[en] Mixed ferrite MnFe₂O₄ has been prepared by combustion synthesis method and subsequent heat treatment. The effects of annealing temperature and quenching conditions on phase compositions of the samples have been investigated by X-ray diffraction and Moessbauer spectroscopy. The results show that the combustion of Fe₂O₃, MnO₂ and Fe results in a series of mixtures of new phases, which convert to MnFe₂O₄ single spinel phase during subsequent heat treatment at 1200 deg. C for 2 h and rapid quenching. Moreover, combustion synthesis of MnFe₂O₄ can efficiently induce a redistribution of divalent and trivalent ions in the A and B sites

[en] The influence of the oxygen pressure on the phase composition, microstructural evolution of the combustion products during the combustion synthesis of zinc ferrite through iron, iron oxide, and zinc oxide powders was discussed. The results show that with the increase of oxygen pressure, combustion temperature and combustion wave velocity increase. Single spinel-phase zinc ferrite can be obtained when the oxygen pressure is 1.0 MPa and a non-stoichiometric composition, Fe_1-xO or Fe_1-zO is formed when the oxygen pressure is below 1.0 MPa or above 1.5 MPa. Moreover, an analysis of the dependence of the degree of conversion to ferrite, η, on the oxygen pressure has also been made. For a given porosity and combustion temperature, the degree of conversion increases with the oxygen pressure increasing and for any given porosity and degree of conversion, higher pressure is required at higher temperature

[en] Nano-sized Sr_0.5Ba_0.5Nb₂O₆ (SBN50) ceramic powders have been synthesized by an aqueous organic gel route. Homogeneous Sr-Ba-Nb precursor gels are prepared with Ba-EDTA, Sr-EDTA, and Nb-citrate complex as source of Sr, Ba, and Nb, respectively. Citric acid and ethylenediaminetetraacetic acid (EDTA) were used as the chelating agents. The structural variation of the SBN powder with annealing temperature was studied by TG-DTA, FT-IR and XRD. The precursor gel on calcination at 800 deg. C for 2 h produces a pure tungsten bronze SBN phase and the corresponding average particle size is 30-50 nm. The influences of the pH and the molar ratio of citric acid:Nb cation on the formation of homogeneous Sr-Ba-Nb precursor gels were also studied. The results show that a homogeneous Sr-Ba-Nb precursor gel with no precipitate is formed at pH 8 and the optimum molar ratio of citric acid and the metal cations is 3:1

[en] Uniformly distributed polycrystalline indium nanohillocks are synthesized on silicon substrates with Au catalyst by using the radio frequency magnetic sputtering technique. The results show that the Au catalyst plays a key role in the formation of indium nanohillocks. After thermally oxidizing the indium nanohillocks at 500 °C in air for 5 h, the indium nanohillocks totally transform into In₂O₃ nanohillocks. The energy-dispersive X-ray spectroscopy result indicates that many oxygen vacancies and oxygen—indium vacancy pairs exist in the In₂O₃ nanohillocks. Photoluminescence spectra under an Ne laser excitation at 280 nm show broad emissions at 420 nm and 470 nm with a shoulder at 450 nm related to oxygen vacancies and oxygen—indium vacancies at room temperature. (interdisciplinary physics and related areas of science and technology)

