The paper gives the melting points of the various materials found in microspheres, and then suggests that the fires must have reached those temperatures in order to produce the spheres.
I see two problems with this.
One is, the idea of the "temperature reached by a fire" is vague, and Jones uses typical measurements which are macroscopic in scale. Most measurements of fire "temperature" are of the air layers in an enclosed space above the fire (usually the top layers, which get hottest.) Mean flame temperatures are sometimes also measured or estimated. But flame temperatures aren't uniform. Parts of a wood flame can have temperatures over 1700°C -- or higher in a post-flashover environment where radiation losses to the surroundings are reduced. Normally this is disregarded because it's only within small regions of the flame that such high temperatures are reached, so it doesn't greatly affect the heating of the surroundings, such as the air layers or even a macroscopic object that the flame might be impinging on. But it must be taken into account when the formation of very small particles is at issue. The paper is about microspheres; mean temperatures on a macroscopic scale are not the only relevant temperatures.
The second is that by concluding that the melting points of the materials in the microspheres must have been reached in the environment, Jones is implicitly assuming specific mechanisms of formation of the spheres: either small isolated chips of mixed metals melted into spherical shapes by the heat of their immediate surroundings (undergoing no chemical change in the process), or bulk amounts of mixed metals being melted and then subsequently separated into spherical droplets by mechanical agitation. (He seems to prefer the latter scenario.) But I'm given to understand by experts here that such spheres can also be formed by chemical reactions that occur at temperatures lower than the melting points, and (if I'm understanding correctly; please correct me if I'm wrong) those reactions can be exothermic, self-heating the spheres above the surrounding temperature.
Thus, the paper's contention that the spheres are evidence of ambient temperatures on a macroscopic scale reaching or exceeding the melting points of the metals in the spheres is not supported by the evidence offered.
Respectfully,
Myriad
I see two problems with this.
One is, the idea of the "temperature reached by a fire" is vague, and Jones uses typical measurements which are macroscopic in scale. Most measurements of fire "temperature" are of the air layers in an enclosed space above the fire (usually the top layers, which get hottest.) Mean flame temperatures are sometimes also measured or estimated. But flame temperatures aren't uniform. Parts of a wood flame can have temperatures over 1700°C -- or higher in a post-flashover environment where radiation losses to the surroundings are reduced. Normally this is disregarded because it's only within small regions of the flame that such high temperatures are reached, so it doesn't greatly affect the heating of the surroundings, such as the air layers or even a macroscopic object that the flame might be impinging on. But it must be taken into account when the formation of very small particles is at issue. The paper is about microspheres; mean temperatures on a macroscopic scale are not the only relevant temperatures.
The second is that by concluding that the melting points of the materials in the microspheres must have been reached in the environment, Jones is implicitly assuming specific mechanisms of formation of the spheres: either small isolated chips of mixed metals melted into spherical shapes by the heat of their immediate surroundings (undergoing no chemical change in the process), or bulk amounts of mixed metals being melted and then subsequently separated into spherical droplets by mechanical agitation. (He seems to prefer the latter scenario.) But I'm given to understand by experts here that such spheres can also be formed by chemical reactions that occur at temperatures lower than the melting points, and (if I'm understanding correctly; please correct me if I'm wrong) those reactions can be exothermic, self-heating the spheres above the surrounding temperature.
Thus, the paper's contention that the spheres are evidence of ambient temperatures on a macroscopic scale reaching or exceeding the melting points of the metals in the spheres is not supported by the evidence offered.
Respectfully,
Myriad