Key Engineering Materials Vol. 617

Abstract: Aiming to develop sponge-type sorbent, composite involving ammonium molybdophosphate (AMP) and polyurethane foam (PUF) was prepared. A 33 - 60 % (w/w) of AMP granule was kneaded with base-liquids of two-component rigid type PUF. The composite was able to selectively and quantitatively adsorb 0.5-500 µL of Cs⁺ from 10 mL solution of 500 µL of Na⁺, K⁺, Mg²⁺ and Ca²⁺ as matrices ions; distribution coefficient (k_d) was 4.2 × 10⁶ and 1.3 × 10⁵ mL/g for without and with matrices, respectively. Maximum sorption capacity was of 42.9 mg/g.

Abstract: The effect of the surface conditions of (001) and (100) rutile TiO₂ surfaces on the photocatalytic decomposition of linoleic acid was investigated. The rate of decomposition was observed by measuring the weight of the remaining linoleic acid. The as-received (polished) (001) surface showed a higher photocatalytic activity than the (100) surface, but the activity was greatly reduced when the surface was treated by HF solution and heated to 400°C. Condition of the surface strongly affects the photocatalytic activity. The heated (001) surface partially regained its activity after multiple parallel grooves were introduced along the [110] direction. However, the surface did not regain its activity if these grooves were instead introduced along the [1-10] or [100] directions.

Abstract: The manufacture of foam glass from recycled material is a way that fits with the global objective of environmental protection and the optimal use of household glass waste. The energy savings, achieved through the use of cullet, result in a significant reduction in air pollution, especially carbon dioxide (CO₂) emission, and reduce the cost of the production process. Moreover, the foam glass, as an insulation active material, will help to reduce the residential energy consumption for heating and/or air conditioning. As this porous material is produced by gas bubbles formation (decomposition of carbonates) within a melt glass, the purpose of this study is to identify the temperature range of foaming gas evolution and its influence on the material properties. This analysis was performed by coupled DTA (differential thermal analysis) & TGA (thermogravimetric analysis). Thermal analysis was performed according to the same procedure as for the sample preparation temperature i.e. a final temperature of 850 °C with a heating rate of 6.5 °C/min. Morphology and physical properties have been measured and the high thermal properties of the resulting product make it a suitable candidate for the fabrication of insulating panels for construction industry.

Abstract: Fukushima nuclear power plant was destroyed by tsunami of the Great East Japan earthquake, and radioactive cesium was widely scattered from there. Further, highly concentrated radioactive cesium was found in the bottom of the sea sludge of Tokyo Bay, where the cesium concentration is 1.513 times as high as usual. However, the decontamination method of the bottom of the sea sludge is not yet established. Therefore, the authors proposed to decontaminate cesium from the sea sludge under an anaerobic condition, referenced from a previous study. Sludge and cesium nitrate were mixed with a wet weight ratio of 0.3 wt% for cesium nitrate to form a model mixture, and immersed in 6 dm³ of deionized water and kept for 10 days. As a result, the author found terms that is able to decrease amount of cesium in the sludge. However we found this term was not anaerobic condition from after research, finally found difficult to decreased cesium in the sludge without aerobic condition.

Abstract: Aiming to apply in removal of selenium from contaminated waste water, we have studied the immobilization of Se (IV) and Se (VI) into the hydrate of calcium alumino-zincate (14CaO.5Al₂O₃.6ZnO, shown as C₁₄A₅Z₆). By adding 2 g of C₁₄A₅Z₆ to 1 L of 5 mg/L Se (VI) solution, the concentration of Se (VI) was decreased to less than 0.01 mg/L within 60 minutes. In the case of using 1 g of calcium hydroxide with 2 g of C₁₄A₅Z₆, the Se (VI) concentration reached to 0.01 mg/L within 30 minutes. On the other hand, the concentration of Se (IV) was decreased from 5 mg/L to 0.16 mg/L in 60 minutes whilst it reached to 0.041 mg/L by adding calcium hydroxide in the same reaction period. The immobilization capacity of selenium were 222 and 127 mg/g for Se (IV) and Se (VI), respectively. By adding calcium hydroxide, the immobilization capacity of C₁₄A₅Z₆ was increased to 240 and 200 mg/g for Se (IV) and Se (VI), respectively.

