Modelling of organizational and technological parameters of the informational model of municipal infrastructure facilities subject to reorganization

This article describes constructing methods of an information reorganization facility model based on parametric mathematical methods. The principles of reorganization parameter selection at the stage of municipal infrastructure facility pre-operation are described. The algorithm of information model building of facilities reorganization, as well as information model of organization processes of reorganization are being shown

Modelling of organizational and technological parameters of the informational model of municipal infrastructure facilities subject to reorganization

This article describes constructing methods of an information reorganization facility model based on parametric mathematical methods. The principles of reorganization parameter selection at the stage of municipal infrastructure facility pre-operation are described. The algorithm of information model building of facilities reorganization, as well as information model of organization processes of reorganization are being shown

Tempering Behavior of a Si-Rich Low-Alloy Medium-Carbon Steel

Owing to the addition of Si, 0.33C-1.8Si-1.44Mn-0.58Cr steel exhibits a unique tempering behavior. The tempering takes place in two distinct sequential stages that are significantly different from those in steels containing 0.2–0.5 wt.% of Si. Stage I is associated with the precipitation of transition carbides in a paraequilibrium manner, can take place in temperatures ranging from ~200 to ~474 °C, and concurrently increases strength, ductility, and toughness. Stage II is associated with the decomposition of retained austenite to bainitic ferrite and transition carbides. As a result, no significant effect of overlapping of Stage I with Stage II takes place. Stage III does not occur at temperatures below ~474 °C, since the precipitation of cementite in a orthoequilibrium manner is suppressed by the addition of 1.8 wt.% of Si. It was shown that a major portion of carbon atoms redistributes to Cottrell atmospheres under quenching. During low-temperature tempering at 200–400 °C, the precipitation of transition carbides consumes a large portion of carbon atoms, thereby increasing the number of ductile fractures and improving the impact toughness without strength degradation. The formation of chains of cementite particles on boundaries takes place in Stage IV at a tempering temperature of 500 °C. This process results in the full depletion of excess carbon from a ferritic matrix that provides increased ductility and toughness but decreased strength

Effect of Alloying on the Nucleation and Growth of Laves Phase in the 9–10%Cr-3%Co Martensitic Steels during Creep

Five Co-modified P92-type steels with different contents of Cr, W, Mo, B, N, and Re have been examined to evaluate the effect of the chemical composition on the evolution of Laves phase during creep at 650 °C. The creep tests have been carried out at 650 °C under various applied initial stresses ranging from 80 to 200 MPa until rupture. An increase in the B and Cr contents leads to a decrease in the size and volume fraction of M23C6 carbides precipitated during tempering and an increase in their number particle density along the boundaries. In turns, this affects the amount of the nucleation sites for Laves phase during creep. The (W+Mo) content determines the diffusion growth and coarsening of Laves phase during creep. Susceptibility of Laves phase to coarsening with a high rate is caused by the large difference in Gibbs energy between fine and large particles located at the low-angle and high-angle boundaries, respectively, and can cause the creep strength breakdown. The addition of Re to the 10%Cr steel with low N and high B contents provides the slowest coarsening of Laves phase among the steels studied

Direct Vapor-Phase Bromination of Multiwall Carbon Nanotubes

We present the simple procedure of the vapor-phase bromination of multiwall carbon nanotubes (MWNTs) at moderate temperatures. MWNTs with average diameter 9±3 nm were treated with Br2 vapors at 250°C to produce Br-functionalized product. Transmission electron microscopy analysis was used to prove low damage of MWNT walls during bromination. X-ray photoelectron spectroscopy (XPS) and differential thermal analysis (DTA) were used to investigate chemical composition of the surface of initial and brominated nanotubes. The experimental results show that the structure of MWNTs is not affected by the bromination process and the total amount of Br-containing surface functions reaches 2.5 wt. %. Electrophysical properties of initial and brominated MWNTs were investigated showing decrease of conductivity for functionalized sample. Possible mechanism of the vapor-phase bromination via surface defects and oxygen-containing functional groups was proposed according to data obtained. Additional experiments with bromination of annealed low-defected MWNTs were performed giving Br content a low as 0.75 wt. % proving this hypothesis