Larson–Miller Constant of Heat-Resistant Steel

Long-term rupture data for 79 types of heat-resistant steels including carbon steel, low-alloy steel, high-alloy steel, austenitic stainless steel, and superalloy were analyzed, and a constant for the Larson–Miller (LM) parameter was obtained in the current study for each material. The calculated LM constant, C, is approximately 20 for heat-resistant steels and alloys except for high-alloy martensitic steels with high creep resistance, for which $ C \approx 30 $ . The apparent activation energy was also calculated, and the LM constant was found to be proportional to the apparent activation energy with a high correlation coefficient, which suggests that the LM constant is a material constant possessing intrinsic physical meaning. The contribution of the entropy change to the LM constant is not small, especially for several martensitic steels with large values of C. Deformation of such martensitic steels should accompany a large entropy change of 10 times the gas constant at least, besides the entropy change due to self-diffusion.     

Lattice dynamics of Mg2Si and Mg2Ge compounds from first-principles calculations

We report first-principles calculations of the structure, elastic properties, lattice dynamics and some thermodynamic properties of Mg₂Si and Mg₂Ge compounds. The fully relaxed structure parameters and elastic stiffness constants of Mg₂Si and Mg₂Ge compounds are in good agreement with previous experimental data. The linear response method is applied to determine the phonon dispersion relations, phonon density of states, and Born effective charge. The computed thermodynamic properties such as vibrational entropy, constant-volume specific heat, and Debye temperature coincide with previous experimental data.     

Direct Evidence for Structural Transition Promoting Shear Thinning in Cylindrical Colloid Assemblies

In this paper, we describe stimuli‐responsive hydrogels prepared from a rigid rod‐like polyelectrolyte ‘imogolite’ and a dicarboxylic acid. The hydrogel exhibited thixotropy in response to mechanical shock within the order of seconds or sub‐seconds. Here, using the latest structural/rheological characterisation techniques, the relationship between the structural transition processes and the shear thinning was estimated. The evidence obtained by the experiments revealed for the first time the direct relationship between the microscopic structural change and the macroscopic thixotropic behavior that have been extensively discussed. The thixotropic hydrogel has the hierarchical architecture in the combination of imogolite and dicarboxylic acid, i.e., sheathed nanotubes/hydroclusters of cross‐bridged nanotubes/frameworks. The formation and disintegration of the network structure upon resting and agitating, respectively, were the origin of gel/sol transition (thixotropy), although the hydroclusters of cross‐bridged nanotubes were maintained throughout the transition.     

Evaluation method of check-valve integrity during sudden closure using thermal-hydraulic and structural analyses

The Advanced Thermal Reactor (ATR), a boiling-water-cooled, heavy-water-moderated, pressure-tube type reactor, has a series of check-valves just upstream of a water drum that serves as a distributing header for fuel channels. In the case of a hypothetical guillotine break upstream of the water drum, the check-valve integrity is a key issue for reactor safety during rapid closure. Pipe break experiments adjacent to and far from the water drum were conducted to measure the deformation of the valve and the water hammer behavior. Fastest disk impact was observed in the case of an adjacent break and water hammer was observed in the case of a break far from the valve. An evaluation method of valve integrity after the rapid closure to be taken over by the simple method is proposed. In the present study, the thermal-hydraulic analysis is conducted using the HITSL code with a dynamic check-valve model, and structural analysis is conducted by the DYNA3D code. Both behaviors relating thermal-hydraulics and structure are traced by these codes.     

Supramolecular assemblies of oligothiophene derivatives bearing β-cyclodextrin

2T-βCD₂ and 3T-βCD₂, which have bithiophene (2T) and terthiophene (3T) with β-cyclodextrin (CD) at each end form supramolecular assemblies in aqueous solutions. These supramolecular assemblies were characterized by NMR, UV, fluorescence spectroscopy, circular dichroism spectroscopy, and atomic force microscope (AFM). Supramolecular assemblies from 3T-βCD₂ form orientated structures due to their π–π stacking ability. AFM images of the supramolecular assembly incorporating 3T-βCD₂ showed fibrous objects on mica substrates.     

Removal of polycyclic aromatic hydrocarbons from contaminated soil by aqueous DNA solution

An aqueous DNA solution was applied for the extraction of polycyclic aromatic hydrocarbons (PAHs) from a spiked soil. Solubilities of 0.56, 11.78, and 11.24 mg L(-1) for anthracene, phenanthrene, and pyrene, respectively, were achieved after 1 day equilibration in 1% DNA. Using a spiked soil that contained 72 mg kg(-1) anthracene, 102 mg kg(-1) phenanthrene, and 99 mg kg(-1) pyrene, extractions of close to 88, 78, and 94%, respectively, were attained with 5% DNA at a 1:50 soil/extractant ratio. Maximum PAH dissolution occurred after 4-6 h. Comparative tests showed the main advantage of DNA over methyl-beta- and gamma-cyclodextrins and Tween 80 for pyrene removal. An ionic strength of 0.1 M NaCl was found necessary for maximum PAH dissolution and extraction. The performance of hexane regenerated DNA also remained stable after three stages of recycling. These results show the huge potential of DNA as an aqueous washing agent for PAH-contaminated soil.