Papers by Keyword: Crystal Orientation

Abstract: The wetting angle (Θ) of molten Ag (Zn, Cu, Ga) drops on graphite substrate is investigated. A texture formation was found in the substrate/drop interphase region after solidification. The enrichment (segregation) of Ag atoms in the interface layer was observed in the Ag-Cu alloy, and unexpected mixing between graphite substrate and the Ag-Ga melt was also detected in the solidified structure.

Abstract: Those materials with an one dimensional phase-aligned structure have a large amount of potentiality as engineering materials because of their exceptional optical, electrical and anisotropically mechanical properties. Many researchers are now working determinedly to explore the methods for fabricating this kind of material. Recently, high magnetic fields have been used to fabricate non-magnetic materials with textured structure where anisotropic magnetic energy should be strong enough to induce preferred crystal orientation. Based on this mechanism, we developed an in situ process for fabricating phase-aligned composites using high magnetic fields. In this work, hypoeutectic Mn-Sb and hypereutectic Al-Ni alloys were solidified in various magnetic fields. The primary MnSb dendrites in the solidified Mn-Sb alloys were found to be macrostructurally aligned along the field direction, while the primary Al3Ni phases in the Al-Ni alloys were found to be macrostructurally aligned perpendicular to the field direction. The X-ray diffraction (XRD) measurement results suggested that these two phases were also oriented by the magnetic field. It was believed that the above-mentioned alignment is based on the crystal orientation and relevant to the heat flux direction, the preferred growth direction and the concentration field around crystallized crystals.

Abstract: The Cu-line patterns with different linewidth were deposited by radio-frequency sputtering and defined by photolithography lift-off process. The residual stress was evaluated with X-ray diffraction technique and the results show that the Cu-line patterns are in a biaxial stress state and the stress values have a great dependence on linewidth. Further analysis reveals that the intrinsic stress has a main effect on changes of residual stress; however, the thermal stress plays a key role on anisotropic contribution of residual stress in directions along and across the Cu line. The variation of intrinsic stress correlates well with crystal orientation of the Cu line, and the linewidth seems to be the most crucial parameter for evolution of both texture and stress.

Abstract: A Bi2Te3-based thermoelectric semiconductor was subjected by high pressure torsion (HPT). Sample disks of p-type Bi0.5Sb1.5Te3.0 were cut from sintered compacts that were made by mechanically alloying (MA) followed by hot pressing. Disks were subjected by HPT with 1, 5 and 10 turns at 473 K under 6.0 GPa of pressure. Crystal orientation was investigated by X-ray diffraction. Microstructures were characterized using scanning electron microscopy. Results indicated that HPT disks after 5 turns had a preferred orientation and a fine grain compared with pre-HPT disks while the orientation factor was decreased after HPT using 10 turns. The power factor had a maximum value at 5 turns as determined by measuring its thermoelectric properties. A maximum power factor of 4.30×10-3 Wm-1K-2 was obtained for HPT disks after 5 turns. This value was larger than that for the pre-HPT disk. The over-HPT of 10 turns was found to have caused a decrease in the preferred orientation leading to a low power factor.

Abstract: We investigated electrical properties of epitaxial Mn doped bismuth ferrite BiFe0.97Mn0.03O3 (BFMO) thin films with different crystal orientations deposited on Si substrates with appropriate buffer layers. Epitaxial SrRuO3 (SRO) thin films with (001), (101), and (111) orientations were grown on CeO2/yttria-stabilized zirconia (YSZ)/Si(001) substrates and YSZ/Si(001), respectively, by the insertion of MgO and TiO2 atomic layers using pulsed-laser deposition (PLD). Using spin coating, we deposited BFMO thin films onto orientated SRO thin films. The BFMO orientation followed the SRO orientation. The Pr values of the BFMO were ordered as follows {111}>{110}>{100}, which is the same as that predicted by crystallographic considerations. The largest Pr value of the {111} orientation is 76 μC/cm2 at 100 kHz, 25°C.

