Journal articles: 'Semi-Crystalline structure'

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Hajová, Hana, Richard Pokorný, and Juraj Kosek. "Diffusion Transport in Reconstructed Semi-Crystalline Structure of Polyolefins." Macromolecular Symposia 302, no. 1 (March 31, 2011): 121–28. http://dx.doi.org/10.1002/masy.201000073.

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Moskalewicz, Tomasz, Sławomir Zimowski, Aleksandra Fiołek, Alicja Łukaszczyk, Beata Dubiel, and Łukasz Cieniek. "The Effect of the Polymer Structure in Composite Alumina/Polyetheretherketone Coatings on Corrosion Resistance, Micro-mechanical and Tribological Properties of the Ti-6Al-4V Alloy." Journal of Materials Engineering and Performance 29, no. 3 (September 26, 2019): 1426–38. http://dx.doi.org/10.1007/s11665-019-04354-y.

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Abstract This paper describes ways of improving the tribological properties of the Ti-6Al-4V titanium alloy at room and elevated temperatures by electrophoretic deposition of Al2O3/PEEK708 composite coatings and post-heat treatment. The microstructure of the coating components and the coatings was examined by scanning and transmission electron microscopy as well as x-ray diffractometry. The influence of cooling rate after heating of the coated alloy on the PEEK structure and coating surface topography was investigated. It was found that slow cooling with a furnace produced a semi-crystalline structure, whereas fast cooling in water generated an amorphous polymer structure. The semi-crystalline coatings exhibited a more developed surface topography than the amorphous ones. The coatings with a semi-crystalline structure revealed higher scratch resistance than the amorphous ones. The corrosion resistance of the uncoated and coated specimens was examined using electrochemical techniques in a 3.5 wt.% NaCl aqueous solution. Both coatings increased the corrosion resistance of the alloy. The friction and wear properties of the coated specimens against an alumina ball in dry sliding contact at room temperature and elevated temperatures of 150 and 260 °C at ball-on-disk were examined. Both amorphous and semi-crystalline coatings increased the wear resistance and decreased the friction coefficient of the titanium alloy at room temperature. In addition, the semi-crystalline coating was also very effective in improving the titanium alloy’s tribological properties at elevated temperatures. The obtained results clearly show that the composite alumina/PEEK coatings are promising for tribological applications in mechanical engineering.

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Kalwik, Aleksandra, Przemyslaw Postawa, and Marcin Nabialek. "Analysis of Ageing Processes of Semi-Crystalline Materials." Materiale Plastice 57, no. 3 (September 30, 2020): 41–51. http://dx.doi.org/10.37358/mp.20.3.5378.

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The article presents the influence of accelerated UV ageing on the structural properties of selected polymer materials. In this study, 3 types of materials from a group of thermoplastics known as PP30T, PE, POM were used. The test samples were prepared by injection moulding. In turn, an accelerated UV ageing process (600 h) was carried out in the UV Test chamber with fluorescent lamps characterized by a wavelength of 313 nm. Changes in the structure of the tested materials were observed by using an optical microscope. Measurements of gloss on the surface of primary samples that were exposed to UV rays were also taken. In addition, the structure of primary and aged samples was tested by differential scanning calorimetry (DSC). The conducted studies have demonstrated the impact of UV radiation on the changes in the surface layer of tested materials.

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Simões, Ricardo, Júlio C. Viana, Gustavo R. Dias, and António M. Cunha. "Mechanical Behavior of the Lamellar Structure in Semi-Crystalline Polymers." Materials Science Forum 730-732 (November 2012): 1006–11. http://dx.doi.org/10.4028/www.scientific.net/msf.730-732.1006.

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We have employed molecular dynamics simulations to study the behavior of virtual polymeric materials under an applied uniaxial tensile load. Through computer simulations, one can obtain experimentally inaccessible information about phenomena taking place at the molecular and microscopic levels. Not only can the global material response be monitored and characterized along time, but the response of macromolecular chains can be followed independently if desired. The computer-generated materials were created by emulating the step-wise polymerization, resulting in self-avoiding chains in 3D with controlled degree of orientation along a certain axis. These materials represent a simplified model of the lamellar structure of semi-crystalline polymers, being comprised of an amorphous region surrounded by two crystalline lamellar regions. For the simulations, a series of materials were created, varying i) the lamella thickness, ii) the amorphous region thickness, iii) the preferential chain orientation, and iv) the degree of packing of the amorphous region. Simulation results indicate that the lamella thickness has the strongest influence on the mechanical properties of the lamella-amorphous structure, which is in agreement with experimental data. The other morphological parameters also affect the mechanical response, but to a smaller degree. This research follows previous simulation work on the crack formation and propagation phenomena, deformation mechanisms at the nanoscale, and the influence of the loading conditions on the material response. Computer simulations can improve the fundamental understanding about the phenomena responsible for the behavior of polymeric materials, and will eventually lead to the design of knowledge-based materials with improved properties.

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Kim, Man-Ho, Jeong-Mann Doh, Seong Chul Han, Keun Hwa Chae, Byung-Yong Yu, Kyung Tae Hong, Andrew Jackson, and Lawrence M. Anovitz. "The pore wall structure of porous semi-crystalline anatase TiO2." Journal of Applied Crystallography 44, no. 6 (October 4, 2011): 1238–45. http://dx.doi.org/10.1107/s0021889811037447.

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The structure of porous TiO2prepared by electrochemical anodization in a fluoride-containing ethylene glycol electrolyte solution was quantitatively studied using small-angle neutron scattering (SANS) and ultra-small-angle neutron scattering (USANS). The cylindrical pores along the coaxial direction were somewhat irregular in shape, were widely distributed in diameter, and seemed to have a broadly pseudo-hexagonal arrangement. The scattering from the pore wall showed a negative deviation from Porod scattering, indicating that the interface between TiO2and the pore was not sharp. A density gradient of around 40–60 Å at the pore wall (i.e.the interface between the pore and the TiO2matrix) was estimated using both constant and semi-sigmoidal interface models. This gradient may be due to the presence of fluorine and carbon partially absorbed by the pore wall from the fluoride-containing electrolyte or to sorbed water molecules on the wall. The neutron contrast-matching point between the TiO2matrix and the pores filled with liquid H2O/D2O mixtures was 51/49%(v/v) H2O/D2O, yielding an estimated mass density of 3.32 g cm−3. The specific surface area of the sample derived from the (U)SANS data was around 939–1003 m2 cm−3(283–302 m2 g−1).

