James Sears

Photonic Sintering of Silver Nanoparticles: Comparison of Experiment and Theory

Photonic sintering is a low thermal exposure sintering method developed to sinter nanoparticle thin films. The process involves using a xenon flash lamp to deliver a high intensity, short duration (< 1 ms), pulse of light to the deposited nanoparticles. Photonic sintering was developed by Nanotechnologies (now NovaCentrix) of Austin, Texas, and was first made public in 2006 (Schroder et al., 2006). As photonic sintering is a new technology it is also known as pulsed thermal processing (PTP) (Camm et al., 2006) and intense pulsed light (IPL) sintering (Kim et al., 2009). Conductive thin films composed of nanoparticle depositions, when exposed to a short pulse of high intensity light, are transformed into functional printed circuits. The printed circuits can be tailored for use as flexible circuit boards, RFID tags, flat panel displays (Carter & Sears, 2007), photovoltaics, or smart packaging (Novacentrix, 2009). One of the primary advantages of the method is that the high intensity pulse of light produces minimal damage on low temperature substrates. This allows the nanoparticles to be deposited and cured on a high variety of low temperature substrates such as cloth, paper, and Mylar (Carter & Sears, 2007; Farnsworth, 2009). Another advantage of using photonic curing is the speed at which nanoparticle depositions can be sintered. Rather than spending hours in an oven or programming a laser to follow the deposition path, the photonic curing process can sinter large areas (~ 200 cm2 per 10 cm long lamp) in < 2 ms (Novacentrix 2009).

Laser sintering of silver nano-particle inks deposited by direct write technology

Direct Write Technologies are being used in antennas, engineered structures, sensors, and tissue engineering. Many for the precursors materials used as inks and pastes for the Direct Write technologies are comprised of nano-scale particles (i.e., Ag, Au, Pt). Various formulations are used to carry the nano-particles during the Direct Write processing. The Direct Write processes deliver these inks and pastes to a surface where they are then post processed to form a functional device. Laser sintering is one form of thermal post processing that can be performed on these deposited nano-particles.This paper will report on the results obtained after laser sintering silver nano-particle inks with a 2W frequency doubled Nd:YAG laser. The results are also compared to conventional oven heat sintering. The results are quantified in terms of surface resistivity, bulk resistance, and microstructure.Direct Write Technologies are being used in antennas, engineered structures, sensors, and tissue engineering. Many for the precursors materials used as inks and pastes for the Direct Write technologies are comprised of nano-scale particles (i.e., Ag, Au, Pt). Various formulations are used to carry the nano-particles during the Direct Write processing. The Direct Write processes deliver these inks and pastes to a surface where they are then post processed to form a functional device. Laser sintering is one form of thermal post processing that can be performed on these deposited nano-particles.This paper will report on the results obtained after laser sintering silver nano-particle inks with a 2W frequency doubled Nd:YAG laser. The results are also compared to conventional oven heat sintering. The results are quantified in terms of surface resistivity, bulk resistance, and microstructure.

Thermal Imaging of Laser Powder Deposition for Process Diagnostics

Thermal imaging is an important tool for future developments in Laser Powder Deposition (LPD). Thermal imaging of the LPD process is typically used for the verification of mathematical models describing the process and/or dynamic melt pool control. The research discussed here shows how thermal imaging can be used to improve our understanding of the connection between deposition parameters, thermal gradients, and final part quality. Data gathered from melt pool and bulk-part thermal images were used to correlate deposition parameters to final part quality. The results presented here are for applications in internal barrel cladding and laser brazing.Copyright

