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  • AIP Publishing  (10)
  • 1
    Online Resource
    Online Resource
    Growth direction of polyoxymethylene crystals inside irradiated trioxane crystals
    AIP Publishing ; 1973
    In:  Journal of Applied Physics Vol. 44, No. 10 ( 1973-10-01), p. 4293-4302
    Details
    In: Journal of Applied Physics, AIP Publishing, Vol. 44, No. 10 ( 1973-10-01), p. 4293-4302
    Abstract: The long slender crystals of polyoxymethylene that grew in irradiated trioxane crystals all grew toward the negative end of the trioxane crystal. The observed direction of growth was consistent with the assumption that the ion at the growing end of the polyoxymethylene chain was a cation. Certain morphological features such as facets and direction of taper of these polyoxymethylene crystals indicated the direction in which the crystals grew. Incidental observations of polyoxymethylene precursor crystals, electret domains in trioxane, and the effects of electron irradiation on polyoxymethylene crystals were made.
    Type of Medium: Online Resource
    ISSN: 0021-8979 , 1089-7550
    URL: Article
    DOI: 10.1063/1.1661954
    Language: English
    Publisher: AIP Publishing
    Publication Date: 1973
    detail.hit.zdb_id: 220641-9
    detail.hit.zdb_id: 3112-4
    detail.hit.zdb_id: 1476463-5
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  • 2
    Online Resource
    Online Resource
    Theory and observations of polymer crystal thickening
    AIP Publishing ; 1973
    In:  Journal of Applied Physics Vol. 44, No. 10 ( 1973-10-01), p. 4332-4339
    Details
    In: Journal of Applied Physics, AIP Publishing, Vol. 44, No. 10 ( 1973-10-01), p. 4332-4339
    Abstract: The thickening of polymer crystals during isothermal annealing is usually observed to be an irreversible process. Phenomenological laws that govern such processes take the form of simple proportionalities—flux being proportional to force. For polymer crystals, a thermodynamic force capable of driving the thickening phenomenon arises from the unequal free energies of the fold and lateral surfaces. By analogy with other irreversible phenomena, the rate of crystal thickening is taken to be proportional to the derivative of the surface free energy with respect to crystal thickness. After certain assumptions, integration yields an equation in which three parameters characterize the system: an initial thickness l0, an equilibrium thickness l*, and a relaxation time τ which is a function of the ``undercooling''. The theory provides a basis for considering the effects of parameters such as time, temperature, thermal history, pressure, and liquids on the thickening rate. In particular, the theory adequately describes the time and temperature dependence of crystal thickening in random copolymers of tetrafluoroethylene and hexafluoropropylene which exhibit thickening behavior completely analogous to that of homopolymers. During thickening, the unit cell dimensions of these quenched-crystallized copolymers decrease in a manner that is consistent with the concept of complete comonomer inclusion upon crystallization.
    Type of Medium: Online Resource
    ISSN: 0021-8979 , 1089-7550
    URL: Article
    DOI: 10.1063/1.1661961
    Language: English
    Publisher: AIP Publishing
    Publication Date: 1973
    detail.hit.zdb_id: 220641-9
    detail.hit.zdb_id: 3112-4
    detail.hit.zdb_id: 1476463-5
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  • 3
    Online Resource
    Online Resource
    Annealing and Melting of Polyoxymethylene Crystals Polymerized Within Irradiated Trioxane Crystals
    AIP Publishing ; 1971
    In:  Journal of Applied Physics Vol. 42, No. 12 ( 1971-11-01), p. 4606-4614
    Details
    In: Journal of Applied Physics, AIP Publishing, Vol. 42, No. 12 ( 1971-11-01), p. 4606-4614
    Abstract: Morphological changes produced by the annealing and melting of the polyoxymethylene crystals that polymerize inside irradiated trioxane crystals were observed. The crystals in which the polyoxymethylene chains were oriented parallel to the threefold axis of the trioxane underwent major reorganization when held at 184°C for 30 sec. The polyoxymethylene crystals in which the chain axis was inclined at a large angle with respect to the threefold axis of the trioxane transformed and melted at temperatures approximately 5°C lower.
