•The role of FeO-containing slag in coal gasification reaction was investigated.•The addition of slag enhanced the coal gasification reaction.•Higher FeO content slag increased CO generation rate and decreased CO amount.•Higher CO2 gas ratio and reaction temperature promoted the gasification of coal.•Low-rank coal was more sensitive to catalyst loadings and produced less CO.In this study, steelmaking slag was utilized as heat carrier and catalyst to perform the coal gasification; meanwhile, CO2 was used as gasifying agent rather than steam from the viewpoint of carbon circulation. An overview on research activities and technology development on the effect of steelmaking slag on coal gasification are provided. The effects of coal type, slag composition, CO2 gas ratio and temperature on the gas producing behavior were discussed through the high temperature experiment. The results showed that coal gasification was remarkably enhanced and the produced CO amount increased considerably with the addition of slag. On the contrary, with the increase of the slag amount, the produced CO amount has the decreasing trend. Coal combined with higher FeO content slag presented higher CO generation rate and less CO generation amount. Moreover, the increase of the CO2 gas ratio and reaction temperature would promote the gasification of coal.

The effects of Bi addition on the properties of Sn-3.0Ag-0.5Cu molten alloy on Cu substrates are discussed using wettability and interface microstructure analysis. The changes of the contact angles between Sn-3.0Ag-0.5Cu-xBi and Cu substrates with the spreading time are described by Dezellus model. It indicates that the spreading process is governed by the interfacial reaction during the dwelling time. The interface microstructure is observed to clarify the effects of reactions on the spreading behavior. It is found that Cu6Sn5 is formed adjacent to the solder and Cu3Sn appears over the substrate with Bi added at 613K, indicating that Bi exists between the intermetallics and the addition of Bi can hinder the diffusion of copper towards the interior of the solder. Therefore the existence of Bi decreases the agglomeration of Cu-Sn grains. The growth of intermetallics is thus limited and the shape of intermetallics transforms from scallop to zigzag consequently. However, the segregation phenomenon appears when the additive amount of Bi is more than 5.5mass %, which could lead to the occurrence of fracture and degrade the performance of Sn-3.0Ag-0.5Cu-xBi alloy. The results of the present study provide basic physical and chemical data for the application of lead-free solder in the future microgravity space environment.

•Sn–3.0Ag–0.5Cu wetting on the inclined Ni substrate is performed at high temperature.•Curve fitting for profiles of droplets are presented to calculate contact angles.•Contact angle hysteresis with different inclinations of the substrate is discussed.•Moving characteristics of the front and rear triple points are investigated.•Surface Evolver is employed to simulate spreading behavior of the molten solder.To investigate interface properties of molten Sn–3.0Ag–0.5Cu solder melting on the inclined Ni substrate at 540 K, wetting experiments are performed and the numerical simulation is carried out by Surface Evolver. Profile curves of the droplets are fitted with empirical equation, which are proposed to obtain preferable contact angles. The spreading behavior of the droplets is analyzed. It is indicated that the contact line hardly moves at the very beginning; the rear point of triple line moves forward along the substrate subsequently, but the front point of triple line is still pinned on the substrate. Correspondingly, the advancing contact angle gradually increases to the peak value, and then declines with the migration of the front point of triple line. The spreading process is simulated to demonstrate the contact angle hysteresis. Interface microstructure is observed to clarify the effect of reactions on the spreading behavior, and the distribution of intermetallic compounds including Ni3Sn4 and (Cu,Ni)6Sn5 are identified.

The reactive spreading processes of Sn–17Bi–0.5Cu melt alloy on Cu substrate were studied by sessile drop method in the temperature range of 523–673 K. Dynamic contact angles between the solder and Cu substrate at different times were recorded with high-resolution CCD digital video. The smallest contact angle was observed at 623 and 673 K. Ultimate spreading radius does not increase monotonously with the temperature increasing. These can be attributed to the strong dissolution of Cu substrate into the liquid solder, which hinders the solder from spreading. Triple line area configuration of the Sn–17Bi–0.5Cu/Cu system was discussed by the description of the equilibrium state. The calculated results based on experiments of the tension balances along each of the three interfaces show good agreement with theoretical analysis. Intermetallic compounds at the Sn–17Bi–0.5Cu/Cu interface are identified as Cu6Sn5 adjacent to the solder and Cu3Sn adjacent to the Cu substrate, respectively. These results are of practical interest for composite lead-free solders’ preparations and joining of Sn–17Bi–0.5Cu to Cu substrate.

Reactive wetting processes of molten Sn-3.5Ag on Cu substrates at elevated temperatures were investigated by the sessile drop method. Equilibrium contact angles of Sn-3.5Ag on Cu substrates are 36.5°, 32.9°, 25.25°, and 32.1° at 523 K, 573 K, 623 K, and 673 K, respectively, indicating that the contact angle does not decrease monotonically with increasing temperature. It is also found that the maximal triple-line mobility does not increase linearly with temperature. The complicated temperature effects on the equilibrium contact angles and triple-line mobility are attributable to the fact that Cu substrates dissolve easily in the liquid solder, hindering solder spreading. A description of the equilibrium state helped explain the triple-line region of the Sn-3.5Ag/Cu joint. The calculated results, based on the experimental values of tension balances along each of the three interfaces, show good agreement with the theoretical analysis. The present results are of practical interest for composite lead-free solder preparations and joining of Sn-3.5Ag to Cu substrates.

The reactive wetting kinetics of a Sn-30Bi-0.5Cu Pb-free solder alloy on a Cu substrate was investigated by the sessile drop method from 493 to 623 K. The triple line frontier, characterized by the drop base radius R was recorded dynamically with a high resolution CCD using different spreading processes in an Ar-H2 flow. We found a good agreement with the De Gennes model for the relationship between ln(dR/dt) and lnR for the spreading processes at 493 and 523 K. However, a significant deviation from the De Gennes model was found for the spreading processes at 548 and 623 K. Our experimental results show a complicated temperature effect on the spreading kinetics. Intermetallics at the Sn-30Bi-0.5Cu/Cu interface were identified as Cu6Sn5 adjacent to the solder and Cu3Sn adjacent to the Cu substrate. The intermetallic compounds effectively enhanced the triple line mobility because of reaction product formation at the diffusion frontier.