Foreign Inclusions Research Articles

Status of 3" 6H SiC Bulk Crystal Growth

In this paper, we report on the current status of our technology for the commercial production of 3” 6H-SiC substrates, including PVT growth [1] of more than 3” diameter and up to 20 mm long 6H-SiC boules, post-growth processing of the boules, and characterization of the produced wafers. We discuss the preparation of SiC sources and seeds, the initial transient stage of the growth, the distribution of temperature in the growth crucible, and the Si/C ratio in the vapor. Special attention is given to the rise of the process stability and the reduction of crystallographic defects, including micropipes (open core screw dislocations), low-angle grain boundaries, foreign polytype inclusions, and graphite inclusions [2,3].

Modeling of partial closure of cracks in a perforated isotropic medium reinforced by a regular system of stringers

A mathematical model of partial closure of a crack in a perforated isotropic medium with a system of rectilinear foreign inclusions is constructed. Such a medium can be interpreted as an unbounded plate reinforced by a regular system of ribs whose cross sections are shaped as narrow rectangles. The medium is assumed to be attenuated by a periodic system of circular holes and straight-line cracks. Determination of unknown contact stresses and contact zone sizes is reduced to solving a singular integral equation, which is transformed by an algebraization procedure to a system of nonlinear algebraic equations solved by the method of consecutive approximations.

Micropipe absorption mechanism of pore growth at foreign polytype boundaries in SiC crystals

Formation of pores at foreign polytype boundaries in bulk SiC crystals is studied by means of synchrotron radiation phase-sensitive radiography, optical and scanning electron microscopies, and color photoluminescence. It is demonstrated that pores are formed through coalescence of micropipes and extend along the polytype boundaries by means of micropipe absorption. A theoretical model is suggested, which describes the micropipe absorption by an elliptic pore nucleated at the boundary of a foreign polytype inclusion. It is shown that depending on the inclusion distortion, the pore can either be a separate micropipe, or grow up to a certain length, or occupy the whole facet of the inclusion.

Numerical simulation of a multi‐contact detection technique for foreign particles in closed food containers

AbstractIn the presented work the basis of a novel method for detecting foreign solid inclusions in closed glass bottles and cans containing liquid food are presented. The new method is based on an automatic recording and analysis of multi‐contact oscillatory signals of the food‐container‐particle (F‐C‐P) system. In this work, two different active mechanisms for positioning the foreign particles next to the wall of the bottle are studied and relevant numerical simulations are presented. In the first case, a bottle filled with water moves linearly with constant acceleration, while in the second case the bottle rotates around its longitudinal axis at a constant angular velocity. The obtained numerical results permit the selection of optimal locations for the detection system components. (© 2009 Wiley‐VCH Verlag GmbH & Co. KGaA, Weinheim)

Interaction of cracks with bonds between their faces in an isotropic medium reinforced by a regular system of stringers

A problem of an elastic isotropic medium with a system of foreign (transverse with respect to crack alignment) rectilinear inclusions is considered. The medium is assumed to be attenuated by a periodic system of rectilinear cracks with zones where the crack faces interact with each other. These zones are assumed to be adjacent to the crack tips, and their sizes can be commensurable with the crack size. Interaction between the crack faces in the tip zone is modeled by introducing bonds (adhesion forces) between the cracks with a specified strain diagram. The boundary-value problem of the equilibrium of a periodic system of cracks with bonds between their faces under the action of external tensile loads and forces in the bonds is reduced to a nonlinear singular integrodifferential equation with a kernel of the Cauchy kernel type. The condition of critical equilibrium of the cracks with the tip zones is formulated with allowance for the criterion of critical tension of the bonds. A case of a stress state of the medium containing zones where the crack faces interact with each other is considered.

In-Service Flaw Detection and Quantification in the Composite Structures of Aircraft

In-Service Flaw Detection and Quantification in the Composite Structures of Aircraft Taking into consideration the increased usage of composites for aircraft structures there is a necessity for gathering information about structural integrity of such components. During the manufacturing of composites as well as during in service and maintenance procedures there is a possibility for damage occurrence. There is a large number of failure modes which can happen in such structures. These failure modes affect structural integrity and durability. In this work modern approach for detection of composites damage detection such as: delaminations, disbonds, foreign object inclusion and core damage has been presented. This detection is possible with the use of advanced P-C aided Non Destructive Testing methods. In the article nondestructive testing results for the composite vertical tail skins on MiG-29 aircraft will be delivered as well as some results of F-16 horizontal stabilizer and W-3 helicopter main rotor blades. Moreover some results of the composite honeycomb and sandwich structures will be presented based on the materials used in the construction of gliders and small aircraft. Factors affecting structural integrity and durability of the composites will be highlighted as well as necessity of the inspection with the use of modern NDT techniques. At the end some effort with Structural Health Monitoring connected with possibility of condition monitoring of composites will be presented.

