Molten salt attack on t′ yttria-stabilised zirconia by dissolution and precipitation

Degradation due to molten salt attack is one of the failure mechanisms of thermal barrier coatings. Thermochemical attack of the salt mixture Na₂SO₄–30 mol% NaVO₃ on ZrO₂–8 mol% YO_1.5 (8YSZ) at 950 °C was studied by two types of experiments. Sintered compacts were exposed to 25 mg cm^?2 salt dosage for up to 96 h. In the other set of experiments, 10–35 wt.% 8YSZ powder was mixed with the salts to study the dissolution of 8YSZ in the molten salt. The role of volatile losses was also examined. The results show that more than 25 wt.% 8YSZ dissolves in the sulphate-vanadate melt at 950 °C, followed by slow reactions to form YVO₄ and NaYV₂O₇ at 950 °C. The unreacted Y₂O₃ and monoclinic ZrO₂ precipitate out separately during rapid cooling (～300 °C/min). Slow cooling at ～3 °C/min leads to the formation of ZrOS apart from ZrO₂ and Y₂O₃.     

Optimization of La2O3-containing diopside based glass-ceramic sealants for fuel cell applications

We report on the optimization of La₂O₃-containing diopside based glass-ceramics (GCs) for sealant applications in solid oxide fuel cells (SOFC). Seven glass compositions were prepared by modifying the parent glass composition, Ca_0.8Ba_0.1MgAl_0.1La_0.1Si_1.9O₆. First five glasses were prepared by the addition of different amounts of B₂O₃ in a systematic manner (i.e. 2, 5, 10, 15, 20 wt.%) to the parent glass composition while the remaining two glasses were derived by substituting SrO for BaO in the glasses containing 2 wt.% and 5 wt.% B₂O₃. Structural and thermal behavior of the glasses was investigated by infrared spectroscopy (FTIR), density measurements, dilatometry and differential thermal analysis (DTA). Liquid–liquid amorphous phase separation was observed in B₂O₃-containing glasses. Sintering and crystallization behavior, microstructure, and properties of the GCs were investigated under different heat treatment conditions (800 and 850 °C; 1–300 h). The GCs with ≥5 wt.% B₂O₃ showed an abnormal thermal expansion behavior above 600 °C. The chemical interaction behavior of the glasses with SOFC electrolyte and metallic interconnects, has been investigated in air atmosphere at SOFC operating temperature. Thermal shock resistance and gas-tightness of GC sealants in contact with 8YSZ was evaluated in air and water. The total electrical resistance of a model cell comprising Crofer 22 APU and 8YSZ plates joined by a GC sealant has been examined by the impedance spectroscopy. Good matching of thermal expansion coefficients (CTE) and strong, but not reactive, adhesion to electrolyte and interconnect, in conjunction with a low level of electrical conductivity, indicate that the investigated GCs are suitable candidates for further experimentation as SOFC sealants.     

Novel Cu–carbon nanofiber composites for the counter electrodes of dye‐sensitized solar cells

Copper (Cu)‐catalyzed carbon nanofibers (CNFs) were used as an alternative of the conventional platinum‐noble‐metal‐based catalyst at the counter electrode (CE) of a dye‐sensitized solar cell (DSSC). The CNFs were grown on activated carbon microfiber powder (PACF) using chemical vapor deposition (CVD) and the Cu nanoparticles (NPs). The Cu NPs served simultaneous roles: (i) as the CVD catalyst for the growth of the CNFs; (ii) as an enhancer of the electrode conductivity; and (iii) as a catalyst for the reduction reaction. The Cu‐CNF composite was applied as a thin layer on the fluorine‐doped tin oxide glass using the simple doctor blade method. The prepared Cu‐NP‐dispersed PACF/CNF composite was characterized using various spectroscopic techniques, including scanning electron microscopy, Fourier transform infrared ray, X‐ray diffraction, Raman spectroscopy, and transmission electron microscopy. The electrochemical tests showed that the Cu‐PACF/CNFs had a high electrocatalytic activity and low charge transfer resistance (1.26 Ω cm²), using the cyclic voltammetry and electrochemical impedance spectroscopy measurements. The DSSC fabricated with Cu‐PACFs/CNFs exhibited a power conversion efficiency value of 4.36%, open circuit voltage of 0.75 V, short circuit current density of 11.12 mA cm^?2, and fill factor of 54%. The prepared transition metal–CNF composite was simple to develop and can potentially be used as an efficient catalyst at the CE of DSSCs. Copyright © 2014 John Wiley & Sons, Ltd.     

