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A systematic investigation has been performed to study the oxidation response of Mo 76 Si 14 B 10 alloy doped with traceable amount of Ce and Al at temperature in the range of 900–1300 °C. The resistance to degradation of Mo 76 Si 14 B 10 ≥ 900 °C has increased due to the dissociation of Mo-oxides into Mo in protective glassy borosilicate layer. Addition of Ce aggrieves oxidation initially, but protection is achieved upon exposure within 3 h at all the different temperatures. No passivation has occurred in Al containing alloy due to the dissolution of Al 2 O 3 in the borosilicate scale leading to the precipitation of aluminum-borate and mullite along with unreacted cristoballite. [ABSTRACT FROM AUTHOR]

• (Ni x Fe 1- x) 70.5 B 17.7 Si 7.8 Ti 4 (at.%) have been prepared by ball milling. • Milled powders consist of α and γ phase in x = 0.3 and 0.4, respectively. • The onset temperature of crystallization increases as Fe content decreases. • The heat-treated x = 0.4 powder shows a |−Δ S M | of 0.695 J/kgK at 19.9 kOe. We report the evolution of nanocrystalline α -Fe and γ-Ni phases in (Ni x Fe 1- x) 70.5 B 17.7 Si 7.8 Ti 4 (at.%) where, x = 0.3 and 0.4, upon mechanical alloying of elemental powder mixtures up to 36 h. The effect of milling time on the nanostructure evolution, thermal stability, and magnetic properties have been investigated throughly using x-ray diffraction (XRD), differential scanning calorimetry (DSC), and vibrating sample magnetometry (VSM). XRD analysis of the as-milled powders revealed that the lattice parameter and the crystallite size of α -Fe phase lies in between 0.2850-0.2972 nm and 3–14 nm; whereas the same for γ-Ni lies in between 0.3550-0.3608 nm and 8–41 nm, respectively, during milling. The thermal analysis of the as-milled powders suggests that the onset temperature of crystallization increases as Fe content decreases. The thermomagnetic measurement of the heat treated powders has revealed the T C of α -Fe phase in x = 0.3 to be 590 K and that of γ-Ni phase in x = 0.4 to be 375 K. The maximum magnetic entropy change has been estimated to be 0.159 Jkg-1K−1 in x = 0.3, while that of x = 0.4 has been found to be 0.695 Jkg-1K−1 at an applied magnetic field of 19.9 kOe. [ABSTRACT FROM AUTHOR]

Abstract: This paper reports the paramagnetic behavior of Mn doped ZnO co-doped with rare earth (Gd and Sm) atoms. The formation of secondary rare earth oxides (Gd2O3 and Sm2O3) is confirmed from the X-ray diffraction patterns. The rare earth oxides in the system forbids the grain growth and interconnection between the grains. The weak link between the grains suppresses the long range exchange interaction between the Mn ions and hence, reduces the ferromagnetic ordering. Owing to the large mismatch between ionic radii of rare earth and transition metal atoms inside the matrix, the rare earth element cannot contribute to promote ferromagnetic behavior in Mn doped ZnO, irrespective of their high individual magnetic moments. [Copyright &y& Elsevier]

Abstract: Mn-doped ZnO samples having composition Zn1−x Mn x O (x=0.02, 0.04 and 0.05) were synthesized by solid state reaction technique with varying concentration of Mn from 0.02 to 0.05. Evidence of room temperature ferromagnetism was observed only in the composition Zn0.98Mn0.02O sintered at 500°C. Our XRD pattern confirms the presence of Mn3O4 impurity phase in all the Zn1−x Mn x O samples with the exception of Zn0.98Mn0.02O. We emphasize that the appearance of Mn3O4 phase in the system forbids the exchange type of interaction between the Mn ions and suppresses the ferromagnetism in all the Mn over-doped Zn1−x Mn x O (x>0.02) system. SEM microstructure study also supports the interruption of exchange type of interaction inside the system with the increase in Mn concentration in the sample. Interestingly, for this particular composition, Zn0.98Mn0.02O sintered at 500°C, glassy ferromagnetism type of transition is observed at low temperature. This type of transition is attributed to the formation of the oxides of Mn clusters at low temperature. [ABSTRACT FROM AUTHOR]

