Thermal Resistance of Fine Powders at Atmospheric Pressure and under Vacuum

2009 ◽  
pp. 52-52-14 ◽  
Author(s):  
DL McElroy ◽  
FJ Weaver ◽  
DW Yarbrough ◽  
RS Graves
Keyword(s):  
Thermal Resistance ◽  
Atmospheric Pressure ◽  
Fine Powders

Evaluation of Thermal Insulation Properties of Fibrous Mineral Fine Powders

2010 ◽  
Vol 178 ◽  
pp. 339-343
Author(s):  
Fei Wang ◽  
Jin Sheng Liang ◽  
Chong Yan Ren ◽  
Qing Guo Tang
Keyword(s):  
Experimental Data ◽  
Thermal Resistance ◽  
Thermal Insulation ◽  
Thermal Conduction ◽  
Fibrous Materials ◽  
Fine Powders ◽  
Resistance Model ◽  
Fibrous Mineral ◽  
The Relationship ◽  
Sepiolite Nanofibers

The equivalent thermal resistance model of sepiolite mineral nanofibers has been presented in this paper to predict the thermal insulation properties of fibrous mineral fine powders. The model was based on the correlation between thermal conduction and gas & solid conduction in the fibrous system. According to the analysis about the process of heat transfer in sepiolite nanofibers, the total thermal conduction can be described as the synergism of the solid thermal conduction and the gaseous thermal conduction. From the equivalent thermal resistance model of fibrous materials in the accumulative condition, it can be seen that the thermal conduction of fibrous mineral fine powders can be evaluated by the relationship between bulk density and thermal conduction of sepiolite nanofibers. Comparing the theoretical values with experimental data obtained from thermal conduction instrument, it was found that the theoretical values corresponded well with experimental data.

Thermal Conductivity and Compressive Strain of Aerogel Insulation Blankets Under Applied Hydrostatic Pressure

2006 ◽  
Vol 129 (2) ◽  
pp. 232-235 ◽  
Author(s):  
Erik R. Bardy ◽  
Joseph C. Mollendorf ◽  
David R. Pendergast
Keyword(s):  
Thermal Conductivity ◽  
Thermal Resistance ◽  
Residual Strain ◽  
Atmospheric Pressure ◽  
Compressive Strain ◽  
Product Line ◽  
Strain Effect ◽  
Total Thermal Resistance ◽  
Original State ◽  
Elevated Pressures

Aerogel is among the best solid thermal insulators. Aerogel is a silica gel formed by supercritical extraction which results in a porous open cell solid insulation with a thermal conductivity as low as 0.013W∕mK. Aerogels have a wide range of uses such as insulation for windows, vehicles, refrigerators∕freezers, etc. Usage for aerogel can be extended for use where flexibility is needed, such as apparel, by embedding it into a polyester batting blanket. These aerogel blankets, although flexible, have little resistance to compression and experience a residual strain effect upon exposure to elevated pressures. It was suggested, by Aspen Aerogels Inc., that a prototype aerogel blanket would have increased resistance to compression and minimized residual strain upon exposure to elevated pressures. Samples of prototype and normal product-line aerogel insulating blankets were acquired. These materials were separately tested for thermal conductivity and compressive strain at incremental pressure stops up to 1.2MPa. The compressive strain of the prototype aerogel blanket reached a level of 0.25mm∕mm whereas the product-line aerogel blanket compressed to 0.48mm∕mm at 1.2MPa. Before compression, the thermal conductivity of the prototype aerogel blanket was slightly higher than the product-line aerogel blanket. During compression the thermal conductivity increased 46% for the product-line aerogel blanket whereas it increased only 13% for the prototype aerogel blanket at 1.2MPa. The total thermal resistance decreased 64% for the product-line aerogel blanket at 1.2MPa and remained at that value upon decompression to atmospheric pressure. The total thermal resistance of the prototype aerogel blanket decreased 33% at 1.2MPa and returned to within 1% of its initial value upon decompression to atmospheric pressure. It was found that the prototype aerogel blanket has approximately twice as much resistance to hydrostatic compression to a pressure of 1.2MPa and also recovers to its original state upon decompression. The thermal resistance of the prototype aerogel blanket remained 37% higher than the product-line aerogel blanket at 1.2MPa. This resistance to compression and the ability to recover to its original state upon decompression from elevated pressures makes the prototype aerogel blanket suitable for applications where high insulation, resistance to compression, and recovery after a compression cycle is needed.

