Dispersed Alumina Research Articles

Effect of test atmosphere composition on high-temperature oxidation behaviour of CoNiCrAlY coatings produced from conventional and ODS powders

The oxidation behaviour of free-standing CoNiCrAlY coatings produced by low-pressure plasma spraying using conventional powder and oxide dispersion strengthened (ODS) powder containing 2 wt. % Al-oxide dispersion was investigated. Thermogravimetric experiments at 1100 °C in Ar-20%O2 and Ar-4%H2-2%H2O showed lower oxidation rates of the ODS than the conventional coating. In the latter material the scale growth was enhanced by extensive Y-incorporation of Y/Al-mixed oxide precipitates in the scale and apparently by Y-segregation to oxide grain boundaries. In the ODS coating the alumina dispersion bonded Y in the form of Y-aluminate thereby effectively suppressing scale ‘overdoping’. SEM/EBSD studies of all alumina scales revealed a columnar grain structure with the lateral grain size increasing approximately linearly with depth from the oxide/gas interface. For both coatings the alumina scale growth was slower in Ar–H2–H2O than in Ar–O2. The result is believed to be related to a lower oxygen potential gradient and to slower grain boundary diffusion in the scale forming in H2/H2O containing gas.

Relationship between Ionic Interation and NMR Relaxation Behavior in LiClO4-PC Solution Coexisting with Fumed Metal Oxide

Lithium ion battery (LIBs) is indispensable to various electrochemical devices in practical use such as a cell phone, electric vehicle due to its high energy density, high voltage. Although the extended use of LIBs technology, batteries which have higher capacity and can stand up to high speed charge/discharge than those of LIBs are demanded. Various studies have reported that the liquid phase occurring adjacent to solid particles has an anomalous behavior when compared to bulk solution[1]. Solid-liquid interface is performed as a base in charge-discharge of LIBs, so an elucidation of liquid phase properties of solid-liquid interface in the non-aqueous electrolyte solution system is important for improving the performance of energy storage devices such as LIBs. In addition, properties of the highly-concentrated electrolytes for performance improvement of LIBs are attracted. In this study, NMR spectroscopic behavior of non-aqueous LiClO4 solution mixed with fumed oxide nanoparticles as model system of gel electrolyte for LIBs, and their dynamic properties and influences to solvent molecules from solid phase or Li+ ion by measurement of the spin-spin (T 2) relaxation time and electrochemical measurement. Samples were prepared in Ar glovebox by mixing propylene carbonate(PC) or LiClO4/PC of predetermined concentration (1-3 mol L-1) and fumed silica(FS) (200 ± 20 m2 g-1), amorphous silica nanoparticles with self-cohesive properties, fumed alumina(FA) (130 ± 20 m2 g-1) and fumed titania(FT) (90 ± 20 m2 g-1) in NMR tube. A content of liquid phase were ranged from 90-100 vol% by gravimetry. We measured 1H and 7Li NMR spectroscopy (Varian INOVA 400; 9.39 T) and 1H spin–spin relaxation time; T 2measurements (XiGo Nanotools Acorn area ; 0.3 T). In 1H NMR spectra, a broad signal was confirmed under the existence solid-phase. It was shown that the dynamic property of PC molecules largely decreased in comparison with the case only for liquid phases. In PC/FS and PC/FA system, 1H NMR spectra shifted to higher magnetic field with the decrease of liquid content. For the shielding effect to the 1H nucleus of the PC molecules by the surface charge of fumed silica, a signal continues to shift to highly-magnetic field as a content of solid-phase increases. This result suggested that the apparent charge densities around the proton of PC molecules increased by fumed silica because fumed silica has a negative charge. In alumina dispersion, NMR signal shifted to higher magnetic field than that of fumed silica. From this result, alumina gives more influence on dynamics properties of liquid phase. A similar result was observed in 1-3 mol L-1 LiClO4/PC and solid coexisting system. From the liquid content dependences of the 1H NMR detection ratios of propylene carbonate, almost same amount of PC molecules were detected in PC/FS coexisting system. This result indicated that fumed silica formed network structure but H of PC molecules remained its dynamics. On the other hand, in fumed alumina or fumed titania dispersion, values of PC molecules detected by NMR decreased compared to the theoretical value of detected amount of PC by 1H NMR. It suggests that the mobility of PC molecules in fumed alumina and titania system were restricted than that in silica system. T2 in solid-liquid coexisting system is also shown in Fig. 1. From Fig.1, in all systems, the T2 value decreases because the dynamics of water molecules of the liquid phase decrease. The T2 value decreased in order of PC/FA, PC/FT, PC/FS system. The influence of the solid surface to solvent mobility in fumed alumina dispersion is the least of the three. This result supports a signal of the NMR and the result of 1H qNMR measurement. We will also discuss the NMR relaxation behavior for LiClO4-PC solution coexisting with te same fumed metal oxides. This study was supported by the JST Core Research for Evolutional Science and Technology (CREST). 【Reference】 [1] M. Mizuhata et al., J. Mol. Liq., 83, 179, (1999). Figure 1

