Thermal Conductivity of Boron Carbides

1987 ◽  
Vol 97 ◽  
Author(s):  
Marvin Moss
Keyword(s):  
Electron Microscopy ◽  
Thermal Conductivity ◽  
Scanning Electron Microscopy ◽  
Raman Spectroscopy ◽  
Temperature Dependence ◽  
Rutherford Backscattering ◽  
Rutherford Backscattering Spectroscopy ◽  
Theoretical Density ◽  
Increasing Temperature ◽  
Scanning Electron

ABSTRACTThe thermal conductivity, k, of boron carbides of various B/C ratios, two modes of preparation – hot pressed and carbothermic, and two isotopic variants of boron – 11B and normal boron 10.81B, was measured from 300 to 1023 K. The density and composition of the samples were reflected in the magnitude and temperature dependence of k, and were investigated further with scanning electron microscopy, Rutherford backscattering spectroscopy, and Raman spectroscopy. While lower than theoretical density in B4C reduces k, the characteristic monotonic decline of k with increasing temperature is retained. This k-vs.-T behavior distinguishes B4C from material with larger B/C ratios for which the temperature dependence is essentially nil.

Thermodynamic Constraints on Ion Beam Mixing of Metals on Insulators

1985 ◽  
Vol 45 ◽  
Author(s):  
G. C. Farlow ◽  
B. R. Appleton ◽  
L. A. Boatner ◽  
C. J. Mchargue ◽  
C. W. White ◽  
...  
Keyword(s):  
Electron Microscopy ◽  
Scanning Electron Microscopy ◽  
Ion Beam ◽  
Metal Films ◽  
Rutherford Backscattering ◽  
Rutherford Backscattering Spectroscopy ◽  
Reaction Enthalpy ◽  
Ion Beam Mixing ◽  
Interfacial Mixing ◽  
Scanning Electron

ABSTRACTSeveral different insulating substrates were coated with various metal films and ion beam irradiated using either Xe or Kr ions. These were then examined by Rutherford backscattering spectroscopy and scanning electron microscopy to determine if interfacial mixing had taken place. These results were compared with the sign of the reaction enthalpy of the metal and substrate to test the proposition that metals mix on insulators if the reaction enthalpy is negative and do not mix if it is positive. The enthalpy rule is in general valid. Two exceptions were found: Cr on Si02 and Zr on Al203; however, these exceptions contain ambiguous features.Irradiation with a light, reactive ion was found to produce no mixing.

Sausage Casings as a Model for Attachment of Salmonella to Meat

1993 ◽  
Vol 56 (5) ◽  
pp. 390-394 ◽  
Author(s):  
ISABEL WALLS ◽  
PETER H. COOKE ◽  
ROBERT C. BENEDICT ◽  
ROBERT L. BUCHANAN
Keyword(s):  
Electron Microscopy ◽  
Scanning Electron Microscopy ◽  
Bacterial Attachment ◽  
Bacterial Cells ◽  
Inoculum Level ◽  
Plate Counts ◽  
Increasing Temperature ◽  
Convenient Model ◽  
Sausage Casing ◽  
Scanning Electron

Artificial sausage casings were used as a model for studying bacterial attachment to meat connective tissue. Sausage casings of known mass were exposed to suspensions of Salmonella typhimurium in 0.15 M NaCl under various time, temperature, and inoculum level regimes, then washed to remove unattached bacteria. Attached bacterial cells were enumerated using both plate counts and scanning electron microscopy. Bacterial cells attached to sausage casing surfaces within 1 min of incubation. Numbers of attached cells increased with increasing temperature and inoculum levels and with time. Rates of attachment of S. typhimurium to sausage casings were comparable with those reported for attachment to meat surfaces. Sausage casings appear to be a convenient model for examining mechanisms of bacterial attachment to meats.

scholarly journals Improving the reactivity of phenylacetylene macrocycles toward topochemical polymerization by side chains modification

2014 ◽  
Vol 10 ◽  
pp. 1613-1619 ◽  
Author(s):  
Simon Rondeau-Gagné ◽  
Jules Roméo Néabo ◽  
Maxime Daigle ◽  
Katy Cantin ◽  
Jean-François Morin
Keyword(s):  
Electron Microscopy ◽  
Scanning Electron Microscopy ◽  
Raman Spectroscopy ◽  
Self Assembly ◽  
Significant Enhancement ◽  
Side Chains ◽  
X Ray Diffraction ◽  
X Ray ◽  
Topochemical Polymerization ◽  
Scanning Electron

