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Lanyi Wang - One of the best experts on this subject based on the ideXlab platform.
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Research on a high performance multilayer ZnO varistor and its fabrication with water based Tape Casting
2010Co-Authors: Lanyi WangAbstract:With the rapid development of small size, low working voltage and high reliability of electronic products, the demands for multilayer chip varistors (MLV) which are designed for surge protection and electrostatic discharge (ESD) protection in circuits are increasing rapidly and the requirements for the MLV’s properties become stricter. In order to meet the demands of "green" production methods in an environmental protection modern world, it is important to study environmentally friendly water-based (aqueous) Tape Casting and the replacement of solvent-based (non-aqueous) Tape Casting with aqueous Tape Casting. In this study, using chemically synthesized doped zinc oxide (CS powder) as the starting powder, high performance multilayer ZnO varistors were prepared with water-based Tape Casting. For the first time, high performance multilayer ZnO varistors were successfully fabricated using both water-based Tape Casting and a chemically synthesized compound powder. The MLVs made by water-based Tape Casting exhibit better electrical properties than those made using the solvent-based Tape Casting. Water-based Tape Casting reduces MLV’s production costs and reaches the goal of environmentally friendly green production, resulting in great social and economic benefits. The electrical properties of MLVs made by CS powder were compared with those made by metal oxide powder (MO powder). The effect of sintering temperature on the electrical properties of MLVs was studied. With the help of microstructure analysis and electrical property measurement of the MLVs, the MLVs made by CS powder display superior electrical properties as a result of their uniform microstructure throughout. The optimal sintering temperature range for our MLVs is 950℃~1050℃. Water-based Tape Casting process was studied. The influence of a water-soluble binder and dispersant on the Tape Casting slurry was analyzed. The aqueous slurry with shear thinning rheological behavior which was desirable for Tape Casting was successfully developed by the optimization study of slurry composition. The aqueous slurry could be stabilised electrosterically by the dispersant. The MLV green sheets were successfully made with water-based Tape Casting. Water-based Tape Casting process was compared with solvent-based Tape Casting. The microstructure and electrical properties of the MLVs made by water-based Tape Casting were also compared with those made by solvent-based Tape Casting. The aqueous green Tape is denser than the non-aqueous one. The multilayer ZnO varistors prepared by aqueous Tape Casting display better electrical properties than those prepared using non-aqueous Tape Casting. We believe that these superior electrical properties are a direct result of the well dispersed and stable slurry with a shear thinning rheological behavior, which makes dopants distribute more uniformly throughout the MLVs. We conclude that water-based Tape Casting can replace solvent-based Tape Casting for the manufacture of high performance multilayer ZnO varistors considering MLV production…
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Preparation and electrical properties of multilayer ZnO varistors with water-based Tape Casting
Ceramics International, 2009Co-Authors: Lanyi Wang, Guoyi Tang, Zheng Kui XuAbstract:Multilayer ZnO varistors were prepared by water-based Tape Casting with water-soluble acrylic as binders. Zeta potentials of the doped ZnO suspensions as a function of pH with and without dispersant were measured. Viscosity measurements were used to find the optimum dispersant concentration needed to prepare a stable slurry. Viscosity properties of the Tape Casting slurry were investigated. The results showed that aqueous acrylic binders have shear thinning properties suitable for Tape Casting of ceramic powders. Scanning electron microscopy (SEM) studies revealed that the green sheets have a smooth defect-free surface and that the multilayer varistor (MLV) ceramics prepared by water-based Tape Casting have a fine grain microstructure with a uniform grain size and dopant distribution. The multilayer ZnO varistors prepared by water-based Tape Casting display comparable good electrical properties to those prepared by solvent-based Tape Casting. This is believed to be attributed to the well dispersed water-based slurry, which makes more uniform dopant distribution throughout the multilayer ZnO varistors. Therefore, water-based Tape Casting is suitable for the manufacture of high performance multilayer ZnO varistors. © 2008 Elsevier Ltd and Techna Group S.r.l.
