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A high-efficiency diffusion-multiple approach was employed to map the phase diagram of the Nb–Cr–Ti ternary system which is critical for the design of niobium silicide-based composites. These composites have high potential as a replacement for Ni-base superalloys for jet engine applications. The formation of the Laves phase and alloying with Ti are critical for the high oxidation resistance of the composites and the Nb–Cr–Ti system serves as the base for understanding the Laves phase formation and Ti alloying. Three isothermal sections at 1000, 1150 and 1200 °C were constructed from the results obtained from diffusion multiples using scanning electron microscopy, electron probe microanalysis, and electron backscatter diffraction. The results help to define the relative stability of the C15 and C36 Laves phases in the Nb–Cr–Ti ternary system.

A multicomponent diffusion mobility database for the Ni-rich fcc phase [2002 Cam] is evaluated by comparing diffusion simulations to two experimental multicomponent Ni-base superalloy diffusion couples: Ni/Rene-88 and IN718/Rene-88. The diffusion simulations use composition-dependent thermodynamic and diffusion quantities within a finite difference code to simulate single-phase and multiphase planar layers. The multiphase layers consist of a matrix phase and a disperse phase. The calculated composition profiles, interdiffusion coefficients, phase fraction profiles, and location of Kirkendall porosity are compared with experimental results. To treat diffusion in the IN718 alloy, iron and carbon are added to the existing diffusion mobility database using previous assessment work and new assessments of Fe-Al and Fe-Co.

A high-efficiency diffusion-multiple approach was employed to determine the phase diagram of the Nb–Cr–Si ternarysystem which is critical for the design of niobium silicide-based in situ composites. These composites have highpotential as a replacement for Ni-base superalloys for jet engine applications. The formation of the Nb(Cr,Si) 2 Lavesphase is beneficial to the high oxidation resistance of the composites and the Nb–Cr–Si system serves as the base forunderstanding the Laves phase formation. The results clearly demonstrate the applicability of the diffusion-multipleapproach in determining such complex phase diagrams as Nb–Cr–Si which contains 14 phases. Two isothermal sectionsat 1000 and 1150 °C were constructed from the results obtained from diffusion multiples using scanning electronmicroscopy (SEM), electron probe microanalysis (EPMA), and electron backscatter diffraction (EBSD). Three ternarycompounds, CrNbSi, (Cr,Nb) 6 Si 5 and (Cr,Nb) 11 Si 8 , were observed at both temperatures, and the C14 Laves phase ofthe Cr–Nb binary system was stabilized by Si to lower temperatures.2003 Published by Elsevier Ltd on behalf of Acta Materialia Inc.

The temperatures of airfoil surfaces in advanced turbine engines are approaching the limits of nickel-based superalloys. Innovations in refractory metal-intermetallic composites (RMICs) are being pursued, with particular emphasis on systems based on Nb-Si and Mo-Si-B alloys. These systems have the potential for service at surface temperatures >1350 °C. The present article will review the most recent progress in the development of Nb-silicide-based in-situ composites for very-high-temperature applications. Nb-silicide-based composites contain high-strength silicides that are toughened by a ductile Nb-based solid solution. Simple composites are based on binary Nb-Si alloys; more complex systems are alloyed with Ti, Hf, Cr, and Al. In higher-order silicide-based systems, alloying elements have been added to stabilize intermetallics, such as Laves phases, for additional oxidation resistance. Alloying schemes have been developed to achieve an excellent balance of room-temperature toughness, high-temperature creep performance, and oxidation resistance. Recent progress in the development of composite processing-structure-property relationships in Nb-silicide-based in-situ composites will be described, with emphasis on rupture resistance and oxidation performance. The Nb-silicide composite properties will be compared with those of advanced Ni-based superalloys.

