Absolute X-ray energy measurement using a high-accuracy angle encoder

This paper presents an absolute X-ray photon energy measurement method that uses a Bond diffractometer. The proposed system enables the prompt and rapid in situ measurement of photon energies over a wide energy range. The diffractometer uses a reference silicon single-crystal plate and a highly accurate angle encoder called SelfA. The performance of the system is evaluated by repeatedly measuring the energy of the first excited state of the potassium-40 nuclide. The excitation energy is determined as 29829.39 (6) eV, and this is one order of magnitude more accurate than the previous measurement. The estimated uncertainty of the photon energy measurement was 0.7 p.p.m. as a standard deviation and the maximum observed deviation was 2 p.p.m.

Effect of secondary crystal orientations on the deformation anisotropy for nickel-based single-crystal plate with notch feature

The effects of the secondary crystal orientations on the nickel-based single-crystal superalloy turbine blades were investigated. The stress concentration features were used for investigation of the optimal secondary crystal orientation leading to the higher strength of the single-crystal turbine blades. The crystal plastic finite element method coupled with micromechanics constitutive model is applied to study the effect of secondary crystal orientation on plastic deformation and mechanical behavior around the cooling holes and notches with the primary (load) orientation fixed at [001] direction. For nickel-based superalloy plates with holes or notches, the secondary crystal orientation effect on the strength needs to be clarified at various load levels. The maximum von Mises stress in the single-crystal alloy varies significantly with variation in the secondary crystal orientations. It was found that only two slip systems dominate the deformation process of the material owing to their favorable orientation with loading. The secondary orientation of 45° was identified with lowest resolved shear stress in the dominating slip systems and potential of producing higher strength for single-crystal turbine blades.

The Effect of Lattice Orientation on the Film Hole Deformation of Nickel-Based Single Crystal Plate Specimen

Based on the crystal plasticity theory, numerical simulation is implemented to calculate the equivalent strain field, resolved shear stress and sectional area of the cooling film hole. The results indicate that plastic strain and the distribution of resolved shear stress caused by multi-hole interference varies with different crystal orientations. Orientation [001] indicates relatively larger deformation than rest orientations. In the case of orientation [001], deformation concentrated at resolved shear stress zone between the holes, while orientation [011] and [111] appeared at the top and bottom of holes. Under the condition of multi-hole, compared to the single hole, the sectional area has a significant increase for orientation [001]. The sectional area changes substantially similar for orientation [011] and [111], but the sectional area is smaller than that in the case of single hole, with a sharp contrast to the formation of orientation [001].

Optical applications of wide-band-gap gallium oxide

Ga2O3 have been attracting much attention as a wide-band-gap semiconductor owing to a large band-gap of 4.8 eV and the availability of high-quality and large-sized single crystals, which are advantageous over conventional wide-band-gap semiconductors. This presentation focuses on optical applications using Ga2O3 single crystals: photodetectors and photoelectrodes, both of which show interesting and promising properties[1,2]. As for photodetectors, a PEDOT-PSS Schottky and In ohmic contacts were prepared on front and back surfaces of a n-type Ga2O3 single crystal plate, respectively, to fabricate a photovoltaic detector. The detector operated at zero bias (V = 0 V) exhibited high responsivities in the solar-blind region (< 280 nm). Incident photon to current conversion efficiency (IPCE) was as high as 21% at 240 nm and a 240-to-300 nm rejection ratio was as large as 10^4, indicating that the detector can be applicable for flame sensing. In fact, the detector successfully detected a flame by distinguishing several nW/cm2 weak solar-blind light from a flame under a strong fluorescent lamp illumination without using visible-cut filters. As for photoelectrodes, an n-type Ga2O3 single crystal plate with In ohmic contact on the back side was used for characterization. From impedance analysis, the conduction and valence band-edges in aqueous solutions were found to be 1.1 V higher and 2.5 V lower than the H+/H2 and O2/H2O redox potentials, respectively. These potential differences, or overpotentials for water splitting, are large enough for photolysis of water. When the photoelectrode was excited by photons, H2 and O2 gases evolved from a counter Pt electrode and the photoelectrode, respectively. The highest IPCE of 36% was obtained at 240 nm. Stoichiometric water splitting was demonstrated at V = 1V without using co-catalysts. These results encourage the notion of Ga2O3 optical applications and also contribute for developing Ga2O3 semiconductor studies.