Elastic Constant

In this study, an analysis of rubberized concrete was done according to composite material rules. The rubberized concrete analyzed was created using various proportions of normal C 16 concrete with bits of scrap automobile tires. Being composed of mortar, aggregate and rubber, the concrete was treated as a three-phase composite. In determining equations for elastic constants, it was observed that experimental results complied conclusively with equations used for composite material rules. An equation was solved to determine the elasticity moduli. Then it was observed that the validity of equation proposed.

The semiconductor ZnO has gained substantial interest in the research community in part because of its large exciton binding energy (60 meV) which could lead to lasing action based on exciton recombination even above room temperature. Even though research focusing on ZnO goes back many decades, the renewed interest is fueled by availability of high-quality substrates and reports of p-type conduction and ferromagnetic behavior when doped with transitions metals, both of which remain controversial. It is this renewed interest in ZnO which forms the basis of this review. As mentioned already, ZnO is not new to the semiconductor field, with studies of its lattice parameter dating back to 1935 by Bunn [Proc. Phys. Soc. London 47, 836 (1935)], studies of its vibrational properties with Raman scattering in 1966 by Damen et al. [Phys. Rev. 142, 570 (1966)], detailed optical studies in 1954 by Mollwo [Z. Angew. Phys. 6, 257 (1954)], and its growth by chemical-vapor transport in 1970 by Galli and Coker [Appl. Phys. Lett. 16, 439 (1970)]. In terms of devices, Au Schottky barriers in 1965 by Mead [Phys. Lett. 18, 218 (1965)], demonstration of light-emitting diodes (1967) by Drapak [Semiconductors 2, 624 (1968)], in which Cu2O was used as the p-type material, metal-insulator-semiconductor structures (1974) by Minami et al. [Jpn. J. Appl. Phys. 13, 1475 (1974)], ZnO/ZnSe n-p junctions (1975) by Tsurkan et al. [Semiconductors 6, 1183 (1975)], and Al/Au Ohmic contacts by Brillson [J. Vac. Sci. Technol. 15, 1378 (1978)] were attained. The main obstacle to the development of ZnO has been the lack of reproducible and low-resistivity p-type ZnO, as recently discussed by Look and Claflin [Phys. Status Solidi B 241, 624 (2004)]. While ZnO already has many industrial applications owing to its piezoelectric properties and band gap in the near ultraviolet, its applications to optoelectronic devices has not yet materialized due chiefly to the lack of p-type epitaxial layers. Very high quality what used to be called whiskers and platelets, the nomenclature for which gave way to nanostructures of late, have been prepared early on and used to deduce much of the principal properties of this material, particularly in terms of optical processes. The suggestion of attainment of p-type conductivity in the last few years has rekindled the long-time, albeit dormant, fervor of exploiting this material for optoelectronic applications. The attraction can simply be attributed to the large exciton binding energy of 60 meV of ZnO potentially paving the way for efficient room-temperature exciton-based emitters, and sharp transitions facilitating very low threshold semiconductor lasers. The field is also fueled by theoretical predictions and perhaps experimental confirmation of ferromagnetism at room temperature for potential spintronics applications. This review gives an in-depth discussion of the mechanical, chemical, electrical, and optical properties of ZnO in addition to the technological issues such as growth, defects, p-type doping, band-gap engineering, devices, and nanostructures.

Present paper describes the facilities of composite material properties identification technique using specimen vibration tests, genetic algorithms, finite elements analysis and specimen shape optimization. In identification process the elastic constants in a numerical model is updated so that the output from the numerical code fits the results from vibration testing. Main problem analysed in this paper is that Poisson's ratio is the worst determined elastic characteristic due to its low influence on specimen eigenfrequencies. It is shown that it is possible to increase its influence by choosing specific test specimen characteristics (side aspect ratio, orthotropy angle, etc.) via optimization routine. In this paper are presented test results of some experiments wherein glass‐epoxy and carbon‐epoxy material properties were identified. Santrauka Straipsnyje aprašomas kompozitiniu medžiagu tamprumo charakteristiku identifikavimo metodas naudojant bandiniu vibracinius bandymus, gen...