The synthesis and self-assembly of two new phenylacetylene macrocycle (PAM) organogelators were performed. Polar 2-hydroxyethoxy side chains were incorporated in the inner part of the macrocycles to modify the assembly mode in the gel state. With this modification, it was possible to increase the reactivity of the macrocycles in the xerogel state to form polydiacetylenes (PDAs), leading to a significant enhancement of the polymerization yields. The organogels and the PDAs were characterized using Raman spectroscopy, X-ray diffraction (XRD) and scanning electron microscopy (SEM).

scholarly journals Structural and thermoelectric properties of the Pr2Zr2O7 compound

2019 ◽  
pp. 4-9
Author(s):  
Adolfo Quiroz-Rodríguez ◽  
Cesia Guarneros-Aguilar ◽  
Ricardo Agustin-Serrano
Keyword(s):  
Electron Microscopy ◽  
Thermal Conductivity ◽  
Thermoelectric Properties ◽  
Crystal Size ◽  
Ambient Pressure ◽  
X Ray Diffraction ◽  
X Ray ◽  
Increasing Temperature ◽  
Thermal Stability Of ◽  
Scanning Electron

In this research, it is presented a detailed study of the structural and thermoelectric properties of the pyrochlore zirconium Pr2Zr2O7 compound prepared by solid-state reaction (SSR) in air at ambient pressure. The synthesized sample was characterized using powder X-ray diffraction. The thermal stability of the thermoelectric compound (TE) Pr2Zr2O7 was tested by thermogravimetric analysis (TGA) and differential thermal analysis (DTA). Scanning electron microscopy shows that the crystal size varies between 0.69 and 2.81μm. Electrical conductivity (\sigma) of the sample calcined at 1400 °C presented values increase irregularly with the increasing temperature from 0.001 to 0.018 S cm-1 as expected in a semiconductor material. The thermal conductivity is lower than 0.44 - 775 W m-1 K-1 which is quite anomalous in comparison with the thermal conductivity of other oxides.

USE OF NANOFLUIDS BASED ON CARBON NANOPARTICLES TO DISPLACE OIL FROM THE POROUS MEDIUM MODEL

2020 ◽  
Vol 6 (4) ◽  
pp. 141-157
Author(s):  
Yuri V. Pakharukov ◽  
Farid K. Shabiev ◽  
Ruslan F. Safargaliev ◽  
Boris S. Yezdin ◽  
Valery V. Kalyada
Keyword(s):  
Electron Microscopy ◽  
Thermal Conductivity ◽  
Electrical Conductivity ◽  
Scanning Electron Microscopy ◽  
Porous Medium ◽  
Synergistic Effect ◽  
Transition Region ◽  
Dimensional Structure ◽  
Hybrid Nanofluids ◽  
Scanning Electron

Graphene, due to its two-dimensional structure, has some unique properties. For example, the thermal conductivity and electrical conductivity of graphene are an order of magnitude higher than the thermal conductivity and electrical conductivity of copper. For this reason, graphene-based nanofluids are now used in many industries. Due to the effect of self-organization of graphene nanoparticles with hydrocarbon molecules, the use of graphene has become possible in the oil industry. Graphene-based nanofluids are used as a displacement fluid to increase the oil recovery coefficient. The displacing ability of graphene-based nanofluids is concentration dependent. An increase in the concentration of nanoparticles entails an increase in viscosity, which negatively affects the performance characteristics of the nanofluid. This problem is partially solved due to the synergistic effect, hybrid nanofluids consisting of nanoparticles of graphene and metals or carbides enhance the displacing ability. Using atomic force microscopy, scanning electron microscopy and molecular modelling methods, this work has studied the formation of supramolecular structures that form a transition region at the oil-nanofluid interface with low surface tension as a result of a synergistic effect in the interaction of graphene planar nanoparticles and silicon carbide nanoparticles covered with graphene layers (Core-shell). The model experiments on a Hele-Shaw cell have shown that in a porous medium, such hybrid nanofluids have a high displacement ability of residual oil. At the same time, the oil — nanofluid interface remains stable, without the formation of viscous fingers. During the study by scanning electron microscopy, a transition region was observed, in the structuring of which the nanoparticles were directly involved. The displacement efficiency of a hybrid nonofluid depends on the concentration of nanoparticles and their interaction.

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