Dispersed Alumina Research Articles

Influence of operational parameters and design of the ejection nozzle on characteristics of finely dispersed aluminum powder: Part I. Influence of operational parameters of the nozzle

The results of analyzing the influence of operational parameters of the ejection nozzle on the characteristics of highly dispersed aluminum powder in production conditions at OOO SUAL-PM are presented. Measurements of dispersed characteristics of the spray when spraying the aluminum melt by the ejection nozzle are performed when varying the consumption and temperature of spraying gas in ranges of 0.17–0.21 m3/s and 873–933 K, respectively, as well as the melt temperature in limits of 1153–1253 K. The results of determining the median diameter of the particles (dm) and content of the highly dispersed fraction (z) (with a particle diameter no larger than 10 μm) in the spray are presented. It is shown that, when modifying the operation parameter of the nozzle, the value of dm decreases by 3.7–12.4%, while the magnitude of z increases by 0.4–3.2%. It is established that an increase in temperature of spraying gas affects the powder properties most effectively.

Lightweight Refractory Concrete Based on Aluminum-Magnesium-Phosphate Binder

The paper is discussing the results of works on preparation of refractory concrete based on aluminum-magnesia-phosphate binder. The modification of magnesia phosphate binder by aluminum allows increasing the stability of the binder, as well as the material working temperature. The choice of aluminum is based on the fact that aluminum-phosphate binders are the most refractory. Corundum manufacturing waste and used aluminum-chromium catalyst IM-2201 were used as aggregates. These are dispersed alumina industrial waste that does not require additional milling. The basic properties of aggregates have been tested. Heat-resistant phosphate cellular concrete with working temperature up to 1600°C was developed. Cellular concrete does not require heat treatment; its hardening is due to the exothermic reaction of aluminum metal and phosphate binder. The phase composition of the phosphate cement was investigated after curing and burning. The effect of aggregate type on phase composition was detected. The earlier formation of stable high-refractory aluminum phosphates was observed. The main refractory properties of the cellular concrete were tested. It is found that the obtained material is not inferior to cellular concrete with aluminum-phosphate binder.

Studies on Amorphous Alloy Dispersed Aluminium Matrix Composite Prepared by High Pressure Torsion

<p class="1Body">Aluminium-based composite reinforced with Cu base amorphous alloy dispersed composite was prepared by means of high pressure torsion between a powder mix of aluminium and amorphous Cu base alloy. The X-ray diffraction pattern of powdered and consolidated composites shows the aluminium phase while the thermal stability of the amorphous alloy was studied with the aid of differential scanning calorimetry (DSC). The microstructural feature of the composite through scanning electron microscope reveals the well-distributed reinforcements in the host aluminium matrix. The hardness measurement on the as prepared composites shows significant increase in hardness with increase in reinforced amorphous alloy. Wear property of the synthesized composites were measured by using ball on plate wear tester which shows increase in wear resistance with increase in reinforced amorphous alloys.</p>

Microstructure evolution of alumina dispersion strengthened copper alloy deformed under different conditions

Microstructure and texture evolution of Cu–0.23%Al2O3 dispersion strengthened copper alloy, deformed at room temperature or cryogenic temperature, were investigated. The main textures in hot-extruded specimen were Brass {011} <211> and Cube {100} <100>. Textures of Brass {011} <211> and Goss {011} <100> were observed in specimen after deformation at room temperature; while textures of Brass {011} <211>, Goss {011} <100> and S {123} <634> were detected after deformation at cryogenic temperature. It is believed that the additional Al2O3 nanoparticles can result in dislocation pinning effect, which can further lead to the suppression of dislocations cross-slip. While in the specimen deformed at cryogenic temperature, both pinning effect and cryogenic temperature are responsible for the formation of Brass, Goss and S textures.

