Development of a prototype thermodynamic database for Nd-Fe-B permanent magnets.

For the Nd-Fe-B permanent magnets, a prototype thermodynamic database of the 8-element system (Nd, Fe, B, Al, Co, Cu, Dy, Ga) was constructed based on literature data and assessed parameters in the present work. The magnetic excess Gibbs energy of the Nd2Fe14B compound was reassessed using thoroughly measured heat capacity data. The Dy-Nd binary system was reassessed based on formation energies estimated from ab initio calculations. The constructed database was applied successfully for estimations of phase equilibria during the grain boundary diffusion processes (GBDP) and the reactions in the hydrogenation decomposition desorption recombination (HDDR) processes.

Computational thermodynamics and microstructure simulations to understand the role of grain boundary phase in Nd-Fe-B hard magnets.

To control the coercivity of Nd hard magnets efficiently, the thermal stability of constituent phases and the microstructure changes observed in hard magnets during thermal processes should be understood. Recently, the CALPHAD method and phase-field method have been recognized as promising approaches to realize phase stability and microstructure developments in engineering materials. Thus, we applied these methods to understand the thermodynamic feature of the grain boundary phase and the microstructural developments in Nd-Fe-B hard magnets. The results are as follows. (1) The liquid phase is a promising phase for covering the Nd2Fe14B grains uniformly. (2) The metastable phase diagram of the Fe-Nd-B ternary system suggests that the tie line end of the liquid phase changes drastically depending on the average composition of Nd. (3) The Nd concentration in the grain boundary phase can reach 100 at% if the volume fraction of the grain boundary phase is constrained. (4) The effect of Cu addition to the Nd-Fe-B system on the microstructural morphology is reasonably modeled based on the phase-field method. (5) The morphology of the liquid phase can be controlled using phase separation in the liquid phase and the grain size of the Nd2Fe14B phase.

Self-healing by design: universal kinetic model of strength recovery in self-healing ceramics.

We propose a new theoretical kinetic model of strength recovery by oxidation-induced self-healing of surface cracks in composites containing a healing agent (HA). The kinetics is a key parameter in the design of structural components that can self-heal the damage done in service. Based on three-dimensional (3D) observations of crack-gap filling, two crack-gap filling models, i.e., a bridging model and a tip-to-mouth filling model, are incorporated in the proposed kinetic model. These crack-gap filling models account for the microstructural features of the fracture surfaces, crack geometry, and oxidation kinetics of the healing-agent. Hence, the minimum and maximum remaining flaw sizes in the healed crack gaps are estimated for various healing temperatures, times, and oxygen partial pressure conditions. Further, the nonlinear elastic fracture mechanics suitable for small-sized remaining flaws, together with a statistical analysis of the original Weibull-type strength distribution, enables the prediction of upper and lower strength limits of the healed composites. Three sintered alumina matrix composites containing silicon carbide (SiC)-type HAs with various volume fractions and shapes, together with monolithic SiC ceramics, are considered. The strength of the healed-composite predicted by our model agrees well with the experimental values. This theoretical approach can be applied to HAs other than SiC and enables the design of self-healing ceramic components for various applications.

Gibbs energy functions with the vacancy complexes in the Al-Cu binary system.

The Gibbs energy functions of the phases in the Al-Cu binary system are taken from the CALPHAD-type thermodynamic assessment (Witusiewicz et al., 2004; Ansara et al., 1998) [1], [2], where the effect of the monovacancy (Va), divacancy (VaVa) and Va-solute atom pair are taken into account based on the formulation (Abe et al., In press). The divacancy is modeled as an associate, VaVa, in the FCC solid solution. The contributions from the Va-solute pair are included through the ternary excess Gibbs energy term. Using the Gibbs energy functions provided in this data article, the fractions of the monovacancies and divacancies, even in various metastable conditions, can be calculated. Since the Gibbs energy functions and phase descriptions are written in the TDB (Thermodynamic DataBase) format, one can use this file with various thermodynamic software packages, such as OpenCalphad [3] etc.

A Novel Design Approach for Self-Crack-Healing Structural Ceramics with 3D Networks of Healing Activator.

Self-crack-healing by oxidation of a pre-incorporated healing agent is an essential property of high-temperature structural ceramics for components with stringent safety requirements, such as turbine blades in aircraft engines. Here, we report a new approach for a self-healing design containing a 3D network of a healing activator, based on insight gained by clarifying the healing mechanism. We demonstrate that addition of a small amount of an activator, typically doped MnO localised on the fracture path, selected by appropriate thermodynamic calculation significantly accelerates healing by >6,000 times and significantly lowers the required reaction temperature. The activator on the fracture path exhibits rapid fracture-gap filling by generation of mobile supercooled melts, thus enabling efficient oxygen delivery to the healing agent. Furthermore, the activator promotes crystallisation of the melts and forms a mechanically strong healing oxide. We also clarified that the healing mechanism could be divided to the initial oxidation and additional two stages. Based on bone healing, we here named these stages as inflammation, repair, and remodelling stages, respectively. Our design strategy can be applied to develop new lightweight, self-healing ceramics suitable for use in high- or low-pressure turbine blades in aircraft engines.

Circularly Polarized Luminescence of Chiral Pt(pppb)Cl (pppbH=1-pyridyl-3-(4,5-pinenopyridyl)benzene) Aggregate in the Excited State.

