Advanced Materials Research Vol. 815

Abstract: AgSnO₂ contact materials have begun to replace toxic AgCdO materials in switching devices such as contactors and circuit breakers since 1970s [1,, which is partly due to the fact that AgSnO₂ materials have shown higher service lives, better welding resistance and less arc erosion in contactors of larger size [. Furthermore, the growing awareness of environmental problems makes it desirable to replace AgCdO contact materials [. However, these materials suffer from an inadequate welding behavior compared with AgCdO [. It was observed that AgSnO₂ made by traditional metallurgical process exhibited high overtemperatures attributed to high contact resistance caused by surface layers of accumulated SnO₂, which was due to the poor wettability of SnO₂ grains in the silver melt in combination with their high thermal stability [6,7]. Another important point was the large size and high hardness of SnO₂ particle prepared by traditional process, which reduced the workability of AgSnO₂ contact materials [8]. In this work, the authors prepared Ti⁴⁺-doped SnO₂ using sol-gel technique and investigated the microstructure, size, distribution and crystallization of Ti⁴⁺-doped tin oxide grains as well as the doping effects on the electrical conductivity of these materials.

Abstract: The microstructure and impurities distribution in metallurgical grade silicon with treated by CaO-SiO₂ and Na₂O-SiO₂ slags were investigated. An exhaustive analysis of the transformation of precipitated phase at grain boundaries has been carried out. Prior to slag treatment, Si-Fe system intermetallic was the primary precipitated phase in metalllurgical grade silicon. After treated by CaO-SiO₂ slag, Si-Ca system intermetallic became the main precipitated phase, such as Si-Ca, Si-Ca-Ti, Si-Ca-Al and Si-Fe-Ca. But Na₂O-SiO₂ slag had another result on refining metallurgical grade silicon; only Si-Fe-Ti phase was generated in precipitated phase and the low level of sodium in treated silicon was obtained.

Abstract: In order to improve the power generation of microbial fuel cells (MFCs), carbon cloth anode was treated with ultrasonic or spent anolyte in this work. The maximum power density of a single-chamber air-cathode MFC was improved from 611.5 mW/m2 to 754.3 mW/m2 and 811.7 mW/m2, and the reactor start-up time was shortened by 7.3% and 22.7% respectively after treatments of the anode with ultrasonic and spent anolyte. Polarization tests reveal that the treated anodes have a smaller electrode polarization at high current densities than the control. MFCs with the treated anodes exhibited lower internal resistances than the untreated anode, which may arise from the enhanced substrate oxidation activity and extra-cellular electron transfer efficiency on these anodes. Results from this study indicated that treatment of anode with ultrasonic or spent anolyte was a simple and effective approach for improving the performance of MFCs.

Abstract: mproving the thermophysical properties of heat transfer fluid is always a research hotspot and difficult subject in the application of solar energy for medium and high temperature. The research and application of these heat transfer fluid, including steam, heat transfer oil, molten salt, air, liquid alloy and nanofluids, were summarized in this paper. After comparing their characteristics, it is found that molten salt, air and liquid alloy have greater application and development prospects. Future research directions include extending the temperature span of operating condition, enhancing the efficiency of heat transfer and storage, lengthening service life and finding out the correlation between microstructure and related performance.

Abstract: Stoichiometric Mg²⁺ and Ti⁴⁺ with different proportions were doped to prepare the LiFe_1-x-yMg_xTi_yPO₄ cathode materials by high temperature solid state method. The samples were investigated with XRD, SEM and charge/discharge measurements. Results show that doping of Mg²⁺ and Ti⁴⁺ distinctly changes the paticle sizes and morphologies, which leads to a improvement of electrochemical performance. The mix-doped LiFe_0.98Mg_0.01Ti_0.01PO₄ material shows the best electrochemical performance due to its smaller crystalline particles and lower the polarization. At the discharge rate of 0.1C, the initial specific capacity of LiFe_0.98Mg_0.01Ti_0.01PO₄ is 105.78 mAh·g^-1, its high-rate performance is also better.

