Degree Of Crystalline Orientation Research Articles

Production of Crystal Oriented Neodymium Silicate Oxyapatite Ceramics and Their Conductivity

Production of oxide ion conductor ceramics having high conductivity is important for applications of solid oxide fuel cells (SOFC) and chemical sensors. Particularly, the ceramics with high ionic conductivity around 873 K have attracted attention for development of SOFC and sensors operated at middle-temperature.Neodymium silicate oxyapatite, denoted by NSO hereafter, was known to show very high oxide ion conductivity along to the c-axis below 873 K [1]. To utilize this property, production of the crystal-oriented ceramics is necessary. In this research, we produced crystal-oriented NSO green bodies by a slip casting under a magnetic field less than 1 T. Dense and crystal-oriented NSO ceramics were obtained by subsequent conventional sintering under an ambient atmosphere. In addition, NSO ceramics having different degree of crystalline orientation were successfully produced. Using these ceramics, the degree of the crystal orientation and its dependence on conductivity were discussed on the basis of experimental data.Composition of NSO was Nd9.43(SiO4)6O2, which was confirmed to be close to the oxyapatite single phase (NSO has a wide composition range [2], [3]). The raw materials were Nd2O3 and SiO2. NSO was synthesized by solid state reaction method at 1473 K or 1773 K.For production of crystal-oriented NSO green body, controlling the distribution of particle size was important to prepare a slurry used for slip casting. Therefore, the synthesized NSO powder was grinded by planetary ball mill. The slurry was prepared by mixing of the grinded NSO powder and polyethyleneimine in distilled water. The c-axis oriented NSO green body was prepared by slip casting under a magnetic field of 1 T and 0.5 T. These green bodies were denoted by NSO-1T and NSO-0.5T, hereafter. The green body produced without magnetic field was denoted as NSO-0T. The green bodies were sintered at 1873 K for 6 h in air in order to obtain the dense ceramics.X-ray diffraction (XRD) patterns on surfaces of (a) NSO-0T, (b) NSO-0.5T and (c) NSO-1T are shown in the Figure. XRD profile of (a) NSO-0T is good agreement with that of the oxyapatite single phase (standard data (d), ICSD No. 01-075-7767). Regarding to the patterns of (b) NSO-0.5T and (c) NSO-1T, intensities of (00l) peaks were very high, compared to those of (a) NSO-0T and standard data. The degree of crystal orientation was evaluated by Lotgering factor [4] calculated from these XRD patterns. Lotgering factors of the densified NSO-1T and NSO-0.5T were 0.93 and 0.95, respectively. In the case of perfect crystal-orientation, Lotgering factor is unity. Contrary, the factor is zero for random crystalline orientation. The factor values of 0.93 and 0.95 indicate that the degrees of the c-axis orientation are very high.Conductivity was measured by electrochemical impedance method between 773 K and 1273 K under air. The conductivity was found to be depended on the Lotgering factor values. Conductivities at 773 K of the samples sintered from NSO-1T, NSO-0.5T, and NSO-0T were 3.97×10-3, 3.04×10-3, and 3.88×10-4 S cm-1, respectively. The conductivities of the samples with highly c-axis orientation was about 10 times higher compared to that of randomly oriented samples. The conductivities of sintered NSO-0.5T and NSO-1T along to the c-axis at 773 K are confirmed to be close to that of a single crystal (6.4×10-3 S cm-1) [5].Considering into high magnetic susceptibility of neodymium, the crystal-oriented NSO ceramics can be fabricated under magnetic fields less than 1 T and high conductivity was achieved comparable to that of single crystal.Reference[1] S. Nakayama, et al, Journal of the European Ceramic Society, 19, 507-510, (1999).[2] R. O. Miller, et al, J. Am. Ceram. Soc., 47, 653-654, (1964).[3] G. J. McCathy, et al, J. Inorg. Nucl. Chem., 29, 253-254, (1967).[4] F. K. Lotgering, J Inorg. Nucl. Chem., 9, 113-123 (1959).[5] S. Nakayama, et al, Journal of materials science letters, 20, 913-915, (2001). Figure 1

Tailoring magnetic properties of self-biased hexaferrites using an alternative copolymer of isobutylene and maleic anhydride

Discussed is a novel self-biased hexaferrite gelling system based on a nontoxic and water-soluble copolymer of isobutylene and maleic anhydride. This copolymer simultaneously acts as a dispersant and gelling agent, and recently received much attention from the ceramics community. Herein its effects on the rheological conditions throughout magnetic-field pressing, and consequently, orientation, density and magnetic properties of textured hexaferrites were investigated. Ka-band FMR linewidths were measured, and the crystalline anisotropy and porosity induced linewidth broadening were estimated according to Schlömann’s theory. The copolymer allowed to reduce the friction between micron-sized magnetic particulates, resulting in higher density and degree of crystalline orientation, and lower FMR linewidth.

