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Among the Li-ion conducting inorganic materials, lithium lanthanum zirconate (LLZO) is believed to possess good chemical stability against Li metal and hence considered to be a promising solid electrolyte for Li-ion batteries. However, systematic sets of studies conducted here at regular intervals during storage of Al-doped LLZO (cubic garnet) sintered pellets in ambient atmosphere have raised serious concerns over their structural/mechanical stability/integrity upon exposure to air. Spontaneous cracking/disintegration/pulverization of LLZO pellets takes place after about three weeks of exposure, primarily due to formation of La2Zr2O7 in the LLZO bulk; as found to be thermodynamically feasible at room temperature upon reaction with CO2/moisture. Steep increase in La2Zr2O7 content coincides with the spontaneous cracking/disintegration. Estimation suggests that internal stresses associated with the formation of La2Zr2O7 from LLZO can be high enough to cause spontaneous fracture. This mandates the development/fabrication/usage of solid-state cells using LLZO under stringent controls against exposure to atmospheric species.

High temperature tensile flow behavior of aluminum-boron carbide (Al-B4C) composites of 0, 5 and 15% B4C, hot rolled to similar to 88% with intermediate annealing at 350 degrees C, was investigated by constant initial strain rate (CIS) ((epsilon) over dot = 1 x 10(-2)s(-1)) test technique at 500 degrees C and strain rate jump ((epsilon) over dot = 5 x 10(-5) - 1 x 10(-2)s(-1)) test technique over the temperature range of 400-500 degrees C. In the as-cast condition, the flow stresses obtained between CIS and strain rate jump test techniques were found to be significantly different at 500 degrees C. The strain rate sensitivity index (m) was found to be similar to 0.1 over (epsilon) over dot = 1 x 10(-4) - 1 x 10(-2)s(-1) for all the composites in both as-cast as well as hot rolled condition. Tensile elongations were found to be 0.36 in both as-cast and hot rolled aluminum, whereas the same reduced in Al-5% B4C composite to 0.35 and 0.27, respectively. The values of activation energy (Q) for deformation of rolled aluminum and Al-5% B4C composite were determined to be 194.2 and 73.4 kJ/mol, respectively. The microstructural examination, using SEM and EBSD techniques, revealed cavitation in aluminum upon differential strain rate test, and grain refinement upon rolling, which increased later during tensile test.

Microstructure evolution after solutionizing and ageing treatment of cast AZ80 Mg alloy were investigated using optical and scanning electron microscopy. Effect of these treatments on grain size, beta-Mg17Al12 intermetallic phase, mechanical behavior, and flow asymmetry were investigated. The initial continuous network of beta-phase found to be reduced after solutionizing. The dissolution of beta-phase and simultaneous grain growth are found to be interrelated. Mechanical properties including yield strength, maximum strength (ultimate compressive strength), and maximum strain attainable in compressive found almost twice than the corresponding values obtained in tension. The asymmetry in compressive and tensile properties is found to decrease with grain size at certain solutionizing duration. Particular heat treatment found to offer best combination of tensile compressive flow properties in AZ80 Mg alloy. Aging under certain conditions found to minimize the strength asymmetry.

Stress corrosion crack growth of a rare earth containing Mg-Mn hot rolled alloy was studied using compact tension and circumferential notch tensile specimens employing constant load in 0.1 N NaCl solution saturated with Mg(OH)(2). Circumferential notch tensile specimens satisfied plane strain conditions; Log crack velocity versus stress intensity plots yielded slope of 0.5 and 1 for stage I region and threshold stress intensity of 10 and 13 MPa m(1/2) for circumferential notch tensile and compact tension specimens respectively. Fractography showed transgranular features involving hydrogen in stress corrosion cracking. (C) 2013 Elsevier Ltd. All rights reserved.

This work compares microstructural and strength properties of ultra-fine grained Al-2.5Mg alloy produced by multi-axial forging in a channel die at room and liquid nitrogen temperatures. The two ultra-fine grained microstructures after total equivalent strain of 23 exhibited similar grain sizes and orientation spread but significantly different respective strengths at room temperature. The difference in the strengths has been attributed to the higher dislocation densities in samples pressed at liquid nitrogen temperature. Dislocation densities were measured on the basis of average misorientations within grains measured using electron-back scattered diffractions. (C) 2013 Elsevier B.V. All rights reserved.