A high-efficiency diffusion-multiple approach was employed to map the phase diagram of the Nb–Al–Si ternary system which is very valuable for the design of niobium silicide-based composites. These composites have high potential as a replacement for Ni-base superalloys for jet engine applications. Aluminum is an alloying element for these composites, thus the Nb–Al–Si phase diagram, especially solubility of Al in Nb5Si3, is important information for the composite design. An isothermal section at 1000 °C was constructed from the results obtained from a diffusion multiple using scanning electron microscopy (SEM) and electron probe microanalysis (EPMA). A ternary phase Nb3Si5Al2 was observed. The solubility data of Al in αNb5Si3 and NbSi2 as well as Si solubility in Nb3Al, Nb2Al and NbAl3 were obtained. The new isothermal section helps to judge the reliability of the existing literature results and to add new data to the Nb–Al–Si phase equilibria.

This article reviews the most recent progress in the development of Nb-silicide-based in situ composites for potential applications in turbine engines with service temperatures of up to 1350°C. These composites contain high-strength Nb silicides that are toughened by a ductile Nb solid solution. Preliminary composites were derived from binary Nb-Si alloys, while more recent systems are complex and are alloyed with Ti, Hf, W, B, Ge, Cr, and Al. Alloying schemes have been developed to achieve an excellent balance of room-temperature toughness, fatigue-crack-growth behavior, high-temperature creep performance, and oxidation resistance over a broad range of temperatures. Nb-silicide-based composites are described with emphasis on processing, microstructure, and performance. Nb silicide composites have been produced using a range of processing routes, including induction skull melting, investment casting, hot extrusion, and powder metallurgy methods. Nb silicide composite properties are also compared with those of Ni-based superalloys.

DADB synthesis: The diammoniate of diborane (DADB) was synthesized in a new metathesis reaction between the diammoniate of monochloroborane and potassium borohydride in liquid ammonia. (1)H and (11)B NMR spectra of DADB are reported. The stability in THF was examined by variable-temperature (11)B NMR spectroscopy.

Phase diagram and thermochemistry data of the binary Al-Hf system are briefly reviewed, and those literature data are used to optimize a consistent thermodynamic description for all the phases. The liquid, face-centered cubic (fcc), body-centered cubic (bcc), and close-packed hexagonal (cph) phases are treated as disordered solutions, whereas all the intermetallic phases are taken as stoichiometric compounds. The model-calculated phase diagram and the thermodynamic properties are in good agreement with most of the experimental data.

Thermodynamic calculations on complex, multi-component alloys are becoming more common in metallurgical research. They are now used on a daily basis in industrial laboratories such as the GE Research Center. They have proven to be of great assistance in the development of new alloys, and in the selection of processing conditions for existing or new alloys. This paper presents an evaluation of the usefulness of the CALPHAD calculations for Ni-base superalloys by showing case study validations and examples of their use.

This paper seeks to illustrate the power of a diffusion-multiple approach in efficient mapping of phase diagrams and materials properties for multicomponent alloy systems, showing that many ternary phase diagrams can be mapped from a single diffusion multiple. The diffusion profiles also allow evaluation of diffusion coefficients. Moreover, the composition variations created in the diffusion multiple allow efficient mapping of hardness and elastic modulus as a function of composition and phases. Examples will be given for precious metal systems currently used in high-temperature sensors. For these systems, the diffusion-multiple approach also produces a tremendous cost saving compared to making heats of various alloys, preparing samples, and measuring properties. This approach uses several microanalytical techniques, such as electron probe microanalysis, electron backscatter diffraction, and instrumented nanoindentation.

Combinatorial methods are high-efficiency methods to create large composition “libraries” of materials, for example, continuous composition variations, and test those compositions systematically in parallel for specific properties of interest, in contrast to the time-consuming one-composition-at-a-time approach. These methods have captured the attention of the materials industry with the promise of providing new discoveries “faster, better, and cheaper.” However, in the academic community, combinatorial methods often meet with less enthusiasm, perhaps due to the perception of combinatorial methodology as an Edisonian approach to science. The facts are quite to the contrary. In addition to impressive successes arising from the application of combinatorial methods to materials discovery, results coming out of systematic high-throughput investigations of complex materials phenomena (which would be too time-consuming or expensive to undertake) provide data leading to improvement in theories and models of materials chemistry and physics. Indeed, combinatorial methods provide a new paradigm for advancing a central scientific goal—the fundamental understanding of structure–property relationships of materials behavior.

