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Stephen C. Danforth - One of the best experts on this subject based on the ideXlab platform.
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Powder Processing, Rheology, and Mechanical Properties of Feedstock for Fused Deposition of Si3N4 Ceramics
Journal of the American Ceramic Society, 2004Co-Authors: Sriram Rangarajan, N. Venkataraman, Ahmad Safari, Stephen C. DanforthAbstract:Fused deposition of ceramics (FDC) is a technique in which green parts are fabricated directly from CAD designs. The Feedstock for FDC is a 1.778 mm diameter filament that requires a low viscosity and high column strength. This study explores the powder processing science, as well as the rheological and mechanical properties required for a successful FDC Feedstock Material. GS44 Si3N4 powders were dispersed in RU9 binder using oleyl alcohol (OA). The viscosity of the RU9/OA/Si3N4 mixture was measured as a function of temperature, solids loading, and OA concentration. The mechanical properties of the filament Feedstock were evaluated in compression to establish FDC process limits. The Feedstock Material shows a shear thinning behavior with OA acting mainly as a plasticizer. The viscosity of GS44-filled RU9 decreases with temperature, and increases with solids content. At 185°C and 55 vol% loading, the viscosity was found to be in the range of 49–7 Pa·s for a corresponding shear rate of 70–1128 s−1. This was sufficiently low for FDC. Based on pressure requirements for FDC extrusion (ΔP), and maximum sustainable stress without buckling by the filament (σE), it has been found that for successful FDC of RU955, 1.1ΔP < σE.
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Feedstock Material property process relationships in fused deposition of ceramics fdc
Rapid Prototyping Journal, 2000Co-Authors: N. Venkataraman, M. J. Matthewson, Noshir A Langrana, Stephen C. Danforth, Ahmad Safari, Sriram Rangarajan, B. Harper, Selçuk Güçeri, Atif M. YardimciAbstract:Fused deposition of ceramics (FDC) is a solid freeform fabrication technique based on extrusion of highly loaded polymer systems. The process utilizes particle loaded thermoplastic binder Feedstock in the form of a filament. The filament acts as both the piston driving the extrusion and also the Feedstock being deposited. Filaments can fail during FDC via buckling, when the extrusion pressure needed is higher than the critical buckling load that the filament can support. Compressive elastic modulus determines the load carrying ability of the filament and the viscosity determines the resistance to extrusion (or extrusion pressure). A methodology for characterizing the compressive mechanical properties of FDC filament Feedstocks has been developed. It was found that Feedstock Materials with a ratio (E/ηa) greater than a critical value (3×105 to 5×105 s‐1) do not buckle during FDC while those with a ratio less than this range buckle.
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Feedstock Material property – process relationships in fused deposition of ceramics (FDC)
Rapid Prototyping Journal, 2000Co-Authors: N. Venkataraman, M. J. Matthewson, Noshir A Langrana, Stephen C. Danforth, Ahmad Safari, Sriram Rangarajan, B. Harper, Selçuk Güçeri, Atif M. YardimciAbstract:Fused deposition of ceramics (FDC) is a solid freeform fabrication technique based on extrusion of highly loaded polymer systems. The process utilizes particle loaded thermoplastic binder Feedstock in the form of a filament. The filament acts as both the piston driving the extrusion and also the Feedstock being deposited. Filaments can fail during FDC via buckling, when the extrusion pressure needed is higher than the critical buckling load that the filament can support. Compressive elastic modulus determines the load carrying ability of the filament and the viscosity determines the resistance to extrusion (or extrusion pressure). A methodology for characterizing the compressive mechanical properties of FDC filament Feedstocks has been developed. It was found that Feedstock Materials with a ratio (E/ηa) greater than a critical value (3×105 to 5×105 s‐1) do not buckle during FDC while those with a ratio less than this range buckle.