No abstract available

[en] Graphene oxide (GO) and reduced graphene oxide (RGO) materials contain a variety of surface O-functional groups that are chemically reactive. When released into the environment these materials may significantly affect the abiotic transformation of organic contaminants, and therefore, may alter their fate and risks. We found that two GO and five RGO materials that varied in C/O ratio, hydrophobicity, and type/distribution of surface O-functionality all had catalytic effects on the dehydrochlorination of 1,1,2,2-tetrachloroethane (TeCA). Even though the catalytic effects of the materials originated from their deprotonated surface O-functional groups, which served as conjugated bases to catalyze the reaction, the catalytic efficiencies of the materials did not correlate strongly with their surface O contents. The spectroscopic evidence (X-ray photoelectron spectroscopy and Fourier transform infrared spectroscopy), surface charge data, and adsorption experiments demonstrated that the catalytic efficiencies of the GO/RGO materials were controlled by a complex interplay of the type and distribution of surface O-functionality, as well as adsorption affinity of the materials. Both Ca²⁺ and Mg²⁺ inhibited the catalytic efficiency of the materials by binding to the surface O-functional groups, and consequently, decreasing the basicity of the functional groups. At an environmentally relevant concentration of 10 mg/L, Suwannee River humic acid (used as a model dissolved organic matter) alone had little effect on the dehydrochlorination of TeCA. However, it could inhibit the catalytic efficiency of the GO/RGO materials by coating on their surface and thus, decreasing the adsorption affinity of these materials for TeCA. The findings further underline the potentially important impacts of nanomaterials on contaminant fate and effects in the environment. - Highlights: • Graphene-based materials catalyze hydrolysis of 1,1,2,2-tetrachloroethane. • Catalytic effects originate from deprotonated surface O-functional groups. • Adsorption affinity of a material plays important role in catalytic efficiency. • Catalytic effects of nanomaterials may significantly affect contaminant fate. - Graphene oxide and reduced graphene oxide materials significantly catalyze dehydrochlorination of 1,1,2,2-tetrachloroethane.

[en] AP 1000 designed by Westinghouse Electric Company has become one of the leaders in the third generation nuclear power plant. More and more researches concentrate on the AP 1000 safety assessment considering the important status of Aaap in China. This paper aims to build the main system model of Aaap plant and study its behavior in case of a loss-of-coolant accident (LOCA) based on the simulation code RELAP5. The model in a steady state makes it possible to perform the desired transient analysis. In the present study, the response of AP 1000 primary circuit to a SB-LOCA in the non-pressurizer side is simulated. Difference between 10-in. cold leg break and 10-in. hot leg break is investigated. The result shows that a hot leg SB-LOCA has the similar effect to a cold leg SB-LOCA but the accident result of the former is less serious. The results of a spectrum of hot leg breaks show that the diminution of RCS pressure is much slower for a smaller break, which leads to different transient behaviors. From the simulation result, transient operating features for AP 1000 under a hot-leg SB-LOCA situation can be concluded. The research data can be beneficial to the prevention and management of a similar accident. (authors)

[en] In this paper, the Gd-AZ91 alloy was manufactured by adding rare earth element Gd in AZ91 magnesium alloy. The effects of solution treatment on the microstructures of rare earth elements Gd were investigated by means of optical microscopy, scanning electron microscopy, X-ray diffraction analysis and equipment for testing mechanical properties. The experimental results show that the addition of rare earth element Gd in AZ91 magnesium alloy can refine the alloy grain, turn β-Mg17Al12 phase into a discontinuous network or point structure, and produce granular compound Al2Gd in the alloy; when solution temperature is about 380 °C, the alloy structure is the best, the tensile strength of the alloy is the largest with the value larger than 250Mpa; when the solution temperature exceeds 380 °C, the alloy structure is coarsened and the mechanical properties of the alloy are reduced. With the increase of rare earth element Gd content, the tensile strength of the alloy shows a tendency to increase gradually, which Indicates that the addition of a certain amount of rare earth elements Gd can improve the plasticity of the alloy. (paper)

[en] In this paper, requirements for safe shutdown by chemical control are analyzed in the rod stuck accident of small modular reactor. Through theoretical calculation of the volume and time needed for boric acid injection process during different operating conditions, the influence of different factors such as the number of stuck rods or concentration and flux of boric acid are compared.The results show that chemical shutdown capability meets the relevant demands, which offers suggestions for the optimization of the system and reference of safety analysis. (authors)

[en] The Fluoride-Salt-Cooled High-Temperature Reactor (FHR) is a molten salt cooled, graphite moderated high temperature reactor. In this work, single-batch cycle length, block power distributions, and temperature-related reactivity effects were assessed using the SCALE code suite. Two types of parametric studies were performed. The first consisted of fixed temperature (isothermal) cases in which to determine the relationship between operation power and cycle length as well as pin power distributions. This second study calculates various isothermal reactivity coefficients based on heterogeneous temperature distributions. Reactivity coefficients with respect to the temperature of the fuel, coolant, and moderator were performed separately to determine their individual contributions. (authors)