'Me cae que no me entiendes': Multi-Language Text in the Mexican Onda

This study examines multi-language texts in the body of the works of the Mexican Onda movement (1964–1971). The aim of the study is to analyse foreign language inclusions from a transcultural perspective. The inclusions to be considered are words and phrases in foreign languages (used in their original form or in translation), and quotations from contemporary pop and rock songs (both original and in translation). By applying a number of theories, such as hermeneutics, transcultural hybridity, and diasporic writing, the study will determine the purpose of such inclusions as part of a complex linguistic coding used in the Onda works. The system of closed codes created by the Onda may appear elitist because it limits the readership of the texts to those who are knowledgeable enough to understand the hidden meaning of the texts. This study argues that the seemingly elitist nature of the Onda is an attempt at bridging the gap between high (mainstream) and low culture (subculture) by challenging the constraints of cultural dominance. This challenge is based upon the rejection of a canonical high cultural framework and its replacement with a transcultural reference system.

Elasticity polarization tensor, surface enthalpy, and Eshelby theorem

In a three-dimensional anisotropic elastic space with either a bounded foreign inclusion or a void, we derive asymptotic formulas for the increment of the polarization tensor of a defect caused by a smooth variation of the defect boundary. The formulas involve weighted integrals of jumps of the surface enthalpy evaluated for solutions to the problem about deformation of an unperturbed composite space by constant stress at infinity. The study of the positiveness/negativeness of the polarization matrix increment leads to inferences with a clear physical interpretation, in particular, for elastic solids admitting phase transitions. For homogeneous ellipsoid shaped inclusions we derive a relation between the polarization tensor and the Eshelby tensor and obtain miscellaneous consequences of this relation as well. In particular, we introduce the notion of the link tensor which is symmetric and positive definite for any elastic properties of homogeneous materials of the composite space. Bibliography: 60 titles. Illustrations: 5 figures.

Microscopic studies on imperfections in selected YAB single crystals

AbstractThe as‐grown surface and inner structures of undoped and Nd3+‐, Cr3+‐, V3+‐, Ce3+‐, Er3+ and Yb3+ – and (Er3+ + Yb3+) – doped yttrium aluminum borate (YAB) single crystals grown from (K2Mo3O10 + B2O3) flux by spontaneous crystallization or top seeded solution growth (TSSG) technique, were investigated using optical and scanning electron microscopic and analytic chemical methods. Fine and rough growth hillocks of dislocational origin, growth layers, traces of inner planar defects and foreign phase crystalline debris were found and analyzed on the as‐grown faces of crystals. Irregular grains and regular block structures and foreign phase inclusions were observed and studied in the interior of the crystals. The chemical compositions measured by energy dispersive X‐ray spectrometry on perfect and imperfect micro regions are compared with those obtained by flame atomic absorption spectrometry on bulk crystals. (© 2009 WILEY‐VCH Verlag GmbH & Co. KGaA, Weinheim)

Kinetics of dissolution of phases upon deformation of nanostructured metals and alloys

The kinetic features of dissolution of foreign inclusions in the bulk of nanostructured metals upon plastic deformation have been discussed. It has been shown that the rate of dissolution of inclusions substantially depends on the character of structural transformations in the subsystem of intercrystallite boundaries of nanomaterials. Equations that determine the kinetics of dissolution of chemical compounds of metals depending on the rate of structural transformations in intercrystallite boundaries upon deformation have been obtained. The behavior of the kinetic curves of dissolution has been described qualitatively. Numerical estimates of the time of dissolution of inclusions Fe3C and Fe2B in steels are given which are in satisfactory agreement with experimental data on the mechanical alloying of iron with nonmetals in ball planetary mills.

