Development of grain boundary allotriomorphic ferrite/granular bainite duplex steel

A new hot-rolled low alloy high strength steel with grain boundary allotriomorphic ferrite/granular bainite duplex micro-structure has been developed through novel microstructure and alloying designs without any noble metal elements such as nickel and molybdenum. Its as-rolled microstructure and mechanical properties, fatigue crack propagation behavior compared with single granular bainitic steel as well as continuous cooling transformation, were investigated in detail. The measured result of CCT (continuous cooling transformation) curve shows that such duplex microstructure can be easily obtained within a wide air-cooling rate range. More importantly, this duplex microstructure has much better combination of toughness and strength than the single granular bainite microstructure. It is found that the grain boundary allotriomorphic ferrite in this duplex microstructure can blunt the mi-crocrack tip, cause fatigue crack propagation route branching and curving, and thus it increases the resistance to fatigue crack propa-gation, improves steel toughness. The mechanical properties of the above commercial duplex steel plates have achieved or exceeded 870 MPa ultimate tensile strength, 570 MPa yield strength, 18% elongation and 34 J Charpy V-notch impact energy at -40℃,showing good development potential.     

High temperature oxidation behavior of high speed steel for hot rolls material

The oxidation characteristics of high speed steel (HSS) were studied at 500 to 800°C. The non-isothermal oxidation and isothermal oxidation (500, 575, 650, 725, 800°C) of HSS were investigated by thermo-gravimetric analysis (TGA). The microstructure, morphology and oxide scale thickness of the isothermal oxidation samples were analyzed by optical microscope (OM), electron probe micro analyzer (EPMA), X-ray diffraction spectrum (XRD) and scanning electron microscope (SEM). The results indicate that the oxidation rate of HSS is very slow at 500 to 650°C, increasing gradually at 650 to 750°C, and drastically at 750 to 800°C, because the phase transformation happens at about 750°C.     

Measurement and AFPS control of molten steel level in strip casting

The measurement and control of the molten steel level are studied, which affect the quality of strip surface in strip casting.A system of molten steel measurement with a CCD (Charge Coupled Devices) sensor is designed, real-time measured data are given and its precision is analyzed. The level fluctuation model is derived, and an adaptive fuzzy-PID controller with supervisory control (AFPS) is proposed. The stability of the system is proved using Lyapunov theorem, and the simulation results are given when the model, the casting speed and the roll gap change. It is suggested that this kind of coupled nonlinear and time varying system is stable and robust using the designed AFPS controller.     

Effects of Different Ceilings in a Burning Compartment on Smoke Hazard with Single Heat Action Analysis Added

One quarter scale experiment device of a typical L - shape architecture structure including a burning room and an adjacent hallway is established to carry out the research. The smoke characteristics at the sampling points below the ceiling of the burning compartment and the roof of the hallway are studied systematically to find out the effects of different ceilings on the local fire origin compartment and the smoke transportation to a remote area. A series of tests is reported and the smoke residence time, the concentration peak and the concentration build up rate are investigated as functions of the type of the ceiling. The smoke residence time, the most important factor concerning smoke toxicity, is described by a novel concept, wavelength, in this study. Furthermore, it is worth emphasizing that the PVC ceiling exhibits a phenomenon of frequent collapse during the fire developing period. The single heat action is conducted to judge the smoke and the heat effect on the fire risk.     

Performances of super-long span prestressed cable-stayed bridge with CFRP cables and RPC girder

To discuss the applicability of advanced composite carbon fiber reinforced polymer (CFRP) and ultra-high performance concrete reactive powder concrete (RPC) in super-long span cable-stayed bridges , ta...     

Novelionic Polymer Electrolytes for Dye Sensitized Solar Cell

In recent years, dye-sensitized solar cells（DSC） based on nanocrystalline porous TiO2 films have attracted much attention because of their relatively higher efficiency and low cost compared with conventional inorganic photovoltaic devices. This type of solar cell has achieved an impressive photo-to-energy conversion efficiency of over 10% where the electrolyte is volatile organic liquid solvents containing I^-/I3^- as redox couple. Because of high volatilities, solvent losses occur during long-term operations, resulting in lowered DSC performances. And leakage of liquid electrolyte also limits the durability of DSC.     

Lithium-ion full cell with high energy density using nickel-rich LiNi0.8Co0.1Mn0.1O2 cathode and SiO-C composite anode

A high-energy-density Li-ion battery with excellent rate capability and long cycle life was fabricated with a Ni-rich layered LiNi_0.8Mn_0.1Co_0.1O₂ cathode and SiO-C composite anode. The LiNi_0.8Mn_0.1Co_0.1O₂ and SiO-C exhibited excellent electrochemical performance in both half and full cells. Specifically, when integrated into a full cell configuration, a high energy density (280 Wh·kg-1) with excellent rate capability and long cycle life was attained. At 0.5C, the full cell retained 80% of its initial capacity after 200 charge/discharge cycles, and 60% after 600 cycles, indicating robust structural tolerance for the repeated insertion/extraction of Li+ ions. The rate performance showed that, at high rate of 1C and 2C, 96.8% and 93% of the initial capacity were retained, respectively. The results demonstrate strong potential for the development of high energy density Li-ion batteries for practical applications.     

Thermoelectric properties of I-doped n-type Bi2Te3-based material prepared by hydrothermal and subsequent hot pressing

I-doped Bi_2Te_(3-x)I_x(x=0, 0.05, 0.1, 0.2) flower-like nanoparticles were synthesized by a hydrothermal method through a careful adjustment of the amount of ethylenediamine tetraacetic acid surfactant. The nanopowders of flower-like nanoparticles were hot-pressed into bulk pellets and the thermoelectric properties of the pellets were investigated. The results showed that I-doping decreased the electrical resistivity effectively, and the thermal conductivitives of the Bi_2Te_(3-x)I_x bulk samples was lower because of the closer atomic mass of I compared to Te.As a result, a ZT value of 1.1 was attained at 448 K for the Bi_2Te_(2.9)I_(0.1)sample.