Thermodynamic calculations, which are being performed on a daily basis in industrial laboratories such as the General Electric Corporate Research and Development Center, have proven to be of great assistance in the development of new alloys and the selection of processing conditions for existing or new alloys. This article presents an evaluation of the state-of-the-art ofthat capability for nickel-base superalloys.

Attempts to synthesize solvent-free MgB_(12)H_(12) by heating various solvated forms (H_2O, NH_3, and CH_3OH) of the salt failed because of the competition between desolvation and dehydrogenation. This competition has been studied by thermogravimetric analysis (TGA) and temperature-programmed desorption (TPD). Products were characterized by IR, solution- and solid-state NMR spectroscopy, elemental analysis, and single-crystal or powder X-ray diffraction analysis. For hydrated salts, thermal decomposition proceeded in three stages, loss of water to form first hexahydrated then trihydrated, and finally loss of water and hydrogen to form polyhydroxylated complexes. For partially ammoniated salts, two stages of thermal decomposition were observed as ammonia and hydrogen were released with weight loss first of 14 % and then 5.5 %. Thermal decomposition of methanolated salts proceeded through a single step with a total weight loss of 32 % with the release of methanol, methane, and hydrogen. All the gaseous products of thermal decomposition were characterized by using mass spectrometry. Residual solid materials were characterized by solid-state 11B magic-angle spinning (MAS) NMR spectroscopy and X-ray powder diffraction analysis by which the molecular structures of hexahydrated and trihydrated complexes were solved. Both hydrogen and dihydrogen bonds were observed in structures of [Mg(H_2O_6B_(12)H_(12)]⋅6 H_2O and [Mg(CH_3OH)_(6)B_(12)H_(12)]⋅6 CH_3OH, which were determined by single-crystal X-ray diffraction analysis. The structural factors influencing thermal decomposition behavior are identified and discussed. The dependence of dehydrogenation on the formation of dihydrogen bonds may be an important consideration in the design of solid-state hydrogen storage materials.

The thermodynamic parameters of the Al-Zr binary system can be very useful for the development of Zr-Al based amorphous and nanocrystalline materials. Phase diagram and thermochemistry data, especially the enthalpy of mixing of the liquid phase and the standard enthalpy of formation for the intermetallic compounds, are employed to optimize a consistent thermodynamic description for all the phases. The liquid, fcc, bcc, and hcp phases are treated as disordered solutions, while all the intermetallic phases are taken as stoichiometric compounds. The calculated phase diagram and thermochemistry data agree well with most of the experimental values reported in the literature.

A methodology is developed which extends the combinatorial approaches to structural materials research and development. This high-efficiency methodology employs diffusion couples and “diffusion multiples” to create large variations (libraries) of compositions in bulk samples for fast and systematic surveys of bulk properties. These composition libraries coupled with microanalytical techniques such as electron probe microanalysis, electron backscatter diffraction analysis, and nanoindentation tests can be used for efficient surveys of phases, equilibria, diffusion coefficients, precipitation kinetics, properties, and composition–phase–property relations (such as solution hardening and strengthening effect) for accelerated design of multicomponent alloys.

Scanning electron microscopy (SEM), transmission electron microscopy (TEM), and thermodynamic calculations were employed to study the phase stability and phase precipitation in the Ni-based superalloy Nimonic 263. The major precipitates at temperatures below 900 °C were gamma-prime and eta (Ni3Ti), with the eta phase starting to precipitate at the expense of the gamma-prime phase after prolonged annealing. The eta precipitates had a thin-plate morphology and formed a regular Widmanstatten pattern. They had a fixed orientation relationship with the fcc matrix. Very fine particles of M23C6 also precipitated intragranularly, and they had a cube-on-cube orientation relationship (OR) with the fcc matrix. Intragranular precipitation of a very fine cylindrical MC carbide was also observed. Grain-boundary (GB) precipitates were mostly M23C6, with a small fraction of MC. Based on the experimental results, a time-temperature-transformation (TTT) diagram was constructed. The experimental results were compared to thermodynamic predictions, and good agreement was observed. The calculations correctly predicted almost all the major phases and their stability temperature ranges. The experimental and calculation results, together, depict a clearer picture of phase stability in the alloy.

