A Theory of Internal Friction Peak Due to Thermal Unpinning of Dislocations and Its Application to P_1 Peak in Copper

A theory of internal frictions due to thermal unpinning of dislocations was developed. The results of quantitative calculations are as follows. (1) An internal friction peak as a function of temperature is formed, of which the shape is different from that of the Debye type single relaxation. (2) The distortion of the peak shape increases linearly with the strain amplitude. (3) The peak height of the internal friction and the magnitude of the associated ΔM effect are related by the equation, Q^_=0.126Δ_M. (4) The mean pinning distance can be estimated from experimental results. The predictions of the theory were compared with the experimental characteristics of the P_1 peak in deformed copper, and a satisfactory agreement was found especially as to the distortion of the peak with the strain amplitude. The estimated pinning distance was found to decrease from 200b to 20b as the deformation increases, where b is the magnitude of Burgers vector, and was found to remain constant or rather slightly increase with the decay (or annealing) of the P_1 peak

A General Treatment of the Distribution of Vacancies to Solute Atoms in a Ternary Solid Solution and its Application to Low Temperature Aging in Al-Cu-Sn Alloys(Metallurgy)

A general treatment to calculate the concentration of vacancy-solute atom pairs in a ternary dilute solid solution is presented. This treatment is applicable to a wide range of vacancy concentration relative to the concentration of one kind of solute atoms. The treatment is applied to explain the effect of tin addition on the rates of low temperature aging in Al-Cu alloys. The difference in the activation energy for aging between Al-Cu alloys and an Al-Cu-Sn alloy is analyzed to find the binding energy of a vacancy-tin atom pair to be about 0.3 eV larger than that of a vacancy-copper atom pair. The experimental result that the retardation of aging due to tin addition is appreciable only for tin concentrations larger than the vacancy concentration is also explained satisfactorily

Titanium dioxide engineered for near-dispersionless high terahertz permittivity and ultra-low-loss

Realising engineering ceramics to serve as substrate materials in high-performance terahertz(THz) that are low-cost, have low dielectric loss and near-dispersionless broadband, high permittivity, is exceedingly demanding. Such substrates are deployed in, for example, integrated circuits for synthesizing and converting nonplanar and 3D structures into planar forms. The Rutile form of titanium dioxide (TiO2) has been widely accepted as commercially economical candidate substrate that meets demands for both low-loss and high permittivities at sub-THz bands. However, the relationship between its mechanisms of dielectric response to the microstructure have never been systematically investigated in order to engineer ultra-low dielectric-loss and high value, dispersionless permittivities. Here we show TiO2 THz dielectrics with high permittivity (ca. 102.30) and ultra-low loss (ca. 0.0042). These were prepared by insight gleaned from a broad use of materials characterisation methods to successfully engineer porosities, second phase, crystallography shear-planes and oxygen vacancies during sintering. The dielectric loss achieved here is not only with negligible dispersion over 0.2-0.8 THz, but also has the lowest value measured for known high-permittivity dielectrics. We expect the insight afforded by this study will underpin the development of subwavelength-scale, planar integrated circuits, compact high Q-resonators and broadband, slow-light devices in the THz band