Microstructure dependent filament forming kinetics in HfO2 programmable metallization cells

Variability remains the principal concern for commercialization of HfO2 based resistance switching devices. Here, we investigate the role of thermal processing conditions on internal structure of atomic layer deposited HfO2 thin films, and the impact of that structure on filament forming kinetics of p+ Si/HfO2/Cu and TiN/HfO2/Cu devices. Regardless of bias polarity or electrode metal, filament formation times are at least one order of magnitude shorter in polycrystalline than in amorphous films, which we attribute to the presence of fast ion migration along grain boundaries. Within polycrystalline films, filament formation times are correlated with degree of crystalline orientation. Inter-device variability in forming time is roughly equivalent across HfO2 film processing conditions. The kinetics of filament forming are shown to be highly dependent on HfO2 microstructure, with possible implications for the inter-device variability of subsequent switching cycles.

Fabrication of Dense Ceramics and the Electrical Conductivity Anisotropy of the Textured MgO-Doped Lanthanum Silicate Oxyapatite

【Introduction】 Lanthanum silicate oxyapatite (LSO) has attracted attention as a new solid electrolyte for solid oxide fuel cell due to its high oxygen-ion conductivity and chemical stability[1]. Magnesium oxide has been reported as the effective dopant to improve the oxygen-ion conductivity of the LSO [2]. It has been revealed that non-doped LSO shows the anisotropic oxygen-ion conductivity depending on the crystal structure direction. It is already known that the oxygen-ion conductivity parallel to the c-axis of the non-doped LSO is much higher than that perpendicular to the c-axis. On the other hand, the anisotropic oxygen-ion conductivity of MgO-doped LSO has not been reported yet. In this study, influence of the crystal orientation on the total conductivity of the MgO-doped LSO was investigated by using texture ceramics which were fabricated by colloidal processing under a strong magnetic field. 【Experimental】 Lanthanum hydroxides La(OH)3, amorphous silica SiO2, Magnesium oxide MgO were used as the raw materials. The raw powders, YSZ balls with a diameter of 5mm, and ethanol were mixed by a pod mill, and the resulting slurry was sieved and dried at 373K. The dried powder was pulverized and the resulting powder was pressed at 20MPa into pellets. The pellets were calcinated at 1673K for 10h in air. The calcinated pellets were pulverized into powder. The resulting powder was dispersed into a water dissolving of ammonium polycarboxylic acid. After the YSZ balls with a diameter of 1mm was added into the mixture, the dispersed MgO-doped LSO powder was ground into small particle using planetary ball mill. This slurry was consolidated by slip casting in a strong magnetic field (12T). A magnetic field was applied parallel or perpendicular to the casting direction. In the case of the latter, the green compacts were prepared in two ways that slurry was rotated or not. The green compacts were pressed by cold isostatic pressing (CIP) at 392MPa, and were then calcinated at 1073K for 5h to remove dispersant. Texture ceramics were obtained by sintering at 1873K for 10h in air. The degree of crystalline orientation was determined by X-ray diffraction (XRD) analysis. The total conductivity of the samples were measured using the two-probe impedance method. 【Results and discussion】 The relative intensities of the (h00) peaks in the surface perpendicular to the static magnetic field were higher than those of the non-oriented one. In contrast, on the surface parallel to the rotating plane of strong magnetic field, the intensities of the (00l) peaks are relatively strong compared to the other peaks. These XRD data show that the crystalline orientation of MgO-doped LSO was controlled by slip casting in a strong magnetic field, and c-axis was aligned by the rotating magnetic field. It is different from non-doped LSO whose the c-axis was aligned parallel to the magnetic field. By comparing to the total conductivity of the above ceramics, the order of the magnitude was found to be the c-axis oriented ceramics > non-textured > a,b-axes oriented one. 【References】 [1] S. Nakayama et al., J. Eur. Ceram. Soc., 18, 1413-1418 (1998) [2] H. Yoshioka et al., Solid State Ionics, 179, 2165-2169 (2008) Figure 1

The degree of crystalline orientation as a function of draw ratio in semicrystalline polymers: a new model based on the geometry of the crystalline chain slip mechanism

