Material Processing with a High Frequency Millimeter-Wave Source

Lewis, David; Imam, M. Ashraf; Kurihara, Lynn K.; Fliflet, A. W.; Kinkead, A. K.; Miserendino, Scott; Bruce, Ralph W.; Gold, Steven H.; Jung, Anne

doi:10.1081/amp-120018902

Cited by 19 publications

(4 citation statements)

References 5 publications

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“…However, the powder preparation and the sintering conditions must be carefully controlled in order to realize these advantages. Millimeter-wave processing has been shown to be an effective alternative to conventional vacuum furnaces for pressure-free sintering of low-loss oxide ceramic materials [4]. The driving force for this type of sintering is the excess surface energy of the grains.…”

Section: Introductionmentioning

confidence: 99%

Consolidation of polycrystalline yttria powder by MILLIMETER-WAVE sintering for laser host applications

Hornstein¹,

Bruce²,

Fliflet³

et al. 2007

2007 16th IEEE International Pulsed Power Conference

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†We report recent results of an investigation of millimeter-wave processing of yttria (Y 2 O 3 ) for fabrication of transparent, high strength polycrystalline ceramic laser hosts for High Energy Laser (HEL) applications. 1,2 The objective is to produce polycrystalline materials with optical quality comparable to that of a single crystal. It is difficult to produce yttria single crystals because of the phase transformation around 2000°C and the high melting temperature which is over 2400°C. While single crystals have high thermal conductivity and can operate at high powers, they are costly and limited in size and dopant concentration. Significant advantages of polycrystalline materials compared to single crystals, are lower processing temperature, higher gain as a result of higher dopant concentrations, faster and less expensive fabrication, and the possibility of larger devices. Millimeter-wave processing has been proposed as an alternative method to solve the problems of both conventional vacuum sintering and low frequency microwave sintering, such as low heating rates, poor coupling, and unfavorable thermal gradients. A major component of the NRL millimeter-wave processing facility is a 20-kW, continuous-wave (CW), 83-GHz gyrotron oscillator (GYCOM, Ltd.). Translucent yttria has been successfully sintered with millimeter-wave beams with up to 99% theoretical density. A partially transparent yttria ceramic sample has also been achieved using the millimeter-wave sintering process. Several factors impact the quality of the sintered material including the presence of agglomerates, impurities, processing atmosphere, sintering aids, and thermal gradients. Efforts to improve the transparency are in progress.

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Section: Introductionmentioning

confidence: 99%

Consolidation of polycrystalline yttria powder by MILLIMETER-WAVE sintering for laser host applications

Hornstein¹,

Bruce²,

Fliflet³

et al. 2007

2007 16th IEEE International Pulsed Power Conference

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“…45 GHz system for continuous production and processing of nanophase oxides and metals, and an 83 GHz, millimetre-wave beam system for a variety of material processing including sintering, joining, coating and coating removal. [7][8][9][10][11][12][13][14][15][16][17] Both systems have advantages for certain types of materials processing; the advantages of the millimetre-wave beam system in joining operations are particularly significant and the subject of this article.…”

Section: Introductionmentioning

confidence: 99%

Joining of materials with millimetre-wave beam source

Lewis¹,

Bruce²,

Imam³

et al. 2004

Science and Technology of Welding and Joining

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An 83 GHz gyrotron-based, millimetre-wave beam system is being used for a range of material processing. One very promising application of this technology is in joining of ceramic and ceramic composite materials and has unique advantages over competitive techniques. The significant advantage is localisation of heating, with the millimetre-wave beam controlled by reflective optics, permitting inexpensive fixturing and instrumentation and minimising thermal damage to components. Another is the possibility of depositing energy specifically in a narrow joint region, through a guided wave effect. A corollary advantage of the process is the possibility of very rapid thermal cycling during joining, minimising thermal degradation of materials being joined.

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“…Thermal analysis by MMW radiometry methods [1] can be combined with MMW high power gyrotron radiation [2] to enable unique capability to research the thermodynamic properties of materials to extreme temperatures that have not been accessible to real time dynamic studies in the past. In particular, the properties of rocks melts up to the vaporization temperature can be quantitatively studied.…”

Section: Introductionmentioning

confidence: 99%

Millimeter-Wave Heating, Radiometry, and Calorimetry of Granite Rock to Vaporization

Woskov

Michael

2011

J Infrared Milli Terahz Waves

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Abstract:Millimeter-wave (MMW) technologies can provide unique heating and diagnostic capabilities to research the thermal dynamics of materials to extreme temperatures. The MMW properties of rocks in the molten state up to their vaporization temperatures are not well known. Using a 28 GHz gyrotron beam collinear with a 130 GHz radiometry view in a calorimetric chamber, the transitions of granite rock specimens through solid phases, melting, and vaporization were observed, including release of trapped trace gas (< 0.07%). The 28 GHz emissivity of molten granite was observed to be approximately constant at 0.66 ± 0.03 up to vaporization where it increased to 0.70 ± 0.03 at an equilibrated temperature of 2710 ± 120 °C. An analysis of the thermal power balance during a 76 s steady state vaporization time period indicates that the MMW emissivity of the molten granite is larger than in the infrared. The observations support the possibility that MMW thermal ablative penetration into hot crystalline rock formations could be a more practical approach than infrared laser drilling to access deep resources.

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Material Processing with a High Frequency Millimeter-Wave Source

Cited by 19 publications

References 5 publications

Consolidation of polycrystalline yttria powder by MILLIMETER-WAVE sintering for laser host applications

Consolidation of polycrystalline yttria powder by MILLIMETER-WAVE sintering for laser host applications

Joining of materials with millimetre-wave beam source

Millimeter-Wave Heating, Radiometry, and Calorimetry of Granite Rock to Vaporization

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