Details of crystalline growth in co-deposited electroplated nickel films with hard (nano)particles

Electroplated nickel dispersion films with incorporated hard particles, primarily titanium oxide, were studied. A sufficient dispersion of nanometre-scaled particles in Watts solution was reached by application of ultrasonic energy to the galvanic bath. Crystal morphology, mean grain size and formation of textures were examined by electron backscattering diffraction (EBSD), X-ray diffraction (XRD) and transmission electron microscopy (TEM). The typical columnar structure of pure Ni films was refined by means of ultrasound. Incorporation of micron-sized TiO₂ particles generates additional nucleation surfaces in contrast to SiC particles. Textures of the subsequent columnar nickel crystals change from 〈2 1 1〉 (silent condition) or 〈1 1 0〉 (ultrasonic condition) fibre textures in growth direction to 〈1 0 0〉 and 〈1 1 1〉 textures under the influence of nanoparticle incorporation. Moreover, nanoparticles remarkably decrease the grain size and grain aspect ratio. Their incorporation takes place inside the crystals as well as between grains.     

Effect of hot deformation temperature on the magnetic and mechanical properties of Nd-Fe-B magnets prepared by spark plasma sintering

The magnetic and mechanical properties of Nd-Fe-B magnets at different hot deformation temperatures have been investigated. The results showed that the optimum magnetic and mechanical properties and the highest crystallographic alignment of Nd-Fe-B magnets were obtained at 700 °C, and the possible reasons were analyzed. The microstructures show that abnormal grain growth is not observed at 650 °C; there exist many small spherical grains, and these small grains do not align during die upsetting. The average size of the grains and the volume fraction of coarse grains increase with increase in deformation temperature. The coarse grains do not align during die upsetting, and the non-alignment regions enlarge with increase in deformation temperature.     

Novel mesoscale defect structure on NiO(1 0 0) surfaces by atomic force microscopy

Cleaved NiO(1 0 0) surfaces were imaged with atomic force microscopy (AFM) to determine defect concentrations and morphology. Random 〈0 1 0〉 and 〈0 0 1〉 oriented steps, which have been previously characterized, were the most common defect observed on the cleaved surface and formed with step heights in multiples of 2.1 Å, the Ni-O nearest-neighbor distance, and terrace widths in the range of 25-100 nm. In addition, the surface showed novel mesoscale (∼0.5-2 μm) square pyramidal defects with the pyramid base oriented along 〈1 0 0〉 symmetry related directions. Upon etching, the pyramidal defects converted to more stable cubic pits, consistent with (1 0 0) symmetry related walls. The square pyramidal pits tended to cluster or to form along step edges, where the weakened structure is more susceptible to surface deformations. Also, a small concentration of square pyramidal pits, oriented with the base of the pyramid along 〈0 1 1〉, was observed on the cleaved NiO surfaces. For comparison purposes, chemical mechanical polished (CMP) NiO(1 0 0) substrates were imaged with AFM. Defect concentrations were of comparable levels to the cleaved surface, but showed a different distribution of defect types. Long-ranged stepped defects were much less common on CMP substrates, and the predominant defects observed were cubic pits with sidewalls steeper than could be accurately measured by the AFM tip. These defects were similar in size and structure to those observed on cleaved NiO(1 0 0) surfaces that had been acid etched, although pit clustering was more pronounced for the CMP surfaces.     

Effect of deformation and annealing on the microstructure and magnetic properties of grain-oriented electrical steels

The effect of plastic deformation and subsequent annealing on the magnetic properties and microstructure of a grain-oriented (GO) electrical steel has been studied. True strain (ε) from 0.002 to 0.23 was applied by rolling in two directions, rolling (RD) and transverse (TD). The deterioration of power losses varies according to the direction of deformation. Annealing the strained material—at 800 °C/2 h—leads to a recrystallization and restored magnetic properties. The main components of annealed-textures are around 15–35° from those of deformed-textures for both RD and TD. Rolling along {1 1 0} 〈0 0 1〉 direction leads to the development of deformation twins.     

