Materials Literature
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The hydrostatic shape, transient deformation, and asymptotic shape of a small liquid drop with uniform surface tension adhering to a planar wall subject to an overpassing simple shear flow are studied under conditions of Stokes flow. The effects of gravity are considered to be negligible, and the contact line is assum…
Supercritical fluid (SCF) technology involving carbon dioxide is recently receiving wide attention due to its vast potential application in various fields such as cleaning, extraction, synthesis, etc., in addition to its environmental benefits. To fully exploit the use of SCFs in new technologies, it is important to u…
In continuation of our goal to implement supercritical fluid (SCF) technology for various applications such as precision cleaning, foaming, and impregnation of materials, a systematic study has been performed involving amorphous polymers. Eleven different polymers of amorphous nature have been subjected to supercritic…
The effects of carbon black loadings ℓ, Temperature T, and shear frequency ω on dynamic mechanical properties of EPDM gum elastomer and its carbon black compounds were investigated under sinusoidal shear flows. The regions of shear flows where the gum elastomer and its carbon black compounds exhibited characteristic p…
The amorphous phase of a series of random 6/6.9 copolyamides was investigated. It was characterized by the glass transition temperature (Tg) and the hydrogen bond content, as a function of the copolymer composition, compared to the corresponding homopolymers, polyamide 6 and polyamide 6.9. The hydrogen bonds in the am…
Polypropylene (PP) was extruded and injection-molded several times to mimic the effect of recycling procedures on PP. Differential scanning calorimetry (DSC) was used to follow crystallization rates under isothermal conditions in a temperature range of 120–150°C. Melting behavior and equilibrium melting temperatures w…
Polypropylene (PP) was extruded and injection-molded several times to mimic the effect of recycling procedures on PP. Differential scanning calorimetry (DSC) was used to follow crystallization rates under isothermal conditions in a temperature range of 120–150°C. Melting behavior and equilibrium melting temperatures w…
The chemical grafting of acrylamide-methacrylic acid (AAM-MAA) mixture onto poly(ethylene terephthalate) (PET) fibers using azobisisobutyronitrile as a chemical initiator was investigated. The use of MAA as a comonomer increased the amount of AAM introduced to the PET fiber up to 33.0%, while the grafting of AAM onto…
Aromatic polyimides were synthesized from 2,2-bis(3-amino-4-hydroxyphenyl)hexafluoropropane (6F-OH diamine) and different aromatic dianhydrides by a one-step hightemperature polycondensation, or by a two-step procedure using either thermal or chemical imidization of poly(amic acids), PAA. The obtained polyimides were…
The ultraviolet spectra of pure and lead salt-poly(vinyl alcohol) (PVA) composite films were studied at room temperature. Blending of PVA with lead acetate and lead nitrate cause a considerable change in the UV spectrum, indicating electronic structure modifications. The complex permittivity (ϵ*) and the complex elect…
In continuation of our goal to implement supercritical fluid (SCF) technology for various applications such as precision cleaning, foaming, and impregnation of materials, a systematic study has been performed involving amorphous polymers. Eleven different polymers of amorphous nature have been subjected to supercritic…
Supercritical fluid (SCF) technology involving carbon dioxide is recently receiving wide attention due to its vast potential application in various fields such as cleaning, extraction, synthesis, etc., in addition to its environmental benefits. To fully exploit the use of SCFs in new technologies, it is important to u…
Dendritic molecules have been constructed with only silicon−silicon linkages. Crystal structures have been obtained for three such molecules in which the core silicon is bonded to three silicons and each polysilyl wing branches once (one dendrimer generation). The three crystal structures differ in the number of space…
A Monte Carlo method, namely, the ‘‘statistical counting method’’ (SCM) has been proposed for simulating the conformational entropy of a single free or confined linear self-avoiding random walk chains on the simple cubic lattice. For a free linear chain with length 1081, it is found from the calculated results of 100…
We present and compare results from Monte Carlo and self-consistent-field studies of a grafted brush of polyelectrolyte chains (of length N), interacting via a screened-Coulombic potential. We examine the brush under a variety of grafting and screening conditions and investigate the various régimes of this system. The…
We have studied the photoluminescence at 1.5 μm of the 4I13/2→4I15/2 transition of the Er3+ ion, incorporated as ErF3 into polycrystalline YF3, LuF3, and LaF3 films, deposited onto SiO2 or Si wafers. We conclude that LaF3 is an exceptionally suitable host for Er3+, since it permits high Er3+ concentrations, long lifet…
Raman measurements have been carried out on Si clusters embedded in porous Si (PS). Conspicuous new Raman peaks are observed, and are identified as surface modes of Si clusters and their combination with TA modes. Good agreement is achieved between the observed Raman peaks and calculated results. The Si clusters drop…
The Raman spectra of MoO3 implanted with 1, 2, and 4×1016 H+/cm2 have been recorded at room temperature. It was found that most of the Raman modes of Ag and Bg symmetry, which are observed between 100 and 1100 cm−1, decrease in intensity by the electronic screening of phonons as a result of the electron transfer from…
From an expression for the energy of a cell containing an antiferroelectric smectic liquid crystal with only nearest-neighbor interactions between layers we conclude the following: (1) a critical cell thickness exists at which the commensurability of the system changes from unity to higher values; (2) for negative die…
In single crystals of the dimer compound Cs3Y2Br9:10% Yb3+ below 31 K, both visible (VIS) and near-infrared (NIR) luminescence intensities were found to exhibit hysteresis as a function of incident NIR intensity and temperature. The optical bistability is intrinsic to Cs3Y2Br9:10% Yb3+ and not a result of an external…