Materials Literature
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Crystal structure / Phase transition / Tricalcium silicate Abstract. Crystals of tricalcium silicate having a monoclinic superstructure transformed into a rhombohedral structure when they were heated at 1200 °C with gas flame: a=7.135(6) A, c=25.586(15) A, space group R3m, and contents of 9 x Ca2,9sSio,9sAlo,o40s.The…
For valves of the same diameter, type material of Stephanodiscus rotula, observed with light and scanning electron microscopy, has more total spines, more central strutted processes, and narrower mantles than does S. niagarae. However, these characters covary with diameter and with one another within each species. Thu…
The delayed hydrogen cracking behavior of cold-worked Zr-2.5Nb at temperatures above about 423 K depends upon the direction of approach to test temperature. Cooling to the test temperatures results in an increase in crack growth rate, da/dt, with increase in temperature, given by the following Arrhenius relationship d…
Time domain spectroscopy (TDS) is introduced for the first time to study the complex permittivity of liquid crystals. Measurements have been carried out for octylcyanobiphenyl (8CB) and the results are compared with literature data obtained by conventional steady-state methods in the frequency domain. It is also shown…
The mechanism of calcium sulfate dihydrate scale formation on reverse-osmosis membranes was studied by the introduction of a theory of crystallization. According to this theory, the values of the growth rate constant and the waiting period before nucleation obtained in long-term runs were reasonable in comparison with…
Theoretical and experimental work on the atomic structure of grain boundaries in metals and ionic crystals is reviewed critically. The dislocation and O-lattice models are described and their usefulness is assessed with reference to a worked example. The models derived from computer simulations of the atomic structure…
The recently discovered incommensurate phase of quartz close to the α-β transition has been investigated using Brillouin scattering. The frequency and the damping of the longitudinal (LA) and transverse (TA) acoustic modes propagating along the X, Y and Z directions have been measured as a function of the temperature…
We extend the wedge technique of Rivière et al. to measure the pretilt angle Φ and the (weak) anchoring energy of a nematic liquid crystal oriented on a suitably treated glass surface. The liquid crystal is placed in a wedge shaped space formed by the plate to be studied and a « standard » plate giving a strong homeot…
The potential impact of oxygen from roots on the source of inorganic nitrogen for Ruppia maritima L. (Potarnogetonales) was investigated in laboratory experiments. Roots released oxygen at a n average rate of 2 to 3 ~g 0, (mg dry wt)-' h-'. A distinctive oxygenated zone with a radius of 0.75 to 1.25mm developed in the…
The crystal structures of two manganoan 1M-phlogopites and kinoshitalite-1M (Ba, Mn brittle mica) have been re-examined to determine if cation ordering patterns in subgroup symmetries exist. In all cases, the X-ray single crystal data are better explained by the ideal symmetry of C2⁄m, which requires only one tetrahed…
Glass formation in the system PbO–PbF2 has been investigated. The structure of these glasses has been studied using X-ray diffraction. Densities, heat capacities, glass-transition and crystallization temperatures and Vicker's microhardnesses have been measured. D.c. conductivities of these glasses have also been measu…
Contrarily to previous expectations, the flat geometry is not the configuration of lowest free energy for the bilayers of SDS in the lamellar phase of SDS/water. Indeed, neutron scattering reveals an unusual pattern of diffuse scattering at small angles, in addition to the regular diffraction spots of a layered mesoph…
Nous avons étudié la structure des deux mésophases d'une molécule discoïde chirale par diffraction des rayons X et par observation optique. La comparaison des deux techniques nous a permis de déterminer quelques-uns des paramètres de la structure. La transition entre les deux mésophases semble être du type ferroélectr…
The oxidation reactions of hindered phenols by molecular oxygen catalysed by monomeric and polymeric cobalt–Schiff base complexes, cobalt and manganese porphyrins, and (pyridine)cobaloxime are described; the rate and selectivity of these reactions are very dependent on the catalyst and on the solvent.A new product has…
Activation and reaction volumes are reported for the interconversion of the 1A and 5T isomers of FeII complexes in several solvents; the reaction volume ΔV° and the activation volume ΔV15‡ are solvent-dependent but ΔV51‡ for the 5T →1A crossover is markedly negative and virtually solvent-dependent and a transition sta…
Abstract Small‐angle neutron scattering, SANS, stands forth as one of the most important of the new tools for evaluating polymer chain conformation and morphology. This paper reviews the SANS literature through 1982, with a few early 1983 references added. The theory of SANS is outlined and compared to light scatterin…
Preoxidised (OX) or prereduced (RED) TiO2(anatase) powder was exposed to N18O at 295 K in the dark. Three phenomena resulted from subsequent ultraviolet illumination: photoadsorption, photoexchange (with a much higher rate than with 18O2) and photodecomposition forming N2O and, to a lesser extent, N2. The initial rate…
We have carried out an extensive high resolution x-ray scattering study of the nematic-smectic A (N-S A) and reentrant nematic-smectic A (RN-SA) phase transition behaviour in mixtures of octyloxycyanobiphenyl (8OCB and hexyloxycyanobiphenyl (60CB). The smectic A phase boundary is found to be parabolic in the temperatu…
A method for determining the tryptophan content of feed and feedstuffs was established. This method involved three steps: alkaline hydrolysis, pretreatment of the hydrolysate for chromatography, and measurement of tryptophan by ion exchange liquid chromatography. With this method, the recovery of tryptophan in egg-whi…
Subsolidus phase equilibria in the system La 2 O 3 ‐P 2 O 5 were established. The system contains six intermediate compounds having molar La 2 O 3 :P 2 O 5 ratios of 3:1,7:3,1:1,1:2,1:3, and 1:5. It was found that the 3:1 compound has a phase transformation at 935°C. The 1:2 compound decomposes to a mixture of 1:1 and…