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Prevorsek, D. C. "Structure of semi crystalline fibers from interpretation of anelastic effects." Journal of Polymer Science Part C: Polymer Symposia 32, no. 1 (March 8, 2007): 343–75. http://dx.doi.org/10.1002/polc.5070320119.

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Filsinger, D. H., and L. K. Frevel. "Computer Automation of Structure-Sensitive Search-Match Algorithm for Powder Diffraction Analysis." Powder Diffraction 1, no. 1 (March 1986): 22–25. http://dx.doi.org/10.1017/s0885715600011246.

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AbstractThe Semi-manual Structure-sensitive SEARCH-MATCH procedure [Frevel, (1982), Anal. Chem. 54, 691–697] has been automated for the Hewlett-Packard HP 3354 Computer. The software is coded in the interpretive HP LAB BASIC II language. A core file of 1026 selected powder diffraction standards has been compiled covering the common crystalline phases encountered in industry, the ubiquitous crystalline minerals, and prototypes of the more frequently found crystal structures. Solid solutions can be readily identified.

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Lovelace, J. J., K. Narayan, J. K. Chik, H. D. Bellamy, E. H. Snell, U. Lindberg, C. E. Schutt, and G. E. O. Borgstahl. "Imaging modulated reflections from a semi-crystalline state of profilin:actin crystals." Journal of Applied Crystallography 37, no. 2 (March 17, 2004): 327–30. http://dx.doi.org/10.1107/s0021889804001773.

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Modulated protein crystals remainterra incognitafor most crystallographers. While small-molecule crystallographers have successfully wrestled with and conquered this type of structure determination, to date no modulated macromolecular structures have been reported. Profilin:β-actin in a modulated semi-crystalline state presents a challenge of sufficient biological significance to motivate the development of methods for the accurate collection of data on the complex diffraction pattern and, ultimately, the solution of its structure. In the present work, fine φ-sliced data collection was used to resolve the closely spaced satellite reflections from these polymorphic crystals. Image-processing methods were used to visualize these data for comparison with the original precession data. These preliminary data demonstrate the feasibility of using fine φ-slicing to collect accurately the intensities and positions of the main and satellite reflections from these modulated protein crystals.

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Avramova, Nadka. "Amorphous and Semi-Crystalline Nylon-6: Processing and Properties." Engineering Plastics 1, no. 4 (January 1993): 147823919300100. http://dx.doi.org/10.1177/147823919300100403.

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The influence of processing conditions on the structure and properties of nylon-6 are investigated. Amorphous nylon-6 is obtained and its properties are compared with those of semi-crystalline nylon-6. The kinetics of crystallization of nylon-6 depends strongly on the previous thermal prehistory of the melt. The recently observed cumulative character in the structural memory of nylon-6 is successfully applied for obtaining this polymer in a pure amorphous state. It was demonstrated that a critical temperature exists above which the “memory” of this polymer can be erased, and this critical temperature is close to the equilibrium melting temperature T m°. The value of T m ° ≍280°C was evaluated using an independent technique. Melt annealing above this temperature suppresses the crystallization process due to destruction of all crystal nuclei. Amorphous nylon-6 was obtained by ultraquenching of its melt, previously treated at a temperature above T m °, to a temperature well below the glass transition region. The ultraquenched nylon-6 is characterized by amorphous initial structure and improved mechanical properties. The thermal behaviour, crystallization and mechanical properties are investigated by differential scanning calorimetry (DSC), wide angle X ray scattering (WAXS) and mechanical testing. After drawing and annealing, the tensile strength and elasticity modulus of initially amorphous nylon-6 increase three times and the elongation at break decreases by half as compared with conventionally quenched samples. The thermal treatment in vacuum of semi-crystalline nylon-6 affects both the structure and the molecular weight. It is demonstrated that the most important factor for the improvement of mechanical properties is the orientation in the amorphous regions. The lower die initial degree of crystallinity, the better are the orientation and the mechanical properties of nylon-6. The best mechanical properties of initially amorphous nylon-6 are explained by achievement of better orientation of molecules in the amorphous regions.

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Avramova, Nadka. "Amorphous and Semi-Crystalline Nylon-6: Processing and Properties." Polymers and Polymer Composites 1, no. 4 (January 1993): 261–74. http://dx.doi.org/10.1177/096739119300100403.

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The influence of processing conditions on the structure and properties of nylon-6 are investigated. Amorphous nylon-6 is obtained and its properties are compared with those of semi-crystalline nylon-6. The kinetics of crystallization of nylon-6 depends strongly on the previous thermal prehistory of the melt. The recently observed cumulative character in the structural memory of nylon-6 is successfully applied for obtaining this polymer in a pure amorphous state. It was demonstrated that a critical temperature exists above which the “memory” of this polymer can be erased, and this critical temperature is close to the equilibrium melting temperature T m°. The value of T m ° ≍280°C was evaluated using an independent technique. Melt annealing above this temperature suppresses the crystallization process due to destruction of all crystal nuclei. Amorphous nylon-6 was obtained by ultraquenching of its melt, previously treated at a temperature above T m °, to a temperature well below the glass transition region. The ultraquenched nylon-6 is characterized by amorphous initial structure and improved mechanical properties. The thermal behaviour, crystallization and mechanical properties are investigated by differential scanning calorimetry (DSC), wide angle X ray scattering (WAXS) and mechanical testing. After drawing and annealing, the tensile strength and elasticity modulus of initially amorphous nylon-6 increase three times and the elongation at break decreases by half as compared with conventionally quenched samples. The thermal treatment in vacuum of semi-crystalline nylon-6 affects both the structure and the molecular weight. It is demonstrated that the most important factor for the improvement of mechanical properties is the orientation in the amorphous regions. The lower die initial degree of crystallinity, the better are the orientation and the mechanical properties of nylon-6. The best mechanical properties of initially amorphous nylon-6 are explained by achievement of better orientation of molecules in the amorphous regions.

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Bellinger, Daniel, Jens Pflaum, Christoph Brüning, Volker Engel, and Bernd Engels. "The electronic character of PTCDA thin films in comparison to other perylene-based organic semi-conductors: ab initio-, TD-DFT and semi-empirical computations of the opto-electronic properties of large aggregates." Physical Chemistry Chemical Physics 19, no. 3 (2017): 2434–48. http://dx.doi.org/10.1039/c6cp07673d.

