[en] Mode-I delamination crack growth in Ceramic Matrix Composite (CMC) materials is studied using experiments and associated numerical modeling. Double cantilever beam tests were conducted to measure delamination growth characteristics and the associated mode-I critical energy release rate. The tests revealed significant crack growth resistance (R-curve) behavior with the load carrying capacity increasing with the delamination growth. The experimentally observed load-displacement response could not be explained by linear elastic fracture mechanics or by a two-parameter triangular cohesive finite element models. The observed crack growth resistance behavior is explained by incorporating cohesive traction-separation relationship with a bilinear softening resulting in a long “tail”, which is interpreted and modeled as a superposition of two traction-separation relationships representing mechanisms associated with near crack-tip region and fiber-bridging in the crack-wake, respectively.

[en] Highlights: • Ion irradiation of PET polymer (used for gas separation applications) for structural, optical, chemical, surface and free volume studies. • The amorphization and decrease of the band gap energy after ions irradiation. • The value of R increased after ion irradiation due to the expansion of the polymeric chains and increase of the size of cavities. • Increase in the surface roughness creating the site of track formation. - Abstract: Topographic micro scale and in-depth nano scale level modifications of polymeric materials play an important role in engineering their physical and chemical properties. Polyethylene terephthalate (PET) is an important class of semi-crystalline polymers used for gas separation properties. The gas diffusion and permeability parameters are directly related to the free volume fractions and the hole distributions. The controlled and precise ion beam irradiation can be used to induce surface and in-depth modifications in the properties of the polymers which help in modifying free volume holes and their distributions. In the present study, the investigation of free volume (nano scale level) and surface (micro scale level) properties of PET polymeric thin films after SHI treatment were employed by means of positron annihilation lifetime spectroscopy (PALS) and atomic force microscopy (AFM), respectively. The PET thin films were irradiated by 50 MeV lithium ions as a function of ion fluence. The value of hole radius (R) and intensity (I_3) of o-Ps were observed to be increased after ion beam treatment. The further analyses were employed to calculate the free volume and fractional free volume of holes from the obtained values of R and I_3. The AFM studies reveal the surface modifications of the irradiated polymer films. The structural, optical and chemical properties were investigated by X-ray diffraction (XRD), UV–visible (UV–vis) and Fourier transform infrared (FTIR) spectrophotometry. Different parameters such as crystallite size and band gap energy were calculated from the obtained data of XRD and UV–vis, respectively

[en] Crystalline thin films of cobalt doped SnO_2 undergoes modification by dense electronic excitation induced by Swift Heavy Ion (SHI) irradiation using 100 MeV Au"8"+ ion beam. Atomic Force Microscopy (AFM) and Power Spectral Density (PSD) analysis shows that the surface modification is dominated by diffusion of surface adatoms. Modification in surface features viz. grain size, rms roughness and roughness exponent can be controlled with homogeneity in surface features due to dense electronic excitation as observed from AFM-PSD and MFM analysis. X-ray diffraction results shows formation of new crystalline phase due to dense electronic excitation. The variation in strain along (101) and (110) crystal plane are nearly equal at irradiation fluence of 5 × 10"1"2 ions/cm"2 as calculated using X-ray diffraction results. UV–Visible studies shows formation of local energy states within the optical band gap region due to modification in electronic state of the system. The significant variation in Urbach's energy at irradiation fluence of 5 × 10"1"2 ions/cm"2 was observed. Transition in magnetic property after critical irradiation fluence of 5 × 10"1"2 ions/cm"2 with high coercivity and lowest saturated magnetization is observed. Resonance RBS studies shows Impurity free phase formation and amorphization causes reduction in density of the target due to amorphization. Very small modification in room temperature electrical conductivity was observed. Overall results shows that the modification in impurity free phase occurred by 100 MeV Au"8"+ ion irradiation in cobalt doped SnO_2 thin films is tough to achieve by other techniques. - Highlights: • Modification in surface features, Grain & Particle size can be controlled. • Same variation in strain along (101) and (110) crystal plane at fluence of 5 × 10"1"2 ions/cm"2. • Formation of local energy states due to modification in electronic states induced by SHI. • RT-FM Co doped SnO_2 is due to combine effect of magnetic dopant and point defects. • Density of the target is reduced during impurity free phase transformation

[en] Highlights: • Synthesis of Zirconia nanoparticles with and without surfactants by co- precipitation method. • Surface modification of ZrO_2 nanoparticles. • Phase transition with different concentration of surfactants. • Dielectric behavior of bare, CTAB assisted and SDS assisted ZrO_2 nanoparticles. - Abstract: In the present paper, we report the synthesis of Cetyltrimethylammonium Bromide (CTAB) and Sodium dodecyl sulfate (SDS) assisted Zirconia (ZrO_2) nanoparticles by co-precipitation method. The effect of surfactant concentration on the structural and dielectric properties has been extensively studied. X-ray diffraction studies reveal the formation of tetragonal phase in the ZrO_2 nanoparticles prepared by lower CTAB concentration. However, for higher concentration of CTAB some traces of monoclinic phase appeared along with tetragonal phase. SDS assisted nanoparticles shows crystalline tetragonal phase with lower concentration of SDS and amorphous nature with higher concentrations of SDS. FTIR results show the presence of Zr–O symmetrical stretching vibrations at tetrahedral site. The dielectric properties of all samples have been studied from 10 Hz to 1 MHz, revealing the low value of dielectric constant with CTAB and very high value with SDS as compared to bare ZrO_2 nanoparticles. The dielectric behaviour of the bare and surfactant assisted nanoparticles has been correlated with the phase transition, size of nanoparticles and the nature of surfactants.

