Since discovered in 1911, the superconductors have evolved from single element, alloy to complex compounds with multiple elements.So far the proved highest superconducting transition temperature is 164 K (under pressure). In the long time of investigation on superconductivity, the understanding on the superconducting mechanism has been promoted significantly. The BCS theory which was greatly successful in describing the conventional superconductivity now is challenged by the new phenomena in some unconventional superconductors.Therefore the investigation of high temperature superconductivity mechanism is also at the dawn of major breakthrough. In this short overview, we will give a survey on the three families of high temperature superconductors, namely cuprates, iron based superconductors. Based on the experience accumulated in past decades, we propose some ideas in exploring high temperature superconductors.

The influence of flaky nickel powder as pigment on the permeation resistance of fluorocarbon based coatings was investigated by salt spray tests, EIS tests and measurement of water vapor transmission rate. The results show that among others the coating with a volume fraction 5% of flaky nickel powder exhibited the best comprehensive performance, however its resistance to water permeation degraded greatly for the coating with higher volume fraction of flaky nickel powder up to 15%.

As phase change heat storage material (PCM), composites of paraffin/expanded graphite of different particle sizes (DPS-EG) were prepared by melt blending method, which were then characterized by means of XRD, FT-IR, SEM, DSC and LFA. The effect of mass fraction of DPS-EG on performance of the composite PCM was studied. Results show that the thermal diffusivity of the composite PCM increased first and then decreased with the increasing mass fraction of small particle sized EG. When the ratio of mass fraction for large sized ones to the small ones of the DPS-EG was 9:1, paraffin may be allowed to fill fully into the free space of the mosaic structure of DPS-EG. The thermal diffusivity of the composite PCM was up to 1.964×10^-6 m²/s, 22 times higher than that of pure paraffin, while its latent heat was 144.2 J/g.

Fe-C-Mo-M steels (where M is Nb, V or Ti, ~0.1%, and Mo ≤0.2% ) were produced by thermal mechanical control processing (TMCP), and then their performance was characterized in terms of failure temperature by means of constant load tensile test while heating from ambient temperature up to 800^oC with a heating rate 28 ^oC/min. The boundary misorientation of the steels after TMCP was examined by electron back scattered diffraction (EBSD), and the precipitates of MC type carbides were characterized by transmission electron microscopy (TEM). The results show that the addition of 0.2% Mo in Fe-C-Nab/V steels increases the failure temperature of steels by 40℃. It is believed that the low-angle grain boundary provided the favorable nucleation site for MC type carbides, which in turn will accelerate the kinetics of precipitation process. The fine and dispersed precipitates of MC type carbides induce significant precipitation strengthening for the steels during the constant load tensile process, thus resulting in higher failure temperature. Among the tested steels, the failure temperature of Ti-Mo steel is the highest due to its highest low-angle grain boundary density which results in the fast precipitation of MC type carbides. The failure temperature of Nb-Mo steel comes the second and that of the V-Mo steels is the lowest because of its lowest low angle grain boundary density leading to the lowest density of precipitated MC type carbides.

The semi-solid ZCuSn10 alloy billets were prepared with strain induced melt activated (SIMA) method involved with hot rolling and reheating process. The microstructure evolution process and spheroidizing mechanism of α(Cu) phase were studied by means of optical microscope, scanning electron microscope and image analysis software. The results show that when a hot rolled ZCuSn10 copper alloy billet with a deformation rate 16% was reheated at 930℃, of which the semi-solid primary phase spheroidized gradually with the increasing holding time; while the average grain size of the copper alloy decreases firstly with time from 68.24 μm for 8 min to 62.31 μm for 10 min and then increases to 71.09 μm for 25 min; the liquid fraction increases from 18.14% for 8 min to 25.32% for 25 min; the shape factor decreases firstly with time from 2.91 for 8 min to 1.67 for 15 min and then increases to 2.43 for 25 min. The alloy exhibits the best semi-solid microstructure for 15 min holding with an average grain size 65.64 μm, a liquid fraction 23.66% and a shape factor 1.67. The microstructure evolution mechanism involves with merge of grains and growth as well as atom diffusion leading to grain growth and spheroidization.

Crystallization behavior and soft magnetic properties of amorphous alloys Fe_x(SiB)_96-xP₃Cu₁ (x=75, 78, 80, 83 and 85, atomic fraction, %) were investigated. It was found that the apparent activation energy for crystallization decreased with the increasing Fe content of the Fe_x(SiB)_96-xP₃Cu₁ alloys. The phases precipitated after properly complete crystallization treatment were the same for all the alloys with varying Fe content. The annealed Fe_x(SiB)_96-xP₃Cu₁ (x=80, 83 and 85) alloys exhibited a uniform nanostructure with grain size smaller than 20 nm, while the grain sizes of the alloys with x=75 and 78 ranged from 5 nm to 50 nm. The saturation magnetization enhanced nonlinearly as the Fe content increased from 75 to 85. The nanocrystalline alloy Fe₈₅Si₃B₈P₃Cu₁ exhibited excellent soft magnetic properties with a coercivity of 12 Am^-1 and a saturation magnetization of 1.87 T. The core loss values of nanocrystalline alloys Fe₈₅Si₃B₈P₃Cu₁ and Fe₈₃Si₄B₉P₃Cu₁ were still less than 1.0 Wkg^-1 even if the saturation magnetic induction intensity was up to 1.7 T, which were superior to that of the commercial Fe₇₈Si₉B₁₃ alloy and non-orientated silicon steel.