Abstract: A clean signature of room temperature multiferroicity in Bi1.2Gd0.1Fe0.8O3 ceramics is observed. Samples were prepared by slow step sintering technique at 850°C. Impurity peaks normally present in original BiFeO3 are completely suppressed with the increase of Bi concentration. Apart from this, structural transformation took place from R3 C to Pn21 a space group and a clear orthorhombic grain growth habit is seen by SEM microstructure. Suppression of impurity phases favors the reduction of mobile oxygen vacancies and hence reduces leakage current for which ferroelectric properties of Bi1.2Gd0.1Fe0.8O3 are enhanced. We argue that the addition of Gd is likely to suppress the spiral spin modulation and at the same time increase the canting angle which favors the enhanced ferromagnetism. Excess Bi is expected to act as point defects and occupy interstitial positions which in turn surrounded by oxygen vacancies and is likely to promote defect driven ferromagnetism with enhanced spin and electric polarization. This finding encourages further revaluation of long-discounted BiFeO3 for multiferroics research. [ABSTRACT FROM AUTHOR]

Abstract: This paper reports on multiferroic properties of Ho substituted BiFeO3 (Bi1−x Ho x FeO3) ceramics. It is observed that for x=0.15, a prominent ferroelectric loop is seen at 300K even if the system remains in rhombohedral (R3c) phase without appearance of any observable impurity phases. A well shaped M–H loop is observed at 10K for x=0.15. However it showed ferromagnetism, confirming the contribution of Ho3+ towards enhancement of ferromagnetic properties of BiFeO3 at 300K. Suppression of impurity phases of pure BiFeO3 bulk ceramic favors the reduction of mobile oxygen vacancies and reduces leakage current, due to which ferroelectric properties of BiFeO3 is enhanced. We argue that Ho substitution at Bi site is likely to suppress the spiral spin modulation and at the same time increase the canting angle, which favors enhanced multiferroic properties. XRD, SEM, magnetization, polarization and chemical bonding analysis measurements were carried out to explain the multiferroic behavior. [ABSTRACT FROM AUTHOR]

Abstract: Nanocrystalline Mn1− x Zn x Fe2O4 (0.2⩽x⩽0.9) was prepared by mechanical alloying of the concerned oxide precursors and subsequent annealing in air and Ar atmosphere, respectively. Milling and annealing in air produces Zn-ferrites (ZnFe2O4) instead of Mn–Zn ferrites as MnO converts to higher oxides at higher oxygen partial pressure and fails to dissolve in the spinel phase. This is confirmed by careful quantitative X-ray diffraction analysis using Rietvelt profile matching and also by the non-saturating paramagnetic nature of the magnetization response with very low saturation level of these spinels milled and annealed in air. On the other hand, single-phase Mn–Zn ferrite results from the identical precursor oxide blend when milling and annealing are carried out under controlled (Ar) atmosphere. The average grain size of the as-milled and annealed powders, measured by Rietvelt refinement, varies between 6–8 and 14–18nm, respectively. Further investigations performed with Mn0.6Zn0.4Fe2O4 reveal that a careful selection of annealing parameters may lead to an early superparamagnetic relaxation. Therefore, the blocking temperature can be significantly reduced through proper heat treatment schedule to ensure superparamagnetism and negligible hysteresis at low temperature. [Copyright &y& Elsevier]

Abstract: Nano-sized crystals of zeolite ZSM-5 were hydrothermally synthesized using a mixture of two templating agents, tri-ethyl butyl ammonium bromide (TEBA) and ethylene diamine (EDA). Synthesized samples were characterized by XRD, SEM and ammonia TPD. Influences of proportions of the templating agents, silica to alumina ratio (SAR) and crystallization period were have been studied. Crystal morphology and size of the synthesized samples varied with proportions templating agents and SAR. Crystal size in the range of 100–400nm was observed with equimolar templates for an SAR of 200. Crystal size increased to 1 to~3μm with SAR in the range of 400–1200. Crystallization of MFI zeolite in presence of mixed templates was found to pass through an unknown meta-stable intermediate. [Copyright &y& Elsevier]

• Oxidation behaviour of Mo 76- x Si 14 B 10 Fe x at 700–800 °C has been studied. • Moist air improves the mass loss by 99% during isothermal oxidation. • Fe addition improves the oxidation resistance in both dry and moist air. The effect of moist environment on the isothermal oxidation behavior of Mo 76- x Si 14 B 10 Fe x (x = 0, 0.5, 1 at.%) ultrafine composites containing proeutectic α–Mo solid solution phase and eutectic mixture of Mo 3 Si (A15) and Mo 5 SiB 2 (T2) phases, have been investigated at temperatures in the range of 700–800 °C. The mass loss has been greatly improved by 99% in moist environment than that of dry air both at 700 °C and 800 °C. The addition of Fe further improves the oxidation resistance in both dry and moist air up to 24 h exposure. The x–ray diffraction and the scanning electron microscopic studies have been performed to reveal the evolution of different phases in the oxide scale and to explore the mechanism of oxidation. The cross-sectional area of the residue alloy in the oxidized coupons has been measured to be 98% in moist air for x = 1 and 50% in dry air for x = 0 than that of the initial alloy coupon pointing that the oxidation resistance of Mo Si B can be greatly improved in presence of moist air as well as upon Fe addition. [ABSTRACT FROM AUTHOR]

