Rapid nickel diffusion in cold-worked carbon steel at 320–450 °C

The diffusion coefficient of nickel in cold-worked carbon steel was determined with the diffusion couple method in the temperature range between 320 and 450 °C. Diffusion couple was prepared by electro-less nickel plating on the surface of a 20% cold-worked carbon steel. The growth in width of the interdiffusion zone was proportional to the square root of diffusion time to 12,000 h. The diffusion coefficient (D_Ni) of nickel in cold-worked carbon steel was determined by extrapolating the concentration-dependent interdiffusion coefficient to 0% of nickel. The temperature dependence of D_Ni is expressed by D_Ni = (4.5 + 5.7/?2.5) × 10^?11 exp (?146 ± 4 kJ mol^?1/RT) m²s^?1. The value of D_Ni at 320 °C is four orders of magnitude higher than the lattice diffusion coefficient of nickel in iron. The activation energy 146 kJ mol^?1 is 54% of the activation energy 270.4 kJ mol^?1 for lattice diffusion of nickel in the ferromagnetic state iron.     

Effects of water and alcohol on the formation of inclusion complexes of d-limonene and cyclodextrins

Abstract

Systematic studies have been carried out on the role of water and alcohol in the formation of inclusion complexes between d-limonene and α-, β- and γ-cyclodextrin (CD) by a micro-aqueous method. The inclusion complex was barely formed at zero water content for all CDs. Above the specific water content for each CD, formation of the inclusion complex correlated well with an equation which was derived on the autocatalytic assumption for the inclusion phenomenon. The inclusion complex correlated well with an equation which was derived on the autocatalytic assumption for the inclusion phrnomenon. The minimum water content, which was defined as 1% of the maximum concentration of the inclusion complex formed, coincided with the number of water molecules inside the cavity of the CD. In the presence of ethanol, a significant amount of the inclusion complex was formed for β- and γ-CD/limonene systems, particularly at lower moisture content. However, for α-CD the inclusion fraction decreased significantly in the presence of ethanol. This means that ethanol inhibits the formation of the inclusion complex between x-CD and d-limonene. For other linear alcohols, the formation of the inclusion complex between d-limonene and β-CD increased with decreasing alkyl chain length. This suggests that the more hydrophilic and the smaller (in molecular size) the alcohol is, the more enhanced is the inclusion of d-limonene to β-CD.     

Effects of thermal history on enthalpy relaxation

The effects of the thermal history on enthalpy relaxation in polymethylmethacrylate (PMMA) have been studied by differential scanning calorimetry (DSC). The temperature dependence of specific heat capacity in the liquid and glassy states, that of relaxation time and the exponent of the Kohlrausch–Williams–Watts function have been obtained by the measurement of the response of heat flux to the sinusoidal temperature variation. The phenomenological model equation as an extension of linear rheology has been applied to enthalpy relaxation. The evolution of entropy under a given thermal history same as the experiment has been calculated and compared with the DSC results. The calculated results reproduce two peaks of specific heat capacity at lower and higher temperatures in the glass transition region: the former is characteristic of PMMA and the latter is observed in typical glassy polymers.     

Fabrication of large‐sized silica monolith exceeding 1000 mL with high structural homogeneity

Reproducible fabrication of the hierarchically porous monolithic silica in a large volume exceeding 1000 mL has been established. By the hydrothermal enlargement of the fully accessible small pores to exceed 50 nm in diameter, the capillary force emerged on solvent evaporation was dramatically reduced, which allowed the preparation of crack‐free monoliths with evaporative solvent removal under an ambient pressure. The local temperature inhomogeneity within a reaction vessel in a large volume was precisely controlled to cancel the heat evolved by the hydrolysis reaction of tetramethoxysilane and that consumed to melt ice cubes dispersed in the solution, resulting in large monolithic silica pieces with improved structural homogeneity. Homogeneity of the pore structure was confirmed, both on macro‐ and mesoscales, using SEM, mercury intrusion, and nitrogen adsorption/desorption measurements. Furthermore, the deviations in chromatographic performance were examined by evaluating multiple smaller monolithic columns prepared from the monolithic silica pieces cut from different parts of a large monolith. All the daughter columns thus prepared exhibited comparable performances to each other to prove the overall homogeneity of the mother monolith. Preliminary results on high‐speed separation of peptides and proteins by the octadecylsilylated silica monolith of the above production have also been demonstrated.     

