The measurement of thermal expansion coefficient of tungsten at elevated temperatures

Knibbs, R.H.

doi:10.1088/0022-3735/2/6/311

Cited by 29 publications

(8 citation statements)

References 4 publications

Supporting

Mentioning

Contrasting

Order By: Relevance

“…4. Geometry changes due to thermal expansion can safely be neglected, because W has a very low thermal expansion coefficient of 6 μm m −1 K −1 (46), which results in geometry changes of less than 1%. The samples are also subjected to repeated thermal cycling (i.e., heated to ≃1;200 K for an hour) before allowing to cool to room temperature.…”

Section: Resultsmentioning

confidence: 99%

Enabling high-temperature nanophotonics for energy applications

Yeng

Ghebrebrhan²,

Bermel³

et al. 2012

Proc. Natl. Acad. Sci. U.S.A.

222

181

View full text Add to dashboard Cite

The nascent field of high-temperature nanophotonics could potentially enable many important solid-state energy conversion applications, such as thermophotovoltaic energy generation, selective solar absorption, and selective emission of light. However, special challenges arise when trying to design nanophotonic materials with precisely tailored optical properties that can operate at hightemperatures (>1,100 K). These include proper material selection and purity to prevent melting, evaporation, or chemical reactions; severe minimization of any material interfaces to prevent thermomechanical problems such as delamination; robust performance in the presence of surface diffusion; and long-range geometric precision over large areas with severe minimization of very small feature sizes to maintain structural stability. Here we report an approach for high-temperature nanophotonics that surmounts all of these difficulties. It consists of an analytical and computationally guided design involving high-purity tungsten in a precisely fabricated photonic crystal slab geometry (specifically chosen to eliminate interfaces arising from layer-by-layer fabrication) optimized for high performance and robustness in the presence of roughness, fabrication errors, and surface diffusion. It offers nearultimate short-wavelength emittance and low, ultra-broadband long-wavelength emittance, along with a sharp cutoff offering 4∶1 emittance contrast over 10% wavelength separation. This is achieved via Q-matching, whereby the absorptive and radiative rates of the photonic crystal's cavity resonances are matched. Strong angular emission selectivity is also observed, with shortwavelength emission suppressed by 50% at 75°compared to normal incidence. Finally, a precise high-temperature measurement technique is developed to confirm that emission at 1,225 K can be primarily confined to wavelengths shorter than the cutoff wavelength. E ver since photonic bandgaps were predicted to exist in appropriately designed periodic subwavelength structures (1-3)-i.e., photonic crystals (PhCs), significant interest has garnered in recent years to exploit this property. Coupled with the recent advancements in nanofabrication techniques, many applications have been made possible, ranging from room-and cryogenic-temperature optoelectronic devices for development of all-optical integrated circuits (4), to highly sensitive sensors (5), low-threshold lasers (6), and highly efficient light emitting diodes (7). PhCs also enable us to accurately control spontaneous emission by virtue of controlling the photonic bandgap (1, 8). In particular, metallic PhCs have been shown to possess a large bandgap (9-12) and consequently superior modification of the intrinsic thermal emission spectra is readily achievable. This is extremely promising for many unique applications, especially high-efficiency energy conversion systems encompassing hydrocarbon and radioisotope fueled thermophotovoltaic (TPV) energy conversion (13,14) as well as solar selective absorbers and emitters for the...

show abstract

Section: Resultsmentioning

confidence: 99%

Enabling high-temperature nanophotonics for energy applications

Yeng

Ghebrebrhan²,

Bermel³

et al. 2012

Proc. Natl. Acad. Sci. U.S.A.

222

181

View full text Add to dashboard Cite

show abstract

“…The experimental value for α is 1.45 to 1.91 × 10 −5 K −1 in the 1000 to 2000 K temperature interval [16].…”

Section: Interatomic Potentialsmentioning

confidence: 94%

Assessment of interatomic potentials for atomistic analysis of static and dynamic properties of screw dislocations in W

Cereceda

Stukowski

Gilbert

et al. 2013

J. Phys.: Condens. Matter

View full text Add to dashboard Cite

Screw dislocations in bcc metals display non-planar cores at zero temperature which result in high lattice friction and thermally-activated strain rate behavior. In bcc W, electronic structure molecular statics calculations reveal a compact, non-degenerate core with an associated Peierls stress between 1.7 and 2.8 GPa. However, a full picture of the dynamic behavior of dislocations can only be gained by using more efficient atomistic simulations based on semiempirical interatomic potentials. In this paper we assess the suitability of five different potentials in terms of static properties relevant to screw dislocations in pure W. Moreover, we perform molecular dynamics simulations of stress-assisted glide using all five potentials to study the dynamic behavior of screw dislocations under shear stress. Dislocations are seen to display thermally-activated motion in most of the applied stress range, with a gradual transition to a viscous damping regime at high stresses. We find that one potential predicts a core transformation from compact to dissociated at finite temperature that affects the energetics of kink-pair production and impacts the mechanism of motion. We conclude that a modified embedded-atom potential achieves the best compromise in terms of static and dynamic screw dislocation properties, although at an expense of about ten-fold compared to central potentials.

show abstract

“…Thermal expansion was calculated with respect to these conditions. Equations for calculating the thermal expansion of tungsten at high temperatures were taken from [19,20]. To simplify the calculation of BðTÞ in the limited temperature range, the correction bðTÞ was approximated to be linear between the highest and lowest obtained temperatures, as…”

Section: Measurement Of the Residual Emissivity Correctionmentioning

confidence: 99%

Spectral irradiance model for tungsten halogen lamps in 340–850 nm wavelength range

2010

View full text Add to dashboard Cite

We have developed a physical model for the spectral irradiance of 1 kW tungsten halogen incandescent lamps for the wavelength range 340-850 nm. The model consists of the Planck's radiation law, published values for the emissivity of tungsten, and a residual spectral correction function taking into account unknown factors of the lamp. The correction function was determined by measuring the spectra of a 1000 W, quartz-halogen, tungsten coiled filament (FEL) lamp at different temperatures. The new model was tested with lamps of types FEL and 1000 W, 120 V quartz halogen (DXW). Comparisons with measurements of two national standards laboratories indicate that the model can account for the spectral irradiance values of lamps with an agreement better than 1% throughout the spectral region studied. We further demonstrate that the spectral irradiance of a lamp can be predicted with an expanded uncertainty of 2.6% if the color temperature and illuminance values for the lamp are known with expanded uncertainties of 20 K and 2%, respectively. In addition, it is suggested that the spectral irradiance may be derived from resistance measurements of the filament with lamp on and off.

show abstract

The measurement of thermal expansion coefficient of tungsten at elevated temperatures

Cited by 29 publications

References 4 publications

Enabling high-temperature nanophotonics for energy applications

Enabling high-temperature nanophotonics for energy applications

Assessment of interatomic potentials for atomistic analysis of static and dynamic properties of screw dislocations in W

Spectral irradiance model for tungsten halogen lamps in 340–850 nm wavelength range

Contact Info

Product

Resources

About