Abstract: A polyacrylamide-grafted starch (St-g-AM-DMC-AMPS) flocculant for the coal slurry wastewater was prepared by using corn starch (St), acrylamide (AM), methyl acryloyloxyethy trimethyl ammonium chloride (DMC) as cationic monomer, 2-acrylamido-2-methyl acrylate sulfonic acid (AMPS) as anionic monomer through solution polymerization. The structure of the synthesized St-g-AM-DMC-AMPS was characterized by FT-IR and TG. The effects of initiator concentration, reaction temperature and monomer concentration on percentage of grafting and the grafting efficiency were investigated. The results showed that the optimal conditions of the polymerization are that the ratio of substrate and monomer is 3:7, the radio of ammonium persulfate is 0.15%, reaction time is 4h and reaction temperature is 50°C. The additional dosage of St-g-AM-DMC-AMPS is varying between 12mg/L and 20 mg/L to obtain better flocculation capability than PAM.

Abstract: An anionic polyacrylamide-grafted starch (St-g-APAM) flocculant for the coal slurry waste water, was prepared by using corn starch and acrylamide (AM) as monomers, acrylic acid (AA) as anionic monomer through solution polymerization. The effects of initiator concentration, reaction temperature, and monomer concentration on percentage of grafting and the grafting efficiency were investigated. The results show that the optimal conditions of the polymerization are as follows: the monomer to substrate ratio of 2.0, AM:AA ratio of 2:1, potassium persulfate of 0.7 x 10^-3 mol/L, reaction time of 4h, the reaction temperature of 50°C. The additional dosage of St-g-APAM is varying between 10 and 20 mg/L to obtain good flocculation capability.

Abstract: Titanosilicate ETS-4 with the Sr and Ni cations modification were prepared by hydrotherrmal method using titanium trichloride and tetraethoxysilane as raw materials. The properties and morphology of the materials were characterized by XRD, SEM techniques, Sr and Ni introduced to the molecular sieve affected the frame contraction when they were heated, and did little effect on the crystallization and morphology. N₂ and CH₄ isotherms of each sample were measured at room temperature. The Sr and Ni doping could improve the N₂ and CH₄ adsorption capacities of ETS-4. The capacities of the two gases increased in the pressurization process for ETS-4-Sr and ETS-4-Ni, with the pressure increasing, no significant change in capacities of N₂ and CH₄ was observed over the ETS-4 sample. Compared to ETS-4 molecular sieves, the capacity for N₂ of ETS-4-Sr and ETS-4-Ni at the pressure of 1200 mmHg increased 4.2 and 3.9 times, respectively. At last, the results indicated that the cations doping (Sr²⁺ and Ni²⁺) can improve the adsorption performance of ETS-4 greatly.

Abstract: A novel series of copolymers containing fluorene units are synthesized by Sonogashira coupling reaction in mild condition. Benzene, naphthalene and anthracene are co-polymerized with ethynylfluorene, respectively. The structures are confirmed by NMR, Mass, Elemental analysis and GPC. The polymers have good thermal properties with glass-transition temperature of 90-155°C(Tg), and they have bandgaps from 2.21-2.77 eV. The results of photoluminescence in solid state show that introduction of huge chromophore could effectively suppress the formation of aggregates and excimers which typically cause red-shifted or new emission.

Abstract: Cu (In_1-xGa_x)Se₂ (CIGS) polycrystalline thin films with Ga-gradient structures were prepared by selenization of sputtered Cu-In-Ga precursors. The Ga contents of the as-selenized CIGS thin films were measured by EDS. With greater Ga content, the peaks in the diffraction pattern become broadened. Auger electron spectroscopy was used to measure the composition distribution of the Cu, In, Ga, and Se elements in the CIGS and CuInSe₂ films. At 300°C, the diffusion coefficients D_Se was approximately (6.7±1.0) x 10^-16 m²s^-1, and D_Ga was about (4.5±1.0) x 10^-18 m²s^-1. D_Se are two orders of magnitude greater than D_Ga, which is also the reason why the selected CIGS film was almost completely selenized, but still able to keep certain Ga-grading profile. The temperature used in this work is within the low temperature range of the two-step selenization approach, which is more suitable for low-cost substrates like flexible substrates.