Stereolithographic Additive Manufacturing of Diamond Photonic Crystal Composed of Titania and Alumina Micro Lattices

Three dimensional micro photonic crystals with a diamond structure made of a dense titania and alumina were fabricated successfully by using stereolithographic additive manufacturing. Photonic band gap properties were investigated in gigahertz and terahertz wave frequency ranges. Acrylic diamond lattice structures with nanometer sized particles of titania and alumina dispersion at 40 vol. % were fabricated by the stereolithography. The forming accuracy was 10 μm. After dewaxing and sintering process, the titania and alumina diamond lattice structures were obtained. The relative density reached above 98 %. Electromagnetic wave transmittances were measured by using a W-band millimeter waveguide connected with a network analyzer and a terahertz wave time domain spectroscopy. In the transmission spectra for the Γ-X &amp;lt;100&amp;gt; direction, a forbidden band was observed at 90 – 110 GHz and 0.4 – 0.6 THz. The band gap frequencies well agreed with calculated results by plane wave expansion (PWE) method. Additionally, simulated results by transmission line modeling (TLM) method indicated that a localized mode can be obtained by introducing a plane defect between twinned diamond lattice structures.

Effect of alumina dispersion on oxidation behavior as well as friction and wear behavior of HVOF-sprayed CoCrAlYTaCSi coating at elevated temperature up to 1000 °C

CoCrAlYTaCSi alloy coating and CoCrAlYTaCSiAl2O3 composite coating were prepared on Inconel 718 alloy substrate by high velocity oxy-fuel (HVOF) spraying in order to avoid the failure of the hot parts made of the Ni-based alloy induced by oxidation and wear damage at elevated temperature of up to 1000°C, with which the agglomerated powder of CoCrAlYTaCSi and Al2O3 was sintered to afford the to-be-sprayed CoCrAlYTaCSiAl2O3 powder. The microstructure and phase composition of the as-sprayed coatings were analyzed by scanning electron microscopy, transmission electron microscopy and X-ray diffraction, and their mechanical properties were determined with a Vicker’s hardness tester and a nano-indentation tester. Furthermore, the oxidation behavior of the coatings was evaluated by thermogravimetry and oxidation test in muffle furnace, and their friction and wear behavior under dry sliding against Si3N4 ball from room temperature to 1000°C was evaluated with a high temperature tribometer. Results show that Ta, C and Si elements mainly exist in the forms of TaC and SiC nano-particles in as-sprayed coatings. The incorporation of Al2O3 dispersion results in a significant increase in the hardness, modulus, contact stiffness and wear resistance, but metallic Co and Cr slightly reduce the oxidation resistance of CoCrAlYTaCSi coating. Particularly, as-fabricated CoCrAlYTaCSiAl2O3 coating exhibits much better wear resistance than CoCrAlYTaCSi coating and other MCrAlY/oxide metal-matrix coatings prepared by HVOF or other technologies, showing promising potential as a protective coating of Ni-alloy based hot parts.

Experimental investigation on effect of ultrasonication duration on colloidal dispersion and thermophysical properties of alumina–water nanofluid

Two decades have been going on since nanofluid was introduced with the hope that it could enhance the thermal performances of heat transfer applications. Nevertheless, yet, there are no standards for nanofluid preparation process (sonicator type, power, amplitude, duration) to achieve stable and well-dispersed nanofluid. The aim of this research is to analyze the consequence of ultrasonication duration on colloidal dispersion and thermophysical properties of 0.5vol.% of Al2O3–water nanofluid. A horn ultrasonic dismembrator was used for different periods from 0h to 5h for nanofluid preparation. Particle size distribution (PSD), zeta potential, and microstructure were studied to check the dispersion characteristics. Thermal conductivity, viscosity, and density of the nanofluid were analyzed for different temperatures from 10°C to 50°C. Better dispersion, higher thermal conductivity and density, and lower viscosity have been observed with the increase of sonication time. Furthermore, thermal conductivity was found to be increased but viscosity and density were decreased with the increase of temperature. The research concluded that higher ultrasonication duration is best and at least 2h of ultrasonication is needed for better performance of the nanofluid.

