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Porosity dependence of elastic constants in aluminum nitride ceramics
Yoshimura, Humberto Naoyuki;Molisani, André Luiz;Narita, Nilson Eiji;Cesar, Paulo Francisco;Goldenstein, Hélio;
Materials Research , 2007, DOI: 10.1590/S1516-14392007000200006
Abstract: aluminum nitride is a relatively new engineering ceramic and its mechanical properties have not been extensively studied. in this work, the effects of porosity (~0 to 38%) on sonic velocities, poisson's ratio, and elastic moduli of partially sintered a1n, both pure and with additives, were investigated. the elastic constants, determined by the ultrasonic pulse-echo method, were significantly influenced by the porosity, but not by the different types of additives used (2 wt. (%) of caco3, cao, and y2o3). all elastic constants evaluated decreased with increasing porosity, but the rates of decrease were higher for elastic moduli compared do sonic velocities and poisson's ratio. the results were analyzed in the light of stress concentration and loading bearing area models proposed in the literature.
Frequency Dependence of the Dielectric Constants and of the Reflectivity for HfO2 and ZrO2 from First-Principles Calculations  [PDF]
C. C. Silva,H. W. Leite Alves,L. M. R. Scolfaro
Physics , 2006, DOI: 10.1063/1.2729892
Abstract: We present, in this work, our theoretical results for the phonon dispersions and the frequency dependence of the reflectivities and the dielectric constants of ZrO2 and HfO2 in the monoclinic phase. The results show the importance of the lattice contribution for the evaluation of the static dielectric constant. Also, besides the anisotropy shown by these materials along the x and z directions, the zero frequency static dielectric constant decreases with the increasing pressure.
Frequency dependence of the electrical conductivity and dielectric constants of polycarbonate (Makrofol-E) film under the effects of γ-radiation  [PDF]
Soad Fares
Natural Science (NS) , 2011, DOI: 10.4236/ns.2011.312129
Abstract: Irradiation effects of γ-radiation on the physical and electrical properties of polycarbonate (Makrofol-E( film has been studied to be able to investigate the dielectric response of irradiated polymers for a wide range of fluence and frequency. The dielectric constant (ε') The loss tangent (tanδ), dielectric loss factor (ε''), the a.c electrical conductivity (σ) and the relaxation time (τ), were measured in the frequency range from (40) Hz to (4) MHz. These samples were irradiated by means of γ-rays from 10 up to 200 KGy. The change in different properties as a function of absorbed dose was studied. Degradation of the polymers leading to amorphisation was observed by increasing the absorbed γ- dose. The induced changes in the electrical conductivity due to γ-rays irradiation of Makrofol-E provide a better method for γ -dose measurements. A semi-empirical equation was developed to use Makrofol-E as a dielectric dosimeter. Furthermore, Makrofol-E has much greater resistance to radiation damage; the attained results suggested strongly the applicability of Makrofol-E to be used in medical products applications.
Frequency Dependence of the Electrical Conductivity and Dielectric Constants of Polycarbonate (Makrofol-E) Film under the Effects of γ-Radiation
American Journal of Materials Science , 2011, DOI: 10.5923/j.materials.20110101.08
Abstract: Irradiation effects of γ-radiation on the physical and electrical properties of polycarbonate (Makrofol-E( film has been studied to be able to investigate the dielectric response of irradiated polymers for a wide range of fluence and frequency. The dielectric constant ( )The loss tangent ( tanδ ), dielectric loss factor (ε ), the a.c electrical conductivity (σ) and the relaxation time (τ), were measured in the frequency range from (40) Hz to (4)MHz. These samples were irradiated by means of γ-rays from 10 up to 200 KGy. The change in different properties as a function of absorbed dose was studied. Degradation of the polymers leading to amorphisation was observed by increasing the absorbed γ-dose. The induced changes in the electrical conductivity due to γ -rays irradiation of Makrofol-E provide a better method for γ -dose measurements. A semi-empirical equation was developed to use Makrofol-E as a dielectric dosimeter. Furthermore, Makrofol-E has much greater resistance to radiation damage; the attained results suggested strongly the applicability of Makrofol-E to be used in medical products applications.