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Schuster, Miriam. "Determination of the linear viscoelastic material behaviour of interlayers with semi-crystalline structures shown by the example of a semi-crystalline ionomer." Glass Structures & Engineering 7, no. 2 (August 2022): 157–71. http://dx.doi.org/10.1007/s40940-022-00185-x.

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AbstractThe temperature dependent linear viscoelastic material behaviour of the most commonly used interlayer PVB is typically determined by means of Dynamic-Mechanical-Thermal-Analysis (DMTA). By horizontally shifting the isothermal modulus curves, a mastercurve is created at a certain reference temperature, which can then be mathematically approximated with a Prony series. A time–temperature superposition principle can be derived from the shift factors. In contrast to PVB, EVA and ionomer (or ionoplastic) interlayers have semi-crystalline structures that melt when the melting temperature is reached and form again when the sample is cooled below the crystallization temperature. The exact structure and number of crystallites depend e.g. on the cooling rate and the physical age (or thermal prehistory) of the sample. These factors must be taken into account in the experimental determination of the material parameters with DMTA. Using the example of SentryGlas®, this article shows that the stiffness of semi-crystalline interlayers is affected by the crystallinity. Mastercurves from DMTA with different temperature programs are created. The degrees of crystallization for the different temperature programs are determined with Differential Scanning Calorimetry (DSC). A time–temperature superposition principle, which applies to the purely amorphous material, and a time-crystallinity superposition principle are derived, which enable the determination of the material parameters for different temperatures and degrees of crystallization.

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Kuttich, Björn, Alexander Matt, Christian Appel, and Bernd Stühn. "X-ray scattering study on the crystalline and semi-crystalline structure of water/PEG mixtures in their eutectic phase diagram." Soft Matter 16, no. 45 (2020): 10260–67. http://dx.doi.org/10.1039/d0sm01601b.

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Water/PEG mixtures start to phase separate below the liquidus line. Above the eutectic temperature the solid phase is either pure water ice or semi-crystalline PEG. Below the eutectic line both crystals coexist, no mixed-crystalline phase is found.

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Li, Mengmeng, Pieter J. Leenaers, Martijn M. Wienk, and René A. J. Janssen. "The effect of alkyl side chain length on the formation of two semi-crystalline phases in low band gap conjugated polymers." Journal of Materials Chemistry C 8, no. 17 (2020): 5856–67. http://dx.doi.org/10.1039/d0tc00172d.

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15

Grubb, D. T. "Structure and properties of crystalline polymer fibers." Proceedings, annual meeting, Electron Microscopy Society of America 45 (August 1987): 444–47. http://dx.doi.org/10.1017/s0424820100126962.

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Most polymer fibers studied by TEM have been semi-crystalline or more recently liquid crystalline, both because the majority of technically interesting fibers are ordered and because scientific interest lies in the polymer morphology. The obvious common feature of fibers is that they are "fibrous" that is to say, they have long and narrow features aligned along the fiber direction. The basic unit obtained by a very local deformation of a crystal is called a micro-fibri l . [1,2] Fibrils may or may not be clear in the TEM, either because the structure itself is not well defined or because of superposition of several small fibrils within the sample.The large plastic deformation in fiber drawing will make any heterogeneity in the material appear fibrous. While zone drawing gels of poly(vinyl alcohol) recently we obtained porous fibers when residual ethylene glycol solvent boiled at just below the draw temperature.

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Soper, A. K., K. Page, and A. Llobet. "Empirical potential structure refinement of semi-crystalline polymer systems: polytetrafluoroethylene and polychlorotrifluoroethylene." Journal of Physics: Condensed Matter 25, no. 45 (October 18, 2013): 454219. http://dx.doi.org/10.1088/0953-8984/25/45/454219.

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Aoki, H., and M. Kodama. "The behavior of water molecules in semi-crystalline bilayer structure of phosphatidylethanolamine." Journal of thermal analysis 49, no. 2 (August 1997): 839–45. http://dx.doi.org/10.1007/bf01996768.

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Tencé-Girault, Sylvie, Sylvie Lebreton, Oana Bunau, Patrick Dang, and François Bargain. "Simultaneous SAXS-WAXS Experiments on Semi-Crystalline Polymers: Example of PA11 and Its Brill Transition." Crystals 9, no. 5 (May 24, 2019): 271. http://dx.doi.org/10.3390/cryst9050271.

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This manuscript of the special issue “Microstructural Evolution and Mechanical Behavior of Semi-Crystalline Polymers” aims to show that Small Angle X-ray Scattering (SAXS) and Wide Angle X-ray Scattering (WAXS) experiments performed simultaneously constitute a unique tool to obtain valuable information on the hierarchical structure of semi-crystalline polymers. These structural quantitative data are needed to model macroscopic properties of polymeric materials, for example their mechanical properties. To illustrate our point, we focus our study on the structure and morphology of polyamide 11. Through a simultaneous SAXS-WAXS experiment, we show that the absence of enthalpic signal in Differential Scanning Calorimetry (DSC) is not synonymous with the absence of structural and morphological evolution with temperature. The case of a thermally activated crystal–crystal transition, the Brill transition, is particularly detailed. Through this SAXS-WAXS study, we show, among other points, and for the first time, that the periodicity of crystalline lamellae (LP) changes at the transition, probably due to a modification of the amorphous phase’s free volume at the Brill transition. We also explain the crucial role of annealing to stabilize polymeric materials that may experience temperature changes over their lifetime. The influence of the annealing on the perfection of crystalline structure, morphology and mechanical behavior is more particularly studied.

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Zhang, Binjia, Ling Chen, Fengwei Xie, Xiaoxi Li, Rowan W. Truss, Peter J. Halley, Julia L. Shamshina, Robin D. Rogers, and Tony McNally. "Understanding the structural disorganization of starch in water–ionic liquid solutions." Physical Chemistry Chemical Physics 17, no. 21 (2015): 13860–71. http://dx.doi.org/10.1039/c5cp01176k.

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Flanagan, Bernadine M., Michael J. Gidley, and Frederick J. Warren. "Rapid quantification of starch molecular order through multivariate modelling of13C CP/MAS NMR spectra." Chemical Communications 51, no. 80 (2015): 14856–58. http://dx.doi.org/10.1039/c5cc06144j.

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Gaskell, P. H. "Relationships between the medium-range structure of glasses and crystals." Mineralogical Magazine 64, no. 3 (June 2000): 425–34. http://dx.doi.org/10.1180/002646100549481.

