Some Thermodynamic Aspects of the Oxides of Chromium

To understand Cr emissions from slag melts to a vapor phase, an assessment of the stabilities of the chromium oxides at high temperatures has been carried out. The objective of the present study is to present a set of consistent data corresponding to the thermodynamic properties of the oxides of chromium, with special reference to the emission of hexavalent chromium from slags. In the current work, critical analysis of the experimental data available and a third analysis in the case of Cr₂O₃ have been carried out. Commercial databases, Fact Sage and ThermoCalc along with NIST-JANAF Thermochemical Tables, have been used for the analysis and comparisons of the results that are presented. The significant discrepancies in the available data have been pointed out. The data from NIST-JANAF Thermochemical Tables have been found to provide a set of consistent data for the various chromium oxides. An Ellingham diagram and the equations for the ΔG° (standard Gibbs free energy change) of formation of CrO _x have been proposed. The present analysis shows that CrO₃(g) is likely to be emitted from slag melts at high oxygen partial pressures.     

Development of cerium and silicon co-doped hydroxyapatite nanopowder and its in vitro biological studies for bone regeneration applications

Multi-ion, co-substituted bioactive glass ceramics play a significant role in the stimulation of physical and biological properties for outstanding effects in biomedical application. The following work attempts to develop HAP as a parent material doped with a combination of cerium (Ce⁴⁺ @1.25?wt%) and silicon (Si⁴⁺ @1, 3 and 5?wt%) by refluxing based sol-gel technique. The anti-bacterial tests exhibit E. coli showing higher inhibition efficiency, in vitro hemolytic test exhibit good compatible nature of dual doped HAP with erythrocytes (<5% of hemolytic). In vitro bioactivity assay confirms that the developed dual doped HAP possesses excellent bone-like apatite layer formation on their surfaces. In vitro cellular study was performed for Ce/Si-HAP@5% powder against MG-63 cells, which demonstrated the good cell viability at higher concentrations (up to 800?µg/ml). Further, dual doped HAP powders were characterized by various analytical techniques such as ATR-FTIR, Powder-XRD, TGA-DTA, SEM-EDS, TEM and XPS analysis. The studies confirm that the synthesized dual doped HAP will act as better bioactive glass ceramics for potential orthopedic and dentistry applications.     

Metal organic frameworks as electrocatalysts: Hydrogen evolution reactions and overall water splitting

The development of clean energy technologies to protect the environment is an important demand of the times. Electrocatalysis is emerging as a promising method for evolution of hydrogen and overall water splitting. Nowadays, metal organic frameworks (MOFs) have emerged as electrocatalysts having uniformly distributed active sites and high electrical conductivity. This review summarizes the latest advances in heterogeneous catalysis by MOFs and their composite/derivatives for efficient hydrogen evolution reaction (HER) and water splitting. Pristine MOFs with their recent development are summarized first followed by composites of MOFs with their enhanced electrocatalytic performances. Overall water splitting by using bifunctional electrocatalysts derived from MOFs with different synthetic approaches is provided and this review gives the metal-based categorisation of precursor MOFs. Different strategies to improve chemical stability, conductivity, and overall electrocatalytic properties have been discussed. In the last, perspectives on the synthesis of efficient MOF-based electrocatalyst materials are provided.     

A clustered locally linear approach on face manifolds for pose estimation

Data points with small variations between them are assumed to lie close to each other on a smooth varying manifold in the feature space. Such data are hard to classify into separate classes . A sequence of face pose images with closely varying pose angles can be considered as such data. The pose angles when large enough create images that are largely differing from each other, and thus, the sequence of face images can be assumed to be on or near a nonlinear manifold. In this paper, we propose an unsupervised pose estimation method for face images based on clustered locally linear manifolds using discriminant analysis. We divide the data into multiple disjointed, locally linear and separable clusters. The problem of identifying which cluster to use is solved by dividing the entire process into two steps. The first step or projection using the entire smooth manifold identifies a rough region of interest. We use clustering techniques on entire data to form the pose-dependent classes which are then used to find the first set of discriminant functions. The second step or second projection uses trained cluster(s) from this neighbourhood to obtain a second set of discriminant functions. The idea behind such an approach is that the local neighbourhood would be linear and provide better between-class separation, and hence, the classification problem would now be simpler.     

A hybrid approach to computing electrostatic forces in fluidized beds of charged particles

In particulate flow devices particles acquire electric charge through triboelectric charging, and resulting electrostatic forces can alter hydrodynamics. To capture this effect, the electrostatic force acting on individual particles in the device should be computed accurately. Electrostatic force is calculated using a hybrid approach consisting of: (1) long‐range contributions from an Eulerian electric field solved using the Poisson equation (2) short‐range contributions calculated using a truncated pairwise sum and (3) a correction to avoid double counting. Euler‐Lagrange simulation of flows incorporating this hybrid approach reveals that bed height oscillations in small fluidized beds of particles with monopolar charge decreases with increasing charge level, which is related to lateral segregation of particles. A ring‐like layer of particles, reported in experimental studies, forms at modestly high charge levels. Beds with equal amounts of positively and negatively charged particles are fluidized in a manner similar to uncharged particles. © 2016 American Institute of Chemical Engineers AIChE J, 62: 2282–2295, 2016     

