Degree Of Crystallite Orientation Research Articles

Anisotropy of electromechanical properties of layered bismuth-containing ferroelectric ceramics with a high degree of texture

The features of the crystal structure, microstructure and electromechanical properties of textured ferroelectric ceramics based on solid solutions of the Na0.5Bi4.5Ti4O15–PbNb0.5Cr0.5O3 system have been studied. Textured ceramics were manufactured by uniaxial hot pressing method with varying sintering conditions. The degree of crystallite orientation in samples with polarization direction perpendicular and parallel to the pressure axis during hot pressing was evaluated using X-ray diffraction analysis (XRD) and scanning electron microscopy (SEM). Complex elastic, dielectric, and piezoelectric parameters of textured piezoceramics were measured and analyzed using PRAP iterative automatic method.

Enhanced oxygen barrier property of poly(ethylene oxide) films crystallite-oriented by adding cellulose single nanofibers

In this study, we investigated the influence of cellulose single nanofibers (CSNFs) added to poly(ethylene oxide) (PEO) on the microstructure and property to create high gas barrier films. The CSNF/PEO nanocomposite films were prepared by solvent casting. The PEO crystallite orientation was measured using wide-angle X-ray diffraction of the SPring-8 synchrotron radiation facility. The degree of crystallite orientation was evaluated from the reflections of the PEO (1 2 0) lattice planes to investigate quantitatively the effect of different amounts of the additive CSNFs. The crystallite orientation of PEO increased with the addition of the CSNF. Furthermore, the oxygen barrier property for each nanocomposite film was found to be higher than that of the pure PEO film. The 5 wt% addition of CSNFs was mostly effective in enhancing the PEO crystallite orientation and oxygen barrier.

Single fibre deformation studies of poly(p-phenylene benzobisoxazole) fibres

Changes in crystal strain and crystallite orientation of three varieties of PBO fibre (namely PBO AS, HM and HM+) have been investigated during deformation from the analysis of diffraction patterns obtained across single filaments, using a synchrotron X-ray source. Crystal strain was measured from the positions of the meridional reflections and orientation calculated from azimuthal broadening of the equatorial reflections. It has been demonstrated that no difference in crystal strain across the fibre exists, with the calculated strain being equal between fibre skin and core at a given level of stress. Further skin-core crystallite orientation analysis (calculation of the orientation parameter \(\left\langle {\sin ^2 \theta } \right\rangle\)) proved that the AS fibre was the only PBO variety with a significant difference in orientation across the fibre, with the core region being less oriented due to the processing conditions. The skin and core orientation of all three fibres was found to improve with deformation, with the core of the AS fibre showing a significantly higher rate of improvement. This resulted in a similar level of orientation for both skin and core regions of the PBO AS fibre at high levels of stress. The fibre modulus was found to increase with the increasing initial degree of crystallite orientation. Furthermore, improvement in orientation with external stress was related to \(\left\langle {\sin ^2 \theta } \right\rangle\)σ = 0, with higher values resulting in greater shear forces on the crystallites and therefore a greater rate of orientation improvement.

Influence of the sinter-forging temperature on the superconducting properties of Bi2223 textured discs

Using the sinter-forging method, we have obtained dense textured Bi2223 materials at a temperature between 835–850 °C in air. In this paper, we study the influence of temperature on the Bi2223 phase formation, the critical current density and the degree of crystallite orientation. Heat treatment conditions have been optimized around 845–850 °C where final pure Bi2223 and highly oriented discs are obtained. X-ray diffraction patterns have been correlated to magnetization and electrical measurements.

A Study on Solid Structure of Regenerated Cellulose Fibers Related with Fibrillation.