Synthesis of silyl-functionalized oligothiophene-based polymers with bright blue light-emission and high refractive index

In this paper, we report the synthesis of partially conjugated polymers with a silyl-group-substituted oligothiophene and a short alkyl chain in the main chain by hydrosilylation polymerization and describe their optical properties such as luminescence and refractive index. The obtained polymers are found to have good solubility and processability. Moreover, the high steric hindrance of the silyl-group can inhibit the π-π interaction and intermolecular aggregation of the polymers. Hence, the emission of the obtained polymers was similar to that of the corresponding silyl-group-substituted oligothiophene. The polymers exhibit intense light blue fluorescence under UV irradiation and a high refractive index in the visible light region.     

213 W average power of 2.4 GW pulsed thermally controlled Nd:glass zigzag slab laser with a stimulated Brillouin scattering mirror

We report a high-average-power and high-pulse-energy diode-pumped Nd:glass laser amplifier system consisting of two thermally-edge-controlled zigzag slab amplifiers and a stimulated Brillouin scattering mirror. This phase-conjugated system produces an average power of 213 W at 10 Hz in a 8.9 ns pulse (2.4 GW peak power) with an optical-to-optical conversion efficiency of 11.7% and a near-diffraction-limited beam. To the best of our knowledge, this is the highest performance from a Nd:glass-based laser amplifier system ever built.     

Development of a new molecular dynamics method for tribochemical reaction and its application to formation dynamics of MoS2 tribofilm

Recently we have developed a novel molecular dynamics program NEW-RYUDO-CR, which can deal with chemical reactions. The developed method has been applied to the study of tribochemical reaction dynamics of MoS₂ tribofilm on iron surface. The initially amorphous MoS₂ layer self-organized its structure as result of the tribochemical reactions and formed layered MoS₂ tribofilm. The friction coefficient significantly decreased as the MoS₂ tribofilm was formed. Besides, sliding was observed between sulfur layers of MoS₂ tribofilms which occurred due to repulsive Coulombic interaction forces between sulfur atoms. This indicates that the formation of the layered MoS₂ tribofilm is important to achieve better lubrication properties.     

Observing quantum correlation of photons in Laguerre-Gauss modes using the Gouy phase

The effect of the Gouy phase, which is one of the geometrical phases of photons, is observed through quantum correlation in Laguerre-Gaussian (LG) modes. In an experiment, the relative phase of two different LG modes of measurement basis states is manipulated via the Gouy phase, and the observed coincidence count rates agree well with theoretical predictions. This result suggests that the Gouy phase can be used as a new tool to manipulate multidimensional photonic quantum states.     

Phase-contrast X-ray imaging of the gas diffusion layer of fuel cells

The understanding of and in situ observation of the transport and distribution of water in carbon‐paper gas diffusion layers (GDLs) using non‐destructive imaging techniques is critical for achieving high performance in polymer electrolyte fuel cells (PEFCs). To investigate the behavior of water in GDLs of PEFCs, phase‐contrast X‐ray imaging via X‐ray interferometric imaging (XII) and diffraction‐enhanced imaging (DEI) were performed using 35 keV X‐rays. The XII technique is useful for the radiographic imaging of GDLs and in situ observations of water evolution processes in operating PEFCs. DEI provides a way for tomographic imaging of GDLs in PEFCs. Because high‐energy X‐rays are applicable to the imaging of both carbon papers and heavy materials, which make up PEFCs, phase‐contrast X‐ray imaging techniques have proven to be valuable for investigation of GDLs.     

Inteferences in neutron and photon activation analysis

The effect of following interferences was quantitatively assessed in terms of interference factor by irradiating samples together with highly pure reagents at two reactor sites of diferent neutron spectra and fluxes for neutron activation analysis (NAA) and an electron LINAC for photon activation analysis (PAA). The interfering reactions studied are 91) fast neutron-induced reactions, (2) uranium fission (3) (n,γ) reactions of other target elements in NAA, and (4) reactions induced by secondary neutrons in PAA. Corrections for these interferences were successfully applied to the activation analysis of some geological reference rock samples and biological samples.