Amount Of Al2O3 Nanoparticles Research Articles

Numerical investigation of falling film generation outside vertical tube with ammonia-water nanofluid

This paper constructed a mathematical model of ammonia-water nanofluid falling film generation outside the vertical tube, which considers the change of the film thickness of the falling film solution, the thermal convection along the film thickness direction and the physical properties of the solution. By solving the mathematical model, the temperature field and other elements of the liquid film were determined. The influence of the properties of the working fluid on the heat and mass transfer in the falling film process is investigated. According to the calculation results, a method of adding nanoparticles in the process of ammonia falling film generation is proposed. The simulation results showed that the heat efficiency of entire falling film process can be enhanced by adding an appropriate amount of Al2O3 nanoparticles. When the added Al2O3 nanoparticles are 1 vol.%, the coefficient of the heat transfer is increased by about 4%, and the mass transfer effect is also improved by about 12%. In brief, the establishment of this model aims to improve heat and mass transfer efficiency and promote the application and integration of low-grade waste heat or renewable energy technologies in built environment.

The Electro-optical study of Al2O3 nanoparticles doped polymer dispersed liquid crystal films

ABSTRACT The electro-optical characteristics of nanoparticles-doped polymer dispersed liquid crystals (PDLCs) have been investigated for display applications. The PDLC samples were obtained by polymerisation induced phase separation of the nematic liquid crystal LC-nanoparticles-prepolymer mixtures under UV illumination with a constant intensity. The effect of Al2O3 nanoparticles doping on the PDLC system was studied. It was seen that the electro-optical characteristics of PDLC were dependent on the amount of Al2O3 nanoparticles used. The effect of morphology on the electro-optical properties was examined, and the experimental results indicated that the driving voltage was affected considerably by the amount of Al2O3 nanoparticles. The results showed that the nanoparticles concentration can be optimised to obtain promising electronic materials with a minimum threshold for display applications.

Machining performance of Inconel-718 alloy under the influence of nanoparticles based minimum quantity lubrication grinding

Abstract Environmental and health problems associated with the conventional mineral-based cutting fluids has enhanced the quest of researchers to search for environment-friendly lubrication techniques. Minimum Quantity Lubrication (MQL) is the latest technique developing to reduce the use of coolants in machining. In the present work grinding of Inconel-718 (Ni-Cr alloy) has been examined under the influence of Al2O3 based Nanofluid Minimum Quantity Lubrication (NFMQL) technique using vegetable oils as the base oils in view of environmental conscious grinding. The grinding performance of Inconel-718 was evaluated in terms of surface roughness, grinding energy, cutting forces, temperature, and G-ratio. Nanofluids were prepared by adding 0.5 wt% and 1 wt% Al2O3 nanoparticles to the sunflower and rice-bran vegetable oils. From the results, it is observed that Al2O3 based nanofluid MQL with sunflower as base oil has given better results with respect to G-ratio, grinding energy, surface roughness, and coefficient of friction. Better value of surface roughness (0.5 μm) is achieved with 0.5 wt% concentration of nano-particles, whereas G-ratio (1.52), grinding energy(32.91 J/mm3) and tangential forces improved under nanofluid MQL condition with 1 wt% concentration of nanoparticles as compared to flood cooling. This might be due to the fact that while nanofluids flow through the wheel-workpiece interface, it results in the formation of a lubrication film that acts as ball bearing and reduces the sliding friction. Thus vegetable oils with the appropriate amount of Al2O3 nano-particles can give sufficient tribological properties with the environment and economic advantages.

Enhanced Thermal Resistance and Electrochemical Performance of the Trilayered PP/PE/PP Separators Using Alumina Coating for Lithium-Ion Batteries