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Process-Property-Performance Relationship for Fused Deposition of Ceramics (FDC) Feedstock Materials
MRS Proceedings, 2000Co-Authors: N. Venkataraman, M. J. Matthewson, Ahmad Safari, Sriram Rangarajan, B. Harper, Stephen C. DanforthAbstract:Fused deposition of ceramics (FDC) is an extrusion based layered manufacturing process. It uses a high solids loaded (>50 vol. % ceramic or metal powder) thermoplastic binder in filament form as the Feedstock Material. The filament acts as both the piston driving the extrusion process and the Feedstock Material being deposited in the X-Y direction onto a Z-stage platform. The primary mode of failure of the filament during the FDC process is via buckling. Earlier work has shown that the filament compressive modulus and the Feedstock viscosity control the buckling behavior of the filament Material in FDC. A study was conducted to investigate the effect of particle/polymer interface on the viscosity and compressive modulus of the PZT filled ECG9 system. The relative viscosity of the untreated and the surface treated particle filled systems increases with solids loading. It is found that both of the surface treated Materials (stearic acid and titanate coupling agent) exhibit a lower relative viscosity than the untreated Material. A rheological model (Krieger-Dougherty model) was used to investigate the possible reasons for the decrease in relative viscosity due to the surface treatment of particles. The investigaton showed that the coupling agent acted as a dispersant (increasing value of ϕm) and thereby decreased the viscosity. The stearic acid may act as a dispersant (increasing value of ϕm) and as a lubricant (decreasing value of K E ). The compressive modulus of all the different systems studied showed an increase with solids loading. A generalized Nielsen model was used to describe the relative modulus vs. solids loading behavior for all the different systems studied. Also, the measured compressive modulus of the filled system was found to be insensitive to the modifications in the particle surface treatment.
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Mechanical Properties of Feedstock Material for Fused Deposition of Ceramics
MRS Proceedings, 1998Co-Authors: N. Venkataraman, T.f. Mcnulty, M. Vidaic, M. J. Matthewson, Sampath Rangarajan, Noshir A Langrana, Ahmad Safari, Stephen C. DanforthAbstract:AbstractA scientific methodology to characterize the critical mechanical properties of Feedstock Material for fused deposition of ceramics has been developed. A detailed discussion of the methodology of mechanical characterization and results for lead zirconate titanate (PZT) fused deposition of ceramics (FDC) Feedstock is presented. The effect of storage time, temperature and crosshead displacement rates on the mechanical properties of the PZT FDC Feedstock was studied. The modulus and the failure stress increase with displacement rate. The modulus and failure stress decrease with temperature indicating the necessity for cooling filaments prior to entrance to liquefier. The modulus also decreases with storage time in 50% RH while failure strain increases with storage time in 50% RH.
N. Venkataraman - One of the best experts on this subject based on the ideXlab platform.
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Powder Processing, Rheology, and Mechanical Properties of Feedstock for Fused Deposition of Si3N4 Ceramics
Journal of the American Ceramic Society, 2004Co-Authors: Sriram Rangarajan, N. Venkataraman, Ahmad Safari, Stephen C. DanforthAbstract:Fused deposition of ceramics (FDC) is a technique in which green parts are fabricated directly from CAD designs. The Feedstock for FDC is a 1.778 mm diameter filament that requires a low viscosity and high column strength. This study explores the powder processing science, as well as the rheological and mechanical properties required for a successful FDC Feedstock Material. GS44 Si3N4 powders were dispersed in RU9 binder using oleyl alcohol (OA). The viscosity of the RU9/OA/Si3N4 mixture was measured as a function of temperature, solids loading, and OA concentration. The mechanical properties of the filament Feedstock were evaluated in compression to establish FDC process limits. The Feedstock Material shows a shear thinning behavior with OA acting mainly as a plasticizer. The viscosity of GS44-filled RU9 decreases with temperature, and increases with solids content. At 185°C and 55 vol% loading, the viscosity was found to be in the range of 49–7 Pa·s for a corresponding shear rate of 70–1128 s−1. This was sufficiently low for FDC. Based on pressure requirements for FDC extrusion (ΔP), and maximum sustainable stress without buckling by the filament (σE), it has been found that for successful FDC of RU955, 1.1ΔP < σE.
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Feedstock Material property process relationships in fused deposition of ceramics fdc
Rapid Prototyping Journal, 2000Co-Authors: N. Venkataraman, M. J. Matthewson, Noshir A Langrana, Stephen C. Danforth, Ahmad Safari, Sriram Rangarajan, B. Harper, Selçuk Güçeri, Atif M. YardimciAbstract:Fused deposition of ceramics (FDC) is a solid freeform fabrication technique based on extrusion of highly loaded polymer systems. The process utilizes particle loaded thermoplastic binder Feedstock in the form of a filament. The filament acts as both the piston driving the extrusion and also the Feedstock being deposited. Filaments can fail during FDC via buckling, when the extrusion pressure needed is higher than the critical buckling load that the filament can support. Compressive elastic modulus determines the load carrying ability of the filament and the viscosity determines the resistance to extrusion (or extrusion pressure). A methodology for characterizing the compressive mechanical properties of FDC filament Feedstocks has been developed. It was found that Feedstock Materials with a ratio (E/ηa) greater than a critical value (3×105 to 5×105 s‐1) do not buckle during FDC while those with a ratio less than this range buckle.