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preparation and electrical properties of multilayer zno varistors with water based Tape Casting
Ceramics International, 2009Co-Authors: Guoyi Tang, Lanyi Wang, Zheng Kui XuAbstract:Multilayer ZnO varistors were prepared by water-based Tape Casting with water-soluble acrylic as binders. Zeta potentials of the doped ZnO suspensions as a function of pH with and without dispersant were measured. Viscosity measurements were used to find the optimum dispersant concentration needed to prepare a stable slurry. Viscosity properties of the Tape Casting slurry were investigated. The results showed that aqueous acrylic binders have shear thinning properties suitable for Tape Casting of ceramic powders. Scanning electron microscopy (SEM) studies revealed that the green sheets have a smooth defect-free surface and that the multilayer varistor (MLV) ceramics prepared by water-based Tape Casting have a fine grain microstructure with a uniform grain size and dopant distribution. The multilayer ZnO varistors prepared by water-based Tape Casting display comparable good electrical properties to those prepared by solvent-based Tape Casting. This is believed to be attributed to the well dispersed water-based slurry, which makes more uniform dopant distribution throughout the multilayer ZnO varistors. Therefore, water-based Tape Casting is suitable for the manufacture of high performance multilayer ZnO varistors.
Andreas Roosen - One of the best experts on this subject based on the ideXlab platform.
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STEEL-SHEET FABRICATION BY Tape Casting
International Journal of Powder Metallurgy, 2008Co-Authors: Mascha Rauscher, Georg Besendörfer, Andreas RoosenAbstract:A new method of manufacturing thin, planar metal sheet has been developed by adapting ceramic Tape-Casting technology to powder metallurgy (PM). By combining the advantages of PM with those of the Tape-Casting technique, a low-cost process for the production of thin planar metal forms has been demonstrated. A stainless steel 316L powder was used as a model system to form a Tape-Casting slurry with preset rheological behavior for the subsequent Casting process. After drying the cast slurry, a flexible green Tape was obtained with sufficient strength and flexibility to withstand further handling by cutting and lamination. The Tape was densified by sintering to produce a flexible metal sheet. The mechanical properties and attendant microstructures of the steel sheet were determined and characterized. In addition a simple, novel joining technique was established by lamination of the green metal sheets, followed by sintering, resulting in a stable homogenous microstructure.
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Steel-sheet fabrication by Tape Casting
International Journal of Powder Metallurgy (Princeton New Jersey), 2008Co-Authors: Mascha Rauscher, Georg Besendörfer, Andreas RoosenAbstract:Tape-Casting technology, an established ceramic forming technique, can be used in powder metallurgy (PM) as a powerful, versatile, and low-cost shaping process. The technology is extensively used in the ceramics industry for the manufacture of thin, planar ceramic products of large area with uniform surface quality and accurate dimensions. Steel sheets were produced using Tape-Casting a 316L stainless steel powder-filled slurry with preset rheological behavior to form a green Tape, which was subsequently sintered under nitrogen to prevent oxidation. Residual agglomerates and milling debris were removed by filtration before Casting. Optimum sheet densities were obtained at a sintering temperature of 1,250?C with densities of 92% PFD for single sheets. The sintered sheets achieved a tensile strength similar to that of rolled annealed 316 stainless steel. No thickness effect was observed in relation to the microstructures.
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Rheological characterization of water-based slurries for the Tape Casting process
Ceramics International, 2002Co-Authors: Bernd Bitterlich, Christiane Lutz, Andreas RoosenAbstract:Rheological properties of aqueous Tape Casting slurries have been investigated as they strongly affect the Tape Casting process and the quality of the final product. The aqueous slurries consist of yttria stabilized zirconia and a polymeric latex emulsion as the binder. The viscosity, its time dependent behavior and the strength of the internal structure of the slurry were characterized by static and dynamic measurements using a cone-plate viscosimeter. The results were compared with the properties of the pure latex emulsion binder. The ceramic slurries exhibit the desired strong pseudoplastic, but non-thixotropic behavior. Due to the high solids content the slurries show distinctive elastic properties below a critical shear stress. Above the critical shear stress the internal structure is broken up and the viscous properties become predominant. The paper demonstrates that the measurement of the viscosity, its time dependent behavior and the strength of the internal structure of the slurry are excellent tools to characterize the suitability of a ceramic slurry for the Tape Casting process. © 2002 Elsevier Science Ltd. and Techna S.r.l. All rights reserved.