A kinetic model of the reaction of dispersed aluminum with water under exposure to hydrocavitation and stabilization of the final product

The reaction of dispersed aluminum with water under the exposure of an A-IX-2 aluminum-containing explosive compound to hydrocavitation has been discussed. A kinetic model of the process has been developed; the chemical reaction rate constant has been determined under experimental conditions. It has been shown that the reaction occurs in an autocatalytic mode and can lead to the complete conversion of aluminum to aluminum hydroxide. A method to stabilize dispersed aluminum during the hydrocavitational extraction of a conversion explosive by using a phosphate buffer has been developed. Experiments have shown that the phosphate buffer has a stabilizing effect and leads to an improvement of the characteristics of the resulting industrial explosive composition.

Influence of aluminum precursors on structure and acidic properties of hollow silica–alumina composite spheres, and their activity for hydrolytic dehydrogenation of ammonia borane

In this study, we investigated the influence of aluminum precursors on structure and acidic properties of hollow silica–alumina composite spheres, as well as their activity for hydrolytic dehydrogenation of ammonia borane. Hollow silica–alumina composite spheres were prepared via the sol–gel method using polystyrene particles as templates. Activities of the hollow spheres prepared using various aluminum precursors for hydrolytic dehydrogenation of ammonia borane were compared. The molar ratios of evolved hydrogen to ammonia borane introduced were 1.0, 2.8, 1.5, and 3.0 in the presence of the hollow spheres prepared using aluminum ethoxide, aluminum isopropoxide, aluminum tributoxide, and aluminum-tri-sec-butoxide, respectively. Hollow spheres prepared using aluminum precursors with branched alkyl groups exhibit more hydrogen evolution than those prepared using aluminum precursors with normal alkyl groups. From the result of solid-state 27Al nuclear magnetic resonance spectra and temperature-programmed desorption of ammonia, 4-coordinated aluminum species are related to Brønsted acid sites, and highly dispersed aluminum species increase the number of Brønsted acid sites.

Understanding AlN Obtaining Through Computational Thermodynamics Combined with Experimental Investigation

Basic material concept, technology and some results of studies on aluminum matrix composite with dispersive aluminum nitride reinforcement was shown. Studied composites were manufactured by „in situ” technique. Aluminum nitride (AlN) has attracted large interest recently, because of its high thermal conductivity, good dielectric properties, high flexural strength, thermal expansion coefficient matches that of Si and its non-toxic nature, as a suitable material for hybrid integrated circuit substrates. AlMg alloys are the best matrix for AlN obtaining. Al2O3–AlMg, AlN–Al2O3, and AlN–AlMg binary diagrams were thermodynamically modelled. The obtained Gibbs free energies of components, solution parameters and stoichiometric phases were used to build a thermodynamic database of AlN– Al2O3–AlMg system. Obtaining of AlN with Liquid-phase of AlMg as matrix has been studied and compared with the thermodynamic results. The secondary phase microstructure has a significant effect on the final thermal conductivity of the obtained AlN. Thermodynamic modelling of AlN–Al2O3–AlMg system provided an important basis for understanding the obtaining behavior and interpreting the experimental results.

