Commercial Alumina Powder Research Articles

Preparation of Al‐Dy core‐shell particles by electron beam treatment of Al powder with consequent magnetron deposition of Dy film

• A new method was proposed for coating a commercial aluminum powder by Dy. • Low-energy high-current electron-beam treatment and magnetron sputtering were used. • Surface smoothing and cleaning were detected after electron-beam refinement. • The average size of powder particles increases with the number of e-beam pulses. • Rolling and shaking of powder during the treatment causes uniformity of deposition. The paper presents a new method for coating commercial metal powders with rare‐earth elements (REE). This method consists of a two‐step treatment of a metal powder in a single vacuum cycle, namely the pulsed irradiation above the melting point by a low‐energy high‐current electron beam with subsequent magnetron sputtering of REE. This research reports the preparation of Al‐Dy core‐shell powder with an average diameter of particles of 40 µm. A powder holder system, providing rotary agitation and shaking of powder, was used to guarantee the uniform processing of each particle. It was established that electron beam irradiation leads to smoothing and cleaning the Al particles from surface oxides. With an increase in the number of pulses, the uniformity of processing increases; however, an increase in the average particle size occurs. Subsequent magnetron sputtering allows completely coating the surface of processed powder with dysprosium. The proposed method can be suitable for fabricating different metal‐REE core‐shell powders with necessary changes in processing parameters.

Commercial aluminum powders, Part I: Particle size characterization and slow heating rate thermal analysis

We characterized nine commercial aluminum (Al) powders using several methods to measure particle characteristics and thermal analysis, with the goal to understand how these parameters influence energy release. Although it is well-known that lot-to-lot variations in commercial nanoparticles are common, the Al powders were more heterogeneous than anticipated – both with regards to particle size distributions and impurities. Manufacturer specifications – often quoted in the literature without confirmation – were not always accurate for the specific sample lots we investigated. In several cases, different conclusions could be drawn from individual particle size techniques; a combination of multiple techniques provides a clearer picture of the powder properties. Thorough characterization of Al powders is required prior to interpretation of experimental results from a variety of applications. In particular, previous studies have shown contradictory results on the influence of Al on detonation performance, perhaps partially due to insufficient characterization of the Al powders themselves.

Commercial aluminum powders, part II: Energy release rates induced by rapid heating via pulsed laser excitation

We used nanosecond laser pulses to excite various aluminum (Al) powders under an extremely fast heating rate (1013 K/s). Our interest lies in three timescales: early (1–10 μs), middle (10–500 μs), and late (tens of milliseconds). We used several spectroscopic methods to monitor AlO emission to track the Al oxidation on all timescales. The characteristic laser-induced air shock velocity determined relative energy release from each Al powder on the early timescale. We found that the Al nanopowders had higher laser-induced shock velocities than the micron-sized powders, indicating faster energy release. The AlO emission monitored in the early time regime correlated with the laser-induced shock velocities, confirming that the increases in laser-induced shock velocities observed resulted from earlier oxidation of the Al. The heterogeneous nature of the Al samples and the strong influence of their properties on fast energy release demonstrated the importance of well-characterized samples for interpreting detonation experiment results.

Production and Characterization of Commercial Aluminum Powders by a New Nozzle Design and Atomization Unit

Abstract: A large area cross section of the production of spherical metal powders by gas atomization in the manufacturing method. Powder metal characteristic improves with small powder size. This aim was realized by vertical gas atomization unit, a new a closely-matched nozzle system and manufacture. In the experimental studies, pure aluminium powders which has an important place in the automotive, air and defence industries were produced. In the studies carried out with the Vertical Gas Atomization unit, aluminium was superheated up to 900°C and atomized at different gas pressures (20-30 bar). Scanning electron microscope (SEM) and particle size measuring device were used for the characterization and size measurements of the produced powders, respectively. The average particle size of the finest powder produced with increasing atomization pressure was determined as d50=19.50µm. Aluminium powder shape and morphology was used as spherical and very little satellization was seen. Keywords: Powder Metallurgy, Atomisation, Nozzle, Al powder, Characterisation

Aluminum Powder Preparation for Additive Manufacturing Using Electrostatic Classification

This work aims to study the possibility of using an electrostatic drum-type separator to prepare a powder with a narrow size distribution curve for usage in additive manufacturing. The size distributions of the uncoated commercial aluminum powders ASP-30, ASP-22, and ASP-5 were analyzed. It was shown that the powders ASP-30 and ASP-22 have similar asymmetric distributions with a SPAN of 1.480 and 1.756, respectively. ASP-5 powder, in turn, has a narrow distribution with a SPAN of 0.869. ASP-30 powder was chosen for further experiment because, traditionally, separators are used to classify large-sized materials with particle size more than 100 μm. The optimal mode of electrostatic classification was proposed for the selected powder. Various classification methods, including centrifugal and electrostatic, were compared. The powders before and after classification were studied by XRD, SEM, TEM, and TG–DSC analyses. The obtained results showed that electrostatic classification does not lead to the formation of coatings on the processed powders. Electrostatic separation effectively narrows the particle size distribution, making it a suitable and valuable method to classify initial powders for additive manufacturing.

