Optimization of magnesium hydroxide composite material mixed with expanded graphite and calcium chloride for chemical heat pumps

A composite chemical heat storage material (EMC) comprising a mixture of expanded graphite (EG), magnesium hydroxide (Mg(OH)₂), and calcium chloride (CaCl₂) was developed as a magnesium oxide/water chemical heat pump reactant. The optimization of a mixing weight ratio between the Mg(OH)₂ content of EMC and EMC itself was discussed from the viewpoints of both heat storage capacity and reactivity by considering the reaction rate constants from a kinetic analysis. It was confirmed that the dehydration reactivity of EMC increased as the mixing weight ratio decreased; however, the heat capacity of the EMC unit mass decreased. A multiplied factor consisting of the multiplied value dehydration rate constant and mixing weight ratio was introduced. It was suggested that a weight ratio of approximately 0.80 was the optimized value when the mixing molar ratio between CaCl₂ and Mg(OH)₂ was 0.10. Dehydration of EMC with an optimized mixing weight ratio and dehydration of pure Mg(OH)₂ were conducted under various temperatures to compare the reaction rate constants of each material. From this study, it was demonstrated that EMC performed better on dehydration than pure Mg(OH)₂.     

Saccharification of alginate by using exolytic oligoalginate lyase from marine bacterium Sphingomonas sp. MJ-3

Alginate is a linear polysaccharide that is abundant in algal biomass. A novel recombinant exolytic oligoalginate lyase from a marine bacterium, Sphingomonas sp. MJ-3, was used for the saccharification of alginate into alginate monosaccharides in order to use alginate monosaccharides as renewable carbon source. The optimal heterologous expression condition for the MJ-3 oligoalginate lyase was determined, and the effects of saccharification reaction conditions were evaluated. Unsaturated monosaccharides up to 3.3 mg/ml were successfully prepared from 1% (w/v) alginate by using the recombinant oligoalginate lyase of Sphingomonas sp. MJ-3.     

Creep behaviour and long-term creep life extrapolation of alloy 617 for a very high temperature gas-cooled reactor

Creep behaviours for Alloy 617, such as creep properties, oxidation and creep fracture morphologies were investigated by a series of creep tests with different stress levels at 1223 K. Creep constants of A, n, m, and C were obtained at 1223 K for Alloy 617. To accurately predict the long-term creep life (or strength) for Alloy 617, a multi constant method with two C in the Larson-Miller (LM) parameter was newly proposed instead of the conventional one with a unique C. The conventional method did not thoroughly match with the creep rupture data, and revealed an overestimation for the prediction of the long-term creep strength. On the other hand, the multi constant method revealed a good agreement with the creep rupture data, and this method was more accurate than the conventional one. The multi constant analysis can be used to accurately predict the long-term creep rupture life of Alloy 617 above 10⁵ h for 1173 K, 1223 K and 1273 K.     

Evaluation of fatigue properties for aged 9Cr-1Mo steel

Low cycle fatigue tests of 9Cr-1Mo steel aged at 600°C for 5000 h and 10000 h were conducted at RT-600°C. Fatigue life was not decreased with aging. Cyclic softening was seen with cycles in both unaged and aged specimens. Aging decreased the amount of softening at RT and 400°C but increased it at 600°C. The precipitate species were not changed with aging upto 5000 h but Laves phase was precipitated after 10000 h aging. Fatigue life of 9Cr-1Mo steel aged to 10000 h is dependent on dislocation slip behavior rather than the amount and coarsening of precipitate.     

Investigation of flame characteristics using various design parameters in a pulverized coal burner for oxy‐fuel retrofitting

In oxy‐coal combustion for carbon capture and storage, oxygen and recirculated CO₂ are used as oxidizers instead of air to produce CO₂‐rich flue gas. Owing to differences between the physical and chemical properties of CO₂ and N₂, the development of a burner and boiler system based on fundamental understanding of the flame type, heat transfer, and NOx emission is required. In this study, computational fluid dynamic analysis incorporating comprehensive coal conversion models was performed to investigate the combustion characteristics of a 30 MWth tangential vane swirl pulverized coal burner. Various burner design parameters were evaluated, including the influence of the burner geometry on the swirl strength, direct O₂ injection, and O₂ concentrations in the primary and secondary oxidizers. The flame characteristics were sensitive to the oxygen concentration in the primary oxidizer. The performance of direct O₂ injection around the primary oxidizer with low O₂ concentration was dependent on the mixing of the fuel and oxidizer. The predictions showed that swirl number adjustment and careful direct oxygen injection design are essential for retrofitting air‐firing pulverized coal burners as oxy‐firing burners.     

Closed-loop phase behaviour in block copolymers

Closed-loop phase diagrams are known in systems with specific intermolecular interactions. In weakly interacting systems, however, such behaviour has never been observed. Here, diblock copolymers formed from polystyrene covalently linked to poly (n-pentylmethacrylate), P(S-b-nPMA), which have only weak segmental interactions, are shown to exhibit a closed-loop phase behaviour over a narrow range of molecular weight. The endothermic transitions from the disordered to ordered and back to the disordered state, as a function of increasing temperature, are dominantly entropic in origin. The morphology and rheological properties of P(S-b-nPMA) undergo characteristic changes at the transitions. Whereas the disorder-to-order transition temperature increases with decreasing molecular weight, the order-to-disorder transition temperature decreases. At a limiting molecular weight, the closed-loop vanishes and no ordering occurs. These findings provide quantitative insight into an elusive transition in weakly interacting multicomponent systems.     

Advanced photospacers with elastic recovery

A new series of photospacers has been prepared with different types of crosslinkers to improve elastic recovery. Afunctional crosslinker with six reactive groups demonstrates the best elastic recovery. As the quantity of crosslinker is increased, the elastic recovery also increases, probably due to an increase in the crosslinking density. The use of ADMS EPS® results in high resolution, good uniformity, and high production yield in the liquid‐crystal‐display (LCD) process. Especially, EPS® improves and solves problems such as viewing angle, crosstalk, and dark spots.     

Two-dimensional photonic crystal semiconductor lasers: computational design, fabrication, and characterization

We have designed, fabricated, and tested two-dimensional (2-D) slab photonic crystal semiconductor lasers at communication wavelengths. Wavelength-size microresonators defined on the 2-D slab photonic crystal have been effective in photon confinement and functioned well as ultra-small lasers by optical pumping. The photonic crystal laser structures that we have tested have shown large quality factors and low thresholds.     

Sb-Se-based phase-change memory device with lower power and higher speed operations

A phase-change material of Sb/sub 65/Se/sub 35/ was newly proposed for the nonvolatile memory applications. The fabricated phase-change memory device using Sb/sub 65/Se/sub 35/ showed a good electrical threshold switching characteristic in the dc current-voltage (I-V) measurement. The programming time for set operation of the memory device decreased from 1 /spl mu/s to 250 ns when Sb/sub 65/Se/sub 35/ was introduced in place of the conventionally employed Ge/sub 2/Sb/sub 2/Te/sub 5/ (GST). The reset current of Sb/sub 65/Se/sub 35/ device also dramatically reduced from 15 mA to 1.6 mA, compared with that of GST device. These results are attributed to the low melting temperature and high crystallization speed of Sb/sub 65/Se/sub 35/ and will contribute to lower power and higher speed operations of a phase-change nonvolatile memory.