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AbstractThe known structure of a crystalline phase is almost always useful in investigating the unknown structure of the compositionally equivalent glass. For the local environment around elements like Si, B and P, the correspondence between site geometry and symmetry can be impressively close. Beyond near neighbours, any relationship becomes less obvious – at least in real-space data. Progress in understanding the medium-range structures of glasses has been painfully slow as a result. One essential clue is given by reciprocal-space features at low Q (scattering vector) in X-ray or neutron scattering data, which are clearly related to the medium-range structure. Interpretation of these features as ‘quasi-Bragg’ scattering allows direct comparison between the structures of the glass and equivalent crystalline phases. Applications of this method will be illustrated in borates and silicates, together with some chalcogenide glasses. Correspondence between low-Q features for these glasses and compositionally-equivalent crystals is qualitatively good. In some cases there is semi-quantitative agreement too. Thus the essential flavour of the medium-range structure of several typical glasses appears to be interpretable, rather easily.

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Ellison, Michael S., Paulo E. Lopes, and William T. Pennington. "In-Situ X-Ray Characterization of Fiber Structure during Melt Spinning." Journal of Engineered Fibers and Fabrics 3, no. 3 (September 2008): 155892500800300. http://dx.doi.org/10.1177/155892500800300302.

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The properties of a polymer are strongly influenced by its morphology. In the case of fibers from semi-crystalline polymers this consists of the degree of crystallinity, the spacing and alignment of the crystalline regions, and molecular orientation of the polymer chains in the amorphous regions. Information on crystallinity and orientation can be obtained from X-ray analysis. In-situ X-ray characterization of a polymer during the melt spinning process is a major source of information about the effects of material characteristics and processing conditions upon structure evolution along the spinline, and the final structure and properties of the end product. We have recently designed and installed an X-ray system capable of in-situ analysis during polymer melt spinning. To the best of our knowledge this system is unique in its capabilities for the simultaneous detection of wide angle and small angle X-ray scattering (WAXS and SAXS, respectively), its use of a conventional laboratory radiation source, its vertical mobility along the spinline, and its ability to simulate a semi-industrial environment. Setup, operation and demonstration of the capabilities of this system is presented herein as applied to the characterization of the melt spinning of isotactic poly(propylene). Crystallinity and crystalline orientation calculated from WAXS patterns, and lamellar long period calculated from SAXS patterns, were obtained during melt spinning of the polymer along the spinline.

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Kim, Hongdeok, and Joonmyung Choi. "Influence of crystalline structure on creep resistance capability in semi-crystalline Polymers: A coarse-grained molecular dynamics study." International Journal of Fatigue 188 (November 2024): 108517. http://dx.doi.org/10.1016/j.ijfatigue.2024.108517.

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Bertoft, Eric. "Understanding Starch Structure: Recent Progress." Agronomy 7, no. 3 (August 25, 2017): 56. http://dx.doi.org/10.3390/agronomy7030056.

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Starch is a major food supply for humanity. It is produced in seeds, rhizomes, roots and tubers in the form of semi-crystalline granules with unique properties for each plant. Though the size and morphology of the granules is specific for each plant species, their internal structures have remarkably similar architecture, consisting of growth rings, blocklets, and crystalline and amorphous lamellae. The basic components of starch granules are two polyglucans, namely amylose and amylopectin. The molecular structure of amylose is comparatively simple as it consists of glucose residues connected through α-(1,4)-linkages to long chains with a few α-(1,6)-branches. Amylopectin, which is the major component, has the same basic structure, but it has considerably shorter chains and a lot of α-(1,6)-branches. This results in a very complex, three-dimensional structure, the nature of which remains uncertain. Several models of the amylopectin structure have been suggested through the years, and in this review two models are described, namely the “cluster model” and the “building block backbone model”. The structure of the starch granules is discussed in light of both models.

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Sakai, Atsushi, Keiji Tanaka, Yoshihisa Fujii, Toshihiko Nagamura, and Tisato Kajiyama. "Structure and thermal molecular motion at surface of semi-crystalline isotactic polypropylene films." Polymer 46, no. 2 (January 2005): 429–37. http://dx.doi.org/10.1016/j.polymer.2004.11.021.

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YE, Xiufang, Jingxuan LIN, Dongchu CHEN, Menglei CHANG, and Hongyang WEI. "Design and Synthesis of Crystalline Carboxyl-terminated Polyester Resin." Materials Science 27, no. 2 (May 5, 2021): 217–23. http://dx.doi.org/10.5755/j02.ms.24058.

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In this work, a novel semi-crystalline polyester resin synthesis was explored, then influence of alcohol/acid ratio and monomer’s structure on crystallinity of poliester resin were studied in details. The crystalline polyester resin was synthesized via a two-step melt-condensation method. The structure and performance of the polyester resin was characterized by X-ray diffraction, infrared radiation, differential scanning calorimeter, thermogravimetric analysis and melt flow rate. The effect of molar ratio between alcohol monomer and carboxyl monomer on the structure and performance of polyester resin was studied, based on these, how the modifications (1,4-cyclohexanedicarboxylic acid and 1,4-cyclohexanedimethanol) affected the crystalline properties of the resin were further studied and optimized with the multi-factors orthogonal test method, and the results show that the synthesized polyester resin meets the expected design, and has some crystalline structure. The change of hydroxyl/carboxyl ratio (-OH/-COOH) can affect the crystallinity: the larger the crystallinity, the smaller the melt flow rate. Two modifications containing rigid cyclohexyl groups with high symmetry can improve the crystallinity of polyester resin.

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Goldman, Maxwell, and Yining Huang. "Investigation into the crystallization of molecular sieve DNL-6." Canadian Journal of Chemistry 100, no. 2 (February 2022): 123–31. http://dx.doi.org/10.1139/cjc-2021-0100.