The high-efficiency combinatorial approaches used for parallel synthesis and screening of large composition libraries of functional materials inspire the possibility of rapid screening of structural materials. Because bulk properties are required for structural materials, the existing approaches for solid-state functional materials are difficult to apply to structural materials screening. Here the author describes a different methodology - the ''diffusion multiple'' - that generates large, multicomponent composition variations (libraries) in bulk samples through thermal interdiffusion. The coupling of diffusion multiples with micro-scale composition-phase-property measurements constitutes a powerful combinatorial approach for structural materials research and development. (orig.)

Transmission electron microscopy (TEM) was employed to study the phase precipitation in Hastelloy X heat-treated at 750, 850, and 900°C for 26 and 100 h. Phase identification was made by electron micro-diffraction and energy dispersion spectroscopy (EDS) X-ray micro-chemical analysis. In addition to the fcc matrix, four different precipitation phases were observed: M6C, M23C6, σ, and μ. The current observations were combined with literature results to build a time–temperature-transformation (TTT) diagram for this alloy. This TTT diagram depicted time–temperature regimes where various phases were formed; thus, it provided information about the general precipitation kinetics for the alloy.

A mnemonic scheme is presented to help recall the equations in classical thermodynamics that connect the four state variables (temperature, pressure, volume, and entropy) to the four thermodynamic potentials (internal energy, Helmholtz free energy, enthalpy, and Gibbs free energy). Max Born created a square to help recall the thermodynamic equations. The new scheme here separates the Max Born square into two squares, resulting in easier recalling of several sets of equations, including the Maxwell equations, without complicated rules to remember the positive or negative signs.

A transmission electron microscope (TEM) was employed to study the ordering and phase separation processes in Au-40 at. pct Ni and Au-50 at. pct Ni alloys in order to test for the possible existence of a transient long-range-order (LRO) phenomenon within a disordered miscibility gap. An L10 LRO phase was found in the Au-50 at. pct Ni alloy when spinodally decomposed specimens were reannealed at ∼490°C on a TEM hot stage. This observation, together with the literature results, indicates that a transient LRO did exist in the Au−Ni system, although it appeared during a reversion process. Attempts to find the L10 and L12 LRO phases during decomposition processes of a single-phase homogeneous solid solution were unsuccessful, except in very thin sections of the TEM foils. Elastic strain energy relaxation was employed to explain the experimental observations. Time-temperature—transformation (TTT) diagrams for the two Au−Ni alloys were constructed based on the TEM characterization. In bulk-annealed samples, only spinodal decomposition and discontinuous precipitation structures were observed.

Transmission electron microscopy (TEM) was employed to study the microstructure and transformation kinetics of a Cu–15Ni–8Sn (wt%) alloy. Five different transformation products were observed: a modulated structure resulting from spinodal decomposition; a DO22 ordered structure; an L12 ordered structure; grain boundary and intragranular γ (DO3) precipitates; and discontinuous γ precipitates. It was found that spinodal decomposition occurred during the early stage of decomposition below ∼500°C. DO22 ordering appeared after spinodal decomposition, and L12 ordering appeared after DO22 ordering. Discontinuous precipitation took place at a very late stage of the decomposition process. A time–temperature transformation (TTT) diagram was established on the basis of extensive TEM characterization. Five separate C-curves were found for the five transformation products. This TTT diagram is very helpful in clarifying the confusion and inconsistency in the literature concerning the precipitation process in the alloy. This work is one of the first experimental studies which report that spinodal decomposition can take place before ordering. It also provides evidence for the coexistence of both DO22 and L12 long range order (LRO) structures in the alloy.