    Type of Medium: Online Resource
    ISSN: 0021-8979 , 1089-7550
    URL: Article
    DOI: 10.1063/1.1659829
    Language: English
    Publisher: AIP Publishing
    Publication Date: 1971
    detail.hit.zdb_id: 220641-9
    detail.hit.zdb_id: 3112-4
    detail.hit.zdb_id: 1476463-5
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  • 4
    Online Resource
    Online Resource
    Melting Temperatures of Copolymers
    AIP Publishing ; 1966
    In:  Journal of Applied Physics Vol. 37, No. 9 ( 1966-08-01), p. 3511-3514
    Details
    In: Journal of Applied Physics, AIP Publishing, Vol. 37, No. 9 ( 1966-08-01), p. 3511-3514
    Abstract: The melting temperatures (532° to 580°K) of copolymers of tetrafluoroethylene and hexafluoropropylene have been measured on a microscope hot stage. The copolymers had concentrations of perfluoromethyl groups between 0.0275 and 0.075 groups per carbon atom and lamella thicknesses which varied from 340 to 500 Å independently of comonomer concentration. An equation based on the concept of inclusion of the groups within the lamellar crystals as defects has been fitted to the data. The constants of fitting yield the equilibrium melting temperature, 616.6°±4.9°K, the surface energy, 4.5×10−13±1.6×10−13 erg/fold, and the perfluoromethyl defect energy, 0.047±0.003 eV/defect. Within the limits of error, these values are shown to be satisfactory by the possible comparisons with previously reported values or with values deduced from physical models. Neglecting the effect of lamella thickness yields a significantly poorer fit of the data.
    Type of Medium: Online Resource
    ISSN: 0021-8979 , 1089-7550
    URL: Article
    DOI: 10.1063/1.1708891
    Language: English
    Publisher: AIP Publishing
    Publication Date: 1966
    detail.hit.zdb_id: 220641-9
    detail.hit.zdb_id: 3112-4
    detail.hit.zdb_id: 1476463-5
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  • 5
    Online Resource
    Online Resource
    Alpha Relaxation in Polyethylene
    AIP Publishing ; 1970
    In:  Journal of Applied Physics Vol. 41, No. 11 ( 1970-10-01), p. 4313-4316
    Details
    In: Journal of Applied Physics, AIP Publishing, Vol. 41, No. 11 ( 1970-10-01), p. 4313-4316
    Abstract: Data are presented to show that a previously reported correlation of the strength of the alpha relaxation in annealed solution-grown crystals of polyethylene with the inverse of lamella thickness is not unique. Nor is a previously reported dependence of relaxation temperature on lamella thickness unique. As the lamella thickness changes with annealing temperature, the unit cell dimensions, the macroscopic density, and the residual solvent content of the crystals also change. Thus, there are apparent correlations between these parameters and the relaxation strength and temperature. Since it is not obvious which, if any, of these correlations is the fundamental one with regard to the alpha relaxation, some caution must be exerted in interpreting them. As an example of this, data are discussed to suggest that there is at least one other presently unknown parameter of importance to the relaxation.