MeV-ion axial surface-channeling from an electron irradiated KCl(0 0 1) surface

Surface-channeling of protons incident with 5 mrad on an electron-irradiated surface is investigated using a 0.55 MeV beam of protons. The target surface is KCl(0 0 1), which is damaged by electron-stimulated desorption with 5 keV electron irradiation. The direction of the incident beam is adjusted along the 〈1 0 0〉 and 〈1 1 0〉 channeling conditions and the channeling-dips of the scattering yields are observed. The irradiation dose-dependence of the minimum yields and widths of the dips is measured. Two dips are compared, i.e., for the 〈1 0 0〉 and 〈1 1 0〉 channelings. By increasing the irradiation dose up to 2 × 10¹⁶ cm⁻², the dip around the 〈1 0 0〉 axis becomes opened, but that of the 〈1 1 0〉 axis becomes shallow. The irradiated surfaces are observed to have many overlapped terraces of sub-micron with monolayer steps. The surface morphology deformed by the irradiation effects to truncate trajectories of the 〈1 0 0〉 channeling protons. This roughness of the surface is more effective for the trajectories of the 〈1 1 0〉 channeling protons. The protons incident on the rough surface along the 〈1 1 0〉 axis are not reflected from the atomic row but reflected by a potential of the surface with steps. Results by a simple computer simulation of the trajectories of protons at stepped surfaces also indicate the scattering processes.     

Nanoridge domains in α-phase W films

Two types of nanoridge domains oriented with each other with an angle ranging between 109° and 124° were measured by scanning tunneling microscopy on the α-W film sputter deposited on an oxidized Si surface. Each domain contains nanoridges with a period of 7.5 ± 1.0 nm. No such domains were observed on the β-W film surface. We argued that due to the anisotropy of the W(1 1 0) surface, the impinging W atoms diffuse faster along the 〈111〉 directions on the surface to form the nanoridge structure. There are two equivalent 〈111〉 directions, which give rise to two orientational domains with an angle of ∼110°. An isotropic β-W(1 0 0) phase has no preferred diffusion direction for the impinging W atoms and therefore, no nanoridge domain structure was observed.     

STM observation of initial growth of Sn atoms on Ge(0 0 1) surface

We have studied initial growth of Sn atoms on Ge(0 0 1) surfaces at room temperature and 80 K by scanning tunneling microscopy. For Sn deposition onto the Ge(0 0 1) substrate at room temperature, the Sn atoms form two kinds of one-dimensional structures composed of ad-dimers with different alignment, in the 〈3 1 0〉 and the 〈1 1 0〉 directions, and epitaxial structures. For Sn deposition onto the substrate at 80 K, the population of the dimer chains aligning in the 〈3 1 0〉 direction increases. The diffusion barrier of the Sn adatom on the substrate kinetically determines the population of the dimer chain. We propose that the diffusion barrier height depends on surface strain induced by the adatom. The two kinds of dimer chains appearing on the Ge(0 0 1) and Si(0 0 1) surfaces with adatoms of the group-IV elements are systematically interpreted in terms of the surface strain.     

Angular distributions of atoms sputtered from NiAl{1 1 0} and Ni{1 0 0}

Using the laser post-ionization surface analysis technique, I have for the first time studied angular distributions of Ni and Al atoms sputtered from NiAl{1 1 0}. Emission angular distributions from Ni{1 0 0} have also been measured. I have observed preferential emissions of Ni and Al atoms along 〈1 1 1〉 and 〈1 0 0〉crystallographic directions for NiAl{1 1 0} and of Ni atoms along 〈1 1 0〉 and 〈1 0 0〉 directions for Ni{1 0 0}. The observed preferential ejections can be explained in terms of the theory of focusing-collision sequences. Because of the difference in surface binding energy between Al and Ni atoms, preferential ejection angles of Ni atoms are slightly different from those of Al atoms along the 〈1 1 1〉 ejections. For NiAl, the 〈1 1 1〉 preferential ejections were less prominent than the 〈1 0 0〉 preferential ejections and this can be related to the low efficiency of momentum transfer in Ni-Al collision sequences along 〈1 1 1〉 lattice directions. The low efficiency of momentum transfer due to the mass mismatch can also be responsible for the experimental observation that the preferential ejections in the alloy were less prominent than those in the Ni metal.     

