No abstract

Spherical (S) and tesseral (T) tensor operators (TOs) have been extensively used in, for example, EMR and optical spectroscopy of transition ions. To enable a systematic review of the published tables of the operators and their matrix elements (MEs) we have generated the relevant tables by computer, using Mathematica programs. Our review reveals several misprints/errors in the major sources of TTOs—the conventional Stevens operators (CSOs—components ) and the extended ones (ESOs—all q) for rank k = 2,4, and 6—as well as of some STOs with . The implications of using incorrect operators and/or MEs for the reliability of EMR-related programs and interpretation of experimental data are discussed. Studies of high-spin complexes like Mn12 (S = 10) and Fe19 (S = 33/2) require operator and ME listings up to k = 2S, which are not presently available. Using the algorithms developed recently by Ryabov, the generalized ESOs and their MEs for arbitrary rank k and spin S are generated by computer, using Mathematica. The extended tables enable simulation of the energy levels for arbitrary spin systems and symmetry cases. Tables are provided for the ESOs not available in the literature, with odd k = 3,5, and 7 for completeness; however, for the newly generalized ESOs with the most useful even rank k = 8,10, and 12 only, in view of the large listings sizes. General source codes for the generation of the ESO listings and their ME tables are available from the authors.

Nanophase materials are promising alternative implant materials in tissue engineering. Here we report for the first time the large-scale direct growth of nanostructured bioactive titanates on three-dimensional (3D) microporous Ti-based metal (NiTi and Ti) scaffolds via a facile low temperature hydrothermal treatment. The nanostructured titanates show characteristics of 1D nanobelts/nanowires on a nanoskeleton layer. Besides resembling cancelous bone structure on the micro/macroscale, the 1D nanostructured titanate on the exposed surface is similar to the lowest level of hierarchical organization of collagen and hydroxyapatite. The resulting surface displays superhydrophilicity and favors deposition of hydroxyapatite and accelerates cell attachment and proliferation. The remarkable simplicity of this process makes it widely accessible as an enabling technique for applications from engineering materials treatment including energy-absorption materials and pollution-treatment materials to biotechnology.

The capability of fast charge and fast discharge is highly desirable for the electrode materials used in supercapacitors and lithium ion batteries. In this article, we report a simple strategy to considerably improve the high rate capability of Co 3 O 4 nanowire array electrodes by uniformly loading Ag nanoparticles onto the surfaces of the Co 3 O 4 nanowires via the silver-mirror reaction. The highly electrically conductive silver nanoparticles function as a network for the facile transport of electrons between the current collectors (Ti substrates) and the Co 3 O 4 active materials. High capacity as well as remarkable rate capability has been achieved through this simple approach. Such novel Co 3 O 4 -Ag composite nanowire array electrodes have great potential for practical applications in pseudo-type supercapacitors as well as in lithium ion batteries.

Olivine-type LiFePO 4 has recently become one of the most important cathode materials for Li-ion batteries, because of its superior capacity retention, thermal stability, nontoxicity, safety, and potentially low cost. Furthermore, LiFePO 4 shows remarkable tolerance to overcharge and discharge, and, in this respect, is noticeably better than the commercial cathode materials currently used in Li-ion batteries. 1À4 The advantages of traditional lithium-ion batteries (i.e., high energy density, design flexibility) coupled with the excellent safety features of olivine phosphates, make LiFePO 4 one of the most promising electrode materials of choice for the hybrid electric vehicles (HEVs) and even electric vehicles (EVs). However, bulk, micrometer-sized LiFePO 4 suffers from a poor rate capability in part because of its inherent low electronic conductivity (∼10 À9 À10 À10 S cm À1 ) and possibly due to its one-dimensional (1D) Li þ ionic conductivity. 5,6