Weldability and microstructural variations in weldments of Ti-5Ta-1.8Nb alloy

The successful replacement of the present generation of corrosion-resistant materials (nitric acid-grade stainless steel and Ti) by Ti-5Ta-1.8Nb, which has better corrosion resistance, depends on its weldability characteristics. This article presents the results of a study on the fabrication, qualification, and microstructural characterization of the welds. Welding was carried out using the direct current electrode negative (DCEN) polarity tungsten inert gas (TIG) (manual) welding method with high-purity Ar shielding. Testing was carried out as per the ASME standard (section IX, welding and brazing). Qualification tests found that the weldment met the required properties. The weldment showed heterogeneous microstructures, which are rationalized based on differences in phase transformation mechanisms that are dictated by the thermal cycles experienced by various microscopic regions. The results, described in this article, confirm that the weldability of the developmental Ti-Ta-Nb alloy is excellent. A preliminary evaluation of the corrosion behavior of the welds showed rates comparable to that of the base metal, establishing that this alloy could be considered as an alternative material for use in highly corrosive environments.     

A Ultra-Wideband Amplitude Modulation (AM) Detector Using Schottky Barrier Diodes Fabricated in Foundry CMOS Technology

Utility of Schottky diodes fabricated in foundry digital 130-nm CMOS technology is demonstrated by implementing an ultra-wideband (UWB) amplitude modulation detector consisting of a low-noise amplifier (LNA), a Schottky diode rectifier, and a low-pass filter. The input and output matching of the detector is better than -10 dB from 0-10.3 GHz and 0-1.7 GHz, respectively, and almost covers the entire UWB frequency band (3.1-10.6 GHz). The measured peak conversion gain is -2.2dB. The sensitivity over the band for amplitude modulation with the minimum E _b/N_o of 6 dB is between -53 and -56 dBm. The power consumption is only 8.5 mW     

Epitaxial nucleation model for chiral-selective growth of single-walled carbon nanotubes on bimetallic catalyst surfaces

An epitaxial nucleation model for single-walled carbon nanotube (SWCNT) growth on bimetallic catalysts surfaces is reported in support of experimental observations of chiral enrichment. We model the bimetallic catalyst surfaces as a 2D (1 1 1) surface consisting of Ni or a combination of Ni and Fe atoms, with varying average bond length between nearest neighbor atoms which corresponds to the crystal structure of the alloys. The energies associated with nanotube cap formation on these various surfaces are calculated using density functional theory (DFT). We find that certain cap chiralities, such as (8, 4), are more stably bound to a surface that resembles a Ni_0.27Fe_0.73 bimetallic catalyst, whereas other chiralities, such as (9, 4), are more stable on a pure Ni surface. These results help explain the predominance of certain chiralities on specific bimetallic catalysts and provide a potential route to controlling the chirality of as-grown SWCNTs.     

Synthesis,spectral, thermal,and chelation potentials of polymeric hydrazone based on 2,4‐dihydroxy benzophenone

A chelating polymer, poly(2,4‐dihydroxy benzophenone hydrazone–formaldehyde) [poly(DHBPH–F)], was synthesized by the polycondensation of 2,4‐dihydroxy benzophenone hydrazone with formaldehyde in the presence of oxalic acid as a catalyst. Poly(DHBPH–F) was characterized by Fourier transform infrared and ¹H‐NMR spectral data. The molecular weight of the polymer was determined by gel permeation chromatography. Polychelates were obtained when the dimethylformamide solution of the polymer containing a few drops of ammonia was treated with an aqueous solution of metal ions. Elemental analysis of the polychelates indicated that the metal–ligand ratio was 1 : 2. The IR spectra of the polymer–metal complexes suggested that the metals were coordinated through the oxygen of the phenolic? OH group and the nitrogen of the azomethine group. The electron paramagnetic resonance and magnetic moment data indicated a square planar configuration for Cu(II) chelate and an octahedral structure for Ni(II) chelate. The thermogravimetric analysis, differential scanning calorimetry, and X‐ray diffraction data indicated that the incorporation of the metal ions significantly enhanced the degree of crystallinity. The polymerization initiation, electrical conductivity, and catalytic activity of the polychelates are discussed. Heavy‐metal ions [viz., Cu(II) and Ni(II)] were removed with this formaldehyde resin, and the metal‐ion uptake efficiency at different pH's, the nature and concentration of the electrolyte, and the reusability of the resin were also studied. © 2010 Wiley Periodicals, Inc. J Appl Polym Sci, 2010     

Evaluation of concentration dependant diffusion coefficients of carbon in a dissimilar joint of ferritic steels

When dissimilar weldments between 9Cr-1Mo and 2¼Cr-1Mo ferritic steels are exposed to high temperature, microstructural and microchemical modifications are observed near the weld interface. Diffusion of carbon driven by the activity gradient from low Cr to high Cr steel leads to the formation of carbon enriched ‘hard’ zone and carbon depleted ‘soft’ zone near the fusion joint. The present paper deals with the measurement of carbon diffusion profiles and the evaluation of concentration dependent diffusion coefficients of carbon across the interface at a temperature of 1023 K. Accurate carbon concentration profiles are generated using carbon calibration graph. The profiles are smoothened to reduce the experimental scatter and the concentration dependant diffusion coefficients are determined using Den Broeder’s method. In the base materials, where the concentration gradient is extremely small, D(c) values are determined using Hall’s method. Variation in D(c) across the weld interface is understood based on the microstructural and microchemical changes that take place during heat treatment.