A high-efficiency combinatorial approach has been applied to rapidly build the database of composition-dependent elastic modulus and hardness of the Ti-Ta and Ti-Zr-Ta systems. A diffusion multiple of the Ti-Zr-Ta system was manufactured, then annealed at 1173K for 1800h, and water quenched to room temperature. Extensive interdiffusion among Ti, Zr and Ta has taken place. Combining nanoindentation and electron probe micro-analysis (EPMA), the elastic modulus, hardness as well as composition across the diffusion multiple were determined. The composition/elastic modulus/hardness relationship of the Ti-Ta and Ti-Zr-Ta alloys has been obtained. It was found that the elastic modulus and hardness depend strongly on the Ta and Zr content. The result can be used to accelerate the discovery/development of bio-titanium alloys for different components in implant prosthesis.

Pure NH3BH3 is prepared at the 100 g scale by displacement reactions of either NH3 and Me2S·BH3 with 94% yield, or NH3 and Ph-NMe2·BH3 with 91% yield, with both reactions performed in toluene at room temperature.

The existing literature has been examined and rationalized to test the general validity of a number of generally accepted concepts concerning the overall transformation kinetics of ferrous alloys. Considerable confusion exists because of the mixup of the continuous cooling kinetics with the isothermal transformation kinetics. Therefore, these two topics are discussed separately. For the continuous cooling process, the following topics are examined: (1) the suppressibility of the martensite transformation at high cooling rates; (2) the cooling rate dependence of M s (martensite transformation-start temperature) and B s (bainite transformation-start temperature); (3) the formation conditions of lath martensite and twinned martensite; and (4) the various features of continuous cooling transformation (CCT) diagrams. For the isothermal transformation process, the following issues are examined: (1) the isothermal transformation kinetics of martensite; (2) the relationship between athermal transformation of martensite and isothermal transformation of martensite; (3) the general features of time-temperature-transformation (TTT) diagrams; (4) the validity of the “isothermal martensite” concept; and (5) the definition of M s and B s for isothermal transformations. Among the main conclusions are: (1) twinned martensite can be formed in all steels, even in pure iron and low-carbon and/or low-alloy steels; (2) isothermal transformation of martensite always follows C-curve kinetics; and (3) B s and M s for isothermal transformations are different from those obtained from cooling transformations. Comparison of literature results with the present assessment of isothermal B s and M s is made and good agreement is observed. The weakness of using TTT diagrams to analyze the continuous cooling kinetics is also discussed. Moreover, (metastable) product diagrams for austenite decomposition are established for both the continuous cooling process and the isothermal transformation process in order to develop a clearer paradigm for both processes.

The experimental data on the kinetics of the fcc to hcp phase transformation in pure cobalt have been summarized (in Figs. 1 and 2) and analyzed in conjunction with the recent finding of a metastable 9R martensite structure by Kajiwara et al. [12,13]. From the observed transformation kinetics, it is predicted that there should exist another martensitic structure for cobalt in addition to the e martensite and the 9R (e″) martensite, i.e., there are three kinds of martensite. Each martensite has a separate Ms temperature, which is identified as 390 ± 5 °C (e), 370 ± 8 °C (e′) and 330 ±15 °C (e″), respectively. The absence of this unidentified e′ martensite in the ultra-fine particles of Kajiwara et al. does not exclude its existence in other forms of pure cobalt. Grain size and impurity effects on the transformation kinetics are also discussed and used to explain the experimental observations in both bulk and ultra-fine particle cobalt.

Growth associated protein 43 (Gap43) is a neuron-specific phosphoprotein, which plays critical role in axon growth and synapses functions during neurogenesis. Here we identified two transcription start sites (TSSs) of the mouse Gap43 gene designated as a proximal site at +1, and a distal TSS at -414. RT-qPCR data reveal that the transcripts from +1 increase 10-fold on day-1 post-all-trans retinoic acid (RA) treatment, reached a peak value at day-4 and gradually reduced. By contrast, the distal TSS directs a late, remarkably sharp increase of the transcripts from the day-5 on. An intense signal of Gap43 at the neurites and neural network is determined by the efficient transcription of the distal promoter as shown in Northern blot and RT-qPCR assay. In addition, the targeting of p300 in combination with a differential enrichment of Brm to Brg1 change at the distal promoter region of the gene is induced under RA treatment. The over hundreds of GA rich stretches and the GAGAG elements located between the two TSSs may take parts in the differential transcription of the two TSSs of the Gap43. Our findings provide the first evidence on the identification and differential transcription of the two TSSs of the mouse Gap43 gene, and the preferential distribution of their protein products in the specific stages of RA induced P19 differentiation. These data suggest the efficient transcription of the distal promoter of Gap43 is an important mark for the transition of P19 cells from the progenitor stage into neuronal differentiation.