The present study demonstrate the effect of stacking fault energy (SFE) on the evolution of crystallite size, dislocation density, twin density, stacking faults, and their mutual interactions during cryorolling in pure copper (SFE 78 mJ/m 2 ) and copper–zinc alloys with varying Zn content of 10 wt% (SFE 35 mJ/m 2 ), 20 wt% (SFE 19 mJ/m 2 ), and 30 wt% (SFE 14 mJ/m 2 ). The dislocation density, twin density and extrinsic fault probability increase whereas crystallite size decreases upon cryorolling and with the decrease of SFE. Accumulation of dislocations at the twin boundaries causes dynamic recrystallization, promotes grain refinement by forming subgrains inside the twin lamellae. Detail investigation on the activity of structural defects during cryorolling of Cu/Cu-Zn alloys has been done through resistivity measurements. Nanoindentation studies have performed to understand the deformation kinetics of the cryorolled Cu/Cu-Zn alloys with high concentration of structural defects in term of strain rate sensitivity and activation volume. A micromechanical model has been used to demonstrate the effect of SFE and the role of structural defects during nanostructuring at cryogenic temperature. [ABSTRACT FROM AUTHOR]

Nanotwinned α-brass (Cu–30 wt.% Zn) with varying lamellae thickness in the range of 28–170 nm, has been produced by cryorolling (CR). The effect of CR strain ( ɛ CR = 0.2–0.95) on the evolution of homogeneity and refinement in terms of twin lamellae thickness, twin spacing, and their distribution, have been studied using high-resolution transmission electron microscopy (HRTEM) and microhardness measurements. Analysis of X-ray peak broadening has shown that the crystallite size reduces down to 20 nm at ɛ CR = 0.95, which scales with the subgrain size in preexisting twin lamellae, as revealed under HRTEM. The effect of dislocation density and crystallite size on the strength of nanotwinned brass has been correlated using an analytical model. [ABSTRACT FROM AUTHOR]

Abstract: Nano-sized porous γ-aluminas have been successfully synthesized by control precipitation method using aluminium nitrate as precursor and different precipitating agents. The synthesized materials have been characterized by SEM, FTIR, XRD and N2 adsorption–desorption. Sample prepared by ammonium bicarbonate route possess spherical nano-sized particle with crystallite size in the range 4.7–5.7nm, surface area 190m2/g and pore volume ∼0.467cm3/g. It also exhibits excellent fluoride adsorption capacity. [Copyright &y& Elsevier]

Abstract We report the evolution of nanocrystalline γ-Ni of 3–7 nm size along with amorphous phase in (Ni 0.50 Fe 0.50) 70.5 B 17.7 Si 7.8 Ti 4 (at.%) upon mechanical alloying of the elemental powder mixture up to 36 h. The effect of milling time on the nanostructure, thermal stability and magnetic properties, have been investigated using x-ray diffraction, differential scanning calorimeter, transmission electron microscope, and vibrating sample magnetometer. The lattice parameter of the γ-Ni phase gradually decreases from 0.3607 nm for 9 h milling down to 0.3554 nm upon 36 h of milling. A first-order magnetic transition has been identified using Arrott plot analysis at Curie temperature (T C) of 608 K along with a large magnetic entropy change (Δ S M) of 0.45 J/kg.K at an applied field of 13800 Oe, and relative cooling power (RCP) of 10.15 J/kg. The effects of nanostructure and phase constituents on the thermal stability, T C , magnetization and coercivity, have been correlated. Highlights • (Ni 0.50 Fe 0.50) 70.5 B 17.7 Si 7.8 Ti 4 (at.%) has been prepared by mechanical alloying. • Heat-treated powder contain nanocrystalline γ -Ni phase with 13–22 nm size. • A first order transition has been identified. • The transition involves a large entropy change of |- ΔS M | = 0.45 J/kg.K at 13800 Oe. [ABSTRACT FROM AUTHOR]

Abstract: The mechanical behaviour upon compression of (Cu0.50Zr0.50)100−x Al x (x =4, 5, 7) rods with 2 and 3mm diameter was systematically studied and compared with the literature data. Fully amorphous bulk metallic glasses (x =5, 7) show little permanent deformation and reproducible yield stress values. The remarkable fracture strain, observed for some apparently X-ray diffraction amorphous samples (x =4), was found to be due to significant amounts (at least 20%) of the B2-CuZr crystalline phase. The effect of possible flaws on the external surface of the rods was evaluated by mechanical testing of either as cast and machined samples. [Copyright &y& Elsevier]