Crystal Growth, Characterization, and Properties of Nonlinear Optical Crystals of LixAg1-xGaSe2 for Mid-Infrared Applications.

LixAg1-xGaSe2 is a new series of solid solution crystals that has a large nonlinear optical (NLO) coefficient and laser-induced damage threshold (LIDT). It has great application prospects in mid-infrared laser frequency conversion. In this work, LixAg1-xGaSe2 (x = 0, 0.2, 0.4, 0.5, 0.6, 0.8, and 1) crystals (Φ 16 mm × 40 mm) were grown by the improved Bridgeman method in a four-zone furnace. It is found that the LixAg1-xGaSe2 (x = 0.2-0.8) crystals keep the same tetragonal symmetry with AgGaSe2 and the melting and solidification temperature increase with the Li content. Because the as-grown crystals are almost opaque in the visible-NIR range, an annealing experiment is necessary. After annealing, the transmittance is improved significantly, which can meet the application requirements. The band gap is changed by annealing atmosphere; for instance, the band gap of Li0.6Ag0.4GaSe2 annealed in a LiGaSe2 powder atmosphere increases from 2.35 to 2.56 eV, while the band gap of LiGaSe2 annealed in vacuum decreases from 3.39 to 3.01 eV. Finally, the LixAg1-xGaSe2 shows an extreme SHG response, especially Li0.8Ag0.2GaSe2, which has about five times that of LiGaSe2, proving the promising NLO properties.

Na-Ions Diffusion Impacts Supercapacitor Performance for Amaryllis-like NiCo2O4 Nanostructures.

NiCo2O4 nanomaterials with exceptional electrochemical performances are synthesized via a simple and low-cost method. The synthesized nanostructures exhibit a high specific surface area of 121.52 m2 g-1 and excellent specific capacitance of 2498.49 F g-1 at a current density of 2 A g-1, an energy density of 79 Wh kg-1, and power density of 3570 W kg-1. The remarkable cycling stability of 92.61% retention after 5000 cycles demonstrates that NiCo2O4 nanomaterials have a potential for practical application in energy storage devices. The Na+ ion diffusion (by VASP) affirms a low activation energy barrier for Na ion intercalations onto the electrode material, illuminating excellent electrochemical performances.

Rapid Immobilization of Simulated Radioactive Soil Waste Using Self-Propagating Synthesized Gd2Ti2O7 Pyrochlore Matrix.

A rapid and effective method is necessary in the disposal of severely radioactive contaminated soil waste. Simulated Ce-bearing radioactive soil waste was immobilized by self-propagating high-temperature synthesis (SHS) within 5 min in this study. The main work includes the rapid synthesis of soil waste forms, the analysis of phase composition, microstructure and chemical durability. These results show that the simulated nuclide Ce was successfully immobilized into the pyrochlore-rich waste matrice, whose main phases are SiO2, pyrochlore (Gd2Ti2O7) and Cu. The normalized leaching rates of Si and Na on the 42nd day are 1.86 × 10-3 and 1.63 × 10-2 g·m-2·d-1, respectively. And the normalized leaching rate of Ce also remains at low level (10-5-10-6 g·m-2·d-1) within 42 days.

Evaluation on the stabilization of Zn/Ni/Cu in spinel forms: Low-cost red mud as an effective precursor.

Red mud, which is from the aluminum industry, is a potentially under-utilized resource. Technological processes for using low-cost red mud as an alternative precursor for detoxifying metal pollutants urgently need to be developed. In this study, we systematically investigated the feasibility of using red mud to detoxify metal-containing wastes (e.g., fly ash) via the formation of preferable crystalline phases. To understand the mechanism of metal detoxification by red mud, CuO, NiO, and ZnO were blended with red mud at different weight ratios and the mixtures were then subjected to ceramic-sintering. After sintering, the X-ray diffraction results revealed that all of the metals (i.e., Cu, Ni, and Zn) were able to be crystallographically incorporated into spinel lattices. Sintering the red mud at 1100 °C for 3 h effectively converted the metals into spinels. The mixing weight ratios strongly affected the efficiency of the metal incorporation. The red mud was able to incorporate 15 wt% of metal oxides. The incorporation mechanisms mainly occurred between the metal oxide(s) and hematite. Modified TCLP tests were conducted to further evaluate the metal stabilization performance of the red mud, which demonstrated the leachabilities of ZnO and the sintered red mud + ZnO product. The concentration of leached metal was substantially reduced after the incorporation process, thus demonstrating that red mud can be successfully used to detoxify metals. The results of this study reveal that waste red mud can be feasibly reused as a promising waste-to-resource strategy for stabilizing heavy metal wastes.

Self-Propagating Synthesis and Characterization Studies of Gd-Bearing Hf-Zirconolite Ceramic Waste Forms.