Validation and enhancement of waste cooking sunflower oil based biodiesel production by the trans-esterification process

This article predicts the optimum conditions for the production of fatty acid ethyl ester (Biodiesel) by trans-esterification process of waste cooking sunflower oil with ethanol in the presence of homogeneous catalyst (KOH). Response surface methodology (RSM) based on central composite rotatable design (CCRD) was used for predicting the mathematical regression equation and optimizing the biodiesel yield. The optimum reaction conditions were found to be 9.05 (mole mole^?1) of (ethanol to waste cooking sunflower oil ratio), 0.99 (wt% to oil) of catalyst concentration, 57.31°C of reaction temperature, 77.12 minutes of reaction time, and 494.94 rpm of mixing rate to achieve 96.33% biodiesel yield by weight. The production rate of produced biodiesel also increased significantly. The fuel properties were measured and found closer to the ASTM standards of biodiesel. Therefore, the suggested biofuel has good scope for use in compression ignition (CI) engines.     

Functionalization of track-etched poly (ethylene terephthalate) membranes as a selective filter for hydrogen purification

This paper reports on the carboxylic and amino group functionalization of track-etched poly(ethylene terephthalate) (PET) membranes with different pore size and pore density. Glycolic acid groups were formed by oxidation of hydroxyethyl end groups while amino groups were introduced by amidation of these carboxylic groups with tetraethylenepentamine. These membranes were characterized by gel permeation chromatography (GPC), nuclear magnetic resonance (NMR) and X-ray photoelectron spectroscopy (XPS) to follow the effect of the oxidation process on the molecular weight of the PET and to access the formation of functional groups. As concluded from NMR and XPS results, the density of carboxyl and amino group increases in comparison to pristine PET membranes. The larger the pore diameter and the pore density, the higher is the extent of functionalization. We demonstrate the deposition of palladium (Pd) nanoparticles onto pore walls and pore surfaces of PET membranes for potential use in hydrogen separation or sensing. Scanning electron microscopy (SEM), transmission electron microscopy (TEM), and energy dispersive x-ray spectroscopy (in SEM) results show presence of Pd nanoparticles in functionalized PET membranes pointing to an enhanced binding capability of Pd nanoparticles that can be used for hydrogen extraction from a mixture of gases.     

Isospora neorivolta SP. N. from the domestic dog

The endogenous development of canine Isospora rivolta (Mahrt, J Protozool 14: 754--759, 1967) was compared with the development of I. ohioensis (Dubey, Parasitology, 1978, In press) in intestines of dogs. A new name, Isospora neorivolta, is proposed for the canine I. rivolta because of developmental differences from I. ohioensis. The major difference between these 2 coccidia is their site of development. Isospora neorivolta develops predominantly in the lamina propria of the posterior half of the small intestine, whereas I. ohioensis develops only in the epithelium and infection occurs throughout the small intestine. Additional information on the development of I. neorivolta in dogs is given.     

