Structural Modifications and Extended Spectral Response of CeO2/CoPc Nanocomposites for Potential Applications

CeO₂/CoPc nanocomposites were synthesized by simple chemical method. Thermal behavior of these nanocomposites was studied by thermogravimetric and differential thermal analysis. The as‐synthesized nanocomposite samples were characterized by various techniques. A decrease in band‐gap energy together with an improved absorption intensity of the composite material confirms the role of the cobalt phthalocyanine in the absorption properties of CeO₂/CoPc composite. This study confirms structural modifications and extended spectral response of the synthesized CeO₂/CoPc nanocomposites. The results demonstrate that CeO₂/CoPc nanocomposite samples are promising materials for organic light‐emitting diodes, solar cells, and optoelectronic devices.     

A fourth-order accurate compact scheme for the solution of steady Navier-Stokes equations on non-uniform grids

This paper deals with the formulation of a higher-order compact (HOC) scheme on non-uniform grids in complex geometries to simulate two-dimensional (2D) steady incompressible viscous flows governed by the Navier-Stokes (N-S) equations. The proposed scheme which is spatially fourth-order accurate is then tested on three nonlinear problems, namely (i) a problem governed by N-S equations with a constructed analytical solution, (ii) lid-driven cavity flow problem, and (iii) constricted channel flow problem. In the process, we have also expanded the scope of fourth-order 9-point compact schemes to geometries beyond rectangular. It is seen to efficiently capture steady-state solutions of the N-S equations with Dirichlet as well as Neumann boundary conditions. In addition to this, it captures viscous flows involving free and wall bounded shear layers which invariably contain spatial scale variations. Our results are in excellent agreement with analytical and numerical results whenever available and they clearly demonstrate the superior scale resolution of the proposed scheme.     

Development of controlled strength-loss resorbable beta-tricalcium phosphate bioceramic structures

Controlling the strength-loss rate during biodegradation is a bottleneck in developing viable resorbable ceramic implants. Resorbable beta-tricalcium phosphate (β-TCP) bioceramic is known for its excellent biocompatibility. However, it exhibits poor sinterability and poor flexural strength. Here, we improved sintering behavior and biaxial flexural strength of β-TCP bioceramic without altering its biocompatibility by introducing multi-oxide sintering additives, in small quantities. These additives could also tailor the rate of resorption and hardness deterioration of β-TCP. A range of additives were prepared and introduced into β-TCP powder. Resultant powders were uniaxially pressed and sintered at 1250 °C, in air. Considerable improvement in densification (up to 33%) and biaxial flexural strength (up to 43%) were achieved. X-ray powder diffraction (XRD) analysis confirmed that the additives didn't alter the phase purity. In vitro cytotoxicity and biocompatibility analyses were performed using a prostate cancer cell-line. Results showed that the doped and pure β-TCP structures were non-toxic and biocompatible.     

Evaluation of the nutritional quality of four unexplored aquatic weeds from northeast India for the formulation of cost-effective fish feeds

A study was conducted to evaluate the nutritional potential of four commonly available, unexplored aquatic weeds namely, Salvinia cuculata, Trapa natans, Lemna minor and Ipomoea reptans from northeast India for ascertaining their suitability for utilization as supplementary fish feed with the aim to reduce the cost of commercial feeds. Results of proximate analysis showed that the crude protein content of the aquatic weeds ranged between 11.0% and 32.2% (w/w), whereas crude fibre and ash contents varied between 4.2% and 20% (w/w), and 13.3% and 31.2% (w/w), respectively. Protein to energy ratio (P/E) of these weeds ranged between 30.7 mg/kcal and 95.3 mg/kcal and the highest value was displayed by I. reptans. All these aquatic weeds contained high amounts of vitamins E and C and mineral elements required for the normal growth and development of fish.     

Antibacterial and dye degradation potential of zero‐valent silver nanoparticles synthesised using the leaf extract of Spondias dulcis

The present study reports a simple and low cost synthesis of zero‐valent silver nanoparticles (ZVSNPs) from silver nitrate using the leaf extract of Spondias dulcis. The ZVSNPs showed a unique peak at 420 nm in UV–vis spectrum. The SEM image portrayed cuboidal shaped particles. The EDX spectrum designated the elemental silver peak at 3 keV. In XRD, a sharp peak at 32.47° denoted the existence of (1 0 1) lattice plane and the average crystallite size was calculated as 48.61 nm. The lattice parameter was determined as 0.39 nm. The FTIR spectra of the leaf extract and ZVSNPs showed shifts in the specific functional group bands which ascertained the involvement of phytoconstituents in the formation and capping of nanoparticles. The average hydrodynamic size was measured as 59.66 nm by DLS method. A low PDI, 0.187 witnessed the monodispersity. A negative zeta potential value of −15.7 mV indicated the negative surface charges of the nanoparticles. The bactericidal action of ZVSNPs was demonstrated against two pathogens S.typhimurium and E.coli during which a dosage dependent zone of inhibition results was observed. Additionally, the catalytic potential of ZVSNPs was examined for the degradation of methylene blue dye in which an accelerated degradation of the dye was observed.Inspec keywords: antibacterial activity, crystallites, electrokinetic effects, scanning electron microscopy, nanoparticles, particle size, ultraviolet spectra, X‐ray chemical analysis, microorganisms, light scattering, nanofabrication, materials preparation, X‐ray diffraction, visible spectra, silver, dyes, Fourier transform infrared spectraOther keywords: wavelength 420.0 nm, Ag, voltage ‐15.7 mV, size 59.66 nm, size 0.39 nm, size 48.61 nm, electron volt energy 3.0 keV, Fourier transform infrared spectra, methylene blue dye, bactericidal action, dynamic light scattering, lattice parameter, Escherichia coli, Salmonella typhimurium, Spondias dulcis, negative zeta potential, polydispersity index, crystallite size, leaf extract, X‐ray diffraction, energy dispersive X‐ray spectrum, cuboidal‐shaped particles, scanning electron microscopy image, ultraviolet–visible spectrum, silver nitrate, zero‐valent silver nanoparticles     

