Materials Literature
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The thermal degradation mechanisms of poly[2,2′-bis(3,4-dicarboxyphenoxy)phenylpropane-2-phenylenediimide] (PEI) have been investigated by thermogravimetry (TG) and by direct pyrolysis mass spectrometry (DPMS). TG data show that PEI has a main decomposition step centred at about 510°C followed by a less marked step in…
The stability and fluctuations of the cylinder (C) and sphere (S) morphologies in the vicinity of the C and S equilibrium have been examined for a poly(styrene- b -isoprene- b -styrene) triblock copolymer by rheology, small-angle X-ray scattering (SAXS), and transmission electron microscopy (TEM). The spinodal tempera…
Hydroxyapatite (HAP) obtained from aqueous solutions under different conditions has been examined by high-resolution transmission electron microscopy (HRTEM) and electron diffraction, including selected-area electron diffraction (SAED) and microdiffraction. A Philips CM300 field-emission gun electron microscope with a…
Paint systems containing color-change or fluorescing compounds were found to be sensitive to underlying corrosion processes by reacting to the pH increase associated with the cathodic reaction that accompanies corrosion. The sensitivity of acrylic-based coating systems for detection of cathodic reactions associated wi…
The manufacture of fine‐grained SiC ceramics by using nanophase SiC powders with particle sizes of about 20 nm is described. Conventional sintering of these powders led to extreme grain growth and hence the nanophase microstructure was destroyed. Pressure‐assisted sintering was applied to reduce the sintering temperat…
Monodomain acrylate-based networks have been synthesized by a two-step cross-linking procedure using gamma-irradiation. Strain-induced reorientation of the nematic director is studied by X-ray diffraction measurements. The geometrical shape (aspect ratio) of the monodomain films is found to affect drastically the dyna…
There is a growing demand for the examination of protein microcrystals at third-generation synchrotron sources. After successful pilot experiments at EMBL/ESRF, which proved that protein microcrystals are often suitable for data collection, operation of the microfocus beamline ID13 was made more user-friendly and suit…
We report the observation of photoluminescence (PL) originating from defects created by the visible and near-infrared irradiation of vitreous silica. Three PL bands at 283, 468, and 558 nm exhibited excitation spectra peaking at 250 nm, which corresponds to the oxygen vacancy defect ${V}_{\mathrm{O}}$ absorption. The…
Er 2 O 3 ‐doped PbO‐Bi 2 O 3 ‐Ga 2 O 3 glasses were prepared through the conventional melt‐quenching method, and the energy transfer mechanisms in Er 3+ were investigated. The fluorescent emission at 2.73 μm, which is normally quenched in silicate glasses, became evident because of the low phonon energy of PbO‐Bi 2 O…
The latest results on the use of porous silicon (PS) as an antireflection coating (ARC) in simplified processing for multicrystalline silicon solar cells are presented. The optimization of a PS selective emitter formation results in a 14.1% efficiency multicrystalline (5/spl times/5 cm/sup 2/) Si cell with evaporated…
Bismuth nanocrystals, embedded in amorphous germanium thin films and synthesized by pulsed-laser deposition, are investigated by Raman spectroscopy. Raman spectra are strongly dependent upon the size of the deposited nanocrystals. For the larger nanocrystals, two peaks corresponding to the optical phonons ${A}_{1g}$ a…
The three-dimensional crystal structure of hen apo-ovotransferrin has been solved by molecular replacement and refined by simulated annealing and restrained least squares to a 3.0-A resolution. The final model, which comprises 5312 protein atoms (residues 1 to 686) and 28 carbohydrate atoms (from two monosaccharides a…
The purpose of the present study is to develop an understanding of the photoluminescence properties of Mn 2+ ‐doped zinc silicate (Zn 2 SiO 4 :Mn) phosphors, which have served as a gree‐emitting phosphor in many industrial applications. Thus, several experimental techniques, such as time‐resolved emission spectra, dec…
Constitutive relations for a binary mixture of nearly elastic, circular disks are derived using the Revised Enskog Theory. Viscosity results from hard disk simulations are compared to the Enskog viscosity for a radii ratio of 1.25. The agreement is good up to an area fraction of 0.40. In the Appendix, we provide brack…
The present article examines the in‐plane tensile properties of a two‐dimensional (2D) all‐oxide ceramic composite. The distinguishing characteristics of the material include fine‐scale porosity within the matrix and the absence of a fiber coating. The anisotropy in the elastic‐plastic properties has been studied thro…
The grafting of polystyryllithium onto chloroethyl ether functions of poly(chloroethyl vinyl ether) (PCEVE) chains is a selective reaction which allows the complete substitution of chloride of CEVE units by polystyrene (PS) chains. Since the PCEVE polymer backbone and the PS grafts can be prepared by living cationic a…
The thermal degradation of poly(lactic acid) has been studied using thermal gravimetric analysis over the temperature range 300–700 K, and following a sterilization dose of 50 kGy under vacuum, nitrogen or air. Isothermal weight loss studies have been found to follow complex kinetics with activation energies determine…
To determine the dissipation induced by the surface of fused silica fibers, we measured the quality factor of fibers having various diameters. We measured a maximum quality factor of 21 million and extrapolated to obtain an intrinsic quality factor for fused silica of 30 million. Dissipation in the surface dominated a…
By relating the structural changes measured using the pair density function analysis of pulsed neutron data for ${\mathrm{LaCoO}}_{3},$ we provide evidence for the evolution of the magnetic state with temperature, from the low-spin state to partial occupation of the intermediate spin (IS) and to the high-spin states.…
Nanoporous carbons (NPCs) are useful in adsorptive separations and catalysis, owing to their ability to discriminate between molecules on the basis of size and shape. This property arises from their narrow pore size distribution, which is typically centred at a size corresponding to 0.5 nm. Despite this level of nanor…