The orientation behaviour of a range of high-density polyethylenes drawn to different draw ratios has been investigated by measurements of optical birefringence and wide-angle X-ray diffraction (WAXS). Consistent with previous research, it can be concluded that birefringence relates to the overall degree of orientation of the amorphous and crystalline phases, and is described to a good approximation by the pseudo-affine deformation scheme. The WAXS results show that crystalline orientation is also related uniquely to the applied strain and moreover is independent of the characteristics of the polymer concerned. It is shown that the crystalline orientation follows a new model based on the geometry of the crystalline slip mechanism where the crystalline phase deforms affinely in the longitudinal drawing direction.

A method for predicting thickness of the unoriented layer in ZnO film using piezoelectricity distribution in depth direction

The crystalline orientation of thin films gradually improves as the growth proceeds. Especially in the non-epitaxial growth, its initial layer is often unoriented. Because the unoriented layer degrades the performance of the device, the degree of crystalline orientation in depth direction is a very important issue. We propose a non-destructive method for predicting the thickness of the unoriented layer, making use of piezoelectricity distribution of films. An electromechanical resonator consisting of the single highly oriented layer excites a fundamental mode, but does not excite a second-overtone mode. The unoriented layer, on the other hand, exhibits little piezoelectric effect. A bilayer resonator consisting of the highly oriented layer on the unoriented layer excites a second-overtone mode because of the deference of piezoelectricity in these layers. In this study, the electromechanical resonance characteristics of Cu/ZnO(0 0 0 1)/Ti(0 0 0 1)/SiO2, Cu/ZnO(0 0 0 1)/AZO(0 0 0 1)/Ti(0 0 0 1)/SiO2 and Cu/ZnO/Al/SiO2 were experimentally observed. These results were compared with the theoretical estimations by a mechanical transmission line model to determine the thicknesses of the piezoelectrically inactive layers in the (0 0 0 1) or oriented ZnO films. The inactive layer thickness in the oriented ZnO film was in good agreement with the unoriented layer thickness observed by the cross-sectional transmission electron microscopy and electron diffraction.

(111)-Oriented Pb(Zr0.52Ti0.48)O3 thin film on Pt(111)/Si substrate using CoFe2O4 nano-seed layer by pulsed laser deposition

Perovskite Pb(Zr0.52Ti0.48)O3 (PZT) thin film with perfect (111)-orientation was achieved on CoFe2O4 seeded-Pt(111)/Ti/SiO2/Si substrate by pulsed laser deposition technique using target with limited excess Pb. Pyrochlore phase formation was suppressed on Pt by CoFe2O4 nano-seed layer (~7 nm), and perovskite PZT was achieved at temperature as low as 550 °C. CoFe2O4 seed layer that has perfect (111)-orientation acts as a promoter for perfectly (111)-orientated growth of PZT. PZT film grown at 600 °C has higher degree of crystalline orientation, lower surface roughness, and compacted microstructure in comparison to the film grown at 550 °C. The PZT film has a nano-size grain-feature structure with grain size of about 40–60 nm. Perovskite formation was also confirmed by ferroelectric measurement. The ferroelectric properties of PZT film grown at 600 °C is higher than that grown at 550 °C which could be attributed to the enhancement of the crystalline orientation, crystallinity, and microstructure of the film.

The structure–property relationships of artificial silk fabricated by dry-spinning process

Regenerated silk fibroin (RSF) fibers were dry-spun from RSF aqueous solution and then post-treated in ethanol aqueous solution. In order to prepare artificial silk which are tougher and stronger than their natural counterpart, the structure–property relationships of the RSF fibers and natural silkworm silks were investigated by using synchrotron radiation X-ray microdiffraction technology, birefringence measurements and Raman spectroscopy. The as-spun RSF fibers with poor mechanical properties exhibited a strong diffraction peak of the [021] lattice plane and a weak diffraction peak of the [020]/[200] lattice plane. However, both the natural silk and the post-treated RSF fibers with exceptional mechanical properties showed weak diffraction peaks of the [021] lattice plane and strong diffraction peaks of the [020]/[200] lattice plane. Nevertheless, the two crystalline peaks are attributed to the silk II structure of silk fibroin. By deconvoluting the one-dimensional wide-angle X-ray microdiffraction pattern, the crystallinity and the degree of crystalline orientation were obtained. The as-spun fibers showed low crystallinity and low crystalline orientation, but the microstructure of the RSF fibers could be improved greatly and even become similar to that of degummed cocoon silk by post-treatment. When the as-spun RSF fibers were first drawn 3 to 4 times with a draw rate of 0.9 mm s−1 in ethanol aqueous solution and then immersed in the same solution for another hour, the breaking strain and breaking energy of the post-treated fibers were significantly greater than those of degummed cocoon silk.