Lithium-ion batteries (LIBs) have served as a potential power source for portable electric vehicles and energy storage devices due to their high energy capability, high power density, cost competitiveness, long cycle life and little memory effect. However, safety issue is still one of the most challenges in affecting widespread use of LIBs as power sources. As a key component of LIBs, the separator should maintain electronic insulation between cathode and anode, enabling free ionic transport and isolating electronic flow. To reach the demand of safety issue, the design of separator takes one task that is responsible for preventing an internal short circuit from thermal evolution. An ideal separator is therefore expected to possess high ionic conductivity, excellent thermal stability, and superior electrochemical performance. One strategy to improve the thermal stability and electrolyte wettability on the separators is introducing ceramic coating layers containing hydrophilic inorganic powders such as ZrO2, SiO2, TiO2, and Al2O3. The above achievements direct us at the development of facile methods to improve the polymeric separators to meet the requirements of high-performance LIBs. Recently, polymeric membranes such as the tri-layered PP/PE/PP have been extensively used as separators for LIB applications. This work work adopts a chemical-wet impregnation method to prepare alumina-coated separator, using commercial Al2O3 nanoparticles and poly(vinylidene fluoride-hexafluoropropylene) (PVdF-HFP) binder. The PVdF-HFP binder contains a ternary mixture comprising the polymer (PVdF-HFP), solvent (acetone), and nonsolvent (water), which is appropriate to mix with ceramic nanoparticles. One potential electrode material, spinel Li4Ti5O12, is served as the anode for the analysis of electrochemical performance, using charge-discharge cycling and electrochemical impedance spectroscopy. Three densities of Al2O3 nanoparticles are uniformly dispersed and coated onto the surface of tri-layered polymeric separators. The bare and Al2O3-coated separators were denoted to U, AS1, AS2, and AS3 according to the weight ratio of Al2O3 to PVdF-HFP solution of 0, 0.06, 0.12, and 0.25 wt.%, respectively. TGA curves reflect that the thermal resistance of tri-layered separators is significantly enhanced after the deposition of Al2O3 coating layers. The alumina deposits display high thermal resistive ability under O2-containing atmosphere. Moreover, FE-SEM images show that the alumina nanoparticles with an average particle size of 300 nm are uniformly dispersed on the surface of the separators. With increasing alumina loading, close-packed Al2O3 nanoparticles interconnected by PVdF-HFP binder are grouped and coated upon the surface of the separators. Typical XRD patterns reveal that bare separator (U) possesses its original reflection bands, while alumina-coated separators (AS1, AS2, and AS3) exhibit additional representative bends, confirming the presence of α-Al2O3 crystals. On the other hand, the mass uptake of the electrolyte (1.0 M LiPF6 in a mixture of ethylene carbonate, propylene carbonate, and dimethyl carbonate with a weight ratio of 1:1:1) on the bare separator (U) is 270 mg cm-2, whereas that on AS1 separator attains as high as 515 mg cm-2. Also, the mass uptake on AS3 separator is 2.2 times higher than that of the bare one. The extent of thermal shrinkage on AS3 sample is ~2.26 times higher than that on U sample. This confirms that an obvious enhancement on thermal stability of polymeric polymer can achieve after the introduction of alumina coating, also demonstrated by the TGA results. With regard to electrochemical performance, the LIB using AS3 separator delivers the highest discharge capacity among these samples, i.e., 166 mAh g-1 (0.1C) and 160 mAh g-1 (1C). The enhanced rate capability is presumably due to high Li-ion storage capacity and excellent wettability, imparting low Li-ion diffusion resistance and then speeding up electronic conduction. With the aid of Al2O3 coating layer, the equivalent series resistance of electrode is significantly reduced and the ionic conductivity is strongly improved, according to analysis of ac impedance spectroscopy. In a word, the amount of Al2O3 nanoparticles is picked up as a key parameter in examining electrochemical performance and thermal stability of LIBs. The enhanced performance is ascribed to the fact that Al2O3 coating layer is served as a robust skeleton to stabilize the separators, imparting a superior insulation and mass transport barrier against volatile compounds formed during the thermal decomposition process.

Use of Al2O3/Nafion Membranes for Room-Temperature Sodium-Sulfur (Na-S) Batteries

