Magnetic And Photocatalytic Properties Of Sulphide, Phosphide And Nitride Prepared By Controlling Vapor Pressure

It is usually difficult to control the high temperature reactions thatcontaining substances with high volatility, such as sulphur，phosphorus, arsenic andselenium. The preparation of these materials is generally carried out by sealing theprecursors in the quartz tube. The preparation of iron-based superconductors withelemental phosphorus and arsenic is an example. It should be noted that the strengthof the quartz tube is limited，and thus a tube would become broken if the gas pressureinside is high enough at elevated temperatures. For example，the vapor pressure ofsulphur will reach one atmospheric pressure at444°C and with increasing thetemperature the vapor pressure will elevate quickly. In comparasion with that ofsulphur，the phosphorus vapor pressure elevates much more quickly at the sameconditions. In this paper，we report on an apparatus that can balance the gas pressureinside and outside the quartz tube during the high temperature reactions. The gaspressure is adjustable below100MPa by using a gas booster and a regulating system.We prepared Fe/FeS nanoparticle magnetic catalysts with core-shell structure byusing the above heated-treatment apparatus，and studied the morphology，magneticand photocatalytic properties. The sample is effective in degradation of MB in thevisible-light region with a degradation of38%. The Fe/FeS catalysts can be recycledby a magnet and reused for its magnetic core and photocatalytic shell. Meanwhile wealso investigated the exchange bias effect of the Fe/FeS system at low temperatures.We prepared MnP by using one step process with the above high gas pressureheated-treatment apparatus and studied its magnetocaloric effect. The maximummagnetic entropy change of the as-synthesized MnP is0.95Jkg-1K-1at roomtemperature under the magnetic field of1.5T. We synthesized N-doped Mn-P-Ncompound and studied its structure，chemical composition and magnetocaloric effect.The maximum magnetic entropy change of Mn-P-N compound was0.70Jkg-1K-1under1.5T with a small magnetic lag.By using the above apparatus，we studied the synthesis，structure and magneticproperties of Mn-O system in the high gas pressure of nitrogen and oxygen. It wasfound that the high nitrogen pressure can promote the reaction at low temperaturesand increase the concentration of N in the lattice. The magnetic measurments showthat the coercivity and the exchange bias field of the sample are1.12T and0.38T at2K，respectively. The high oxygen pressure is benefit to the oxidation reaction with more phases.Nitrogen doped TiO2-xfilms have been prepared by using N-ion implantationmethod and formed a2.73atm%concentration of N atoms in the N-doped films. Thephotocatalytic properties of the N-doped films under visible light have beeninvestigated by degradation of methylene blue solution.