Materials Literature
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The simple model for atomic displacements by electrons of Seitz and Koehler is used to calculate the total number of displaced atoms in germanium and silicon due to electrons and gamma rays of energies up to 7 Mev. The calculations are compared to reported experiments in the literature. Electron damage at energies bel…
The Lindemann melting rule is used to eliminate the elastic constant from the thermal conductivity formula proposed by Lawson. The thermal conductivity is thus obtained as a function of density, atomic weight, and melting temperature. The introduction of a dependence on bond character allows a major fraction of the av…
Trititanium pentoxide (Tia05) is dimorphic--a rapid, reversible phase transformation occurring at about 120 C. The high-temperature modification is of the anosovite type (slightly deformed pseudobrookite structure). It can be stabilized at room temperature by small contents of iron.
Abstract Films of amorphous polyethylene terephthala were drawn and heated to various extents. Intensity change of the infrared spectral bands resulting from these treatments were followed. There are more than seven bands which change their intensities by drawing, and sixteen bands affected by heat treatment. Exactly…
Oxygen ion mobility in the cubic fluorite‐structure phase having the composition Zr 0.85 Ca 0.15 O 1.85 has been directly determined by exchange measurements employing the stable isotope O 18 and mass spectrometer analysis. Measurements of electrical conductivity have been carried out as a function of both temperature…
The formula given by Moli\`ere for the scattering cross section of a charged particle by an atom, on which has been based the formula for the "screening angle" ${\ensuremath{\chi}}_{\ensuremath{\alpha}}$ in his theory of multiple scattering, has been examined and found to contain an inconsistent approximation in all o…
Thin sheets, removed by cleavage from the surface layers of mica exposed to fission fragments from uranium, have been examined in transmission in the electron microscope. Fission fragment tracks which are less than 300 A. in diameter and greater than four microns in length have been seen, superimposed upon a general b…
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An empirical equation form, approximating the apparent dependence of the strength of brittle polycrystalline specimens on the combined effect of porosity and grain size, has been developed from concepts and data in the literature. The form is shown to be applicable to data for thoria and chromium carbide specimens.
The total photoelectric cross sections of copper, molybdenum, silver, tantalum, and gold have been measured at 662 kev. A highly collimated beam of gammas from a Cs-137 source impinged upon a thin disk of a target material. Photoelectrons from a target were detected by a plastic scintillator subtending very nearly $4\…
Ferroelectric ${(\mathrm{glycine})}_{3}$\ifmmode\cdot\else\textperiodcentered\fi{}${\mathrm{H}}_{2}$S${\mathrm{O}}_{4}$ crystallizes at room temperature in the monoclinic system with $a={9.41}_{7}$ A, $b={12.64}_{3}$ A, $c={5.73}_{5}$ A, $\ensuremath{\beta}=110\ifmmode^\circ\else\textdegree\fi{}{23}^{\ensuremath{'}}$;…
Montmorillonite, illite, chlorite, and kaolinite in the playas of southern California are traceable directly to the source areas surrounding the basins. No evidence found in this investigation suggests that these clay minerals are unstable in the sodic or calcic saline lake environment, but this conclusion may not be…
Proto-enstatite, at room temperature, is orthorhombie with 8 units of MgSiO3 in a cell of dimensions a ----9.25, b ----8.74, c = 5.32 A, pseudo space group Pbcn. The atomic coordinates of the pseudo space group were determined from X-ray powder data. The SiO3 chain is fully extended. One of the Mg atoms has an irregul…
A new modification of boron, resulting from the pyrolytic decomposition of BI z on a heated surface (800 C. to 1100 C.), has been found to have a simple rhombohedral structure, with a 0 = 5.057 /~ and c~ = 58.06 , space group R3m, Z ----12. The atomic parameters have been obtained from a single crystal using the prece…
The structure was determined and refined by use of Pa t te rson and Fourier projections on the three faces of the uni t cell. The seven shortest Zr-O separations in the coordination polyhedron around each zirconium range from 2.04 to 2.26 A; since the next nearest Zr-O separat ion is 3.77 ~ , the coordination number o…