Fine Inclusions Research Articles

Fine SiC inclusions and grain boundary phases in pressureless sintered SiAlON

Abstract The starting powder, synthesized by carbothermal reduction, was pressureless sintered at temperatures over 1670°C to produce a dense SiAlON (Si 6−z Al z . O z N 8−z ) of z = 0·5. The dense material was characterized by X-ray diffractometry (XRD), scanning electron microscopy (SEM) and analytical electron microscopy (AEM), showing a microstructure featuring 1 μm, equiaxed, β′-grains bonded with a glassy phase. Fine SiC grains, 10–50 nm in size, were identified as inclusions in β′-SiAlON grains or at the grain boundaries. α′-SiAlON grains or whiskers which alloyed with Y and Ca were occasionally found in sizes less than 0·5 μm located in glassy pockets at grain boundaries or on the oversintered surface. Several other phases, normally non-detectable from XRD spectra, were found at grain boundaries by TEM, including yttrium-aluminum garnet (YAG), (Fe,Zr) Si x′ amorphous SiO x and elemental Si. The formation of SiC and other grain boundary phases is primarily due to the reducing atmosphere, chemistry of the matrix and neighboring glassy phase.

Widespread aluminium deposition in extracerebral organ systems of patients with dialysis-associated encephalopathy.

We have described new silver-staining methods for the demonstration of lesions in senile dementia of the Alzheimer type. The same procedure was used to visualize characteristic aluminium (Al)-containing inclusions in choroid epithelium, glia and neurons of the central nervous system in dialysis-associated encephalopathy (DAE). Here we describe the patterns and degree of Al deposition in extracerebral tissues of 12 DAE autopsy cases. Light microscopy of silver-stained paraffin sections demonstrated autonomic ganglion cells filled with numerous intracytoplasmic black-stained fine granular inclusions, which were also seen in endocrine tissues (pituitary, parathyroid and adrenal) and in Leydig cells. Heart, liver cells and the testicular tubules were involved, but decalcified bones, haematopoetic elements, hyperplastic epithelium and one case of malignant epithelium lacked inclusions. Laser microprobe mass analysis revealed prominent Al-related mass signals within the en-bloc silver-stained inclusions which were seen at low intensity in adjacent non-stained structures. Electron microscopy demonstrated accumulations of small electron-dense granules intermingling with lipopigments.

Application of transient elastic waves to the nondestructive evaluation of plate structure with cavity or inclusion

This paper utilized the heterogeneous finite difference formulation to study the propagation of transient elastic waves in media with internal interfaces due to a steel ball impact. The media considered in this paper include a parallel layered half‐plane, a dipping layered half‐plane, and a plate with a hole or circular inclusion. Transient elastic waves generated by dropping a steel ball on the layered (both parallel and dipping) plates are recorded to check the validity of the results simulated from the present numerical scheme. In order to detect a void or inclusion in a plate structure, the near‐offset seismogram and point‐source/array‐receiver (PS/AR) seismogram are simulated numerically. The simulated results of the near‐offset seismogram suggested that the bottom‐reflected P wave can be utilized to estimate the diameter of a circular inclusion. The unique features in the PS/AR seismogram suggested that the PS/AR seismogram can be utilized to identify a void or inclusion in plate structures. In combination with recent laser ultrasound developments, the present study can also serve as a basis for the detection of fine voids or inclusions in materials.

High activation energy for TAFF and pinning by fine inclusions in melt textured Y/sub 1/Ba/sub 2/Cu/sub 3/O/sub 7- delta /

In Bridgman melt-textured Y/sub 1/Ba/sub 2/Cu/sub 3/O/sub 7- delta / (YBCO) the activation energy, U/sub 0/, for thermally activated flux flow (TAFF) has been found to be almost four times higher than in conventional sintered bulk material by measuring rho (T, B) curves. One reason could be very fine inclusions with an average diameter of 35 nm and associated dislocations. An estimation of core pinning by these fine particles yields critical current densities, j/sub c/, at 1 T of 4.8*10/sup 4/ A/cm/sup 2/ and 2*10/sup 5/ A/cm/sup 2/ for 77.3 K and 4.2 K, respectively. This calculated current density is on the same order of magnitude as the j/sub c/,/sub Delta M/ value estimated from M(B) measurements at 4.2 K and 1 T, but at 77.3 K and 1 T the calculated current density is about one order of magnitude higher than the j/sub c/,/sub Delta M/ value. The lower critical current density at 77.3 K could be caused by TAFF or oxygen deficient regions near the small angle grain boundaries, which become normally conducting at high fields and temperatures.< <ETX xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">&gt;</ETX>

石英の変形・再結晶と水

Quartz grains within granitic mylonite from the Median Tectonic Line (MTL) contain significant amounts of water (from 2500 to 10500 ppm) with IR signatures. Most of this water is freezable, and may differ from those within natural vug-grown quartz and synthetic single crystals. Quartz grains in strongly sheared mylonites may contain large number of fine (less than 500 nm in diameter) inclusions along dislocations which bear a resemblance to bubbles developped within heat-treated wet synthetic quartz. This water within extremely fine inclusions may be effective for the hydrolytic weakening of rocks within the earth's crust.

