Tape Casting Process Research Articles

Tape Casting of Graphite Material: A New Electrochemical Sensor

AbstractTape casting is a feasible method for preparing ceramic tapes with different electrical and magnetic properties for multilayer ceramic devices. This paper describes the tape casting process for the preparation of a new kind of self‐standing carbon electrodes (SSCE) using different ratios of graphite and the organic additives generally used in the non‐aqueous tape casting process.

Aqueous tape casting of 10 mol%-Gd 2O 3-doped CeO 2 nano-particles

The aqueous tape casting process was systematically developed and investigated for the tape casting of 10 mol%-Gd 2O 3-doped CeO 2 nano-particles. This study focused on obtaining the optimum slurry formulations and on the effects of the processing parameters such as the stability, the rheology and the wetting properties on the tape characteristics. High solid loading (55 vol.%) and stable slurries of 10GDC nano-particles were achieved using poly(acrylic acid) (PAA) as a dispersant; poly(vinyl alcohol) (PVA) as a binder; poly(ethylene glycol) (PEG) as a plasticizer; octanol as a defoamer and 2,4,7,9-tetramethyl-5-decyne-4,7-diol ethoxylate as a surfactant. The pH values of the slurries were maintained in the range of 9.0–10.0. Homogeneous, defect-free green tapes (thickness 150–200 μm) with smooth surface and high relative green density (51.5%) were thus successfully obtained.

Tape casting of new electrolyte and anode materials for SOFCs operated at intermediate temperature

An important task in SOFC research is the reduction of the operating temperature to 700 °C, to avoid premature ageing of the cell components and the use of expensive interconnect materials. This requires the development of new electrolytes and electrodes materials. Oxyapatite electrolytes have recently attracted considerable attention and we have already reported some interesting performances for the La 9Sr 1Si 6O 26.5 composition ( σ = 8.8 × 10 −3 S cm −1 at 700 °C) [Beaudet Savignat, S., Lima, A., Barthet, C. and Henry, A., In Proceedings of the International Symposium Solide Oxide Fuel Cells VIII, Vol. 2003–2007, pp. 372–378]. This study was centered on the manufacturing of an apatite electrolyte and a Ni/apatite cermet anode by the tape casting process, with a view to the development of anode/electrolyte 1/2 cells. Slurries compositions were first optimized to adjust green tapes characteristics. Secondly, we focused on the binder burnout and the sintering. Dense electrolytes were synthesized. The influence of the particle size of the apatite powder, with a fixed NiO powder particle size, and the influence of the addition of pyrolyzable organic particles on the sintering and the microstructure of the anode material were studied.

Preparation by tape casting and hot pressing of copper carbon composites films

During this last decade, the use of metal matrix composites (MMCs) such as AlSiC or CuW for heat dissipation in microelectronic devices has been leading to the improvement of the reliability of electronic power modules. Today, the continuous increasing complexity, miniaturization and density of components in modern devices requires new heat dissipating films with high thermal conductivity, low coefficient of thermal expansion (CTE), and good machinability. This article presents the original use of copper carbon composites, made by tape casting and hot pressing, as heat dissipation materials. The tape casting process and the sintering have been adapted and optimised to obtain near fully dense, flat and homogeneous Cu/C composites. A good electrical contact between carbon fibres and copper matrix and a low porosity at matrix/copper interfaces allow obtaining a low electrical resistivity of 3.8 μΩ cm −1 for 35 vol.% carbon fibre (electrical resistivity of copper = 1.7 μΩ cm −1). The CTE and the thermal conductivity are strongly anisotropic due to the preferential orientation of carbon fibres in the plan of laminated sheets. Values in the parallel plan are, respectively, 9 × 10 −6 °C −1 and 160–210 W m −1 K −1 for 40 vol.% fibres. These CTE and thermal conductivity values are in agreement with the thermo-elastic Kerner's model and with the Hashin and Shtrikman model, respectively.

