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The effect of transformation of focused ultrasound radiation into collimated beams of longitudinal and transverse waves in the volume of a hemispherical transformer after refraction on its surface has been described. When the hemisphere is fastened on a studied plane–parallel object, the formed sharp beams of elastic waves incident normally on the surface of the sample make it possible to perform elastic measurements with minimum errors, which can be due to refractive aberrations of the focused beam.

The volumetric visualization of materials and inner boundaries of a joint is one of the fields in which long-focus high-frequency beams are used. Visualization is carried out using beams that passed through the immersion–sample interface and changed their geometry due to differences in the refraction of rays being incident at different angles on the interface. The beam structure is substantially distorted upon refraction and transforms into a caustic. The problem of spatial resolution in the formation of acoustic images of the microstructure in the material bulk is relevant. This paper presents a theoretical analysis of the spatial resolution with consideration for refractive aberrations in the formation of images of interfaces that are located at a considerable depth in the sample bulk. The results of the experimental visualization of the interface between jointed materials are presented. It is shown that the theoretical estimate is in good agreement with the experimental value of the resolution for beams of longitudinal waves converging in the sample volume.

The production of composites based on nanopowders synthesized by the sol-gel method in the system aluminum oxide and tetragonal zirconium dioxide stabilized by cerium cations (Al2O3–[Ce–TZP]) is described. It is shown that modification of the compositions by calcium oxide promotes the formation of composites of a dispersion-hardening phase in the form of long-prismatic grains in the sintering process. The presence of this phase affects the increase of strength and resistance to brittle fracture of composites with a ZrO2 matrix and with an Al2O3 matrix. The strength in static bending of the composites reaches 1000 MPa and the cracking resistance K 1c increases to 11.0 MPa·m1/2.

Nowadays there is a great practical interest in research and development of nonwoven fibrous materials based on biopolymers for medical purposes. One of the most promising methods for obtaining nonwoven materials with a highly developed surface is electrospinning. In this paper the possibility of effective sterilization by ozone treatment method of ultrafine fibers based on polyhydroxybutyrate (PHB) was considered. The purpose of the study was to establish the correlation between changes in the supramolecular structure and the physical-mechanical properties of fibrous materials under the influence of ozone. The study was carried out by using differential scanning calometry (DSC), electronic paramagnetic resonance (EPR), optical microscopy and scanning electron microscopy (SEM) methods.

Currently, the development and research of nonwoven medical fibrous materials based on biopolymers is an area of a great practical interest. One of the most promising methods for producing nonwoven materials with a highly developed surface is electrospinning (ES). In the article, the possibility of effective sterilization of ultrathin fibers based on polyhydroxybutyrate (PHB) by the ozone treatment was considered. The purpose of this work was to establish the interrelation between changes in the ES process and accompanying changes in the supramolecular structure, morphology, physical and mechanical properties of the fibrous materials based on PHB.

This paper is devoted to the evaluation of composite materials and components using ultrasonic visualization of structural changes caused by the external force. It is proposed to measure the strain of a sample under load using digital correlation of images recorded by a scanning acoustic microscope. An algorithm for processing the spatio-temporal ultrasonic data is developed to measure the longitudinal and transverse strains versus the applied force. The four-layer carbon fiber-reinforced composites with alternating packing of fibers (90/45) are evaluated by the proposed method. The relationships between the strains and the applied force are obtained up to the destruction of the sample. It is shown that the maximal longitudinal and transverse strains achieved for the test sample are 1.2% and 0.3%, respectively.

It is found that a ceramic based on zirconia modified with oxides of yttrium and ytterbium (Yb–TZP) maintains high mechanical properties after hydrothermal treatment, equivalent to 20 years of residence of an implant in vivo. The study of the surface of ceramic samples before and after hydrothermal treatment by atomic force microscopy is carried out. The change in the grain composition of the microstructure of this ceramic is shown, defined by subsurface change in the phase composition caused by martensitic transformation of zirconia.

Elastic properties and internal structure of glass-ceramic, feldspatic ceramic, PMMA and hybrid blocks for chairside CAD/CAM dental crowns were assessed by pulsed acoustic microscopy. Elastic modulus of hybrid ceramic was 1.5 times inferior to feldspatic ceramic and glass-ceramic but almost 10 times higher than those of polymer samples. We found the presence of pores from a few to hundreds of microns in the bulk of inorganic materials samples, isolated point defects were revealed in polymer materials while in hybrid material defects were not found.Методом импульсной акустической микроскопии проведена оценка упругих свойств и внутренней структуры стеклокерамических, полевошпатных, полиметилметакрилатных и гибридных блоков для CAD/CAM изготовления зубных коронок методом chairside. По модулю упругости показатели гибридной керамики в 1,5 раза и более уступают полевошпатной и лейцитной керамике, но почти в 10 раз превышают показатели полимерных образцов. Выявлено наличие пор величиной от нескольких до сотни микрон в толще образцов из неорганических материалов; в полимерных материалах визуализированы единичные точечные дефекты, в гибридном материале дефектов обнаружено не было.

The paper introduces the methods with time-resolved technique and isosurface display technique to get two- and three-dimensional (3D) acoustical imaging for scanning acoustic microscopy. Time-resolved technique presents the way to realize two-dimensional (2D) acoustical imaging - A- (O-), B- and C-scan, and a discrete combinatorial 3D image; and isosurface display technique realizes a 3D image with continuous distribution in full direction. The paper proposals a transitional model of square column, which consists of the data of echo signal pattern extracted from volume database, to construct the imaging cube and depict an isosurface using isovalue of internal boundaries in the cube, for the evaluation of internal defects in bulk specimen - Boron Nitride. 3D acoustical imaging has the advantage to show the position, size, appearance, distribution, and tendency of internal structures (voids, inclusions and defects) with complex shapes in non-transparent bulk material. The results show that 3D acoustical visualization presents more affluent, overall and intuitive pattern than 2D imaging for micro-sized structure investigation.

We have produced the samples of Bi2Te3-based nanostructured thermoelectric (TE) alloys by the method of high energy mechanotreatment from the mixture of the nano- and micro-sized powders (ball milling) followed by two methods of bulk samples preparing: (a) by the method of hot pressing sintering (HPS) and (b) by the method of spark plasma sintering (SPS). The microstructure of the obtained pellets was investigated by methods of acoustic and optical microscopy. With the crack/pore detection in acoustic microscopy images we marked that spot and cut the pellet through that spot perpendicular to the pellet's plane. The cut section, after polishing and etching, was examined on Olympus BX-51D microscope. The obtained pictures for the HP sintering samples shows, that the planes of all macro- and of micro-cracks are oriented perpendicularly to the axis of the load of the pellet. By using acoustic microscopy we investigate cracks and pores distributions in bulk of nanostructured Bi0.4Sb1.6Te3 alloy sintered by HPS and SPS methods.