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Emanuel Sachs - One of the best experts on this subject based on the ideXlab platform.
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High Green Density ceramic components fabricated by the slurry-based 3DP process
Solid Freeform Fabrication Proceedings, 1997Co-Authors: Jason Grau, Jason E. Grau, Scott A. Uhland, Michael J. Cima, Jooho Moon, Emanuel SachsAbstract:The 3DP process has been modified to directly fabricate high Green Density parts using submicron powder. The slurry-based 3DP process deposits the powder bed by spraying a dispersed slurry of the component material onto a piston. Alumina, silicon nitride, and lead zirconate titanate components with Green densities as high as 67% have been fabricated by the slurry-based 3DP process. Solution phase binder systems have proven to be successful for the new process. Substantially improved surface finish over the conventional dry powder-based 3DP process has been demonstrated. Layer heights less than 50 Jlm can be prepared with this process. Thus, the stepped surface topography commonly observed in solid free form parts is substantially reduced.
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High Green Density ceramic components fabricated by the slurry-based 3DP process
1997Co-Authors: Jason E. Grau, Scott A. Uhland, Michael J. Cima, Jooho Moon, Emanuel SachsAbstract:The 3DP process has been modified to directly fabricate high Green Density parts using submicron powder. The slurry-based 3DP process deposits the powder bed by spraying a dispersed slurry of the component material onto a piston. Alumina, silicon nitride, and lead zirconate titanate components with Green densities as high as 67% have been fabricated by the slurry-based 3DP process. Solution phase binder systems have proven to be successful for the new process. Substantially improved surface finish over the conventional dry powder-based 3DP process has been demonstrated. Layer heights less than 50 Jlm can be prepared with this process. Thus, the stepped surface topography commonly observed in solid free form parts is substantially reduced. Introduction Structural ceramic components require fine-grained starting powders and high Green Density in order to achieve near theoretical Density after firing. Wet processing techniques such as slip casting and injection molding are commonly used in ceramic forming processes to produce parts that meet these criteria. Structural ceramic components have been fabricated in the past with 3DP using spray-dried powders. These powders are -50 J.lm agglomerates of submicron powder. Spray-dried powders were easily spread into uniform layers, but printed components had packing densities less than 35%. Post-processing was required to achieve sufficient Density prior to firing. The slurry-based 3DP process has been developed to overcome the difficulties of spreading fine submicron powder and also to enable layers as thin as 10 J.lm to be deposited. This paper discusses the slurry-based 3DP process and initial results with different ceramic materials systems. The process is sufficiently generic to be adapted to new materials systems. Our preliminary experiments have been performed on two types of ceramic materials, high purity alumina (several grades of Ceralox HPA) and sintered silicon nitride compositions (HC Stark MIl, 6 wt. % Ah03, 6 wt. % Y203). Firing conditions were 1650°C for 1 hr in air for the alumina samples and 1755°C for 1 hr under 2 psig N2 for the silicon nitride. The slurry-based 3DP process The slurry-based 3DP process was developed to fabricate high Green Density components from submicron powders using wet processing techniques. Figure I shows a schematic of the slurry-based 3DP process. The primary difference from the standard 3DP process
Jaroslav Cihlař - One of the best experts on this subject based on the ideXlab platform.
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Laminated alumina/zirconia ceramic composites prepared by electrophoretic deposition
Journal of the European Ceramic Society, 2012Co-Authors: Hynek Hadraba, Daniel Drdlik, Zdenek Chlup, Karel Maca, Ivo Dlouhý, Jaroslav CihlařAbstract:The electrophoretic deposition of alumina and zirconia powders from isopropanolic suspension in the presence of monochloroacetic acid was studied in the constant-current regime. The different levels of electric current during deposition from 250 μA to 48. mA were used. The Green Density of the deposit depends on the current Density and then on the particle velocity during deposition, reaching values from 58% to 61% according to the electric current used. It was found that the lower the Green Density of the Green deposit, the larger the pores. The low Green Density led to low final fired Density and subsequently to the low Vickers hardness HV5 ranging from 2000 to 1650 depending on electric current used. Based on these findings microlaminates having various thickness ratios to achieve different residual stress levels were prepared consisting of alternating layers of alumina and zirconia. © 2011 Elsevier Ltd.
Jason E. Grau - One of the best experts on this subject based on the ideXlab platform.
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High Green Density ceramic components fabricated by the slurry-based 3DP process
Solid Freeform Fabrication Proceedings, 1997Co-Authors: Jason Grau, Jason E. Grau, Scott A. Uhland, Michael J. Cima, Jooho Moon, Emanuel SachsAbstract:The 3DP process has been modified to directly fabricate high Green Density parts using submicron powder. The slurry-based 3DP process deposits the powder bed by spraying a dispersed slurry of the component material onto a piston. Alumina, silicon nitride, and lead zirconate titanate components with Green densities as high as 67% have been fabricated by the slurry-based 3DP process. Solution phase binder systems have proven to be successful for the new process. Substantially improved surface finish over the conventional dry powder-based 3DP process has been demonstrated. Layer heights less than 50 Jlm can be prepared with this process. Thus, the stepped surface topography commonly observed in solid free form parts is substantially reduced.
