Experimental and Numerical Determination of Thermal Radiative Properties of ZnO Particulate Media

2009 ◽  
Vol 132 (1) ◽  
Author(s):  
P. Coray ◽  
W. Lipiński ◽  
A. Steinfeld
Keyword(s):  
Radiative Properties ◽  
Continuous Beam ◽  
Scattering Medium ◽  
Measured Intensity ◽  
Particulate Media ◽  
Varying Thickness ◽  
Thermal Radiative Properties ◽  
Exponential Trend ◽  
Radiative Characteristics

The radiative characteristics of dependently scattering packed-beds of ZnO particles, applied in the design of high-temperature solar thermochemical reactors, were investigated experimentally. ZnO samples of varying thickness were exposed to a continuous beam of near monochromatic thermal radiation in the 0.5–1 μm wavelength range. The overall transmitted fraction measured as a function of sample thickness s obeys an exponential trend exp(−As), with the fit parameter A ranging from 4000±100 m−1 at 555 nm to 2100±100 m−1 at 1 μm. In the forward directions, the measured intensity distribution is approximately isotropic, whereas in the backward directions it is well approximated by a Henyey–Greenstein equation with asymmetry factors g≈−0.4 at 555 nm and g≈−0.1 at 1 μm. A Monte Carlo ray-tracing model of the experimental setup is employed to extract the extinction coefficient and the scattering albedo for the case of a nongray absorbing-scattering medium.

Experimental and Numerical Determination of Thermal Radiative Properties of ZnO Particulate Media

2008 ◽  
Author(s):  
Patrick Coray ◽  
Wojciech Lipin´ski ◽  
Aldo Steinfeld
Keyword(s):  
Radiative Properties ◽  
Asymmetry Factor ◽  
Scattering Medium ◽  
Measured Intensity ◽  
Particulate Media ◽  
Thermal Radiative Properties ◽  
Exponential Trend ◽  
Set Up ◽  
Radiative Characteristics

The radiative characteristics of packed beds of ZnO particles, applied in the design of high-temperature solar thermochemical reactors, were investigated experimentally. ZnO samples of varying thickness were exposed to a continuous beam of near monochromatic thermal radiation in the 0.5–1 μm wavelength range. The overall transmitted fraction measured as a function of sample thickness s obeys an exponential trend exp(–As), with the fit parameter A ranging from (4000 ± 100) m−1 at 555 nm to (2100 ± 100) m−1 at 1 μm. In the forward directions, the measured intensity distribution is approximately isotropic, whereas in the backward directions it is well approximated by a Henyey–Greenstein equation with asymmetry factor g ≈ − 0.4 at 555 nm and g ≈ − 0.1 at 1 μm. A Monte Carlo ray-tracing model of the experimental set-up is employed to extract the extinction coefficient and the scattering albedo for the case of non-grey absorbing-scattering medium.

Determination of thermal radiative properties of packed-bed media containing a mixture of polydispersed particles

2009 ◽  
Vol 48 (8) ◽  
pp. 1510-1516 ◽  
Author(s):  
Klaus Jäger ◽  
Wojciech Lipiński ◽  
Helmut G. Katzgraber ◽  
Aldo Steinfeld
Keyword(s):  
Packed Bed ◽  
Radiative Properties ◽  
Thermal Radiative Properties

Direct phase determination in electron crystallography: small organic molecules

1992 ◽  
Vol 50 (2) ◽  
pp. 1166-1167
Author(s):  
Douglas L. Dorset
Keyword(s):  
Organic Molecules ◽  
Data Sets ◽  
Temperature Structure ◽  
3D Analysis ◽  
Intensity Data ◽  
Electron Crystallography ◽  
Phase Determination ◽  
Measured Intensity ◽  
3D Data

The quantitative use of electron diffraction intensity data for the determination of crystal structures represents the pioneering achievement in the electron crystallography of organic molecules, an effort largely begun by B. K. Vainshtein and his co-workers. However, despite numerous representative structure analyses yielding results consistent with X-ray determination, this entire effort was viewed with considerable mistrust by many crystallographers. This was no doubt due to the rather high crystallographic R-factors reported for some structures and, more importantly, the failure to convince many skeptics that the measured intensity data were adequate for ab initio structure determinations.We have recently demonstrated the utility of these data sets for structure analyses by direct phase determination based on the probabilistic estimate of three- and four-phase structure invariant sums. Examples include the structure of diketopiperazine using Vainshtein's 3D data, a similar 3D analysis of the room temperature structure of thiourea, and a zonal determination of the urea structure, the latter also based on data collected by the Moscow group.

Least-square refinement of structure parameters from CBED integrated intensities: application to determination of temperature factors in Y BA2CU3O7

1992 ◽  
Vol 50 (2) ◽  
pp. 1456-1457
Author(s):  
Kjersti Gjønnes ◽  
Jon Gjønnes
Keyword(s):  
Least Square ◽  
Measured Intensity ◽  
Structure Information ◽  
Accurate Temperature ◽  
Least Square Fit ◽  
Case Application ◽  
Integrated Intensities ◽  
Temperature Factors ◽  
Narrow Bands

Electron diffraction intensities can be obtained at large scattering angles (sinθ/λ ≥ 2.0), and thus structure information can be collected in regions of reciprocal space that are not accessable with other diffraction methods. LACBED intensities in this range can be utilized for determination of accurate temperature factors or for refinement of coordinates. Such high index reflections can usually be treated kinematically or as a pertubed two-beam case. Application to Y Ba2Cu3O7 shows that a least square refinememt based on integrated intensities can determine temperature factors or coordinates.LACBED patterns taken in the (00l) systematic row show an easily recognisable pattern of narrow bands from reflections in the range 15 < l < 40 (figure 1). Integrated intensities obtained from measured intensity profiles after subtraction of inelastic background (figure 2) were used in the least square fit for determination of temperature factors and refinement of z-coordinates for the Ba- and Cu-atoms.

Transient And Spatial Radiative Properties Of Patterned Wafers During Rapid Thermal Processing

1995 ◽  
Vol 387 ◽  
Author(s):  
Peter Y. Wong ◽  
Ioannis N. Miaoulis ◽  
Cynthia G. Madras
Keyword(s):  
Heat Transfer ◽  
Heat Source ◽  
Thermal Processing ◽  
Rapid Thermal Processing ◽  
Temporal Variations ◽  
Radiative Properties ◽  
Wafer Surface ◽  
Patterned Wafers ◽  
Thermal Radiative Properties ◽  
Dynamic Variations

AbstractTemperature measurements and processing uniformity continue to be major issues in Rapid Thermal Processing. Spatial and temporal variations in thermal radiative properties of the wafer surface are sources of non-uniformities and dynamic variations. These effects are due to changes in spectral distribution (wafer or heat source), oxidation, epitaxy, silicidation, and other microstructural transformations. Additionally, other variations are induced by the underlying (before processing) and developing (during processing) patterns on the wafer. Numerical simulations of Co silicidation that account for these factors are conducted to determine the radiative properties, heat transfer dynamics, and resultant processing uniformity.

Sign in / Sign up

Export Citation Format

Share Document