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Crystallization of DNL-6, a silicoaluminophosphate (SAPO) based molecular sieve with the RHO topology, was investigated under both the hydrothermal synthesis (HTS) and dry-gel conversion (DGC) conditions. Crystallization of DNL-6 under the HTS conditions is rather fast. But a combination of crystallization under the DGC conditions and reducing reaction temperature slow down the reactions, allowing for intermediates to be captured. Under the DGC conditions, DNL-6 crystallizes through a semi-crystalline layered phase. The nature of this intermediate is aluminophosphate (AlPO) rather than SAPO with most P atoms having a local environment of P(–O–Al)3(OH). The surfactant (cetyltrimethylammonium chloride) used for synthesis appears to be part of the layered intermediate. Si is directly incorporated in the DNL-6 framework via SM II mechanism when the semi-crystalline AlPO phase is transforming to DNL-6 with the assistance of a very small amount of water. Both the structure directing agent and the surfactant play a role in the formation of DNL-6, as they were found within the final synthesized products. SEM data show that hydrothermal synthesis produces a much more crystalline product. The facts that the semi-crystalline layered phase was also observed in the powder X-ray diffraction patterns of the solid samples obtained under the HTS conditions and that the evolution of the local structure around P and Al in the intermediate phases are similar imply that under the reaction conditions employed in the present study, the formation pathways of DNL-6 under the HTS and DGC conditions appear to have some similarities.

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Fiołek, Zimowski, Kopia, and Moskalewicz. "The Influence of Electrophoretic Deposition Parameters and Heat Treatment on the Microstructure and Tribological Properties of Nanocomposite Si3N4/PEEK 708 Coatings on Titanium Alloy." Coatings 9, no. 9 (August 21, 2019): 530. http://dx.doi.org/10.3390/coatings9090530.

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Nanocomposite Si3N4/PEEK 708 coatings were successfully fabricated on the Ti-6Al-4V alloy substrate by electrophoretic deposition (EPD) and post-EPD heat treatment. The addition of chitosan polyelectrolyte into ethanolic-based suspensions enabled the cathodic co-deposition of ceramic and polymeric particles. Zeta potential measurements allowed the elaboration of stable suspensions. The selection of the optimal EPD voltage and time enabled uniform coatings to be obtained. Heating above the PEEK melting point and cooling with a furnace or in water resulted in the formation of dense coatings with semi-crystalline or amorphous polymer structures, respectively. Both coatings with a thickness in the range of 90–105 µm had good adhesion and scratch resistance to the substrates, despite the presence of relatively high degrees of open porosity. The coatings improved the tribological properties of the titanium alloy. However, a strong relationship between the polymeric matrix structure and wear resistance was observed. Semi-crystalline coatings proved to be significantly more wear resistant than amorphous ones.

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Tsuchikawa, Satoru, and H. W. Siesler. "Near-Infrared Spectroscopic Monitoring of the Diffusion Process of Deuterium-Labeled Molecules in Wood. Part I: Softwood." Applied Spectroscopy 57, no. 6 (June 2003): 667–74. http://dx.doi.org/10.1366/000370203322005364.

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The diffusion process of several molecules (D2O, n-butanol (OD) and t-butanol (OD)) in softwood (Sitka spruce) was investigated by means of a deuterium exchange method and Fourier transform near-infrared (FT-NIR) polarization spectroscopy. The location of OH groups in different states of order of cellulose in wood was clarified by analyzing the FT-NIR transmission spectra ranging from 7200 to 6000 cm−1. Four absorption bands were assigned to 2 × v(OH) absorptions of the amorphous regions, OH groups in semi-crystalline regions, and two types of intramolecular hydrogen-bonded OH groups in the crystalline regions, respectively. The saturation level of accessibility was very different for these absorption bands (i.e., 70–80, 60, and 40–50% for the amorphous, semi-crystalline, and crystalline regions, respectively). However, the saturation accessibilities for each absorption band varied little with molecular structure and geometry of the diffusants. The diffusion rate of D2O was much faster than that of n-butanol (OD) and t-butanol (OD) for all states of orders. The size effect of the butanols led to slight differences in the diffusive transport in the crystalline regions.

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Hoffmann, Falk, Rainhard Machatschek, and Andreas Lendlein. "Understanding the impact of crystal lamellae organization on small molecule diffusion using a Monte Carlo approach." MRS Advances 5, no. 52-53 (2020): 2737–49. http://dx.doi.org/10.1557/adv.2020.386.

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AbstractMany physicochemical processes depend on the diffusion of small molecules through solid materials. While crystallinity in polymers is advantageous with respect to structure performance, diffusion in such materials is difficult to predict. Here, we investigate the impact of crystal morphology and organization on the diffusion of small molecules using a lattice Monte Carlo approach. Interestingly, diffusion determined with this model does not depend on the internal morphology of the semi-crystalline regions. The obtained insight is highly valuable for developing predictive models for all processes in semi-crystalline polymers involving mass transport, like polymer degradation or drug release, and provide design criteria for the time-dependent functional behavior of multifunctional polymer systems.

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Syed Nuzul Fadzli, S. A., S. Roslinda, and Firuz Zainuddin. "Sol Gel Synthesis and In Vitro Evaluation of Apatite Forming Ability of Silica-Based Composite Glass in SBF." Key Engineering Materials 660 (August 2015): 125–31. http://dx.doi.org/10.4028/www.scientific.net/kem.660.125.

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In this study, xerogel glass based on SiO-CaO-PO4 was synthesized by a low temperature acid catalysed sol-gel route. The in vitro evaluation of apatite forming ability for the glass was conducted in simulated body fluid (SBF) solution as the glasses were immersed for duration of 1, 7, 24 hours and 7 days. The XRD analysis showed that the glass formed semi-crystalline structure when sintered at 1000oC and consisted of Ca2O7P2 and Ca2O4Si phases. Image captured using FESEM showed the apatite-like structures were eventually formed on the glass top surface in small numbers after the glass immersed in SBF for only an hour. The numbers of the apatite structures were continuously grown with the increase period of immersion time. The apatite structure mostly covered on top of the glass surface after 24 hours of immersion and continuously growth into bone-like apatite structure when immersed for 7 days in the SBF. The apatite layer formed on the surface of the glass was confirmed as crystalline structure of hydroxyl-carbonate-apatite (HCA) as revealed by the complimentary results of EDS, XRD and FTIR analysis.

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Maleki-Bigdeli, Mohammad-Ali, Majid Baniassadi, Kui Wang, and Mostafa Baghani. "Developing a beam formulation for semi-crystalline two-way shape memory polymers." Journal of Intelligent Material Systems and Structures 31, no. 12 (May 30, 2020): 1465–76. http://dx.doi.org/10.1177/1045389x20924837.