The title compound is prepared by a metathesis reaction between unsolvated NaB3H8 and NH4Cl in liquid ammonia at -78 °C (30 min, 95% yield).

The general characteristics of phase transformation kinetics during cooling and heating are introduced. It is demonstrated that the cooling process always depresses the phase boundaries away from equilibrium and towards lower temperatures; similarly, the heating process always shifts the phase boundaries to higher temperatures. Moreover, the larger the cooling or heating rate, the larger the discrepancy. According to this observation, the reliability of cooling and heating data (irrespective of the methods used to determine them: electrical resistance, dilatometry, etc.) for phase diagram assessments is discussed. The principle for correct assessment of metastable phase information is also briefly introduced. It is pointed out that each kind of metastable phase has its own transformation-start temperature, Ts (Ms, etc.), during cooling. More specifically, each kind of martensite has its own Ms. Examples are shown for Fe-Ni, Fe-Mn, and Ti-Cr alloys.

Unsolvated NaB3H8 is prepared by reaction of Na/Hg amalgam with THF·BH3 at room temperature for 3 d (

A simple and efficient way to synthesize unsolvated sodium octahydrotriborate has been developed. This method avoids the use of dangerous starting materials and significantly simplifies the reaction setup, thus enabling convenient large-scale synthesis. The structure of the unsolvated compound has been determined through powder X-ray diffraction.

A new ambient-temperature, catalyst-free reaction between ammonia borane and tetrahydrofuran borane produces aminodiborane via the formation of a dihydrogen bond and subsequent molecular hydrogen elimination. The facile synthesis of aminodiborane will make this long-sought active chemical reagent readily available for both inorganic and organic reactions. From aminodiborane, an inorganic butane analogue, NH(3)BH(2)NH(2)BH(3), was prepared, and its single-crystal structure displayed a gauche rather than an anti form conformation.

The asymmetric unit of the title salt, 2NH4+·B10H102−·1.5H2O or (NH4)2B10H10·1.5H2O, (I), contains two B10H102− anions, four NH4+ cations and three water mol­ecules. (I) was converted to the anhydrous compound (NH4)2B10H10, (II), by heating to 343 K and its X-ray powder pattern was obtained. The extended structure of (I) shows two types of hydrogen-bonding interactions (N—H⋯O and O—H⋯O) and two types of dihydrogen-bonding interactions (N—H⋯H—B and O—H⋯H—B). The N—H⋯H—B dihydrogen bonding forms a two-dimensional sheet structure, and hydrogen bonding (N—H⋯O and O—H⋯O) and O—H⋯H—B dihydrogen bonding link the respective sheets to form a three-dimensional polymeric network structure. Compound (II) has been shown to form a polymer with the accompanying loss of H2 at a faster rate than (NH4)2B12H12 and we believe that this is due to the stronger dihydrogen-bonding inter­actions shown in the hydrate (I).

To explore the regulatory effect of the GAGA element-related protein (GRP) on the Drosophila GAGA-dependent promoter activity in Jurkat cells.Drosophila GAGA (dGAGA) factor (dGAF), GRP, and either the chloramphenicol acetyltransferase (CAT) reporter plasmid driven by the GAGA element-containing promoter of ftz gene or its mutant GAGA control were selectively co-transfected into Jurkat cells. Promoter activity analyses were performed by analyzing the RNA expression of the CAT in a real-time-RT PCR system, with pRC-CMV-betaGal co-transfected with the CAT reporter as a transfection efficiency control. Electrophoretic mobility shift assays (EMSA) were carried out to examine the binding profile of Jurkat nuclear extracts with a biotin labeled probe-containing dGAGA.In Jurkat cells, GRP, either singly or combined with dGAF, elevated the activity of wild type dGAGA-containing ftz promoter dose-dependently in certain range. However, when the level of GRP was excessively high, it reduced or even fully inhibited the promoter activity of the ftz gene. On the contrary, either GRP or dGAF could not activate the ftz promoter with mutant GAGA. EMSA profile showed a specific band composed of the GAGA element and its binding proteins from Jurkat cells.Human GAGA element-binding proteins exist in Jurkat cells. Its may either directly regulate the gene via GAGA elements or mediate the biphasic regulation of relevant gene in a GRP dose-dependent way.