Abstract: M-TiO₂ (M = Ag, Cu) nanocomposite layers were grown by pulsed direct liquid injection chemical vapor deposition (DLICVD) on various substrates to produce bactericidal surfaces with long term activity. Monodisperse Ag nanoparticles (NPs) with an average size of 5-10 nm are embedded in an anatase matrix. A bactericidal behavior determined by the JIS Z 2801 standard test was found for Ag-TiO₂ films for Ag ≤ 1 at. % and above. Higher Ag content is not necessary since efficiency is already at its maximum (relative activity 100%). By contrast, using Cu as antibacterial agent, a larger size distribution of metal particles was found (20 to 400 nm). Cu-TiO₂ films exhibit a bactericidal behavior if their thickness is higher than 100 nm and Cu content ≥ 3.5 at. %. These coatings are still antibacterial after 5 months of aging and their efficiency has decreased by only 35%.

Abstract: The longest afterglow time of an orange-red- emitting SrS:Eu²⁺,Pr³⁺ afterglow phosphor by visible light irradiation was about 1010 minutes was previously achieved by varying the synthetic conditions such as amount of Li⁺ added, reduction temperature, reduction time, and initial Eu/Sr and Pr/Sr atomic ratios in previous paper. Therefore, this study reports on the effect of the RE³⁺ codopants on the afterglow time of an orange-red-emitting SrS phosphor by visible light irradiation. SrSO₄:Eu³⁺,RE³⁺(RE³⁺ = Tm³⁺, Er³⁺, Tb³⁺, Nd³⁺, Pr³⁺, Ce³⁺, and La³⁺), which was the precursor for SrS phosphors, was synthesized via a liquid-phase reaction. SrSO4:Eu³⁺,RE³⁺ was pressurized at 10 MPa for a few minutes to form a compact, which was then heated under a H₂S or Ar-H₂ (5 mol%) reductive atmosphere at 1400 °C for 2.5 h to generate the SrS:Eu³⁺,RE³⁺ afterglow phosphor. The emission color of the SrS:Eu²⁺,RE³⁺ afterglow phosphor was orange-red and its emission peak was observed around 610 nm. The excited band of the phosphor was in the range of visible light more than 440 nm. The emission and excitation spectra of the SrS:Eu²⁺,RE³⁺ afterglow phosphor were not dependent on the RE³⁺ codopants. However, the afterglow time of SrS:Eu²⁺,RE³⁺ phosphor was increased with the increase of ionic radius of the coactivator. The longest afterglow time of SrS:Eu²⁺,Ce³⁺ phosphor by irradiating for 5 minutes at 1000 lx which was created from a D₆₅ lamp was 1376 minutes. This was 9.5 times longer than that of a commercial available phosphor (CaS:Eu²⁺,Tm³⁺).

Abstract: We report here on resistive switching measurements on GaMo₄S₈ a lacunar spinel compound with tetrahedral Mo₄ clusters filled with 11 electrons. Alike other clustered lacunar spinel compounds with 7 or 8 electrons per cluster, this narrow gap Mott Insulator exhibits both a volatile and a non-volatile unipolar resistive switching. We found that the volatile resistive switching appears above a threshold electric field in the 7 kV/cm range. For electric field much larger than this threshold, the resistive switching becomes non-volatile. Successive electric pulses allow switching back and forth between high and low resistance states. All these results demonstrate that the narrow gap Mott insulator compound GaMo₄S₈ could be a relevant candidate for a new type of non-volatile memory based on an electric field induced breakdown of the Mott insulating state.

Abstract: A family of TeO₂-based glasses is known to have high third-order nonlinear properties and expected as nonlinear optical devices. In the present study, we fabricated Ag₂O-TeO₂ and Ag₂O-Nb₂O₅-TeO₂ glasses, and estimated their structures and linear/nonlinear optical properties. The main results showed that the absorption-edge of the glasses was shifted to longer wavelength side with increasing Ag₂O content. By Raman spectroscopy, it was found that an increase in Ag₂O content promoted to change TeO₄ to TeO₃/TeO₃₊₁ units. X-ray photoelectron spectroscopy (XPS) revealed the presence of an electronic state of Ag²⁺ ions, which was supposed to have a large influence on the absorption-edge wavelength. In Ag₂O-Nb₂O₅-TeO₂ glass system, the third-order nonlinear susceptibility χ⁽³⁾ increased with increasing Ag₂O content at the expense of Nb₂O₅ content.

Abstract: The effects of various fluoride fluxes on the crystallization of blue phosphor BaMgAl₁₀O₁₇:Eu²⁺ were characterized using a wide panel of experimental methods. LiF appeared as the most efficient, with a significant increase of the photoluminescence yield under excitation at 280 nm. Besides, the recrystallization resulted in a redistribution of the dopant among the three crystallographic sites, leading to a strong increase of the excitation in the near-UV domain. This allowed the emission to increase by 40 % under a 400 nm irradiation, typically of interest for possible LED-blue phosphor systems. At last, the shaping into hexagonal single crystals allowed both a reduction of the thermal degradation under air, and the discovery of a novel regeneration process at moderate temperature.