Precursors to Boron-Nitrogen Macromolecules and Ceramics

1986 ◽  
Vol 73 ◽  
Author(s):  
C. K. Narula ◽  
R. T. Paine ◽  
R. Schaeffer
Keyword(s):  
High Temperature ◽  
Boron Nitride ◽  
Important Material ◽  
The Past ◽  
High Temperature Reactions ◽  
Boron Nitrogen

ABSTRACTBoron nitride has been prepared in the past from classical high temperature reactions and more recently by CVD methods. Few attempts have been made to prepare this important material from pyrolyses of preceramic oligomers or polymers. In the present study oligomerization reactions of substituted borazenes with silyamine crosslinking groups have been found to provide useful gel materials which upon pyrolysis form boron nitrogen materials. Selected aspects of this chemistry and some characterization of the materials is presented.

Mass spectrometric characterization of high-temperature outgassing of anisotropic pyrolytic boron nitride

1985 ◽  
Vol 57 (14) ◽  
pp. 2995-2996 ◽  
Author(s):  
Paul L. Fortucci ◽  
Vincent D. Meyer ◽  
Edward K. Pang
Keyword(s):  
High Temperature ◽  
Boron Nitride ◽  
Mass Spectrometric ◽  
Pyrolytic Boron Nitride

Archaeological applications of natural gold analyses

2021 ◽  
pp. SP516-2021-59
Author(s):  
C. D. Standish ◽  
R. J. Chapman ◽  
N. R. Moles ◽  
R. D. Walshaw ◽  
J. A. Sheridan
Keyword(s):  
High Temperature ◽  
Bulk Alloy ◽  
Provenance Studies ◽  
Mineral Inclusions ◽  
Compositional Approach ◽  
Icp Ms ◽  
Wide Range ◽  
High Temperature Reactions ◽  
Microchemical Characterization

AbstractCompositional studies of natural gold usually have a geological focus, but are also important in archaeological provenancing. Both methodologies rely on compositional comparison of two sets of samples, one of which is geographically constrained. Here we describe how experiences in gold characterization resulting from geological studies are relevant to archaeology. Microchemical characterization of polished sections of natural gold identifies alloy compositions, alloy heterogeneity and mineral inclusions. Gold from all deposit types shows Cu and Sn values much lower than those recorded during numerous studies of artefacts. Inclusions in artefact gold include various Cu- and Sn-bearing compounds which indicate specific high temperature reactions that could ultimately illuminate the conditions of (s)melting. The use of LA-ICP-MS to generate a wide range of elemental discriminants for provenance studies may be compromised by alloy adulteration and/or unrepresentative analysis of natural/artefact alloys, which are commonly highly heterogeneous at the micron scale. Geological studies normally characterize only the earliest-formed (hypogene) alloy, whereas archaeology-focussed studies should entail analyses of bulk alloy compositions and impurities that may be incorporated during (s)melting. Isotopic-based provenancing alleviates many of these problems but, to date, generates regional rather than locality specific targets. A dual isotopic-compositional approach is recommended.

Use of two-color array pyrometry for characterization of combustion synthesis waves

2000 ◽  
Vol 15 (2) ◽  
pp. 572-580 ◽  
Author(s):  
U. Anselmi-Tamburini ◽  
F. Maglia ◽  
G. Spinolo ◽  
Z. A. Munir
Keyword(s):  
Activation Energy ◽  
Wave Propagation ◽  
High Temperature ◽  
Combustion Synthesis ◽  
Morphological Changes ◽  
Formation Of Cracks ◽  
High Temperature Reactions ◽  
Time Sequences

A two-color array pyrometer was used to investigate morphological developments on the surface of materials undergoing self-propagating high-temperature reactions. Time sequences of temperature spatial profiles during wave propagation were found to be complex in their nature and dynamics. They contain features that are interpreted in terms of morphological changes during the process. These features include formation of cracks or voids, expansion of the sample, and formation of droplets of metals on the surface. The use of the array pyrometer for determination of the activation energy of the combustion reaction between Zr and NiO is reported.

Characterization of High-Temperature Reactions at the BaO/W Interface

Langmuir ◽  
1996 ◽  
Vol 12 (21) ◽  
pp. 5099-5108 ◽  
Author(s):  
Jianou Shi ◽  
David L. Allara
Keyword(s):  
High Temperature ◽  
High Temperature Reactions
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