Finite element analysis of non‐Newtonian magnetohemodynamic flow conveying nanoparticles through a stenosed coronary artery

The present study considers two‐dimensional mathematical modeling of non‐Newtonian nanofluid hemodynamics with heat and mass transfer in a stenosed coronary artery in the presence of a radial magnetic field. The second‐grade differential viscoelastic constitutive model is adopted for blood to mimic non‐Newtonian characteristics, and blood is considered to contain a homogenous suspension of nanoparticles. The Vogel model is employed to simulate the variation of blood viscosity as a function of temperature. The governing equations are an extension of the Navier‐Stokes equations with linear Boussinesq's approximation and Buongiorno's nanoscale model (which simulates both heat and mass transfer). The conservation equations are normalized by employing appropriate nondimensional variables. It is assumed that the maximum height of the stenosis is small in comparison with the radius of the artery, and, furthermore, that the radius of the artery and length of the stenotic region are of comparable magnitude. To study the influence of vessel geometry on blood flow and nanoparticle transport, variation in the design and size of the stenosis is considered in the domain. The transformed equations are solved numerically by means of the finite element method based on the variational approach and simulated using the FreeFEM++ code. A detailed grid‐independence study is included. Blood flow, heat, and mass transfer characteristics are examined for the effects of selected geometric, nanoscale, rheological, viscosity, and magnetic parameters, that is, stenotic diameter (d), viscoelastic parameter (), thermophoresis parameter (), Brownian motion parameter (), and magnetic body force parameter (M) at the throat of the stenosis and throughout the arterial domain. The velocity, temperature, and nanoparticle concentration fields are also visualized through instantaneous patterns of contours. An increase in magnetic and thermophoresis parameters is found to enhance the temperature, nanoparticle concentration, and skin‐friction coefficient. Increasing Brownian motion parameter is observed to accelerate the blood flow. Narrower stenosis significantly alters the temperature and nanoparticle distributions and magnitudes. The novelty of the study relates to the combination of geometric complexity, multiphysical nanoscale, and thermomagnetic behavior, and also the simultaneous presence of biorheological behavior (all of which arise in actual cardiovascular heat transfer phenomena) in a single work with extensive visualization of the flow, heat, and mass transfer characteristics. The simulations are relevant to the diffusion of nano‐drugs in magnet‐targeted treatment of stenosed arterial disease.     

Steady Conjugate Heat Transfer from X-Ray or Laser-Heated Sphere in External Flow at Low Reynolds Number

ABSTRACT

A laser or an X-ray beam is used to heat a sphere that is immersed in uniform external flow. Temperature distributions as well as local and average convective heat transfer coefficients are calculated in order to evaluate the efficacy of cooling the solid sphere. The present work extends previous studies by: (1) applying a unique heat source imposed by irradiating the sphere with an intense X-ray energy beam; (2) performing the conjugate heat transfer analysis in fluid and solid domain; and (3) calculating the internal and surface temperature distribution. Absorption of the irradiation results in nonuniform heat generation, having an exponential spatial distribution of heat source. The limiting cases of heat source distribution are localized surface “laser” heating and near-uniform heat generation throughout the sphere. Key results are reported for two different source beam sizes (small and large) striking the sphere, with comparison to the solution for the isothermal wall boundary condition.     

Biodiesel production from Nerium oleander (Thevetia peruviana) oil through conventional and ultrasonic irradiation methods

In the present research work, Nerium oleander oil has been used as raw material for producing biodiesel using both ultrasonic transesterification and a magnetic stirrer method. A two-step transesterification process was carried out for optimum condition of 0.40% V/V methanol to oil ratio, 1% V/V H₂SO₄ catalyst, 55°C temperature, and 60 min reaction time followed by treatment with 0.2% V/V methanol to oil ratio, 1% V/W KOH alkaline catalyst, 55°C temperature, and 60 min reaction time. The process is repeated with an ultrasonic method at the frequency of 28 kHz using ultrasonic horn type reactor (50 W) for about 10–15 min. Biodiesel obtained from ultrasonic method and magnetic stirrer was then compared for their percentage yield and physiochemical properties. Ultrasonic transesterification process gave a maximum yield of 97% by weight of oleander biodiesel along with improved physiochemical characteristics. Therefore, it is concluded that ultrasonic method is the most effective method for converting crude oleander oil into biodiesel.