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In this research, the bending of a two-way shape memory polymer beam is examined implementing a one-dimensional phenomenological macroscopic constitutive model into Euler–Bernoulli and von-Karman beam theories. Since bending loading is a fundamental problem in engineering applications, a combination of bending problem and two-way shape memory effect capable of switching between two temporary shapes can be used in different applications, for example, thermally activated sensors and actuators. Shape memory polymers as a branch of soft materials can undergo large deformation. Hence, Euler–Bernoulli beam theory does not apply to the bending of a shape memory polymer beam where moderate rotations may occur. To overcome this limitation, von-Karman beam theory accounting for the mid-plane stretching as well as moderate rotations can be employed. To investigate the difference between the two beam theories, the deflection and rotating angles of a shape memory polymer cantilever beam are analyzed under small and moderate deflections and rotations. A semi-analytical approach is used to inspect Euler–Bernoulli beam theory, while finite-element method is employed to study von-Karman beam theory. In the following, a smart structure is analyzed using a prepared user-defined subroutine, VUMAT, in finite-element package, ABAQUS/EXPLICIT. Utilizing generated user-defined subroutine, smart structures composed of shape memory polymer material can be analyzed under complex loading circumstances through the two-way shape memory effect.

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Shieh, P. C., and J. M. Howe. "Investigation of the atomic structure of crystal/amorphous interfaces in Pd80Si20 Alloy by HRTEM and image simulations." Proceedings, annual meeting, Electron Microscopy Society of America 48, no. 4 (August 1990): 114–15. http://dx.doi.org/10.1017/s0424820100173704.

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Determining the atomic structures of solid/liquid interfaces is important for understanding mechanisms of solidification of crystalline materials. To date, research in this area has largely been theoretical in nature because of the difficulty of determining the atomic structure of a solid/liquid interface experimentally. This study has employed HRTEM and image simulations to investigate the atomic structure of crystalline/amorphous interfaces in directionally crystallized Pd80Si20 amorphous ribbons. The crystalline/amorphous interface is similar to a solid/liquid interface in many respects. The HRTEM analyses of directionally crystallized samples have shown that the amorphous Pd80Si20 alloy crystallizes into a lamellar mixture of faceted Pd3Si and nonfaceted Pd9Si2. Interpretation of the HRTEM images requires knowledge of the visibility of ordered structures imbedded in amorphous surroundings. This paper reports the results of a computer simulation study undertaken to determine this visibility.Computer simulations were performed in two parts: 1) construction of a model atomic structure, and 2) simulation of HRTEM images of the model structure. The atomic model was started with a crystalline seed of Pd3Si several unit-cells thick and new atoms were deposited on to the seed according to the dense random packing model for metal-metalloid systems. A unit cell of appropriate size was cut from the resulting composite structure and sliced into layers for input into the image simulations. The HRTEM images were calculated using the TEMPAS multislice program with the following parameters for a JEOL 4000EX: 400kV accelerating potential, 1.0 mm spherical aberration coefficient, 5.0 nm half-width of Gaussian spread of defocus, 0.5 mrad semi-angle of beam convergence, 6.5 nm−1 objective aperture radius, −50.0 nm defocus (near Scherzer defocus) and diffracted beams out to 4.0 nm−1

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Chen, Jun-Qi, Xuan Wang, Wei-Feng Sun, and Hong Zhao. "Improved Water-Tree Resistances of SEBS/PP Semi-Crystalline Composites under Crystallization Modifications." Molecules 25, no. 16 (August 12, 2020): 3669. http://dx.doi.org/10.3390/molecules25163669.

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Water-tree resistances of styrene block copolymer/polypropylene (SEBS/PP) composites are investigated by characterizing crystallization structures in correlation with the dynamic mechanical properties to elucidate the micro-structure mechanism of improving insulation performances, in which the accelerated aging experiments of water trees are performed with water-knife electrodes. The water-tree morphology in spherulites, melt-crystallization characteristics and lamella structures of the composite materials are observed and analyzed by polarizing microscopy (PLM), differential scanning calorimetry (DSC) and scanning electron microscopy (SEM), respectively. Dynamic relaxation and stress-strain characteristics are specifically studied by means of a dynamic thermomechanical analyzer (DMA) and electronic tension machine, respectively. No water-tree aging occurs in both the highly crystalline PP and the noncrystalline SEBS elastomer, while the water trees arising in SEBS/PP composites still has a significantly lower size than that in low-density polyethylene (LDPE). Compared with LDPE, the PP matrix of the SEBS/PP composite represent a higher crystallinity with a larger crystallization size in consistence with its higher mechanical strength and lower dynamic relaxation loss. SEBS molecules agglomerate as a “island” phase, and PP molecules crystallize into thin and short lamellae in composites, leading to the blurred spherulite boundary and the appreciable slips between lamellae under external force. The high crystallinity of the PP matrix and the strong resistance to slips between lamellae in the SEBS/PP composite essentially account for the remarkable inhibition on water-tree growth.

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Schlicht, Samuel, Sandra Greiner, and Dietmar Drummer. "Low Temperature Powder Bed Fusion of Polymers by Means of Fractal Quasi-Simultaneous Exposure Strategies." Polymers 14, no. 7 (March 31, 2022): 1428. http://dx.doi.org/10.3390/polym14071428.

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Powder Bed Fusion of Polymers (PBF-LB/P) is a layer-wise additive manufacturing process that predominantly relies on the quasi-isothermal processing of semi-crystalline polymers, inherently limiting the spectrum of polymers suitable for quasi-isothermal PBF. Within the present paper, a novel approach for extending the isothermal processing window towards significantly lower temperatures by applying the quasi-simultaneous laser-based exposure of fractal scan paths is proposed. The proposed approach is based on the temporal and spatial discretization of the melting and subsequent crystallization of semi-crystalline thermoplastics, hence allowing for the mesoscale compensation of crystallization shrinkage of distinct segments. Using thermographic monitoring, a homogenous temperature increase of discrete exposed sub-segments, limited thermal interference of distinct segments, and the resulting avoidance of curling and warping can be observed. Manufactured parts exhibit a dense and lamellar part morphology with a nano-scale semi-crystalline structure. The presented approach represents a novel methodology that allows for significantly reducing energy consumption, process preparation times and temperature-induced material aging in PBF-LB/P while representing the foundation for the processing of novel, thermo-sensitive material systems in PBF-LB/P.

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Reznik, P. L., O. A. Chikova, and B. V. Ovsyannikov. "A Study of Flat Hot-Deformed Semiproducts Аl-Мg-Mn-Sc-Zr Microstructure, Phase Composition, Crystalline Structure and Mechanical Properties." Materials Science Forum 843 (February 2016): 117–22. http://dx.doi.org/10.4028/www.scientific.net/msf.843.117.