Using first-principles density functional calculations, the structural, electronic, elastic and optical properties of cubic spinel SiGe2N4 were studied by means of the full-relativistic version of the full-potential augmented plane wave plus local orbitals. We employed both the generalized-gradient approximation (GGA), which is based on exchange-correlation energy optimization to calculate the total energy, and the Engel–Vosko formalism, which optimizes the corresponding potential for band structure calculations.The calculated bulk properties, including lattice parameters, bulk modulus and their pressure derivatives, are in reasonable agreement with the available data. We have determined the full set of first-order elastic constants and their pressure dependence, which have not been calculated and measured yet. Band structure, density of states and pressure coefficients of energy band gaps are given. The obtained results for band structure using EV-GGA are larger than that of GGA. We calculated the frequency dependent complex dielectric function ε2(ω) for radiation up to 30 eV. The assignment of the critical points to the band structure difference at various points of the Brillouin zone was made. The pressure and volume dependence of the static dielectric constant and the refractive index were calculated.

A new correlation between ultrasonic shear wave velocity and Poisson’s ratio has been established for isotropic solid materials, based on the data generated experimentally and collected from the literature. Poisson’s ratio has been found to decrease with increasing ultrasonic velocity in various solid materials such as metals and alloys, ceramics and glasses, intermetallics and polymers. The slope of the plot of the ultrasonic velocity against Poisson’s ratio is found to be almost constant for any given alloy system with different microstructures associated with various heat treatments, alloying elements, grain size, temperature effect, etc. Further, it has been demonstrated that ultrasonic shear wave velocity is a better parameter for materials characterization as compared to longitudinal wave velocity.

Ab-initio methods have been employed to investigate the electronic and elastic properties of beryllium chalcogenides (namely BeS, BeSe and BeTe). The electron momentum density, autocorrelation function and energy band gap have been computed using the linear combination of atomic orbitals method. Using the full potential linearized augmented plane-wave and projector-augmented wave methods, the energy bands and density of states (DOS) along with elastic properties are also calculated. The electronic band structure, total and partial DOS and elastic moduli obtained from the present calculations are found to be in good agreement with available earlier data. The calculated valence band width, equal valence electron density curve and bulk modulus confirm the trend of ionicity BeS>BeSe>BeTe.

Summary The study deals with determination of intrinsic formation strength from well log data, to analyse sandcut behaviour of exploratory gas wells in Daman formation of C-24 area of Tapti-Daman, Western Offshore, India. The intrinsic formation strength has been estimated through computation of elastic constants from the acoustic well log data. The dynamic elastic constants viz. shear and bulk modulii

We have performed a first principles study of structural, mechanical, electronic, and optical properties of orthorhombic Sb2S3 and Sb2Se3 compounds using the density functional theory within the local density approximation. The lattice parameters, bulk modulus, and its pressure derivatives of these compounds have been obtained. The second-order elastic constants have been calculated, and the other related quantities such as the Young's modulus, shear modulus, Poisson's ratio, anisotropy factor, sound velocities, Debye temperature, and hardness have also been estimated in the present work. The linear photon-energy dependent dielectric functions and some optical properties such as the energy-loss function, the effective number of valance electrons and the effective optical dielectric constant are calculated. Our structural estimation and some other results are in agreement with the available experimental and theoretical data.

Structural, electronic, elastic and optical properties of the cubic-antiperovskite-type ANSr3, with A=As, Sb and Bi, are studied under pressure effect using the full-relativistic version of the full-potential augmented plane wave plus local orbitals method (FP-APW+lo). The exchange–correlation potential is treated by the generalized gradient approximation within the scheme of Perdew, Burke and Ernzerhof (GGA-PBE). Also we have used Engel and

A force field for the modeling of hydroxyapatite; Ca10(PO4)6OH2 (HAP) is established based upon transferable potentials. Ca–O, P–O and O–O potentials were transported from those previously published for fluorapatite and based on single crystal experimental data. The interactions of hydroxyl oxygen with calcium and phosphate were re-scaled by fitting to experimental data for CaO and AlPO4, respectively, to account for the reduction in the oxygen charge from −2.0 to −1.426. Force field accuracy is tested by comparing the calculated and experimental values for the cell constant and atom positions in the unit cell. The elastic constants and bulk modulus calculated for HAP are in close agreement with the experimental results. The potentials were also used to calculate the compressibility data of HAP and fluorapatite, and these results also agree with the published experimental data. Using formal charges for metal cations allows modeling the complete solid solution of Cd–Ca hydroxyapatite with a good accuracy.