[en] Indoor radon has been recognised as one of the health hazards for mankind especially when the uranium rich material lies close to the surface of the earth. Wide spread uranium mineralization is associated with copper, nickel and other sulphides in the Singhbhum shear zone developed at the northern margin of the Singhbhum craton in the state of Jharkhand of India. Emanation of radon an α-active inert gas is associated with the presence of uranium in ground whose concentration varies with specific sites and geological materials. Measurements of radon exhalation rate in rock samples from Surda copper mine area have been carried out. Can technique using LR-115 type II plastic track detector has been used for measurements. Uranium, thorium and potassium concentrations have been measured through low level gamma ray spectroscopy. Uranium concentration (activity) is found to vary from 135.8 to 4607.8 Bq/kg whereas the exhalation rate lies in the range 0.26 to 1.15 Bq m^-2 h^-1. Overall a positive correlation has been found between uranium concentration and radon exhalation rates. Results are compared with our earlier measurements in other mines regions of the Singhbhum shear zone. This area has the lowest uranium concentration and radon exhalation rate

[en] We report the synthesis of nanostructured austenitic AISI 304L stainless steel (SS) through cryorolling (CR) and reversion annealing in the temperature range of 700–800 °C. Severe CR at sub-zero temperature promotes twinning in γ-austenite, which transform into α'-martensite with lath thickness of 50–100 nm. Whereas, 50–300 nm size γ-grains recrystallize in nano-twinned α' through reversion annealing as confirmed by transmission electron microscopy (TEM) and electron back scattered diffraction (EBSD) imaging. The evolution of highly processable bulk nano-austenitic SS with bimodal grain size distribution on achieving high strength (~1295 MPa), large tensile ductility (~0.47), and true necking strain of 0.59, have been discussed

[en] In this work, density functional theory plane-wave pseudo potential method with generalized gradient approximation is used to investigate the elastic, mechanical, phonon and thermodynamic properties of LuAuPb and YAuPb compounds. The physical properties such as elastic constants, bulk modulus, shear modulus, Young's modulus, Poisson's ratio and shear anisotropy factor of both the compounds are calculated. The elastic properties of these compounds reveal that these compounds are mechanically stable. Further, the phonon dispersion curves prove that these compounds are also dynamically stable. The study of shear anisotropic factor gives purely anisotropic nature of these compounds. Pugh's and Frantsevich's ratio shows that both these compounds exhibit ductile nature. The sound velocities and Debye temperature of these compounds are also estimated from elastic constants. Using the slack equation, the lattice thermal conductivity of these compounds is also estimated. At room temperature, LuAuPb attains low thermal conductivity as compared to YAuPb. At 300 K, the calculated values of specific heat capacity per atom at constant volume for LuAuPb and YAuPb compounds are 24.37 Jmol⁻¹ K⁻¹ and 23.95 Jmol⁻¹ K⁻¹ respectively. This is the first quantitative theoretical estimation of these properties. - Highlights: • We found that LuAuPb and YAuPb are mechanically as well as dynamically stable. • The elastic properties of these compounds are calculated for the first time. • At 300 K, LuAuPb attains low lattice thermal conductivity as compared to YAuPb. • The Debye temperature of these compounds are estimated also.

[en] CR-39 is a polycarbonate widely used as SSNTD for recording nuclear charged particles and in other applications. Latent ion tracks produced in the polymers due to the damage produced by the passage of Swift Heavy Ions contain amorphous material with highest degree of disorder, changing the free volume properties which have strong correlation with the macroscopic properties of the material. Positron annihilation lifetime spectroscopy (PALS) provides direct information about the dimension, content and hole size distribution of free volume in polymers. The effect of irradiation of ⁴⁰Ar (14.9 MeV/n) ions on CR-39 polycarbonate by Positron Annihilation Lifetime Spectroscopy (PALS) is reported here. PALS provides a non-destructive and non-interfering probe, having high detection efficiency for free volume hole properties. From o-Ps lifetime mean free volume hole radius and average free volume of the micro-voids have been calculated. PAL measurement shows an increase in free volume on irradiation

[en] Coal contains naturally occurring radionuclides arising from the uranium and thorium series. Burning of coal is one of the sources of the technologically enhanced exposure of human beings from natural radionuclides. The population is exposed to radiation which are discharged to the environment by the emissions from thermal power stations in gaseous and particulate form containing radioisotopes. This paper presents the measurements of airborne radon levels in the coal fired thermal power plants at Kasimpur (Uttar Pradesh), Lahra Mohabat at Bhatinda (Punjab) and at Durgapur (West Bengal) in India. Radon levels in the plants are found to be higher than in the Indian dwellings. Potential alpha activity, radon and its daughter concentration, and effective dose equivalent are obtained

[en] We calculate, here, the electromagnetic (em) neutron–proton mass difference analytically by using arctan ansatz in Skyrme model. The value so obtained is compared with those given in the literature. Our value agrees well with the widely accepted value in the literature. (author)