Oriented crystallization of alkylating amino-nitropyridine in a matrix of polyvinyl alcohol

It was found that alkylating amino-nitropyridine was able to crystallize epitaxially in a matrix of polyvinyl alcohol (PVA). Its longest spacing lay upon the periodical spacing between highly oriented PVA chains, i.e. its alkyl chains were across PVA chains. The degree of crystalline orientation of alkylating amino-nitropyridine in a drawn matrix of PVA was markedly higher than that of PVA at the low draw ratio below 6, which suggested that its epitaxial growth progressed with selecting the micro-fibrils composed of the highly oriented PVA. One of possible models of this epitaxy structure has been deduced with using its crystal structure proposed in a previous paper, which well matches its X-ray diffraction patterns.

Surface Structures of Regenerated Cellulose Fibers Observed by Atomic Force Microscopy.

The surface morphology of various regenerated cellulose fibers was observed by atomic force microscopic method under dry and wet states. For Lyocel, long and slender microfibrils with ca. 10_??_20nm diameter were aligned along the fiber axis. Commercially available cupro (Cupro-1) had fibrils with ca. 80_??_200nm diameters. On the surface of anti-fibrillation type cupro (Cupro-2) and viscose rayon (Rayon), the well developed microfibrils were not clearly observed and anisotropy of the particles constructing the microfibril or aggregate was lower than those of Lyocel and Cupro-1. The tendency of fibrillation occurring under wet state was in the order of Lyocel>Cupro-1>Cupro-2_??_Rayon and this order was just corresponding to the degree of the anisotropy of the particles. The surface morphology was changed by wetting in the order of Rayon_??_Cupro-2>Cupro-1>Lyocel. The degree of connection of the particles along the fiber axis (DCP) was also in the latter order. The degree of crystalline orientation was just in reverse order. The decrease of the tensile strength by wetting was larger for the fiber with lower DCP. DCP and the anisotropy were considered to govern the lowering of the wet tensile strength and the fibrillation tendency for the regenerated cellulose fiber.

Magnetic torque of oriented bulk Bi2212 by the shock-loading method

The magnetic torque of oriented bulk specimen of Bi2Sr2CaCu2O8+δ by the shock-loading method was measured under magnetic fields up to 8 kOe in the temperature range from 4.2 to 100 K. The torque amplitude of the shocked specimen was much larger than that of the as-grown bulk specimen measured as a reference. The angular dependence of the torque was reproduced by assuming the Gauss-type distribution for the crystalline orientation. It became clear that the magnetic torque of the shocked specimen showed the high degree of crystalline orientation in which the c-axis is perpendicular to the pellet disk plane and that the flux pinning perpendicular to the pellet disk plane was enhanced by shock-loading.

Deformation behavior of polytetrafluoroethylene films under tensile stress at various temperatures

AbstractDeformation behavior of polytetrafluoroethylene (PTFE) films was investigated by thermomechanical analysis (TMA) under various tensile stresses (σ) up to 1.15 MPa in the temperature range from room temperature to 360°C. In the heating process above σ ≈ 0.25 MPa, a contraction of the PTFE film occurs in the melting temperature region. In the cooling process above σ ≈ 0.05 MPa, an elongation occurs in the crystallization temperature region, and above σ ≈ 0.5 MPa, it reaches 20–30% of the original length of the film. The PTFE films in the melt state above σ ≈ 0.5 MPa contract with increasing temperature up to 360°C and elongate with decreasing temperature. For the films that underwent deformation in the TMA, the crystalline orientation and the surface morphology were investigated by wide‐angle X‐ray diffraction and scanning electron microscopy, respectively. The degree of crystalline orientation in the deformed films increases with increasing σ and approaches a plateau at σ ≈ 0.4 MPa. On the surface of the deformed films, alignment of the bands and deformation of granules, which are formed by heat treatment above the melting point, are observed. © 1994 John Wiley & Sons, Inc.

