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 TBC Systems with NiPtAl or NiCoCrAlYTa Bond Coatings after Thermal Cycling at 1100°C: A Comparative Study of Failure Mechanisms

2008 ◽  
Vol 595-598 ◽  
pp. 213-221 ◽  
Author(s):  
Aurélie Vande Put ◽  
Djar Oquab ◽  
Daniel Monceau
Keyword(s):  
High Temperature ◽  
Comparative Study ◽  
Thermal Cycling ◽  
Nickel Aluminide ◽  
Morphological Changes ◽  
Failure Mechanisms ◽  
Bond Coatings ◽  
Failure Path ◽  
Tbc Systems

During service, TBC can suffer degradation by CMAS, FOD, erosion or spallation. Whereas the first three are due to foreign particles, the last one is related to thermal cycling. When subjected to high temperature exposures followed by rapid coolings under oxidizing conditions, a TBC system undergoes morphological changes and stress development. This will initiate cracks which propagate and finally lead to failure by spallation. Consequently, the aim of the present study is to understand better the mechanisms responsible for such spallation events. Two kinds of TBC systems with different bond coatings (NiCoCrAlYTa or Pt-modified nickel aluminide bond coatings) are thermally cycled. Subsequently, SEM investigations on TBC systems after spallation concentrate on failure path, defect, morphological and microstructural changes to propose way for improving TBC system lifetime.

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.

scholarly journals Determination of the viscosity of molten salts by a capillary method. The system cadmium chloride-cadmium bromide

1948 ◽  
Vol 194 (1037) ◽  
pp. 237-244 ◽  
Keyword(s):  
Activation Energy ◽  
High Temperature ◽  
Molten Salts ◽  
Cadmium Chloride ◽  
Molar Fraction ◽  
Recording Device ◽  
Capillary Method ◽  
Cadmium Bromide ◽  
Salt Mixtures

The knowledge of the viscosity of molten salts and their mixtures is important (1) for testing recent theories by Eyring and by Frenkel, and (2) for confirming or modifying conclusions regarding the constitution of certain molten salt mixtures which were investigated by Bloom & Heymann. A capillary method based on the Ubbelohde-Bingham principle has been adapted to the conditions at high temperature. The main feature of the method is an automatic electric recording device, involving a balanced Wheatstone net with amplifier and an electric clock. The isotherms of viscosity plotted against molar fraction in the system CdCl 3 -CdBr 2 are linear. The activation energy of viscosity is 1.6 to 1.8 times as great as the activation energy of ionic migration.

Sign in / Sign up

Export Citation Format

Share Document