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Feedstock Material property – process relationships in fused deposition of ceramics (FDC)
Rapid Prototyping Journal, 2000Co-Authors: N. Venkataraman, M. J. Matthewson, Noshir A Langrana, Stephen C. Danforth, Ahmad Safari, Sriram Rangarajan, B. Harper, Selçuk Güçeri, Atif M. YardimciAbstract:Fused deposition of ceramics (FDC) is a solid freeform fabrication technique based on extrusion of highly loaded polymer systems. The process utilizes particle loaded thermoplastic binder Feedstock in the form of a filament. The filament acts as both the piston driving the extrusion and also the Feedstock being deposited. Filaments can fail during FDC via buckling, when the extrusion pressure needed is higher than the critical buckling load that the filament can support. Compressive elastic modulus determines the load carrying ability of the filament and the viscosity determines the resistance to extrusion (or extrusion pressure). A methodology for characterizing the compressive mechanical properties of FDC filament Feedstocks has been developed. It was found that Feedstock Materials with a ratio (E/ηa) greater than a critical value (3×105 to 5×105 s‐1) do not buckle during FDC while those with a ratio less than this range buckle.
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Process-Property-Performance Relationship for Fused Deposition of Ceramics (FDC) Feedstock Materials
MRS Proceedings, 2000Co-Authors: N. Venkataraman, M. J. Matthewson, Ahmad Safari, Sriram Rangarajan, B. Harper, Stephen C. DanforthAbstract:Fused deposition of ceramics (FDC) is an extrusion based layered manufacturing process. It uses a high solids loaded (>50 vol. % ceramic or metal powder) thermoplastic binder in filament form as the Feedstock Material. The filament acts as both the piston driving the extrusion process and the Feedstock Material being deposited in the X-Y direction onto a Z-stage platform. The primary mode of failure of the filament during the FDC process is via buckling. Earlier work has shown that the filament compressive modulus and the Feedstock viscosity control the buckling behavior of the filament Material in FDC. A study was conducted to investigate the effect of particle/polymer interface on the viscosity and compressive modulus of the PZT filled ECG9 system. The relative viscosity of the untreated and the surface treated particle filled systems increases with solids loading. It is found that both of the surface treated Materials (stearic acid and titanate coupling agent) exhibit a lower relative viscosity than the untreated Material. A rheological model (Krieger-Dougherty model) was used to investigate the possible reasons for the decrease in relative viscosity due to the surface treatment of particles. The investigaton showed that the coupling agent acted as a dispersant (increasing value of ϕm) and thereby decreased the viscosity. The stearic acid may act as a dispersant (increasing value of ϕm) and as a lubricant (decreasing value of K E ). The compressive modulus of all the different systems studied showed an increase with solids loading. A generalized Nielsen model was used to describe the relative modulus vs. solids loading behavior for all the different systems studied. Also, the measured compressive modulus of the filled system was found to be insensitive to the modifications in the particle surface treatment.
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Mechanical Properties of Feedstock Material for Fused Deposition of Ceramics
MRS Proceedings, 1998Co-Authors: N. Venkataraman, T.f. Mcnulty, M. Vidaic, M. J. Matthewson, Sampath Rangarajan, Noshir A Langrana, Ahmad Safari, Stephen C. DanforthAbstract:AbstractA scientific methodology to characterize the critical mechanical properties of Feedstock Material for fused deposition of ceramics has been developed. A detailed discussion of the methodology of mechanical characterization and results for lead zirconate titanate (PZT) fused deposition of ceramics (FDC) Feedstock is presented. The effect of storage time, temperature and crosshead displacement rates on the mechanical properties of the PZT FDC Feedstock was studied. The modulus and the failure stress increase with displacement rate. The modulus and failure stress decrease with temperature indicating the necessity for cooling filaments prior to entrance to liquefier. The modulus also decreases with storage time in 50% RH while failure strain increases with storage time in 50% RH.
E R Weber - One of the best experts on this subject based on the ideXlab platform.
