• Journal of the Microelectronics and Packaging Society
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• v.22 no.3
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• pp.45-50
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• 2015

The goal of this research is the create novel magnets with no rare-earth contents, with larger energy product by comparison with currently used ferrites. For this purpose we developed nano-sized hard-type/soft-type composite ferrite in which high remanent magnetization (Mr) and high coercivity (Hc). Nano-sized Ba-ferrite, Ni-Zn ferrite and $BaFe_{12}O_{19}/Ni_{0.5}Zn_{0.5}Fe_2O_4$ composite ferrites were prepared by sol-gel combustion method by use of glicine-nitrate and citric acid. Nanocomposite ferrites were calcined at temperature range $700-900^{\circ}C$ for 1h. According to the X-ray diffraction patterns and FT-IR spectra, single phase of NiZn-ferrite and Ba-ferrite were detected and hard/soft nanocomposite ferrite was indicated to the coexistence of the magnetoplumbite-structural $BaFe_{12}O_{19}$ and spinel-structural $Ni_{0.5}Zn_{0.5}Fe_2O_4$ that agreed with the standard JCPDS 10-0325 data. The particle size of nanocomposite turn out to be less than 120 nm. The nanocomposite ferrite shows a single-phase magnetization behavior, implying that the hard magnetic phase and soft magnetic phase were well exchange-coupled. The specific saturation magnetization ($M_s$) of the nanocomposite ferrite is located between hard ($BaFe_{12}O_{19}$) and soft ferrite($Ni_{0.5}Zn_{0.5}Fe_2O_4$). The remanence (Mr) of nanocomposite ferrite is much higher than that of the individual $BaFe_{12}O_{19}$ and $Ni_{0.5}Zn_{0.5}Fe_2O_4$ ferrite, and $(BH)_{max}$ is increased slightly.

• Advances in concrete construction
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• v.10 no.5
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• pp.403-416
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• 2020

This study investigated the effect of alkaline activators - NaOH_aq (NH) (NH: 0-16 M) and Na₂SiO_3aq (NS) (NS/NH: 0-3.5) in the synthesis of silico-manganese fume (SMF) and ground blast furnace slag (BFS) blended alkali-activated mortar (AASB). The use of individual activator was ineffective in producing AASB of sufficient fresh and hardened properties, compared to the synergy of both activators. This may be attributed to incomplete dissolution and condensation of oligomers required for gelation of the binder. An inverse relationship was noted among the fresh properties and the NH concentration or NS/NH ratio. This was influenced by the dissolution and condensation of silicate monomers under polymerization process. The maximum 28-day strength of ~45 MPa, setting time of 60 min and flow of 182 mm was obtained with the use of combined activators (10M-NH and NS/NH=2.5). The combined activators at NS/10M-NH=2.5 constituted SiO₂/Na₂O, H₂O/Na₂O and H₂O/SiO₂ molar ratio of 1.61, 17.33 and 10.77, respectively. This facilitated the formation of C-S-H, C/K-A-S-H and C-Mn-S-H in the framework together with an increase in the crystallinity due to more silicate re-organization within the aluminosilicate chain. On comparison of the high concentrated with mild alkali synthesized product, it revealed that the concentration of OH^- and Si monomers together with alkali metals influenced the dissolution of precursors and embedment of the constituent elements in the polymeric matrix. These factors eventually contributed to the microstructural densification of the mortar prepared with NS/10M-NH=2.5 thereby enhancing the compressive strength.

• Journal of Food Hygiene and Safety
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• v.32 no.2
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• pp.114-122
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• 2017

N-nitrosamines can be produced in the process of heating, processing, storage and packaging. Migration specifications for N-nitrosamines exist only for rubber baby bottle nipples, which are regulated by the Ministry of Food and Drug Safety (MFDS). There is no regulation for other food contact substances (FCS) and studies on N-nitrosamines migration from FCS are rather limited. A pilot study showed an increase in N-nitrosamines contents when cooking instant noodles. Thus, the migration from the packaging was suspected and it was necessary to monitor the migration of N-nitrosamines from food packaging materials and to examine the change in N-nitrosamines contents when cooking instant foods. Three N-nitrosamines, NDMA (N-nitrosodimethtlamine), NDEA (N-nitrosodiethylamine), NDBA (N-nitrosodibutylamine), were analyzed in migration test solutions from plastics such as polyethylene, polypropylene and polystyrene, papers and aluminium containers. In all test solutions, N-nitrosamines were detected less than method quantitation limits (MQLs). Food samples were also investigated to ensure that there is no effect from food contact substances when cooking instant foods. In retort sauces such as curry, black soybean sauce and tomato sauce, NDMA concentration was ranged from 0.54 to $3.81{\mu}g/kg$, but there were no significant differences between unheated and heated samples. However, the NDMA contents were significantly increased in most of the instant noodle samples tested when cooked (p < 0.05). No effects from the food contact substances or cooking water was observed. Only when the seasoning powder and noodles were cooked together was NDMA detected. Individual components (noodle, seasoning powder or dried vegetable) or other combinations such as noodles and dried vegetables did not generate N-nitrosamines. Therefore, it is speculated that NDMA may be formed from the precursors in noodles and seasoning powders when they are solubilized in a medium of water.