Texture and Anisotropy of Hot-Pressed h-BN Matrix Composite Ceramics With in Situ Formed YAG

Textured h-BN matrix composite ceramics were prepared by hot-pressing using different contents of 3Y2O3-5Al2O3 (mole ratio of 3:5) as the liquid phase sintering additive. During the hot-pressing process, the liquid Y3Al5O12 (YAG) phase with good wettability to h-BN grains was in situ formed through the reaction between Y2O3 and Al2O3, and a coherent relationship between h-BN and YAG was observed with [010]h-BN // [1̅11]YAG and (002)h-BN // (321)YAG. Plate-like h-BN grains in the YAG liquid phase environment were rotated under the action of the uniaxial sintering pressure, making their basal surfaces preferentially arranged perpendicular to the sintering pressure, forming textured microstructures with the c-axis of h-BN grains oriented parallel to the sintering pressure, which give these composite ceramics anisotropy in their mechanical and thermal properties. The highest texture degree was found in the specimen with 30 wt.% YAG content, which also possesses the most anisotropic thermal conductivity. The aggregation of YAG phase resulting in the buckling of h-BN plates was observed in the specimen with 40 wt.% YAG content, which significantly reduced its texture degree.

Effects of a magnetic field applied during electroplating on the texture and magnetic properties of Ni nanowire arrays

Ni nanowire arrays were prepared by electroplating using anodic aluminum oxide templates, and a magnetic field was applied during the electroplating process. The effects of an applied magnetic field on the texture and magnetic properties of the Ni nanowire arrays were studied. The results show that the (110) texture is formed in the nanowires prepared in different magnetic fields. However, the applied magnetic field during electroplating can affect the texture degree, and there exists a suitable magnetic field for small diffusion degree of the (110) texture. On the basis of texture characterization, the effects of applied magnetic field on the magnetic properties of Ni nanowire arrays are discussed.

Determination of Texture Degree of NdFeB-Magnets by Means of Neutron Diffraction

Six samples of Nd-Fe-B-permanent magnets, distinguished in the texture degree, have been measured by neutron diffraction in the reflection and transmission regimes. The texture in the samples was formed by application of impulses of external magnetic field 0H = 4 T. Analysis of the obtained neutron diagrams by means of the Fullprof program allowed quantitative determination of the texture degree and conclusion to be made that the texture degree grows with an increase in numbers of magnetic field impulses.

Growth and Characterisation of Electrodeposited Co/Cu Superlattices

Ferromagnetic/non-ferromagnetic Co/Cu superlattices were grown on polycrystalline Titanium (Ti) from a single electrolyte by electrodeposition. Microstructure and magnetoresistance (MR) of the superlattices were investigated as a function of the electrolyte pH as well as the layer thicknesses. Structural characterisation by X-ray diffraction (XRD) showed that the superlattices have face-centred cubic (fcc) structure with a strong (111) texture at the studied pH levels, but the texture degree is affected by the electrolyte pH. The scanning electron microscope (SEM) studies revealed that the superlattices grown at low pH (2.0) have smoother surfaces compared to those grown at high pH (3.0). The superlattices exhibited either anisotropic magnetoresistance (AMR) or giant magnetoresistance (GMR) depending on the Cu layer thickness. The shape of MR curves changes depending on the combination of Co and Cu layer thicknesses. The superlattices with Co layers less than 3 nm and Cu layers less than 2 nm have broad and non-saturating curves, indicating the predominance of a superparamagnetic contribution, possibly due to the discontinuous nature of the ferromagnetic (Co) layer. For superlattices with the same bilayer and total thicknesses, the GMR magnitude decreased as the electrolyte pHincreased. Besides possible structural differences such as the texture degree and the surface roughness, this may arises from the variation in the Cu content of the ferromagnetic layers caused by the electrolyte pH.

Textured Pb(Mg1/3Nb2/3)O3–PbTiO3 Ceramics Prepared by Reactive Templated Grain Growth

<001> textured Pb(Mg1/3Nb2/3)O3-0.325PbTiO3 (PMN-32.5PT) ceramics were prepared by reactive templated grain growth (RTGG). Plate-liked {001}-SrTiO3 single crystal particles were used as template seeds. MgNb2O6, TiO2, PbO were mixed with SrTiO3 templates as a reactive matrix. SrTiO3 templates were oriented after tape-casting. The textured PMN–32.5PT ceramics were produced after heat treatment. In preparing textured PMN-32.5PT, RTGG was more efficient than TGG because of the chemical energy released in reaction. The final texture degree was very sensitive to the sintering history. An initial anneal step below the melting point of PbO resulted in better development of texture.

Proton Beam Texturing of Superconducting YBaCuO Ceramics

ABSTRACTResistive superconducting (SC) transition, current-voltage characteristics, and X-ray diffraction (XRD) of YBaCuO ceramics have been studied after exposure to 18 MeV proton beam at 300 K. In the interval of 1013 −5×1014 cm−2 the irradiation induced oxygenation of weak intergrain contacts and grain alignment, anisotropy and broadening of SC-transition measured along and across the proton beam, and residual magnetization were found. The proton induced anisotropic texture is responsible for the critical current increase at 77 K and the resistivity decrease at 90–200 K. In a higher dose interval of 1013 −1015 cm−2 the SC-transition parameters degrade and the resistivity increases, depending on a texture degree, weak intergrain links become deoxygenated and no texture occurs. The magnetization (pinning) and the anisotropy of SC-transition can be due to localization of charges at the proton induced defects (mostly in oxygen sublattices).

On The Harris Texture Index

The texture index introduced by Harris (1952) is reconsidered from the point of view of the orientation distribution of crystallites in a flat powder specimen. It is shown that the texture index can be used as an approximate measure of texture degree or as a texture correction factor in cases of a weak texture. Its failure in both these aspects for the strong textures is caused by an incorrect averaging of pole densities contained in the original definition of this quantity.