Structural and magnetization studies were carried out on Dy1-xYxCo5 [x = 0, 0.2, 0.4, 0.6, 0.8, 1] compounds which crystallize in the hexagonal CaCu5-type structure. Lattice parameters and unit-cell volume increase with Y concentration. Large thermomagnetic irreversibility between the field-cooled and the zero-field cooled magnetization data has been observed in all the compounds, which has been attributed to the domain wall pinning effect. Temperature dependence of magnetization data shows that except DyCo5 and YCo5, all the compounds show spin reorientation transitions in the range of 5-300 K. The spin reorientation temperature decreases from 266 K for x=0.2 to 100 K for x=0.8. Powder x-ray diffractograms of the magnetically aligned samples show that DyCo5 has planar anisotropy at room temperature whereas all the other compounds possess axial anisotropy. The spin reorientation transition has been attributed to a change in the easy magnetization direction from the ab-plane to the c-axis, as the temperature is increased. The anisotropy field and the first order anisotropy constant are found to be quite high in all the compounds except DyCo5. The magnetic properties have been explained by taking into account the variations in contributions arising from the rare earth and transition metal sublattices., Comment: 12 pages, 7 figures

The sintering behavior of titanium-titanium nitride nanocomposite powders has been investigated by dilatometry. Micron-sized titanium powders of average particle size of similar to 12 mu m and nano sized titanium nitride powders of average particle size of similar to 50 nm were used to produce two compositions of Ti-8 wt%TiN and Ti-15 wt%TiN by physical mixing and ultrasonification. Dilatometry was carried out by constant rate of heating (10 degrees C/min) to various temperatures in the range of 650-1250 degrees C followed by isothermal holding for I h. The effect of nano TiN dispersion on the sintering onset temperature, linear shrinkage, shrinkage rate, activation energy, and microstructure of titanium was investigated. The sintering of titanium-titanium nitride nanocomposites was found to be influenced by the sintering between the Ti-Ti contacts (self diffusion), Ti-TiN contacts (diffusion of N into Ti), TiN-TiN contacts, the role of oxygen as well as the alpha-beta transformation in titanium. (C) 2006

In recent years there has been considerable interest in the dominant mass transport mechanisms operating during sintering of nanocrystalline powders. The present investigation deals with these mass transport mechanisms in nanocrystalline titanium powders. Sintering studies have been carried out by dilatometry of the powder compacts using a constant rate of heating (CRH) and employing model equations for the initial sintering portion. The shrinkage values obtained by heating the specimens at a constant rate of heating (CRH) to various temperatures were analyzed using Young and Curlers equations and a model proposed by Johnson and Berrin. Based on the analysis of experimental data, mechanisms are proposed for the initial sintering of nanocrystalline titanium powders. (c) 2006

First-principles, density-functional based electronic structure calculations are carried out for MgC(Ni1-xCox)(3) alloys over the concentration range 0

High temperature flow behaviour and microstructural evolution were investigated in an annealed AA 8090 Al-Li alloy over the temperature range 623-803 K and strain rate range similar to6 x 10(6)-3x 10(2) s(-1). Stress-strain rate data, obtained using a differential strain rate test technique and plotted in log-log scale, exhibited three regions I, II, and M, with increasing strain rate. In these regions, the values of strain rate sensitivity index m and the activation energy for deformation were determined to be 0.17, 0.43, and 0.17; and 758.8, 93.3, and 184.3 kJ mol(-1), respectively. The stress-strain curves obtained from constant strain rate tests exhibited flow hardening at lower strain rates and higher temperatures whereas flow softening occurred at higher strain rates and lower temperatures. The microstructural evolution revealed the dominance of grain growth under the former conditions and dynamic recrystallisation under the latter conditions. Ductility and m were found to increase with temperature, with the maximum values of 402% and 0.55, respectively, at a temperature 803 K and strain rate 2 x 10(-4) s(1). (C) 2003 IoM Communications Ltd. Maney for the Institute of Materials, Minerals and Mining.

