Materials Literature
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Solid solutions along the magnesite-siderite join have been synthesized from mechanical mixtures of iron oxalate and basic magnesium carbonate using hydrothermal synthesis techniques at 500°C and about 2 kilobars. The double capsule method was used to provide the atmosphere necessary to prevent decomposition and oxida…
All articles of this category Improved procedures are described for the synthesis of meso -tetrakis(2,6-dichlorophenyl)porphyrin and for subsequent perhalogenation of the porphyrin ring. halogenated porphyrins - metalloporphyrins halogenation - oxidation catalysts
The frequencies of the Si-Si, Si-Ge, and Ge-Ge Raman modes in ${\mathrm{Si}}_{1\mathrm{\ensuremath{-}}\mathit{x}\mathrm{\ensuremath{-}}\mathit{y}}$${\mathrm{Ge}}_{\mathit{x}}$${\mathrm{C}}_{\mathit{y}}$ alloys with y\ensuremath{\leqslant}0.03 have been measured. All frequencies are found to increase as a function of t…
The exciton binding energy ɛb for a conducting polymer can only be defined unambiguously in the long chain limit. In that limit it can be taken as the difference between the bandgap or the ‘single particle bandgap’ — the former if the exciton dissociates into a free electron and hole, the latter if it dissociates into…
We analyzed the magnetic, transport, and magnetotransport properties of ${\mathrm{La}}_{0.67}$${\mathrm{Ca}}_{0.33}$${\mathrm{Mn}}_{1\mathrm{\ensuremath{-}}\mathit{x}}$${\mathrm{Al}}_{\mathit{x}}$${\mathrm{O}}_{\mathit{y}}$ as a function of aluminum concentration, temperature, and magnetic field and we found that when…
In situ Fourier transform infrared spectroscopic studies have been carried out on the nature of a metal complex‐immobilized polyaniline (PAn)/Prussian blue‐modified electrode and on the application of this electrode to the electroreduction of in an aqueous solution. On cathodic polarization, the ring structures of PAn…
The physical and electrical properties of xPb(Sc1/2Nb1/2)O3-yPb(Mg1/3Nb2/3)O3-zPbTiO3(PSMNT 100x/100y/100z) ternary ceramic materials near the morphotropic phase boundary (MPB) were investigated. The MPB follows on almost linear region between the PSMNT 58/00/42 and PSMNT 00/68/32 MPB compositions of the binary system…
The Brillouin light scattering technique has been used to study the elastic properties of a number of silicon dioxide films deposited by plasma-enhanced chemical vapor deposition on Si substrates. In addition to stoichiometric undoped glass films produced from either silane or tetraethylorthosilicate, we have also stu…
Paramagnetic centers in Nb-doped BaTiO3 ceramics are measured at 77–500 K by electron paramagnetic resonance (EPR) for investigating the role of the centers on the well-known positive temperature coefficient of resistivity (PTCR) effect (PTCR at the Curie temperature). EPR detects four signals; an anisotropically broa…
The effect of fluorine addition on silicon oxide film properties as a function of SiF4/O2 gas flow ratio was investigated. The films were deposited by using electron cyclotron resonance plasma chemical vapor deposition with SiF4 and O2 as source gases diluted in Ar. Characterization of films was carried out in terms o…
The electrical degradation of (Ba, Sr)TiO 3 [BST] thin films as a function of the film thickness was investigated. BST thin films with various thickness were deposited on Pt/Ti/SiO 2 /Si substrates by in-situ RF magnetron sputtering. It was found that the electrical properties degraded markedly as the thickness of the…
The structure observed in concentrated polymeric micelles results from interactions between coronal chains that develop as micelles are brought to approach distances where the chains either compress or interdigitate. One powerful model for polymeric micelles comprises spherical particles with chains tethered to their…
Metal-insulator transition was observed in icosahedral quasicrystals ${\mathrm{Al}}_{70.5}$${\mathrm{Pd}}_{21}$${\mathrm{Re}}_{8.5\mathrm{\ensuremath{-}}\mathit{x}}$${\mathrm{Mn}}_{\mathit{x}}$ as x changed from 5 to 0. It was found that conductivity data of the insulating samples (x\ensuremath{\leqslant}3.5) could be…
Ultraviolet light induced changes in polyimide liquid-crystal alignment films were investigated. Infrared, UV-visible, x-ray photoelectron spectroscopy, and electron-spin-resonance measure- ments indicated that bond breaking and subsequent oxidation reactions occur in polyimide films (SE7210, OCG284, DuPont 2555 and 2…
Abstract A variety of dendrimers up to generation 7 possessing terminal P(S)Cl 2 , (3‐[G 1 ]‐3‐[G 7 ]) or P(O)Cl 2 , (7‐[G 1 ]‐7‐[G 3 ], 7‐[G 3 , 7‐[G 7 ) have been tri‐ and tetrafunctionalized. Selective monosubstitution of P(X)Cl 2 (X = S, 0) termini with allylamine or propargylamine gave the trifunctionalized dendr…
Aromatic, fully conjugated polymers are a class of polymers attracting significant interest in academics as well as industry. In particular, poly-(p-phenylene) (PPP) and poly(p-phenyienevinylene) (PPV) are important materials due to their thermal stability and electrical conductivity after doping. Very recently their…
Abstract The reaction of ferric chloride and β‐diketones (HL) in alkaline methanol solution represents a good synthetic route to hexairon(III) clusters [MFe 6 ‐(OCH 3 ) 12 (L) 6 ] + (M = Na, Li), which exhibit an unusual sixfold molecular symmetry. Single‐crystal X‐ray diffraction showed that the six octahedrally coor…
New experimental techniques have been applied to the study of single-photon double ionization of atoms and molecules. A coincidence technique is described in which the spectra of nearly zero energy photoelectrons are recorded in two identical photoelectron energy analysers. The results are discussed in terms of the av…
Abstract Linear polyurethanes (PUR‐D k ) were prepared by reacting 4,4′‐methylenediphenyl diisocyanate (MDI) with low‐molecular‐weight diols HO(CH 2 ) k OH ( k = 2, 3, 4, and 6) and fractionated by precipitation or extraction with mixtures of N , N ‐dimethylformamide (DMF) and dibutyl ether (DBE). The fractions were…
Binary magnesium alloys containing chromium, manganese, or titanium were made using a physical vapour deposition technique. The corrosion resistance of the alloys was assessed in aqueous chloride solutions using total immersion tests in quiescent 600 mmol L−1 NaCI solutions. Alloying with manganese or titanium was fou…