    Type of Medium: Online Resource
    ISSN: 0021-8979 , 1089-7550
    URL: Article
    DOI: 10.1063/1.1658461
    Language: English
    Publisher: AIP Publishing
    Publication Date: 1970
    detail.hit.zdb_id: 220641-9
    detail.hit.zdb_id: 3112-4
    detail.hit.zdb_id: 1476463-5
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  • 6
    Online Resource
    Online Resource
    Alpha Relaxation in Polyethylene
    AIP Publishing ; 1971
    In:  Journal of Applied Physics Vol. 42, No. 13 ( 1971-12-01), p. 5902-5903
    Details
    In: Journal of Applied Physics, AIP Publishing, Vol. 42, No. 13 ( 1971-12-01), p. 5902-5903
    Type of Medium: Online Resource
    ISSN: 0021-8979 , 1089-7550
    URL: Article
    DOI: 10.1063/1.1660047
    Language: English
    Publisher: AIP Publishing
    Publication Date: 1971
    detail.hit.zdb_id: 220641-9
    detail.hit.zdb_id: 3112-4
    detail.hit.zdb_id: 1476463-5
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  • 7
    Online Resource
    Online Resource
    Thermal Expansion of Polyethylene Unit Cell: Effect of Lamella Thickness
    AIP Publishing ; 1970
    In:  Journal of Applied Physics Vol. 41, No. 11 ( 1970-10-01), p. 4316-4326
    Details
    In: Journal of Applied Physics, AIP Publishing, Vol. 41, No. 11 ( 1970-10-01), p. 4316-4326
    Abstract: The unit cell dimensions have been measured at temperatures between 93 and 333 K for linear polyethylene samples with long periods of 385, 220, and 99 Å. The angular positions of 6 x-ray diffraction lines were obtained at 5–10 K intervals with a powder diffractometer and the positions corrected for beam penetration so as to agree with powder camera results obtained with more lines at 296 and 155 K. At lower temperatures, the cell dimensions are nearly independent of long period, but at higher temperatures, the basal area of the cell appears to vary linearly with the reciprocal of the long period. The value of the slope increases with temperature and at 293 K is nearly the same for sets of data obtained with a number of different molecular weight distributions, crystallization and annealing conditions as well as for n-paraffins. The specific volume data for all three polymer samples can be represented between 133 and 333 K with a standard deviation of 2.6×10−4 cm3 g−1 by the equation V=0.8341(1055.5−T)/(931.7−T)+(0.12−1.6×10−3T+7.8×10−6T2)/l2in which V is in cm3 g−1, T is °K and l2 is the long period expressed in angstroms. It is concluded that the interaction of the molecules at the surface of the crystal is not as important as the length of the molecular stems between the folds in affecting the dimensions at higher temperatures. The stems probably alter the dimensions through their effect on the thermal energy. The dependence of crystal specific volume on crystal size is estimated to reduce the heat of fusion of small crystals by about 2% in the normal range of long period. Neglecting this in analyzing melting-temperature-lamella-thickness data can lead to errors of the order of 3% in the surface free energy and 0.3 K in the equilibrium melting temperature. The variation of crystal specific volume accounts for about 5% of the variation of macroscopic specific volume and constant pressure specific heat with long period.
    Type of Medium: Online Resource
    ISSN: 0021-8979 , 1089-7550
    URL: Article
    DOI: 10.1063/1.1658462
    Language: English
    Publisher: AIP Publishing
    Publication Date: 1970
    detail.hit.zdb_id: 220641-9
    detail.hit.zdb_id: 3112-4
    detail.hit.zdb_id: 1476463-5
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  • 8
    Online Resource
    Online Resource
    Trans-gauche concentration in crystalline polyethylene measured by the intensity of rocking mode vibrations of deuterated methylene groups
    AIP Publishing ; 1980
    In:  Journal of Applied Physics Vol. 51, No. 10 ( 1980-10-01), p. 5080-5094
    Details
    In: Journal of Applied Physics, AIP Publishing, Vol. 51, No. 10 ( 1980-10-01), p. 5080-5094
    Abstract: Polyethylene with a low concentration of deuterated methylene groups displays an infrared band in the frequency region 646–651 cm−1. This band is attributed to a rocking normal mode of a CD2 group with one of the adjacent dihedral angles approximately trans and the other approximately gauche (tg). This mode vibrates at 620 cm−1 when the dihedral angles adjacent to the CD2 group are both trans (tt). In polyethylene crystals tg sequences can occur only in defects where constraints cause some of the dihedral angles to be approximately trans or gauche. Calculations of the rocking mode vibrational frequencies of CD2 groups in model chains which incorporate some of the typical defects showed that the bands were broadened but not completely disrupted by the distorted dihedral angles. Measurements of the relative intensities of the CD2 rocking bands show an increase in the concentration of tg sequences consistent with the thermal generation of defects which may be involved in transport of the polymer chain through the crystal. Confidence in the particular values of the concentration ratio is limited by uncertainties in the determination of the base line for the infrared bands of interest. Quantitative measurements of the concentration ratio tg/(tg+tt), determined from the integrated band intensities, fall between limits set by reasonable independent estimates of the concentration of folds and point dislocations.
