Materials Literature
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This paper describes the results of an extensive microstructural study designed to explore the basic processes controlling the nucleation of graphite nodules in chill cast iron. The experimental melts were nodularized with magnesium ferrosilicon and then inoculated, either with foundry grade ferrosilicon or Superseed…
Abstract As the basic research for the study of complex reactions in polymers, the complex formation of poly(vinyl alcohol) (PVA) with copper and other metals was tried. Spectroscopy, pH titration, and elementary analysis were employed in the reaction of PVA and Cu(II) ions in aqueous solution. The complexing protonat…
The X-band e.p.r. spectra at 4.2 K of cerium(III), dysprosium(III), and ytterbium(III) doped into cubic Cs2NaYCl6 are reported. The magnitude of the g-factor and the isotropic nature of both g and the line width indicate that the ions occupy sites of exact octahedral symmetry. Analysis of the spin Hamiltonian paramete…
The 13C n.m.r. spectra of the methyl esters of the four coproporphyrin type-isomers and deuteroporphyrin-IX, and of octaethylporphyrin, and the zinc(II), thallium(III), and some diprotonated derivatives are reported and assigned. An immediate differentiation between the coproporphyrin type-isomers is provided by the s…
At rest between two metallized glass plates a nematic liquid shows a screw-like deformation pattern if one turns the plates by an angle ωm around an axis perpendicular to the plates. If a voltage U is applied, the molecules are tilted with respect to the electric field when U exceeds a threshold voltage. With increasi…
Magnetic susceptibility measurements and Mössbauer spectra show that NdCoO3 and GdCoO3 contain predominantly low-spin CoIII ions at low temperatures which transform partially to high-spin Co3+ until a certain temperature. Beyond this temperature, there is a transfer of eg electrons from Co3+ to CoIII giving rise to di…
Tetramethyltetraselenofulvalene reacts with tetracyanoquinodimethane to form a highly conducting organic solid.
A numerical technique has been used to predict eutectic compositions of some liquid crystal mixtures; good agreement was found with experimental results on mixtures of 4′-n-alkyl- and 4′-n-alkoxy-4-cyanobiphenyls some of which are nematic over the range 0–60 °C.
Natural diamond was implanted with 40 keV argon ions at room temperature and with fluences 6.1013 − 2.4.1015 cm−2. The crystal structure of implanted layers has been studied and the results are presented.
Après un bref rappel des travaux de Grandjean et de Cano, il est démontré que, lorsqu'un clivage dans un cristal, ou l'espace compris entre deux verres frottés est rempli par un liquide cholestérique, les cloisons apparaissant dans le milieu sont en fait des fils, ainsi que l'avait déjà noté Friedel (1922). Les fils s…
Certain peculiarities of photoconductivity in ferroelectrics are discussed. On the example of the ferroelectric SbSI, the nature of anomalies in electrical conductivity and photoconductivity in the Curie temperature region is discussed. For the first time the photoconductivity in certain ferroelectric niobates and the…
Abstract The heat capacity of SnCl2·2H2O and SnCl2·2D2O crystals, substances with layer structure, was measured from 13 to 300 K. Anomalies due to ordering of the hydrogen (deuterium) position were observed at TC(H2O)=217.94 K and at Tc(D2O)=234.47±0.05 K. The total entropy change of the transition was estimated to be…
A discussion is given of the dielectric properties of some nematic phenyl benzoates with the structure For n = 2 the dielectric anisotropy Δ∊=∊‖– ∊⊥ is found to be positive. For n = 1, however, the sign depends on the para substituents In particular, replacement of an alkyl group by an alkoxy group shifts Δ∊ towards n…
The anomalous ultrasonic attenuation and velocity variation caused by the critical fluctuation of spins near the Curie and Néel temperatures are theoretically investigated and found to be strongly affected by an application of magnetic field. In the random phase approximation, the attenuation coefficient is expressed…
Homolysis of the C–Mn bond of [RMn(CO)5] or [RCOMn(CO)5] under u.v. irradiation has been studied using nitrosodurene as a spin-trap for both the radicals formed; irradiation of various metal–metal bonded compounds (LM–ML, M = Mn, Re, Fe, Mo, or Co) gives rise to metal-centred radicals which can similarly be trapped.
Rates of oxidative vaporization of on preoxidized resistively heated chromium were determined in flowing oxygen at a pressure of 0.115 Torr for temperatures from 1000° to 1300°C. Reaction controlled rates were obtained from experimental rates by a gold calibration technique, and these rates were shown to agree with th…
The influence of the addition of mainly 1st row of transition elements on the resistivity anomaly of BaTiO3 semiconducting ceramics has been examined. The results showed that Mn ion is the most effective in increasing the PTC anomaly by up to a factor of 109. The high temperature chemical behaviour of the ceramics was…
A survey is given of the results of five years electron fractography as conducted at the National Aerospace Laboratory N.L.R. and of the contribution of this work to the comprehension of fatigue cracking, ductile fracture, cleavage and stress corrosion.
W A Wooster Oxford: University Press 1973 pp x + 344 price £7 'The reader who died of boredom' is a built in hazard for the authors of books on group theory, and Dr Wooster sets his own critical standards when he confesses that he has difficulty in keeping awake while reading such books. As a fellow sufferer, I am hap…
ADVERTISEMENT RETURN TO ISSUEPREVArticleNEXTStereochemistry of low-spin cobalt porphyrins. III. Crystal structure and molecular stereochemistry of bis(piperidine)-.alpha.,.beta.,.gamma.,.delta.-tetraphenylporphinatocobalt(II)W. Robert ScheidtCite this: J. Am. Chem. Soc. 1974, 96, 1, 84–89Publication Date (Print):Janua…