This paper is an attempt to study the fire performance of concrete filled steel tube reinforced concrete (CFSTRC) columns exposed to fire condition. Tests were carried out on CFSTRC columns subjected to ISO-834 standard fire. Details of temperature distribution, fire resistance, deformations and failure mechanism are presented in the paper. Based on the observation and analysis of test results, the characteristics of CFSTRC columns subjected to a fire were investigated. It was found that the concrete outside CFST can act as a natural insulation to the steel tube and the inner concrete; there was no local buckling in steel tube due to the presence of concrete both outside and inside steel tube; the concrete inside steel tube kept intact in the test. These characteristics make CFSTRC columns obtain a favorable fire performance. A three-dimensional finite element analysis (FEA) model was developed to calculate the temperature field of CFSTRC columns. Based on theoretic analysis, the influences of important parameters on the temperature field of the composite columns were investigated. The studies in the paper will be a foundation for further theoretical analysis on the mechanic performance of CFSTRC columns exposed to fire.

Dry tribological tests of M50 matrix composites containing 0, 2.5, 5.0, and 7.5 wt% Ag are undertaken at 0.2 m/second 15 N from 25°C to 450°C against Si3N4 ceramic balls. The results indicate that the tribological performance is strongly dependent on the content of solid lubricant Ag. M50 matrix composites containing 5.0 wt% Ag exhibits the great tribological performance with the low friction coefficients of 0.23 to 0.43 and less wear rates of 1.89 to 3.52 × 10−6 mm3 N−1 m−1 from 25°C to 450°C, which is attributed to the formation of thick lubricating film on the worn surface. Furthermore, the migration model of solid lubricant Ag in M50 matrix composites is established to predict the thickness of formed lubricating film.

Oxidation of nanometer metallic particles has been an obstacle that hinders the application of these materials in magnetic fluids. In this paper, the synthesis of magnetic fluids containing carbon-coated iron nanoparticles have been investigated. The carbon-coated iron nanoparticles have been produced by a W-arc discharge method. The uncapsulated particles and carbonaceous debris have been removed from the product by acid treatment and magnetic separation. The morphology, size distribution and phase composition of the particles have been characterized by TEM and XRD. The results show that the size of the particles is about 10 nm, the core of the particles is iron, and the shell of the particles is onion shaped carbon layers. The mineral oil based magnetic fluids containing carbon-coated iron nanoparticles was synthesized by using complex surfactants (T151 and OAE) to form double surfactant layers on the particle surface. The magnetic fluids with highest magnetization was obtained when the amount of surfactants is 160% of that of carbon-coated particles in weight. The magnetic properties of the encapsulated particles and magnetic fluids were investigated by VSM, their magnetization curves show a lack of hysteresis, characteristic of superparamagnetic material. The saturation magnetization of carbon-coated iron particles is 113.9emu/g, and the saturation magnetization of magnetic fluids containing carbon-coated iron particles (35%wt.) is 32emu/g.

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