Uptake of Arsenic(V) Using Alumina Functionalized Highly Ordered Mesoporous SBA-15 (Alx-SBA-15) as an Effective Adsorbent

The SBA-15 (a mesoporous SiO2 material) decorated with 10% aluminum (Al10-SBA-15) was found to be an excellent adsorbent to remove As(V) from water. The highly dispersed aluminum species have been obtained over the well-ordered mesoporous Al10-SBA-15 adsorbent and act as the active adsorption sites for arsenic(V) removal instead of SiO2. The adsorption behavior of As(V) onto Al10-SBA-15 was investigated in aqueous solution using various experimental parameters. The adsorption data of As(V) could be fitted more successfully by the Langmuir isotherm than the Freundlich isotherm model, and the pseudo-second-order equation described this entire adsorption process well. It is found from the analysis of kinetic data with the intraparticle diffusion mode that both the boundary layer (film) diffusion and intraparticle diffusion may contribute to the rate-limiting steps. Importantly, Al10-SBA-15 exhibits high arsenic(V) removal in the wide pH range of 2.0–8.2 and can remove As(V) from water containing arsenate of ...

INFLUENCE OF MODE PARAMETERS AND DESIGN OF THE EJECTION NOZZLE ON CHARACTERISTICS OF HIGHLY DISPERSED ALUMINUM POWDER. PART 2. INFLUENCE OF THE NOZZLE DESIGN

The influence of the design of an ejection nozzle on characteristics of highly dispersed aluminum powder in industrial conditions at the LLC «SUAL-PM» enterprise is performed. Measurements of dispersed characteristics of the spray product when spraying the aluminum melt by the ejection nozzle are performed for six variants of modified nozzles. The results of determining the median diameter of particles ( d ) and content of a highly dispersed phase ( z ) (with the particle diameter no larger than 10 μm) in the spray product are presented. It is shown that the most efficient method of modifying the spray nozzle is profiling the cone part of a protective bush and imposition of ultrasonic vibrations on a nozzle case (a decrease in d m by ~31,6 % and an increase in z by ~8,5 %).

Oxidation Behavior of Ti Added Alumina Dispersion Strengthening Copper Alloy

【Alumina dispersion strengthening copper(ADSC) alloy has great potential for use in many industrial applications such as contact supports, frictional break parts, electrode materials for lead wires, and spot welding with relatively high strength and good conductivity. In this study, we investigated the oxidation behavior of ADSC alloys. These alloys were fabricated in forms of plate and round type samples by surface oxidation reaction using Cu-0.8Al, Cu-0.4Al-0.4Ti, and Cu-0.6Al-0.4Ti(wt%) alloys. The alloys were oxidized at $980^{\circ}C$ for 1 h, 2 h, and 4 h in ambient atmosphere. The microstructure was observed with an optical microscope(OM) and a scanning electron microscope(SEM) equipped with energy-dispersive X-ray spectroscopy(EDS). Characterization of alumina was carried out using a 200 kV field-emission transmission electron microscope(TEM). As a result, various oxides including Ti were formed in the oxidation layer, in addition to ${\gamma}$ -alumina. The thickness of the oxidation layer increased with Ti addition to the Cu-Al alloy and with the oxidation time. The corrected diffusion equation for the plate and round type samples showed different oxidation layer thickness under the same conditions. Diffusion length of the round type specimen had a value higher than that of its plate counterpart because the oxygen concentration per unit area of the round type specimen was higher than that of the plate type specimen at the same diffusion depth.】

High temperature mechanical behavior of alumina dispersion strengthened copper alloy with high content of alumina

The microstructure and its effects on the high temperature mechanical behavior of Cu–2.7%Al2O3 (volume fraction) dispersion strengthened copper (ADSC) alloy were investigated. The results indicate that fine alumina particles are uniformly distributed in the copper matrix, while a few coarse ones are distributed on the grain boundaries. Tensile tests results show that Hall-Petch mechanism is the main contribution to the yield strength of ADSC alloy at room temperature. Its high temperature strength is attributed to the strong pinning effects of alumina particles on the grain and sub-grain boundaries with dislocations. The ultimate tensile strength can reach 237 MPa and the corresponding yield strength reaches 226 MPa at 700 °C. Tensile fracture morphology indicates that the ADSC alloy shows brittleness at elevated temperatures. Creep tests results demonstrate that the steady state creep rates at 400 °C are lower than those at 700 °C. The stress exponents at 400 °C and 700 °C are 7 and 5, respectively, and the creep strain rates of the ADSC alloy are controlled by dislocation core diffusion and lattice diffusion.