The effects of alumina nanoparticles as fuel additives on the spray characteristics of gas-to-liquid jet fuels

The use of metal nanoparticles as fuel additives have gained interest due to its positive influence on liquid fuels’ combustion and emission performance. Nanoparticles dispersion affects the hydrodynamic and thermo-physical properties of the liquid fuel, and in turn, its atomization, mixing and evaporation characteristics. This work investigates the influence of nanoparticles dispersion on the spray performance of alternative gas-to-liquid (GTL) jet fuel under atmospheric ambient conditions. The spray characteristics of GTL fuel with dispersed alumina nanoparticles are compared with those of the pure GTL fuel. The spray characteristics at the macroscopic and microscopic levels are measured using the optical diagnostic techniques of shadowgraph and phase Doppler anemometry, respectively. The nanoparticles dispersed in liquid fuel tend to slightly alter the transient nature of the spray formation, enhance the liquid sheet instability and reduce the liquid sheet breakup length when compared to those of the pure GTL fuel. Furthermore, the mean droplet sizes of GTL fuel dispersed with nanoparticles are smaller than those of the pure GTL fuel.

Freezing kinetics of vacuum-induced surface directional freezing in a glass vial

Directional freezing is used to prepare aligned porous materials made from ceramic dispersions. The alternate procedure of vacuum-induced surface-freezing uses a reduction in pressure to achieve freezing rather than the use of a cryogen-driven cold-finger. In this work the rate of directional freezing that occurs during vacuum-induced surface freezing of alumina dispersions in glass vials was measured using a video camera technique. The rate of advancement of the freezing front is broadly similar to that seen with conventional freeze casting: initially 900µm/s caused by spontaneous freezing of a surface layer at 250mTorr, followed by steady state at approximately 12–15µm/s during directional freezing. The steady state phase could be described by Stefan’s equation where the ice layer thickness grows with the square root of time. The temperature differences across the sample necessary to give the measured rates of advancement of the freezing front were calculated to be 18.8°C, 13.9°C and 9.1°C for volume fractions of dispersed phase of 0.032, 0.064 and 0.128, respectively. The temperature of the slurry below the freezing front declined from 0°C at the start of directional freezing to around −23°C at its conclusion. Stefan’s equation predicts that the temperature of the cold source, i.e. a sublimation front, is −14°C declining to −37°C, which are plausible values. The mechanism of vacuum-induced surface directional freezing is suggested to be undercooling of the slurry surface to below −10°C at reduced pressure by evaporative water loss. After rapid formation of a continuous, frozen surface-layer, sublimation starts and the enthalpy of sublimation assumes the role of a cold source for directional freezing. A sublimation front moves down through the frozen region behind the freezing front and has a rapidly declining temperature down to below −35°C. This is the cold source for directional freezing.

Using warm accumulative roll bonding method to produce Al-Al2O3metal matrix composite

In this study, warm accumulative roll bonding process has been used to produce metal matrix composite (Al/1% Al2O3). The microstructure and mechanical properties of composites have been studied after different warm accumulative roll bonding cycles by tensile test, Vickers micro-hardness test and scanning electron microscopy. The scanning electron microscopy results reveal that during higher warm accumulative roll bonding cycles, the layers of alumina particles are broken. It leads to the generation of elongated dense clusters with smaller sizes. This microstructure evolution leads to improve the hardness, strength and elongation during the accumulative roll bonding process. The results demonstrated that the dispersed alumina clusters improve both the strength and toughness of the composites. Also, an extra pass of cold rolling on the final warm accumulative roll bonding product shows the ability to obtain further strength. In general, warm accumulative roll bonding process would allow fabricating metal particle reinforced with high uniformity, good mechanical properties and high bonding strength.

