Showing papers on "Texture (crystalline) published in 1972"

Diffusion of Impurities in Polycrystalline Silicon

Abstract: The diffusion of electrically active impurities into polycrystalline silicon deposited by the thermal decomposition of silane has been studied. Both boron and phosphorus have been found to diffuse more rapidly into polycrystalline silicon than into single‐crystal silicon. The diffusivity is greatest in films deposited at about 1000°C although this maximum is a function of the deposition rate, film thickness, and substrate material as well as the deposition temperature. The maximum diffusivity is associated with a structure which has the maximum {110} texture. Although most of the films have been deposited onto amorphous SiO2, a nucleating layer of polycrystalline silicon has been found to influence the diffusion of impurities into a thick layer of polycrystalline silicon deposited over the nucleating layer. An optimum structure is obtained with a nucleating layer containing maximum {110} texture. The enhanced diffusion is tentatively attributed to diffusion down defects in the polycrystalline silicon. The...

The Development of Rolling Textures in Low-Carbon Steels

Abstract: The crystallite orientation distribution analysis was applied to the study of the development of the rolling textures in low-carbon steels. It was found that the constraining effect of the grain boundary remarkably influences the rolling textures of polycrystalline iron. This enhances the crystal rotations, which would not be expected to occur in single crystals; and grains having the { 110 } 〈 112 〉 orientations are forced to rotate about the 〈 111 〉 axes lying in the sheet normal direction toward the { 110 } 〈 110 〉 orientations. This is the origin of the 〈 111 〉 fiber texture normally found in the rolling textures of low-carbon steels. The presence of the partial fiber texture having the 〈 111 〉 axes inclined 30 deg from the sheet normal toward the rolling direction could not be confirmed.

Preferred Orientation in Al2O3 Substrates

Abstract: The degree of preferred orientation (texture) of doctor-bladed polycrystalline 99.5% Al2O3 substrates from 3 sources was evaluated by qualitative optical and quantitative X-ray analyses. The substrates exhibit a fiber texture in which the basal planes lie preferentially in the plane of the substrate. The same texture is weakly evident in the unfired materials. The strength of the texture in fired substrates varies from lot to lot and among suppliers, but its character remains essentially the same. Measurements of dielectric constant, flexural strength, and thermal expansivity are consistent with the observed texture. The possible origins of the texture and its importance in substrate applications are discussed.

The texture transition in α-brasses determined by neutron diffraction

Abstract: Three-dimensional orientation distribution functions were calculated from (111), (200), (220) and (311) pole figures for α-copper–zinc alloys in the concentration range from 0 to about 30% zinc. The pole figures were measured by neutron diffraction. The main feature of the texture transition is a continuous shortening or cut off of the tube of preferred orientations present in the copper texture beginning with the end orientation ~(\bar 112) [1\bar 11]. This orientation has nearly completely disappeared at about 5% zinc. Simultaneously its twin orientation (011) [100] appears. A second feature is the continuous decrease of maximum density of all texture components over the whole concentration range. The results support Wassermann's theory of mechanical twinning as the reason for the texture transition.

The effect of crystallite shape on small-angle X-ray scattering

Abstract: Diffraction by a linear crystallite system was calculated to explain different shapes of small-angle reflections. The calculations show that various SAXS patterns observed can be obtained theoretically if the shape of certain crystallites are accounted for. Various reflection shapes can be explained chiefly by the changes in the crystallite shape and size. Dash, four-point and two-point reflections are associated with rectangular and oblique crystallite of small lateral dimensions. In the case of radial reflections the crystallite represents a plate and the fibril — a stack of plates. Structural changes in oriented samples with planar crystallite texture caused by shrinkage were studied. The principal process of shrinkage consists in the growth of lateral (with respect to the texture axis) crystallite dimensions and in their transformation into plates. Simultaneously the rotation of the macromolecule axis takes place. At the second stage of the shrinkage the layers twist around an axis perpendicular to the film plane. Then isotropic structure is formed. Transition between the two kinds of reflections are typical of various processes taking place in the course of polymer deformation and shrinkage.

The Spherical Sample Method in Neutron Diffraction Texture Determination

Abstract: Neutron diffraction proves advantageous as compared to X-ray diffraction in texture analysis because of the lower absorption coefficient for a broad variety of materials especially metals. The spherical sample method is recommended because it yields the most reliable results and it does not require great preparational efforts. The fundamental difference between the spherical sample method in X-ray and in neutron diffraction is discussed.

Tooth cleaning device

Abstract: A device adapted to be worn on the finger for cleaning the teeth, wherein the device has an outer surface provided with a fabric texture with the fabric being impregnated with a dentifrice material. The device has a tab at the open end thereof for facilitating the placement of the device on a finger.

Confined-growth crystallization of polyethylene

Abstract: A new typical orientation pattern of polyethylene has been observed in extruded, melt-drawn composites containing 10% polyethylene and 90% polystyrene. In these composites, the polyethylene phase is dispersed in the polystyrene matrix as thin, long ribbons (width 1000 A, thickness 500 A). The b axis of the crystallites is found oriented preferentially along the long dimension of the ribbons, i.e., in the extrusion direction. The a and c axes of the crystallites show no preferred orientation. This texture pattern is attributed to the fact that, in view of the small cross section of the polyethylene phase, crystallization can proceed only along the long axis of the ribbons. Since the b axis is the direction of fastest growth in polyethylene (and the radial direction in a spherulite), most polyethylene unit cells are oriented with their b axes in the long dimension of the ribbons.

