Colloidal Consolidation of Ceramic Nanoparticles by Pressure Filtration

The applied pressure and suspension height during consolidation of an aqueous suspension of nanometer-sized particles (24 nm hydroxyapatite, 30 nm SiC, 68 nm 8 mol% yttria-stabilized zirconia, 150 nm Al₂O₃, and 800 nm SiC) were continuously recorded using a pressure filtration apparatus. The packing density decreased when the particle size was less than 70 nm. The final packing density of 150−800 nm particles at 19 MPa was strongly influenced by the surface charge. However, surface charge does not affect the packing density of particles less than 70 nm. The ratio of the energy applied to two particles during consolidation to the interaction energy between two particles in a suspension was correlated to the packing density. The low packing density of 20−30 nm particles was improved by steric stabilization. The estimated thickness of the dispersant layer adsorbed on the particle surfaces was less than 1 nm and nearly independent of the molecular weight of the dispersants. When the applied pressure was released, the height of the consolidated cake increased because of the release of the elastic strain stored in the dispersant layer.     

Direct Evidence of Dopant-Enhanced Grain-Boundary Sliding in Yttria-Stabilized Zirconia Bicrystals

Compression tests were conducted at 1400°C in air for undoped and Si-doped yttria-stabilized zirconia (YSZ) bicrystals with the same orientation relationship (Σ=5, [001]/{210} grain boundary). It was found that the macroscopic grain-boundary slidings are observed during the deformation in both undoped and doped bicrystals, and the sliding displacements increase almost linearly with increasing total displacements. It is distinctly demonstrated that the Si-doped bicrystal exhibits a sliding displacement that is a few times larger than the undoped bicrystal. In addition, the total strain of the Si-doped bicrystal at a failure is much larger than that of the undoped bicrystal. It can be stated that Si doping in YSZ not only enhances the grain-boundary sliding but also suppresses its failure.     

Phase transition and the packing structure of the side mesogenic groups of liquid crystalline side-chain copolymers

Summary Copolymers consisting of cholesteryl 11-methacryloyloxy-undecanoate (ChMO-10) and t-buthyl methacrylate (t-BMA) were studied by DSC method and by small angle X-ray scattering method (SAXS). Although homopolymer (pChMO-10) has two different packing structures which are a single-layer packing structure and a two-layer packing one, copolymers (co-pChMO-10-t-BMA) have only the single layer packing one in their mesophase. Furthermore, transition entropy at a clearing point of co-pChMO-10-t-BMA (80/20) is larger than that of pChMO-10. Adequate distance of the mesogenic groups in the direction of a short axis of the mesogenic groups, produced by introduction of non-mesogenic units, seems to stabilize the single-layer packing structure.     

Instrumented charpy impact test of epoxy resin filled with irregular-shaped silica particles

The effect of particle size on the impact properties of an epoxy resin has been studied. This resin was filled with irregular-shaped silica particles prepared by crushing fused natural raw quartz. These particles were sorted into six groups of different mean sizes ranging from 2 to 47 μm. The impact properties were measured by an instrumented Charpy type impact tested, which can record a load-displacement curve during impact fracture. The impact absorbed energy (U) was measured using specimens having a U-shaped blunt notch, and the impact fracture toughness (K_CI) was measured using specimens having a sharp crack introduced by a fresh razor blade. As the particle size decreased. U increased and K_CI decreased. The fractured surfaces and crack tip regions were observed using a scanning electron microscope to clarify the above phenomena.     

UV-Curable Adhesives For Optical Communications

UV-curable optical adhesive systems featuring refractive indices in the 1.45 to 1.59 region controllable to within 0.005 are developed using new fluoro-epoxies and fluoro-epoxy (meth) acrylates. These adhesives possess excellent refractive index matching with optical glass and optical fibres, and the joints exhibit high bonding strength and good durability. These high performance adhesives are readily applicable as optical adhesives in fabricating optical components, attaching fibres to optical waveguides, and splicing optical fibres for optical communications.     

Dopamine D2, D3 and D4 receptor and transporter gene polymorphisms and mood disorders

Disturbances in dopaminergic systems have been implicated in the etiology of mood disorders. Although genetic factors also play an important role, no major gene has been identified. We conducted an association study using the dopamine D2, D3 and D4 receptor, and transporter gene polymorphisms, comparing 101 mood-disorder patients (52 bipolar and 49 unipolar) and 100 controls. Our results suggest that there is a significant association between the dopamine D4 receptor gene and mood disorders, especially major depression, but no association between the other polymorphisms and mood disorders. Further investigations are needed to clarify the clinical significance of this association in the pathophysiology of mood disorders.     