A High-Voltage Terminal for a Field-Emission Gun

1972 ◽  
Vol 30 ◽  
pp. 428-429
Author(s):  
N. F. Ziegler
Keyword(s):  
Field Emission ◽  
High Voltage ◽  
Atmospheric Pressure ◽  
Power Supplies ◽  
High Coherence

A high-voltage terminal has been constructed for housing the various power supplies and metering circuits required by the field-emission gun (described elsewhere in these Proceedings) for the high-coherence microscope. The terminal is cylindrical in shape having a diameter of 14 inches and a length of 24 inches. It is completely enclosed by an aluminum housing filled with Freon-12 gas at essentially atmospheric pressure. The potential of the terminal relative to ground is, of course, equal to the accelerating potential of the microscope, which in the present case, is 150 kilovolts maximum.

Electron microscope characterization of MOCVD-grown gap layers on Si

1986 ◽  
Vol 44 ◽  
pp. 724-725
Author(s):  
K.M. Jones ◽  
M.M. Al-Jassim ◽  
J.M. Olson
Keyword(s):  
Atmospheric Pressure ◽  
Vapour Deposition ◽  
Chemical Vapour ◽  
Organic Chemical ◽  
Lattice Match ◽  
Si Substrates ◽  
Metal Organic ◽  
Good Lattice ◽  
Antiphase Domains

The epitaxial growth of III-V semiconductors on Si for integrated optoelectronic applications is currently of great interest. GaP, with a lattice constant close to that of Si, is an attractive buffer between Si and, for example, GaAsP. In spite of the good lattice match, the growth of device quality GaP on Si is not without difficulty. The formation of antiphase domains, the difficulty in cleaning the Si substrates prior to growth, and the poor layer morphology are some of the problems encountered. In this work, the structural perfection of GaP layers was investigated as a function of several process variables including growth rate and temperature, and Si substrate orientation. The GaP layers were grown in an atmospheric pressure metal organic chemical vapour deposition (MOCVD) system using trimethylgallium and phosphine in H2. The Si substrates orientations used were (100), 2° off (100) towards (110), (111) and (211).

Microstructure and reactivity of small metal particles: The role of Ce additives

1992 ◽  
Vol 50 (1) ◽  
pp. 318-319
Author(s):  
L.D. Schmidt ◽  
K. R. Krause ◽  
J. M. Schwartz ◽  
X. Chu
Keyword(s):  
Atmospheric Pressure ◽  
Noble Metals ◽  
Mixed Oxides ◽  
Catalytic Properties ◽  
Chemical Shifts ◽  
Catalytic Converter ◽  
Structural Evolution ◽  
Single Particles ◽  
Small Metal Particles

The evolution of microstructures of 10- to 100-Å diameter particles of Rh and Pt on SiO2 and Al2O3 following treatment in reducing, oxidizing, and reacting conditions have been characterized by TEM. We are able to transfer particles repeatedly between microscope and a reactor furnace so that the structural evolution of single particles can be examined following treatments in gases at atmospheric pressure. We are especially interested in the role of Ce additives on noble metals such as Pt and Rh. These systems are crucial in the automotive catalytic converter, and rare earths can significantly modify catalytic properties in many reactions. In particular, we are concerned with the oxidation state of Ce and its role in formation of mixed oxides with metals or with the support. For this we employ EELS in TEM, a technique uniquely suited to detect chemical shifts with ∼30Å resolution.

Modeling of mass-transportation of tris-(acetylacetonato)chromium(III) at atmospheric pressure

1999 ◽  
Vol 09 (PR8) ◽  
pp. Pr8-251-Pr8-258 ◽  
Author(s):  
N. E. Fedotova ◽  
A. N. Mikheev ◽  
N. V. Gelfond ◽  
I. K. Igumenov ◽  
N. B. Morozova ◽  
...  
Keyword(s):  
Atmospheric Pressure ◽  
Mass Transportation

Modeling of silicon epitaxial growth with SiHCl3 in a CVD barrel reactor at atmospheric pressure

1999 ◽  
Vol 09 (PR8) ◽  
pp. Pr8-221-Pr8-228
Author(s):  
E. de Paola ◽  
P. Duverneuil ◽  
A. Langlais ◽  
M. Nguyen
Keyword(s):  
Epitaxial Growth ◽  
Atmospheric Pressure ◽  
Barrel Reactor
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