Microwave properties of highly oriented YBa2Cu3O7-? superconducting thin films

We have performed millimeter-wave frequency (94 GHz) measurements on high-quality YBa2Cu3O7-δ superconducting films on yttrium-stabilized (100) ZrO2 and MgO substrates. The ∼0.2μm thin films fabricated by magnetron sputteringin situ with the YBa2Cu3O7-δ powders as target exhibit superconducting transition temperatures up to 88 K. The critical current density of 6×105 A/cm2 at 77 K and the X-ray diffraction spectrum as well as scanning electron microscope photographs indicate these thin films are fullyc-axis oriented, extremely high in density, and universally homogeneous. Millimeter-wave surface resistances have been measured on a hemisphere open resonator in the temperature range of 20 K toT c and beyond. The surface resistance at 94 GHz and 77 K for these films is found to be about 30 mΩ, nearly 1/4 that for copper, and a drop of two orders in the surface resistance within 4 K is observed, which indicates that these films are good materials for applications in the millimeter-wave range, especially for fabricating microwave devices. We observed such low surface resistance in these thin films due to the near absence of grain and phase boundaries coupled with a high degree of crystalline orientation.

Structures and properties of injection moldings of crystallization nucleator‐added polypropylenes. I. Structure–property relationships

AbstractFlexural test specimens were injection‐molded from polypropylenes added with 0.5 wt % of calcium carbonate, talc, p‐tert‐ dibutyl‐benzoic acid monohydroxy aluminum, or p‐di‐methyl‐benzylidene sorbitol under cylinder temperatures of 200–;320°C. Properties such as flexural modulus, flexural strength, heat distortion temperature, Izod impact strength, hardness, and mold shrinkage and higher‐order structures such as crystalline texture, crystallinity, a*‐axis‐oriented component fraction, and degree of crystalline orientation were measured and structure–property relationships were studied. By the addition of crystallization nucleators, the flexural modulus, flexural strength, heat distortion temperature, hardness, and mold shrinkage were increased and Izod impact strength was decreased. The degrees of crystalline orientation such as the orientation fraction OF and c‐axis orientation function fc were increased by the addition of nucleators. The degree of the increase was higher as the crystallization temperature was higher. Close relationships were observed between some properties and the degrees of crystalline orientation.

Surface morphology and crystalline orientation of uniaxially drawn polytetrafluoroethylene films

AbstractFor polytetrafluoroethylene (PTFE) films drawn uniaxially at 100, 150, 250, and 350°C, the morphology and degree of crystalline orientation were investigated by electron scanning microscopy and wide‐angle X‐ray diffraction, respectively. On the surface of the PTFE films which were heat‐treated at 350°C for 2 h before the drawing, granules with a diameter of about 2 μm and bands with a width of about 0.3 μm were observed. By the drawing below the melting point, the bands are transformed into fibrils and a porous structure is formed by the drawing above the draw ratio (λ) of about 1.3. By drawing above the melting point, striations appear perpendicularly to the draw direction, and the collapse of the granules is observed. The orientation of the crystallites increases rapidly with increasing the draw ratio and approaches a plateau at λ ≈ 1.5 for the films drawn above the melting point and at λ ≈ 2.0 for that below it.

Investigation of molecular orientation and conformational change upon drawing for various ethylene/1‐butene copolymers by IR spectroscopy

AbstractInfrared spectroscopy was used to investigate the molecular orientation and the conformational change upon drawing for various ethylene/1‐butene copolymers in a wide range of crystallinity (0 ≤ Xc ≤ 85% ). The degree of crystalline orientation at constant draw ratio decreases with increasing crystallinity. The orientation function for the amorphous CH2 sequence in the trans conformation, f(am), was calculated assuming additivity for the orientation functions of the trans bands. f(am) increases with drawing in a characteristical way for the different materials and reaches a value higher than that of the amorphous gauche bands. Furthermore, it was found that f(am) is strongly dependent on crystallinity. The relative concentration of the amorphous CH2 sequences in the trans conformation increases at the expense of that of the gauche sequences. The transformation from gauche to trans in the amorphous phase occurs simultaneously with the orientation of the amorphous CH2 sequences.