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High Green Density ceramic components fabricated by the slurry-based 3DP process
1997Co-Authors: Jason E. Grau, Scott A. Uhland, Michael J. Cima, Jooho Moon, Emanuel SachsAbstract:The 3DP process has been modified to directly fabricate high Green Density parts using submicron powder. The slurry-based 3DP process deposits the powder bed by spraying a dispersed slurry of the component material onto a piston. Alumina, silicon nitride, and lead zirconate titanate components with Green densities as high as 67% have been fabricated by the slurry-based 3DP process. Solution phase binder systems have proven to be successful for the new process. Substantially improved surface finish over the conventional dry powder-based 3DP process has been demonstrated. Layer heights less than 50 Jlm can be prepared with this process. Thus, the stepped surface topography commonly observed in solid free form parts is substantially reduced. Introduction Structural ceramic components require fine-grained starting powders and high Green Density in order to achieve near theoretical Density after firing. Wet processing techniques such as slip casting and injection molding are commonly used in ceramic forming processes to produce parts that meet these criteria. Structural ceramic components have been fabricated in the past with 3DP using spray-dried powders. These powders are -50 J.lm agglomerates of submicron powder. Spray-dried powders were easily spread into uniform layers, but printed components had packing densities less than 35%. Post-processing was required to achieve sufficient Density prior to firing. The slurry-based 3DP process has been developed to overcome the difficulties of spreading fine submicron powder and also to enable layers as thin as 10 J.lm to be deposited. This paper discusses the slurry-based 3DP process and initial results with different ceramic materials systems. The process is sufficiently generic to be adapted to new materials systems. Our preliminary experiments have been performed on two types of ceramic materials, high purity alumina (several grades of Ceralox HPA) and sintered silicon nitride compositions (HC Stark MIl, 6 wt. % Ah03, 6 wt. % Y203). Firing conditions were 1650°C for 1 hr in air for the alumina samples and 1755°C for 1 hr under 2 psig N2 for the silicon nitride. The slurry-based 3DP process The slurry-based 3DP process was developed to fabricate high Green Density components from submicron powders using wet processing techniques. Figure I shows a schematic of the slurry-based 3DP process. The primary difference from the standard 3DP process
Hynek Hadraba - One of the best experts on this subject based on the ideXlab platform.
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Laminated alumina/zirconia ceramic composites prepared by electrophoretic deposition
Journal of The European Ceramic Society, 2012Co-Authors: Hynek Hadraba, Daniel Drdlik, Zdenek Chlup, Karel Maca, Ivo Dlouhý, Jaroslav CihlarAbstract:Abstract The electrophoretic deposition of alumina and zirconia powders from isopropanolic suspension in the presence of monochloroacetic acid was studied in the constant-current regime. The different levels of electric current during deposition from 250 μA to 48 mA were used. The Green Density of the deposit depends on the current Density and then on the particle velocity during deposition, reaching values from 58% to 61% according to the electric current used. It was found that the lower the Green Density of the Green deposit, the larger the pores. The low Green Density led to low final fired Density and subsequently to the low Vickers hardness HV5 ranging from 2000 to 1650 depending on electric current used. Based on these findings microlaminates having various thickness ratios to achieve different residual stress levels were prepared consisting of alternating layers of alumina and zirconia.
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Laminated alumina/zirconia ceramic composites prepared by electrophoretic deposition
Journal of the European Ceramic Society, 2012Co-Authors: Hynek Hadraba, Daniel Drdlik, Zdenek Chlup, Karel Maca, Ivo Dlouhý, Jaroslav CihlařAbstract:The electrophoretic deposition of alumina and zirconia powders from isopropanolic suspension in the presence of monochloroacetic acid was studied in the constant-current regime. The different levels of electric current during deposition from 250 μA to 48. mA were used. The Green Density of the deposit depends on the current Density and then on the particle velocity during deposition, reaching values from 58% to 61% according to the electric current used. It was found that the lower the Green Density of the Green deposit, the larger the pores. The low Green Density led to low final fired Density and subsequently to the low Vickers hardness HV5 ranging from 2000 to 1650 depending on electric current used. Based on these findings microlaminates having various thickness ratios to achieve different residual stress levels were prepared consisting of alternating layers of alumina and zirconia. © 2011 Elsevier Ltd.
M Koopman - One of the best experts on this subject based on the ideXlab platform.
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the relationship between the Green Density and as sintered Density of nano tungsten compacts
International Journal of Refractory Metals & Hard Materials, 2015Co-Authors: Xu Wang, Zhigang Zak Fang, M KoopmanAbstract:Abstract Tungsten is a primary candidate material for certain structural applications in future fusion reactors. However, drawbacks associated with these applications include the need for low ductile to brittle transition temperature (DBTT) and significant demands for fracture toughness. A possible solution to these problems is nanostructuring of tungsten (nano-W; grain size 40% relative Density) of compacts for nano tungsten powders made by high-energy milling. This makes the material prone to rapid grain growth; with a grain size well over 100 nm before complete densification, even at 1000 °C. In this work, a high Density Green compaction method for nano-W powders was demonstrated, which can improve Green Density by at least 18% in relative Density. Additionally, the effect of Green Density on the sintering behavior of nano-W was investigated.
