Remarkably improved dehydrogenation of ZrCl4 doped NaAlH4 for hydrogen storage application

Thermal dehydrogenation kinetics of sodium alanate (NaAlH₄) has been studied with respect to ZrCl₄ additive, and the results were compared with pure NaAlH₄. The FTIR analysis has shown insignificant effects of ZrCl₄ on the structural integrity of AlH₄^? anion after ball milling. Partial reduction of ZrCl₄ has been observed during ball milling with NaAlH₄. The in-situ reduction favors to homogeneous and adherent dropping of ZrCl₄ over the NaAlH₄ surface which leads to remarkably improved dehydrogenation process. The dehydrogenation of ZrCl₄ doped NaAlH₄ occurred in three steps similar to pure NaAlH₄. The dehydrogenation temperatures of all the steps were substantially decreased as compared to pure NaAlH₄. The apparent activation energy of dehydrogenation of ZrCl₄ doped NaAlH₄ was evaluated for all the dehydrogenation steps and found to be significantly less with respect to pure NaAlH₄.     

Analysis of thermal radiation,Joule heating,and viscous dissipation effects on blood-gold couple stress nanofluid flow driven by electroosmosis

Gold nanoparticles associated with DNA, RNA, proteins, oligonucleotides, and peptides are useful in therapies and drug delivery. The present article mainatins that gold nanoparticles play a tremendous role in remedying cancer and fatal diseases. A mathematical model is proposed for the two-dimensional motion of the couple stress nanofluid consisting of gold nanoparticles under the application of peristaltic propulsion and electroosmosis mechanisms in an asymmetric microchannel. The effects of radiation with slip boundary have been employed. The governing equations are simplified under the assumptions of low Reynolds number and long wavelength and the Poisson-Boltzmann equation is solved under Debye–Hückel linearization. Analytical solutions for the velocity of fluid motion, nanoparticle temperature, stream function, pressure gradient, are evaluated and analyzed graphically under the effects of various physical parameters. It is notable from the analysis that raising the Brinkman number boosts the nanoparticle temperature and heat transfer coefficient which validate the physical model and analysis. Moreover, it is noticed that sphere-shaped gold nanoparticles enhance the temperature as compared to other geometries of nanoparticles. The present study results may assist in developing the technology, smart micropumps, drugs, and device for hemodialysis and other health care applications.     

Eggshell derived mesoporous biphasic calcium phosphate for biomedical applications using rapid thermal processing

Biphasic calcium phosphate (BCP) has received much interest for making various bone substitutes since its physicochemical properties can be easily tailored by tuning its phase composition. Due to high temperature processing, it is hard to prepare BCP with nanoscale characteristics. In the present study, we have made an attempt to optimize the heat treatment parameters for the synthesis of BCP with nanoscale characteristics from eggshell derived hydroxyapatite (HA) through rapid thermal processing (RTP). To accomplish this, eggshell derived HA was prepared by wet precipitation method and subjected to RTP at 750°C and 1150°C for 3 and 10 minutes. For comparison we have also studied conventional calcination at 750°C and 1150°C for 3 hours. XRD, FTIR, SEM, EDX, HRTEM, and BET analyses were used to understand the effect of RTP and conventional calcination on eggshell derived HA. Our results indicate that eggshell derived HA on RTP at 1150°C for 3 minutes and 10 minutes can offer nanoscale BCP with good dissolution, bioactivity, cytocompatibility, and mesoporous nature. Hence, RTP can be a potential method to prepare BCP with nanoscale features for biomedical applications.     

Embrittlement of a Duplex Stainless Steel in Acidic Environment Under Applied Cathodic Potentials

Hydrogen-induced degradation of mechanical properties of a duplex stainless steel in 0.1N H₂SO₄ solution has been studied under in situ cathodic charging conditions. Significant reductions in percentage of elongation, toughness, and time to failure were noticed due to the ingress of hydrogen into the material at various applied cathodic potentials in the range of −200 to −800 mV (SCE). Cleavage fractures were identified mainly in the ferritic phases. Crack growth was observed to be inhibited by the austenite phase. However, depending on the severity of the environment, both the ferrite and austenite phases could be embrittled. At less negative potentials, presence of surface film and low hydrogen fugacity seemed to control hydrogen ingress in the metal. Addition of thiosulfate to the acidic solution further degraded the mechanical properties of the steel at the applied cathodic potential.     

