Laser-Induced Line Patterning of Nonlinear Optical Crystals in Glass

This paper reports the progress in the patterning of nonlinear optical crystal lines on a glass surface by laser irradiation techniques. Two techniques for the patterning of crystal lines have been developed, i.e., rare-earth atom heat processing and transition metal atom heat processing, in which continuous-wave lasers such as Nd:YAG laser (wavelength: lambda = 1064 nm) are irradiated onto the glasses containing rare-earth ions such as Sm³⁺ and Dy³⁺ or transition metal ions such as Ni²⁺ and Cu²⁺. The patterning of lines consisting of nonlinear optical crystals such as beta-BaB₂O₄, SmxBi_1- xBO₃, (Sr,Ba)Nb₂O₆, and LiNbO₃ has been achieved. It is clarified from the azimuthal dependence of second harmonic intensities and polarized micro-Raman scattering spectra that nonlinear optical crystals in the lines are highly oriented along the laser scanning direction, i.e., the patterning of single-like crystal lines. It is also possible to pattern two-dimensional crystal bending or curved lines by just changing the laser scanning direction, and such bending crystal lines have a potential for optical waveguides.     

Effect of in-flight particle behavior on the morphology of flame sprayed Er2O3 splats

The morphology and microstructure of splats impact the comprehensive capability of a new coating methodology called chelate flame spraying (CFS). This study addresses the quantitative characterization of the spread morphologies of flame sprayed Er₂O₃ splats directly deposited under different spray conditions on aluminum alloy substrates with a mirror finish. The influence of the in-flight particle temperature and velocity, carrier gas type, and carrier gas ratio on the solidification mechanism of molten droplets was investigated. Image analysis methods were employed to identify single splats from the morphology observed with field-emission scanning electron microscopy (FE-SEM). In addition, Er₂O₃ films were synthesized on an Al–Mg alloy (A5052) substrate using N₂ or O₂ as the carrier gas. When O₂ was used as the carrier gas, 109-μm-thick films were deposited on the A5052 substrate. The cross-sectional porosity of the films was 3.8%. In contrast, films with 101-μm thickness were synthesized on the A5052 substrate when N₂ was used as the carrier gas. The cross-sectional porosity of these films was 13.8%. The results showed that the carrier gas type (N₂) and carrier gas ratio had a significant effect on the flattening behavior of the molten droplets. A spraying method combined with multidimensional modes is proposed to control the morphology of the splats.     

Pressureless all-solid-state sodium-ion battery consisting of sodium iron pyrophosphate glass-ceramic cathode and β″-alumina solid electrolyte composite

In recent years, the expansion of demand for lithium ion batteries has resulted in soaring prices of the constituent resources. From the viewpoint of safety, studies on all-solid-state batteries are actively being carried out. In this study, we succeeded in driving all-solid-state batteries derived from nontoxic oxide glasses at room temperature without requiring scarce resources such as lithium and cobalt. The main structure of the ceramic batteries with a simple structure in which Na₂FeP₂O₇ crystallized glass and β″-alumina solid solution are joined by pressureless cofiring at 550°C. During the crystallization of Na₂O-Fe₂O₃-P₂O₅ glass, fusion with the β″-alumina solid solution is achieved. Reversible charge and discharge of 80 mAh/g were achieved at room temperature. It is not necessary to apply pressure during cell preparation or the use of the batteries. Furthermore, the strong junction at the cathode and electrolyte interface does not peel off during charge and discharge over a long period of 623 cycles. Ex situ X-ray photoelectron spectroscopy revealed partial Fe⁴⁺ induction and a reversible charge and discharge reaction even after overcharging to 9 V. It was demonstrated that Na₂FeP₂O₇ is very stable against overcharging to 9 V.     

Jamming layered membrane gripper mechanism for grasping differently shaped-objects without excessive pushing force for search and rescue missions

A gripper comprising a jamming membrane was developed with the capability of grasping collapsible, soft, and fragile objects without applying heavy pressure. In disaster sites, it is necessary for robots to grab various types of objects, such as fragile objects. Deformable grippers that contain bags filled with powder cannot handle collapsible or soft objects without excessive pressure. Changing powder density relatively by changing inner volume is one approach to overcome this problem. By expanding the concept and simplifying the variable inner volume of the gripping mechanism, we developed a jamming membrane comprising the following three layers: outer layer and inner layer made of rubber and a powder layer in between the outer and inner rubber layer. This jamming membrane allows collapsible, soft, or fragile objects to be held securely without applying too much pressure. We designed and developed a prototype of the jamming membrane gripper. Our experiments confirmed the validity of the proposed jamming membrane mechanism.     