Microstructure and Properties of Nanocrystalline Copper Strengthened by a Low Amount of Al2O3 Nanoparticles

Dispersion-strengthened Cu-Al2O3 materials have been studied over recent years to find an optimum processing route to obtain a high strength, thermal-stable copper alloy designed for modern applications in electrical engineering. The study analyses the influence of 1 vol.% of alumina content on strengthening the copper matrix. Microstructure of the Cu-Al2O3 composite was studied by x-ray diffraction as well as scanning and transmission electron microscopy. The composite shows a homogeneous, thermal-stable nanostructure up to 900 °C due to dispersed alumina nanoparticles. The particles effectively strengthen crystallite/grain boundaries in processes of powder consolidation and annealing of the compact. In contrast to monolithic Cu, the Cu-1 vol.% Al2O3 exhibits more than double strength and hardness. The nanocrystalline matrix and the low amount of alumina particles result in a yield strength of 288 MPa and a ductility of 15% which is a good combination for practical utilization of the material.

Refractory Cellular Concrete Based on Phosphate Binder from Waste of Production and Recycling of Aluminum

The article is considering the results of development of refractory cellular concrete based on aluminum-phosphate binder. It was prepared from aluminum production slag, aluminum recycling slag and aluminum etching sludges. The selection of aluminum phosphate is based on the fact that the aluminum-phosphate binders and materials are the most refractory. Fire clay, wastes of corundum production and used aluminum-chromium catalyst IM-2201 were used as aggregates. These are dispersed alumina and high-alumina industrial waste that do not require additional costs for milling. The basic properties of raw materials have been tested.The heat-resistant phosphate cellular concrete was developed based on fire clay and the corundum production waste, it has working temperature 1400-1600°C. Cellular concrete is setting due to the exothermic reaction fine powder of aluminum and phosphate binder. The porosity is formed by the reaction of metal - phosphate binder. The phase composition of the phosphate binders was investigated after setting and heating. The scheme of the phase composition changes is presented. The main heat-resistant properties are investigated for the resulting cellular concrete. It is found that the obtained material is not inferior to cellular concrete with pure aluminum-phosphate binder.

Influence of alcohol solvents on morphology of hollow silica–alumina composite spheres and their activity for hydrolytic dehydrogenation of ammonia borane

In this study, we reported effect of alcohol solvents on morphology of hollow silica–alumina composite spheres and their activity for hydrolytic dehydrogenation of ammonia borane. Silica–alumina composite shell was coated on polystyrene template particles via sol–gel reaction in various alcohol solvents. The hollow spheres were prepared in methanol, ethanol and 2-propanol for 36, 17 and 8 h, respectively. The results indicate that the order of sol–gel reaction rate was 2-propanol > ethanol > methanol. Amount of hydrogen evolution of the hollow spheres prepared in methanol and ethanol were higher than that of the hollow spheres prepared in 2-propanol. From the results of solid-state 27Al nuclear magnetic resonance spectra, we found that aluminum species of the hollow spheres prepared in methanol and ethanol were highly dispersed in their silica matrix. The results of temperature programed dispersion of ammonia showed that all the hollow spheres have weak and strong Bronsted acid sites. The amount of weak Bronsted acid sites in all the hollow spheres were of same level, while the amount of strong Bronsted acid sites increase with decrease of sol–gel reaction rate. These results indicate that the sol–gel reaction rate influences the dispersion of aluminum species, and highly dispersed aluminum species lead to increase in the amount of Bronsted acid sites.

Heterocoagulation of alumina and quartz studied by zeta potential distribution and particle size distribution measurements

This paper presents a new approach to characterizing heterocoagulation (i.e. coagulation of mixtures of dissimilar particles) by measuring the zeta potential distribution and the particle size distribution of individual and combined alumina and quartz at pHs 5, 7, and 10. The results show that the heterocoagulation of alumina and quartz would occur at pHs 5 and 7 but not at pH10. For the alumina and quartz particles under study, the aggregate size was mainly between 1.3 and 8.7μm and the quartz would act as the core particle and the alumina as the surrounding particles in the heterocoagulation process. The heterocoagulation and dispersion at different pHs and the aggregate structure at pHs 5 and 7 were verified by the scanning electron microscope analysis. The heterocoagulation and dispersion of alumina and quartz at different pHs can be accounted for by the interparticle force revealed by force analysis in the framework of the Deyaguin-Landau-Verwey-Overbeek theory.