An examination of the crystal structures present in nylon‐6 fibers

AbstractThe variety of wide‐angle x‐ray scattering (WAXS) patterns exhibited by nylon‐6 fibers with different fabrication histories is rationalized using a model comprising three limiting structures, viz., an α, a γ, and a pleated α structure. The γ and pleated α structures both have a single broad reflection in the range 2θ = 19° −25°, but differ in their annealing behavior. At 205° (in vacuo), the pleated α structure converts to the normal α structure by removal of the pleats, without breaking any hydrogen bonds. The γ structure, however, remains unchanged under this annealing condition since it is necessary to break all the hydrogen bonding in the structure to convert it to the α form. Different fabrication routes produce fibers which resemble the three ideal structures to varying extents. Fibers extruded at low speeds (and hence low spinline tension) resemble a mixed conventional α/pleated α structure with only a small γ component. Increasing the take‐up speed (and hence the spinline tension) of the as‐spun fiber, or in‐line drawing of the low orientation fiber (without prior storage), increases the γ content. If drawing of the low orientation fiber takes place after several hours storage (off‐line drawing), a largely α structure is produced. The intensity of the 020 reflection in the γ structure is shown to be very dependent on the degree of crystalline orientation in the sample.

Properties of poly(ethylene terephthalate) prepared by high-pressure extrusion in a capillary die

The procedure of Southern and Porter has been used to prepare poly(ethylene terephthalate) segments by high-pressure extrusion in an Instron capillary rheometer at temperatures from 245° to 265°C. X-Ray measurements of crystalline orientation along the axis of long-growth segments showed that segment properties were controlled by the time-dependent crystallization of polymer melt in the rheometer reservoir. During the initial stage of extrusion, a highly oriented, translucent segment was generated by flow-induced crystallization. However, formation of the translucent morphology eventually stopped, and thereafter a poorly oriented, opaque segment was generated by solid-state extrusion. From wide- and small-angle x-ray scattering, differential scanning calorimetry, and density measurements, it was determined that the most perfect morphologies were prepared at an extrusion temperature of 265°C. In addition to having the highest degree of crystalline orientation, translucent segments extruded at 265°C have a peak melting point of 267°C and a crystallinity value of 62%. Hot-stage optical microscopy showed that the translucent segments contained axially aligned fibrous crystals whose birefringence persisted to 290°C. The exceptional thermal stability of the segments was corroborated by the results of shrinkage tests at temperatures near the melting point; even after 1 hr at 260°C, the shrinkage did not exceed 7%. The accumulated evidence suggests that the translucent segments contain an extended-chain component.

Melt Spinning of Poly-xylyleneadipamide

Drawn poly-m-xylyleneadipamide filament was dry-heat-treated under free tension at the temperature ranging from 50 to 230°C, and thermal shrinkage (S), birefrigence (Δn), degree of crystallinity (x), degree of crystalline orientation (fc) and degree of amorphous orientation (fa) of the specimens were measured . Relation between transition points observed by Arrhenius plot of 'thermal shrinkage vs. temperature of the thermal treatment and structural quantities, namely thermal retraction mechanism was investigated.The results are as follows : 1) Transition points are observed at 75, 110 and 190°Cin Arrhenius plot, that is, the plot of the logarithm of the thermal shrinkage (log S) vs. reciprocal of the absolute temperature (1/T). In the plots of Δn, x, fc and fa vs. 1/T, transition points are also observed at 50, 70, 110 and 180°C. There is a good relationship between thermal shrinkage and structural quantities.2) The transition point at 50°C is assumed to prior glass transition temperature in the slightly wet state and the thermal retraction caused at the temperature ranging from 50 to 75°Cis due to the disorientation of amorphous chains in the same state.3) The transition point at 75°Cis glass transition temperature, and the retraction caused at the temperature between 75 and 110°C is deduced from the disorientation of amorphous chains and the retraction of amorphous chains under tension induced by folded chain crystallization.4) The transition point at 110°Ccorresponds to the crystal grain boundary relaxation, designated as ai, and the thermal retraction caused at the temperature ranging from 110 to 190°Cis assumed to be mainly the retraction of amorphous chains under tension induced by folding.5) The transition at 190°C is assigned to the crystal disordering relaxation, designated as ct2, and the retraction in the range of 190 to 235°C is due to the rearrangement of molecular chains and partial melt. Melting point of this polymer is 235°C.

Steam and heat setting of nylon 6 fiber. V. Investigation of wide- and small-angle x-ray diffraction

Crystalline content, crystalline orientation, and long period of heat-set nylon 6 fibers were investigated. Fibers subjected to dry heat setting or steam setting, have x-ray diffraction patterns which suggest that an increase of crystallinity occurs on treatment, especially in the case of steam setting. The degree of crystalline orientation does not decrease greatly in either dry heat setting or steam setting. Therefore, the increased dyeability of nylon 6 fiber on heat setting is not attributable to a decrease of orientation of crystallites. The large increase of long period produced by steam setting corresponds to the increase in density noted.