    Type of Medium: Online Resource
    ISSN: 0021-8979 , 1089-7550
    URL: Article
    DOI: 10.1063/1.327424
    Language: English
    Publisher: AIP Publishing
    Publication Date: 1980
    detail.hit.zdb_id: 220641-9
    detail.hit.zdb_id: 3112-4
    detail.hit.zdb_id: 1476463-5
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  • 9
    Online Resource
    Online Resource
    Influence of parasitic phases on the properties of BiFeO3 epitaxial thin films
    AIP Publishing ; 2005
    In:  Applied Physics Letters Vol. 87, No. 7 ( 2005-08-15)
    Details
    In: Applied Physics Letters, AIP Publishing, Vol. 87, No. 7 ( 2005-08-15)
    Abstract: We have explored the influence of deposition pressure and temperature on the growth of BiFeO3 thin films by pulsed laser deposition onto (001)-oriented SrTiO3 substrates. Single-phase BiFeO3 films are obtained in a region close to 10−2mbar and 580°C. In nonoptimal conditions, x-ray diffraction reveals the presence of Fe oxides or of Bi2O3. We address the influence of these parasitic phases on the magnetic and electrical properties of the films and show that films with Fe2O3 systematically exhibit a ferromagnetic behavior, while single-phase films have a low bulklike magnetic moment. Conductive-tip atomic force microscopy mappings also indicate that Bi2O3 conductive outgrowths create shortcuts through the BiFeO3 films, thus preventing their practical use as ferroelectric elements in functional heterostructures.
    Type of Medium: Online Resource
    ISSN: 0003-6951 , 1077-3118
    URL: Article
    DOI: 10.1063/1.2009808
    RVK:
    UA 1000
    Language: English
    Publisher: AIP Publishing
    Publication Date: 2005
    detail.hit.zdb_id: 211245-0
    detail.hit.zdb_id: 1469436-0
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  • 10
    Online Resource
    Online Resource
    Polyoxymethlene Crystals Grown Within Irradiated Trioxane Crystals
    AIP Publishing ; 1970
    In:  Journal of Applied Physics Vol. 41, No. 11 ( 1970-10-01), p. 4296-4312
    Details
    In: Journal of Applied Physics, AIP Publishing, Vol. 41, No. 11 ( 1970-10-01), p. 4296-4312
    Abstract: The morphological development of polyoxymethylene crystals polymerized from and grown within trioxane crystals was observed following irradiation of the trioxane with alpha particles and a subsequent heat treatment. A novel method of sample preparation enabled the morphology to be observed in detail and resulted in the discovery of new forms of polyoxymethylene crystals as well as an improved description of previously reported forms. A solid-gas-solid crystal growth mechanism was postulated to account for the predominantly acicular habit of the polyoxymethylene crystals.
    Type of Medium: Online Resource
    ISSN: 0021-8979 , 1089-7550
    URL: Article
    DOI: 10.1063/1.1658460
    Language: English
    Publisher: AIP Publishing
    Publication Date: 1970
    detail.hit.zdb_id: 220641-9
    detail.hit.zdb_id: 3112-4
    detail.hit.zdb_id: 1476463-5
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