Interactive contribution of grain size and grain orientation to coercivity of melt spun ribbons

During melt spinning process, the improvement of certain grain orientation and the refinement of grain size with surface velocity have interactive and contradictory effects on the magnetic properties. The contributions of these effects have seldom been taken into account and they were discussed in this paper via Fe-2, 4, 6.5 wt% Si alloys. Heat treatment at 1173 K for 1 h was performed to show the annealing impact. The X-ray diffraction patterns show that the high surface velocity and heat treatment increase the intensity ratio of line (2 0 0) to (1 1 0) of A2 phase. The (2 0 0) line corresponds to (2 0 0) plane in 〈0 0 1〉 direction, easy magnetization direction of α-Fe phase in Fe-Si alloy. The improvement of this grain orientation with the surface velocity decreases the coercivity, which should increase due to the grain refinement. It is revealed that the 〈0 0 1〉 texture promoted by the anisotropic heat release during melt spinning process is one factor to improve the magnetic properties and should be considered when preparing soft magnetic materials.     

The formation model of Ni-Cr oxides on NiCoCrAlY-sprayed coating

The atomic arrangement and distribution of oxides (Cr₂O₃, NiCr₂O₄ and NiO) on the sprayed-NiCoCrAlY coating after oxidation are analyzed. The formation and the growth model of Ni-Cr oxide phases are discussed according to the matching relationship between atoms. The outline character and a scale of spinel NiCr₂O₄ are discussed. The results show that Cr atoms can form two close-packed arrangements in the crystal plane of Cr₂O₃ perpendicular to 〈0 0 1〉 orientation. The atomic spacing in the first arrangement corresponds to double that of Ni/Ni₃Al in {1 1 1} crystal face. This suggests that Ni/Ni₃Al is the substrate for Cr₂O₃ to grow along 〈0 0 1〉 direction. The lattice mismatch between Cr₂O₃ and Ni/Ni₃Al is less than that of Al₂O₃, which indicates that Cr₂O₃ is easier to form than Al₂O₃ during the oxidation process. The atomic spacing in another close-packed arrangement of Cr₂O₃ perpendicular to 〈0 0 1〉 orientation is approximately equal to that of Ni or Cr in the plane of NiCr₂O₄ and NiO perpendicular to 〈1 1 1〉 orientation. So Cr₂O₃ can be the substrate for NiCr₂O₄ and NiO to grow in the 〈0 0 1〉 direction. NiCr₂O₄ and NiO can grow directly along the 〈1 1 1〉 orientation on each other. NiCr₂O₄ can grow outward in the planes of Cr₂O₃ perpendicular to 〈0 0 1〉 and grow inward along 〈1 1 1〉 orientation of NiO.     

Investigation on the magnetocaloric effect in DyNi2, DyAl2 and Tb1−nGdnAl2 (n=0, 0.4, 0.6) compounds

The magnetocaloric effect (MCE) in the DyNi₂, DyAl₂ and Tb_1−nGd_nAl₂ (n=0, 0.4, 0.6) was theoretically investigated in this work. The DyNi₂ and DyAl₂ compounds are described considering a model Hamiltonian which includes the crystalline electrical field anisotropy. The anisotropic MCE was calculated changing the magnetic field direction from 〈1 1 1〉 to 〈0 0 1〉 in DyNi₂ and from 〈1 0 0〉 to 〈0 1 1〉 in DyAl₂. The influence of the second- and first-order spin-reorientation phase transitions on the MCE that occurs in these systems is discussed. For the calculations of the MCE thermodynamic quantities in the Tb_1−nGd_nAl₂ systems we take into account a two sites magnetic model, and good agreement with the available experimental data was obtained.     

