A double-layer composite electrode based on SrSc0.2Co0.8O3−δ perovskite with improved performance in intermediate temperature solid oxide fuel cells

Dual-layer composite electrodes consisting of a layer adjoining to an Sm_0.2Ce_0.8O_1.9 (SDC) electrolyte composed of 70 wt.% SrSc_0.2Co_0.8O_3−δ + 30 wt.% Sm_0.2Ce_0.8O_1.9 (SScC + SDC composite) and a second layer composed of 70 wt.% SrSc_0.2Co_0.8O_3−δ + 30 wt.% Sm_0.5Sr_0.5CoO_3−δ (SScC + SmSC composite) were fabricated and investigated as potential cathodes in intermediate temperature solid-oxide fuel cells. Thermo-mechanical compatibility between the two electrode layers and between the electrode and the electrolyte were examined by SEM, XRD and EIS. After sintering, no clear boundary between SScC + SDC and SScC + SmSC layers was observable by SEM. The repeated thermal cycling didn’t induce the delamination of the electrode from the electrolyte nor the formation of cracks within the electrode. As a result, stable electrode performance was achieved during thermal cycling and long-term operation. Symmetric cell tests demonstrated that the dual-layer electrode with a ∼10-μm SScC + SDC layer and a ∼50-μm SScC + SmSC layer (SScC + SDC/SScC + SmSC (1:5)) had the lowest electrode-polarization resistance among those tested. Anode-supported fuel cells with an SDC electrolyte and SScC + SDC/SScC + SmSC (1:5) cathode were fabricated. Peak power density as high as 1326 mW cm⁻² was achieved at 650 °C, which was higher than for similar fuel cells with a single-layer SScC + SDC or an SScC + SmSC composite electrode.     

Lanthanum samarium oxalate — its growth and structural characterization

Lanthanum samarium oxalate (LSO) single crystals are grown in silica gels by the diffusion of a mixture of aqueous solutions of lanthanum nitrate and samarium nitrate into the test tube having the set gel impregnated with oxalic acid. Tabular crystals of LSO having well defined hexagonal basal planes are observed at different depths inside the gel. LSO crystals grown by this method are colourless and transparent. Laue transmission X-ray diffraction pattern of LSO reveals well defined spots with two-fold symmetry along the horizontal axis. Thermogravimetric analysis (TGA) and differential scanning calorimetry (DSC) support that LSO loses water around 120°C, and CO and CO₂ around 350–450°C. The infrared (IR) absorption spectrum of LSO establishes the presence of oxalate (C₂ O₄)²⁻ ions. Energy dispersive X-ray analysis (EDAX) confirms the presence of La and Sm in the sample. X-ray photoelectron spectroscopic (XPS) studies of LSO confirm the presence of La and Sm in their respective oxide states. An empirical structure for LSO has been proposed on the basis of these findings.     

Sr transfer factors between different levels in the trophic chain in two dams of Douro river (Portugal)

The study of Sr transfer in the trophic chain, was undertaken in the dams of Miranda do Douro and Régua belonging respectively to the upper and middle streams of Douro river.

This study was carried out during 17 months, between January 1985 and May 1986, and Sr was measured in water, phytoplankton (seston) zooplankton, specimens belonging to two benthic families (Chironomidae and Tubificidae) and in representatives of four species of fish of Cyprinidae family: Chondrostoma polylepis—boce; Cyprinus carpio—carp; Carassius auratus—goldfish; Barbus bocagei—barbel.

The results obtained showed the existence of strong seasonal variation in the levels of Sr in water and in the different levels of the food chain.

The minimum values in water correspond to the rainy seasons, when the flow is higher, identifying a clear dilution effect. In fish, where these variation are slighter, the amount of Sr is proportional to the size of the body (constant concentration), possibly because the greatest part of this element is found on skeleton pieces (bones and scales).

All the studied organisms present high Sr concentration factors from the water. However, taking into account annual averages, a great accumulation of Sr in the food chain, from the plankton to the fish itself, is not found, meaning that no important phenomena of biomagnification to Sr concentrations between prey and predator exist. The higher transfer factors (TFs) from benthic animals to fish are only due to the absence of skeleton in those animals. An estimation of TFs from benthic animals to the soft edible parts of fish show that no biomagnification exists.

The determination of TFs between food-chain levels during the different seasons, together with other physico-chemical, biological and hydrological data presented, is essential to the development of protective measures against radioactive threats.     

Sol-Gel Glass-Encapsulated Crown Ethers for the Separation and Preconcentration of Strontium from Acidic Media

Extraction chromatography employing an inert polymeric support impregnated with a crown ether (typically, 4,4’,(5’)-di-(tert-butylcyclohexano)-18-crown-6 (DtBuCH18C6)), either neat (i.e., undiluted) or as a solution in 1-octanol, has previously been shown to provide an effective means for the isolation of radiostrontium from a variety of sample types for subsequent determination. In this study, sol-gel chemistry has been employed to prepare sorbents in which DtBuCH18C6 is encapsulated in a silica matrix. The resultant materials have been evaluated for their ability to retain strontium ion and compared to a commercially available extraction chromatographic (EXC) resin. Certain of the new materials are shown to provide uptake efficiencies comparable to those obtained with the commercial resins, although unless a porogen is employed, the kinetics of strontium uptake are significantly slower. In contrast to conventional EXC materials, however, strontium uptake by DtBuCH18C6-loaded glasses does not increase in proportion to the amount of extractant present, indicating that not all of the crown ether present is available for interaction with the metal ion.     