Impact of anionic and cationic polyacrylamide on the stability of aqueous alumina suspension—comparison of adsorption mechanism

In the present study, particular emphasis was put on the effects of the type of functional groups of anionic and cationic polyacrylamide (PAM) and solution pH on the mechanism of polymer adsorption on the surface of dispersed alumina. The polymer-adsorbed amount, surface charge density and zeta potential of solid particles without and with PAM, as well as the stability of Al2O3 suspension containing the polymer, were determined. For this purpose, the spectrophotometry, potentiometric titration, microelectrophoresis and turbidimetry were applied. It was shown that adsorption of anionic PAM decreases with the pH rise, whereas in the case of cationic PAM, it increases. High adsorption level is a result of more coiled structure of adsorbed macromolecules. The anionic PAM has greater impact on the suspension stability deterioration in comparison to the cationic polymer in the whole range of studied pH values. The more pronounced effect of alumina suspension destabilization in the anionic PAM presence was obtained at pH 6, at which solid surface charge neutralization occurs.

Optimization of Dielectric Constant of Polycarbonate/Polystyrene Modified Blend by Ceramic Metal Oxide

We modified a polycarbonate (PC)/polystyrene (PS) blend by loading alumina (Al2O3) into the blend. X-ray diffraction (XRD) shows a decrease in crystallinity. The optical microscopy and atomic force microscopy (AFM) confirms the homogeneous dispersion of alumina. The differential scanning calorimetry (DSC) data shows improved results in glass transition (Tg) and melting temperature (Tm) of blend systems. The electrical properties of polymer blends modified by Al2O3 were studied as a function of frequency (50 Hz–35 MHz) at 323 K. The alumina showed a significant effect in resulting in a high dielectric constant with low dielectric loss and dissipation factor.

Electro Deposition of Nickel-alumina Composite Coating

Nickel-alumina composite coatings were synthesized by electrodeposition technique. The co-deposition of alumina was accomplished by using magnetic stirring, variation of current density and temperature. The xrd analysis confirmed the formation of Ni-Al2O3 composites and the SEM studies revealed uniform dispersion of alumina into nickel matrix. The morphology of the alumina particles found significantly affected by the current density and temperature. The incorporation of alumina showed increased hardness and wear resistance of the coatings.

Effect of surfactant on dispersion of alumina in photopolymerizable monomers and their UV curing behavior for microstereolithography

Ceramic microstereolithography has recently emerged as a solid free form fabrication techniques for the fabrication of three-dimensional (3D) ceramic components of complex shapes. The spatial resolution of ceramic parts depends upon cure depth and cure width of UV curable ceramic suspensions. Ceramic particle size, its distribution and difference in the refractive indices between ceramic particles and UV curable monomer influence suspension microstructure which will be reflected in viscosity change and extent of colloidal gelation. Suspensions of alumina are formulated in a monomer having hydrophobic backbone structure (monomer chains terminating both ends with –CH2–) by dispersing alumina modified with suitable carboxylic acids (stearic acid and oleic acid). Another suspension was prepared just by dispersing as received alumina in a monomer having hydrophilic backbone structure (monomer chains terminating one end with –OH–). Suspensions exhibit different microstructures owing to solvency of adsorbed layer in monomer having hydrophobic backbone structure, interaction of hydroxyl groups present on alumina particles with monomer having hydrophilic backbone structure as revealed by dynamic rheology. We report effect of microstructure of these suspensions on UV curing behavior by monitoring C=C conversion. The spatial resolution of ceramic part is predicted by measuring cure depth and cure width for the suspensions cured in microstereolithography apparatus.

