High-frequency acoustic sensors for operation in a gaseous medium. Final report

Technical Report · Mon Dec 31 00:00:00 EST 1990

DOI:https://doi.org/10.2172/10192194· OSTI ID:10192194

Kino, G S

Photothermal microscopy is a technique for measuring thermal properties on a small scale by using focused laser beams as heat sources and as temperature probes. Typically used for nondestructive evaluation (NDE) of materials, its main advantage is its ability to measure types of flaws that are not visible optically or acoustically. Because of the optical nature of photothermal microscopy, sub-micron resolutions can be obtained in many of these thermal measurements. The greatest limitation of these systems is their relatively poor signal-to-noise ratios and, consequently, slow imaging speeds. To circumvent this problem, a variety of approaches to the detection of thermal waves has been pursued in recent years. This thesis compares the relative merits of a common class of techniques that rely on direct observation of physical changes in the heated sample, including a novel approach to interferometric measurement of the thermal expansion. It is found that the optimum approach depends not only on the physical properties of the sample being studies, but also upon the resolution of the experiment and the damage threshold of the specimen. Finally, this dissertation describes the applications of photothermal microscopy to the study of the anisotropic thermal properties of the new high-{Tc} superconductors. By adding a high-vacuum cryostat to the microscope, the authors have been able to study the influence of the superconducting transition on the thermal conductivity. The measurements of the anisotropic thermal conductivity demonstrate that the heat flow along the superconducting planes is enhanced below the transition, and that no such enhancement exists in the non-superconducting direction. Material examined was Bi-Ca-Sr-Cu-O.

• Research Organization: Stanford Univ., CA (United States). Edward L. Ginzton Lab.
• Sponsoring Organization: USDOE, Washington, DC (United States)
• DOE Contract Number: FG03-87ER13797
• OSTI ID: 10192194
• Report Number(s): DOE/ER/13797-T1; GL-4979; ON: DE95002123; BR: KC0401030; TRN: AHC29428%%69
• Resource Relation: Other Information: PBD: [1990]
• Country of Publication: United States
• Language: English

Related Subjects

42 ENGINEERING
36 MATERIALS SCIENCE
MICROSCOPY
BISMUTH OXIDES
THERMODYNAMIC PROPERTIES
CALCIUM OXIDES
STRONTIUM OXIDES
COPPER OXIDES
PROGRESS REPORT
NONDESTRUCTIVE TESTING
LASER RADIATION
SPATIAL RESOLUTION
PERFORMANCE
INTERFEROMETRY
PHOTODETECTORS
420500
360204
MATERIALS TESTING
PHYSICAL PROPERTIES