Fabricating Devices Using Nano-Particulates with Direct Write Technology

Nano-particulates are being used in conjunction with Direct Write Technologies for fabrication of electronic devices, sensors, and in tissue engineering. The materials being used in Direct Write Technologies predominately are suspensions, solutions or pastes comprised from nano-particulate metals, oxides or organics. This paper will present a comparison of several nano-particle silver inks being evaluated for use by one of these Direct Write Technologies, Maskless Meso-Scale Material Deposition (M3D) being developed by Optomec, Inc., Albuquerque, NM. USA. The silver inks in this case were deposited by the M3D process and then cured by sintering by both oven and by laser. Optical microscopy and Scanning Electron Microscopy (SEM) were used to examine the resultant cured material. The surface resistivity of these deposits was determined as a measure of their quality. A soft magnetic inductor material was also fabricated through a combination of nickel and iron oxide nano-particles. The results obtain with this inductor material are also discussed.

Repair opportunities for aerospace components through laser powder deposition

Laser Powder Deposition (LPD) for component repair and manufacturing offers some unique solutions for Aerospace applications. LPD is a CAD/CAM solid freeform fabrication technology that uses metal powder and laser fusion for repairing or manufacturing of components. Inherent to LPD is the ability to add material for repair or manufacture of critical GTE components with minimal heat affect to the under lying material. Also, due to the nature of LPD, hard coatings can be achieved without heat treatment allowing for repair of heat-treated steels. In some cases LPD repair can be used to replace hard chrome or carburized surfaces. Details of several Aerospace like components that have been repaired and manufactured will be disclosed.Laser Powder Deposition (LPD) for component repair and manufacturing offers some unique solutions for Aerospace applications. LPD is a CAD/CAM solid freeform fabrication technology that uses metal powder and laser fusion for repairing or manufacturing of components. Inherent to LPD is the ability to add material for repair or manufacture of critical GTE components with minimal heat affect to the under lying material. Also, due to the nature of LPD, hard coatings can be achieved without heat treatment allowing for repair of heat-treated steels. In some cases LPD repair can be used to replace hard chrome or carburized surfaces. Details of several Aerospace like components that have been repaired and manufactured will be disclosed.

Hard, Wear Resistant Metal Surfaces for Industrial Applications through Laser Powder Deposition

Most materials produced today are monolithic structures that are heat treated to perform a particular function. Laser Powder Deposition (LPD) is a technology capable of modifying a metallic structure by adding the appropriate material to perform a desired function (e.g., wear and corrosion resistance). LPD offers a unique fabrication technique that allows the use of soft (tough) materials as base structures. Through LPD a hard material can be applied to the base material with little thermal input (minimal dilution and heat-affected-zone {HAZ}), thus providing the function of a heat treatment or other surface modifications (e.g., carburizing, nitriding, thermal spray and electroplating). Several materials (e.g., Stellite 6 &21, 316 SS, 420 SS, M4, Rex 20, Rex 121, 10V, AeroMet 100, CCW+, IN 625 and IN 718) have been deposited on to carbon steel (4140, 4340, 1566, 1018) substrates to provide various functions for a number of industrial applications. These surface modifications have been evaluated through standard wear testing (ASTM G-65), surface hardness (Rc), micro-hardness (vickers), and optical microscopy. The results from these evaluations will be presented along with several industrial application case studies.

Fabrication of Conductors and Inductors by Nano-Particle Deposition through Direct Write Technology

Direct Write Technologies are being utilized in antennas, engineered structures, sensors, and tissue engineering. One form of the Direct Write Technologies is Maskless Mesoscale Material Deposition (M3D) for Optomec, Inc. M3D is a process that uses aerosol formation, transport and deposition. Inks for the M3D utilize nano-particles in suspension for deposition. Several different conductive inks were deposited with M3D and characterized for electrical resistivity and microstructure. Soft magnetic material was formulated as an ink suspension, deposited and characterized. This paper will report on the results obtained after sintering conductive nano-particle inks and soft magnetic material. Sintering was performed with a 2W frequency doubled Nd:YAG CW laser, a conventional muffle furnace and a novel photonic curing method. Depositions of various conductive inks were examined for physical dimensions (width and thickness) and microstructure. A study of the sintering characteristics if these ink was also includ...