Device for detecting anticholinesterase materials

Abstract: AN ARTICLE OF MANUFACTURE COMPRISING IN SUPERIMPOSED RELATIONSHIP, (A) A SELF-SUPPORTING LAYER, (B) A CELLULOSIC ELEMENT HAVING SULFITED POLYACROLEIN BOUND CHOLINESTERASE DISPERSED THROUGHOUT THE INTERSTICES THEREOF AND (C) AN ACTIVE CHOLINESTERASE FREE CELLULOSIC LAYER HAVING THE SAME PHYSICAL PROPERTIES OF COLOR AND TEXTURE AS THE CELLULOSIC ELEMENT (B) AFTER BOTH HAVE BEEN WETTED WITH BUFFER AND AN APPROPRIATE DETECTION SOLUTION.

Topographic Arrangement of Crystallite Orientations in Rolled Copper

Abstract: In single and polycrystalline copper rolled to a reduction of 95 %, the topographic arrangements of crystallite orientations were determined over large areas by means of electron microscopy. Correlated data on orientation, diffraction site, and transmission pictures in three cross-sections perpendicular to the normal, rolling and transverse directions were obtained and evaluated. These results were complemented by X-ray studies of the texture. The rolled polycrystalline structure consists of roughly disc-shaped regions of uniform orientation which are fairly strongly misoriented with respect to each other. The planes of the discs lie paral.lel to the rolling plane. Within these regions of uniform orientation lie elongated subgrains extended in the longitudinal and transverse directions. In a surface layer of a few microns thickness the dryly rolled single crystals have essentially a (100)[011] texture. This is independent of the orientation of the interior of the material. The observed structures are discussed with respect to possible formation mechanisms.

Assembly for press-forming sheet material

Abstract: A METHOD OF AND AN ASSEMBLY FOR PRESS-FORMING SHEET MATERIAL SUCH AS, FOR EXAMPLE, ASBESTOS-CEMENT SHEETS DISPLAYING A PREDETERMINED DEEP TEXTURED DESIGN IS DISCLOSED HEREIN. IN CARRYING OUT THE METHOD, A SLURRY OF THE SHEET MATERIAL IS PLACED IN AN OPEN MOLD COMPRISING PART OF A PRESS ASSEMBLY AND ON TOP OF A RESILIENT PAD POSITIONED WITHIN THE MOLD. A TEXTURED PLATE FASTENED TO THE TOP DIE FACE OF THE PRESS ASSEMBLY IS PROVIDED FOR APPLYING FORMING PRESSURE TO THE SLURRY SO AS TO CONSOLIDATE THE LATTER INTO SHEET MATERIAL DISPLAYING THE DESIRED TEXTURE. DURING CONSOLIDATION AND IN RESPONSE TO THE FORMING PRESSURE, THE AFORESTATED PAD IS DEFORMED TO PROVIDE SUBSTANTIALLY UNIFORM DENSITY TO THE SHEET MATERIAL.

Molecular Orientation Effects in Compensated Liquid Crystals

Abstract: An optical and a dielectric memory effect is observed in compensated mixtures of cholesteryl chloride and cholesteryl laurate. When the temperature is increased after a sufficiently high dc electric field is once applied and then reduced to zero at low temperatures, the liquid crystal becomes transparent and the dielectric constant becomes maximum at a temperature approaching the cholesteric to nematic phase transition temperature. This effect can be erased by heating up to an isotropic state. The phase transition from the homeotropic to the plane texture is observed by applying the high frequency electric field. The critical frequency depends upon the sample temperature and it varies from 3 kHz to 500 kHz as the temperature rises from 17°C to 50°C. These phenomena are discussed based on the orientation effects of liquid crystal molecules.

Cyclic Textures in Aluminium Wires

Abstract: Three-dimensional orientation distribution functions were calculated from neutron diffraction pole figures of unwound cylinders taken at different distances from the centre of cold drawn Al-wires. Their features change from the axially symmetric type at the very centre of the wire towards a texture near to the rolling type at the surface. Relations between the three-dimensional function and ordinary fibre texture pole figures were used to study the dependence of the textures on certain processing variables for cold drawn as well as recrystallized wires.

Texture Development in Ferritic Stainless Steel Sheet

Abstract: Two grades of ferritic stainless steels (495 and 410.types) containing about 13 % chromium have been processed by cold rolling with intermediate and final anneals. The development of textures has been followed and the plastic anisotropy of the annealed sheet has been assessed. Processing conditions for the development of anisotropy favourable for deep drawing applications have been defined for the 405 type stainless steel. The evolution of the favourable {554} 〈 225 〉 texture component appears to be progressive throughout the processing. It is particularly well-developed after two moderate cold rolling reductions of about 70 % and a final anneal at 850–900°C. Differences between the 405 and 410 steels have been attributed to differences present in the early stages of processing.

Epitaxy and fiber texture of Pb films on mica and glass.

Abstract: We report the production of (111) epitaxial Pb films on mica and (111) textured Pb films on mica and glass. Film structure is studied by reflection electron diffraction and by etching and optical microscopy. Thin (about 1000 A) epitaxial films are found to be doubly positioned. Reorientation during growth of thicker films leads to single positioning in areas several tenths of a millimeter across.

A field-ion microscopy study of chemically vapour deposited molybdenum and tungsten thin films

Abstract: Films of molybdenum and tungsten, 0–500 A thick have been chemically vapour deposited onto field-ion emitter substrates by the thermal decomposition of the appropriate hexacarbonyl. Epitaxial molybdenum films on tungsten substrates could be progressively field evaporated to reveal the interface. Molybdenum film structure and purity were found to be dependant on deposition temperature, previous substrate thermal rearrangement and vacuum conditions. Tungsten films on field evaporated molybdenum substrates were of high purity, epitaxial, and comparatively insensitive to deposition conditions whilst those on platinum were non-epitaxial but with a pronounced 〈211〉 texture.