Aqueous tape casting of yttria stabilized zirconia

Tape casting process was used to produce yttria stabilized zirconia (YSZ) substrates in an aqueous system with poly(vinylalcohol) (PVA) and glycerine as binder and plasticizer, respectively. Various compositions of YSZ slips with different amounts of PVA and glycerine and consequently different solid/liquid ratios were prepared. The influence of the slip composition on the rheological properties of the slips was studied. In addition, the effect of the slip composition on the properties of the green and sintered tapes was investigated. PVA and glycerine did not affect the dispersion properties of the YSZ powder. Glycerine additions enhanced the flexibility of the green tapes but also produced a decrease in the tensile strength. The increase in the PVA content increased the tensile strength but resulted in a markedly decrease in the green density of the tapes. A correlation between the green and sintered density was found. The anisotropic sintering shrinkage parallel and perpendicular to the casting direction increased with increasing the PVA content. The slip compositions with 5wt% PVA produced green tapes with satisfactory tensile strength. They had the highest sintered density, the lower sintering shrinkage and the lesser shrinkage anisotropy.

Forming nanometer TiO 2 sheets by nonaqueous tape casting

The condition for the preparation of stable nanometer TiO 2 slurries by nonaqueous tape casting was indentified. To acquire stable low-viscosity slurries, the influences of solvent, dispersant and solid content on the rheological properties were investigated. The azeotropic mixtures (ethanol/methyl ethyl ketone) and Polyester/Polyamine Copolymer (KD-1) could serve as good solvent and dispersant, respectively. The slurries of nanometer TiO 2 behaved as near Newtonian up to a solid loading of 34 vol.%. Films of TiO 2 had very good qualities, such as homogeneity, surface quality, absence of bubbles and cracks, which indicated that slurries at selected conditions met the needs of tape casting process. The relative density of 24 and 34 vol.% sintered sheet was 51 and 69%, respectively. Results indicated the density increased with the solid content, sintering temperature and pressure.

Magnetoelectric Coupling in Bilayers of Pb(Zr, Ti)O3 Epoxy and Hot Pressed Manganite Perovskite

The synthesis and magnetoelectric (ME) characterizationof bilayers of Pb(Zr,Ti)O3 (PZT) and hot pressed manganiteperovskite La0.7Sr0.3MnO3 (LSMO) are discussed. Very strong ME interactions are measured for the bilayers. The bilayersexhibit superior ME coupling compared to thick-film composites preparedby tape casting process. Data of the ME voltage coefficient havebeen obtained as functions of bias magnetic field H, temperatureand frequency. The transverse coupling is stronger than thelongitudinal interactions and a maximum in the ME voltage coefficientis measured at 225 K. The frequency dependence of the ME voltagecoefficient reveals a peak at the electromechanical resonance due toradial modes.

Tapped Multilayer Bandpass Filter on Bi-Based Ceramics

Based on ceramic lamination, a multilayer microwave bandpass filter was fabricated with high dielectric constant (> 80), low temperature co-fired (∼950°C) Bi-based dielectric ceramics. Green ceramic sheets were manufactured by tape casting process and a gold conductive paste was used as the inner electrode. The filter is composed of two coupled stepped-impedance stripline resonators and the input/output ports of the filter are implemented with transmission lines directly tapped to resonators. Since the tapped lines and stepped-impedance resonators (SIRs) were arranged in the same layer, it makes the structure of filter simpler and needs fewer layers than the conventional input/output coupling structure. The admittance matrix for equivalent circuit of the tapped filter was obtained from the four-port coupled-line parameter matrix. The filter with tapped resonators was designed at center frequency at 1.8 GHz. The dimensions of the experimental filter are 4.5 mm × 3.2 mm × 1 mm.