STRUCTURE AND PROPERTIES OF EPITAXIAL THIN FILMS OF Bi2FeCrO6: A MULTIFERROIC MATERIAL POSTULATED BY AB-INITIO COMPUTATION

ABSTRACT Experimental results on Bi2FeCrO6 (BFCO) epitaxial films deposited by laser ablation on SrTiO3 substrates are presented. It has been theoretically predicted using first-principles density functional theory that BFCO is ferrimagnetic (with a magnetic moment of 2μB per formula unit) and ferroelectric (with a polarization of ∼ 80 μ C/cm2 at 0K). The crystal structure investigated using X-ray diffraction shows that the films are epitaxial with a high degree of crystallinity. Chemical analysis carried out by X-ray Microanalysis and X-ray Photoelectron Spectroscopy indicates the correct cationic stoichiometry in the BFCO layer, namely (Bi:Fe:Cr = 2:1:1). Cross-section high-resolution transmission electron microscopy images together with selected area electron diffraction confirm the crystalline quality of the epitaxial BFCO films with no identifiable foreign phase or inclusion. The multiferroic character of BFCO is proven by piezoresponse force microscopy (PFM) and magnetic measurements showing that the films exhibit ferroelectric and magnetic hysteresis at room temperature. The local piezoelectric measurements show the presence of ferroelectric domains and their switching at the sub-micron scale.

Application of a new image segmentation method to detection of defects in castings

X-ray-based inspection technique is well applied to identification and evaluation of internal defects in castings, such as cracks, porosities, and foreign inclusions. Combining X-ray inspection with digital image processing and automatic image assessment is now the preferred approach for the continuous inspection of castings. However, in practical application, the quality of the X-ray image is poor. Under the circumstances, many classical thresholding methods usually cannot obtain ideal segmentation results. In this paper, we propose an effective segmentation method for the detection of typical internal defects in castings derived for an X-ray inspection system. The proposed method takes advantage of the fuzzy set theory and bound histogram and presents fuzzy exponential entropy for object and background according to the fuzzy sets and gray-level distribution of the image. The ideal threshold is obtained by maximizing the fuzzy exponential entropy associated with the distribution of the object and background classes in the bound histogram. Experimental results indicate that the proposed method is a powerful method to analyze images derived from X-ray inspection for automatically detecting typical internal defects in castings.

Photothermocapillary method for detecting foreign inclusions in solids under paint and varnish coatings

It is shown that the thermocapillary effect induced by laser radiation in a thin layer of silicon oil on a horizontal surface of a solid sample can be used for detecting foreign inclusions (cylindrical sleeves) hidden under paint and varnish coatings.

Energy-minimizing inclusion in an elastic plate under remote shear

A single foreign inclusion perfectly embedded in an elastic plate is considered as a bimaterial setup for finding the interface shape that minimizes the energy increment in a homogeneous shear stress field given at infinity. While simple in concept, this optimization problem is very hard computationally. For tractability, we limit our focus to a narrowed set of curves which can be conformally mapped onto a circle by an analytic function with only one nonzero Laurent term. The resultant one-parameter shape optimization problem with an integral objective functional is then accurately solved using an enhanced complex variable approach. This scheme, though seemingly restrictive, provides good qualitative insight into the optimal solution and bridges the gap between the limiting cases of the energy-minimal hole and the rigid inclusion solved previously.

Foreign Body Inclusion Cyst of the Nasal Radix after Augmentation Rhinoplasty

Development of a cystic mass on the nasal dorsum is a very rare complication of aesthetic rhinoplasty. Most reported cases are of mucous cyst and entrapment of the nasal mucosa in the subcutaneous space due to traumatic surgical technique has been suggested as a presumptive pathogenesis. Here, we report a case of dorsal nasal cyst that had a different pathogenesis for cyst formation. A 58-yr-old woman developed a large cystic mass on the nasal radix 30 yr after augmentation rhinoplasty with silicone material. The mass was removed via a direct open approach and the pathology findings revealed a foreign body inclusion cyst associated with silicone. Successful nasal reconstruction was performed with autologous cartilages. Discussion and a brief review of the literature will be focused on the pathophysiology of and treatment options for a postrhinoplasty dorsal cyst.

Goodayia Rostellatum Gen. N., Sp. N. (Protozoa) - A Monothalamous Foraminiferan from the Black Sea

Goodayia RostellatumGen. N., Sp. N. (Protozoa) - A Monothalamous Foraminiferan from the Black SeaGoodayia rostellatumgen. n., sp. n. (Protozoa) - a Monothalamous Foraminifera from the Black Sea. Sergeeva N. G., Anikeeva O. V.-Goodayia rostellatumgen. n., sp. n. is described from the open slope of the Black Sea along the northwestern part of the Crimean Peninsula (160 m water depth). The test of this very delicate, organic-walled, monothalamous (single-chambered) foraminifer is elongated and becomes wider from the middle to the apertural end. Test wall consists of two layers, and the protoplasm is separated from the inner layer by a more or less distinct space. The protoplasm is finely granular, homogeneous, without foreign inclusions. The single terminal apertural structure has an asymmetric, beak-like shape with the aperture located under the beak. The nucleus is situated more or less in the middle of the test. The shape and size of the test, the presence of two membranes, and the single terminal aperture are the features reminiscent of the generaGloiogullmiaandRhynchogromia.However, the new genus has significant differences from these taxa, notably the absence of any foreign mineral or organic particles adhering to the test wall, and the beak-shaped apertural structure.