Sintering nano-particles on low temperature materials

Direct Writing (or Printing) technologies use nano-particle inks and pastes to build mesoscale-scale devices. The term mesoscale refers to sizes from approximately 10 microns to 1000 microns, and covers the range between geometries deposited with the more conventional thin film and thick film processes. These processes begin with dispensing of liquid molecular precursors or colloidal suspensions of metal, dielectric, ferrite, or resistor nano-powders. The dispensing is accomplished by either controlling an aerosol stream or bead of thick viscous paste to produce features with dimensions as small as 10 microns. In a typical configuration, the substrate is placed on a platen that is attached to a high precision CAD/CAM stages, so that intricate geometries may be produced. Either laser, photonic or furnace thermal treatments is used to process the deposit to the desired state. Application of these technologies to the production of direct write inductors, capacitors, and resistors is presented, along with electrical characterization of these components.Direct Writing (or Printing) technologies use nano-particle inks and pastes to build mesoscale-scale devices. The term mesoscale refers to sizes from approximately 10 microns to 1000 microns, and covers the range between geometries deposited with the more conventional thin film and thick film processes. These processes begin with dispensing of liquid molecular precursors or colloidal suspensions of metal, dielectric, ferrite, or resistor nano-powders. The dispensing is accomplished by either controlling an aerosol stream or bead of thick viscous paste to produce features with dimensions as small as 10 microns. In a typical configuration, the substrate is placed on a platen that is attached to a high precision CAD/CAM stages, so that intricate geometries may be produced. Either laser, photonic or furnace thermal treatments is used to process the deposit to the desired state. Application of these technologies to the production of direct write inductors, capacitors, and resistors is presented, along with ele...

Preliminary Design of a Calorimeter for Experimental Determination of Effective Absorptivity of Metal Substrates During Laser Powder Deposition

A thermal model of the laser powder deposition (LPD) process has been developed and tested. Results obtained from the model, however, are dependent upon the magnitude of the laser energy absorbed during the process. Although spectral absorptivities of metal surfaces are described in literature, during the LPD process, the powder increases the energy delivered to the substrate. There are no published data regarding this affect. Therefore, the SDSM&T Additive Manufacturing Laboratory (AML) is developing a calorimeter to experimentally investigate the affect of the powder on laser energy absorption at the metal substrate. The preliminary design is described in this paper with discussion on measures being taken to increase the accuracy of experimental data.Copyright

Optimization of laser powder deposition for 316L stainless steel

Laser Powder Deposition (LPD) is being developed under a number of programs for fabrication of aircraft structural parts, gas turbine engine component repair, remanufacturing of mis-machined parts, fabrication of tooling and dies, and medical implants. The understanding of the effects of LPD process parameters on material properties has not been fully developed. In this paper, an attempt is made to group the main LPD process parameters (i.e., laser power, linear velocity, layer height, and hatch width) into a term defined as specific energy (energy per unit volume) for 316L stainless steel. A number of depositions have been produced at increasing specific energies. These deposits were sectioned into specimens for mechanical tensile testing and metallurgical analysis. The resultant mechanical properties and microstructures are compared the specific energy used during deposition.Laser Powder Deposition (LPD) is being developed under a number of programs for fabrication of aircraft structural parts, gas turbine engine component repair, remanufacturing of mis-machined parts, fabrication of tooling and dies, and medical implants. The understanding of the effects of LPD process parameters on material properties has not been fully developed. In this paper, an attempt is made to group the main LPD process parameters (i.e., laser power, linear velocity, layer height, and hatch width) into a term defined as specific energy (energy per unit volume) for 316L stainless steel. A number of depositions have been produced at increasing specific energies. These deposits were sectioned into specimens for mechanical tensile testing and metallurgical analysis. The resultant mechanical properties and microstructures are compared the specific energy used during deposition.