Development of TiB<sub>2</sub> Dispersed Aluminum Composites by Spark Plasma Sintering

In order to obtain the high performance materials with high thermal conductivity, high electrical conductivity, low thermal expansion, good mechanical properties and low density, TiB2 particle dispersed aluminum (Al) composites was developed by spark plasma sintering. As these properties are affected by the dispersibility of the particles, the relationship among the dispersibility of dispersant and the thermal conductivity and mechanical properties was investigated, 20 vol. % TiB2 dispersed Al composites with different dispersibility were fabricated by spark plasma sintering (SPS). The dispersibility was estimated quantitatively by using the definition method of local number of particles (LN2DR method), and two composites having 6.884 and 4.839 for number of LN2DR was obtained. Thermal conductivity of the composites with homogeneous distribution of TiB2 particles was lower than that with heterogeneous distribution and clustering. On the other hand, the tensile strength of the composites improved as increasing temperature compared with Al block. Furthermore, strength of the composites with homogeneous distribution of TiB2 particles at 200°C and more was higher than that of the composites with heterogeneous distribution and clustering.

Co-Ni Electroless Composite Plating of Nanometer-Leveled Diamond Particles on Micrometer-Leveled Plastic Balls and the Application of Thus Prepared Devices to Various Electronics Processes

The aim of this paper is to develop a, lightweight and forceful Magnetic abrasive particles (MAP). Magnetic field assisted finishing was performed to examine the fabricated MAPs. A new MAPs based on the nickel-cobalt diamond composite plated plastic ball have been prepared successfully. The finishing results for “Damascene” sample or “Copper Overhang Generated in the Direct Laser Via Process” have suggested the powerful ability of the new MAPs to the field of the fabrication of various electronic devices. Magnetic abrasive particles (MAPs) are crucial to ensure finishing quality and accuracy in magnetic abrasive finishing (MAF) processing. Conventional MAPs consist of ferrous particles and abrasive, such as Al2O3, SiC, ZrO2, B4C as well as diamond, cubic boron nitride, MgO, CeO2 or fumed silica. The MAPs can be used as unbound, loosely bound or bound. One of them KMX 80 (trade name) are frequently used as commercial magnetic abrasives. This abrasive particle consists of dispersed aluminum oxide grains in iron matrix particles with the average diameter of 80 micrometer. Here, ferrous particles, which are mostly conventional used magnetic particle in MAF process, provide force of grinding via magnetic field. But due to the corrosion and softness of ferrous materials, the post-cleaning of the surface finished by the MAPs containing ferrous particles becomes the most time-consuming and critical procedure in some ultra-precision MAF processing, other magnetic particles should be urgent to be developed to replace the conventional ferrous particles. In this paper a, lightweight and forceful MAP has been developed. And Magnetic field assisted finishing was performed to examine the fabricated MAPs. A new bound MAP based on the electroless cobalt-nickel boron, 20 nm sized diamond composite plating to plastic balls was prepared. 10 mirometer sized Plastic ball was used as support here for MAPs growth due to its lightweight properties. “Damascene” sample were supplied by Selete Co. Ltd. The original surface of the sample was covered with over-coated copper layer. Thus supplied sample was used as a workpiece. The AFM images of the surface profiles was captured after finishing by KMX80 (3 mins) followed by the cobalt-nickel diamond composite plated plastic balls for 8 mins. The AFM images for the sample after MAF suggests that nano meter-sized surface smoothing could be attained. The best finishing conditions will be needed to be investigated in future. Another approach of MAP to electronic devices has been tried for removal of copper overhang generated in the direct Laser via process by use of magnetic polishing method. In recent years, via holes has been used for the connection of external wiring and internal wiring of the multilayer substrate. When copper foil of wiring layer was processed by laser, melted copper was adhered, so projections called “overhang” are formed around the opening of via hole. Adhesiveness and flatness of plating will be decreased by the overhang, therefore removal process of them will be indispensable. Therefore magnetic polishing method has been tried as a novel removal technique in this study. In conclusion, the finishing results for “Overhang” sample have suggest the powerful ability of the new MAPs to the field of the fabrication of the FWB(Printed Wiring Board) devices.