Effect of wall temperature modulation on the heat transfer characteristics of droplet-train flow inside a rectangular microchannel

The numerical studies of water–oil two-phase slug flow inside a two-dimensional vertical microchannel subjected to modulated wall temperature boundary conditions have been discussed in the present paper. Many researchers have contributed their efforts in exploring the characteristics of Taylor flows inside microchannel under constant wall heat flux or isothermal wall conditions. However, there is no study available in the literature which discusses the impact of modulated thermal wall boundary conditions on the heat transfer behavior of slug flows inside microchannels. Hence, to bridge this gap, an effort has been made to understand the heat transfer characteristics of the flow under sinusoidal wall temperature conditions. Initially, a single phase flow and heat transfer study was performed in microchannels, and the results of the fully developed velocity profile and heat transfer rate were validated with benchmark analytical results. Then an optimal selection of the combination of sinusoidal thermal wall boundary conditions has been made for the two-phase slug flow study. Later, the effects of amplitude(0 b ε b 0.03) and frequency(0 b ω b 750π rad·s~(-1)) of the sinusoidal wall temperature profile on the heat transfer have been studied using the optimal combination of the wall boundary conditions. The results of the numerical study using modulated temperature conditions on channel walls showed a significant improvement in the heat transfer over liquid-only flow by approximately 50% as well as over two-phase flow without wall temperature modulation. The non-dimensional temperature contours obtained for different cases of temperature modulation clearly explain the root cause of such improvement in the heat transfer. Besides,the results based on the hydrodynamics of the flow have also been reported in terms of variation of droplet shapes and film thickness. The influence of Capillary number on the film thickness as well as heat transfer rates has also been discussed. In addition, the measured film thickness has also been compared with that calculated using standard empirical and analytical models available in the literature. The heat transfer rate obtained from the numerical study for the case of unmodulated wall temperature was found to be in a close match with a phenomenological model to evaluate slug flow heat transfer having a mean absolute deviation of 7.56%.     

Role of additives in the matrix of solvent encapsulated beads on its yttrium sorption from aqueous streams

Polyethersulfone (PES)-based beads encapsulating organic extractant PC88A and additives have been prepared, characterized and evaluated for yttrium sorption from aqueous chloride medium. The role of additives on modifying the morphological structure of the beads resulting in varying degrees of sorption has been examined. Amongst the various additives investigated, polyvinyl alcohol (PVA) led to significantly enhanced sorption of yttrium. The sorption data were analyzed by different isotherms. The mechanism of sorption was found to proceed via intraparticle diffusion as well as film diffusion following pseudo-second-order kinetics and chemisorption. The polymeric beads were found to be highly stable toward repeated numbers of sorption and desorption of yttrium.     

Accelerated Corrosion of a Boiler Chimney: Causes and Preventive Steps

Heavy corrosion attack was observed on the SS 304 liner used on the upper part of a mild steel chimney stack in a boiler. The corrosion had taken place due to the condensation of acidic flue gases. The corrosion damage in the liner material was even higher at locations, where a ladder was attached to the chimney body. Heavy thinning of the mild steel chimney body at such locations had also taken place from the inside, i.e., the inner surface exposed to the flue gas atmosphere. The chemical analysis of the corrosion deposits and condensates confirmed the presence of highly acidic environment (pH 2) consisting of mostly sulfate ions. Remedial measures to prevent future occurrence of the problem are also addressed.     

Nanoporous Silicon Microcavity Based Fuel Adulteration Sensor

Fuel adulteration is a very common practice in several countries around the world. This paper reports the use of porous silicon as a sensor for the detection of adulteration of petrol and diesel by kerosene. Porous silicon has some very useful properties such as high sensitivity, small size, high surface-to-volume ratio, bio-compatibility and compatibility with silicon IC technology which make it suitable for sensing purposes. The main objective of this work is to develop an optical sensor to detect the level of adulteration in a fuel sample using a porous silicon microcavity (PSMC). Reflectance measurements are used to detect the concentration of kerosene, which is the most commonly used adulterant for petrol and diesel, in the fuel sample. The core principle on which the sensing is based is that a change in the effective refractive index of the microstructure due to the introduction of the fuel in the pores leads to a change in the reflectance spectrum of the structure. The same sensor is used for the detection of adulteration in petrol as well as in diesel. The sensing process is reversible, thus making the sensor reusable.     

Real-time holographic backlighting positioning sensor for enhanced power coupling efficiency into selective launches in multimode fiber

This paper presents a qualitative, real-time backlighting positioning sensor for the alignment of an optical beam to a minutely deviated diffraction order axis to increase the power coupling efficiency into a multimode fiber in selective launches. Results show that the technique facilitates the alignment of the lenses to the first diffraction order axis and improves the power coupling efficiency into a multimode fiber.     

Porous alumina templates and nanostructured CdS for thin film solar cell applications

Nanostructured CdS was grown by electrodeposition of cadmium sulfide inside a porous alumina template. Uniform pore size and spacing in the template was achieved when the starting material for the template was aluminum foil. Typical pore size was 45 nm. Nanostructured CdS was also deposited by electrodeposition on indium tin oxide (ITO)-coated glass and by solution growth on ITO-coated glass. Schottky diodes were formed on nanocrystalline CdS and the analysis of their current–voltage characteristics yielded a diode ideality factor (n) of 2.6 and a reverse saturation current density (J_S) of 1.00×10⁻⁵ A/cm². Corresponding values for the Schottky diode on polycrystalline CdS were 3.4 and 1.93×10⁻⁶ A/cm².