Dispersion and tape casting of silicon carbide through aqueous route

Dispersion behaviour of SiC in aqueous media was studied using four different dispersants and as a function of pH. The slurry was characterized in each case by sedimentation, viscosity and rheological studies. The best dispersant was selected and its optimum amount was determined. For this system, the pH was varied over a range of 2–11. The slurry displayed the minimum viscosity as well as near-Newtonian behavior at pH range 8–11. SiC tapes were obtained by Double doctor blade tape-casting process, with polyvinyl alcohol as binder and PEG and BBP as plastisizers. The stability of the tape casting slurry was determined by rheological characteristics. As-cast tapes were dried in air at room temperature. The results show that it is possible to obtain homogenous defect-free green tapes of 57.7% solid loading and 53% green density with smooth surface using the optimized tape casting slurry.

Manufacturing of Structured TiO<sub>2</sub>-Surfaces for Cell Carrier Application

Titania surfaces were produced via a combined tape and slurry casting process. They were structured in the mm-µm range using structuring the gypsum, embossing the green ceramic, and lasering the sintered ceramic. The resulting structures were analyzed upon surface roughness and optically characterized by SEM. The ra values lay between 19-28 µm. Fibroblasts were seeded onto these structures, incubated for one and three days, and the number of cells was compared using polystyrol petri-dishes and borosilicate glass cover slips as references. It was demonstrated that the structure of the ceramic had an influence on the cell behaviour: larger cell numbers could be observed for the structured ceramics.

Fracture of Monoliths Fabricated by Stacking Water Processed Green Ceramic Tapes

A lamination technique for joining ceramic green tapes fabricated from aqueous ceramic slurries via tape casting process is investigated. Monolithic pieces with varying compositions within the Al2O3 / t-ZrO2 system were fabricated by gluing the constituent tapes and pressing at room temperature. The quality of the interfaces between the different tapes in sintered specimens was evaluated by means of the fracture behavior of the pieces during the ball on three balls test. Different fracture patterns were found as a function of pressure and the characteristics of the tapes. Large scale interface defects led to delamination during fracture whereas no critical defects could be observed in the smooth fracture surfaces. Small scale interface defects were revealed by fracture.

Rheological characterisation of water-based AlN slurries for the tape casting process

In the present work rheological properties of aqueous concentrated AlN suspensions have been investigated in the presence of a sintering aid, deffloculant, binder and plasticizers, in order to screen the most suitable experimental conditions to obtain a good rheological behaviour for tape casting thick and non-cracked tapes with good flexibility. Suspensions exhibiting the desired shear thinning behaviour could be prepared. Adding binder and plasticizers did not change the shear thinning behaviour, but the viscosity revealed an increasing trend with increasing added amounts of binder. The flexibility was improved for the tapes derived from the more viscous suspensions containing higher amounts of binder. Crack free tapes having a maximum thickness of 1.5 mm, and with binder and plasticizer contents in the ranges of 10–15 wt.% and 5–10 wt.%, respectively, could be obtained.

Influence of the slip composition on the aqueous processing and properties of yttria stabilized zirconia green tapes

The tape-casting process was used to produce yttria stabilized zirconia (YSZ) substrates in an aqueous system with poly(vinylalcohol) (PVA) and glycerine as binder and plasticizer, respectively. Various compositions of YSZ slips with different amounts of PVA and glycerine and consequently different solid/liquid ratios were prepared. The influence of the slip composition on the rheological properties of the slips and the drying kinetics of the cast tapes were studied. In addition, the effect of the slip composition on the properties of the resultant green tapes was investigated. PVA and glycerine did not affect the dispersion properties of the YSZ powder. The slip composition had influence only on the second stage of the drying kinetic; for a constant PVA content, the slips with higher amounts of glycerine resulted in tapes with higher drying rate. Glycerine additions enhanced the flexibility of the green tapes but also produced a decrease in the tensile strength. The increase in the PVA content increased the tensile strength but resulted in a marked decrease in the green density of the tapes. The slip compositions with 5 wt.% PVA produced green tapes with satisfactory tensile strength which had the highest green density. Since a greater amount of glycerine resulted in tapes with higher drying rate and enhanced the flexibility of the green tapes, the slip composition 5 wt.% PVA–7.1 wt.% glycerine was adequate for the production of YSZ substrates through the tape-casting process.

