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Abstract: Li-rich layered oxide is prepared and coated with an AlF3 layer by a chemical deposition method. The as-prepared and AlF3-coated Li-rich materials are characterized by X-ray diffraction (XRD), scanning electron microscopy (SEM), and transmission electron microscopy (TEM). The as-prepared Li-rich oxide has a typical layered structure with the chemical formula of Li(Li0.17Ni0.25Mn0.58)O2, and the AlF3 layer with a thickness of about 5–7nm is coated on the surface of the Li(Li0.17Ni0.25Mn0.58)O2 grains. Galvanostatic charge–discharge tests at various rates show that the AlF3-coated Li(Li0.17Ni0.25Mn0.58)O2 has an obviously enhanced electrochemical performance compared with the as-prepared sample. At 0.2C rate, the AlF3-coated sample provides a large capacity of more than 250mAhg−1. The coulombic efficiency in the initial cycle is improved to 89.5% from 76.4%. At 5C rate, the reversible capacity of the AlF3-coated sample is stable at above 104mAhg−1 after 200 cycles, much higher than that of the as-prepared sample. According to the analysis from electrochemical impedance spectra (EIS), the improvements of the electrochemical performance are mainly attributed to the pre-activation of the Li-rich layered oxide induced by the AlF3 coating and the maintenance of more active sites for the lithium ion intercalation/extraction in the AlF3-coated sample. [Copyright &y& Elsevier]

Abstract: In the current study, in order to elucidate the mechanisms for the favorable effects of lithium nitrate in controlling alkali silica reaction (ASR), vycor glass disk immersion specimens and glass disk–cement paste sandwich specimens were prepared and examined by XRD, SEM and Laser Ablation Induction Coupled Plasma Mass Spectrometry (LA-ICP-MS). Results showed that when glass disk was immersed in only NaOH solution, the glass was attacked by hydroxyl ions but no solid reaction product was found, thus the presence of calcium was essential for the formation of ASR gel. In the presence of lithium, the glass surface was covered by a thick layer of Li–Si crystal. With the addition of Ca(OH)2, the glass surface was completely covered by Li–Si crystal and a lithium-bearing low Ca–Na–(K)–Si gel. These two phases either form a dense matrix with Li–Si crystal serving as the framework, and the gel filling in the void space, or the Li–Si crystal serving as the foundation to completely cover the entire reactive SiO2 surface, and the gel sitting on top of these crystal particles. Hence, the suppressive effects of LiNO3 were attributed to the formation of a layer of Li–Si crystals intimately at the reactive SiO2 particle surface and the formation of Li-bearing low-Ca ASR gel products. The Li-bearing low-Ca ASR gels may have a dense and rigid structure, thus having low capacity to absorb moisture from the surrounding paste, and exhibiting a non-swelling property. [Copyright &y& Elsevier]

Abstract: We investigate thin blend films of phenyl-substituted hexa-peri-hexabenzocoronenes (HBC) with various alkyl side chain lengths ((CH2)n, n=6, 8, 12 and 16)/perylenediimide (PDI). These blends constitute the active layers in bulk-hetero junction organic solar cells we studied recently [1]. Their structural properties are studied by both scanning electron microscopy and X-ray diffraction measurements. The results support the evidence for the formation of HBC donor–PDI acceptor complexes in all blends regardless of the side chain length of the HBC molecule. These complexes are packed into a layered structure parallel to the substrate for short side chain HBC molecules (n=6 and 8). The layered structure is disrupted by increasing the side chain length of the HBC molecule and eventually a disordered structure is formed for long side chains (n>12). We attribute this behavior to the size difference between the aromatic parts of the HBC and PDI molecules. For short side chains, the size difference results in a room for the side chains of the two molecules to fill in the space around the aromatic cores. For long side chains (n>12), the empty space will not be enough to accommodate this increase, leading to the disruption of the layered structure and a rather disordered structure is formed. Our results highlight the importance of the donor–acceptor interaction in a bulk heterojunction active layer as well as the geometry of the two molecules and their role in determining the structure of the active layer and thus their photovoltaic performance. [Copyright &y& Elsevier]

Abstract: Bi3.25Eu0.75Ti3O12 (BET) thin films were deposited on Pt/Ti/SiO2/Si(111) substrates by a metal-organic decomposition method. The effects of annealing temperatures 600–800°C on microstructure, ferroelectric, dielectric and piezoelectric properties of BET thin films were studied in detail. The spontaneous polarization (87.4×10−6 C/cm2 under 300kV/cm), remnant polarization (65.7×10−6 C/cm2 under 300kV/cm), the dielectric constant (992.9 at 100kHz) and the effective piezoelectric coefficient d 33 (67.3pm/V under 260kV/cm) of BET thin film annealed at 700°C are better than those of the others. The mechanisms concerning the dependence of the enhancement d 33 are discussed according to the phenomenological equation, and the improved piezoelectric performance could make the BET thin film a promising candidate for piezoelectric thin film devices. [Copyright &y& Elsevier]