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A series of 20 and 100 nm Fe53Pt47 thin films sputter-deposited onto Si substrates have been thermally annealed using a pulsed thermal plasma arc lamp. A series of one, three or five pulses were applied to the thin films with widths of either 50 or 100 ms. The microstructure and magnetic properties of these annealed Fe53Pt47 films are discussed according to the various annealing conditions and A1 to L10 phase transformation. Upon pulse annealing, the average in-plane grain size of 15 nm (nearly equivalent for both film thicknesses) was observed to increase to values near 20 nm. In general, increasing the pulse width or number of pulses increased the L10 order parameter, tetragonality of the c/a ratio and coercivity of the specimen. The exception to this trend was for five pulses at 100 ms for both film thicknesses, which indicated a reduction of the order parameter and coercivity. This reduction is believed to be a result of the interdiffusion of Fe and Pt into the Si substrate and the formation of iron oxide clusters in the grain boundaries characterized by atom probe tomography.

Pulse thermal processing (PTP) of FePt nanoparticle films was studied using a high density infrared (HDI) plasma arc lamp. FePt nanoparticle films on silicon substrates were processed using 0.25- second infrared (IR) pulses. The processing was aimed at reaching a peak target temperature for multiple pulses of 550 C. Numerical simulations of the heat transfer for the PTP were performed to determine the operating power levels for the plasma arc lamp. Infrared measurements were conducted to obtain experimental data for the surface temperature of the FePt nanofilm. Parameters needed for the heat-transfer model were identified based on the experimental temperature results. Following the model validation, several numerical simulations were performed to estimate the power levels. It was shown that the FePt nanoparticle films were successfully processed using the power levels provided by the heat-transfer analysis.

Sputter-deposited, equiatomic PtMn thin films have application in giant magnetoresistive spin valves, tunneling magnetoresistive spin valves, and magnetic random access memory. However, the as-deposited films are found to be a disordered A1 phase in a paramagnetic state rather than an antiferromagnetic phase with L10 structure, which is needed for device operation. Therefore, a postannealing step is required to induce the phase transformation from the asdeposited A1 face-centered-cubic phase to the antiferromagnetic L10 phase. The A1 to L10 metastable transformation was studied by x-ray diffraction and differential-scanning calorimetry. An exothermic transformation enthalpy of −12.1 kJ/mol of atoms was determined. The transformation kinetics were simulated using the Johnson-Mehl-Avrami analysis.

Pulse-thermal processing (PTP) based on high-density plasma arc lamp technology has been utilized to crystallize melt-spun NdFeB-based amorphous ribbons to form magnetic nanocomposites consisting of Nd2Fe14B and α-Fephases. After applying suitable pulses, the NdFeB-based ribbons were developed with hard magnetic properties. The highest coercivity can be obtained for ribbons with a thickness of 40 μm after PTP treatments consisting of a 400 A pulse for 0.25 s for ten times. The correlation between PTP parameters and magnetic properties indicates that PTP is an effective approach to control the structure and properties of nanostructured magnetic materials. Transmission-electorn microscopy analysis revealed that the observed decoupling between the hard and the soft phases is related to large grain size in the samples, which is in turn related to different heating conditions in different regions of samples.

The effect of pulsed-thermal-processing with high-density plasma arc heating is discussed for 20 nm thick nanocrystalline FePt thin films. The dependence of the A1→L10 phase transformation on pulsed time and radiant energy of the pulse is quantified through x-ray diffraction and alternating gradient magnetometry. For 100 ms and 250 ms pulse widths, the phase transformation was observed. Higher radiant energy densities resulted in a larger measured coercivity associated with the L10 phase.

Oak Ridge National Laboratory has developed a unique rapid heating capability utilising a high density infrared (HDI) radiant plasma arc lamp. Power densities ≤3.5 W cm-2 are achievable over an area 35 x 3.175 cm. The power output of the lamp is continuously variable over a range from 1.5% to 100% of available power, and power changes can occur in

Many biomaterials are being developed to repair or replace articular cartilage. One of these materials, a poly(vinyl-alcohol) cryogel (PVA-c) may exhibit the mechanical properties required to withstand the harsh environment of diarthrodial joints. To better understand how PVA-c friction is affected by different variables employed in bench top testing to simulate joint conditions, a six-factor, two-level fractional–factorial experiment was developed. Factors included temperature, lubricant, material stiffness, load, sliding speed, and surface roughness. Static and dynamic friction were found to depend significantly on material stiffness and roughness, increasing as material stiffness and roughness increased. Dynamic friction was also inversely proportional to sliding speed. Overall static and dynamic friction for all variables was 0.285±0.091 and 0.143±0.066 (average±S.D.), respectively. Material deformation and other factors may have contributed to the higher than expected friction levels. Frictional behavior of this PVA-c against stainless steel does not follow Amonton’s friction law, nor does it follow friction models based on repulsion and adsorption theories.

