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In this work, microporous MgO refractory aggregates with nano-sized pores were prepared by in situ decomposition method using Mg(OH)2 as raw material. The effects of firing temperatures (1600–1700°C) and compacting pressures (100–200 MPa) on the microstructures and properties of microporous MgO refractory aggregates were thoroughly studied. The results showed that the microporous MgO refractory aggregates contained two types of pore structures, which were intra-particle pores with pore sizes of 180.0–230.0 nm formed by in situ decomposition of Mg(OH)2 and inter-particle pores with pore sizes of 1.5–3.0 μm derived from particle packing between Mg(OH)2 pseudomorph particles, respectively. Besides, the firing temperatures had a great influence on the intra-particle pore size and microcrystallite size. And the compacting pressures not only influenced the intra-particle pore size via packing behaviors but also affected the inner firing behaviors of the pseudomorph particles due to the increase in H2O vapor pressure. Overall, at a compacting pressure of 150 MPa and firing temperature of 1650°C, the sample had the best comprehensive performance with a bulk density of 1.92 g/cm3, a compressive strength of 11.9 MPa, an apparent porosity of 45.0%, a relative aggregate tube strength of 25.2% and a median pore size of 262.3 nm. [ABSTRACT FROM AUTHOR]

A bimetallic composite roll with the cladding layer of high-speed steel (HSS) and the roll core of ductile cast iron (DCI) was manufactured by the electroslag remelting cladding (ESRC) technology, and the changes in the graphite morphology, matrix structure, and mechanical properties of the DCI core before and after the ESRC process were compared. The DCI core was first heated to a very high temperature and then cooled down to room temperature during ESRC which led to a deteriorative graphite morphology with a low spheroidisation rate, a large size, and a nonuniform distribution and also caused a solid-state phase transformation of the matrix structure from lamellar pearlite + few carbides to bainite + large amounts of carbides. Based on the changes of graphite sphericity, matrix structure, carbides content, the tensile strength and impact toughness of DCI before and after the ESRC process changed from 458 MPa, 3.02 J/cm2 to 417 MPa, 5.74 J/cm2, respectively. [ABSTRACT FROM AUTHOR]

The decarburisation annealing processes of Nb-bearing grain-oriented silicon steel under different conditions were conducted. The effect of nitriding and decarburisation annealing time on the carbon content, precipitates, microstructure and texture of Nb-bearing grain-oriented silicon steel were investigated by the various analysis methods. The results show that the carbon content in the steel decreases as decarburisation time increasing, and decreases below 0.003% eventually. Larger number density and smaller size of precipitates were obtained in the sample treated by nitriding before decarburisation annealing process, leading to fine and uniform microstructure, which is beneficial to obtain excellent magnetic properties for Nb-bearing grain-oriented silicon steel. The main texture types of the experimental samples were γ-fibres with a peak at {111}<112 >. The nitriding before decarburisation annealing process makes little effect on texture evolution during decarburisation annealing process. [ABSTRACT FROM AUTHOR]

The surface oxidation weight gains on 7.8 wt% Cr-containing stainless steel at different temperatures were studied by thermogravimetric analysis and scanning electron microscope (SEM) equipped with energy-dispersive spectroscopy (EDS). The results show that there are two layers of oxide scales covering the surface of steel matrix after 100 min high-temperature oxidation. The inner oxide scale consists of (Fe, Cr) oxide and the outer oxide scale is composed of Fe oxide due to the stronger affinity of Cr with O. The growth of outer oxide scale is dominated by the combined effects of chemical reaction rate and mass transfer. Based on the study of the oxidation kinetics at different temperatures, a prediction model for surface oxidation weight gain on 7.8 wt% Cr-containing stainless steel electrode during electroslag remelting is acquired, providing a reference for the determination of the amount of deoxidiser added into the molten slag during electrode remelting. [ABSTRACT FROM AUTHOR]

The description of line-line topological relations is still an unsolved issue although much effort has been done. The problem is involved in many practical applications such as spatial query, spatial analysis and cartographic generalization. To develop a sound and effective approach to describe line-line relations, it is first necessary to define the topology of an individual line, i.e., local topology. The concept of connective degree is used for the identification of topological differences in the geometric structure of a line. The general topological definition of a line is given, i.e., endpoints set and interior point set. This definition can be applied to the embedded spaces of different dimensions, whether co-dimension is equal to or larger than zero. On this basis, a generic model called the 4 intersection-and-difference is set up for the description of basic line-line topological relations, upon which a conceptual neighborhood graph is built with consideration of topological distance. It is concluded that the proposed model can represent the property of topological changes, and basic relations between line segments in IR 1 and IR 2. [ABSTRACT FROM AUTHOR]

Thermoelectric generation (TEG) is one of the most effective technologies converting heat directly into electric power. In this paper, a nearly kilowatt class TEG system mainly based on radiation heat transfer was designed and built. The open circuit voltage, the output power, the power density, and the conversion efficiency of the TEG system were investigated in detail at different temperature gradients. The maximum inverter power output of the TEG system assembled with 182 TEG devices can reach 684 W at a temperature difference around 125 K, and the corresponding power density can reach 845 W/m2. The inverter output power is almost proportional to the temperature difference between the hot and the cold side of TEG system. Our results confirmed that if the waste heat resource was sufficient to provide a greater temperature difference of 200 K in practical application, the output power and the power density of this TEG system would reach 1.23 kW and 1.51 kW/m2, respectively. [ABSTRACT FROM AUTHOR]