Radiocarbon dating of charred human bone remains preserved in urns excavated from medieval Buddhist cemetery in Japan

For a preliminary test of ¹⁴C dating of cremated human remains, we have collected charred bone and wood–charcoal fragments from cremated remains contained in cinerary urns that had been excavated from medieval Buddhist cemetery at the Hoenji temple in Aichi prefecture, central Japan. More than 230 urn vessels were discovered from the excavated area of ca. 14 m wide and 14 m long. The identification of charred bone or charcoal fragments among the remains was performed by observation of surface appearance, inspection of fine structures by a microscope, bubble formation during the HCl treatments in preparing target material for AMS ¹⁴C dating, carbon and nitrogen contents, δ¹³C and δ¹⁵N values of the fragments. All ¹⁴C ages obtained for the samples that were identified as charred bone remains were almost consistent with the archeological age estimated based on typological analysis of respective urns. On the other hand, some ¹⁴C ages for the remains identified as wood charcoal, which had been produced from firewood or a wooden coffin during the cremation, were not consistent with archeological estimation, shifting toward older ¹⁴C ages, most probably as the result of old wood effect.     

Homogenizing behaviour in a hydrogen-absorbing LaNi4.55Al0.45 alloy through annealing and rapid quenching

Homogenizing behaviour in a hydrogen-absorbing alloy with a composition of LaNi_4.55Al_0.45 through annealing and rapid quenching was investigated to improve its equilibrium characteristics with hydrogen. Annealing has an effect on homogenizing the Al distribution in the dominant phase of CaCu₅ structure and decreasing the plateau slope in the P-C isotherms. The rapidly quenched alloy exhibited a flatter but narrower plateau region than the induction-melted and annealed alloy, which became wider after short-time annealing for 7.2 ks at 1323 K. The effect of the annealing in the rapidly quenched alloy was attributed to a decrease in lattice defects introduced by the rapid quenching process.     

Determination of Thermal Spray Coating Property with Curvature Measurements

Real-time curvature measurement of a coating-substrate system during deposition has facilitated the monitoring of coating stresses and provided additional insights into thermal spray deposition mechanisms. However, the non-equilibrium state of coating formation along with harsh spray booth environment introduces complexity not only in data interpretation but also in the coating properties estimation. In this paper, a new procedure is proposed to estimate the elastic modulus of thermal sprayed ceramic coatings using in situ curvature and temperature measurements. In order to correlate the measurable parameters to coating elastic modulus, a systematic study is conducted to develop a suitable methodology. First, various finite element model analyses are carried out to formulate suitable relations between the measurements and elastic modulus. Subsequently, experiments are conducted to validate the procedure to estimate coating moduli. The results are compared with more accurate measurements obtained from post-deposition characterization technique under low temperature thermal cycles. The comparison suggests that the moduli estimated using the proposed procedure are in good agreements with those obtained from the post-deposition technique. Further, the nonlinear response of coatings are evaluated from the estimated moduli during deposition and cool down, which offer additional information on the characteristics of thermal spray coatings.     

Fundamental research of laser micro welding for practical use of titanium eyeglass frames

Micro welding of titanium eyeglass frames requires sound strength, good exterior appearance and stable production, which suit micro laser welding. The objective of this work is to fundamentally investigate butt welding conditions with a pulsed yttrium aluminium garnet laser beam for exterior appearance and joint strength. Eleven factors of welding conditions which influence joint strength were evaluated from the viewpoint of quality engineering. It was found that two factors of defocused distance and processing of welding surface of the welding parts led to fluctuation of the joint strength. Therefore, sub-millimetre scale control of the laser irradiated point along the optical axis and the removal of impurities lead to brittle metallic compounds on the surface and produce sound strength of the joints. Furthermore, the optimized laser condition is applied to fabrication of components with the shape of titanium eyeglass frames. The qualities of the obtained joints were confirmed by a stripping test, cyclic bending test, metallographic observation and hardness determination. It was revealed that the laser welding method is more reasonable than conventional resistance brazing methods.