Browsing by Subject "SALDVI"
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Item Preparation and Properties of In-Situ Devices Using the SALD and SALDVI Techniques(1998) Crocker, James E.; Sun, Lianchao; Shaw, Leon L.; Marcus, Harris L.One of the many advantages of Selective Area Laser Deposition (SALD) and Selective Area Laser Deposition Vapor Infiltration (SALDVI) is that they can be used to embed in-situ micro-sensors within macro-components. A single-point SiC/C thermocouple sensor embedded within a SiC macro-component and electrically insulated with silicon nitride layers has been demonstrated. In many applications, multi-point sensors within a single component are needed, e.g., in monitoring the temperature gradient and distribution at different positions. In this paper, multi-point thermocouple devices are demonstrated. The macro-component is a SiC bulk shape made by infiltrating vapor deposited silicon carbide into a silicon carbide powder bed using the SALDVI technique. Multiple SiC/C thermocouples are embedded in-situ in the SiC bulk shape using the SALD technique. The transient and steady state responses ofthe embedded thermocouples are compared to reference thermocouples probing the surfaces of the bulk shape.Item SALDVI Optimization for the Tetramethylsilane - Silicon Carbide System(1997) Crocker, James E.; Jakubenas, Kevin J.; Harrison, Shay; Shaw, Leon L.; Marcus, Harris L.Selective Area Laser Deposition Vapor Infiltration (SALDVI) ofsilicon carbide powder infiltrated with silicon carbide deposited from tetramethylsilane (TMS) was studied. The effects of deposition time, temperature, and gas precursor pressure are discussed. The discussion centers on the efforts to properly balance these parameters to produce multi-layered shapes with structural integrity, particularly for use as the matrix material for shapes containing embedded devices. This includes optimizing scan speed, deposition temperature, and gas pressure to maximize infiltration to increase density and layer to layer bonding, and minimize excessive deposition to maintain critical dimensions. Initial powder properties are also optimized to minimize bulk motion in the powder bed during deposition, which was observed and identified as a mechanism that reduces inter-layer bonding.Item Silicon Carbide Shapes By Selected Area Laser Deposition Vapor Infiltration(1994) Birmingham, B.R.; Tompkins, J.V.; Marcus, H.L.Selected Area Laser Deposition Vapor Infiltration (SALDVI) is a unique combination ofselected area laser deposition, chemical vapor infiltration and layered powder handling techniques that can be used to fabricate silicon carbide (SiC)/SiC composite shapes. This paper discusses a SALDVI process under investigation which selectively infiltrates SiC powder with SiC generated by decomposition of a gas precursor under a scanned laser beam. A general description of the process, including some of its inherent advantages is presented. Experimental results which explore beam interaction, powder size and infiltration time effects are also presented.