In recent years, Lithium-Sulfur (Li-S) batteries have attracted much attention due to their high theoretical capacity (1675 mAh/g), environmental benignancy, abundancy and cost-effectivity of sulfur. However, due to the increase in the price of lithium, an alternative material to be used as anode is highly needed. Sodium is a promising candidate because of its natural abundancy and low cost. Thus, conventional Sodium-sulfur (Na-S) batteries were already demonstrated which operates at high temperatures (>300 °C) bringing safety problems because of the molten state of electrodes at high temperature range. Park et al recently showed that Na-S batteries could be used at room-temperatures1. As expected, room temperature Na-S batteries have the same problems as of Li-S batteries; insulating nature of sulfur, dissolution of polysulfide species formed upon discharging of the battery, shuttle effect of these polysulfide species, huge volume change during the formation of the end of discharge product, Na2S, and dendrite formation on sodium anode. These issues result in rapid capacity fading of the battery and limit their usage in practice. To mitigate these drawbacks, encapsulating sulfur into meso-/micro-porous structures were suggested2-4. However, the leakage of polysulfide species from the porous matrixes is inevitable, thus recent studies of the room-temperature Na-S batteries mostly focus on the development of protective barrier between anode and cathode electrodes to prevent polysulfide migration 5-11. To do so, ß-alumina5,6 was firstly employed as polysulfide barrier followed by nafion dispersion7, carbon nanotubes or carbon fibers 8,9,10,11. Herein, in order to prevent the poisoning of sodium anode from the dissolved polysulfides, we developed Al2O3/Nafion membranes12. Nafion has an ability of cation selectivity and anion nonpermeability which play perfect roles on preventing migration of polysulfides towards anode side. On the other hand, Al2O3, is an electrochemically inactive material, has porous structure which provides lots of channels to pass Na+ ions and it can absorb polysulfides13. By combining their constructive properties, enhancement of the battery performance was aimed. Within this context, porous separator were coated by Nafion solutions together with different amount of Al2O3nanoparticles by using a serigraphy (silk screen) printing machine. Nice uniform coating of the protective barriers were obtained which were confirmed by microstructural analysis. Electrochemical cycling performances of those membranes resulted better capacity retention and stability in comparison with the bare separator. Moreover, shuttle effect of the Na-S cells were highly eliminated resulting higher Coulombic efficiencies. ACKNOWLEDGEMENTS This work is partially supported by National Young Researchers Career Development Grant of TUBITAK (contract no: 213M374). REFERENCES [1] C. W. Park, J. H. Ahn, H. S. Ryu, K. W. Kim, H. J. Ahn, Electrochem. Solid St. 2006, 9, A123. [2] D. J. Lee, J. W. Park, I. Hasa, Y. K. Sun, B. Scrosati, J. Hassoun, J. Mater. Chem. A 2013, 1, 5256. [3] T. H. Hwang, D. S. Jung, J. S. Kim, B. G. Kim, J. W. Choi, Nano Lett. 2013, 13, 4532. [4] S. Xin, Y. X. Yin, Y. G. Guo, L. J. Wan, Adv. Mater. 2014, 26, 1261. [5] S. Wenzel, H. Metelmann, C. Raiss, A. K. Durr, J. Janek, P. Adelhelm, J. Power Sources 2013, 243, 758. [6] I. Kim, J.Y. Park, C.H. Kim, J.W. Park, J.P. Ahn, J.-H. Ahn, K.W. Kim, H.J. Ahn, J. Power Sources, 2016, 301, 332-337. [7]I. Bauer, M. Kohl, H. Althues, S. Kaskel, Chem. Commun. 2014, 50, 3208. [8]X. W. Yu, A. Manthiram, J. Phys. Chem. Lett. 2014, 5, 1943. [9]X. W. Yu, A. Manthiram, ChemElectroChem 2014, 1, 1275. [10] X. W. Yu., A. Manthiram, J. Phys. Chem. C 2014, 118, 22952. [11]X. W. Yu., A. Manthiram, Adv. Energy Mater. 2015, 1500350. [12] E.C. Cengiz, Z. Erdol, A. Aslan, A. Ata, R. Demir-Cakan, 2015, manuscript in preparation. [13] X.Y. Liu, Z.Q. Shan, K.L. Zhu, J.Y. Du, Q.W. Tang, J.H. Tian, J. Power Sources, 2015, 274 85–93

Experimental Investigation on Influence of Nano Fluids in Drilling of Al 6061 Alloy using Grey Based- Taguchi Approach