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rheological characterization of water based slurries for the Tape Casting process
Ceramics International, 2002Co-Authors: Bernd Bitterlich, Christiane Lutz, Andreas RoosenAbstract:Rheological properties of aqueous Tape Casting slurries have been investigated as they strongly affect the Tape Casting process and the quality of the final product. The aqueous slurries consist of yttria stabilized zirconia and a polymeric latex emulsion as the binder. The viscosity, its time dependent behavior and the strength of the internal structure of the slurry were characterized by static and dynamic measurements using a cone-plate viscosimeter. The results were compared with the properties of the pure latex emulsion binder. The ceramic slurries exhibit the desired strong pseudoplastic, but non-thixotropic behavior. Due to the high solids content the slurries show distinctive elastic properties below a critical shear stress. Above the critical shear stress the internal structure is broken up and the viscous properties become predominant. The paper demonstrates that the measurement of the viscosity, its time dependent behavior and the strength of the internal structure of the slurry are excellent tools to characterize the suitability of a ceramic slurry for the Tape Casting process.
Zheng Kui Xu - One of the best experts on this subject based on the ideXlab platform.
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Preparation and electrical properties of multilayer ZnO varistors with water-based Tape Casting
Ceramics International, 2009Co-Authors: Lanyi Wang, Guoyi Tang, Zheng Kui XuAbstract:Multilayer ZnO varistors were prepared by water-based Tape Casting with water-soluble acrylic as binders. Zeta potentials of the doped ZnO suspensions as a function of pH with and without dispersant were measured. Viscosity measurements were used to find the optimum dispersant concentration needed to prepare a stable slurry. Viscosity properties of the Tape Casting slurry were investigated. The results showed that aqueous acrylic binders have shear thinning properties suitable for Tape Casting of ceramic powders. Scanning electron microscopy (SEM) studies revealed that the green sheets have a smooth defect-free surface and that the multilayer varistor (MLV) ceramics prepared by water-based Tape Casting have a fine grain microstructure with a uniform grain size and dopant distribution. The multilayer ZnO varistors prepared by water-based Tape Casting display comparable good electrical properties to those prepared by solvent-based Tape Casting. This is believed to be attributed to the well dispersed water-based slurry, which makes more uniform dopant distribution throughout the multilayer ZnO varistors. Therefore, water-based Tape Casting is suitable for the manufacture of high performance multilayer ZnO varistors. © 2008 Elsevier Ltd and Techna Group S.r.l.
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preparation and electrical properties of multilayer zno varistors with water based Tape Casting
Ceramics International, 2009Co-Authors: Guoyi Tang, Lanyi Wang, Zheng Kui XuAbstract:Multilayer ZnO varistors were prepared by water-based Tape Casting with water-soluble acrylic as binders. Zeta potentials of the doped ZnO suspensions as a function of pH with and without dispersant were measured. Viscosity measurements were used to find the optimum dispersant concentration needed to prepare a stable slurry. Viscosity properties of the Tape Casting slurry were investigated. The results showed that aqueous acrylic binders have shear thinning properties suitable for Tape Casting of ceramic powders. Scanning electron microscopy (SEM) studies revealed that the green sheets have a smooth defect-free surface and that the multilayer varistor (MLV) ceramics prepared by water-based Tape Casting have a fine grain microstructure with a uniform grain size and dopant distribution. The multilayer ZnO varistors prepared by water-based Tape Casting display comparable good electrical properties to those prepared by solvent-based Tape Casting. This is believed to be attributed to the well dispersed water-based slurry, which makes more uniform dopant distribution throughout the multilayer ZnO varistors. Therefore, water-based Tape Casting is suitable for the manufacture of high performance multilayer ZnO varistors.