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The article investigates the influence of additional thermal treatment of an ingot before deformation on the microstructure, phase composition, crystalline structure, and mechanical properties of flat hot deformed semi-finished products made from Al-Mg-Mn-Sc-Zr aluminum alloy and presents the results obtained. Additional thermal processing of ingots before deformation was carried out in order to increase the level of the mechanical properties of semiproducts. Mechanical properties testing was carried out for both large-sized specimens and for sub-micro volumes of α-aluminum crystalline particles.

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Liu, Xuelian, Nicolas Desilles, Bo Jiang, Corinne Chappey, and Laurent Lebrun. "High barrier semi-crystalline polyesters involving nature occurring pyridine structure towards sustainable food packaging." Polymer 247 (April 2022): 124790. http://dx.doi.org/10.1016/j.polymer.2022.124790.

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ASAI, Shigeo. "The Control of Higher-Order Structure of Semi-Crystalline Polymers by Using Carbon Dioxide." Kobunshi 54, no. 9 (2005): 690. http://dx.doi.org/10.1295/kobunshi.54.690.

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Podgorbunskikh, Ekaterina, Timofei Kuskov, Vladimir Bukhtoyarov, Oleg Lomovsky, and Aleksey Bychkov. "Recrystallization of Cellulose, Chitin and Starch in Their Individual and Native Forms." Polymers 16, no. 7 (April 3, 2024): 980. http://dx.doi.org/10.3390/polym16070980.

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Semi-crystalline natural polymers are involved in many technological processes. Biopolymers having identical chemical compositions can differ in reactivity in heterogeneous transformations depending on their crystal structure (polymorphic modification). This paper compares the crystal structure recrystallization processes occurring in natural polysaccharides (cellulose, chitin, and starch) in the individual form and as a component of native biomass. Aqueous treatment of pre-amorphized semi-crystalline biopolymers was shown to result in swelling, thus alleviating the kinetic restrictions imposed on the restoration of crystalline regions and phase transition to the thermodynamically more stable polymorphic modification. During recrystallization, cellulose I in the individual form and within plant-based biomass undergoes a transition to the more stable cellulose II. A similar situation was demonstrated for α- and β-chitin, which recrystallize only into the α-polymorphic modification in the case of both individual polymers and native materials. Recrystallization of A-, B-, and C-type starch, both in the individual form and within plant-based flour, during aqueous treatment, results in a phase transition, predominantly to the B-type starch. The recrystallization process depends on the temperature of aqueous treatment; longer treatment duration has almost no effect on the recrystallization degree of polymers, both in the individual form and within native materials.

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Androsch, René, Katalee Jariyavidyanont, and Christoph Schick. "Enthalpy Relaxation of Polyamide 11 of Different Morphology Far Below the Glass Transition Temperature." Entropy 21, no. 10 (October 10, 2019): 984. http://dx.doi.org/10.3390/e21100984.

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Polyamide 11 (PA 11) samples of different supermolecular structure, including the crystal-free glass and semi-crystalline PA 11 of largely different semi-crystalline morphology, were prepared by fast scanning chip calorimetry (FSC). These samples were then annealed at different temperatures well below the glass transition temperature Tg. The main purpose of the low-temperature annealing experiments was the calorimetric detection of mobility of chain segments at temperatures as low as −40 °C (≈Tg − 80 K) where still excellent impact resistance is predicted. It was found that annealing PA 11 at such low temperature, regardless the thermal history and supermolecular structure including crystallinity as well as crystal shape and size, permits distinct enthalpy relaxation at rather short time scale with the structural changes reverting on subsequent heating as detected with pronounced sub-Tg-enthalpy-recovery peaks. The main glass transition, associated to large-amplitude segmental mobility, as well as relaxations at temperatures only slightly below Tg are even more distinctly sensitive to the crystal morphology. In contrast to spherulitically grown lamellar crystals, presence of high-specific-surface area nanometer-sized ordered domains causes a shift of the glass transition temperature of the amorphous phase to higher temperature, proving stronger coupling of ordered and amorphous phases than in case of lamellae. In addition, the increased coupling of the crystalline and amorphous phases slows down the cooperative rearrangements on annealing the glass slightly below Tg. The performed study contributes to further understanding of the spectrum of structural relaxations in PA 11 including the effect of presence of crystals. Enthalpy relaxation and consequently the reduction of entropy at temperatures slightly below Tg strongly depends on the semi-crystalline morphology, while an only minor effect is seen on low-temperature annealing at Tg − 80 K, possibly indicating different molecular mechanisms for the processes occurring in both temperature ranges. The low-temperature process even seems proceeding in the crystalline fraction of the material.

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41

Wu, Ruiqing, Jingjuan Lai, Yi Pan, Zhaohui Zheng, and Xiaobin Ding. "High-strain slide-ring shape-memory polycaprolactone-based polyurethane." Soft Matter 14, no. 22 (2018): 4558–68. http://dx.doi.org/10.1039/c8sm00570b.

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To enable shape-memory polymer networks to achieve recoverable high deformability with a simultaneous high shape-fixity ratio and shape-recovery ratio, novel semi-crystalline slide-ring shape-memory polycaprolactone-based polyurethane (SR-SMPCLU) with movable net-points constructed by a topologically interlocked slide-ring structure was designed and fabricated.

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42

Rajkumar, Ganeshalingam, Hind A. AL-Khayat, Felicity Eakins, Carlo Knupp, and John M. Squire. "The CCP13FibreFixprogram suite: semi-automated analysis of diffraction patterns from non-crystalline materials." Journal of Applied Crystallography 40, no. 1 (January 12, 2007): 178–84. http://dx.doi.org/10.1107/s0021889806048643.

