Thermal measuring and testing – Thermal testing of a nonthermal quantity – With loading of specimen
Reexamination Certificate
1998-12-31
2001-03-13
Bennett, G. Bradley (Department: 2859)
Thermal measuring and testing
Thermal testing of a nonthermal quantity
With loading of specimen
C374S043000, C374S020000
Reexamination Certificate
active
06200022
ABSTRACT:
BACKGROUND OF THE INVENTION
1. Field of the Invention
The present invention relates generally to thermal analysis methods and apparatus. More specifically, the present invention relates to static and dynamic thermomechanical analysis of localized regions of inhomogeneous samples that are identified and selected at high spatial resolution using scanning probe microscopy.
2. Description of the Related Art
Techniques for the thermomechanical characterization of solids and thin films are well-known and widely used. A description of such methods is given in “Thermal Analysis—Techniques and Applications” by E. L. Charsley and S. B. Warrington (eds.), Royal Society of chemistry, Cambridge, England (1992), which is hereby incorporated by reference in its entirety herein. There are several problems with these methods.
One problem is a practical one. Conventional thermomechanical or dynamic mechanical analysis experiments are often very time consuming, typically requiring several hours to complete. Consequently, solutions to urgent problems in industry are often delayed.
Another problem is related to sampling or data collection. Frequently, the sample being analyzed is either too small or too thin, or it is buried within a larger component from which it is difficult or impossible to extract. For example, the problems associated with obtaining a sufficient sample of a thin film that is firmly adhered to a substrate or sandwiched between two other layers are well-known.
Another problem is more fundamental in nature. Thermal methods are particularly useful in studying the morphology of polymer and polymer-containing samples. Modulated Temperature Differential Scanning Calorimetry (MTDSC), which was developed several years ago by Reading and co-workers, has greatly increased the quality of the structural information that can be obtained by calorimetry. See, M. Reading in Trends in Polymer Science vol. 1 pp. 248-53 (1993) and U.S. Pat. No. 5,224,775 to Reading et al. (the “'775 patent”), both of which are hereby incorporated by reference in their entirety herein. One advantage of MTDSC is that ‘reversing’ and ‘non-reversing’ processes can be separated. A second advantage of MTDSC is the improvement in the sensitivity and resolution with which glass transitions can be measured. As a result, scientists have found that MTDSC offers unique benefits in the study of curing systems, semi-crystalline polymers, and, in particular, polymer blends and related systems. But, even this advanced method cannot give spatially resolved information.
Moreover conventional thermomechanical analysis is performed using bulk samples, and consequently does not provide spatially resolved data. The inability of conventional thermal analytical techniques to give spatially resolved information is a critical shortcoming because modern polymeric materials are usually blends or composites with complex morphologies whose evaluation is crucial to the determination of their material properties. But, conventional thermal analysis techniques provide no information regarding the size of the domains or how they are distributed in space.
Therefore, it would be advantageous to use the advantages offered by each of the techniques described above and others described below by incorporating them into a technique for localized thermomechanical and calorimetric analysis, together with high-resolution microscopy.
SUMMARY OF THE INVENTION
The present invention is a thermal analysis system and method which allows a user to obtain images whose contrast is determined by either surface topography, or by sub-surface variations in mechanical or thermal properties, using an active or passive thermal probe. In general, thermal analysis is a set of techniques including differential scanning calorimetry (“DSC”), modulated temperature differential scanning calorimetry (“MTDSC” or “MDSC®”), dynamic mechanical analysis (“DMA”), thermomechanical anslysis (“TMA”), thermogravimetric analysis (“TGA”) and differential thermal analysis (“DTA”).
In a preferred embodiment of the present invention, a region of the sample is selected for analysis from an image of the sample. This region is subjected to a localized temperature heating or cooling ramp. The heat is supplied by the thermal probe itself, or by a similar adjacent probe, with or without the addition of supplementary general heating as provided by a sample heater stage. Several kinds of measurements are made during application of the temperature ramp. One measurement is a measurement of quasi-static and dynamic mechanical compliance of the selected region. Another measurement is a measurement of the heat flow into the sample. These measurements can be used to generate graphs or fingerprints of the localized region of the sample under study. Thus, the present invention provides localized thermomechanical and calorimetric analysis measurements simultaneously.
The present technique for performing localized thermomechanical analysis is termed Mechanothermal Analysis with Scanning Microscopy (“MASM”). Two MASM techniques are disclosed. “Static MASM” localizes conventional thermomechanical analysis (“TMA”), i.e., studies involving the application of zero frequency (linear) temperature programs to the sample being analyzed. Static MASM is described in F. Oulevey, A. Hammiche, H. M. Pollock, N. A. Burnham, M. Song, D. J. Hourston and M. Reading, “Phase transitions in polymers: towards dynamic mechanical analysis with submicron spatial resolution,” in “Surfaces and interfaces of polymers and composites,” European Physical Society Conference on Molecular Physics, vol. 21B, Lausanne, Jun. 1-6 1997, R. Pick and G. Thomas, eds., European Physical Society 1997, pp. 155-56, which is hereby incorporated by reference in its entirety.
“Dynamic MASM” localizes Dynamic Mechanical Analysis (“DMA”). In DMA, a sinusoidal stress or strain is imposed on a sample to be analyzed. Any stress or strain which can be characterized as a function of one or more frequencies and amplitudes can be used. The resulting data is generally displayed in curves representing the storage modulus and the loss modulus as a function of temperature. Thermal events are derived from the storage and loss modulus data. Although, DMA does not reveal all the information provided by differential scanning calorimetry, it is several orders of magnitude more sensitive for the study of some phase transitions and relaxation spectra. For such events, therefore, MASM offers a higher sensitivity than calorimetric analysis with scanning microcscopy (“CASM”), as described, for example, in the '547 application.
A first object of the present invention is to use a scanning probe microscope to obtain images from which regions may be selected for the subsequent acquisition of localized thermomechanical data.
Another object of the present invention is to subject a localized region of a sample to both upward and downward temperature ramps, and at the same time to impose a combination of fixed and sinusoidally-modulated strain, while measuring the resultant force.
Another object of the present invention is to subject a localized region of a sample to both upward and downward temperature ramps, while simultaneously imposing a combination of fixed and sinusoidally-modulated force on the region, and then measuring the resultant strain.
Another object of the present invention is to use data resulting from the localized applied stress or strain in the presence of upward and downward temperature ramps to detect meltings, glass transitions and other thermal events, and to distinguish between reversible and irreversible contributions to the phenomena revealed in such events.
Another object of the present invention is to provide an ability to collect both MASM and CASM data substantially simultaneously.
Another object of the present invention is to select individual regions of a sample surface with a spatial resolution of a few tens of nanometers, on which to perform localized thermomechanical measurements.
Another object of the present invention is to obtain scanning prob
Hammiche Azzedine
Montague-Pollock Hubert Murray
Reading Michael
Bennett G. Bradley
Shaw Pittman
TA Instruments, Inc.
Verbilsky Gail
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