Madhusudhanan Balasubramanian - One of the best experts on this subject based on the ideXlab platform.
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Optimization of barium titanate nanopowder slip for Tape Casting
Journal of Materials Science, 2006Co-Authors: V. Vinothini, Paramanand Singh, Madhusudhanan BalasubramanianAbstract:Dispersion of barium titanate nano powder of average particle size ∼30 nm in different solvent systems of Tape Casting (toluene–ethanol, methyl ethyl ketone–ethanol, xylene–ethanol) along with Triton x-100 or phosphate ester as dispersants has been studied using sedimentation experiments. The influence of different parameters such as type of solvent system, dispersant and concentration of dispersant on BaTiO3 slip dispersion, viscosity and the properties of green Tape were studied. The optimal concentration of dispersant was determined from the minimum slip viscosity. Xylene–ethanol with phosphate ester was found to be the best solvent and dispersant system for Tape Casting. Defect free, denser and smooth green Tapes are formed with this system.
Guoyi Tang - One of the best experts on this subject based on the ideXlab platform.
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Preparation and electrical properties of multilayer ZnO varistors with water-based Tape Casting
Ceramics International, 2009Co-Authors: Lanyi Wang, Guoyi Tang, Zheng Kui XuAbstract:Multilayer ZnO varistors were prepared by water-based Tape Casting with water-soluble acrylic as binders. Zeta potentials of the doped ZnO suspensions as a function of pH with and without dispersant were measured. Viscosity measurements were used to find the optimum dispersant concentration needed to prepare a stable slurry. Viscosity properties of the Tape Casting slurry were investigated. The results showed that aqueous acrylic binders have shear thinning properties suitable for Tape Casting of ceramic powders. Scanning electron microscopy (SEM) studies revealed that the green sheets have a smooth defect-free surface and that the multilayer varistor (MLV) ceramics prepared by water-based Tape Casting have a fine grain microstructure with a uniform grain size and dopant distribution. The multilayer ZnO varistors prepared by water-based Tape Casting display comparable good electrical properties to those prepared by solvent-based Tape Casting. This is believed to be attributed to the well dispersed water-based slurry, which makes more uniform dopant distribution throughout the multilayer ZnO varistors. Therefore, water-based Tape Casting is suitable for the manufacture of high performance multilayer ZnO varistors. © 2008 Elsevier Ltd and Techna Group S.r.l.
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preparation and electrical properties of multilayer zno varistors with water based Tape Casting
Ceramics International, 2009Co-Authors: Guoyi Tang, Lanyi Wang, Zheng Kui XuAbstract:Multilayer ZnO varistors were prepared by water-based Tape Casting with water-soluble acrylic as binders. Zeta potentials of the doped ZnO suspensions as a function of pH with and without dispersant were measured. Viscosity measurements were used to find the optimum dispersant concentration needed to prepare a stable slurry. Viscosity properties of the Tape Casting slurry were investigated. The results showed that aqueous acrylic binders have shear thinning properties suitable for Tape Casting of ceramic powders. Scanning electron microscopy (SEM) studies revealed that the green sheets have a smooth defect-free surface and that the multilayer varistor (MLV) ceramics prepared by water-based Tape Casting have a fine grain microstructure with a uniform grain size and dopant distribution. The multilayer ZnO varistors prepared by water-based Tape Casting display comparable good electrical properties to those prepared by solvent-based Tape Casting. This is believed to be attributed to the well dispersed water-based slurry, which makes more uniform dopant distribution throughout the multilayer ZnO varistors. Therefore, water-based Tape Casting is suitable for the manufacture of high performance multilayer ZnO varistors.