Ultrastructural and Cytochemical Study of the Odontoclasts in Physiologic Root Resorption of Human Deciduous Teeth

Using extracted human deciduous teeth undergoing physiologic root resorption, this author studied the ultrastructural and cytochemical features of odontoclasts. The scanning electron microscopic observation of trypsin-treated dentin and cementum surfaces of resorption lacunae showed the exposure of collagen fibrils and prominent loss of the peritubular matrices around the dentinal tubules. In the resorption lacunae formed in enamel, there was dissolution of either the rod or the interrod regions. The odontoclasts developed extensive ruffled borders apposed to these resorbing matrices and had round phagosomes containing tannic acid-stainable fine amorphous inclusions, which were identical to those in the extracellular canals of the ruffled borders. The odontoclasts did not phagocytose the collagen fibrils. The odontoclasts showed the enzymatic activities of the acid trimetaphosphatase and acid p-nitrophenyl phosphatase (p-NPPase) in the Golgi-lysosome system, the ruffled border region, and along the resorbing dentin surfaces. The p-NPPase activity was inhibited by sodium tartrate. Also, the odontoclasts showed H(+)-K(+)-ATPase activity in the cytoplasm along the plasma membranes including those of ruffled border and the limiting membranes of the lysosomes. These results suggest that: 1) the odontoclasts are associated with resorption of non-collagenous organic matrices and/or extracellularly-degraded collagenous fragments rather than the incorporation of intact collagen fibrils; 2) the odontoclasts release the hydrolytic enzymes onto the lacunal surfaces and/or the lysosomes for the extra/intracellular degradation of the organic matrices; and 3) they also have H(+)-K(+)-ATPase for extracellular demineralization of the inorganic crystals.

Study of underwater welding using a modified gravity technique

Abstract A modified gravity arc welding installation has been used to study underwater welding and the weld metal characteristics under simulated laboratory conditions. The constant deposition of metal per unit length of the weld, independent of the electrode consuming rate, could be controlled by a given electrode leading angle. X‐ray radiographie inspection revealed that only few detectable defects, in addition to undercuts, were presented in the underwater welds. Fractographic observations have shown that many fine inclusions existed; however, microcracks and microvoids were rather few in the deposit. Microcracks, if any, generally propagated along the columnar grain boundary ferrite and arrested in the region of acicular ferrite. The correlations between fracture and microstructure have indicated that the grain boundary ferrite and associated Widmanstätten side plates induced the brittle fracture, while acicular ferrite led to a ductile type of failure.

Microimaging and off-line microscopy of fine particles and inclusions

Characterization of large numbers of fine particles or inclusions is of increasing importance to assist in (1) evaluating metal or ceramic powders as candidates for compaction or use in composite materials, (2) monitoring environmental effects of particles produced in manufacturing processes and (3) identifying trace contaminants in engineering materials. These properties are best studied by either optical or electron microscopy, but a need to describe them in statistically significant terms places a burden on manual microscopy techniques. A technique called computer-controlled scanning electron microscopy (CCSEM) was developed in the late 1970s to overcome operator bias and to characterize large numbers of individual features by size, shape factor and elemental composition in a short period of time. An advancement of CCSEM technology, microimaging, is a technique used to collect images in an automated manner during a CCSEM analysis. This paper discusses recent advances in CCSEM and personal computer technology which make possible the collection and storage of images during CCSEM analysis.

Fatigue crack initiation and propagation in smooth specimens of polycarbonate.

Fatigue tests of a push-pull loading were carried out on the smooth specimens of polycarbonate at the speed of 2Hz at room temperature. The roles of very small inclusions and shear bands in the initiation and growth of fatigue crack on the surface of specimen were investigated. This is accomplished by careful successive observations by using the replica of cellulose methyl ether. It was found that the initiation of the surface crack appeared from the fine inclusions near the surface of specimens at 20-30% of the fatigue life, and that the surface crack from these inclusions was hindered by the shear bands that formed at their ends. The final length of surface crack is strongly influenced by the stress amplitude. The characteristic behaviors of the crack initiation and growth on the surface of the smooth specimens of polycarbonate were discussed in terms of the mechanical properties and yield behavior of the material.

Localization of woodchuck hepatitis virus in the liver.