Synroc is recognized as the second-generation waste matrice for nuclear waste disposal. Zirconolite is one of the most durable Synroc minerals. In this study, Gd and Hf were selected as the surrogates of trivalent and tetravalent actinide nuclides. Gd-bearing Hf-zirconolite (Ca1-xHf1-xGd2xTi2O7) ceramic waste forms were rapidly synthesized from a self-propagating technique using CuO as the oxidant. The results indicate that Gd can concurrently replace the Ca and Hf sites. However, Gd2O3 could not completely be incorporated into the lattice structure of zirconolite when the x value is higher than 0.8. The aqueous durability of selected Gd-Hf codoped sample (Hf-Gd-0.6) was tested, where the 42 days normalized leaching rates (LRi) of Ca, Cu, Gd and Hf are measured to be 1.57, 0.13, 4.72 × 10-7 and 1.59 × 10-8 g·m-2·d-1.

Heavy-ion irradiation effects on U3O8 incorporated Gd2Zr2O7 waste forms.

In this research, the heavy-ion irradiation effects of U-bearing Gd2Zr2O7 ceramics were explored for nuclear waste immobilization. U3O8 was designed to be incorporated into Gd2Zr2O7 from two different routes in the form of (Gd1-4xU2x)2(Zr1-xUx)2O7 (x = 0.1, 0.14). The self-irradiation of actinide nuclides was simulated by Xe20+ heavy-ion radiation under different fluences. Grazing incidence X-ray diffraction (GIXRD) analysis reveals the relationship between radiation dose, damage and depth. The radiation tolerance is promoted with the increment of U3O8 content in the discussed range. Raman spectroscopy testifies the enhancement of radiation tolerance and microscopically existed phase evolution from the chemical bond vibrations. In addition, the microstructure and elemental distribution of the irradiated samples were analyzed as well. The amorphization degree of the sample surface declines as the U content was elevated from x = 0.1 to x = 0.14.

One-pot sonochemical synthesis of magnetite@reduced graphene oxide nanocomposite for high performance Li ion storage.

In this research, we introduce a one-pot sonochemical method for the fabrication of magnetite@reduced graphene oxide (Fe3O4@rGO) nanocomposite as anode material for Li-ion batteries. Fe3O4@rGO is synthesized under ultrasonic irradiations by using iron (II) salt and GO as raw materials. An in-situ oxidation-reduction occurs between GO and Fe2+ during the ultrasonic chemical reaction process. Fe3O4 particles with the size of ∼20 nm are uniformly deposited on the surface of rGO nanosheets. The electrochemical activity of Fe3O4@rGO is systematically evaluated as an anode material in Li-ion battery. Li-ion cells using Fe3O4@rGO as electrode deliver high discharge and charge capacities of 1433.6 and 907.8 mAh g-1 in the initial cycle at 200 mA g-1. Even performed at 500 and 5000 mA g-1, it is able to deliver reversible capacities of 846.4 and 355.6 mAh g-1, respectively, demonstrating outstanding Li-ion storage performance. This research presents a straightforward and efficient method for the fabrication of Fe3O4@rGO, which holds great potential in synthesis of other metal oxides on graphene sheets.

Growth mechanism of one-step self-masking reactive-ion-etching (RIE) broadband antireflective and superhydrophilic structures induced by metal nanodots on fused silica.

This work presents a low-cost, simple, convenient, advanced technology to prepare large-area defect-free subwavelength structures (SWSs). SWSs were obtained by a metal-induced one-step self-masking RIE process on a fused-silica surface, in which metal-fluoride (mainly ferrous-fluoride) nanodots were used to induce and gather stable fluorocarbon polymer etching inhibitors in the RIE polymers as masks. The SWS growth processes are visible with an increase in etching time and some exhibit prominent broadband antireflective properties from the visible to the near-infrared wavelength range. Transmission in the 600-900-nm range increased from approximately 93% for the polished fused silica to above 99% for the double-side SWSs on fused silica. A theoretical simulation by a finite-difference time-domain method agreed well with the experiments. Moreover, the surface of the SWSs exhibits excellent superhydrophilic properties.

[The longitude study on the mental development of congenital hearing-impaired infants and toddlers].

OBJECTIVE: To explore the effect of chronological age and acoustic device in cognitive development of congenital hearing-impaired infants and toddlers, and analyze the correlation of abilities in cognitive development with other factors. METHODS: Depending on chronological age (1 year old group and 2 years old group) and acoustic device (hearing aids and cochlear implantation), locomotor, personal-social, hearing and speech, hand and eye co-ordination, performance tests in Griffith Cognitive Development Scale were used to assess the cognitive development of 80 hearing-impaired infants and toddlers aged 0-2 years, including before intervention (0 month), after intervention (6, 12 months). Datas were analyzed by Repeated Measurements and Pearson Correlation Test. RESULTS: During 1 year hearing intervention and rehabilitation, hearing and speech, performance and cognitive were extremely significant difference for each phase of early intervention (P < 0.01), the development of locomotor, personal-social, hand and eye co-ordination were no significant difference (P > 0.05). Personal-Social in 1 year old group with hearing impairment was much higher than 2 years old group P < 0.05). Hearing and speech in cochlear implanted group with hearing loss was much higher than hearing aids group. Cognitive development was positive correlation with various region development P < 0.01), and was negatively correlated with chronological age (P > 0.05). CONCLUSIONS: Cognitive development is proportional to recovery time. The chronological age of early intervention obviously affect deaf children's cognitive development. The ability of hearing and speech in cochlear implanted children is superior to children with hearing aids in severe and profound hearing impaired children.