Search

Bearing capacity and durability of corroded steel bars is strongly deteriorated, and the degradation of mechanical properties versus corrosion ratio is topical. Given the random nature of corrosion process, stochastic method can be used to describe mechanical performance of corroded steel bars. In this paper, to simulate marine tidal zone environment, steel bars corroded by chloride solution under dry-wet cycling are studied experimentally, while mechanical performance deterioration of corroded steel bars is analyzed statistically. The corrosion ratios of specimens are found to increase over time for several phases, while their strength dropped with corrosion ratio. The residual nominal strength to corrosion ratio of steel bars is found to be well fitted with the Gumbel distribution, which parameters are calculated and discussed in detail.

The growth defects in solution grown L-arginine phosphate monohydrate (LAP) organic crystals were investigated by white-beam synchrotron radiation topography. The crystals were cut into slices in different directions. The transmission topographies showed the dislocations, growth striations, growth sector boundaries and inclusions in both (100) slice and (001) slice with different reflection. We also presented the contrast of microbe, which is a severe problem in LAP crystal growth. The topography with 015 reflection showed the dislocations originated from the surface of the seed and following the (00 1) and (100) direction, and the Burgers vectors of those dislocations were determined. The dynamic images of growth sector boundaries were also showed clearly.

The hyperbranched polymers can be made by self-condensing vinyl polymerization without gelation transition. The average molecular weights, as well as the average sizes, can reach infinite values as the reaction is quantitatively completed, and the scaling forms of the molecular parameters should exist. In the paper, based on a recursion formula, the scaling form of the number fraction distribution and the number of the n-mers are given analytically as the conversion of double bonds is near 1. The mean square radius of gyration for very large hyperbranched polymers is calculated explicitly to give a scaling exponent. Finally, a scaling relation associated with the fractal dimension and the polydispersity exponent is given clearly.

An investigation of twin structures in NdP5O14 single crystals has been undertaken using white‐beam synchrotron x‐ray topography. The so‐called a‐type twins along the a axis are clearly revealed in the topographs. The displacements of the images that arise from the twins are directly measured in different topographs. With the measured values, the monoclinic distortion angle δ(δ=β−90°) is calculated, which is in good agreement with the unit cell parameters. A fine‐beam Laue diffraction pattern of the twin has also been taken which is well consistent with its simulation. From these results, the twin structures of NdP5O14 are discussed.

Ultra‐fast high‐temperature microwave annealing at temperatures as high as 2050 °C for 30 s has been performed on phosphorus ion‐implanted 4H‐SiC for phosphorus doping concentrations in the range 5×1019 cm−3–8×1020 cm−3. For comparison, inductive heating furnace anneals were performed at 1800 °C–1950 °C for 5 min. Electrical resistivity of the P+‐implanted samples decreased with increasing annealing temperature reaching a minimum value of 6.8×10−4 Ωcm for 2050 °C/30 s microwave annealing and a slightly higher value for 1950 °C/5 min inductive heating furnace annealing. X‐ray rocking curve measurements showed that the microwave annealing not only removed the lattice damage introduced by the ion‐implantation process, but also the defects present in the original virgin sample as well.

Potential applications of SiC include components for advanced turbine engines, tube assemblies for radiant burners and petrochemical processing and heat exchangers for high efficiency electric power generation systems. Reliable methods for joining SiC are required in order to cost-effectively fabricate components for these applications from commercially available shapes and sizes. This manuscript reports the results of microwave joining experiments performed using two different types of SiC materials. The first were on reaction bonded SiC, and produced joints with fracture toughness equal to or greater than that of the base material over an extended range of joining temperatures. The second were on continuous fiber-reinforced SiC/SiC composite materials, which were successfully joined with a commercial active brazing alloy, as well as by using a polymer precursor.

Microwave rapid thermal annealing has been utilized to remove the lattice damage caused by nitrogen (N) ion-implantation as well as to activate the dopant in 6H-SiC. Samples were annealed at temperatures as high as 1400 °C, for 10 min. Van der Pauw Hall measurements indicate an implant activation of 36%, which is similar to the value obtained for the conventional furnace annealing at 1600 °C. Good lattice quality restoration was observed in the Rutherford backscattering and photoluminescence spectra.

Microwave sintering of zirconia toughened mullite (ZTM) has been performed in a single mode applicator. In comparison with conventional sintering, microwave processing of ZTM leads to a higher density and finer grain size. Microstructure of microwave sintered ZTM was characterized by TEM and HRTEM techniques. The pinning of intergranular ZrO2 dispersoids retarded the grain growth of mullite matrix. The observation of a considerable number of trans-granular microcracks indicates that microcracking toughening is the main toughening mechanism for ZTM.