Effect of CNT distribution on tribological behavior of alumina–CNT composites

Alumina–carbon nanotube (CNT) composites with a different volume fraction of CNTs were fabricated by two different processing methods to investigate the effect of the distribution of CNT in the ceramic matrix on the tribological behavior. Alumina–CNT composites with CNT content up to 12 wt.% were fabricated by tape casting, followed by lamination and hot pressing. For the comparison, composites with the same composition were prepared by hot pressing. The friction and wear behaviors of the CNT reinforced composites were investigated using a ball-on-reciprocating wear tester under an unlubricated condition at room temperature. The wear rate of hot-pressed samples decreased with increasing up to 4 wt.%, but increased with further addition of CNT. The wear rate of the tape casted composites decreased steadily with increasing CNT addition up to 12 wt.%. Density and mechanical properties depending on CNT addition were measured. SEM was employed to observe worn and unworn surface. All the results demonstrated that tape casting process significantly improved the uniform distribution of CNT in the alumina, resulting in enhanced wear resistance of composites.

Structure and electrical properties of PMN-PZT micro-actuator deposited by tape-casting process

A potential application for Pb(Mg1/3Nb2/3)O3-Pb(Zr0.52T{i}0.48)O3 (PMN-PZT) piezoelectric material is micro positioning and actuation for hard disk drives. And this material was developed and the processing of a piezoelectric multilayer element for stacking and co-firing Ag/Pd electroded tape casting layers was investigated. The formation mechanisms of PMN-PZT ternary solid solution prepared by the mixed oxides techniques has been characterized by differential thermal analysis (DTA) and thermal gravimetric analysis (TGA). The sintered microstructure and composition of the PMN-PZT multilayer elements were investigated by scanning electron microscope (SEM), and X-ray spectrometer (EDX). The data from DTA/TGA stress the importance of a slow debonding from room temperature to 500 ∘C. The joining of the electrode to the PMN-PZT layer confirms that the internal electrodes are well defined and is well interconnected to the PMN-PZT layer. The ferroelectric polarization-electric (P-E) hysteresis loops of the piezoelectric films were also measured. The remanent polarization and coercive field calculated from the P-E curves decreased with decreasing the number of PMN-PZT multilayer films from 10-layer to 4-layer. After that, a novel U-type micro-actuator attached to each side via piezoelectric elements was also practically measured by laser Doppler vibrometer in order to testify the driving mechanics of it. The highest displacement/voltage sensitivity of 1.496 μm/±20 V is achieved by the micro-actuator with two 10-layer elements. The corresponding resonance frequency of the sway mode is high at 12 kHz.

Dispersion of Si 3N 4 powders in aqueous media

The stability of Si 3N 4 suspensions was studied and characterized in terms of zeta potential, sedimentation, apparent viscosity and rheology measurements. Zeta potential measurement showed that the isoelectric point (IEP) of the as-treated Si 3N 4 particles was pH ∼ 4.6. The ratio between the number of surface amine groups per unit area N B, and the number of surface silanol groups per unit area, N A, was calculated as 0.007. As silanol groups are expected to show acidic behavior, a cationic polymer, PEI was selected as dispersant. After the adsorption of PEI, The IEP of Si 3N 4 particles shifted to pH 10.4. The surface dissociation behavior of Si 3N 4 particles in aqueous media was also studied and related to the slurry stability. Based on the sedimentation, apparent viscosity and rheological measurements, the optimal slurry for tape-casting process can be obtained at pH 9.3 with 1 wt.% PEI as dispersant. It was shown that PEI is an effective dispersant for Si 3N 4 particles in aqueous media.