A brief rationalisation is made of the isothermal decomposition kinetics of supercooled austenite in steels. From the experimental evidence of the past several decades, it is concluded that each type of isothermal decomposition product, i.e. grain boundary allotriomorphs, Widmanstatten ferrite (and cementite), pearlite, upper bainite, lower bainite, lath martensite, and twinned martensite, has its own independent C-curve in time–temperature–transformation (TTT) diagrams. Special emphasis is placed on the isothermal transformation kinetics of martensite. It is demonstrated that martensite transformation follows C-curve kinetics in isothermal conditions; this is a general rule and holds for all steels. The reason why most experimental TTT diagrams fail to display separate C-curves for different products is briefly explained. A temperature–composition–product (TCP) diagram is constructed for Fe–C alloys (plain carbon steels) to depict the general pattern of the decomposition process and to display th...

The asymmetric unit of the title salt, 2NH(4)(+).B(10)H(10)(2-).1.5H(2)O or (NH(4))(2)B(10)H(10).1.5H(2)O, (I), contains two B(10)H(10)(2-) anions, four NH(4)(+) cations and three water molecules. (I) was converted to the anhydrous compound (NH(4))(2)B(10)H(10), (II), by heating to 343 K and its X-ray powder pattern was obtained. The extended structure of (I) shows two types of hydrogen-bonding interactions (N-H...O and O-H...O) and two types of dihydrogen-bonding interactions (N-H...H-B and O-H...H-B). The N-H...H-B dihydrogen bonding forms a two-dimensional sheet structure, and hydrogen bonding (N-H...O and O-H...O) and O-H...H-B dihydrogen bonding link the respective sheets to form a three-dimensional polymeric network structure. Compound (II) has been shown to form a polymer with the accompanying loss of H(2) at a faster rate than (NH(4))(2)B(12)H(12) and we believe that this is due to the stronger dihydrogen-bonding interactions shown in the hydrate (I).

The ammonia complex of magnesium borohydride Mg(BH4)2·2NH3 (I), which contains 16.0 wt % hydrogen, is a potentially promising material for hydrogen storage. This complex was synthesized by thermal decomposition of a hexaaammine complex Mg(BH4)2·6NH3 (II), which crystallizes in the cubic space group Fm3m with unit cell parameter a = 10.82(1) A and is isostructural to Mg(NH3)6Cl2. We solved the structure of I that crystallizes in the orthorhombic space group Pcab with unit cell parameters a = 17.4872(4) A, b = 9.4132(2) A, c = 8.7304(2) A, and Z = 8. This structure is built from individual pseudotetrahedral molecules Mg(BH4)2·2NH3 containing one bidentate BH4 group and one tridentate BH4 group that pack into a layered crystal structure mediated by N−H···H−B dihydrogen bonds. Complex I decomposes endothermically starting at 150 °C, with a maximum hydrogen release rate at 205 °C, which makes it competitive with ammonia borane BH3NH3 as a hydrogen storage material.