Competition between surface energy and interphase energy in transition region and diameter-dependent orientation of silicon nanowires

A small sandwiched transition region between the Au catalysis droplet and silicon nanowires (SiNWs) is proposed to investigate the diameter-dependent orientation of SiNWs grown by the vapor-liquid-solid (VLS) mechanism. Atomic-scale calculation shows that for a given transition region width, there is always a critical diameter. Below the critical value, surface energy dominates and the 〈1 1 0〉 orientation is preferred, whereas at larger diameters, the interphase energy dominates and SiNWs grow along the 〈1 1 1〉 direction. The variability of the critical diameter is also included in our model by adjusting the transition region width. The theoretical results are in agreement with those from experiments.     

Influence of the substrate on ferroelectric properties of 〈1 1 1〉 oriented rhombohedral Pb(Zr0.6Ti0.4)O3 thin films

〈1 1 1〉-oriented Pb(Zr_0.6Ti_0.4)O₃ thin films were elaborated in the same run by RF multitarget sputtering on Si/SiO₂/TiO₂/Pt(1 1 1) and LaAlO₃/Pt(1 1 1) substrates. PZT thin films were textured, exhibiting 〈1 1 1〉 fibre texture on silicon substrates whereas epitaxial relationships were found when grown on LaAlO₃/Pt(1 1 1). On the latter substrate, values of spontaneous polarization and of dielectric permittivity were measured close to that calculated previously along the 〈1 1 1〉 direction of PZT rhombohedral single crystal. On the contrary, spontaneous polarization and dielectric permittivity measured on PZT thin films deposited on platinized silicon were found deviating from calculated values. These different electrical results are attributed to different ferroelectric domain configurations.     

Developments in the production of grain-oriented electrical steel

The quality and production technology of grain-oriented electrical steel have been improved over the past 70 years. Firstly, through the improvement of {1 1 0} 〈0 0 1〉 alignment, development of thinner-gauge material, and establishment of magnetic domain refining techniques, magnetic properties of the material have been improved dramatically. Secondly, many mechanisms have been proposed for the reason why Goss texture develops selectively during the final annealing stage. Thirdly, to reduce manufacturing costs, many new techniques have been developed. The most advanced in commercial realization is the application of low-temperature slab-reheating techniques. Despite these achievements, the mechanisms of texture selection are not yet clear in all their details. Further improvement of magnetic properties and the application of compact production process for grain-oriented electrical steels in commercial production are needed to be realized.     

Texture, microstructure and magnetic properties of Fe-28Cr-15Co-3.5Mo permanent magnet

Crystallographic texture, microstructure and magnetic properties of Fe-28Cr-15Co-3.5Mo alloy were studied as a function of processing parameters. Texture studies revealed that thermo-magnetic aging leads to the development of ideal Goss type, {1 1 0} 〈0 0 1〉 and cube type {0 0 1} 〈0 1 0〉 textures. The orientation densities of these texture components become stronger after the step-aging treatments. Microstructural features show that improvement in magnetic properties were due to aligning and elongation of ferromagnetic Fe, Co-rich (α₁) particles in the preferred 〈1 0 0〉 directions. Magnetic analysis reveals that magnetic properties of the alloys are directionally dependent and influenced by the choice of thermo-magnetic treatment temperature or time. The maximum values of intrinsic coercive force, remanence and energy product, obtained in the textured magnetic alloy were 68.99 kA/m (867 Oe), 1.12 T (11.2 kG) and 43.2 kJ m³ (5.4 MG Oe), respectively.     