Localization of woodchuck hepatitis virus in liver tissue from 10 infected woodchucks was investigated immunohistochemically and ultrastructurally. Woodchuck hepatitis virus surface antigen was detected by immunoperoxidase methods in the cytoplasm of hepatocytes with a fine granular and/or inclusion body appearance. Woodchuck hepatitis virus surface antigen positive hepatocytes were often found in the peripheral zone of hepatic lobules. In contrast to human hepatitis B core antigen, woodchuck hepatitis virus core antigen was observed only in the cytoplasm of hepatocytes, but not in the nuclei. In hyperplastic foci, woodchuck hepatitis virus antigen-positive hepatocytes were found in 3 of 8 animals. Furthermore, in 1 of 5 animals with hepatocellular carcinoma, woodchuck hepatitis virus surface antigen and woodchuck hepatitis virus core antigen were present in carcinoma cells. Electron microscopic examination revealed many filamentous structures (18 to 20 nm in diameter) in the cisternae of the endoplasmic reticulum. Noncoated core particles (18 to 20 nm in diameter) were found in the cytoplasm of the hepatocytes, but not in the nuclei. The coated particles (42 to 45 nm in diameter) were observed in the cisternae of the endoplasmic reticulum. These coated particles were shown to be morphologically identical to the virus particles in serum. These results indicate that woodchuck hepatitis virus core antigen is produced and assembled mainly in the cytoplasm of hepatocytes, and seems to be rapidly assembled into virion. The similarity of woodchuck hepatitis virus infection to human hepatitis B virus infection makes the woodchuck an excellent experimental model for the study of hepadna virus oncogenesis.

Monoclonal antibodies against individual cytokeratins in the detection of metastatic spread

A panel of 17 monoclonal antibodies (MAbs) recognizing various keratin polypeptides has been used to define their binding on non-epithelial elements in 28 bone-marrow samples and 14 lymph nodes, in order to establish their limitations for use as a possible tool for immunodiagnosis of carcinoma spread. Immunocytochemical studies have shown that only 8 antibodies consistently exhibited no false-positive staining of marrow cells. All the remaining MAbs labelled (mostly in a non-specific manner) a few cells of marrow samples derived from patients with either haematological disorders or malignant lymphomas. Fine granules and droplet-like cytoplasmic inclusions were predominant patterns of positive reactions. Homogeneous cytoplasmic staining reminiscent of specific keratin immunolabelling was occasionally seen as well. The positive cells could be also identified in some lymph nodes free of tumour infiltration. All antibodies visualized cytoplasmic droplets in scattered cells of lymph nodes taken from a patient with non-Hodgkin lymphoma. This type of positivity was mostly associated with positive histochemical reactions for iron. Quite significant was the detection of fibrillar positivity in the extrafollicular reticular cells in all nodes examined. Such a specific type of staining was exclusively induced by antibodies directed against epitopes of keratin 8 and 18, whereas those MAbs recognizing keratin 7 and 19 always gave negative results. Our data indicate that caution is required when such MAbs, considered as markers of specific cell types, are being used as an immunodiagnostic tool to identify single carcinoma cells. A series of criteria, including morphological ones, must be utilized in order to obtain meaningful results.

Petrography of the migmatites from the High Dam Western Quarry, Aswan, South Egypt

The migmatites of the High Dam Western Quarry are part of a crystalline massif south of Aswan and comprise granitoid and trondhjemitic varieties. Both comprise leucocratic (leucosome) and melanocratic (melanosome) fractions. The granitoid migmatites are more abundant and their mineralogy is similar to that of biotite gneisses whereas that of the trondhjemitic migmatites is similar to that of the hornblende gneisses of Aswan. The migmatites show stromatic, ptygmatic and phlebitic structures. The plagioclase is normally zoned and usually carries fine inclusions of sphene, apatite and iron oxide that lie in planes parallel to the long axes or the twin planes of these plagioclase crystals. K-feldspar megacrysts show intensive perthitization of exsolution origin and some include xenomorphic quartz crystals between the idiomorphic cores and their outer rims. Porphyritic, myrmekitic, graphic and rapakivi textures are common in the migmatites. These features suggest crystallization of the leucosomes from silicate melts formed by partial melting in small closed systems in water-undersaturated conditions through high grade regional metamorphism up to the K-feldspar-sillimanite-almandine sub-facies.

On the singularities of contact forces in the bending of plates with fine inclusions

A number of problems on the bending of plates with thin inclusions that are distinguished by the conditions at the inclusions is examined. The problems are reduced to systems of integral equations whose characteristic part has the following form in the general case ▪.