The Interface and Grain Growth in Cofired Ferroelectric / Ferrite Multilayer Composites

The multilayer composites were prepared by cofiring Pb(Ni1/3Nb2/3)O3-based ferroelectrics and NiCuZn ferrite using tape casting processes. The interface and grain growth of the composites were investigated. The results show that the sintered interface of composites is solid, continuous with no delamination and cracks, which should be attributed to the chemical compatible of the two materials. The grain growth of ferroelectrics adjacent to the interface is different from that far from the interface. It should attribute to Fe3+ diffused from the ferrite to ferroelectrics and soluted into the perovskite lattice. The difference factor dD is proposed to describe the microstructure difference between the interface and the inner parts.

Investigation of Device Performance and Process Capability for Accurate SOFC Cost Estimates

Manufacturing and production costs are a major concern for the development and commercialization of solid oxide fuel cells (SOFCs) [1]. A current review of research indicates that device geometries with thin (<30 μm) film layers and reduced stack temperature gradients will be required to meet device performance and reliability requirements [2]. We have developed a process based cost model for high volume manufacturing of SOFC devices [3]. This work investigates the sensitivity SOFC device manufacturing costs with respect to device performance and reliability requirements. We have incorporated process capability requirements to determine at what performance level process capability must be considered to provide an accurate cost model, enabling a determination of cost viability for device designs prior to manufacturing investment. We have also investigated the cost of process capability against the potential savings in balance of plant costs as device operation temperatures are reduced. Our work indicates that the device designs requiring electrolyte films at less than 30 μm result in a cost difference of up to $50 per unit cell, for traditional screen printing and tape casting processes. Additionally, our investigation indicates that the savings in materials and manufacturing for BOP costs at lower temperatures may not be offset for operation temperatures below 700°C for cell maximum power densities of 1 W/cm 2 . Additionally, cost performance maps are used to indicate optimum performance and operation temperature regimes for 5 kW system cost minimization.

Aqueous tape casting processing of low dielectric constant cordierite-based glass-ceramics—selection of binder

In this paper, four different binders were investigated in the process of aqueous tape casting of cordierite-based glass-ceramics and their effects on the rheological behaviour of the suspensions and on the microstructures of the green tapes were compared. Meanwhile, a good compatibility between the dispersant and binder was found to be a predominant factor to obtain an optimised cordierite glass-ceramic tape. The microstructure of the green tape was observed by SEM and the weight loss during binder burn out process was determined by DTA/TG. The dielectric constant and dielectric loss of the sintered tapes (at 1150 °C for 2 h) was also measured.

Sintering and microwave dielectric properties of LTCC-zinc titanate multilayers

The effects of ZnO–B 2O 3–SiO 2 (ZBS) on the sintering behavior and microwave dielectric properties of ZnO–TiO 2 system were investigated as a function of ZBS content and sintering temperature. Densities of the specimens were enhanced with an increase of ZBS up to 2 wt.% and then decreased. X-ray diffractometry analyses results indicated that the phase stability region of the hexagonal ZnTiO 3 extended to lower temperatures as the amount of ZBS increased. The dielectric properties of ZnO–TiO 2 system with ZBS are strongly dependent on the sintering conditions, especially near the phase decomposition temperature. The sintering temperature of the specimens could be reduced to 900 °C without the degradation of the microwave dielectric properties. From 900 °C, the temperature compensation characteristics occurred as the phase composition changed from ZnTiO 3 to two phases: Zn 2TiO 4 and rutile. The dielectric constant ( ɛ r) increased and Q×f value decreased due to the phase decomposition. The ɛ r value of 27, Q×f value of 19,396 (at 6 GHz) and τ f value of 2 ppm/°C were obtained for ZnO–TiO 2 ceramics with 2.0 wt.% ZBS sintered at 900 °C for 3 h. The low-temperature sintering ceramics powders were suitable for the tape casting process. Also, the material is compatible with Ag electrodes and, therefore, is suitable for LTCC application.