Roman Maev

The application of scanning acoustic microscopy to dielectric polymer composite material study

Acoustic microscopy is an effective method for visualization and quantitative analysis of physico-mechanical properties and microstructure of dielectric polymer blends and polymer composites. It allows one to use this method for investigating a wide variety of opaque materials and obtaining information about their inner structure as well as for optically transparent materials in which the contrast between different structures is practically absent. The methods of acoustic microscopy turns out to be very sensitive to any kind of inhomogeneties as well as various bulk defects: microcracks, pours, adhesion disturbance, exfoliation, inclusions, deviations from the given thickness off the layer in multilayered system and coating, technological deviations of sizes, orientation and grain distribution. In this work, the authors present experimental results investigation of two groups of objects. First is, polyethylene-polystyrene mixture films produced by different methods, where acoustic images clearly reveal the internal distribution of phases for each technological process. The second group is a multilayer dielectric structure, formed by different kinds of polymer, such as high density polyethylene, polyamide or ethylene vinyl alcohol, etc. In this case methods were used for nondestructive measurement of the thickness of multilayer polymer composite and adhesive layer and defect inspection.

Comparison between scanning acoustic microscopy and submillimeter spectroscopy. A new opportunity to investigate dielectric behavior and structure of materials

In acoustic microscopy, ultrasound and hypersound range waves (10 MHz-2 GHz) are used as the analysis factor. The following trends in the development of this method for polymers seem promising: morphology of smooth surfaces with nonuniform distribution of physical and mechanical properties, measurements of local anisotropy, study of dynamic phenomena connected with the change in materials due to physical factors (temperature, UV, IR, SHF-radiation), mechanical and chemical factors. In the field of submillimeter spectroscopy we have developed a spectrometer capable of performing dielectric measurements in solids in the previously inaccessible region of millimeter-submillimeter wavelengths (3-0.3 mm). The spectrometer employs intensive frequency tunable radiation from a Backward-Wave Oscillator (BWO) in combination with optical contactless measuring schemes, which realizes the most efficient advantages of infrared spectroscopy and conventional microwave technique: precise, independent measurements of the real /spl epsi/ and imaginary /spl epsi/ parts of the spectra in a wide frequency range.

Investigating Compact Bone Microstructure and Mechanical Properties Using Acoustic Microscopy

The bone tissue represents a substantial challenge for ultrasound inspection. In comparison with soft tissues it features the highest values of density, sound velocity, reflection and refraction ratios similar to those of metals. At the same time, unlike metals, the bone is a compound with heterogeneous chemical composition and very complicated structure, including osteons, Haversian channels, pores of various shape and dimensions. These factors caused definite difficulties in the acoustic microscopy application for bone condition diagnostics both in vivo and in vitro. Nevertheless there is a large area where acoustic microscopy could have a significant useful application. It is bone histology, which, undeservedly, has not been paid proper attention until now. At present, the basic histological techniques are light and electron microscopy. Electron microscopy requires fixing, contrasting, or preparing replicas. Light microscopy demands fixing, dehydration, demineralization, staining etc. The main bone tissue function is to provide resistance to various mechanical loads that is provided by the special interaction between organic and inorganic components. However histological procedures spoil intimate integration of organic and mineral components, and further, we study just shrunken structure, which may have no counterparts with alive tissue.