Synthesis and characterization of the nano alumina-filled tetraglycidyl-4, 4′-diaminodiphenylmethane epoxy resin

In this study, the in situ incorporation of the inorganic alumina nanoparticles into the reactants of tetraglycidyl-4, 4′-diaminodiphenylmethane (TGDDM) epoxy resin represented an efficient way for the preparation of alumina/TGDDM nanocomposite. The surface modification of the alumina nanoparticles was carried out using two individual silane coupling agents, namely, aminopropyltriethoxysilane (APS) and glycidoxypropyltrimethoxysilane (GPS). The degree of silane grafting was evaluated for both coupling agents using FTIR spectroscopy and thermogravimetric analysis. The epoxy equivalent weight (EEW) of the epoxy resin in addition to the weight percentage of the lost nanoparticles during TGDDM polymerization was used as measurements of the polymerization yield. The neat nano alumina has more adverse effect on the epoxy EEW value (171 g/mol) than both silane-modified nano alumina (143–157 g/mol, depending on the reaction conditions). The degree of nano alumina dispersion in the epoxy matrix was investigated using SEM micrographs. The longer and more deflected crack pathways on the fractured surface of the alumina/TGDDM nanocomposites may be attributed to a relatively good degree of dispersion of the silane-modified alumina nanoparticles in the epoxy matrix. Compared to neat alumina, the better dispersion of the silane-modified alumina nanoparticles may be related to the improved interfacial interactions between the oxiran or amine groups available on the silane-modified alumina nanoparticles and the TGDDM epoxy functional groups. Besides, the higher exothermic heat of cure (i.e., 30–53 %) as evidenced in differential scanning calorimetry may be due to a rather good state of dispersion of silane-modified alumina nanoparticles.

Mixed matrix membranes comprising PMP polymer with dispersed alumina nanoparticle fillers to separate CO2/N2

In regards to the evolution of desirable properties and chemical structure for high performance of gas separation by membranes, mixed matrix membranes (MMMs), need to be carefully designed and controlled to realize high efficiency. This research investigates the role of the main parameters in the fabrication and performance analysis of MMMs prepared through blending of alumina nano particles (Al2O3) and poly(4-methyl-1-pentyne) known as PMP with various weight percentages of alumina nano-particles in the PMP precursor. Precursor and resultant MMMs were characterized using thermogravimetric analysis (TGA) and scanning electron microscopy (SEM) techniques. SEM images demonstrated the proper dispersion of Al2O3 particles in the precursor matrix. Results indicated that the microstructure of the precursor, blend composition, and the content of nano particles play an important role in gas transport properties of the resulting MMMs. The influence of the percentage of alumina nano particles used in the precursor matrix on the CO2 and N2 permeability and CO2/N2 illustrated a selective trend for the MMMs. Using higher alumina content resulted in membranes with higher permeability and ideal selectivity. The highest rate of CO2 and N2 permeability could be obtained from PMP-alumina with a loading of 30 wt% alumina (PMP30) at 10 bar. Furthermore, these results suggest that PMP30 MMMs (at operating pressures of 8 bar) are exceptional candidates for the CO2/N2 separation, offering enhanced gas pair selectivity in the range of 4.5-5 depending on the operating pressure. The results of this research revealed that high-performance gas separation by MMMs can be realized through adopting a judicious combination of blending and dispersing techniques. Open image in new window

The effect of boehmite alumina nanoparticles on the properties of polylactide/polypropylene blend composites

