Browsing by Subject "SLRS"

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Development of a Selective Laser Reaction Sintering Workstation
(1992) Birmingham, B.R.; Tompkins, J.V.; Zong, G.; Marcus, H.L.
The purpose of this paper is to describe the design and operation of a Selective Laser Reaction Sintering workstation developed at The University of Texas. The workstation allows the study of solid freeform fabrication of reaction sintered materials on a research scale. The mechanical and control systems of the workstation are detailed, and Selective Laser Reaction Sintering as a technique is discussed including example material systems that are currently under study.
Development of Nanocomposites for Solid Freeform Fabrication
(1993) Manthiram, A.; Chi, F.; Johnson, F.; Birmingham, B.R.; Marcus, H.L.
Nanocomposites in which the constituents are mixed on a nanorneter scale can provide important advantages in the Selective Laser Sintering (SLS) and Selective Laser Reactive Sintering (SLRS) processes. The larger surface area and grain boundaries in the nanocolnposites compared to that in the conventional microcomposites are expected to enhance the solid state diffusion during laser irradiation as well as during any other subsequent processes. Our strategy is to design and develop nanocomposites in which one nanosize cOlnponent has a lower melting point than the other nanosize component, either of which can serve as the matrix phase. The nanoscale dispersion of the low melting component can aid the sintering process during SLS or SLRS. Nanocomposite powders of AI203-COOx, Ab03-NiO, A1203-CO and A1203-Ni have been synthesized by sol-gel processing and are evaluated by SLS.
Selective Laser Sintering and Reaction Sintering of Ceramic Composites
(1992) Subramanian, Kamatchi; Zong, Guisheng; Marcus, H.L.
Selective Laser Sintering and Reaction Sintering (SLS and SLRS) are used as methods of forming composites and preforms. Al20jAI and SiC/AI were studied as model systems. Ceramic and metallic powders are mixed and locally sintered using SLS and SLRS. Post processing heat treatment was also employed. Wettability and residual stress aspects of this process are discussed.
Solid Freeform Fabrication of Silicon Carbide Shapes by Selective Laser Reaction Sintering (SLRS)
(1993) Birmingham, B.R.; Marcus, H.L.
This paper describes an investigation ofthe production ofsilicon carbide shapes by Selective Laser Reaction Sintering (SLRS). One type ofSLRS process, which combines laser sintering of silicon with acetylene decomposition, is briefly outlined, and the mechanisms important to the process are discussed. A series oftest shapes are made at different acetylene pressures to determine pressure effects on conversion to silicon carbide. X-ray diffraction spectroscopy is used for bulk analysis ofthe shapes, and Auger electron spectroscopy is used for surface analysis. The results indicate that acetylene pressure does have a strong effect on silicon conversion to silicon carbide, and SLRS can be used successfully to make silicon carbide shapes.
Solid Freeform Fabrication of Silicon Nitride Shapes by Selective Laser Reaction Sintering (SLRS)
(1995) Marcus, H.L.; Birmingham, B.R.
SelectiveLaser ReactionSinteringis a variation ofselective laser sintering (SLS) that incorporates anjn~situreaction underthe·scannedbeamtofabricate shapes from materials not directly accessible by traditional SLS. Thispaperclescribesaninvestigation into the production of silicon nitride (Si3N4) shapes by lasersinteringsiliconpowderinanammonia (NH3) atmosphere. The effect of gas pressure and the importance of gas/laserinteractionsarediscussed. Single and multiple layer shapes are fabricated. The material is analyzed by x~ray diffraction spectroscopy (XRDS) for phase content and scanning electron microscopy (SEM) for macrostructure. Data is presented that demonstrates conversion rates from silicon to silicon nitride on the order of 85%.