Precision LCVD System Design with Real Time Process Control

A Laser Chemical Vapor Deposition (LCVD) system was designed using a fixed 100 Watt C02 laser focused on a moveable substrate. Temperature and height measurement devices monitor the reaction at the point of deposition to provide feedback for controlling the process. The LCVD system will use rapid prototyping technology to directly fabricate fully threedimensional ceramic, metallic, and composite parts of arbitrary shape. Potential applications include high temperature structures, electronic/photonic devices, and orthopaedic implants.Mechanical Engineerin

Fabrication of Advanced Thermionic Emitters Using Laser Chemical Vapor Deposition-Rapid Prototyping 498

Laser Chemical Vapor Deposition-Rapid Prototyping (LCVD-RP) is a relatively new manufacturing process. Its capabilities are ideally suited for the manufacturing of a type of electron emitter called an integrated-grid thermionic emitter. The integrated-grid thermionic emitter is composed of wagon wheel-like structures of alternating layers of boron nitride and molybdenum on tungsten. The goal of this paper is to determine the feasibility of using LCVDRP technology to manufacture advanced thermionic emitters.Mechanical Engineerin

Heat Transfer Analysis of a Gas-Jet Laser Chemical Vapor Deposition (LCVD) Process 461

This paper describes the development of a computer model used to characterize the heat transfer properties of a gas-jet LCVD process. A commercial software package was used to combine heat transfer finite element analysis with the capabilities of computational fluid dynamic software (CFDS). Such a model is able to account for both conduction and forced convection modes of heat transfer. The maximum substrate temperature was studied as a function of laser power and gas-jet velocity.Mechanical Engineerin

Field-dependent heat transport in the Kondo insulator SmB6 : phonons scattered by magnetic impurities

The thermal conductivity $\kappa$ of the Kondo insulator SmB$_6$ was measured at low temperature, down to 70 mK, in magnetic fields up to 15 T, on single crystals grown using both the floating-zone and the flux methods. The residual linear term $\kappa_0/T$ at $T \to 0$ is found to be zero in all samples, for all magnetic fields, in agreement with previous studies. There is therefore no clear evidence of fermionic heat carriers. In contrast to some prior data, we observe a large enhancement of $\kappa(T)$ with increasing field. The effect of field is anisotropic, depending on the relative orientation of field and heat current (parallel or perpendicular), and with respect to the cubic crystal structure. We interpret our data in terms of heat transport predominantly by phonons, which are scattered by magnetic impurities.Comment: publish versio