Effect of SiO2 Coating on Microstructure and Mechanical Behavior of Al-ABOw Composite Synthesized by Powder Metallurgy Technique

In this investigation, powder metallurgy route was employed to synthesize SiO2 (5, 10 and 15 vol%) coated aluminium borate whisker (ABOw) reinforced aluminium composites. Commercial pure aluminium powder was used as matrix material and SiO2 coated ABOw was used as reinforcements. M icrostructures of the composites were characterized using scanning electron microscopy and high resolution scanning electron microscopy. Energy dispersive spectroscopy was employed to confirm the weight percentages of elements present in the composites. Transmission electron microscopic analysis was performed to observe morphological changes in the composites. X-ray diffraction analysis was carried out to confirm the phases of developed reinforcement and composites. A universal testing machine was employed for the observation of mechanical properties, viz. flexural strength, Young’s modulus and diametral compressive strength, and it was found that the mechanical strength improved by 50-55% in the case of 10 vol% SiO2 coated Al-ABOw composite. The effect of SiO2 coating on the hardness of fabricated composite was also evaluated and the maximum microhardness value was observed to be 46.2 HV in 10 vol% SiO2 coated composite. Themicrostructural analysis showed that excellent grain refined structures with improved mechanical strength were obtained.

Hydrogen generation performance of waste aluminum alloy chips and powders

ABSTRACT The objective of this work is to compare and evaluate hydrogen generation performance of 1050, 6013, and 7075 series commercial aluminum machining chips and powders obtained from mechanical milling of the chips. Prior to mechanical milling 20 wt.% NaCl was added to aluminum chips to activate aluminum. NaCl salt also functioned as a process control agent and prevented excessive cold welding of aluminum particles during intense plastic deformation applied by ball milling. Morphology of chips and powders was analyzed by scanning electron microscopy. Hydrogen generation experiments were performed by using distilled water and 1 M NaOH solution at 70°C. The effect of temperature on the hydrogen production performance of aluminum alloys was also investigated in the range of 30–70°C. Mechanically milled powders gave higher hydrogen generation yield compared to the chips. Severe cold working by mechanical milling accelerated the corrosion and increased the hydrogen production performance of the powders. Hydrogen production efficiency of milled powders in NaOH solution was approximately 3.5–7 times higher than milled powders in distilled water. Hydrogen yield of aluminum alloys increased with increasing alloy content and the highest values were obtained from Al 7075 powders in NaOH solution. It was also verified that the hydrogen yield increases with increasing reaction temperature.

One-part eco-cellular concrete for the precast industry: Functional features and life cycle assessment

This paper focuses on investigating greener alternatives of cellular concrete technology to fulfil current searches for a shift to circular economy. A novel one-part eco-cellular concrete (ECC-OP) was developed and studied. The one-part alkali activated materials (AAM-OP) and new alkali-activated cellular concrete (AACC) technologies were combined to develop greener alternative of cellular concrete production. The progressive steps from traditional cellular concrete (TCC) based on ordinary Portland cement (OPC) and commercial aluminium powder (A) to a 100% waste-based cellular concrete are presented. Blast furnace slag (BFS) was the precursor, RHA was employed as the silica source, olive stone biomass ash (OBA) was the alkali source and recycled aluminium foil (AR) was employed as an aerating agent. The functional features of the materials were studied and compared to those established by the European standard and the American Concrete Institute (ACI) Committee 523 guides. The new ECC-OP with a bulk density, compressive strength and thermal conductivity that respectively equal 660 kg/m3, 6.3 MPa and 0.20 W/mK was obtained. Finally, a cradle-to-gate life cycle assessment (LCA) was made, where the industrial process of a masonry unit manufacture was raised by using each studied material. A 96% reduction in the kgCO2eq per m3 of material was reached with the new proposed ECC-OP compared to TCC manufacturing.

