Materials Literature
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Nitrogenated and hydrogenated amorphous carbon (a-C:H:N) films have been deposited by a plasma beam source using a gas mixture of C2H2, Ar and N2. The Ar/C2H2 ratio is kept constant at a ratio of 3, with the nitrogen flow allowed to vary. Nonnitrogenated films, with Ar/C2H2 ratios of 3 and 6 were also deposited and an…
We report in situ measurements of four-probe dc resistance (R) and thermopower (S) of Cs- and K-doped single-wall carbon nanotube (SWNT) mats as a function of a doping and temperature (T). With increasing dopant exposure, the mat resistance has been found to first decrease and then increase, exhibiting a minimum for o…
We study the conductance of carbon nanotube wires in the presence of disorder, in the limit of phase-coherent transport. For this purpose, we have developed a simple numerical procedure to compute transmission through carbon nanotubes and related structures. Two models of disorder are considered, weak uniform disorder…
Surfactant-mediated transport of insoluble, hydrophobic polymers can be exploited to produce a novel interleaved metal oxide/polymer composite containing poly(p-phenylene). The synthetic route is illustrated in the scheme, whereby a surfactant bilayer between the MoO3 layers is displaced by the PPP/surfactant dispersi…
New AB 2 type monomers, with a various number of phenylene units, were prepared and converted to hyperbranched poly(ether ketones) by polymerization. Four kinds of AB 2 type monomers, 4-hydroxy-3‘,5‘-bis(4-fluorobenzoyl)-biphenyl, 1, 4-hydroxy-3‘‘,5‘‘-bis(4-fluorobenzoyl)- p -terphenyl, 2, 4-hydroxy-3‘‘‘,5‘‘‘-bis(4-fl…
Two series of thermoplastic polyurethane elastomers [poly(propylene glycol) (PPG) based PP samples and poly(oxytetramethylene)glycol (PTMG) based PT samples] were synthesized from isophorone diisocyanate (IPDI)/1,4-butanediol (BD)/PPG and IPDI/BD/PTMG. The IPDI/BD based hard segments contents of polyurethane prepared…
Ln 2 CuSnO 6 (Ln = Pr, Nd, and Sm) and La 2 CuZrO 6 have been stabilized in the same layered double perovskite structure as La 2 CuSnO 6 at high pressures of 6−8 GPa. Their crystal structures and magnetic properties were investigated. Replacement of La 3+ by smaller lanthanide ions and Sn 4+ by larger Zr 4+ increased…
The biodegradable poly(L-lactide-co-trimethylene carbonate) [poly(LLA-co-TMC)] was synthesized by molten ring-open copolymerization and the structure and properties of the copolymer were investigated by GPC, NMR, FTIR, DSC, and Instron testing. The copolymer with a higher LLA content had a higher initial molecular wei…
Optical conductivity spectra of single crystals of the perovskite-type ${3d}^{1}$ metallic alloy system ${\mathrm{Ca}}_{1\ensuremath{-}x}{\mathrm{Sr}}_{x}{\mathrm{VO}}_{3}$ have been studied to elucidate how the electronic behavior depends on the strength of the electron correlation without changing the nominal number…
The electrical resistivity, magnetization, dilatation and sound velocity have been measured for La 1- X Sr X MnO 3 (0.48≤ X ≤0.90) polycrystals. Observed anomalies in the sound velocity and the dilatation strongly suggest the occurrence of the charge ordering within the Sr concentration range 0.48≤ X ≤0.82. A phase di…
A variety of polyethylenes were investigated over a range of drawing temperatures by the simultaneous measurement of the small- and wide-angle X-ray scattering patterns and the load−extension curve and were all found to undergo a similar sequence of deformation processes under 90 °C. Interlamellar separation was ident…
We predict the formation of GaSe nanotubes from an energetic argument which employs pseudopotential density functional theory methods. The strain energy of GaSe nanotubes is found to be comparable to existing carbon nanotubes. Based on this energetic comparison, we expect GaSe nanotubes with diameters of 40--48 \AA{}…
The effect of noncrystallizable units on the crystallization and melting was studied for two octene copolymers of syndiotactic polypropylene, in an extension of previous investigations on a homopolymer sample with 3% meso diads. Using time and temperature dependent SAXS experiments and DSC, we determined the dependenc…
The transition from microcrystalline to nanocrystalline diamond films grown from Ar/H2/CH4 microwave plasmas has been investigated. Both the cross-section and plan-view micrographs of scanning electron microscopy reveal that the surface morphology, the grain size, and the growth mechanism of the diamond films depend s…
We have studied the electronic structure of Mn impurities in GaAs by Mn $2p$ core-level photoemission spectroscopy. From cluster-model analysis assuming the neutral $({\mathrm{Mn}}^{3+})$ or negatively ionized $({\mathrm{Mn}}^{2+})$ ground state, electronic structure parameters have been obtained. In either case, the…
The layered pnictide titanates ${\mathrm{Na}}_{2}{\mathrm{Pn}}_{2}{\mathrm{Ti}}_{2}\mathrm{O}$, $Pn=\mathrm{Sb}$ and As, display anomalies in the susceptibility and resistivity that have not yet been associated with either magnetic ordering or with structural distortion. Based on local spin-density approximation calcu…
Flyash is an inexpensive material that can reduce the overall cost of the composite if used as a filler for unsaturated polyester resin (PR). Flyash-filled unsaturated polyester resin (FPR) was cast into sheets. The tensile strength, flexural strength, and flexural modulus were determined. Calcium carbonate-filled pol…
Predicted earlier, microcracks on the crystal surface of both finely dispersed $LiYF_4$ powders and single crystals of the Van Vleck paramagnet $% LiTmF_4$ were detected by using the NMR Cryoporometry and Atomic-Force Microscopy technique.
It has been observed that in bulk and polycrystalline thin films of colossal magnetoresistive (CMR) materials the magnetoresistance follows a different behavior compared to single crystals or single crystalline films below the ferromagnetic transition temperature Tc. In this paper we develop a phenomenological model t…
The temperature-dependent electronic structure has been investigated for a single crystal of magnetite $({\mathrm{Fe}}_{3}{\mathrm{O}}_{4})$ by measurements of the optical-conductivity spectrum. Upon the charge-ordering (Verwey) transition ${(T}_{V}=121 \mathrm{K})$, a clear opening of the optical gap (0.14 eV) is obs…