A new high density infrared based coating process has been developed to produce wear resistant coatings on AISI 4340 steel substrates that are of commercial interest. The process combines infrared heating, with power densities up to 35 MW m -2, with room temperature precursor spray deposition processes to rapidly form wear resistant coatings. Here, the process is demonstrated using a 20 vol.-%WC reinforced coating in a Ni-11 wt-%P binder on a AISI 4340 steel substrate, to produce a smooth, high density, 10 μm thick coating with minimal degradation of the WC reinforcement or base steel and a hardness seven times greater than that of the substrate.

The stereographic scanning electron microscopy (SEM) imaging was used to investigate the wear mechanism in wire electrical discharge machining (EDM) truing of metal bond diamond wheels for ceramic grinding. A piece of the grinding wheel was removed after truing and grinding to enable the examination of wheel surface and measurement of diamond protrusion heights using a SEM and stereographic imaging software. The stereographic SEM imaging method was calibrated by comparing with the profilometer measurement results. On the wheel surface after wire EDM truing and before grinding, some diamond grain protruding heights were measured in the 32 μm level. Comparing to the 54 μm average size of the diamond grain, this indicated that over half of the diamond was exposed. During the wire EDM process, electrical sparks occur between the metal bond and EDM wire, which leaves the diamond protruded in the gap between the wire electrode and wheel. These protruding diamond grains with weak bond to the wheel were fractured under a light grinding condition. After heavy grinding, the diamond protrusion heights were estimated in the 5–15 μm range above the wear flat. A cavity created by grinding debris erosion wear of the wheel bond could be identified around the diamond grain.

Covering a light-emitting diode (LED) with quantum dots (QDs) can produce a broad spectrum of white light. However, current techniques for applying QDs to LEDs suffer from a high density of defects and a non-uniform distribution of QDs, which respec-tively diminish the efficiency and quality of emitted light. Oak Ridge National Laboratory (ORNL) has the unique capability to thermally anneal QD structures at extremely high power densities for very short durations. This process, called pulse thermal proc-essing (PTP), reduces the number of point defects while main-taining the size and shape of the original QD nanostructure. Therefore, the efficiency of the QD wavelength conversion layer is improved without altering the emission spectrum defined by the size distribution of the quantum dot nanoparticles. The cur-rent research uses a thermal model to predict annealing tempera-tures during PTP and demonstrates up to a 300% increase in pho-toluminescence for QDs on passive substrates

A high silicon (Si)-containing aluminum–silicon (Al–Si) alloy surface weld overlay, deposited on 319 Al alloys, has been developed at Oak Ridge National Laboratory (ORNL) in order to improve surface-dependent properties, like resistance to wear. The overlay deposition process relies on standard techniques for Al manufacturing, therefore no unusual equipment is required. Microscopic examination of the high Si Al–Si weld overlays show a fine eutectic microstructure containing large Si particles, with the overall microstructure characteristic of a hypereutectic Al–Si alloy, similar to 390 Al alloy. The deposition process is versatile enough to be able to place the overlay in critical areas where high wear resistance is needed, thus reducing the overall cost of a component. In order to quantify the wear resistance of the high Si Al–Si overlays, they have been evaluated alongside 390 Al alloy which exhibits high wear resistance. Pin-on-disk (POD) wear tests have been performed on heat-treated (HT) and non-heat-treated specimens consisting of the high Si Al–Si overlays deposited on 319 Al alloy, bulk 390 Al alloys, and bulk 319 Al alloys. The high Si Al–Si weld overlay shows potential as a replacement of bulk 390 Al alloy for applications requiring high wear resistance.