According to an orthogonal experimental design and neural network prediction models, a new kind of backfill cementitious materials of unclassified tailings-rod milling sands is prepared with unclassified tailings partly replaced rod milling sands as aggregates, iron slag powder as the active materials as well as desulphurized ash and quicklime as the main stimulator. Hydration products and microstructures of the backfill cementitious materials are analyzed by XRD and SEM. The results show that with addition of 30% unclassified tailings, the compressive strength of the backfill cementitious materials cured for 3 days, 7 days and 28 days reaches 1.73 MPa, 4.22 MPa and 6.93 MPa, and the corresponding increment is 8.13%, 51.8% and 34.0% respectively in comparison with the ordinary cement, and these strength values can meet the backfill strength index of Jinchuan Nickel mine. The hydration products of the new backfill cementitious materials are mainly C-S-H gel and flocculent CSH gel, which form dense gel and bond the aggregates together resulting in the high mechanical strength of the materials. Therefore, utilization of 30% unclassified tailings can be achieved for the nickel mine company through producing this new backfill cementitious materials.

The intergranular corrosion characteristics of 316LN austenitic stainless steel welded joints with different welding heat input in boiling nitric acid solution were investigated by metallography analysis and acoustic emission technology. The results show that the resistance to intergranular corrosion of welded joints deteriorated with the increasing welding heat input. The intergranular corrosion resistance of the weld zone is better than that of the heat affected zone and the base material. Five stages for the intergranular corrosion process can be differentiated according to the characteristics of the detected acoustic emission spectrum, such as oxidation, passivation, oxide film crack initiation, oxide film crack propagation and finally fast intergranular corrosion. In other words, in the acoustic emission spectrum, there exist an obvious energy peak by 20 kHz representing the oxidation signal; an obvious energy peak by 40 kHz of a burst-like signal representing the stage of passivation process; energy peaks in a range 80 to 100 kHz of burst-like signal representing the oxide film crack initiation; energy peaks by frequency of 60 kHz representing the stage of crack propagation; and finally a peak by 50 kHz of a burst-like signal with a slightly longer duration representing the stage of fast intergranular corrosion.

Luminescent phosphors GdVO₄: Eu³⁺ was prepared in solutions with different pH values by hydrothermal synthesis route using Gd₂O₃, NH₄VO₃ and Eu₂O₃ as precursors, and cetyl trimethyl ammonium bromide (CTAB) as surfactant. The synthesized products were characterized in terms of morphology, structure and luminescent performance by means of XRD, SEM, TEM, and PL. The results show that in an acid solution with pH=1, the size of synthesized GdVO₄: Eu³⁺ crystal grains is of micron scale; in a solution with pH=4 , their size shrinks to nano-scale; it turned out well-dispersed nano-flakes of about 50 nm in solution with pH=7; besides, in solution with pH=10, a certain amount of impurity Gd(OH)₃ was detected by XRD for the synthesized GdVO₄: Eu³⁺ crystal grains. On the other hand, the surfactant affected obviously the final morphology of the synthesized GdVO₄: Eu³⁺ crystal grains in terms of changes in the crystal growth direction and the aggregation shape, correspondingly, the luminescent properties were affected by grain size and crystallinity. It turned out that square GdVO₄: Eu³⁺ nano-crystals with well crystallinity represented the optimal emission performance. But it is noted that the aggregation effect may weaken the luminescent property of the products.

Powders of ceria-zirconia solid solution were prepared by using different molar ratio of Ce(NO₃)₄6H₂O and Zr(NO₃)₄5H₂O as raw materials and appropriate additives of C₃H₅NO, C₇H₁₀N₂O₂ and (NH₄)₂S₂O₈ as polymer -net gel. The influence of the polymer-net gel on the preparation process and the effect of Ce/Zr ratio on the properties of the powders of ceria-zirconia solid solution were investigated respectively. The results show that the additives of polymer are beneficial not only to the separation of the particulates of ceria-zirconia solid solution due to the formation of a three-dimensional network of the polymer-net gel, but also to the formation of nanoporous powders of ceria-zirconia solid solution due to the burn away of polymer during the subsequent calcinations. The powders of ceria-zirconia solid solution with particle size 10-20 nm could be prepared when the mass ratio of C₃H₅NO and C₇H₁₀N₂O₂ was 5: 1, the dissolvability of mixed solute was 0.04 mol/L and an appropriate heat treatment process was adopted. XRD analysis revealed that the ceria-zirconia solid solutions with molar ratio of Ce/Zr in a range of 3: 7-5: 5 present tetragonal crystallographic structure, while those in a range of 6: 4-7: 3 present cubic structure respectively; their lattice constant decreased with the increasing Zr⁺ content. N₂ adsorption isotherm showed that the ceria-zirconia solid solution with Ce/Zr molar ratio of 6: 4 exhibited excellent features: specific surface area of 120 m²g^-1; aperture of 8.12 nm; pore volume of 0.22 cm³/g. SEM images showed that the ceria-zirconia solid solution powders have an alveolate-like network structure.