Decompression stripping of carbon dioxide from rich monoethanolamine through porous hydrophobic modified ceramic hollow fiber membrane contactor

In this study, commercial alpha alumina powder was used to fabricate hollow fiber membrane by phase inversion spinning method. The fabricated alumina hollow fiber membrane was confirmed to have high chemical and thermal stability based on thermogravimetric analysis and contact angle measurement. When CO2 stripping characteristics were examined by introducing decompression membrane contactor process in the stripping part of amine absorption process, increase in degree of vacuum resulted in increased CO2 stripping flux. In liquid to lumen operation under decompression pressure of 61.325 kPa and absorbent flow rate of 9 ml/min, CO2 stripping flux was 45.75 × 10−4 mol/m2·s. Existing articles on membrane contactor stripping were mostly N2 sweep type and reported CO2 stripping flux of 1–24 mol/m2·s, whereas the present study achieved stripping performance that was approximately 2–40 times higher. Decompression stripping of porous ceramic hollow fiber membrane contactor can be viewed as a promising process since it did not cause the phenomenon of decrease in CO2 purity due to N2 and showed similar or greater CO2 stripping flux than previously reported membrane contactor stripping processes.

Microstructure and Mechanical Behaviour of ABOw Reinforced Aluminium Matrix Composite Synthesized by Powder Metallurgy route

In present study, the effect of Aluminum borate whiskers (ABOw) content (5, 10 and15 wt.%) on the development of Al-ABOw composite using powder metallurgy route has been investigated. Firstly, Aluminum borate whiskers (ABOw) were produced using sol-gel method. The commercial pure aluminum powder was used as matrix material in this investigation. Amongst, the various casting technology, the powder metallurgy route is most economical and extensively used by researchers. The microstructures of composites were observed using optical microscopy (OM), scanning electron microscopy (SEM). Transmission electron microscopy (TEM) analysis was performed for the observation of ABOw powder morphologies. The XRD analysis was carried out to confirm the phases and peak intensity of developed alloy and composites. The sintering was carried out at 600°C for all samples. After that, the bending test was carried out to calculate flexural strength of alloy and composites. The flexural strength 172±5 MPa was obtained maxima in composite with 10 wt.% ABOw along with improved hardness around 40.2HV. The result shows that, the composite exhibited better interfacial bonds, uniformity in microstructure and optimum flexural strength.

Development of non-shrinkable ceramic composites for use in high-power microwave tubes

Al2O3-CaO-SiC-based ceramic composites with four different compositions were sintered at 1700°C for 3 h in an air furnace. The phase analysis, microstructural characterization, and elemental composition determination of the developed composites were performed by X-ray diffraction (XRD), field-emission scanning electron microscopy (FESEM), and energy-dispersive X-ray (EDAX) analysis, respectively. The shrinkage, thermal properties, and electrical resistivity of the composites were also studied. The experimental results showed the effects of adding silicon carbide and calcia to alumina on the thermal, electrical, and shrinkage properties of the resultant composites. Among the four investigated ceramic composites, the one composed of 99wt% alumina, 0.5wt% CaO, and 0.5wt% SiC exhibited the best characteristics for use as a potting material in a dispenser cathode of a microwave tube. The material exhibited slight expansion instead of shrinkage during drying or firing. Other properties of the composite powder, such as its thermal properties and electrical resistivity, were comparable to those of a commercial alumina powder.

EXPERIMENTAL INVESTIGATION OF P/M PARTS MANUFACTURING CONDITIONS USING AA2014 AND ELEMENTAL AL AND CU POWDERS

Bu çalışmanın amacı, iki farklı AA2014 toz grubundan (önalaşımlı, elementel formda) elde edilen numunelerin mekanik test sonuçları, kırık yüzey analizi ve metalografik çalışmalarını karşılaştırarak, elementel tozun kullanımıyla elde edilen değerlerin tasarım malzemesi olarak yeterli mekanik özelliklere sahip olup olmadığını belirlemeye çalışmaktır. Ön alaşımlı (AA2014), elemental alüminyum ve bakır tozları kullanılarak klasik toz metalurjisi (TM) yöntemiyle numuneler üretilmiştir. AA2014 alaşımının içerdiği oran kadar, ticari saf Alüminyum tozuna bakır eklenmiş ve dökümde soğuk presleme yapılmıştır. Benzer koşullarda, ön alaşımlanmış (AA2014) tozlar ve element tozlarından benzer bir bileşim elde etmek için harmanlama ve karıştırma işlemleri gerçekleştirilmiştir. Sinterleme koşulları olarak, üç farklı sıcaklık (600°C, 610°C, 620°C) kullanılmış ve sinterleme süresi sabit tutulmuştur (30 dakika). Bu aşamada, alüminyum matriksinin katı çözeltiler oluşturmak için Bakır atomlarını çözmesi beklenir. Bu durumun gerçekleşmesini incelemek için metalografik çalışmalar yapılmıştır. Sonuç olarak, alüminyum ve bakır tozu, uzun bir kalıp ömrü için alaşımlı AA2014 yerine elemental olarak kullanılabilir.