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control of metal impurities in dirty multicrystalline silicon for solar cells
Materials Science and Engineering B-advanced Functional Solid-state Materials, 2006Co-Authors: A A Istratov, Tonio Buonassisi, Matthew D Pickett, Matthias Heuer, E R WeberAbstract:Abstract The rapid growth of the global photovoltaics (PV) industry is increasingly limited by the availability of suitable Si Feedstock Material. Therefore, it is very important to explore new approaches that might allow processing of solar cells with satisfactory energy conversion efficiency based on inexpensive Feedstock Material with less stringent impurity control, i.e., “dirty” silicon. Our detailed studies of the distribution of metal impurity clusters in multicrystalline Si have demonstrated that cells with the same total impurity content can have widely different minority carrier diffusion lengths based on the distribution of the metals, i.e., whether they are dispersed throughout the Material or concentrated in a few, large clusters. Possible approaches to defect engineering of metal clusters in silicon are discussed.
Ahmad Safari - One of the best experts on this subject based on the ideXlab platform.
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Powder Processing, Rheology, and Mechanical Properties of Feedstock for Fused Deposition of Si3N4 Ceramics
Journal of the American Ceramic Society, 2004Co-Authors: Sriram Rangarajan, N. Venkataraman, Ahmad Safari, Stephen C. DanforthAbstract:Fused deposition of ceramics (FDC) is a technique in which green parts are fabricated directly from CAD designs. The Feedstock for FDC is a 1.778 mm diameter filament that requires a low viscosity and high column strength. This study explores the powder processing science, as well as the rheological and mechanical properties required for a successful FDC Feedstock Material. GS44 Si3N4 powders were dispersed in RU9 binder using oleyl alcohol (OA). The viscosity of the RU9/OA/Si3N4 mixture was measured as a function of temperature, solids loading, and OA concentration. The mechanical properties of the filament Feedstock were evaluated in compression to establish FDC process limits. The Feedstock Material shows a shear thinning behavior with OA acting mainly as a plasticizer. The viscosity of GS44-filled RU9 decreases with temperature, and increases with solids content. At 185°C and 55 vol% loading, the viscosity was found to be in the range of 49–7 Pa·s for a corresponding shear rate of 70–1128 s−1. This was sufficiently low for FDC. Based on pressure requirements for FDC extrusion (ΔP), and maximum sustainable stress without buckling by the filament (σE), it has been found that for successful FDC of RU955, 1.1ΔP < σE.
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Feedstock Material property process relationships in fused deposition of ceramics fdc
Rapid Prototyping Journal, 2000Co-Authors: N. Venkataraman, M. J. Matthewson, Noshir A Langrana, Stephen C. Danforth, Ahmad Safari, Sriram Rangarajan, B. Harper, Selçuk Güçeri, Atif M. YardimciAbstract:Fused deposition of ceramics (FDC) is a solid freeform fabrication technique based on extrusion of highly loaded polymer systems. The process utilizes particle loaded thermoplastic binder Feedstock in the form of a filament. The filament acts as both the piston driving the extrusion and also the Feedstock being deposited. Filaments can fail during FDC via buckling, when the extrusion pressure needed is higher than the critical buckling load that the filament can support. Compressive elastic modulus determines the load carrying ability of the filament and the viscosity determines the resistance to extrusion (or extrusion pressure). A methodology for characterizing the compressive mechanical properties of FDC filament Feedstocks has been developed. It was found that Feedstock Materials with a ratio (E/ηa) greater than a critical value (3×105 to 5×105 s‐1) do not buckle during FDC while those with a ratio less than this range buckle.
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Feedstock Material property – process relationships in fused deposition of ceramics (FDC)
Rapid Prototyping Journal, 2000Co-Authors: N. Venkataraman, M. J. Matthewson, Noshir A Langrana, Stephen C. Danforth, Ahmad Safari, Sriram Rangarajan, B. Harper, Selçuk Güçeri, Atif M. YardimciAbstract:Fused deposition of ceramics (FDC) is a solid freeform fabrication technique based on extrusion of highly loaded polymer systems. The process utilizes particle loaded thermoplastic binder Feedstock in the form of a filament. The filament acts as both the piston driving the extrusion and also the Feedstock being deposited. Filaments can fail during FDC via buckling, when the extrusion pressure needed is higher than the critical buckling load that the filament can support. Compressive elastic modulus determines the load carrying ability of the filament and the viscosity determines the resistance to extrusion (or extrusion pressure). A methodology for characterizing the compressive mechanical properties of FDC filament Feedstocks has been developed. It was found that Feedstock Materials with a ratio (E/ηa) greater than a critical value (3×105 to 5×105 s‐1) do not buckle during FDC while those with a ratio less than this range buckle.