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The extraction of useful information from recorded diffraction patterns from non-crystalline materials is non-trivial and is not a well defined operation. Unlike protein crystallography where one expects to see well behaved diffraction spots in predictable positions defined by standard space groups, the diffraction patterns from non-crystalline materials are very diverse. They can range from uniaxially oriented fibre patterns which are completely sampled as Bragg peaks, but rotationally averaged around the fibre axis, to fibre patterns that are completely unsampled, to either kind of pattern with considerable axial misalignment (disorientation), to liquid-like order and even to mixtures of these various structure types. In the case of protein crystallography, the specimen is generated artificially and only used if the degree of order is sufficient to yield a three-dimensional density map of high enough resolution to be interpreted sensibly. However, with non-crystalline diffraction, many of the specimens of interest are naturally occurring (e.g.cellulose, rubber, collagen, muscle, hair, silk) and to elucidate their structure it is necessary to extract structural information from the materials as they actually are and to whatever resolution is available. Even when synthetic fibres are generated from purified components (e.g.nylon, polyethylene, DNA, polysaccharides, amyloidsetc.) and diffraction occurs to high resolution, it is rarely possible to obtain perfect uniaxial alignment. The CCP13 project was established in the 1990s to generate software which will be generally useful for analysis of non-crystalline diffraction patterns. Various individual programs were written which allowed separate steps in the analysis procedure to be carried out. Many of these programs have now been integrated into a single user-friendly package known asFibreFix, which is freely downloadable from http://www.ccp13.ac.uk. Here the main features ofFibreFixare outlined and some of its applications are illustrated.

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Bucknall, David G., Gabriel Bernardo, Meisha L. Shofner, Deb Nabankur, Dharmaraj Raghavan, Bobby G. Sumpter, Scott Sides, Abul Huq, and Alamgir Karim. "Phase Morphology and Molecular Structure Correlations in Model Fullerene-Polymer Nanocomposites." Materials Science Forum 714 (March 2012): 63–66. http://dx.doi.org/10.4028/www.scientific.net/msf.714.63.

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In this work we have performed a systematic study of blends of [6,-phenyl C61 butyric acid methyl ester (PCBM) with the following amorphous and semi-crystalline polymers: atactic polystyrene (PS), syndiotactic polystyrene (syn-PS), poly (2-vinyl-naphthalene) (P2VN), poly (9-vinyl-phenanthrene) (P9VPh), poly (vinylidene-fluoride) (PVdF) and poly (3-hexyl-thiophene) (P3HT). Experimental measurements using DSC, x-ray and neutron scattering coupled with molecular modeling (MD and DFT) have been utilized to determine the solubility and phase morphology of these model polymer-fullerene blends.

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Hernandez, Marianella, Tiberio A. Ezquerra, and Miguel A. López-Manchado. "Effects of Orientation on the Segmental Dynamics of Natural Rubber." Materials Science Forum 714 (March 2012): 57–61. http://dx.doi.org/10.4028/www.scientific.net/msf.714.57.

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The effects of orientation on the segmental dynamics of vulcanized natural rubber have been studied by dielectric relaxation spectroscopy. Morphological changes during the stretching process were also investigated by wide-angle X-ray scattering using a synchrotron radiation. Results reveal that segmental dynamics of NR is affected by uniaxial stretching since a slowing down of the segmental relaxation is achieved. Also, there is evidence of an amorphous/semi-crystalline transition around 300% strain; below this extension, molecular chains show orientation, but no crystallization takes place; while above such strain, the crystalline structure formed limits the segmental dynamics of NR.

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Zhang, Ying, Mao Peng Geng, Lei Cheng, and Yan Chun Wang. "Influence of Processing Parameters on Microstructure of Casting Rolling Semi-Solid AZ91D Magnesium Alloy." Solid State Phenomena 141-143 (July 2008): 535–38. http://dx.doi.org/10.4028/www.scientific.net/ssp.141-143.535.

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Semi-solid AZ91D magnesium slurry was prepared by mechanical stirring method and the evolution of microstructure under different technological parameters such as casting temperature, standing time, stirring time and stirring speed et al were studied. The results show that the technological parameters have great influence on the microstructure of the semi-solid magnesium slurry. Neither too high nor too low stirring speed is a benefit to form the semi-solid state; stirring time is also not too long; higher casting temperature is unfavorable; with the increasing of standing time, the steady-state apparent viscosity of the slurry increases rapidly, the number of nucleation increases and the crystalline structure becomes finer.

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Arguelles, A., M. Leoni, J. A. Blanco, and C. Marcos. "Semi-ordered crystalline structure of the Santa Olalla vermiculite inferred from X-ray powder diffraction." American Mineralogist 95, no. 1 (December 23, 2009): 126–34. http://dx.doi.org/10.2138/am.2010.3249.

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de Oliveira, Lilian R., Lizandro Manzato, Yvonne P. Mascarenhas, and Edgar A. Sanches. "The influence of heat treatment on the semi-crystalline structure of polyaniline Emeraldine-salt form." Journal of Molecular Structure 1128 (January 2017): 707–17. http://dx.doi.org/10.1016/j.molstruc.2016.09.044.

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Stribeck, Norbert, Rüdiger Bayer, Peter Bösecke, and Armando Almendarez Camarillo. "Visualisation of the structure transfer between an oriented polymer melt and the semi-crystalline state." Polymer 46, no. 8 (March 2005): 2579–83. http://dx.doi.org/10.1016/j.polymer.2005.01.076.

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Shen, Xiaobo, Volodimyr V. Duzhko, and Thomas P. Russell. "A Study on the Correlation Between Structure and Hole Transport in Semi-Crystalline Regioregular P3HT." Advanced Energy Materials 3, no. 2 (September 24, 2012): 263–70. http://dx.doi.org/10.1002/aenm.201200509.

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Madhloom, Samara A. "Structural Properties of Nanoparticles TiO2/PVA Polymeric Films." Al-Mustansiriyah Journal of Science 28, no. 2 (April 11, 2018): 188. http://dx.doi.org/10.23851/mjs.v28i2.517.

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In this research, X-ray diffraction of the powder (PVA polymer, titanium dioxide with two parti-cle sizes) and (TiO2 (15.7 nm)/PVA and TiO2 (45.7 nm)/PVA) films have been studied,the amount of polymer is (0.5) g and (0.01)g from each particle sizes of nanoparticles will be used. Casting method is used to prepare homogeneous films on glass petri dishes. All parameters ac-counted for the X-ray diffraction; full width half maximum (FWHM), Miller indices (hkl), size of crystalline (D), Specific Surface Area (S) and Dislocation Density (δ). The nature of the structural of materials and films will be investigated. The XRD pattern of PVA polymer has semi-crystalline nature and the titanium dioxide with two particle sizes have crystalline structure; ana-tase type. While the mixture between these materials led to appearing some crystalline peaks into XRD pattern of PVA polymer

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Journal articles on the topic 'Semi-Crystalline structure'

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