石膏及石膏制品中锶含量测定方法的研究

锶是石膏及石膏制品中常见的杂质元素,锶的同位素中锶85、锶89和锶90等都具有放射性且半衰期较长,对人体有较大危害。传统的测定锶含量方法不适宜石膏及石膏制品中锶含量的测定;采用电感耦合等离子原子发射光谱(ICP-AES)法来测定石膏及制品中锶含量,具有快速、准确、重现性好的特点,符合检验检疫行业要求。     

La_2O_3/LDPE复合材料非等温结晶性能研究

利用差示扫描量热仪(DSC)考察了氧化镧(La2O3)/低密度聚乙烯(LDPE)复合材料的非等温结晶行为。通过Jeziorny法、Ozawa法及莫志深法研究了复合材料的非等温结晶动力学。结果表明:在添加La2O3后,LDPE成核速率降低,结晶度下降,晶体粒径分布变宽。在非等温结晶动力学分析中,Jeziorny法lg[-ln(1-Xt)]～lgt关系曲线在结晶前期和中期具有较好的线性关系,结晶后期产生较大偏离;Ozawa法并不适用;而莫志深法适用于该体系的研究,表明La2O3的加入使LDPE结晶速率增大。     

锶渣混凝土在农村公路中的应用

通过室内强度试验结果与现场施工条件确定了锶渣混凝土的水泥用量,阐述了锶渣混凝土面层施工的主要工序,并说明了锶渣混凝土面层施工中的关键性控制要点,以促进其在农村公路中的应用和推广。     

Exploration of 1D-2D LaFeO3/RGO S-scheme heterojunction for photocatalytic water splitting

Sustainable energy innovation is spearheading the way to achieve decarbonisation through commercially viable and highly competitive renewable technologies for green hydrogen. Photocatalytic water splitting has received global attention, as it promotes the direct conversion of solar energy to chemical energy and hydrogen production. Lanthanum orthoferrite (LaFeO₃) has been selected due to its narrow bandgap perovskite-oxides (ABO₃) type nature, low cost and high chemical stability but it is limited with fast charge recombination. To circumvent its constraint of fast charge recombination, an efficient graphene-based nanocomposite has been prepared by employing reduced graphene oxide (RGO) nanosheets as charge separators for visible light driven photocatalytic water splitting. Here, we present a thorough physical and spectroscopic characterization of the Lanthanum orthoferrite/Reduced Graphene oxide (LaFeO₃/RGO) nanocomposites, and investigate its photocatalytic and photoelectrochemical performance. The photocurrent density of the nanocomposites demonstrated ∼21 times higher in comparison to pure LaFeO₃. The as-prepared nanocomposites have been successfully used as photocatalysts for H₂ generation through water reduction under visible light. A significant enhancement in H₂ generation has been recorded for nanocomposites (∼82 mmol g⁻¹ h⁻¹) as compared to that of bare LaFeO₃ (∼9 mmol g⁻¹ h⁻¹) which is among the highest values obtained using noble-metal-free graphene-based photocatalytic nanocomposites. This work offers a facile approach for fabricating highly efficient 1D-2D heterostructure for photocatalysis application.     

包覆量对铝酸锶复合包覆效果的影响

目的对铝酸锶进行复合包覆处理,以提高荧光粉的抗水解性能。方法采用液相水解法在铝酸锶表面包覆SiO2/Al2O3膜,并对膜层进行耐水性、发光性能测试及形貌分析,研究包覆量对包覆效果的影响。结果包覆量对包膜效果有着重要的影响。包覆量太低,荧光粉的耐水性能受到限制,很容易发生水解;包覆量太高,会影响荧光粉的发光性能,发光亮度降低。结论要想得到包膜效果较好的产品,SiO2和Al2O3占铝酸锶的质量百分比最好控制在5%左右。     

Microstructure and biocorrosion behaviors of solution treated and as-extruded Mg–2.2Nd–xSr–0.3Zr alloys

Mg–2.2Nd–xSr–0.3Zr alloys (x=0, 0.4 and 0.7, mass fraction, %) were prepared by gravity casting. Solution treatment was conducted on the as-cast alloys to homogenize microstructure, and hot extrusion was subsequently conducted. Microstructure was observed using an optical microscope and a scanning electron microscope. Biocorrosion behaviors of the alloy in simulated body fluid were analyzed by mass loss, hydrogen evolution and Tafel polarization experiments. The results show that the amount of residual eutectic phase of the solution treated alloys increases with increasing Sr addition, and the grains are significantly refined after hot extrusion. The corrosion resistance of the solution treated alloys deteriorates apparently with increasing Sr addition, while the corrosion resistance of the as-extruded alloys is improved with Sr addition. Nevertheless, the biocorrosion behavior of the as-extruded alloys obtained by Tafel polarization shows different trends from those obtained by the other two methods.