Nanocrystalline ferrite formation by ball milling in pure Fe (0.004 mass% C) has been studied through morphology observation and microhardness measurements. It was found that nano-ferrite first formed at the outer surface area in the powders at the early stage of ball milling, which was attributed to the deformation localization. The boundaries between the nano-ferrite and work-hardened regions are quite clear under SEM and the hardness of nano-ferrite region is more than 3 GPa higher than that of the work-hardened region. Further milling led to the particle refinement and formation of nano-ferrite of the whole particles. It has been suggested that the nanocrystalline ferrite formed through a transition from dislocation cell wall created by work hardening during ball milling to grain boundary, which is regarded to contribute to the hardness gap between the work hardened structure and the nanocrystalline ferrite. A relatively high stability against temperature was observed in the nano-ferrite formed by ball milling. The irregular grain boundaries of nano-ferrite annealed at high temperature was attributed to that the grain growth of nanocrystalline ferrite takes place by coalescence of neighboring grains.KEY WORDS: nanocrystalline ferrite; pure Fe; ball milling; heavy deformation; structure.and a length of several mm were cut from iron block and subjected to ball milling. Ball milling was performed in a conventional horizontal ball mill under the protection of pure Ar atmosphere up to 1 800 ks. A vial with inner diameter of 128 mm, a rotation speed of 95Ϯ1 rpm and a ball to powder weight ratio of 100 : 1 were applied. Structural characterization was performed in scanning electron microscopic (SEM) and transition electron microscopic (TEM) observations. SEM observations were carried out on a JEOL JSM-6 300 microscope after polishing and etching the samples in 3% Nital. TEM was performed on a Hitachi H-800 working at 200 kV. Microhardness measurement was carried out using a MVK-G1 Vicker's hardness tester with an applied load of 1.96 N for 10 s. ResultsThe microstructure evolution of pure Fe with ball milling was observed by SEM. It was found that heavy deformation taking place during ball milling led to the formation of two types of structure in all the specimens with intermediate milling times (see Fig. 1). One is a uniformly layered structure near the outer surface area of the particles, which is difficult to be etched by Nital (the bright area near or on the surface). The other is a conventionally deformed structure in the interior of the particles (the interior darker area). Generally, the boundaries between these two types of structures are quite clear under SEM observation. It was also observed that the amount of the layered structure increased with increasing milling time. Among the powders with certain milling time, the finer the particles are, the larger the fraction of layered structure. Figure 2 shows the microstructure change with ball milling time. The starting microstructure of pure Fe is ferrite wit...

Aromatic iodinated disinfection byproducts (DBPs) are a newly identified category of highly toxic DBPs. Among the identified aromatic iodinated DBPs, 2,4,6-triiodophenol and 2,6-diiodo-4-nitrophenol have shown relatively widespread occurrence and high toxicity. In this study, we found that 4-iodophenol underwent transformation to form 2,4,6-triiodophenol and 2,6-diiodo-4-nitrophenol in the presence of monochloramine. The transformation pathways were investigated, the decomposition kinetics of 4-iodophenol and the formation of 2,4,6-triiodophenol and 2,6-diiodo-4-nitrophenol were studied, the factors affecting the transformation were examined, the toxicity change during the transformation was evaluated, and the occurrence of the proposed transformation pathways during chloramination of source water was verified. The results revealed that 2,4,6-triiodophenol and 2,6-diiodo-4-nitrophenol, which could account for 71.0% of iodine in the transformed 4-iodophenol, were important iodinated transformation products of 4-iodophenol in the presence of monochloramine. The transformation pathways of 4-iodophenol in the presence of monochloramine were proposed and verified. The decomposition of 4-iodophenol in the presence of monochloramine followed a pseudo-second-order decay. Various factors including monochloramine dose, pH, temperature, nitrite concentration, and free chlorine contact time (before chloramination) affected the transformation. The cytotoxicity of the chloraminated 4-iodophenol samples increased continuously with contact time. The proposed transformation pathways occurred during chloramination of source water.

Antibiotics have been widely used for disease prevention and treatment of the human and animals, and for growth promotion in animal husbandry. Antibiotics can disturb the intestinal microbial community, which play a fundamental role in animals' health. Misuse or overuse of antibiotics can result in increase and spread of microbial antibiotic resistance, threatening human health and ecological safety. In this study, we used Illumina Hiseq sequencing, (1)H nuclear magnetic resonance spectroscopy and metagenomics approaches to investigate intestinal microbial community shift and antibiotic resistance alteration of the mice drinking the water containing tetracycline hydrochloride (TET). Two-week TET administration caused reduction of gut microbial diversity (from 194 to 89 genera), increase in Firmicutes abundance (from 24.9 to 39.8%) and decrease in Bacteroidetes abundance (from 69.8 to 51.2%). Metagenomic analysis showed that TET treatment affected the intestinal microbial functions of carbohydrate, ribosomal, cell wall/membrane/envelope and signal transduction, which is evidenced by the alteration in the metabolites of mouse serum. Meanwhile, in the mouse intestinal microbiota, TET treatment enhanced the abundance of antibiotic resistance genes (ARGs) (from 307.3 to 1492.7 ppm), plasmids (from 425.4 to 3235.1 ppm) and integrons (from 0.8 to 179.6 ppm) in mouse gut. Our results indicated that TET administration can disturb gut microbial community and physiological metabolism of mice, and increase the opportunity of ARGs and mobile genetic elements entering into the environment with feces discharge.