Electricity: measuring and testing – Particle precession resonance – Using a nuclear resonance spectrometer system
Patent
1992-04-29
1994-04-05
Tokar, Michael J.
Electricity: measuring and testing
Particle precession resonance
Using a nuclear resonance spectrometer system
324300, G01R 3320
Patent
active
053008880
DESCRIPTION:
BRIEF SUMMARY
The present invention relates to nuclear magnetic nuclear resonance (NMR), and, in particular, to the thermal analysis of various substances by use of the process known as proton magnetic resonance thermal analysis (PMRTA).
BACKGROUND OF THE INVENTION
It is known to take such NMR measurements with the sample held at, or near, room temperature by use of commercially available equipment known as an NMR spectrometer. One such spectrometer which is commercially available is the BRUKER MINISPEC manufactured by Bruker of Germany. While this device has a price which is within an acceptable range, the device suffers from the disadvantage that the temperature range at which measurements can be taken is limited. As the temperature controlled probes used with this device are water cooled, the maximum temperature at which any measurement can be taken is approximately 100.degree. C.
Another NMR spectrometer which is commercially available is that sold under the trade name MAGNEPULSE PC/AT 2000 by Auburn International Inc. of Danvers, Mass., U.S.A. Again this device operates at a substantially constant temperature.
However, many substance-q such as coal, NYLON, KEVLAR (Registered Trade Marks) and generally any solid, semi-solid or liquid organic material including polymers are desirably subjected to PMRTA. As such substances are heated they undergo various transformations from an initial equilibrium state to a final equilibrium state. The intermediate states are inherently non-equilibrium and transient. Thus, in order to capture information about these intermediate states, the measurement techniques would ideally be instantaneous. In practice this ideal is never met but practical results can be achieved if the time resolution of the in-situ measurement is adequate to monitor phenomena of interest. The NMR properties, which reflect the physical and chemical properties of the substance, are required to be recorded and monitored as a function of temperature and time as the substance is subjected to a controlled temperature program.
The measurement difficulties arise because of the continually changing nature of the properties of the specimen and the measurement equipment during the course of the analysis. For example, the dielectric properties of the specimen, coil resistance, and other electrical properties of the resonant radio frequency (RF) circuit change during the temperature changes. An analogy may be drawn to attempting to take fast exposure photographic snap shots of an object having a variable distance from the lens while the lens itself is changing its shape.
OBJECT OF THE INVENTION
It is the object of the present invention to provide a method of, and apparatus for, carrying out proton magnetic resonance thermal analysis measurements. This method and apparatus is capable of being substantially automated.
In carrying out such measurements, it is necessary to heat a small sample of the material to be analyzed to high temperatures in the absence of other hydrogen or proton containing material. The sample is held within a probe which is itself located within a magnetic field. The performance of the probe is largely dependent upon its mechanical, electrical and structural properties. It is an ancillary object of the present invention to provide a probe construction which enables the probe to be fabricated without undue difficulty and which enables accurate results to be achieved from the NMR measurements.
SUMMARY OF THE INVENTION
According to one aspect of the present invention there is disclosed a method of carrying out proton magnetic resonance thermal analysis measurements, said method comprising the steps of:
i) locating a sample within a coil forming part of an RF tuned circuit and applying a magnetic field to said sample,
ii) heating said sample in accordance with a predetermined temperature regime,
iii) applying pulsed RF energy to said coil to generate a pulsed RF electromagnetic field which is applied to said sample, and thereafter substantially simultaneously,
iv) adjusting the magnitude of said ma
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Lynch Leo J.
Webster David S.
Commonwealth Scientific and Industrial Research Organisation
Tokar Michael J.
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