The technique of Self-propagating High-temperature Synthesis (SHS) was used to prepare NiAl from compacts using elemental powder mixtures in stoichiometric amounts under vacuum and argon atmosphere. Considerable changes in the oxygen contents of the specimen before and after the SH-synthesis were not observed. But, unusual occurrence of an impurity phase was noticed in the product as second phase precipitate. The sparsely distributed precipitates could be detected only in the Transmission Electron Microscope and was characterized to be an oxide of aluminium (alpha-Al2O3) containing nickel oxide (NiO), whose solubility in alpha-Al2O3 at room temperature has not been reported earlier. The occurrence of this phase could be traced to the oxygen on the surface of the reactant particles. (C) 2002 Kluwer Academic Publishers.

Electrochemical impedance spectroscopy, scanning electron microscopy, and energy dispersive X-ray analysis were employed to provide evidence of the dissolution and redeposition steps involved in the activation of aluminium by indium in aluminium alloy sacrificial anodes having indium as an activator. The experiments clearly showed that the alloyed indium dissolved and redeposited back on to the aluminium surface. This redeposition step was responsible for activating passive aluminium. (C) 1996 The Institute of Materials.

MnAPO and MnSAPO (APO = aluminum phosphate; SAPO = silicoaluminophosphate) with -34 and -44 framework structures have been synthesized. Rapid synthesis of MnAPO-34 could be achieved using morpholine as the template that subsequently changes to MnAPO-20 during synthesis. The presence of manganese in the framework has been established by a number of experimental techniques. ESR spectra of the low manganese containing samples were better resolved, and by comparison of these with the ESR of Mn2+-exchanged samples, it was possible to conclude that Mn2+ was present in the framework of the MnSAPOs. The nature of the silicon site depended on the manganese content of the sample as seen from Si-29 MASNMR. With higher manganese content, more silica-rich regions next to SAPO domains in the framework were formed. In MnAPO-44, a complete ordering of the T atoms appeared to have been achieved with every P atom being surrounded by three Al and one Mn. DTA-TG, infrared, and UV-visible spectra of the samples will be discussed.

Medium pore molecular sieves SAPO-11, SAPO-31 and SAPO-41 have been synthesized using di- n -propylamine as the organic template. They have been characterized by various methods such as X-ray powder diffraction, solid state MAS NMR spectroscopy, thermal analysis, chemical analysis and temperature programmed desorption (TPD) of ammonia. Catalytic activities of these materials in the alkylation of toluene with methanol have been studied. While SAPO-11 and SAPO-31 showed moderate activity, very high catalytic activity was shown by SAPO-41. All the catalysts showed varying degrees of shape selectivity towards p -xylene. SAPO-41 gave a large amount of 1,2,4-trimethylbenzene in addition to the xylenes.

Commercially pure titanium substrate was coated with aluminium by flame spraying or arc spraying techniques and was irradiated with a laser to form a laser-alloyed zone (LAZ). The microstructure of the LAZ was investigated. High-temperature oxidation tests were carried out in air at different high temperatures and the characteristics of the oxide layer were investigated using Auger electron spectroscopy. The aqueous corrosion tests were carried out in 3.5% NaCl solution at room temperature. The laser-processed material showed considerable improvement in the high-temperature oxidation-resistant property while the aqueous corrosion-resistant property of the LAZ was found to remain almost unaffected.

Silicon-substituted aluminophosphates with different framework structures SAPO-5, -11, -34 and -44 have been synthesized by the hydrothermal method using organic templates. The extent of silicon substitution in these materials has been investigated by chemical analysis, measurement of acidity through temperature-programmed desorption of ammonia and silicon MAS-NMR spectroscopy. It has been found that for SAPO-5, and SAPO-11 a small amount of silicon substitution takes place at the phosphorus sites and most of the silicon atoms are present either as silica-rich regions in the structure or as amorphous silica. The amount of silicon in them is quite low. For SAPO-34 and -44, on the other hand, the major part of the silicon randomly substitutes the phosphorus atoms and the rest of it forms small silica patches in the structure. The last two structures cannot be prepared in pure form unless the concentration of the silica source in the synthesis gel is quite high.

Report in details the preparation and procedure and some physical properties of a few Al-based metastable alloys in the amorphous or quasicrystalline phase by MA. Furthermore, their properties are compared with those of the similar composition prepared by some other conventional techniques. The following compositions were mechanically alloyed for several hours until metastable phases wre obtained, either in amorphous or in quasi-crystalline form: Al 50 Mn 20 Si 30 , Al 50 Mn 20 Ge 30 and Al 50 Mn 20 Si 20 Ge 10