Study of Al2O3 addition to synthetic Ca‐based sorbents for CO2 sorption capacity and stability in cyclic operations

AbstractSynthetic CaO sorbents were prepared using alumina as a sintering inhibitor via a simple precipitation method. The effects of three mixing procedures on the physical properties and CO2 capture performance of the sorbents were examined. The cyclic CO2 capture performance of the sorbent derived from the precipitation of calcium salts over colloidal alumina (highly dispersed alumina gel) showed the best performance of the three mixing methods. It was found that variation of alumina‐to‐CaO ratios did not significantly change the sintering influence on the sorbent capacity in cyclic operations. CaO particles homogeneously mingled with alumina at higher ratios. Sintering prevention, however, was not observed. This important observation indicates that alumina appeared to merely act as a binder for the fabrication of mechanically enhanced strength particles that are suitable for large‐scale operations. It was determined that CO2 uptake was not dependent on either the mixing technique or the type of synthetic materials incorporated into a sorbent in cyclic operation. The sorbent derived from the precipitation of calcium salts over colloidal alumina with an alumina‐to‐CaO ratio of 20:80 achieved the highest CO2 uptake of 13.1 moles/kg sorbent for half an hour of carbonation in the first cycle and retained a sorption capacity of 6.5 moles/kg sorbent after 17 successive cycles (50 % activity loss), which is in agreement with the reported results. It was demonstrated that the quantity of CO2 uptake increased moderately with decreasing sorbent particle sizes. The effect of pressure on sorbent CO2 uptake was insignificant.

Development of Research and Application of Copper Alloys with High Strength and High Conductivity

High-strength and high-conductivity copper alloy is a kind of structural function materials, which has excellent comprehensive mechanical and physical properties. The strengthening methods of copper alloy are summarized. The basic requirements of high-strength and high-conductivity copper alloy is established. The application of the materials is described, including lead frame materials, electrified contact wires materials, electrode Materials. Meanwhile, the alumina dispersion strengthened copper alloy is introduced. The internal oxidation process, structure, dispersoid and anti-intenerate properties have also been analysis in detail. Finally, the development direction of this material is put forward.

Mathematical Model of Iron Reduction with Aluminothermic Method

Utilization of industrial waste in foundry engineering is one of approaches for decrease of production cost price. This technological process may be based on exothermic oxidation-reduction reaction with the resulting formation of iron from dross. Initial charge mixture consists of dispersed aluminum, iron dross and admixtures. This paper is concerned with mathematical modeling of thermite steel production. Presented model takes into account thermal, mechanical and kinetic processes occurring in aluminothermic method of steel melt production.

Three‐Dimensional Stereolithography of Alumina Photonic Crystals for Terahertz Wave Localization

Using stereolithography as an additive manufacturing (AM) process, photonic crystals, with a diamond‐like structure composed of alumina microlattices, were fabricated and their electromagnetic band gap profiles, in terahertz frequency ranges, were investigated. Acrylic resins with dispersed alumina particles were fabricated by stereolithography with micrometer‐order accuracy. After dewaxing and sintering processes, alumina lattices were obtained with high relative densities that reflected the terahertz waves, through Bragg diffraction, perfectly in all directions. Twinned crystal structures with mirror symmetric diamond lattices were designed to introduce defect interfaces. Double‐cavity defects consisting of unit cells hollowed from the diamond lattices formed the coupled resonation modes.

Behaviour of Amorphous Aluminosilicates towards Ageing by High-Temperature Steaming

The structure of amorphous aluminosilicates obtained by grafting silicon on alumina (Si/Al2O3) mostly remains the same after ageing by steaming. The rearrangement of surface silicon species on the facets of γ-alumina slightly decreases the number of Brønsted acid sites, which is determined through ethanol adsorption followed by thermogravimetry as well as m-xylene isomerisation. Al/SiO2 prepared by grafting aluminium on silica undergoes sintering of the silica support and the agglomeration of the surface aluminium species during steaming. This process leads to a sharp decrease in the number of Brønsted acid sites, which are associated with the dispersed aluminium species, and dehydroxylation of the silica surface.