an important surface treatment to induce a compressive residual stress field, which improves fatigue and fracture properties of components. In this work, we examine the effect of laser shock processing on the wear and friction behavior of 6061-T6 aluminum alloy. Wear rate and friction coefficient evolution are investigated for different process parameters of LSP. Roll-on-flat tribometer is used with different loading conditions. Hardness and residual stresses are assessed as well. It is observed that wear rate decreases as pulse density increases; this is explained in light of residual stress distribution.     

Development of a monitor to simultaneously measure dissolved ozone and organic matter in ozonated water

A method for measuring both dissolved ozone (DO₃) concentration and UV absorbance was developed adopting ultraviolet (UV) absorption method (Japan Water Works Association (JWWA), 1993a, Japan Water Works Association (JWWA), 1993b) using sodium thiosulfate (Na₂S₂O₃) solution for removing residual ozone in ozonated water. A DO₃ monitor based on this method was tested. This method was proven to be effective from experimental results. The performance of the monitor was examined with continuous ozonated water. As a result, the monitor performed stably during about 2 months, so that both DO₃ concentration and UV absorbance in the ozonated water could be accurately measured. Therefore, the authors have proposed the new aquatic control system with this monitor for ozonation.     

Characterization of local texture in a moderately deformed polycrystalline AlSi-alloy

Polycrystalline material of various grain sizes of AlSi-alloy containing second-phase particles have been deformed at room temperature in axisymmetric compression. The variation in crystallographic orientation in the as-deformed material was obtained by the Electron Back Scattered Pattern (EBSP) technique in SEM. “Random” and cumulative long range misorientation gradients have been quantified within the matrix (M) and at heterogeneities such as the grain boundary (GB), the triple line region (TL) and in the vicinity of large second phase particles (P) in material compressed to equivalent plastic strains of 0.2 and 0.4. It is shown that the misorientation gradient increases differently in different regions with increasing strain. Maximum values were found in regions expected to be more strained than average in order to accomodate imposed constraint from neighbouring grains or from the presence of large second phase particles. An important feature of the deformed structure seems to be the cumulative rotation of the lattice about an axis close to the 〈111〉-axis in regions with large misorientations.     

Mixed-solvothermal synthesis and characterization of triangular prism-like Y2O3

In this paper, it was demonstrated that Y₂O₃ microprisms could be prepared by a mixed-solvothermal method with triethylene tetramine as precipitator and sequent heat treatment process. X-ray diffraction (XRD), scanning electron microscopy (SEM), transmission electron microscopic (TEM) and high-resolution transmission electron microscopic (HRTEM) were used to characterize the products. The height of the Y₄O(OH)₉(NO₃) microprisms is about 1.2 μm and the length of the side of the bottom surface is about 0.6 μm. It was found that the composition of solvent, dosage of triethylene tetramine, reaction time and reaction temperature had great effect on the morphologies of the final products. The as-obtained product via solvothermal process, monoclinic yttrium oxide hydroxide nitrate, Y₄O(OH)₉(NO₃), could convert to Y₂O₃ with the same morphology after annealing at high temperatures. Eu³⁺ doped Y₂O₃ microprisms were also prepared and their photoluminescence (PL) properties were investigated. This method may be applied to prepare other rare earth oxides with complex structures.     

Diversity in nutritional composition of wild jack bean (Canavalia ensiformis L. DC) seeds collected from south India

Nine accessions of the wild jack bean (Canavalia ensiformis L. DC) seeds collected from nine different locations of south India were analysed for proximate composition and mineral profiles. The major findings of the study were as follows: crude protein ranged from 28.9 to 35.0%, crude lipid 3.4–4.7%, crude fibre 7.0–10.7%, ash 3.0–5.8%, carbohydrates 46.1–54.5% and energy levels 1469–1574 kJ 100 g⁻¹ DM. Significant (P<0.05) diversity was observed in crude protein and carbohydrate contents among the accessions collected from different locations based on analysis of variance (ANOVA) analysis. Potassium was the most abundant mineral, which ranged from 634 mg 100 g⁻¹ in Dasukuppam accession to 1017 mg 100g⁻¹ in Valacode accession. Sodium and magnesium levels are generally low with mean values of 63 and 250 mg 100 g⁻¹, respectively. In the present study, in all minerals, significant diversity was observed among the accessions collected from different locations.     

GH80A经强流脉冲电子束改性后的高温氧化行为研究

目的 提高燃气轮机叶片材料镍基高温合金GH80A的抗高温氧化性能。方法 利用强流脉冲电子束（High-Current Pulsed Electron Beam, HCPEB）技术对GH80A合金进行表面处理。研究HCPEB辐照前后GH80A的微观结构变化及在850 ℃恒温氧化后的氧化动力学行为及氧化机制。利用光学显微镜、X射线衍射仪和扫描电子显微镜对HCPEB诱发的微观结构和氧化产物进行了表征。结果 HCPEB辐照后,GH80A合金表面发生熔化,形成厚约3 μm的重熔层,重熔层内形成大量的位错滑移,且晶粒明显得到细化。850 ℃高温氧化实验结果表明,氧化100 h后,原始样品氧化增重最大,生成的氧化膜较厚,且存在大量裂纹,所生成的Cr2O3发生了挥发,导致氧化膜疏松多孔,基体发生了严重的内氧化。HCPEB辐照20次后,样品氧化增重最小,100 h氧化后形成的氧化膜主要由外层TiO2和内层Cr2O3构成。外层连续致密的TiO2抑制了保护性氧化膜Cr2O3的挥发,因此生成的Cr2O3氧化膜连续、致密、无剥落,对基体起保护作用。结论 HCPEB辐照后,GH80A合金的抗高温氧化性能明显提升,20次辐照样品的抗高温氧化性能最佳。