Thermal measuring and testing – Transformation point determination – By change in optical property
Reexamination Certificate
1999-04-08
2001-05-15
Gutierrez, Diego (Department: 2859)
Thermal measuring and testing
Transformation point determination
By change in optical property
C374S022000, C250S341100, C250S341600
Reexamination Certificate
active
06231228
ABSTRACT:
BACKGROUND OF THE INVENTION
1. Field of the Invention
This invention resides in the area of apparatuses and methods used for the determination of melting points of materials and more particularly relates to an apparatus and method which determines the melting point of a sample material by measuring temperature changes of the material until the thickness of the sample material goes to zero under pressure.
2. Description of the Prior Art
Many methods are used to determine melting points of materials. The simplest are types where observers note temperatures at which materials, upon heating, become transparent such methods first involve immersing the particle of material whose melting point is to be determined in a non-solvent which is heated at a known rate. As the heat from the medium is transferred into the particle, at the point where the temperature of the medium is equal to the melting point of the particle, the particle changes its optical transmissibility and also may change its physical shape. The automated recording of temperature while an observer monitors the reflectivity of infrared light directed at material is disclosed in International Application No. PCT/GB90/00751. A problem with many of these prior art melting point determination apparatuses is that they lack accuracy in that they require the judgment of an observer as to when a reaction has taken place, and this judgment can vary from observer to observer.
U.S. Pat. No. 5,092,679 by the present inventor disclosed an apparatus and method that automatically records measurements of both light reflectivity or transmissivity and temperature of a material to determine its melting point. The invention also disclosed means for recording deformation of materials at various pressures.
A November, 1991 article in
Laboratory Equipment Digest
entitled “Faster and Simpler Melting Point Measurement” described a melting point device which measures the reflectivity of near-infrared light directed at a material, which material rests on a plate of borosilicate glass heated from below by a flat film strip heater. A problem with many of the prior art apparatuses is that they require a light source and measure the reflectivity of light directed at the sample material.
SUMMARY OF THE INVENTION
It is an object of the device and method of this invention to determine the melting point of a sample material utilizing a narrow field of view non-contact infrared thermometer hereinafter referred to as an infrared thermometer. The use of such an infrared thermometer allows for a standard temperature scale to be utilized.
It is a further object of this invention to provide a device to determine melting point as it relates to pressure. It is important that pressure be considered when determining a melting point of a material because at different pressures, a material at its melting point may have a variety of states.
The device of this invention utilizes a powder made from the material that is to have its melting point determined. The powdered material is placed between an upper first glass plate and a lower second glass plate to form a wafer which wafer/plate sandwich is supported by a support member disposed under each end of the lower plate on its bottom side. Pressure is first applied to the upper plate. In one embodiment heat is then applied to the upper plate from above and the temperature of the sandwiched wafer is measured by an infrared thermometer positioned under the lower plate. The temperature of the bottom surface of the lower plate is continuously recorded. When the sample material melts, it thins and spreads out, changing the heat transmission properties of the wafer, and is no longer sensed by the infrared thermometer. At that point in time when the infrared thermometer directly senses the heat source, the indicated temperature spikes, and a chart recorder indicates the temperature at that point in time of such temperature spike which corresponds to the melting point of the sample material. Toroidal heat sources can also be utilized in some embodiments above, and in some embodiments below, the plates. Once the sample melts, the toroidal heat source, not being in the direct line of sight of the infrared thermometer which has a narrow field of view, is then not sensed and the indicated temperature detected drops at the melting point of the material which temperature drop is recorded.
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Gutierrez Diego
Nitkin William
Pruchnic Jr. Stanley J.
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