It is well known that the Cupro®, Polynosic and organic solvent span rayons, such as Tencel®, and Lyoce® fibers are easy to fibrillate. The Rayon fiber is difficult to fibrillate. We developed fibrillation-resistant Cupro(CUPRO2) by means of a new spinning method. In this study, we attempted to compare the solid structures of CUPRO2, Cupro (CUPROl), Rayon(RAYON) and Lyocel (LYOCEL) in order to discover the factors governing the fibrillation. To this end, WAXD, Dynamic viscoelastic analysis, and CP/MASS13 CNMR analysis were carried out. The measured fibrillation resistance grade was as follows: RAYON (95)>CUPRO2 (75)>CUPRO1 (40)>LYOCEL (10). Crystallinity index, degree of crystallite orientation, and apparent crystallite size estimated for the (1_??_0) plane decreased with increasing fibrillation resistance grade. The peak temperatures of α1 and α2 dispersion (Tmaxα1, Tmaxα2) measured from the mechanical loss tangent-temperature curve increased in order of the fibrillation resistance grade, that is to say, the inter-and intra-molecular hydrogen bonding seemed to increase with increasing fibrillation resistance grade. It may be concluded.that the fibrillation characteristic is greatly influenced by the degree and strength of inter-and intra-molecular hydrogen bonding in the amorphous region at the surface of the microfibril.

The Influence of Drawing on Solid Structure and Fibrillation Resistance of Cuprammonium Rayon(Cupro).

An attempt was made to clarify the influence of drawing on solid structure and the fibrillation tendency for cuprammonium rayon, as a model of regenerated cellulose fibers. The drawing was carried out for the gel-like fiber obtained after coagulation (drawing at coagulation) and at the regeneration process of the coagulated fiber (drawing at regeneration). In the case of drawing at coagulation, the fibrillation tendency, degree of crystallite orientation (fc), and birefringence (Δn) increased, and the peak temperature of α2 dispersion (Tmaxα2) and tanαvalue (tanαmaxα2), which are the parameters representing the density and the amount of the amorphous region, respectively, decreased with drawing ratio. On the other hand, for drawing at regeneration, only fc showed very low drawing ratio dependence, while the influence of drawing on other factors was same as the case of the drawing of coagulation. The coagulated fiber with constant length showed remarkable stress relaxation at regeneration process. From these results we considered that in the case of drawing at coagulation, both crystal and amorphous phases increased in their orientation degree by drawing, because of the presence of network structure formed by cellulose-copper (II) complex. During the regeneration, such network structure is cleaved by the sulfric acid, as a regeneration reagent. Therefore the crystallization occurs under less tension than that at coagulation process and the drawing at this process may mainly lead to the orientation of cellulose molecules in amorphous region. The drawing at coagulation and regeneration processes was inferred to make remarkable break-down of bondings between fibrils, which may results in an increase of fibrillation tendency.

Structure of high-density polyethylene obtained by hydrostatic extrusion in solid state

A number of structural characteristics were calculated from X-ray diffraction patterns for high-density polyethylene obtained by hydrostatic extrusion at 393 and 353 K: dimensions of crystallites and X-ray long periods, the degree of crystallite orientation, total and fibrillar degrees of crystallinity (both volume and mass), weight fractions of intra- and inter-fibrillar amorphous interlayers. With increasing extrusion draw ratio the microfibrils become thinner and fuse, until alternating amorphous and crystalline lamellae oriented perpendicularly to the axis of extrusion are finally formed with a certain fraction of interlamellar interconnecting bridges. The observed increase of modulus with extrusion draw ratio at a given temperature is at first due to enhanced orientation of crystallites and increasing crystallinity, but in the later stages is connected with uniform distribution of load on all fibrils and interlamellar bridges.

Effect of stress on the magnetostriction and magnetization of rare earth-Re<inf>1.95</inf>alloys

The magnetostrictions and magnetizations of highly magnetostrictive rare earth-Fe 1.95 alloys have been measured under compressive stress up to 48 MPa. The shape of the magnetostriction and magnetization curves depend upon the relative concentrations of Tb, Dy, and Ho and the degree of crystallite orientation.

