Papers by Keyword: Nodule

Abstract: The microstructure and mechanical properties of the work roll grade acicular nodular cast iron supplied by two different manufacturers were studied and compared. These rolls have different chemical compositions, namely work roll A and work roll B, respectively. This work aims to evaluate the two different work rolls with different chemistry and the effect on the microstructure and hardness. The microstructure was observed by the optical microscope and image analyzer, and the hardness value was measured using a Rockwell hardness machine. The results showed that the work roll A presented more carbides and graphite nodules than B. Carbide area fraction and nodularity level of work roll A are found much higher than B; therefore, it provided a higher hardness. It seems a higher percentage of carbon and proper amount of magnesium as a nodulizer contributed to produce more carbides and nodules on the cast iron of work roll A compared to B.

Abstract: The application of new materials and three-dimensional structures are being used to achieve next-generation semiconductor devices. Hence, the role of the chemical-mechanical planarization (CMP) process has gained importance. Polyvinyl acetal (PVA) brushes are widely used as scrubbers during post-CMP cleaning. However, the mechanisms of brush scrubber cleaning are still a matter of debate because direct observation is difficult. Many researchers have proposed the removal mechanisms that operate during brush cleaning based on investigations of the forces acting on particles, friction, and the lubrication characteristics. Hydrodynamic drag forces and direct contact between the brush and the particles have been proposed as cleaning mechanisms [1–5]. Philipossian et al. [6] and Sun et al. [7] focused on the brush design and suggested that the existence of nodules or eccentricity of the roller brush had a significant effect on the friction. The friction system between the roller brush and the surface is complex because of the collision of nodules with the surface. Hence, the shapes of the nodules have been designed through trial and error. In this study, we focus on the friction of a single nodule to investigate the role of nodules in roller brush cleaning. The normal and friction forces are measured during brush sliding. In particular, we focus on the viscoelastic properties of a PVA brush and discuss its effects on friction.

Abstract: The oxidation kinetics of 2205 stainless steel in humid air at high temperature were studied by adopting thermal-gravimetric analysis (TGA). The morphology, composition and microstructure of the oxide scales were analyzed using SEM and XRD. The experiment showed that few scales form on the surface of DSS2205 at less than 800°C.With increasing temperature above 800°C, thickness of oxide scales increase and the inner oxides can be found. The nodules can be observed when the temperature reaches 1050°C.

Abstract: In this study, the aluminizing of high silicon cast iron by hot-dipping in pure Al melt was performed and their high temperature oxidation behaviour was tested at 750 °C for virous exposure time. After high temperature oxidation tests, the microstructure analysis of all samples were investigated by means of metallographical examination, scanning electron microscopy (SEM) equipped with energy-dispersive X-ray spectrometer (EDS) and X-ray diffractometry (XRD).The results showed that the coating layers consisted of three layer, in the sequence of Al, Fe-Al and Si-rich layers from external topcoat to substrate. Nodules graphite had a blocking effect to retard the outward diffusion of Fe atoms and impeded the growth of Fe2Al5 in C-axis. Eventually, the cast iron substrate was oxidized directly by oxygen penetration via the greater cracks and pores to form Fe oxide nodules after 750 °C oxidation for 48h.

Abstract: The microstructure of oxide scale formed in the early stage of oxidation of cold-rolled sheets of 17%Cr-Mn-Ni austenitic stainless steel was examined using SEM and TEM. Samples were oxidized at 973 to1373K for 1 to 15min. Nodules were observed on the surfaces of specimens oxidized at 1173K. The nodules were composed of two layers, which comprised Fe oxides and Cr-rich Fe-Cr-Mn oxides, respectively. The other scale was composed of two layers of Fe-Cr-Mn oxides with different compositions. Nodules were not observed on the surfaces of the specimens oxidized at 973 and 1373K. After oxidation at 1373K for 1min, the scale was composed of three layers. The first layer consisted of Fe-Mn oxides with a spinel structure, the second consisted mainly of Cr oxides, and the third consisted of Cr-Mn oxides containing a small amount of Fe.