Multipactor suppressing titanium nitride thin films analyzed through XPS and AES
Castro-Colin, M;Durrer, W;López, J.A;Pinales, L.A;Encinas Baca, C;Moller, D;
Revista mexicana de física , 2008,
Abstract: cathodic-magnetron-deposited titanium nitride films were grown on anodized aluminum substrates and studied via aes and xps spectro-scopies to determine their depth-dependence composition. as it is well known, the native oxide grown on aluminum does not make the substrate impervious to radio frequency damage, and typically a thin film coating is needed to suppress substrate damage. in this article we present the profile composition of titanium nitride films, used as a protective coating for aluminum, that underwent prior conditioning through anodization, observed after successive sputtering stages.
Multipactor suppressing titanium nitride thin films analyzed through XPS and AES  [cached]
M. Castro-Colin,W. Durrer,J.A. López,L.A. Pinales
Revista mexicana de física , 2008,
Abstract: Cathodic-magnetron-deposited titanium nitride films were grown on anodized aluminum substrates and studied via AES and XPS spectroscopies to determine their depth-dependence composition. As it is well known, the native oxide grown on aluminum does not make the substrate impervious to radio frequency damage, and typically a thin film coating is needed to suppress substrate damage. In this article we present the profile composition of titanium nitride films, used as a protective coating for aluminum, that underwent prior conditioning through anodization, observed after successive sputtering stages.
Theoretical study of the elastic properties of titanium nitride

Dong CHEN,Jingdong CHEN,Yinglu ZHAO,Benhai YU,Chunlei WANG,Deheng SHI,

金属学报(英文版) , 2009,
Abstract: The equilibrium lattice parameter, relative volume V/Vo, elastic constants Cij, and bulk modulus of titanium nitride are successfully obtained using the ab initio plane-wave pseudopotential (PW-PP) method within the framework of density functional theory. The quasi-harmonic Debye model, using a set of total energy vs molar volume obtained with the PW-PP method, is applied to the study of the elastic properties and vibrational effects. We analyze the relationship between the bulk modulus and temperature up to 2000 K and obtain the relationship between bulk modulus B and pressure at different temperatures. It is found that the bulk modulus B increases monotonously with increasing pressure and decreases with increasing temperature. Moreover, the Debye temperature is determined from the non-equilibrium Gibbs func-tions.
Dielectric Screening in Atomically Thin Boron Nitride Nanosheets  [PDF]
Lu Hua Li,Elton J. G. Santos,Tan Xing,Emmanuele Cappelluti,Rafael Roldán,Ying Chen,Kenji Watanabe,Takashi Taniguchi
Physics , 2015, DOI: 10.1021/nl503411a
Abstract: Two-dimensional (2D) hexagonal boron nitride (BN) nanosheets are excellent dielectric substrate for graphene, molybdenum disulfide and many other 2D nanomaterials based electronic and photonic devices. To optimize the performance of these 2D devices, it is essential to understand the dielectric screening properties of BN nanosheets as a function of the thickness. Here, electric force microscopy along with theoretical calculations based on both state-of-the-art first-principles calculations with van der Waals interactions under consideration and non-linear Thomas-Fermi theory models are used to investigate the dielectric screening in high-quality BN nanosheets of different thicknesses. It is found that atomically thin BN nanosheets are less effective in electric field screening, but the screening capability of BN shows a relatively weak dependence on the layer thickness.
Colossal Dielectric Constants in Braced Lattices with Defects  [PDF]
A. P. Ramirez,G. Lawes,V. Butko,M. A. Subramanian,C. M. Varma
Physics , 2002,
Abstract: The dielectric constant of CaCu3Ti4O12 is measured with a different electrode geometry than previous measurements. Similar colossal values are obtained showing that they are "intrinsic" to the material. We show that in braced structures such as CaCu3Ti4O12, a small concentration O(10-3) of defects, which disrupt the bracing and relax between different equivalent configurations, can lead to colossal dielectric constants above a characteristic temperature. The dielectric constant e(w,T) has a frequency and temperature dependence of the same form as found experimentally.
Colloidal Plasmonic Titanium Nitride Nanoparticles: Properties and Applications  [PDF]
Urcan Guler,Sergey Suslov,Alexander V. Kildishev,Alexandra Boltasseva,Vladimir M. Shalaev
Physics , 2014,
Abstract: Optical properties of colloidal plasmonic titanium nitride nanoparticles are examined with an eye on their photothermal via transmission electron microscopy and optical transmittance measurements. Single crystal titanium nitride cubic nanoparticles with an average size of 50 nm exhibit plasmon resonance in the biological transparency window. With dimensions optimized for efficient cellular uptake, the nanoparticles demonstrate a high photothermal conversion efficiency. A self-passivating native oxide at the surface of the nanoparticles provides an additional degree of freedom for surface functionalization.
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