We prepared enantiomers of chiral Pt(II) complexes, Pt(pppb)Cl and Pt(pppb)CN (pppbH=1-pyridyl-3-(4,5-pinenopyridyl)benzene), and measured their CPL (circularly polarized luminescence) spectra for excimer and trimer emission. The contribution of the pinene moiety to CPL was considerably low for the π-π* emission of the monomer but large for MMLCT (metal-metal-to-ligand charge-transfer) of the excimer and trimer which had a helical structure induced in a face-to-face stacking fashion. The trimer CPL for (+)-Pt(pppb)Cl was larger in intensity than that of excimer CPL; on the other hand, that for (+)-Pt(pppb)CN was opposite in sign compared with that of excimer CPL. We conclude that differences in the excited-state structure of the aggregate between Pt(pppb)Cl and Pt(pppb)CN account for the variation in the CPL spectra. By the aid of TD-DFT calculations it was predicted that the dihedral angle θ(Cl-Pt-Pt-Cl) was 50-60° or 110-140° for Pt(pppb)Cl aggregates and 160° for Pt(pppb)CN aggregates.

Hydrazone-palladium-catalyzed allylic arylation of cinnamyloxyphenylboronic acid pinacol esters.

Allylic arylation of cinnamyloxyphenylboronic acid pinacol esters 3, which have arylboronic acid moiety and allylic ether moiety, using a hydrazone 1d-Pd(OAc)2 system proceeded and gave the corresponding 1,3-diarylpropene derivatives 4 with a phenolic hydroxyl group via a selective coupling reaction of the π-allyl intermediate to the boron-substituted position of the leaving group.

Luminescence change by the solvent of crystallization, solvent reorganization, and vapochromism of neutral dicyanoruthenium(II) complex in the solid state.

The "solvent effect" on the solid-state luminescence of a neutral complex, [Ru(dbb)(2)(CN)(2)] (dbb = 4,4'-di-tert-butyl-2,2'-bipyridine), was presented. The crystals of this complex showed a variety of luminescence color from orange to dark-red, depending on the acceptor number of the solvent included in the crystal as a solvent of crystallization. The luminescence change was very similar to the solvatochromism in solution, which was attributed to the local donor-acceptor interaction between the CN group and the solvent molecules. The dynamic shift observed in the transient emission spectrum of the crystalline powder was accounted for by the solvent molecule reorganization. X-ray crystallography of [Ru(dbb)(2)(CN)(2)].3(CH(3))(2)CO showed the complex molecule having an approximate C(2) symmetry and very weak interactions between the acetone molecules and the CN groups. A three-dimensional network constructed by acetone molecules was observed in the hydrophobic space consisting of t-butyl groups in dbb ligands. A thin film of the complex showed vapochromic behavior such that the luminescence changed depending on the solvent of crystallization. This suggests a capability for organic molecule discrimination using the complex in the solid state.

Luminescence color change of a platinum(II) complex solid upon mechanical grinding.

The mechanochemical behavior of Pt(5dpb)Cl (5dpbH = 1,3-di(5-methyl-2-pyridyl)benzene) was investigated in terms of solid-state luminescence. The yellow luminescence of the crystalline complex changed to orange when grinding into fine powder on a glass substrate with a spatula. A broad emission band, which was not detected for the crystal, was observed at around 670 nm for the powder. The powder X-ray diffraction (XRD) pattern was the same as that calculated from X-ray crystallographic data of the single crystal. A broad band appeared within 100 ns after laser excitation accompanied by quenching of the s(pi,pi*) emission of Pt(5dpb)Cl, which was then weakened with decreasing temperature and disappeared below 120 K. The phenomenon was very similar to the excimer formation observed in solution. A related complex, Pt(dpb)Cl (dpbH = 1,3-di(2-pyridyl)benzene), also exhibited luminescent mechanochromism. However, the broad emission that appeared upon grinding still remained at 77 K, and XRD showed that the ground sample of Pt(dpb)Cl was amorphous.

[2,6-Bis(5-methyl-2-pyridyl)phenyl-kappa(3)N,C(1),N']chloridoplatinum(II).

In the title compound, [Pt(C(18)H(15)N(2))Cl], the Pt(II) centre adopts a distorted square-planar coordination geometry due to the pincer-type monoanionic N-C-N tridentate ligand. The planar complexes stack via pi-pi interactions to form two-dimensional accumulated sheets. This packing pattern is in contrast to that in related pincer-type N-C-N complexes, which exhibit a one-dimensional columnar stacking.

Tuning of luminescence spectra of neutral ruthenium(II) complexes by crystal waters.

Neutral ruthenium(II) complexes [RuLL'(CN)2] (L, L' = bpy, dmb, dbb; bpy = 2,2'-bipyridine, dmb = 4,4'-dimethyl-2,2'-bipyridine, dbb = 4,4'-tert-butyl-2,2'-bipyridine) were prepared, and the luminescence characteristics of the complexes in the solid state were measured. The luminescence was tuned by crystal waters included in the crystals; for example, [Ru(dbb)2(CN)2] x 2H2O, [Ru(dbb)2(CN)2] x H2O, and [Ru(dbb)2(CN)2] emit luminescence at 640, 685, and 740 nm, respectively.