Materials Literature
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High resolution 125Te and 123Te F.T. n.m.r. spectroscopy have been used to identify all members of the series [TenSe4–n]2+(n= 1–4) in the Te–Se–oleum system.
The temperature dependence of the permittivity of BTF 2 ceramic has been measured. Three singularities have been observed, of which two at 898°C and 752°C correspond to displacive phase transitions leading to the sequence paraelectricm ↔ ferroelectric ↔ ferroelectric. The third feature, around 400°C, is tentatively as…
Fission cross-section ratio measurements were made in the 2- to 3-MeV region using 235U samples with 234U and 236U samples containing ∼10% 235U. Atom ratios were obtained from measured thermal fission ratios and the isotopic analysis and also by alpha counting. Shape measurements were made from threshold to 10 MeV usi…
Temperature dependences of the optical rotatory power ρs 3 in the ferroelectric phase, the field-induced optical rotatory power ρ3(E 3) in the paraelectric phase and of the initial permittivity ε33 have been measured. These results show that dρ3/dE 3 fulfils the Curie-Weiss law being proportional to the value of ε33.…
Previous studies on eutectoid steel have demonstrated that strength and toughness are essentially independently varying parameters, with the former primarily controlled by the pearlite interlamellar spacing and the latter primarily controlled by the prior austenite grain size. The work has now been extended to study t…
The enzymatic defects in a number of Bacillus subtilis mutants of the alpha-ketoglutarate dehydrogenase complex lacking activity have been investigated. Mutants in the citK locus, as well as a series of deletions of unknown length covering the citK locus, are deficient in E1 of the complex, alpha-ketoglutarate dehydro…
The kinetics of the reaction OH + NO(+ M)→ HNO2(+ M) have been studied, using flash photolysis to generate OH radicals and time-resolved resonance absorptions to observe the rate of their removal. Effective second-order rate constants, k1=(– d ln [OH]/dt)/[NO], have been determined at four temperatures, T= 233, 296, 4…
Abstract A series of methyl methacrylate (MMA)–methacrylic acid (MAA) copolymers containing up to 50% methacrylic acid and the respective homopolymers were reproducibly pyrolyzed at 900°C and the fragments identified by gas chromatography (GC) or GC–mass spectroscopy. It was shown that PMMA and the MMA portions of blo…
Abstract Coalescence in vertical close packed dispersions . Models are presented for the description of growing, decomposing, and steady‐state dispersions. They contain the velocity of the dispersed phase V 0 , the initial drop diameter Φ 0 , the hold‐up ε , and the coalescence times between the drops τ and at the fre…
Transmission electron microscopy (TEM) has been widely used to study point defect clusters in metals following quenching and irradiation. As a result of this work considerable progress has been made in our understanding of the nucleation, morphology, and growth of clusters and this paper reviews the current state of t…
Photochromic (Z)-1-methylpropylidene(diphenylmethylene)succinic anhydride undergoes photochemical conrotatory ring closure and thermal disrotatory ring closure reactions to form red 1,8a-dihydronaphthalene intermediates (1,8a-DHNs) which undergo a facile thermal 1,5-H shift to yield colourless 1,2-DHNs. Yellow (E)-3,5…
Abstract Electrically polarized and unpolarized films of polyacrylonitrile (PAN) have been investigated by both infrared attenuated total reflection (ATR) and thermally stimulated discharge (TSD). ATR analysis of PAN films has been aimed at explaining the molecular origin of thermally stimulated currents, and conseque…
Dielectric measurements of the ceramic samples of Bi2MoO6 show that this crystal is ferroelectric with the Curie temperature Tc ≈ 570°C. According to the empirical relation between cation shift and ferroelectric Curie temperature the approximate magnitude of Mo6+ cations displacement equal to Δz = 0.21 Å.
Single crystals of Ca 3 (VO 4 ) 2 with diameters up to 25 mm and lengths of 60 mm have been grown by the Czochralski technique from a stoichiometric melt. Elastic, thermoelastic, piezoelectric, linear electrooptic, dielectric and pyroelectric properties have been measured. Ca 3 (VO 4 ) 2 exhibits much smaller elastic…
Treatment of the phaeofarnesins (4) isolated from the Chlorobium chlorophylls-660 (ex. Chloropseudomonas ethylicum) with sulphuric acid in methanol gives the methyl phaeophorbides (1) which can be dehydrated by refluxing in benzene in the presence of acid to afford the 2-vinyl derivatives (2); prolonged refluxing give…
Procedures are described for the quantitative determination of the asbestos and α-quartz contents of bulk samples by use of X-ray powder diffractometry. The method gives satisfactory results for several different types of asbestos and for mixtures of two or more different types. Problems with sample grinding and prefe…
Electron microscopy observations show that in the ordered alloy Ni 3V, perfect 1/ 2[112] dislocations are dissociated into three 1/ 6[112] partial dislocations bounding an intrinsic-extrinsic pure stacking fault pair (i.e. without any wrong first neighbour bonds); from this an evaluation of stacking fault energies can…
Polystyrene without additional compounds was treated in a laboratory oven at elevated temperatures (200 degrees, 350 degrees, 500 degrees C) under slight air flow (0.7 l/min). The thermal degradation products appearing in different phases (gases, vapors, aerosols) were collected and analyzed by methods of chromatograp…
A variety of configurations of coupled dislocations straddling a polygon wall were revealed by the etch hillock technique on the (001) surface of white tin. Observations indicated that: (1) Both coupled dislocations and wall dislocations move to the same [100] direction under an applied stress; (2) Their slip plane is…
The intensities of 90 normal and 93 satellite x-ray reflections of the modulated intermediate phase of NaNO2 were measured 0.2 K. above the Curie temperature. The least agreement between the observed and calculated structure factors has been obtained by assuming that the antiferroelectric phase of NaNO2 is both amplit…