Micro-thermal analysis: techniques and applications

Abstract

The terms micro-thermal analysis and micro-spectroscopic analysis are used to include any form of localized characterization or analysis combined with microscopy that uses a near-field thermal probe to exploit the benefits of using thermal excitation. Individual regions of a solid sample are selected by means of surface or sub-surface imaging (atomic force microscopy and/or scanning thermal microscopy), so as to add spatial discrimination to four well-established methods of chemical fingerprinting, namely thermomechanometry, calorimetry, spectroscopy and analytical pyrolysis. We begin by describing the state of the art of scanning microscopy that uses resistive thermal probes, followed by an account of the various techniques of micro-thermal analysis. Modern materials technology is increasingly concerned with the control of materials at the mesoscale. The ability to add an extra dimension of, say, chemical composition information to high-resolution microscopy, or microscopic information to spectroscopy, plays an increasingly useful part in applied research. Micro-thermal analysis is now being used commercially to visualize the spatial distribution of phases, components and contaminants in polymers, pharmaceuticals, foods, biological materials and electronic materials. This review outlines various applications that have been described in the literature to date, the topics ranging from multi-layer packaging materials and interphase regions in composites, to the use of the technique as a means of surface treatment.

Concurrent elution of calcium phosphate and macromolecules from alginate/chitosan hydrogel coatings

“…35,40,41 With a hydrogel coating thickness of the order of 100 nm, -TA is expected to detect FIG. 1.…”

Nanoscale resolution scanning thermal microscopy using carbon nanotube tipped thermal probes

“…11,12 Scanning thermal microscopy (SThM) [11][12][13][14][15][16][17][18][19] has come a long way since its invention 11 in 1986 and currently plays a leading role in the investigation of thermal properties on the nanoscale. SThM use a self-heating thermal sensors incorporated within a sharp tip that is thermally contacted with a sample surface and is widely used in studies of polymeric and organic materials 15 .…”

Nanoscale thermoelastic probing of megahertz thermal diffusion

“…To overcome this limit for purposes of imaging transient thermal fields, the most developed thermal sensing schemes with submicron lateral resolution are based on scanned local probe techniques. 14,15 Use of a modulated heat source in an atomic force microscope ͑AFM͒ tip, for example, has proved useful for imaging time-varying temperature distributions up to frequencies of ϳ100 kHz. [15][16][17] AFM-based probing of kilohertz surface vibrations induced by resistive heating or chopped light allows additional contrast from the thermal expansion coefficient.…”