https://hdl.handle.net/11256/46 2021-04-29T02:52:38Z 2021-04-29T02:52:38Z Simmons, RO Balluffi, RW https://hdl.handle.net/11256/39 2014-07-15T17:43:19Z 2014-07-02T00:00:00Z

Measurement of Equilibrium Concentrations of Vacancies in Copper Simmons, RO; Balluffi, RW The net added fraction of thermally-generated atomic sites, ΔNN, has been measured, during equilibrium heating to near the melting point, in a coarse-grained copper bar of 99.999% purity. The linear thermal expansion, ΔLL, and the x-ray lattice expansion, Δaa, as measured simultaneously, agree within the measurement error of ±1×10−5 throughout the temperature interval between 56 and 850°C. At 1000 and at 1075°C, ΔNN=3(ΔLL−Δaa) is (0.9±0.5)×10−4 and (1.9±0.5)×10−4, respectively. Using expected limits for the binding energies of vacancy clusters, it is concluded that ΔNN consists almost entirely of monovacancies. An assumed value of (1.5±0.5)k for the formation entropy, combined with these concentrations, yields a monovacancy formation energy of (1.17±0.11) eV. The ratio of this formation energy to the activation energy for self-diffusion is therefore about 0.57, near the ratios found for the other noble metals. The results imply a monovacancy migration energy of (0.88±0.13) eV. The present results are compared with the results of a wide variety of other investigations of defects in copper which include: (1) theoretical calculations, (2) quenching and annealing, (3) thermal diffusion, (4) annealing after irradiation, and (5) annealing after cold work. In certain cases apparent disagreement is found. However, it is concluded that in no case is there a sufficiently firm body of experimental data available either to confirm or to contradict the present monovacancy data. The need for further definitive experiments in these areas is emphasized.

2014-07-02T00:00:00Z Gehlen, P. C. Cohen, J. B. https://hdl.handle.net/11256/35 2014-07-15T17:44:47Z 2003-11-17T00:00:00Z

Nature of Long-Range Order in Cu3+xAu1-x Gehlen, P. C.; Cohen, J. B. The diffuse scattering and intensities of Bragg peaks from single crystals of Cu77Au23 and Cu78Au22 have been studied for various degrees of long‐range order. The results indicate that the excess Cu atoms, replacing Au in Cu3Au1 distribute themselves at random for the maximum degree of long‐range order. The maximum values of the order parameter indicate that the Cu sublattice is completely filled. For order less than the maximum, the results can be explained in terms of a large number of small ordered regions antiphase to the matrix; these regions are primarily two dimensional and vary in composition from point to point in the alloy. These are more Cu rich than similar regions in Cu3Au. Evidence is presented that the difference in atomic sizes of the species varies with degree of order. It is also shown that the scattering due to differences in atomic size and thermal vibrations and that due to local order can be separated completely at one temperature by symmetry operations, as suggested by Borie and Sparks.

2003-11-17T00:00:00Z Straumanis, M. E. Yu, L. S. https://hdl.handle.net/11256/34 2014-07-15T17:46:18Z 1969-04-08T00:00:00Z

Lattice Parameters, Densities, Expansion Coefficients and Perfection of Structure of Cu and Cu-In alpha Phase Straumanis, M. E.; Yu, L. S. Spectroscopically pure Cu has a lattice parameter a25 = 3.61491 Å (corrected for refraction), and a thermal expansion coefficient [alpha] = 14.87 × 10-6°C-1 between 15 and 55°C. The measured density d25 is 8.9314 ± 0.0002 g.cm-3 in agreement with the calculated value dx = 8.9316. In the [alpha] solid solution region additions of In increase the lattice parameter of Cu according to ax = 3.6149 + 0.0091x up to x = 10.4 (x = atomic % In, balance Cu). The thermal expansion coefficients between 15 and 65°C of the homogeneous alloys increase from 14.87 (pure Cu) to 17.2 × 10-6°C-1 at the solid solubility limit (10.4 atomic % In, quenched from 650°C). With the increase of In content the experimental densities become increasingly lower than the calculated ones because of void formation. Upon cold rolling the voids close and the differences disappear. The [alpha] phase represents a substitutional solid solution without structural defects. Alloys quenched from the liquid state do not show any microporosity; the voids appear after homogenization at 800°C. Micropore formation is explained by differential shrinkage of the various crystalline fractions formed during solidification, giving rise to internal stresses in the solid alloy. Relief of stresses results in vacancies or micropores, which coalesce into voids upon heat treatment.

1969-04-08T00:00:00Z Eppelsheimer, D.S. Penman, R. R. https://hdl.handle.net/11256/33 2014-07-15T17:47:28Z 1950-01-07T00:00:00Z

Thermal Dilation of Copper Eppelsheimer, D.S.; Penman, R. R. The prediction that certain cubic metals may not be precisely cubic throughout a range of temperature below their melting points led to the present investigation. Pure copper was chosen as the cubic metal to examine for anisotropy in its thermal dilation, and the (024) and the (331) planes were chosen in the lattice. Temperatures for examination ranged between 18°–770°C, using a 19-cm high-temperature powder camera by Unicam of Cambridge, England. Plotting the lattice constant vs. temperature, the thermal dilation of pure copper was found to be isotropic throughout the temperature range investigated.

1950-01-07T00:00:00Z