Mechanism initiated by nanoabsorber for UV nanosecond-pulse-driven damage of dielectric coatings

A model of plasma formation for UV nanosecond pulse-laser interaction with SiO(2) thin film based on nanoabsorber is proposed. The formalism considered the temperature dependence of band gap. The numerical results show that during the process of nanosecond pulsed-laser interaction with SiO(2) films, foreign inclusion absorbing a fraction of incident radiation heats the surrounding host material through heat conduction causing the decrease of the band gap and making the initial transparent matrix into an absorptive medium around the inclusion. During the remainder pulse, the abosorbing volume of the host material is effectively growed and lead to the formation of the damage craters. We investigated the experimental damage craters and compared with theoretical prediction. The pulselength dependence of damage threshold was also investigated.

Potential fields caused by point sources in regions with apertures and foreign inclusions

A semi-analytic approach is developed for obtaining potential fields generated by point sources in regions embedded with foreign inclusions and containing holes of various shape. This study promotes an extension of the range of effective implementation of the Green's function version of the boundary integral equation method in mechanics of contemporary materials. Equivalents of Green's functions are obtained to boundary-contact value problems posed for Laplace equation on piecewise homogeneous multiply connected regions. Dirichlet, Neumann and Robin boundary conditions can be imposed on the outer boundary of the region and on contours of the apertures, while the ideal contact conditions are assumed on the interfacial contours. Source points could be located either outside or inside the inclusion. A Green's function modification of the method of functional equations is applied. A number of illustrative examples included to show the potential of the approach.

Fracture of an isotropic medium strengthened with a regular system of stringers

An isotropic medium containing a system of foreign transverse rectilinear inclusions is considered. Such a medium can be interpreted as an infinite plate strengthened with a regular system of ribs (stringers) whose cross section is a very narrow rectangle. The medium is weakened by a periodic system of rectilinear cracks. The action of the stringers is re placed by unknown equivalent concentrated forces at the points of their connection with the medium. The boundary-value problem on equilibrium of the periodic system of cracks under the action of external tensile forces is reduced to a singular integral equation, from the solution of which the stress in tensity factors are found. The condition of limiting state of equilibrium of the cracks is formulated based on a criterion of brittle fracture. The stress state in the case where crack faces come into a partial contact is also considered.

Epitaxial Bi2FeCrO6 multiferroic thin films

We present experimental results on Bi2FeCrO6 (BFCO) epitaxial films deposited by laser ablation directly on SrTiO3 substrates. It has been theoretically predicted by Baettig and Spaldin [Appl. Phys. Lett. 86 012505 (2005)], using first-principles density functional theory, that BFCO is ferrimagnetic (with a magnetic moment of 2 µB per formula unit) and ferroelectric (with a polarization of ∼80 µC/cm2 at 0 K). The crystal structure has been investigated using X-ray diffraction, which shows that the films are epitaxial with a high crystallinity and have a degree of orientation depending on deposition conditions determined by the substrate crystal structure. Chemical analysis, carried out by X-ray microanalysis and X-ray photoelectron spectroscopy (XPS), indicates the correct cationic stoichiometry in the BFCO layer, namely (Bi:Fe:Cr = 2:1:1). XPS depth-profiling revealed that the oxidation state of Fe and Cr ions in the film remains 3+ throughout the film thickness and that both Fe and Cr ions are homogeneously distributed throughout the depth. Cross-section high-resolution transmission electron microscopy images plus selected area electron diffraction confirm the crystalline quality of the epitaxial BFCO films with no identifiable foreign phase or inclusion. The multiferroic character of BFCO is demonstrated by ferroelectric and magnetic measurements showing that the films exhibit ferroelectric and magnetic hysteresis at room temperature. In addition, local piezoelectric measurements carried out using piezoresponse force microscopy (PFM) show the presence of ferroelectric domains and their switching at the sub-micron scale.