Materials Literature
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The effect of stress relaxation by creep on the thermal stress fracture of brittle ceramics at high temperature under conditions of quasi‐static heat flow is discussed. It is shown that, to a good approximation, thermal stress relaxation rates can be calculated on the basis of creep rates which correspond to the minim…
Summary A number of new alkaline-earth-rare-earth silicate and germanate compounds with the apatite-type structure have been synthesized including a new calcium lanthanum silicate, Ca 4 La 6 (SiO 4 ) 6 (OH) 2 , which has a 9·63 Å, c 7·12, and c/a 0·740. This has a random distribution of Ca 2+ and La 3+ over the (4f) a…
Summary The immediate Q/I relation of K in a soil relates the amount of labile K present to its chemical potential, measured relative to the chemical potential of (Ca+Mg) in the same soil. The present work shows that the form of the Q/I relation is almost unchanged either by large additions of K, up to 3750 kg K 2 O/h…
A two-valence-band model and the theory of transport in semiconductors with non-parabolic bands have been used to explain the carrier concentration dependence of the room-temperature thermoelectric power and below-room-temperature Hall mobility of undoped and Na-doped PbTe. It was assumed that the scattering is by lat…
Considerable x-ray diffraction analysis of omega phase in titanium alloys has been reported; however, little direct observation of its occurrence via electron microscopy has been published. In this work we have demonstrated by means of transmission electron microscopy that the omega phase in titanium-35% niobium preci…
This paper presents the results of measurements of the velocities of 〈12̄10〉 (0001) edge dislocations in zinc as a function of applied shear stress. All tests were conducted at room temperature on 99.999% pure zinc monocrystals. Dislocations were revealed by means of the Berg-Barrett x-ray technique. Stress pulses of…
The spreading behavior and equilibrium contact angle, θ, of organic liquids on soda‐lime glass surfaces were observed at relative humidities (rh) varying from 1 to 95%. Increasing rh increased θ for many nonhydrophilic liquids on glass; no comparable effects occurred with nonadsorptive solid surfaces. The decrease in…
Covers advancements in spacecraft and tactical and strategic missile systems, including subsystem design and application, mission design and analysis, materials and structures, developments in space sciences, space processing and manufacturing, space operations, and applications of space technologies to other fields.
Grain size and other structural features are known to influence the mechanical properties of mild steels, and it is shown that their effects in stress-corrosion crack propagation are essentially the same as their effects upon plastic-flow characteristics. Preferential corrosion in the grain-boundary regions of mild st…
ADVERTISEMENT RETURN TO ISSUEPREVArticleNEXTThe Structure-Activity Relationship in Barbiturates and Its Similarity to That in Other NarcoticsCorwin. Hansch and Susan M. AndersonCite this: J. Med. Chem. 1967, 10, 5, 745–753Publication Date (Print):September 1, 1967Publication History Published online1 May 2002Published…
The materials scientist is concerned with relating microstructure and properties. In crystals, most of the important imperfections can only be observed by transmission through thin foils (T.E.M.), first accomplished by Heidenreich in 1949. The truly amazing growth of T.E.M. is due mainly to three factors: a) improveme…
The room-temperature oxidation behaviour of reactive metal and ceramic powders is reviewed and it is shown that many materials under normal circumstances oxidize to give a limiting film thickness of ∼50Å. Since the thickness of oxide films has an important bearing on sintering characteristics the control of oxidation…
Abstract Aromatic polyhydantoins of high molecular weight have been prepared by a polyaddition—cyclocondensation reaction of diethyl m ‐phenylenebisiminoacetate with aromatic diisocyanates in m ‐cresol. The polyhydantoin obtained from methylenebis(4‐phenyl isocyanate) showed good thermal stability up to 400°C. in air.…
The high-temperature irradiation embrittlement of steels and nickel alloys is probably due to helium precipitation in grain boundaries. It would be desirable to retain the helium as fine bubbles evenly distributed within the grains. A fine dispersion in the metal matrix may act as nucleation site for helium bubbles an…
The X‐ray thermal expansion of TaC x was measured over the composition range from TaC 0.789 to TaC 0.997 at temperatures to 1000°C. The average thermal expansion coefficient, α, increased with increasing formula weight; α from 25° to 1000°C is 6.04, 6.37, and 6.96 × 10 −6 /°C for TaC 0.789 , TaC 0.912 , and TaC 0.997…
It is shown that a tracer plate will diffuse into a specimen which is being plastically deformed by a process called mechanical diffusion. The magnitude of the penetration via mechanical diffusion is about equal to the offset of the individual glide packets; this offset, in turn, is caused by the nonhomogeneous charac…
Summary Several studies (e.g. Bolt et al ., 1963; Beckett, 1964 a ) of the exchange equilibria between K and Ca on soil colloids or pure clay minerals have drawn attention to the presence of sites with different affinities for K. There is so far no evidence to indicate the location of sites with the highest affinity,…
Abstract The esterification of metal soaps, in the combination of zinc and calcium soaps, on poly(vinyl chloride) (PVC) has been carried out both in liquid and solid phase to determine why the reactivity of zinc soap decreases on addition of calcium soap, improving the long‐run heat stability of PVC and causing the we…
Abstract A theory is presented for a general treatment of the molecular size distribution, the gel point, and the post-gelation phenomena with respect to polymerization with formations of various kinds of interunit junctions, assuming (1) that all functional groups are equally reactive, and (2) that no kind of intramo…
Abstract Results of following the quantities of free Ca(OH) 2 and of tricalcium silicate (C 3 S) during the hydration of C 3 S, and also the influence of the presence of free CaO on this reaction are in accordance with the hypothesis of Stein & Stevels with regard to the hydration of C 3 S. at the first contact be…