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Process-Property-Performance Relationship for Fused Deposition of Ceramics (FDC) Feedstock Materials
MRS Proceedings, 2000Co-Authors: N. Venkataraman, M. J. Matthewson, Ahmad Safari, Sriram Rangarajan, B. Harper, Stephen C. DanforthAbstract:Fused deposition of ceramics (FDC) is an extrusion based layered manufacturing process. It uses a high solids loaded (>50 vol. % ceramic or metal powder) thermoplastic binder in filament form as the Feedstock Material. The filament acts as both the piston driving the extrusion process and the Feedstock Material being deposited in the X-Y direction onto a Z-stage platform. The primary mode of failure of the filament during the FDC process is via buckling. Earlier work has shown that the filament compressive modulus and the Feedstock viscosity control the buckling behavior of the filament Material in FDC. A study was conducted to investigate the effect of particle/polymer interface on the viscosity and compressive modulus of the PZT filled ECG9 system. The relative viscosity of the untreated and the surface treated particle filled systems increases with solids loading. It is found that both of the surface treated Materials (stearic acid and titanate coupling agent) exhibit a lower relative viscosity than the untreated Material. A rheological model (Krieger-Dougherty model) was used to investigate the possible reasons for the decrease in relative viscosity due to the surface treatment of particles. The investigaton showed that the coupling agent acted as a dispersant (increasing value of ϕm) and thereby decreased the viscosity. The stearic acid may act as a dispersant (increasing value of ϕm) and as a lubricant (decreasing value of K E ). The compressive modulus of all the different systems studied showed an increase with solids loading. A generalized Nielsen model was used to describe the relative modulus vs. solids loading behavior for all the different systems studied. Also, the measured compressive modulus of the filled system was found to be insensitive to the modifications in the particle surface treatment.
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Mechanical Properties of Feedstock Material for Fused Deposition of Ceramics
MRS Proceedings, 1998Co-Authors: N. Venkataraman, T.f. Mcnulty, M. Vidaic, M. J. Matthewson, Sampath Rangarajan, Noshir A Langrana, Ahmad Safari, Stephen C. DanforthAbstract:AbstractA scientific methodology to characterize the critical mechanical properties of Feedstock Material for fused deposition of ceramics has been developed. A detailed discussion of the methodology of mechanical characterization and results for lead zirconate titanate (PZT) fused deposition of ceramics (FDC) Feedstock is presented. The effect of storage time, temperature and crosshead displacement rates on the mechanical properties of the PZT FDC Feedstock was studied. The modulus and the failure stress increase with displacement rate. The modulus and failure stress decrease with temperature indicating the necessity for cooling filaments prior to entrance to liquefier. The modulus also decreases with storage time in 50% RH while failure strain increases with storage time in 50% RH.
Traugott E. Fischer - One of the best experts on this subject based on the ideXlab platform.
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Multimodal powders: a new class of Feedstock Material for thermal spraying of hard coatings
Scripta Materialia, 2001Co-Authors: Ganesh Skandan, Ruvee Yao, Bernard H. Kear, Yunfei Qiao, Lucy Liu, Traugott E. FischerAbstract:We are developing a new class of High Velocity Oxy-Fuel (HVOF) thermal spray Feedstock powders, which consist of aggregates of hard ceramic particles that are either mixed or coated with a more readily fusible nanophase binder. Thus, during thermal spraying, the nanostructured Material undergoes rapid melting while the aggregated Material is heated but not necessarily melted. A dense coating is formed when the molten nano-Material fills the available pore spaces between the heated and softened aggregates, providing a strong and tough matrix for the spray deposited Material. Such multimodal coatings combine moderate hardness with exceptional abrasive wear resistance. Characteristics of the multimodal feed powders, along with the structure and properties of the resulting coatings, are described in this paper.
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Multimodal coatings: A new concept in thermal spraying
Journal of Thermal Spray Technology, 2000Co-Authors: Ganesh Skandan, Ruvee Yao, Bernard H. Kear, Yunfei Qiao, Lucy Liu, R. Sadangi, Traugott E. FischerAbstract:Recently, considerable emphasis has been placed on HVOF thermal spraying of nanostructured WC/Co with the intention of achieving high hardness combined with excellent wear resistance. However, depositing dense coatings and simultaneously preventing decarburization has remained a challenge. We have approached the problem by developing a novel Feedstock Material that consists of a mixture of coarse and fine particles of WC/Co. Particles of different sizes have a different response in the combustion flame. The resultant coating is dense and has no decarburized phases. The abrasion wear resistance is at least 50% better than that of a pure coarse-grained WC/Co coating.
