Seongjin Hwang

Effect of anorthite and diopside on dielectric properties of Al2O3/glass composite based on high strength of LTCC substrate

The green sheet of an alumina filler/glass matrix, which is a glass–ceramic based on an anorthite and diopside composite, is a low-fired substrate material for microelectronic packaging. In this study, alumina/glass sheets were prepared using a tape-casting process. The mechanical and dielectric properties of the sintered bodies were examined as a function of the sintering temperature. The volume of the crystalline phases was considered with the peak area of the XRD intensity for evaluating the alumina/glass composite. The flexural strength and dielectric properties of the sintered alumina/glass composites were 167.2 ± 13.1 MPa for the four-point bending test, 5.51 for the dielectric constant and 2,078 MHz for the quality factor, respectively. The dielectric constant was dependent on the volume of crystalline phases present.

Mechanical and acid-etching properties of Bi2O3–ZnO–B2O3 glass-containing ceramic fillers

The properties of the composite, having a complicated microstructure, are decided by many factors such as those of glass matrix, crystal phases, fillers, and holes. We investigated how the addition of ceramic fillers to the glass matrix affects the mechanical and etching properties of the glass composite by forming new crystal phases. Different amounts of two fillers, ZnO and Al2O3, were added to a glass frit consisting of Bi2O3–ZnO–B2O3. It was sintered at 550 °C for 30 min. Based on the results of this study, the porosity and degree of crystallization of the composites could be controlled by adjusting the content of the ZnO and Al2O3 fillers. Therefore, porosity and degree of crystallization formed by the reaction between a glass matrix and fillers influence the mechanical and etching properties of the composite.

O-phase and carbides precipitation in intermetallics based on Ti−Al

In Ti−Al based intermetallics, precipitates of several ternary phases, such as the orthorhombic O-phase, perovskite P-phase and hexagonal H-phase structures, were experimentally identified during aging. These phases are believed to develop from the matrix of the α2-phase as a result of the characteristic diffusion of the alloying elements that involves changes in chemical composition and lattice structure. In this paper, the formation mechanism of these phases was studied in the matrix of Ti−Al-based intermetallic compounds. The O-phase was found to form in the primary equiaxed α2 grains in multivariant forms and as fine α2+O mixtures in Ti-24A1-14Nb-3V-0.5Mo alloy during solution treatment at 1000°C/1h followed by water quenching and aging at 650°C and 850°C. The supersaturation of Nb, the β stabilizer, resulted in a segregation of the Nb-rich region and Nb-poor region, incurring the formation of the O-phase as a consequence of the α2-phase decomposition. A crystallographic orientation relationship between the α2-phase and the O-phase was observed. In Ti-46.6A1-2Mn-1.4Mo-0.3C alloy, P-phase carbides formed mainly at the α2/γ interface whereas some H-phase carbides were also found within the γ grain and at prior α grain boundaries. The presence of ledges between the P-phase and α2-phase interfaces indicated that the nucleation stage of the P-phase involved an interface-controlled process with a coherency relationship at the interface.

Electrical Properties of Screen Printed Silicon Solar Cell Dependent upon Thermophysical Behavior of Glass Frits in Ag Pastes

Ag pastes consist of Ag powder, vehicles, glass frits and additives, such as bismuth, aluminum and zinc. Pb–Bi oxide glass frits have been used in Ag pastes of silicon solar cells. The glass frit plays important roles in Ag paste. However, there are few studies of glass frit in Ag paste for silicon solar cell. In this study, the screen-printed silicon solar cell was investigated with Pb–Bi oxide glass frits in Ag pastes. The electrical properties of fabricated silicon solar cell were correlated to the viscous flow of glass frits in the Ag pastes during the fast firing. The glass particles were spread perfectly over the Ag and SiNx substrates with decreasing contact angle at approximately 700 °C. Based on our results, the thermophysical properties of Pb–Bi oxide glass frits can be helpful for understanding the contact formation of silicon solar cell and improving the solar cell performance.

Shape change of Ag electrode with shrinkage difference between electrode and dielectric in PDP

In PDP, edge-curl is one of the problems encountered as a result of an interaction between the transparent dielectric and the bus electrode, and has a deleterious effect on the electrical efficiency of the PDP. Edge-curl can increase its height while sintering the dielectric. Therefore, it is important to know the effect of the dielectric on the electrode. This study examined the shape change of the electrode as a function of the sintering temperature by scanning electron microscopy. The thermal properties of the electrode and the dielectric were measured by TG-DTA and dilatometer. Based on these results, a faster reaction of the dielectric around the electrode and the difference in shrinkage between the dielectric and the electrode were found to be causes of the occurrence and deepening of edge-curl.

Microstructural development of Ti-24Al-14Nb-3V-0.5Mo alloy during hot tensile deformation

AbstractMicrostructure of the Ti-24Al-14Nb-3V-0.5Mo (at.%) alloy deformed from room temperature to 700°C was studied by the H-800 transmission electron microscope (TEM) equipped with a side entry goniometer stage capable of ±45° tilt on the X or Y axis operating under two-beam condition. Especially dislocation types and slip systems of the α2-phase (D019) were analyzed in accordance with

Surface Morphology and Reflectance of Calcite Filler in Glass Composites

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Modification of Frit Surface by Thermal Treatment for a Transparent Dielectric in Plasma Display Panel

invisibility criterion. The results indicated that with increasing the deformation temperature from room temperature to 700°C, the slip of