Strength of materials containing systems of fine inclusions

Strength of materials containing systems of fine inclusions

Interdiffusion in the Ta-W system

Interdiffusion in the Ta-W system, a continuous body-centered-cubic solid solution, has been investigated in the temperature range 1300–2100 °C with single-phase diffusion couples prepared by chemical vapor deposition. Fine inclusions, presumably oxides or carbides, decorated the couple interfaces and served as Kirkendall markers. The diffusion annealing times ranged from 16 h to 220 days. The resulting concentration profiles were measured with the electron microprobe and analytical electron microscope. The chemical diffusion coefficient was determined by the classical Boltzmann–Matano technique. The intrinsic diffusivities were determined by the technique of Darken. In the composition range 20–80 at. % W, the activation energy Q for chemical diffusion was constant at 130.5±1.5 kcal/mole. The activation energies for the intrinsic diffusion coefficients at the composition of the Kirkendall marker plane, approximately 70 at. % W, were Q(Ta)=132.3±0.5 kcal/mole and Q(W)=122.0±0.5 kcal/mole.

Integrodifferential equations of the three-dimensional problem of the theory of elasticity for a body with a system of fine inclusions

Integrodifferential equations of the three-dimensional problem of the theory of elasticity for a body with a system of fine inclusions

Structure, phase composition, and character of fracture of sintered TiC-NiTi composite materials

There exist three ranges of compositions of TiC-NiTi alloys, in which the sintering of the composites is controlled by different mechanisms: 0–30% NiTi, in which solid-phase sintering predominates; 40–60%, in which intense recrystallization through a liquid phase takes place; and 70–90%, which is characterized by a regrouping of carbide particles. The structure of the alloys consists of TiC, NiTi, and Ni3Ti phases. Fine Ni3Ti inclusions form during sintering as a result of titanium impoverishment of the NiTi brought about by directional migration of titanium atoms to carbide grains. Thus, TiC exerts a strong influence on the character of phase transformations in the NiTi binder of TiC-NiTi alloys. As the composition of the NiTi changes during sintering, the damping ability imparted to the binder by the martensitic transformation occurring in it during fracture deformation manifests itself only in alloys with ⩽ 30% TiC. The character of fracture of TiC-NiTi alloys depends on their binder content and microstructure. Alloys of low binder content with a heterogeneous structure fracture mainly along phase and grain boundaries. In alloys with ⩾70% NiTi fracture through the cementing phase predominates. The greatest plasticity is exhibited by an alloy with 70% NiTi, which is characterized by a homogeneous structure, a medium-sized grain (3–4 μm), and a superelastic state of its binder.

Ocular ultrastructural studies of two cases of the Hurler syndrome (systemic mucopolysaccharidosis I-H)

The ocular histopathology of Hurler syndrome (systemic mucopolysaccharidosis, type I-H), with emphasis on ultrastructural findings is reported in two cases. Numerous fine fibrillogranular inclusions were observed in: conjunctival fibrocytes; corneal epithelium, keratocytes and endothelium; uveal melanocytes and fibrocytes; ciliary epithelium; smooth muscle cells of ciliary body; pericytes; lens epithelium; retinal pigment epithelium; ganglion cells; and sclerocytes. Some multimembranous inclusions were noted in Schwann cells, keratocytes, trabecular endothelium, uveal fibrocytes and melanocytes, retinal ganglion cells, sclerocytes, optic nerve astrocytes, and vascular pericytes. Extracellular fibrillogranular material was present in the corneal stroma, Descemet's membrane, and scleral stroma. The extensive involvement of the ocular tissues of these two cases emphasizes Hurler syndrome as the most severe form of the systemic mucopolysaccharidoses.

The effect of steelmaking on the hydrogen attack of carbon steel

Four normalized carbon steels made in different ways (Si-killed, Al-killed, REM-treated, and electroslag refined) were studied to determine the role of differing fine inclusions on the early stages of hydrogen attack (HA). Hydrogen exposures were made at 450°C (6.5 MPa) and 375°C (7.6 MPa). The first stage of HA is shown to be the development of a closely spaced (1 to 2 µm) array of small bubbles over the ferrite/pearlite, or occasionally the ferrite/ferrite boundaries. These bubbles grew together to form tears, primarily in the rolling plane, leading to more rapid expansion normal to this plane than parallel to it. Fracture planes followed high solute layers in banded steel but only rarely if ever did the fine bubbles form on inclusions. At 450°C REM-treated steel was attacked the fastest and Al-killed steel required exposures two to four times as long for attack.

Effect of heat treatment on the plasticity of nickel alloys

1. The presence of >103 per cm2 of fracture surface of large colonies consisting of lamellar inclusions and a large number of fine lamellar inclusions in the boundaries of crystals lowers the plasticity and facilitates the development of high-temperature brittleness of alloys KhN75MBTYu and KhN78T. 2. Preliminary heating of alloy KhN75MBTYu with low plasticity at 750–1000° for 1–20 h does not remove high-temperature brittleness. 3. Heating at temperatures above 1000° leads to partial solution and coalescence of pellicular inclusions, resulting in an increase of the fracture toughness at room temperature.