Papers by Keyword: Tape-Casting

Abstract: The hydrogen is promising energy carrier due to its high energy density, convenient transportation, eternal sources in the earth and cleanness. Solid oxide fuel cells (SOFCs) have not been commercialized yet even though it has been studied for decades. The issues about solid oxide fuel cells are manufacturing process and electrochemical performance. Tape-casting process has an advantage of cost reduction for mass production. it is reported that infiltration improves electrochemical performance of SOFCs by enhancing the three phase boundary (TPB) and porosity. To fabricate the electrode with porous scaffold structure for infiltration, pore formers were added in the tape-casting slurry. In this study, four types of mixtures of several pore formers such as carbon black, graphite, poly methyl methacrylate and glassy carbon were estimated. Micro structure of each type is investigated through scanning electron microscope (SEM). The thickness of the unit cell manufactured by tape-casting is in the range of 200 - 250 μm. The fabricated unit cell with carbon black and glassy carbon shows the open circuit voltage 1.07 V at 800°C. As a result of the study, mixed ratio of pore formers was researched for Solid Oxide Fuel Cells manufacturing process applied by tape-casting and infiltration method.

Abstract: A thin ScSZ electrolyte with a large area was synthesized using the tape-casting method. The conductivity of 0.095 S cm^-1 at 800°C was achieved. The maximum power density of a single cell reached 368 mW cm^-1 at 800°C. To make a large electrolyte battery more suitable, our study improves the casting method of preparing a dense, porous electrolyte substrate that promotes surface roughness of the electrolyte. However, it is difficult to control the thickness of the substrate, meaning that further improvements are needed.

Abstract: In this paper, the W-Cu functionally graded material (FGM) was prepared by using the non-aqueous tape-casting technique combined with vacuum hot-pressing sintering. The graded composite material with high density, uniform transition and graded component was designed by 7 layers with the copper content range from 40 to 100 wt. %. Then the structures and properties of the composite were characterized. The scanning acoustic microscope (SAM) results for the W-Cu graded material showed that the interface between different layers was of high smoothness and parallel. The SEM-EDS results of cross section show that the W and Cu content changed gradually along the laminating direction after sintering. The equivalent electrical conductivity and the equivalent thermal conductivity of the W-Cu graded material were 0.3976×10⁸ S/m and 323.5 W/(m·K), respectively, which were much higher than that of the W-40 wt. % Cu homogeneous composite. The Vickers hardness of the high tungsten content surface and the high copper surface were 163 HV and 80 HV, respectively, which were same with that of the homogeneous material.

Abstract: Tape-casting technology is introduced to fabricate metal-arrayes patterned ceramic substance containing periodic multilayer silver wire structure in the low dielectric constant ceramic matrix for microvave bandgap materials and left hand material application. One important advantage of the metal patterned ceramic substance comparing with the periodic structures fabricated on the printed circuit boards (PCB) using a shadow mask/etching technique is that complex multilayer structure can be designed and fabricated in the ceramic body as well as on the surface by the tape-casting process, while the shadow mask/etching technique technology can only design patterns on the surface of printed circuit boards. An Hp8720ES network analyzer was used to measure the transmission properties of the metal patterned ceramic substance. The experimental result shows some novel properties at X-band microwave frequencies. The metal patterned ceramic substance can be used in the microwave communication, such as microwave antenna.

Abstract: Techniques for producing near net shape ceramic components using aqueous forming processes are reviewed. Particular focus is on three dimensional, complex shape forming by gel casting and thin film forming by tape casting. Recent progress has been made in formulations that rely on dispersion of submicron ceramic particles in aqueous solutions containing polymers such as chitosan or poly vinyl alcohol and a temperature activated crosslinking agent (DHF, 2,5-dimethoxy- 2,5-dihydrofuran). These formulations can be produced to have low viscosity so that they can either be poured or injected into complex shape molds or cast into tapes. After casting, the suspension is heated to about 70 oC to activate the crosslinking agent. During crosslinking of the polymer, the rheological and mechanical behavior of the suspension is changed from liquid-like to solid-like. This allows the complex shaped bodies to be removed from the mold, dried and sintered. The strengthening of the cast tape due to crosslinking the polymer allows it to be dried without cracking. Rheological and mechanical behaviour, green and fired densities as well as examples of formed components will be presented. The green bodies can be readily machined with common high speed tool steel tools.

Abstract: Silicon nitride ceramics was prepared by tape casting nonaqueous ceramic slurries, laminating the green ceramic tapes, and gas pressure sintering in nitrogen atmosphere. Lu2O3 and SiO2 were used as the sintering additives, and 3 wt.% β-Si3N4 seed was added to enhance β-Si3N4 grain growth unidirectionally. The seeded and tape-cast Si3N4 showed very good high temperature bending strength at 1500oC, when the stress applied along with the grain alignment direction. This was attributable to the formation of a high melting point grain boundary phase and the fibrous Si3N4 grains alignment. After exposure in air at 1500oC for up to 100 h, the oxidation products formed on the Si3N4 surface consist of Lu2Si2O7 and SiO2. The bending strength of the oxidized and tape-cast Si3N4 was degradation, the strength decrease was associated with the formation of new defects on the surface and the interface between the oxide layer and the Si3N4 bulk.