Microstructure and optical properties of alumina sintered from various phases

Self-synthesized and commercial alumina (boehmite, γ-Al2O3, α-Al2O3) powders were consolidated using an identical spark plasma sintering cycle, and optically translucent samples were obtained. The benefit of higher pressure is remarkable grain growth suppression. Additionally, the shorter dwell time at higher pressure advantageously leads to a reduction in grain size while conserving the optical transparency and without affecting the density.

Morphology Studies on Mechanically Milled Aluminium Reinforced with B4C and CNTs

Carbon nanotubes (CNT) with exceptional mechanical and physical properties are the prime candidate materials for metal matrix composites. But the dispersion of CNTs in the metal matrix is affected by attractive van der Waals forces. In this study, we have adopted ultrasonication and mechanical alloying to achieve homogenous dispersion of multiple reinforcements namely B4C and CNTs within the commercial purity aluminium powder. The ultrsonication of all the starting materials was followed mechanical alloying process which was carried out in a planetary ball mill up to 480 min. The milling process was systematically studied by taking a small amount of milled powder at different milling time of 60, 120, 240 and 480 min respectively. The effect of ultrasonication and mechanical alloying on both morphology of the powders and dispersion of B4C and CNTs was studied using scanning electron microscopy. The results showed uniform dispersion of both B4C and CNTs within the pure aluminium powders without any agglomeration. Both the pure aluminium and hybrid nanocomposite powder showed decrease in particle size from 20.89 µm to 5.67 µm and 2.72 µm respectively after 480 minutes of ball milling.

Structural, morphological and electrical properties of alumina/YAG composites as solid electrolyte for IT - SOFC

Alumina/YAG composites (AYX_t) with high relative density (99.2 %TD) were successfully obtained by mixing commercial alumina powder with different volume fractions of yttrium aluminium garnet (Y3Al5O12-YAG; 7, 14, 21 and 28). YAG was synthetized by nitrate glycine reaction in the form of precursor powder. Polycrystalline YAG powder was obtained by calcination at 950?C for 2 h. Additionally, obtained compositions were characterized by XRD, SEM, EDX and electrochemical impedance spectroscopy. By XRPD analysis was found that the particle size of YAG powders lies in the nanometric range (being lower than 35 nm). By SEM microphotographs of composites were confirmed the formation of a conductive path consisting from mutually interconnected YAG particles. This was confirmed by the electrochemical impedance spectroscopy. The highest electrical conductivity of grain (?g) and grain boundary (?gb) at 700?C amounted to 2.22?10-2 ?-1cm-1and 9.44?10-3 ?-1cm-1, respectively, was measured in the composite containing 21 vol% of YAG.

Phase variation and thermophysical properties of La2Hf2O7 with alumina addition

La2O3-Al2O3-HfO2 ceramics were prepared by solid reaction of La2Hf2O7 ceramic powders which were synthesized by solution combustion and commercial alumina powders at 1600°C in air for 10h. Phase variation and thermophysical properties of La2O3-Al2O3-HfO2 ceramics were investigated. With the increase of alumina content, LaAlO3, HfO2 and LaAl11O18 phase structures appeared. The thermal expansion coefficients gradually increased with the increase of alumina content from 1000°C to 1300°C. The thermal conductivities of La2O3-Al2O3-HfO2 ceramics had nonlinear variation with the increase of alumina content and reached the lowest value around 1.1W·m−1·K−1 when the ratio of La2Hf2O7 to Al2O3 was 1:0.25. Therefore, the La2O3-Al2O3-HfO2 ceramics with a proper content of alumina can be considered as a new thermal barrier materials. Meanwhile, as potential application as interface layer in TBC, La2O3-Al2O3-HfO2 ceramics are beneficial to improve the effectiveness of the thermal barrier coating.