A novel process has been developed at Oak Ridge National Laboratory for the production of high silicon (Si) containing aluminum–silicon (Al–Si) alloy weld overlay on Al alloys. The main purpose of the overlay is to improve the wear resistance of the underlying alloy. The process is versatile enough to place the overlay only in critical areas, thus, greatly reducing the cost of a component. Instead of manufacturing a component from expensive high Si content 390 Al alloy, the component could be manufactured from an inexpensive alloy, such as 319 Al alloy, and the high Si, Al–Si alloy overlay could be placed in essential areas where high wear resistance was required. Test specimens comprised of the high Si, Al–Si alloy overlays on 319 Al alloy have been processed to mimic the wear resistance of bulk 390 Al alloys. Pin-on-disk wear tests have been performed, following ASTM standards, to quantify the wear resistance of the high Si, Al–Si alloy overlay with that of bulk 390 Al alloy. Wear tests have also been p...

The nanotribological performance of Ti–B–N protective coatings, 500 nm thick, have been studied in the range of 0–38.5 at.% N. A correlation was established amongst the chemical state, structure, mechanical properties, and nanowear resistance as a function of atomic percent nitrogen. The mechanical properties, elastic modulus and hardness, of the films were tested using a Hysitron Triboscope nanomechanical test instrument. The nanotribological performance of the films was evaluated using a Nanoindenter II with scratch capability. Single and reciprocating nanowear scratches, 10 μm in length, were performed at normal loads ranging from 50 to 750 μN. An atomic force microscope (AFM) was utilized to characterize the nanowear tracks with respect to depth and amount of plowing of material. The AFM images revealed that the reciprocating nanowear test caused grooving of the films with little to no material removal. Chemical and structural information was obtained by X-ray photoelectron spectroscopy (XPS) and X-ray diffraction. Increasing N content correlated with increasing number of B–N bonds, structural disorder, and decreasing hardness, modulus, and wear resistance.

Thin films (500 nm) of Ti–B–N have been produced by d.c. magnetron sputtering from a TiB2 target in various Ar+N2 gas mixtures. The atomic concentration of nitrogen in the films varies between 0 and 38 at.%. The ratio of boron to titanium in the films is fixed by the relative concentration of these two elements in the TiB2 sputtering target. Bonds of B–N, B–Ti, Ti–N and Ti–B are observed in the B 1s and the Ti 2p spectra. The change of shape observed in the N 1s spectra led to the conclusion that at low nitrogen concentration the nitrogen atoms are preferentially bonded with titanium atoms, in good agreement with thermodynamical data. By using quantitative information from the B 1s, Ti 2p and N 1s curve fittings, the formation of a film containing three separate phases (TiN, BN and TiB2) is discussed. Copyright © 2000 John Wiley & Sons, Ltd.

Further insight into processing-structure-property relationships have been carried out for existing and candidate carbon-based protective overcoats used in the magnetic recording industry. Specifically, 5 nm thick amorphous diamond-like carbon (a:C) and nitrogenated diamond-like carbon (a:CNx) overcoats were deposited by low deposition rate sputtering onto a thin film disk consisting of either CoCrPt/CrV/NiP/AlMg or CoCrPt/CrV/glass. The wear durability and frictional behavior of these hard disks were ascertained using a recently developed depth sensing reciprocating nanoscratch test. It was determined that the CN0.14/CoCrPt/CrV/glass disk exhibited the most wear resistance, least amount of plastic deformation, and lowest kinetic friction coefficient after the last wear event. Core level x-ray photoelectron spectroscopy (XPS) results of sputter cleaned overcoats indicated that nitrogen up to 14 at. % incorporated into the amorphous network resulted in these improvements near the overcoat/magnetic layer in...

Pulse thermal processing (PTP) has the capability of processing thin-films and nanoparticles over broad areas utilizing high-density infrared plasma arc lamp technology. Heating rates reaching 600,000°C/s, which is orders of magnitude larger than current state-of-the-art rapid thermal annealing systems, are possible that allow controlled diffusion on the nanoscale. The ability to control heating at these levels permits processing thin-films and nanoparticles on temperature-sensitive substrates such as polymers. The PTP technique has been used to crystallize sputtered amorphous silicon thin-films on sapphire substrates.