Electron Diffraction Measurement of Degree of Crystallite Orientation in Native Cellulose Fibers

Electron diffraction techniques have been employed in the study of crystallite orientation within fibrils of cellulose removed from cotton and ramie fibers. It was found that the degree of orientation of crystallites within fibrils representing ten cotton varieties did not deviate appreciably from one another; however, the alpha angle determined for ramie was significantly lower than that determined for the cottons.

Apparatus for Use with the X-Ray Diffractometer to Determine the Degree of Crystallite Orientation in Fibers

Apparatus for Use with the X-Ray Diffractometer to Determine the Degree of Crystallite Orientation in Fibers

Determination of degree of crystallite orientation in graphite products

Determination of degree of crystallite orientation in graphite products

Moduli of Cotton Fibers and Yarns in Relation to X-Ray Angles

Cotton samples with a wide range in fiber properties were chosen. An X-ray measure of the degree of crystallite orientation and/or the secant modulus of fifteen cottons are traced through levels from sub-fibers to single fibers to bundles to yarns. The differences due to sample characteristics gradually become less as the cottons progress through these levels. When the secant modulus of the yarns spun at the appropriate twist for maximum strength is referred to the X-ray measurement, no additional masking, but resolution occurs. The resolution seems to be more pronounced with American upland than with barbadense cottons. Tenacity, secant modulus, and bundle linear density primarily explain the rankings.

Determination of the Degree of Crystallite Orientation in Cotton Fibers by Means of the Recording X-Ray Diffraction Spectrometer

An improved technique is described for the quantitative determination of the degree of crystallite orientation of cellulose in cotton and related cellulosic fibers, using the X-ray diffraction spectrometer with potentiometer recording and a rotating specimen mount. The method is based on the angular dispersion of the 002 diffraction arc of cellulose but employs the somewhat more conveniently determined angle at half-maximum in tensity instead of the photographically determined "40% angle," used by Berkley. It is shown that the angle of half-maximum intensity (50% angle by analogy) is less than Berkley's "40% angle" by a constant value of 3.3°. The effects upon the precision of the results of sample preparation and instrumental variations are described. Under the conditions proposed, the precision of the half- maximum angle is about 0.65°. This compares with a precision of about 1.0° for results obtained by photographic recording and photometering of the X-ray patterns [2]. Using the improved X-ray spectrometer technique described, the dark room required for photographic determination of orientation, with its rigid processing control, can be dispensed with, and a determination can be made in about one-fourth of the time.

14—On the Technique of Measuring Orientation in Cotton by X-Rays

AbstractThe degree of crystallite orientation has been measured for 14 cottons by X-rays and has been expressed in three ways. First, by the angular displacement from the point of maximum blackening on the (002) diffraction arc to the point where the absorption is 40 per cent, of the maximum; this was first used by berkley and Woodyard and is standard practice in America. Corrections have to be applied for those experimental conditions which cannot be held constant.A second method, developed by the author, employs a calibration strip on each film, which allows transmitted intensity readings to be converted directly into the corresponding X-ray intensities, independent of the opacity of the film or of the particular characteristics of the microphotometer used.The third method gives the average angle of inclination to the fibre axis of the chain molecules in the crystalline regions; it has been used by Hermans et al mainly for viscose rayon, and takes into account the distribution of X-ray intensity around ...

X-ray Studies of Silk Fibres

X-ray studies were made of a Bombyx mori type of silk and of a Tussah silk. Differences in the diffractive properties of the fibroin components of these silks are recorded. Diffraction bands were found for the sericin components of each type of silk, show ing that this component also exists on the fibre in a partially crystalline condition but with a lower degree of crystallite orien tation than is exhibited by the fibroin component. The positions of the observed sericin bands are different for each type of silk. Comparison of the diffraction patterns of hard and soft silks of the Bombyx mori type showed no significant difference between them.