Properties of YIG-based magnetic glass-ceramics with different nucleating agents

The effect of bismuth, silver oxide and palladium on the crystallization of yttrium iron garnet in Na₂O-SiO₂-Y₂O₃-Fe₂O₃ glass-ceramics has been investigated by X-ray diffraction thermal analysis, magnetic measurements and optical microscopy. It is found that the magnetic properties of these glass-ceramics can be altered significantly by a change in the nucleating agents and the heat treatment schedule. This behaviour is explained on the basis of the microstructure and the volume fraction of the different magnetic phases crystallized within the glasses.     

Phases and Microstructures in Zirconia-Calcia-Titania Multiphase Ceramics

Two cubic phases of differing compositions and lattice parameters and a monoclinic phase are found in samples of zirconia with 8 mol% calcia and 4 to 10 mol% titania. Increasing amounts of titania reduce the amounts of the cubic phases. The monoclinic phase dissolves small amounts (∼1 mol%) of calcia and up to 4.7 mol% titania; these amounts for the cubic phases are much larger. The cubic lattices contract linearly with increasing amounts of titaia and a contraction in the monoclinic lattice is also evident.     

Bending of Delaminated Composite Conoidal Shells under Uniformly Distributed Load

Conoidal shells are very popular roofing units owing to their aesthetic elegance and stiffness. Many parts of the globe, which were earlier assumed to be seismologically stable, are now being considered as earthquake prone. Hence the necessity to build light structures using composites has become very important. In this paper an eight-noded isoparametric shell element is applied for analyzing the bending behavior of delaminated composite conoidal shells under a uniformly distributed load with different practical boundary conditions. To ensure compatibility of deformation and equilibrium of forces and moments at the delamination crack front, a multipoint constraint algorithm is incorporated, which leads to an unsymmetrical stiffness matrix. This formulation is validated through the solution of benchmark problems. Lamination, curvature, and extent of delamination area are varied to compare the performances of delaminated conoidal shells against those with no damage. The results are carefully observed, and a set of conclusions is presented at the end of the paper.     

1‐Aza‐15‐Crown‐5 Functionalized Graphene Oxide for 2D Graphene‐Based Li+‐ion Conductor

Attachment of Li⁺ ion on graphene surface to realize Li⁺‐ion conductor is a real challenge because of the weak interaction between the ions and the functional groups of graphene oxide; although, a large number of theoretical results are already available in the literature. To overcome this problem, graphene oxide is functionalized by 1‐aza‐15‐crown‐5, the cage‐like structure containing four oxygens that can bind Li⁺ ion through electrostatic interaction. Li⁺ migration on graphene surface has been investigated using ac relaxation mechanism. Perfect Debye‐type relaxation behavior with β (relaxation exponent) value ≈1 resulting from single ion is observed. The activation energy of Li⁺ migration arising due to cation‐π interaction is found to be 0.37 eV, which agrees well with recently reported theoretical value. It is believed that this study will help to design isolated ion conductors for Li⁺‐ion battery.     

Nanocrystalline magnetic alloys and ceramics

Magnetic properties of materials in their nanocrystalline state have assumed significance in recent years because of their potential applications. A number of techniques have been used to prepare nanocrystalline magnetic phases. Melt spinning, high energy ball milling, sputtering, glassceramization and molecular beam epitaxy are some of the physical methods used so far. Among the chemical methods, sol-gel and co-precipitation routes have been found to be convenient. Ultrafine particles of both ferro- and ferrimagnetic systems show superparamagnetic behaviour at room temperature. Coercivity(H _c ) and maximum energy product(BH) _max of the magnetic particles can be changed by controlling their sizes. The present paper reviews all these aspects in the case of nanocrystalline magnetic systems — both metallic and ceramics.