The effect of boehmite alumina nanofiller on properties of polylactide/polypropylene blend compatibilized with 3% maleic anhydride grafted polypropylene was investigated. Boehmite alumina nanoparticles were finely dispersed in polylactide/polypropylene/boehmite alumina blend up to 7 wt.% to form blend nanocomposites which were prepared by twin-screw melt compounding. The morphology, thermal, mechanical, heat distortion temperature, thermomechanical and degradation characteristics were investigated. Scanning electron microscopy indicated a tubular morphology with increasing boehmite alumina in the blend matrix particularly at 5 and 7 wt.% of boehmite alumina loadings with few agglomerates. Transmission electron microscopy indicated a highly dispersed boehmite alumina in the blend nanocomposites. Boehmite alumina nanoparticles significantly influenced the thermal properties and a nucleation of the blend matrix. A significant improvement in the tensile modulus and tensile strength upon addition of boehmite alumina in the blend nanocomposites was obtained. However, beyond 3 wt.% of boehmite alumina addition, there was a clear deterioration in mechanical properties.

Characteristics of Nano-alumina Particles Dispersion Strengthened Copper Fabricated by Reaction Synthesis

Abstract Alumina dispersion strengthened copper (ADSC) composite was prepared by reaction synthesis (RS) process. Results show that nano-sized γ-Al2O3 particles with about 10 nm in size are homogeneously distributed in copper matrix. A coherent interface relationship with (002)Cu // (133)γ-Al2O3, and [110]Cu//[011]γ-Al2O3 characterizes along the explored interfaces of the composites. All of the interfaces are clear and closely combined with each other. The composites have high properties, the tensile strength can reach 570 MPa and the yield strength can reach 533 MPa at room temperature. Meanwhile, the softening temperature is higher than 1173 K. The electrical conductivity of the sample is 85% IACS and the Rockwell hardness can reach 86 HRB.

Characterization of ball-milled carbon nanotube dispersed aluminum mixed powders

Currently, carbon nanotube (CNT) is attracting much interest as fibrous materials for reinforcing aluminum matrix composites due to unique properties, such as high strength, elastic modulus, flexibility and high aspect ratios. However, the quality of the dispersion is the major concerning factor which determines the homogeneity of the enhanced mechanical and tribological properties of the composite. This work study and characterized carbon nanotube dispersion in ballmilled CNT-aluminum mixed powders with four different formulations such as 1, 1.5, 2 and 2.5 wt% CNT under high energy planetary ball milling operations. The ball milling was performed for two hours at constant milling speed of 250 rpm under controlled atmosphere. The characterization is performed using FESEM and EDX analyzer for mapping, elemental and line analysis. The experimental results showed homogeneous dispersion of CNTs in aluminum matrix. The composite mixture showed similar pattern from mapping, elemental and line analysis. Identification of only two peaks proved that controlled atmosphere during milling prevented the formation of inter metallic compounds such as aluminum carbide in the composite mixture. Therefore, this CNT-A1 composite powder mixture can be used for new nano-composite development without any agglomeration problem.

One pot eco-friendly synthesis of highly dispersed alumina supported alginate biocomposite for efficient chromium(VI) removal

An eco-friendly biocomposite namely alumina/alginate (AlAlg) composite was synthesized by uniformly dispersing alumina (Al) over alginate (Alg) polymeric matrix by one-pot method. The structure, surface morphology and elements present in the biocomposite was characterized using instrumental techniques like FTIR, SEM and EDAX analysis respectively. Batch process was adopted to investigate the potential of the composite toward chromium(VI) removal. The various adsorption influencing factors like contact time, pH, competing anions, initial chromium concentration and temperature were investigated. The maximum Cr(VI) sorption capacity (SC) of AlAlg composite was found to be 17.45mg/g and shows enhanced SC than CaAlg composite which posses the SC of 9.45mg/g. The experimental datas were fitted to various isotherms and kinetic models. The nature of chromium sorption was explained by the calculated values of thermodynamic parameters and the feasible chromium sorption mechanism was also established.