Raman active E2 modes in aluminum nitride films

The vibrational spectrum of AlN thin films has been studied in recent years by theoretical and experimental methods, but there is still a lack of full knowledge of the Raman shift of the active E₂ modes of this material. Early work by Carlone et al. [1] has indicated that the E₂ modes of AlN deposited on Si occur at frequencies of 303cm^-1 and 426cm^-1. In the present study, Raman spectra of AlN deposited by magnetron sputtering on polished Si, quartz and BK7 substrates and also the Raman spectrum of pure Si, were compared to show that these peaks can actually be assigned as Raman peaks of Si, instead of AlN Raman peaks. We show that the Raman lines at 240cm^-1 and 650cm^-1 are the true AlN E₂ Raman peaks in agreement with calculated and experimental works reported in the literature that indicate the occurrence of the low and high E₂ Raman modes of AlN in the ranges (228-252)cm^-1 and (631-665)cm^-1, respectively.     

Hardenability Improvement Mechanisms and Hardenability-Controlling Factors in Steels With Combined Mo–B Addition

Metallurgical and Materials Transactions A - To elucidate the hardenability improvement mechanisms and hardenability-controlling factors in low-carbon (C) steels with the combined addition of...     

Enhanced Li-ion conductivity of strontium doped Li-excess garnet-type Li7+xLa3-xSrxZr2O12

The mechanism underlying the enhancement of the conductivity of Li₇La₃Zr₂O₁₂ (LLZO), an oxide-based solid electrolyte that contains excess Li, was experimentally investigated through subvalent cation substitution. We prepared Sr-substituted Li-rich LLZO with high conductivity of the order of 10⁻⁴ S/cm by using a solid-state method. We investigated the mechanism underlying the conductivity enhancement via detailed structural analysis through Sr K-edge X-ray absorption near edge spectroscopy and X-ray diffraction and neutron powder diffraction analyses. The results suggested that the conductivity enhancement is due to the change in Li⁺ arrangement caused by the incorporation of excess Li into the LLZO lattice.     

Bandgap Tunable Oxynitride LaNb2O7–xNx Nanosheets

Bandgap tunable lanthanum niobium oxynitride [LaNb₂O_7-xN_x]^(1+x)− nanosheet is prepared by the delamination of a Ruddlesden−Popper phase perovskite oxynitride via ion−exchange and two−step intercalation processes. The lanthanum niobium oxynitride nanosheets have a homogeneous thickness of 1.6 nm and exhibit a variety of chromatic colors depending on the nitridation temperature of the parent-layered oxynitride. The bandgap energy of the nanosheets is determined by ultraviolet photoemission spectroscopy, Mott–Schottky, and photoelectrochemical measurements and is found to be tunable in the range of 2.03–2.63 eV. Furthermore, the oxide/oxynitride superlattice structures are fabricated by face−to−face stacking of 2D crystals using oxynitride [LaNb₂O_7-xN_x]^(1+x)− and oxide [Ca₂Nb₃O₁₀]⁻ nanosheets as building blocks. Moreover, the superlattices-like restacked oxynitride/oxide nanosheets hybrid exhibits unique proton conductivity and dielectric properties strongly influenced by the oxynitride nanosheets and enhanced photocatalytic activity under visible light irradiation.     

Power factor control for inverters under high penetration of distributed generation

The paper proposes a method to select a power factor for an inverter of distributed power generation systems to keep appropriate voltage of a power system with the high penetration of inverter-interfaced generation. The increase of inverter-interfaced power sources, such as wind and photovoltaic power generation, arouses concerns on the voltage fluctuations in a power system. While constant power factor control of an inverter has been studied as a means to stabilize the voltage of a power system, there still remains room to improve the control. The proposed method in the paper selects the power factor based on the R/X ratio of the looking-back impedance into the interconnected power system. By normalizing the related variables, a general formula is derived for the power factor, and the resultant relationship between the apparent power and voltage of an inverter becomes identical irrespective of the R/X ratio with the control. Sample studies show that, by operating an inverter with the power factor, voltage fluctuations are effectively suppressed even for a power system with the high penetration of inverter-interfaced generation.     

Tetraphenylporphyrin Enters the Ring: First Example of a Complex between Highly Bulky Porphyrins and a Protein**

Tetraphenylporphyrin (TPP) is a symmetrically substituted synthetic porphyrin whose properties can be readily modified, providing it with significant advantages over naturally occurring porphyrins. Herein, we report the first example of a stable complex between a native biomolecule, the haemoprotein HasA, and TPP as well as its derivatives. The X-ray crystal structures of nine different HasA-TPP complexes were solved at high resolutions. HasA capturing TPP derivatives was also demonstrated to inhibit growth of the opportunistic pathogen Pseudomonas aeruginosa. Mutant variants of HasA binding FeTPP were shown to possess a different mode of coordination, permitting the cyclopropanation of styrene.