In-situ synchrotron X-ray diffraction study of stress-induced phase transformation in Ti50.1Ni40.8Cu9.1 thin films

Stress-induced martensitic transformation of as-sputtered and post-annealed Ti_50.1Ni_40.8Cu_9.1 thin films was investigated using in-situ synchrotron X-ray diffraction (S-XRD) technique. For the as-deposited film, in-situ S-XRD analysis showed a martensitic transformation from parent phase to martensite during initial loading, followed by reorientation of martensite variants via detwinning. This detwinning process induced a strong 〈0 2 0〉 fiber texture along the loading direction and a strong 〈0 0 2〉 fiber texture perpendicular to the loading direction. For the 650 °C annealed film, there is only elastic deformation, followed by a martensitic transformation during deformation.     

Microstructure and texture evolution of strip casting 3 wt% Si non-oriented silicon steel with columnar structure

An Fe-3 wt%Si strip with columnar structure and pronounced {0 0 1}〈0 v w〉 texture was produced using a twin-roll strip caster. Then the as-cast strip was cold-rolled and annealed. The microstructure and texture evolution along the processing steps was investigated. It is found that inhomogeneous microstructure is produced in both cold-rolled and final annealed samples due to the large initial grains. The cold rolling texture is dominated by pronounced a-fiber texture and relatively strong γ-fiber texture. The final recrystallization texture is characterized by {0 0 1}〈0 1 0〉, {0 0 1}〈2 1 0〉, {1 1 0}〈0 0 1〉 texture and a slightly shifted {1 1 1}〈1 1 2〉 component. The microstructural inhomogeneity plays an important role in the texture evolution.     

Structure, magnetic and magnetostrictive properties of as-deposited Fe-Ga thin films

Polycrystalline Fe_100−xGa_x (19?x?23) films were grown on Si(1 0 0) substrates at different partial pressures of sputtering gas ranging from 3 to 7 μbar. Microstructural, magnetic and magnetostrictive properties were studied using X-ray diffraction (XRD), atomic force microscopy (AFM), energy dispersive spectroscopy (EDS) and magneto-optic Kerr effect (MOKE) magnetometry respectively. X-ray diffraction showed that all films have the body-centered cubic (bcc) Fe-Ga phase with the 〈1 1 0〉 direction out of the film plane. Magnetic characterization of the films showed that the films prepared at 3 μbar had weak uniaxial anisotropy whereas films grown at Ar pressures in the range 4-7 μbar were magnetically isotropic. The effective saturation magnetostriction constants (λ_eff) of the films were measured using the Villari effect. It was found that effective saturation magnetostriction constants were almost constant over the Ga composition range achieved by varying the sputtering pressure. The measured effective magnetostriction constants fit closely to the calculated saturation magnetostriction constants of 〈1 1 0〉 textured polycrystalline films with the 〈1 1 0〉 directions slightly canted with respect to the normal to the sample surface. It was found that a high pressure of the sputtering gas effected the magnetic softness of the films. The saturation field increased and remanence ratio decreased with increase in pressure.     

Effect of temperature on non-destructive wave propagation in potassium halides

Temperature dependence of ultrasonic attenuation is investigated for potassium halides in the temperature range 100–400 K. These calculations are done for KCl, KBr and KI for longitudinal and shear waves along the 〈1 1 1〉 direction. The non-linearity coupling parameters and thermal relaxation time have also been obtained for these crystals. In the present investigation, it has been found that phonon–phonon interaction is the dominant cause for ultrasonic attenuation.     

Nucleation and orientation of graphite{0001} layers on Pt{110}

Investigations by field electron microscopy revealed that graphite{0;0001} layers grow preferentially on Pt{110}. Layer nucleation and initial growth occurs in the vicinal area of {110} along the 〈112〉 and the 〈100〉 zones and not on the unstepped {110} plane itself. The growth rate in the vicinal area is determined by the epitaxial misfit parallel to the step edges. An alignment of the graphite layer with the underlying {110} is observed. It corresponds to graphite〈101̄0〉 ∥ Pt〈100〉, which coincides with the calculated orientation of smallest epitaxial misfit. The change of relative emission from {110} upon adsorption of graphite is discussed.