Moving Boundary Transport Phenomena in Selective Area Laser Deposition Process

The overall selective area laser deposition process was modeled using the two-layer, three dimensional solid phase heat transfer with the moving boundary condition considered, gas phase mass transfer, and film growth coupled equations. A modified front-tracking finite difference method was used to solve the moving boundary heat conduction in thick deposits. The results correlate with the experimental observations.Mechanical Engineerin

Selective Area Laser Deposition - A Method of Solid Freeform Fabrication

Mechanical Engineerin

Selective Laser Sintering and Reaction Sintering of Ceramic Composites

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.Mechanical Engineerin

Parametric Analysis for Selective Laser Sintering of a Sample Polymer System

Mechanical Engineerin

Catalyst and plasma assisted nucleation and renucleation of gas phase selective laser deposition

A method and apparatus for selectively depositing a layer of material from a gas phase to produce a part comprising a plurality of deposited layers. The apparatus includes a computer controlling a directed energy beam, such as a laser, to direct the laser energy into a chamber substantially containing the gas phase to preferably produce photodecomposition or thermal decomposition of the gas phase and selectively deposit material within the boundaries of the desired cross-sectional regions of the part. For each cross section, the aim of the laser beam is scanned over a target area and the beam is switched on to deposit material within the boundaries of the cross-section. Each subsequent layer is joined to the immediately preceding layer to produce a part comprising a plurality of joined layers. In an alternate embodiment of the present invention, a gas phase is condensed on a surface and a laser beam is used to selectively evaporate, transform, activate or decompose material in each layer. A catalytic environment can be created proximate or upon the target area to ensure that initial nucleation and renucleation layers are receptive to substantially rapid and uniform growth of gas phase material at the target location. The catalyst can be placed on the initial substrate layer and/or upon successive layers as the layers are being deposited on the outer surface of the evolving part.Board of Regents, University of Texas Syste

Method and apparatus for direct use of low pressure vapor from liquid or solid precursors for selected area laser deposition

Methods and apparatus for selectively depositing a layer of material from a gas phase to produce a part comprising a plurality of deposited layers. The apparatus includes a computer controlling a directed energy beam, such as a laser, to direct the laser energy into an unheated chamber substantially containing the gas phase to preferably produce photodecomposition or thermal decomposition of the gas phase and selectively deposit material within the boundaries of the desired cross-sectional regions of the part. At least one component of the gas phase is a vapor which condenses at a temperature above the ambient temperature of the chamber. Each such component can exist at a partial pressure no higher than its equilibrium vapor pressure at the chamber ambient temperature. For each cross section, the aim of the laser beam is scanned over a target area and the beam is switched on to deposit material within the boundaries of the cross-section. Each subsequent layer is joined to the immediately preceding layer to produce a part comprising a plurality of joined layers. A catalytic environment can be created proximate or upon the target area to ensure that initial nucleation and renucleation layers are receptive to substantially rapid and uniform growth of decomposed gas phase material at the target location. The catalyst can be placed on the initial substrate layer and/or upon successive layers as the layers are being deposited on the outer surface of the evolving part.Board of Regents, University of Texas Syste

Use of neighborhood unhomogeneity to detect the edge of hyperspectral spatial stray light region

Since hyperspectral images contain fine spectral information of the target objects, there is continuous demand for the detailed analysis about such images. A somewhat neglected but critically important challenge regarding hyperspectral image is the presence of "spatial stray light" - a phenomenon caused by scattering of photons from target objects. In this study, neighborhood unhomogeneity method is used to detect the edge of spatial stray light region in hyperspectral images. Analyses were conducted on reflectance datasets of standard card, potato leaf, and corn kernels from three inbred lines. By using neighborhood unhomogeneity method, the edge of spatial stray light region could be detected obviously and experimental results show the effectiveness of the proposed method. © 2014 Elsevier GmbH