Unraveling the Complexity of Nano-Dispersoids in the Oxide Dispersion Strengthened Alloy 617.

Nanocrystalline oxides are mainly responsible for Ni-base oxide dispersion strengthened (ODS) superalloys excellent thermo-mechanical properties. To establish the microstructural correlations between the metallic matrix and various oxide dispersoids, we report here the atomic-scale structure and chemistry of the complex nano-oxide dispersoids. Ultrahigh-resolution Cs-aberration-corrected scanning transmission electron microscopy (STEM) based techniques have been used to resolve nano-dispersoids in the Alloy 617 ODS. These nano-oxides, interestingly, possess a variety of high-angle annular dark-field (HAADF) contrasts, that is, bright, dark, and bi-phases. Both the light and heavy atoms have been found to be present in Y­Al­O complex-oxide nanostructures in varying quantities and forming a characteristic interface with the metallic matrix. In overcoming the limitation of conventional STEM-HAADF imaging, the integrated differential phase-contrast imaging technique was employed to investigate the oxygen atoms along with other elements in the dispersoids and its interface with the matrix. The most intriguing aspect of the study is the discovery of a few atoms thick Al2O3 interlayer (shell) around a monoclinic Y­Al­O core in the Ni-matrix. On the other hand, when the dispersoid is a hexagonal type Y­Al­O complex, the interface energy is already low, maintaining a semi-coherent interface and it was devoid of a shell.

Effect of nano-hydroxyapatite incorporation on fluoride-releasing ability, penetration, and adaptation of a pit and fissure sealant.

BACKGROUND: Dental caries is one of the most common multifactorial oral diseases and can be prevented using pit and fissure sealants. AIM: To evaluate the effect of nano-hydroxyapatite (nanoHAP) incorporation on fluoride-releasing ability, penetration, and adaptation of a pit and fissure sealant. DESIGN: This was an in vitro study with two groups: conventional sealant and nanoHAP-incorporated sealant. Sealant penetration and adaptation were assessed using stereomicroscope and scanning electron microscope (SEM) (15 and 10 samples per group, respectively). Fluoride release was analyzed using ion-selective electrode (15 samples per group). The chi-square test was used to compare penetration and adaptation between the 2 groups, and an independent Student t test was used to compare fluoride release. RESULTS: The nanoHAP group showed significantly more samples with no bubbles (P = .001) and no debris (P < .001). SEM analysis showed a significantly greater percentage of adequate fissures in the test group (P = .007). The fluoride release was significantly higher in test samples with p values of .001 and .016 on day 1 and day 60, respectively. CONCLUSION: The incorporation of nanoHAP into the conventional pit and fissure sealant improved its penetration and adaptation properties along with fluoride release.

Study of Crystallographic Texture Evolution during High-Temperature Deformation of 18Cr-ODS Ferritic Steel based on Plasticity Assessment.

This paper aims at understanding the texture evolution in extruded oxide dispersion strengthened 18Cr ferritic steel during high-temperature uniaxial compression testing at 1,423 K at a strain rate of 0.01/s based on extensive electron back scatter diffraction characterization. The α-fiber texture is observed along the extrusion direction (ED) in the initial microstructure. The flow curves generated during uniaxial compression test are used to determine the associated hardening parameters. In addition, the degree of texture evolution after deformation along the ED and the transverse direction (TD) with respect to the initial condition has been predicted using VPSC-5 constitutive model. The prediction shows that the deformation along the ED produces a dominant γ-fiber texture in contrast to the TD. This is in agreement with the experimental results where γ-fiber texture is observed, due to enhanced dynamic recrystallization at high-temperature deformation.

Comparison of Induced Sputum and Bronchoalveolar Lavage Fluid Examination in the Diagnosis of Sputum Negative Pulmonary Tuberculosis.

BACKGROUND: Tuberculosis (TB) is one of the common infections in the world, especially in developing countries like India. Therefore, early diagnosis is important. This study was undertaken to compare the yield of sputum, induction with bronchoalveolar lavage (BAL) in smear-negative suspected pulmonary TB patients in a tertiary care hospital in Agra. METHODS: Fifty patients were included in the study. In all patients, induced sputum, fibreoptic bronchoscopy and BAL fluid were subjected to diagnostic testing. RESULTS: On acid-fast smear examination, induced sputum and BAL fluid tested positive in 27/50 and 25/50 patients, respectively with a sensitivity of 83.3% and 90% respectively (p<0.0001). On comparing sputum induction versus BAL on culture, 30 patients were positive by sputum induction and 27 patients were positive on BAL fluid, with the sensitivity of 85.7% and 77.1%, respectively. The results showed that the sputum induction showed a significantly higher yield than that of BAL fluid (p=0.0013). CONCLUSION: Sputum induction offers an alternative approach in the diagnosis of smear-negative suspected pulmonary TB patients and would enhance sensitivity for the diagnosis of TB.

Electronic and Vibrational Decoupling in Chemically Exfoliated Bilayer Thin Two-Dimensional V2O5.

The synthesis of high-quality two-dimensional (2D) transition metal oxides is challenging compared to 2D transition metal dichalcogenides as a result of the exotic surface changes that can appear during formation. Herein, we report the synthesis of bilayer 2D V2O5 nanosheets with a thickness of ∼1 nm using the chemical exfoliation method and a comprehensive study on the vibrational and optical properties of bilayer 2D V2O5. We report, for the first time, a thickness-dependent blue shift of 1.33 eV in the optical bandgap, which signifies the emergence of electronic decoupling in bilayer 2D V2O5. In addition, a thickness-dependent vibrational decoupling of phonon modes observed via Raman spectroscopy fingerprinting was verified by computing the lattice vibrational modes using the density functional perturbation theory. We demonstrate that the manifestation of the electronic and vibrational decoupling can be used as a benchmark to confirm the successful formation of bilayer 2D V2O5 from its bulk counterpart.

Synthesis and characterization of nanocrystalline Ti(1-x)Al(x)N by reactive magnetron sputtering.

Ti(1-x)Al(x)N metastable films were synthesized by reactive magnetron co-sputtering with different Ti to Al ratios. XRD studies showed that as-deposited films were crystalline for concentrations of Al (35, 40, 55 and 64%) and become amorphous at 81% Al. These films were annealed at 1073 K to study the phase separation. Films up to 55% Al did not show any phase separation after annealing. But films with 64% Al splits into c-TiAIN and c-AIN, whereas films with 81% Al split into cubic-TiN and hex-AIN. Distribution of crystallites and their size were analyzed by TEM. High density of crystallites with dimensions between 3-11 nm was dispersed in amorphous matrix for 64% Al films. Nanoindentation technique was used to determine the mechanical properties of these films without substrate effect. Maximum hardness obtained for as deposited and annealed films (64% Al) were 35 GPa and 38 GPa, respectively.