Geopolymer eco-cellular concrete (GECC) based on fluid catalytic cracking catalyst residue (FCC) with addition of recycled aluminium foil powder

This study presents a new cellular concrete design focused on the energy eco-efficiency and the sustainability concept: geopolymer eco-cellular concrete (GECC). Geopolymer systems made from alkali-activated fluid cracking catalyst residue (FCC) aerated by recycled aluminium foil powders (R) were designed. Commercial aluminium powder (A) was also used as an aerating agent in GECC matrix and its effect was compared with traditional cellular concrete (TCC) made with ordinary Portland cement (OPC). The more alkaline medium of the GECC system improved the hydrogen reaction rate and consequently a higher efficiency in the pore matrix development can be found. Aluminium powder addition of 0.2% by mass of the precursor (FCC) was enough to yield cellular concrete with a natural density significantly lower than that found for TCC. The replacement of A by R made it possible to produce an alternative GECC in which the recycling of the waste aluminium has an important eco-efficiency role because its low cost and its energy saving function. Ground R has less aeration effectiveness than A. However, when co-milling of FCC + R was carried out, advantageous performance GECC was attained. Very interesting properties were obtained for this material: good pore size and its proper distribution in the matrix, low natural density (600–700 kg/m3), relatively high compressive strength (2.5–3.5 MPa), low open/closed porosity ratio (1.15) and the lowest thermal conductivity (0.581 W/mK). This opens an interesting way of reusing both FCC as precursor and aluminium foil waste as an aerating agent in the preparation of new geopolymer eco-cellular concrete (GECC).

Industrial Sintering Response and Microstructural Characterization of Aluminum Powder Metallurgy Alloy Alumix 123

In this work, the industrial sintering response of the commercial aluminum powder metallurgy alloy ‘Alumix 123’ has been examined and the resulting microstructure investigated by optical microscopy, scanning electron microscopy, energy-dispersive x-ray spectroscopy, and x-ray diffraction. Alumix 123 is similar in composition to wrought aluminum alloy 2014 and was revealed to develop a sintered density of 92% of theoretical using standard practices for industrial sintering. Microstructural investigations proved that as a result of industrial sintering, a number of embrittling iron-containing intermetallics are developed in addition to the desirable copper-rich intermetallics. To improve the density of sintered components, procedures were developed for secondary processing by ‘sizing’ (repressing) in a laboratory setting. The results showed that sizing to the industry standard reduction in height of 5% only closed a portion of open surface porosity and that higher sizing pressures should be used in applications that are sensitive to this microstructural feature.

Effect of temperature and holding time on the densification of alumina obtained by two-step sintering

Abstract The two-step sintering technique is a process of controlling the sintering curve, which provides materials with higher density and smaller grain size when compared to conventional sintering. This technique was evaluated by optical dilatometry with three commercial alumina powders of different purity (92, 96 and 99 wt% of Al 2 O 3 ) and particle size (between 0.73 and 2.16 µm). Different sintering conditions in the first (temperature, T1) and second (temperature, T2, and holding time, t2) steps were studied in order to evaluate the effect of these variables on densification and grain growth. Considering T1 as the temperature at which a relative density (D rel ) of 83% was achieved, and for the range of conditions tested, it was found that higher D rel values and lower grain size of alumina were obtained with higher T2 and lower t2. Alumina with 99 wt% purity sintered at T1 of 1550 °C for 5 min and T2 of 1500 °C for 4 h showed the best relationship between higher densification (~96% relative density) and reduced grain size (0.94±0.15 µm). Thus, this work demonstrated that suppression of grain growth can also be obtained for commercial alumina.

Combustion of Metallurgical Wastes Using Secondary Aluminum Foils

ABSTRACTSimulating the reactions in a complex system can lead to self-sustaining and energy efficient treatment of wastes in recycling promoting manner. In this contribution, the synergic combination of electric arc furnace dust (EAFD), mill scale, and secondary aluminum, in a form of waste foil, was researched aiming to use exothermal energy of reactions and to obtain environmentally favorable products. The secondary aluminum in the form of foil was prepared in different ways in order to develop aluminum surface and to be suitable for aluminothermic reactions. The commercial aluminum powder was used to determine optimal conditions using full factorial experiment design. After that, research was performed on aluminothermic reactions with the aluminum powder obtained from secondary aluminum foils. Results show that the secondary aluminum can be successfully used for a treatment of oxides bearing hazardous wastes in an energy efficient and environmentally friendly manner. The comparative life-cycle assessment revealed several advantages of using the secondary aluminum foil as a reduction agent compared to the conventional recycling of the secondary aluminum foil.