Materials for a CdTe solar cell (ITO/CdS/CdTe/Cu/Pt) were sputtered at room temperature onto kapton, then transformed from resistive layers into a working solar cell by Pulse Thermal Processing (PTP), a novel radiant heat treatment developed at Oak Ridge National Laboratory (ORNL). Unlike conventional device fabrication approaches, the solar cell was a complete device, front-to-back contact, prior to heat treatment. In this proof-of-concept approach, the I-V curves for the as-deposited sputtered materials demonstrate little measurable photovoltaic (PV) activity, but achieved a V oc of 634 mV after PTP. Based on process simulations, it's estimated that the material/device transformation occurred in under 30 ms, while maintaining the kapton substate at temperatures below 250 °C.

Ultra-thin nitrogenated carbon overcoats have attractive tribological properties that make them favourable for protective coatings for rigid magnetic disks. In this study the influence of the overcoat nitrogen content and thickness on the tribological performance, assessed by nanowear tests, was evaluated. The nitrogenated carbon overcoats, with thicknesses ranging from 5 to 10 nm, were deposited on 15 nm thick layers of CoCrPt media.

The need for maintaining a lower specific engine oil temperature is essential in enhancing the longevity of the oil and of the engine and its components. By decreasing the engine oil temperature the oil is able to perform its job more efficiently. It is proposed to use the carbon foam, with its exceptional thermal management capabilities, to aid in reducing and stabilizing the engine oil temperature during steady state operation. Also, it is possible to use the carbon foam to heat the engine oil during startup to reduce emissions and possibly engine wear. The mesophase pitch derived carbon foam, developed at Oak Ridge National Laboratory, is a material that offers excellent thermal management capability. The foam has an open cell structure (0.98 fraction open porosity) with graphitic ligaments aligned parallel to the cell walls. The alignment of the graphitic ligaments in a three dimensional array gives the foam homogeneous thermal properties, unlike graphite fibers. The bulk thermal conductivity of the foam has been measured to be 175 W/m{center_dot}K, placing it on the level of 6061 aluminum, which has a bulk thermal conductivity of 180 W/m{center_dot}K. Copper has a bulk thermal conductivity over two times higher, at 400 W/m{center_dot}K. The proposedmore » research will entail using the carbon foam, with its excellent thermal management capabilities, as a cooling and heating medium for engine oil, or in other words an oil temperature regulator. The foam will aid in maintaining a specific oil temperature during steady state operation and in heating of the engine oil at startup. Being able to maintain a consistent oil temperature will ensure better operation of engine oil, by extending the life of the oil and engine. All Parties will conduct research efforts in order to determine the best utilization of the carbon foam in managing engine oil temperatures.« less

Pulse Thermal Processing (PTP) using a High Density Infrared (HDI) Plasma Arc Lamp has been investigated as an enabling manufacturing tool for processing nanomaterials and thin-films. HDI is a single source lamp that offers unique capabilities of processing broad areas with power densities approaching those of a laser. The extremely high radiant energies delivered by the plasma arc lamp provides heating rates approaching 600, 000°C/s through a single pulse on a millisecond time frame, thus allowing controlled diffusion on nano-meter scale. The ability to design the functionality of nanomaterials offers tremendous potential to exploit this technology for a wide range of applications based on nanotechnology. This present article discusses application of PTP using high-density plasma arc lamp to perform; a) phase transformation in FePt nanoparticle system for magnetic media applications, and b) crystallization of amorphous Si (a-Si) for photovoltaic and thin-film transistor (TFT) applications.

A natural gas engine-driven heat pump was outfitted with a graphite foam radiator to demonstrate its thermal efficiency and compare it with that of a conventional radiator. A sequence of tests was performed with the graphite foam radiator operating in series with the standard aluminum radiator. Most aluminum air-to-water radiators exhibit an overall heat transfer coefficient up to 100 W/(m2 ·K). Laboratory experiments have demonstrated that a graphite foam radiator can achieve an overall heat transfer coefficient up to an order of magnitude larger. The mesophase pitch derived graphite foam is a material that offers excellent thermal management capability. The foam has an accessible surface area of 4 m2 /g and an open cell structure with graphitic ligaments aligned parallel to the cell walls, giving it an overall bulk thermal conductivity of up to 175 W/(m·K). The bulk thermal conductivity of aluminum is 180 W/(m·K). The density of the graphite foam is a fifth of that of aluminum and its thermal diffusivity is three times greater than aluminum. These properties allow the graphite foam to be utilized in radiator, or any other heat exchanger, designs that are more efficient than conventional radiators. A graphite foam radiator designed to reject a given amount of heat will be smaller in size, weigh less, require less cooling air, and be quicker at removing heat than a conventional aluminum radiator.Copyright © 2002 by ASME

