Materials Literature
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Fixtured sintering of up to 5 hours at 1223 to 1323 K is successfully used to diminish the dimensional change of NiTi memory alloys produced from mixtures of elemental Ni and Ti powders packed and pressed at room temperature under 400, 500, and 600 MPa pressure. The improvements obtained can help near-net-shape techno…
A nanocomposite material, composed of nano-sized MgO-filler added to a low-density polyethylene (LDPE), was subjected to electrical property investigations under DC voltage application. The volume resistivity of LDPE, under 40-80 kV/mm DC field at 90 /spl deg/C, increases by the power of 10 due to the addition of only…
Abstract Summary: In this work, epoxy resin/CaCO 3 nanocomposites were prepared by in situ and inclusion polymerization. Nanoparticles with a size of 30–40 nm were dispersed efficiently in bisphenol‐A alkaline solution before polymerization and the dispersion could be kept in the resultant composite by a reaction that…
[reaction: see text] An improved methodology for the N-alkylation of the porphyrin isomer N-confused porphyrin is presented. The combination of polar solvent conditions and the use of the base Cs2CO3 affords externally modified products in high yield without separation difficulties and without the use of large excesse…
A general macromodel of the phase change random access memory (PCRAM) elements for use in HSPICE-based computer simulator is proposed in this paper by introducing physical models of PCRAM elements. It can simulate the dc and transient behavior of PCRAM element. In this paper, the model was integrated with the standard…
Copolymerization of lactide, epsilon-caprolactone, and trimethylene carbonate is performed. The synthesis is focused on obtaining materials with adequate properties for application as a suture coating that could contain an antimicrobial agent like triclosan. An amorphous character, a low glass transition temperature,…
Abstract Summary: Hydroxyethylcellulose (HEC) was synthesized by a fully homogenous method from cellulose in 7.5 wt.‐% NaOH/11 wt.‐% urea aqueous solutions under mild conditions. HEC samples were characterized with NMR, SEC‐LLS, solubility, and viscosity measurements. The MS and DS values of the obtained HEC samples a…
By the reaction of the appropriate organometallic precursors and tetrakishydroxymethyl phosphonium chloride (THPC) at the toluene-water interface, we have prepared nanocrystalline films of Au-Ag and Au-Cu alloys with a range of compositions. The films have been characterized by X-ray diffraction, electron microscopy,…
The synthesis and magnetic properties of the high-spin tetranuclear cluster [Mn(III)(2)Mn(II)(2)(O(2)CC(CH(3))(3))(2)(teaH(2))(2)(teaH)(2)](O(2)CC(CH(3))(3))(2) (1) (where teaH(3) = triethanolamine) is described. Complex 1 is the pivalate analogue of our previously reported family of tetranuclear mixed-valence carboxy…
A new gas injection/specimen heating holder is developed for the purpose of in situ observation of gas reaction of materials at high temperatures in a transmission electron microscope at near-atomic resolution. A fine tungsten wire is employed as a heating element of the holder and a battery is used as the power sourc…
We report the adsorption isotherms and the isosteric heats of adsorption of pure methane, ethane, and CO2 and a mixture of methane and CO2 in the periodic mesoporous silica MCM-41 using a multicomponent adsorption calorimeter of the Tian-Calvet type, looking in particular at the degree of heterogeneity in the adsorpti…
Single walled carbon nanotubes (SWNTs) have been functionalized in a mixture of 96% sulfuric acid and ammonium persulfate, using sodium nitrite to produce intermediate diazonium salts from substituted anilines. These afford unbundled functionalized SWNTs from bulk bundled SWNTs. This new process eliminates the need fo…
A novel ultrathin enzymatically degradable multilayered film using DNA as building blocks was fabricated by the layer-by-layer (LbL) technique. The UV-vis spectrometry and AFM experiments showed that the buildup of DNA and poly-L-lysine (PLL) was a kind of "exponentially growing films". The dye adsorption experiment s…
The origin of a recently reported peculiar phenomenon---polarization reversal against the applied electric field in ferroelectric thin films [M. Aplanalp and P. G\"unter, Ferroelectrics 258, 3 (2001), T. Morita and Y. Cho, Appl. Phys. Lett. 84, 257 (2004)]---has been identified. The phenomenon is observed when poling…
Abstract Summary: Ultrasonic irradiation was employed to prepare polypyrrole (PPY)/Fe 3 O 4 magnetic nanocomposite by chemical oxidative polymerization of pyrrole in the presence of Fe 3 O 4 nanoparticles. This approach can solve the problem in the dispersion and stabilization of inorganic nanoparticles in polymer. Th…
A new beamline, fully dedicated to X-ray powder diffraction (XPD) measurements, has been installed after the exit port B of the bending magnet D10 at the Brazilian Synchrotron Light Laboratory (LNLS) and commissioned. The technical characteristics of the beamline are described and some performance indicators are liste…
Abstract Hybrid thin films of conjugated polymers and CdSe nanoparticles have been fabricated by using a layer‐by‐layer (LbL) approach driven by covalent coupling reactions. This method permits facile covalent crosslinking of the polymer/nanoparticle interlayers in common organic solvents, which provides a general rou…
We extensively study the phase diagram of a diblock copolymer melt confined in a cylindrical nanopore using real-space self-consistent mean-field theory. We discover a rich variety of new two-dimensional structures that have no analogue in the unconfined system. These include nonhexagonally coordinated cylinder phases…
A recently proposed microscopic activated barrier hopping theory [K. S. Schweizer and E. J. Saltzman, J. Chem. Phys. 119, 1181 (2003)] of slow single-particle dynamics in glassy liquids, suspensions, and gels is derived using nonequilibrium statistical mechanics. Fundamental elements underlying the stochastic nonlinea…
[reaction: see text] Oxidation of alkynes to alpha-dicarbonyl derivatives through a convenient one-pot procedure via a Brønsted acid-promoted "hydration" and a DMSO-based oxidation sequence has been achieved in high yields. The scope and limitations of the reaction have also been investigated.