To investigate the effect and immuoregulative mechanisms of NK1.1(+) cells on the development of experimental autoimmune myasthenia gravis (EAMG).The NK1.1(+) cells were depleted by intraperitoneal (i.p.) administration of anti-mouse NK1.1 mAb to C57BL/6 mice. Mice were immunized subcutaneously with AChR in CFA. The incidence and severity of EAMG was determined according to the Lennon disease symptoms grading. IFN-gamma and IL-4 in MNCs culture medium were measured by ELISA. AChR IgG of serum was measured by radioimmunoassay. In some experiments, the anti-IFN-gamma mAb was injected (i.p.) to neutralize IFN-gamma.The onset of EAMG was delayed and the severity was decreased obviously in NK1.1(+) cell-depleted mice. However, depletion of NK1.1(+) cells after immunization had no impact on the development of EAMG. Depletion of NK1.1(+) cells could significantly reduce the expression of AChR-specific antibody as well as the production of IFN-gamma. The development of EAMG and production of AChR specific Ab in NK1.1(+) cell-depleted mice were decreased obviously after treating with anti-IFN-gamma antibody.NK1.1(+) cells are involved in the early EAMG, and NK1.1(+) cells could enhance the production of IFN-gamma released by AChR-specific T cells as well as the AChR-specific antibodies, which may enhance the outcome of EAMG.

We have determined the structures of two phases of unsolvated Mg(BH4)2, a material of interest for hydrogen storage. One or both phases can be obtained depending on the synthesis conditions. The first, a hexagonal phase with space group P61, is stable below 453 K. Upon heating above that temperature it transforms to an orthorhombic phase, with space group Fddd, stable to 613 K at which point it decomposes with hydrogen release. Both phases consist of complex networks of corner-sharing tetrahedra consisting of a central Mg atom and four BH4 units. The high-temperature orthorhombic phase has a strong antisite disorder in the a lattice direction, which can be understood on the basis of atomic structure.

Publisher Summary The never-ending nature of phase diagram determination comes from several factors: the time and resource constraints dictate the focus of a particular research to a region of the phase diagram of immediate interest; the availability of equipment at the research facility dictates the type of measurements one can perform; some subtle crystal structure changes may be missed by a research group without advanced facilities or relevant knowledge; certain measurement procedures may miss subtle electronic, magnetic, or ordering transitions; and specimen purity and conditions may introduce discrepancies that need further investigation to sort out. This chapter discusses several topics on phase diagrams, including the ever-increasing interplay of modeling and experiment, phase diagrams for functional materials, high-throughput phase diagram determination, and the low-temperature phase diagrams. A recommended list of further reading materials is also provided in the chapter along with a list of recent compilations of phase diagrams.

Publisher Summary This chapter focuses on the importance of understanding the basic phase transformation kinetics in determination and assessment of phase diagrams. The cooling process always shifts the phase transformation temperature away from the equilibrium phase boundary toward lower temperatures, and the opposite is true for the heating process. The chapter, using examples, shows that the shift can be very pronounced for solid–solid phase equilibrium transitions at low temperatures, and the heating data are no better than the cooling data if equilibrium is not reached at low temperatures before heating. The chapter discusses the difficulty associated with slow decomposition of some high-temperature phases, especially intermetallic compounds and presents some examples. The slow decomposition kinetics is often manifested as a widening of the composition region of a stoichiometric phase or line compound in a phase diagram. The chapter emphasizes that caution must be taken in the determination of phase diagrams at relatively low temperatures.

The cover shows a SEM backscattered electron image of a cross-sectional thermal barrier coating (TBC) system on the bottom and its correspondent thermal conductivity image on the top. The thermal conductivity image was collected using a novel time-domain thermoreflectance technique with a femtosecond laser and it reveals the conductivity variation in the TBC system, especially in the bond coat. The thermal conductivity value of each point/pixel has an accuracy of 8 % and a spatial resolution of ∼ 3 mm. More on thermal condcutivity imaging can be found in the article by J.-C. Zhao et al. on page 622.

Extended abstract of a paper presented at Microscopy and Microanalysis 2013 in Indianapolis, Indiana, USA, August 4 – August 8, 2013.

Unlike functional materials, which most often are used for one specific physical or chemical property, structural materials often need to satisfy simultaneously several different properties such as strength, ductility, modulus, fracture toughness, environmental resistance, etc. In addition, many structural materials undergo several different processes such as casting, forging, rolling, and the like before they are used in the final product. Thus it is not very practical to “screen” for structural materials directly. Instead, high-efficiency approaches can be used to map critical properties and data to accelerate the design of structural materials.