Drilling, a hole making process is especially important because it accounts for a large portion of overall machining operations. Amongst all machining operations, drilling using twist drill is most commonly applied method for generating holes for riveting and fastening of structural assemblies.This paper deals with multi performance characteristics in drilling of Aluminum 6061 alloy with water based Nano fluid (small amount of Al2O3 Nano particles in water) using Grey based – Taguchi method. Five parameters namely cutting speed, feed rate, point angle, clearance angle and variable volume fraction of Al2O3 Nanoparticles in water were identified and their ranges for the present investigation were determined from preliminary experiments. Thrust force and surface roughness are recorded using well calibrated equipments at 3 levels with L27 orthogonal array as per Taguchi experimental plan. Optimal combination of process parameters was obtained to minimize the recorded responses. In the case where experiments are ambiguous or when the experimental method cannot be carried out exactly, grey analysis helps to compensate for the shortcoming in statistical regression. Grey based – Taguchi method is an effective tool for analyzing the relationship between sequences with less data and can analyze many factors that can overcome the disadvantages of statistical method. Most of manufacturing industries perform a huge number of drilling operations in machine shops. The drilling technology has been studied to improve the cutting performance with optimizing the cutting parameters and the tool geometry. Some researchers have developed mathematical models of drilling to estimate thrust and torque. Williams [1] showed that during cutting there are three identifiable zones of interest at the drill point, the main cutting edges, the secondary cutting edges at the chisel edge and an indentation zone about the drill center. Zhang et al. model was based on mechanics of vibration and the continuous distribution of thrust and torque along the lip and the chisel edge of the twist drill [2]. The mean thrust and torque increased as feed increases under constant vibration parameters [3–4]. They concluded that vibration drilling is different from conventional drilling and it is a dynamic cutting process. Another model was presented for drilling processes by Yang et al. [5]. A statistical analysis of hole quality was performed by Furness et al. [12]. They found that feed and speed have a relatively small effect on the measured hole quality features. With the expectation of hole location error, the hole quality is not predictably or significantly affected by the cutting conditions. Although the authors did not expect these results, they have the important positive implication that production rates may be increased without sacrificing hole quality. Rincon and Ulsoy[15] showed that the changes in the relative motion of the drill do affect the variations of the forces. An increase in the ranges of drill motion results in an increase in the ranges of torque and thrust. The 6061 alloy of aluminum is primarily composed of magnesium and silicon. Some other elements of 6061 aluminum alloy include small amounts of iron, copper, manganese,

Preparation and characterisation of electrodeposited Ni-Cr/Al<SUB align="right">2O<SUB align="right">3 nanocomposite coatings from a trivalent chromium-based bath

Ni-Cr/Al2O3 composite coatings were co-deposited on mild steel substrates by co-electrodeposition of Ni-Cr alloys and Al2O3 nanopowders from a trivalent chromium plating bath. Variations of Cr and Al2O3 nanoparticles in nanocomposite coatings as a function of Al2O3 concentration in electrolyte, cathode current density, stirring rate and temperature of plating bath was investigated. It was found that these parameters strongly affect the weight percentage of Cr and Al2O3 nanoparticles in the coatings. Microstructural characterisation of the coatings was performed by x-ray diffraction (XRD), scanning electron microscopy and energy-dispersive x-ray analysis (EDX). The corrosion behaviour of the nanocomposite coatings was evaluated by charting the Tafel curves of the solution of H2SO4 (5%) at room temperature. The results showed that the amount of Al2O3 nanoparticles in the coating increases with increasing Al2O3 concentration in electrolyte. This also enhances the co-deposition of Ni and Cr. It was also found that the presence of Al2O3 nanoparticles leads to an increase in hardness and corrosion resistance of the coatings. The distribution of Al2O3 nano-particles across the coatings was uniform even in those cases which resulted from baths of higher concentrations of Al2O3.

Electrical conductivity and dielectric behaviour of PPG4–AgCF3SO3:Al2O3 nanocomposite gel polymer electrolyte system

In this report, the synthesis of solvent-free poly(propylene glycol) 4000 (PPG4)–silver triflate (AgCF3SO3):xAl2O3 nanocomposite gel polymer electrolytes containing four different amounts of Al2O3 nanoparticles corresponding to x = 1, 3, 5 and 7 wt.%, respectively, with an ether oxygen-to-metal cation ratio (O–M) of 4:1 together with their vibrational spectroscopic characteristics derived from Fourier transform infrared (FT-IR ) spectroscopic analysis at room temperature (25 °C) is described. Furthermore, a detailed investigation concerning their mechanism of ion transport performed by means of complex impedance analysis in the frequency range 20 Hz to 1 MHz and over the temperature region 25–90 °C and analysed in terms of electrical conductivity spectra, electrical modulus spectra and impedance spectra has indicated that the typical composition PPG4–AgCF3SO3:5 wt.% Al2O3 would exhibit the best room temperature electrical conductivity of 6.2 × 10−4 S cm−1 owing to the mobility of coordinated silver cations through the mechanism of enhanced segmental motion of the PPG4 polymer chains as aided by the various coordinating sites available within the polymer network. It is also demonstrated from the present FT-IR results that significant changes in the intensity, shape and position of the different vibrational bands corresponding to –OH stretching, C–O–C stretching, C–H stretching and C–O–C in C–H stretching modes occur as a result of the incorporation of Al2O3 nanofiller particles into the PPG4–AgCF3SO3 complex. It is evident from the conductivity data that the observed enhancement in electrical conductivity would result from appropriate changes in ionic association occurring in the form of probable ion–ion and ion–polymer interactions involving Al2O3 nanofiller additive in accordance with the Lewis acid–base model of polymer–salt–filler interactions.