Abstract: Au/NiCr/Ta soft multi-layered metal films were deposited on hard Si-(111) substrate by magnetron sputtering. The crystal orientation, Hardness (H) and Elastic modulus (E) were investigated as a function of substrate temperature by XRD and nanoindentation techniques. The XRD revealed that all films on Si-(111) substrate are Au-(111) preferred orientation, indicating there are no alloying phases in the films, which is different from Au/NiCr/Ta films on Al2O3 substrate with a mixture of Au-(111) and Au-(200) orientation. Nanoindentation tests at shallow indentation depths (h≤t/4) where the hardness is reliable for metal films on hard substrate. Au film at substrate temperature 200°C has the highest hardness 4.2GPa. Meanwhile, the H/E value also indicated that the Au/NiCr/Ta films have preferable wear resistance at substrate temperature 200°C.

Abstract: In general, magnesium metal is not used as uncoated material on account of its corrosion characteristic. This work was done by preparing 99.99% pure magnesium coating films by RF magnetron sputtering onto SPCC substrates [1]. The individual preparation conditions of gas pressures and bias voltages were 1×10-2 ~ 1×10-3 Torr and 0V ~ -300V, respectively. The analysis about crystal orientation, morphology and electrochemical characteristic of Mg thin films was performed by using X-ray diffraction (XRD), field emission scanning electron microscopy (FESEM), electrochemical impedance spectroscopy (EIS) etc.. It is as a results of experiment that the morphology of the sputtered films changed from a columnar structure to a granular structure when Ar gas pressure increased or bias voltage decreased. Also, the prepared Mg thin film’s morphology did not have defects and pinholes, and the corrosion resistance was improved by the formation of a homogeneous passive layer.

Abstract: We have used synchrotron x-ray diffraction to study the crystal orientation in human dental enamel as a function of position within intact tooth sections. Keeping tooth sections intact has allowed us to construct 2D and 3D spatial distribution maps of the magnitude and orientation of texture in dental enamel. We have found that the enamel crystallites are most highly aligned at the expected occlusal points for a maxillary first premolar, and that the texture direction varies spatially in a three dimensional curling arrangement. Our results provide a model for texture in enamel which can aid researchers in developing dental composite materials for fillings and crowns with optimal characteristics for longevity, and will guide clinicians to the best method for drilling into enamel, in order to minimize weakening of remaining tooth structure, during dental restoration procedures.

Abstract: The protein adsorption behavior was investigated for highly (001) oriented hydroxypatatite coatings (HACs). Highly (001) oriented (HO-) HACs and HAC with low orientation (LO-HAC) were prepared on titanium (Ti) substrates through a radio-frequency thermal plasma spraying method. Sintered HA pellets (S-HA) was also prepared as a control. The solution of 22 'g/100 'l PBS of the fluorescein-isothiocyanate (FITC) labeled bovine serum albumin (FITC-BSA), immunoglobulin G (FITC-IgG) and cytochrom c (FITC-CCC) was separately dropped on the surface of HACs and was incubated for 30 min. After the incubation, such HACs were washed with the PBS additionally supplemented with 125mM NaCl and observed using a fluorescence microscope. Fluorescence microscopic examination indicates that FITC labeled proteins somewhat adsorbed on the HACs, while proteins adsorbed little on S-HA surface. In particular, it can be seen that FITC-CCC adsorbed more prominently on the HO-HAC.

Abstract: The effect of crystal orientation on the recovery and recrystallization of cold-rolled Ni (99.96% purity) has been investigated. Particular attention was paid to the annealing response of regions with either the Copper (C), Brass (B) or S rolling texture orientations. Samples with an initial average grain size of approx. 500μm were deformed to strains of up to εvM = 4.5. As a result of the large initial grain size, even after high rolling reductions it is possible to find sufficiently large regions of material with similar crystal orientation to analyze the recovery and recrystallization behaviour as a function of crystal orientation. Microstructural investigations were carried out in the scanning electron microscope using both electron channeling contrast and electron backscatter diffraction orientation mapping. Both the S and C orientation regions exhibit a heterogeneous microstructure containing bands of localized deformation. The presence of volumes surrounded by high angle boundaries in these regions strongly influences both the recovery and recrystallization behaviour of the material. Twinning was observed also to play an important role in the generation of recrystallized grains, with twin chains of up to 3 generations being observed.