Materials Literature
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The synthesis and liquid crystalline behaviour of the first and second generations of a dendrimeric structure based on poly(propyleneimine)(DAB-dendr(NH2)x) are reported. 4-(4-n-Alkoxybenzoyloxy)salicylaldehydes are used as mesogenic moieties attached at the peripheral amino groups of the dendrimers giving rise to den…
Different glasses in the system xPbF2: (1 — x)[PbO : TeO2] have been synthesized and investigated. The effects of increasing PbF2 contents on material properties such as glass transition temperature (Tg), thermal expansion coefficient (α), microhardness (Hv), and electrical conductivity (σ) are studied. Addition of Pb…
The surface of porous silica particles was modified with poly(acrylic acid) by reacting the carboxyl groups on poly(acrylic acid) with the amino groups of pregrafted aminopropyltriethoxysilane (APS). The chemical modifications by APS and polymer were characterized by infrared spectroscopy and the amount of APS and pol…
Heating of polystyrene beads containing pentane isomers as the blowing agent traditionally produces polystyrene foam. Undesirable emissions of the blowing agent and its high flammability are the complications of this process. A new process for the production of expandable polystyrene has been developed, using water as…
Foams have been used for several decades to decrease the mobility of drive gas or steam, thereby enhancing the reservoir sweep efficiency. More recently foams found application in near-wellbore production enhancement operations such as acid diversion for matrix stimulation, gas shut-off, water shut-off and hydraulic f…
The thermo-insulating properties of both perpendicular- and conventional cross-laid lofty nonwoven fabrics, four different types each in terms of fiber fineness, are investi gated using a new static method with a heat flux sensor. The relationship between the thermal conductivity and the material density of all the sa…
Nucleation and growth of stable and metastable crystalline phases are described in the framework of a single-order parameter Cahn–Hilliard theory. A piecewise parabolic free-energy order parameter relationship composed of three parabolas of positive curvature coefficient has been adopted. The analytical solution of th…
ADVERTISEMENT RETURN TO ISSUEPREVCommunicationNEXTSynthesis of a NdAlO3/Al2O3 Ceramic−Ceramic Composite by Single-Source Precursor CVD†Michael Veith, Sanjay Mathur, Nicolas Lecerf, Karsten Bartz, Manuela Heintz, and Volker HuchView Author Information Institute of Inorganic Chemistry, University of Saarland, D-66123 Sa…
The magnetoresistance (MR) of icosahedral Al-Pd-Re of nominal composition ${\mathrm{Al}}_{70.5}{\mathrm{Pd}}_{21}{\mathrm{Re}}_{8.5},$ and with resistance ratios R [=\ensuremath{\rho}(4 K)/\ensuremath{\rho}(295 K)] from 2 to 120, has been measured in the range 0.1--40 K in magnetic fields up to 12 T. Three regions of…
Electron-spin-resonance (ESR) and dielectric spectroscopy techniques have been applied to study the dipole centers connected with ${\mathrm{Mn}}^{2+}$ and ${\mathrm{Fe}}^{3+}$ impurity ions substituted for ${\mathrm{K}}^{+}$ in the incipient ferroelectric ${\mathrm{KTaO}}_{3}.$ It was shown that the reorientations of…
Self-consistent approaches for quantification of the phase composition of ordered mesoporous materials (OMMs) are proposed on the basis of powder X-ray diffraction (XRD), and, for the first time, on the basis of gas adsorption and thermogravimetry (TGA). A series of hexagonal MCM-41 samples containing different amount…
A method of powder diffraction analysis is proposed that is applicable to transition metal nanoparticles and which has been applied to palladium. From results of simulations it is shown that: ( a ) the overall average lattice constant of small transition metal clusters decreases with decreasing size of the cluster as…
The present study investigated the in vitro mechanism and degradation rate of polyhydroxyoctanoate (PHO). Solution-cast PHO films were incubated in either water or isoosmotic phosphate-buffered saline (PBS) for periods ranging from 1 to 24 months. Physical characterization included weight loss, water absorption, pH ch…
The crystal structure of α-silicon nitride (Si 3 N 4 ) was refined by the Rietveld method using synchrotron radiation powder diffraction data (wavelength = 1.2 Å) collected at station BL-4B2 in the Photon Factory. A refinement procedure that adopted a new weight function, w = 1/Y_o^e ( Y o is the observed profile inte…
A variety of physico-chemical methods employ chemical denaturants to unfold proteins, and study different biophysical processes involved therein. Chemical denaturants are believed to induce unfolding by stabilizing the unfolded state of proteins over the folded state, either macroscopically or through specific interac…
The effect of the ac electric field on piezoelectric properties is investigated in lead zirconate-titanate (PZT) films of various compositions and thicknesses. Non-linear piezoelectric properties of PZT films are compared to those of bulk ceramics. It is shown that non-linearity is strongly suppressed in thin films of…
The influence of an asymmetric periodic grooved cell surface on the 2D static director configuration of a nematic liquid crystal has been investigated. The minimum in the Frank-Oseen free energy was solved numerically with the Rapini-Papoular form of the surface anchoring energy at the nematic-grating interface. Resul…
New ferrocenyloligosilylene aryl complexes have been synthesized, FcSi n Me 2 n C 6 H 5 ( n = 1−6) and FcSi 2 Me 4 {C 6 H 4 -X} (X = m -CF 3 . p -Cl, p -Br, p -OMe, p -NMe 2, p -CH C(CN) 2 ). The complexes have been evaluated with respect to their electrochemical redox and NLO hyperpolarizability properties. All compl…
The hyperfine parameters of iron atoms are studied in iron nanocrystallites prepared by different methods: ball milling of iron powder, partial crystallization of Fe-Zr-B-Cu amorphous ribbons, and vacuum evaporation of Fe-B polycrystalline multilayers. Careful analysis of the spectral contribution of the possible impu…
In actuator technology active or smart materials have opened up new horizons in terms of actuation simplicity, compactness, and miniaturization potential. One such material is the nickel-titanium shape memory alloy (NiTi SMA), which is gaining widespread use in a variety of applications. The numerous advantages of SMA…