Interaction of metal ions with clays: I. A case study with Pb(II)

Pb(II) adsorption was studied under different conditions (pH, time, metal ion concentration, clay amount, temperature) on kaolinite, montmorillonite, and their poly(hydroxo)zirconium (ZrO–kaolinite, ZrO–montmorillonite) and tetrabutylammonium (TBA–kaolinite, TBA–montmorillonite) derivatives. All samples were calcined (ZrO-derivatives at 773 K, TBA-derivatives at 973 K) before using as adsorbents. The data were interpreted assuming first- and second-order kinetics. The rate constants including the pore diffusion rate constant are reported. The adsorption data could be fitted with Freundlich and Langmuir isotherms, and the coefficients indicated favorable adsorption of Pb(II) on the clays. Determination of the thermodynamic parameters, ΔH, ΔS, and ΔG showed the adsorption to be exothermic accompanied by decrease in entropy and Gibbs energy.     

Induction Plasma Sprayed Nano Hydroxyapatite Coatings on Titanium for Orthopaedic and Dental Implants

This paper reports preparation of a highly crystalline nano hydroxyapatite (HA) coating on commercially pure titanium (Cp-Ti) using inductively coupled radio frequency (RF) plasma spray and their in vitro and in vivo biological response. HA coatings were prepared on Ti using normal and supersonic plasma nozzles at different plate powers and working distances. X-ray diffraction (XRD) and Fourier transformed infrared spectroscopic (FTIR) analysis show that the normal plasma nozzle lead to increased phase decomposition, high amorphous calcium phosphate (ACP) phase formation, and severe dehydroxylation of HA. In contrast, coatings prepared using supersonic nozzle retained the crystallinity and phase purity of HA due to relatively short exposure time of HA particles in the plasma. In addition, these coatings exhibited a microstructure that varied from porous and glassy structure at the coating-substrate interface to dense HA at the top surface. The microstructural analysis showed that the coating was made of multigrain HA particles of ~200 nm in size, which consisted of recrystallized HA grains in the size range of 15- 20 nm. Apart from the type of nozzle, working distance was also found to have a strong influence on the HA phase decomposition, while plate power had little influence. Depending on the plasma processing conditions, a coating thickness between 300 and 400 μm was achieved where the adhesive bond strengths were found to be between 4.8 MPa to 24 MPa. The cytotoxicity of HA coatings was examined by culturing human fetal osteoblast cells (hFOB) on coated surfaces. In vivo studies, using the cortical defect model in rat femur, evaluated the histological response of the HA coatings prepared with supersonic nozzle. After 2 weeks of implantation, osteoid formation was evident on the HA coated implant surface, which could indicate early implant- tissue integration in vivo.     

A review of the causes of bullwhip effect in a supply chain

A review of the past research studies on the causes of bullwhip effect is presented in this paper. This paper is an effective study from the point of view that it presents a detailed classified study of the overall research studies on the effect of both the operational and the behavioral factors on bullwhip effect. A total of 19 causes of bullwhip effect have been shown here. We have identified the various gaps of research in the past research studies. An overview of the steps taken by the industries in order to tackle the bullwhip effect is also provided at the end of this paper. Directions for further research studies are also provided in each subsection of this study and at the end of this paper.     

A novel sol–gel synthesis of mesoporous ZrO2–MoO3/WO3 mixed oxides

Mesoporous ZrO₂–MoO₃/WO₃ mixed oxides have been synthesized through a novel, convenient one step sol–gel technique. Water soluble molybdate/tungstate and zirconium (IV) carbonate complex have been employed in presence of cationic surfactant, tetradecyltrimethylammonium bromide under basic condition. The synthesized materials have shown high specific surface areas and narrow pore-size distributions which were achieved after optimization of the amount of surfactant. Mesoporous ZrO₂–MoO₃ and ZrO₂–WO₃ mixed oxides have shown specific surface areas of 228 and 275 m² g⁻¹ and pore sizes of 3.65 nm and 4.33 nm, respectively. FTIR and Raman studies prove the formation of hetero bonding in mixed oxides.     

Field-dependent spin waves in high-aspect-ratio single-crystal ferromagnetic nanowires

We investigate the spin wave (SW) modes in high-aspect-ratio single-crystal ferromagnetic nanowires (FMNWs) using an all-optical time-resolved magnetooptical Kerr effect (TR-MOKE) microscope. The precessional magnetization dynamics in such FMNWs unveil the presence of uniform and quantized SW modes that can be tuned by varying the bias magnetic field (H). The frequencies of the modes are observed to decrease systematically with a decreasing magnetic field, and the number of modes in the spectrum is reduced from four to three for H < 0.7 kOe. To understand these results, we perform micromagnetic simulations that reveal the presence of edge, standing wave, and uniform SW modes in the nanowires (NWs). Our simulations clearly show how the standing wave and uniform SW modes coalesce to form a single mode with uniform precession over the entire NW for H < 0.7 kOe, reproducing the experimentally observed reduction in modes. Our study elucidates the possibility of manipulating the SW modes in magnetic nanostructures, which is useful for applications in magnonic and spintronic devices.

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Synthesis, Processing, Mechanical, and Biological Property Characterization of Hydroxyapatite Whisker-Reinforced Hydroxyapatite Composites

Effects of hydroxyapatite (HA) whiskers addition on densification, mechanical, and biological properties of HA compacts were studied for their use as an implant material for orthopedic and dental applications. HA nanopowder was synthesized using reverse micelle as template system, and urea hydrolysis synthesis route was used to prepare micrometer-sized HA whiskers. Poly (oxyethylene)₁₂ nonylphenol ether (NP12) and cyclohexane were used as surfactant and organic solvent, respectively, for the reverse micelle microemulsion system. Desired microstructure in sintered HA composite was obtained by mixing Mg²⁺ as a dopant in HA nanopowders, and Al³⁺ as a dopant in HA whiskers. Compacts were processed using pressureless sintering. With an increase in whisker content from 0 to 10 wt%, the average compressive strength of HA compacts decreased from 120 to 90 MPa. HA composite processed with 10 wt% HA whisker showed a microhardness of 3.6 GPa and an average indentation fracture toughness of 1.5 MPa·m^1/2. Mineralization study in simulated body fluid showed deposition of octacalcium phosphate on sintered HA compacts. In vitro cytotoxicity tests with human osteoprecursor cell line confirmed excellent osteoblast cell attachment and growth on the sintered HA compacts with 0, 10, and 20 wt% HA whiskers.