Approximately two thirds of the world's energy consumption is wasted as heat. In an attempt to reduce heat losses, heat exchangers are utilized to recover some of the energy. A unique graphite foam developed at the Oak Ridge National Laboratory (ORNL) and licensed to Poco Graphite, Inc., promises to allow for novel, more efficient heat exchanger designs. This graphite foam, Figure 1, has a density between 0.2 and 0.6 g/cm 3 and a bulk thermal conductivity between 40 and 187 W/m{center_dot}K. Because the foam has a very accessible surface area (> 4 m 2 /g) and is open celled, the overall heat transfer coefficients of foam-based heat exchangers can be up to two orders of magnitude greater than conventional heat exchangers. As a result, foam-based heat exchangers could be dramatically smaller and lighter.

In this investigation, the wear durability of existing and candidate protective overcoats and substrates was examined. Specifically, 5 nm thick diamond-like carbon (DLC) and nitrogenated diamond-like carbon (N-DLC) overcoats were deposited by sputtering onto glass, glass-ceramic, and NiP/AlMg substrates. The magnetic medium was a 15 nm thick layer of CoCrPt deposited on a 50 nm thick underlayer of CrV. The wear resistance of the hard disks was determined by a recently developed depth sensing reciprocating scratch test using the Nano Indenter© II. During the scratch tests, a constant normal load of 30 jtN was maintained at an indenter velocity of 2μm/sec. It was found the N-DLC/CoCrPt/CrV/glass disk exhibited the most wear resistance and least amount of plastic deformation after the last wear event. Conversely, the NDLC/CoCrPt/CrV/NiP/AiMg disk displayed the least wear resistance even though the magnitude of the elastic recovery was the greatest. This amount of recovery was influenced by the high elastic modulus of the NiP/AIMg substrate. Consequently, the scratch test failed to isolate the intrinsic properties of the overcoat, however it provided a very powerful means of quantitatively assessing the overall response of the whole magnetic disk. This is more relevant since it simulates the response the disks see in performance. In addition, a discrete amount of nitrogen up to 14 atomic % incorporated into the amorphous network resulted in an increase in overcoat durability compared to the DLC overcoat. This was attributed to an increase in the XPS determined number of N-sp3 C bonded sites in a predominantly N-sp2 C bonded matrix. However, with increasing nitrogen concentrations ≥18%, the film structure was weakened due to the micro-Raman spectroscopy determined formation of terminated sites in the amorphous carbon network since nitrogen failed to connect the sp2 domains within the network.

The energy distribution and temperature evolution within paintlike systems that are exposed to spectral radiant energy were studied. A complete set of material properties was derived and discussed. Infrared measurements were conducted to obtain experimental data for the temperature in the paint film. The heat flux due to the incident radiation from the plasma arc lamp was measured using a heat flux sensor with a very short response time. A radiative transport model based on spectral four-flux radiation transport equations has been developed for multilayered and semitransparent material systems. Comparisons between the computed and experimental results for temperature show that the energy transport model yields accurate results for a black painted substrate.

Bipolar doping in wide bandgap semiconductors is difficult to achieve under equilibrium conditions because of the spontaneous formation of compensating defects and unfavorable energetics for dopant substitution. In this work, we explored the use of rapid pulse thermal processing for activating nitrogen dopants into acceptor states in ZnO. Low-temperature photoluminescence spectra revealed both acceptor-bound exciton (AX0) and donor-acceptor pair emissions, which present direct evidence for acceptors generated after pulse thermal processing of nitrogen-doped ZnO. This work suggests that pulse thermal processing is potentially an effective method for p-type doping of ZnO.

The disordered face-centered-cubic A1 to the chemical ordered face-centered-tetragonal L10 phase transformation of chemically synthesized magnetic FePt nanoparticles has been studied in the millisecond regime using a pulsed high-density plasma arc light source. Under select annealing conditions, relatively high magnetic coercivities (Hc) and anisotropies (Hk) of FePt nanoparticles were obtained with the millisecond pulse processing without significant sintering of the nanoparticles.