Synthesis of SiC ceramics from processed cellulosic bio-precursor

Synthesis of SiC ceramic from processed cellulosic bio-precursor was investigated. Bamboo (Bambusa tulda Roxb.) plants abundantly available in the Jorhat district of Assam, India, were selected for extraction of fibers following Kraft pulping method and bleached bamboo pulp fibers were suitably cast in the form of rectangular boards. Coir fibers available in the Alleppy district of Kerala, India, were initially digested with dilute alkali, mixed with cellulose acetate solution, air dried and then hot-pressed at 140 ± 5 °C under 2.0–2.5 MPa pressure to make rectangular boards. Well-characterized processed bio-precursors were pyrolysed at ～800 °C under flowing N₂ atmosphere to prepare the bio-carbonaceous preforms (carbon templates) which showed nearly uniform shrinkages in all directions. Coir fiber composite board carbon showed lower pyrolytic weight loss (～66%), higher density (0.49 g cm^?3), lower porosity (～58%) and narrower pore diameter (10 μm) compared to the cast bamboo pulp fiber board carbon. The carbon samples showed perfect retention of fibrous morphological features of hierarchically grown bio-structures. Ceramization of carbon templates could be done by reactive melt silicon infiltration into porous channels at ～1600 °C under vacuum. The final ceramics were adequately dense (%theoretical density > 99%), showed negligible linear dimensional changes (indicating net-dimension formation capability), presence of crystalline Si and SiC phases and duplex microstructure with complete preservation of fibrous architecture of plant bio-structure. The Si/SiC ceramic composite synthesized from coir fiber board gave room temperature 3-point flexural strength and Young's modulus values of 121 MPa and 276 GPa, respectively. Both the ceramic composites showed adequate oxidation resistance during heating at 1300 °C for 7 h in air.     

Biocompatible hyperbranched polyurethane/multi-walled carbon nanotube composites as shape memory materials

Multi-walled carbon nanotube (MWCNT)-based composites have been prepared by in situ technique using Mesua ferrea L. seed oil-based hyperbranched polyurethane (HBPU) as the matrix. The scanning electron microscope, transmission electron microscope and Fourier transform infrared spectroscopy analyses revealed good dispersion as well as interaction of MWCNT with the matrix. Remarkable recovery of shape to the extent of 98% was obtained after composite formation. More than 300% improvement in tensile strength was observed as compared to the pristine HBPU. Significant enhancement of thermal stability up to 275 °C was found even at low MWCNT loading (1 wt.%). Bacterial degradation of the composite films was tested using two strains of Pseudomonas aeruginosa, MTCC 7814 and MTCC 7815. The composites exhibited enhanced biodegradability as compared to the pristine polymer. The cytocompatibility test based on hemolysis of red blood cells showed that the material lacks cytotoxicity. The investigation indicates that the material has high potential as shape memory biomaterial.     

Effect of dynamic cross-linking on mixing torque behavior and tensile yield behavior of isotactic polypropylene (iPP) / ethylene-propylene diene rubber (EPDM) /nitrile rubber (NBR) elastomeric blends

The mixing torque behavior of ter blends of isotactic-polypropylene (iPP) with ethylene-propylene diene rubber (EPDM)/Nitrile rubber (NBR) was studied with the help of Rheometer using resole type phenolic resin as a cross-linking agents. Systematic changes with varying blend composition were observed in stress-strain behavior in the yield region viz., width of yield peak, work of yield, yield stress and yield strain. Analysis of yield stress data was made on the basis of various mathematical expressions of first power and two-thirds power laws of blend composition dependence and the porosity model. It led to consistent result from the expressions about the variation of stress concentration effect in both uncross-linked and cross-linked blend systems. With the aid of scanning electron microscopy (SEM) shapes and sizes of dispersed elastomer phase (EPDM / NBR) domains at varying blend compositions were studied.     

Properties of CO2 laser-welded butt joints of dissimilar magnesium alloys

The paper presents results of keyhole laser beam welding of dissimilar magnesium alloys that have been carried out with the CO₂ laser of maximum power of 2.5 kW. The workpieces of die-cast alloys AZ91 and AM50 with thicknesses of 4.5 mm have been butt-welded with helium used as a shielding gas. With the chosen flow rate of helium shielding and the focal position set on the metal surface the nearly parallel fusion zones boundaries were obtained. The analysis of microstructures of the joints, measurements of hardness distribution and the elemental distribution in the weld cross-sections permitted to find the changes due to heating in the fusion zones and recrystallization. The static tensile strength tests and the three point bending tests have allowed to determine the mechanical properties of the joints. The corrosion resistance tests performed by the electrochemical method on samples of as-cast materials and samples with the welds of similar and dissimilar alloys have not displayed the differences in the corrosion resistance. However, the microscopic observations of surfaces of welded samples have shown the influence of the joints on corrosion development.