Synthesis of C2H4 by partial oxidation of CH4 over LiCl/NiO

Alkali halide added transition metal oxides produced ethylene selectively in oxidative coupling of methane. The role of alkali halides has been investigated for LiCl-added NiO (LiCl/NiO). In the absence of LiCl the reaction over NiO produced only carbon oxides (CO₂ + CO). However, addition of LiCl drastically improved the yield of C₂ compounds (C₂H₆ + C₂H₄). One of the roles of LiCl is to inhibit the catalytic activity of the host NiO for deep oxidation of CH₄. The reaction catalyzed by the LiCl/NiO proceeds stepwise from CH₄ to C₂H₄ through C₂H₆ (2CH₄ → C₂H₆ → C₂H₄). The study on the oxidation of C₂H₆ over the LiCl/NiO showed that the oxidative dehydrogenation of C₂H₆ to C₂H₄ occurs very selectively, which is the main reason why partial oxidation of CH₄ over LiCl/NiO gives C₂H₄ quite selectively. The other role of LiCl is to prevent the host oxide (NiO) from being reduced by CH₄. The catalyst model under working conditions was suggested to be the NiO covered with molten LiCl. XPS studies suggested that the catalytically active species on the LiCl/NiO is a surface compound oxide which has higher valent nickel cations (Ni^(2+δ)+ or Ni³⁺). The catalyst was deactivated at the temperatures>973 K due to vaporization of LiCl and consumption of chlorine during reaction. The kinetic and CH₄---CD₄ exchange studies suggested that the rate-determining step of the reaction is the abstraction of H from the vibrationally excited methane by the molecular oxygen adsorbed on the surface compound oxide.     

Superconducting Coupling Nature at Grain Boundaries in Bi2Sr2CaCu2Ox Glass-Ceramics

Superconducting coupling nature at grain boundaries in Bi₂Sr₂CaCu₂O _x glass-ceramics consisting mainly of the low- T _c phase was first examined by measuring superconducting properties and temperature or ac field dependence of ac complex susceptibility. It was found from the ac loss peaks that superconducting coupling at grain boundaries was basically characterized by three types of weak links. The weak-link behaviors at grain boundaries depended strongly on cooling conditions after annealing and annealing time and temperature. Particularly, it was found that the weak links at grain boundaries were improved by prolonged annealing at 840°C. The furnace-cooled glass-ceramics obtained by annealing at 820° or 840°C for about 200 h exhibited a critical transport current density (77 K, zero magnetic field) of about 200 A/cm².     

Crystalline Phases and YAG Laser-Induced Crystallization in Sm2O3–Bi2O3–B2O3 Glasses

The glass formation region, crystalline phases, second harmonic (SH) generation, and Nd:yttrium aluminum garnet (YAG) laser-induced crystallization in the Sm₂O₃–Bi₂O₃–B₂O₃ system were clarified. The crystalline phases of Bi₄B₂O₉, Bi₃B₅O₁₂, BiBO₃, Sm _x Bi_{1− x} BO₃, and SmB₃O₆ were formed through the usual crystallization in an electric furnace. The crystallized glasses consisting of BiBO₃ and Sm _x Bi_{1− x} BO₃ showed SH generations. The formation of the nonlinear optical BiB₃O₆ phase was not confirmed. The formation (writing) region of crystal lines consisting of Sm _x Bi_{1− x} BO₃ by YAG laser irradiation was determined, in which Sm₂O₃ contents were∼10 mol%. The present study demonstrates that Sm₂O₃–Bi₂O₃–B₂O₃ glasses are promising materials for optical functional applications.     

Decoupling between Enthalpy Relaxation and Viscous Flow and Its Structural Origin in Fragile Oxide Glass-Forming Liquids

The structural relaxation kinetics at the glass transition in tellurium oxide (TeO₂)-based glasses has been examined from viscosity and heat-capacity measurements to clarify the features of the structural relaxation in fragile oxide glass-forming liquids. A large decoupling between enthalpy relaxation and viscous flow, i.e., a large discrepancy between the activation energies for the enthalpy relaxation (recovery), Δ H , and viscous flow, E _η, has been demonstrated in TeO₂-based glasses. The values in x K₂O· x MgO·(100 − 2 x )TeO₂ glasses, for example, are ∼919–1051 kJ/mol for Δ H and ∼ 577–701 kJ/mol for E _η, given the ratio of Δ H/E _η≈ 1.44–1.59. Some viscosity and heat-capacity data (all data have been reported previously) obtained from similar experiments in Sb₂O₃–B₂O₃ glasses belonging to the category of strong glass-forming liquids have been reanalyzed in this paper for comparison; a strong coupling was found to exist between Δ H and E _η, i.e., Δ H/E _η≈ 0.98–1.18. An origin of decoupling between Δ H and E _η in fragile glass-forming systems such as TeO₂-based glasses has been discussed by considering the glass structure model for fragile glasses; strongly bonded correlated (highly constrained) regions are surrounded or connected by weakly bonded noncorrelated (unconstrained) parts.