Aluminum Powder Research Articles

Enhancing powder bed fusion of alumina ceramic material: a comprehensive study from powder tailoring to mechanical performance evaluation

Powder bed fusion (PBF) is an additive manufacturing (AM) technique that holds a great promise for alumina ceramic materials to be processed in a one step. To ensure an effective outcome, the powder material should be thoroughly tailored, and the process parameters should be appropriately investigated. These process parameters include laser power, scanning speed, hatching space, and scanning strategies. The alumina powder has been tailored and modified to be appropriately used for PBF using the spray-drying technique, and the process parameters have been predicted and selected using a developed numerical model. Different scanning speeds of 100, 200, 300, and 400 mm/s have been considered, and the other parameters have been numerically predicted. The results demonstrated that spray drying is an effective technique for tailoring the characteristics of alumina powder, such as particle shape, particle size distribution, flowability, and absorptivity, making it ideally suited for PBF processing. Furthermore, the developed numerical model demonstrated outstanding reliability in predicting the most effective laser power and hatching space for different scanning speeds, resulting in significant cost and time savings when compared to relying solely on experimental trials. Employing a scanning speed of 400 mm/s yielded a significant improvement in relative density and quality of the printed samples surpassing other scanning speeds. Moreover, this speed effectively addressed various challenges encountered by other scanning speeds. Following the optimization of process parameters, it was determined that a relative density of 94.5% could be achieved by utilizing a scanning speed of 400 mm/s, a laser power of 210 W, and a hatching space of 30 µm. However, the evaluation of mechanical performance revealed that while the microhardness of the printed alumina samples matched the values reported in the literature, the attained compressive strength fell significantly below the values reported in the literature.

Preparation and Characterization of Novel Sulfoaluminate-Cement-Based Nonautoclaved Aerated Concrete.

The production of autoclaved aerated concrete via the autoclaving process incurs substantial energy consumption, posing a challenge to sustainable economic development. Herein, a novel nonautoclaved aerated concrete (NAAC) was prepared using sulfoaluminate cement as the primary raw material and aluminum powder as the aerating agent. The physicomechanical characteristics and pore structures of the sulfoaluminate-cement-based (SAC) NAAC (SAC-NAAC) were examined through X-ray diffraction, thermogravimetry, and scanning electron microscopy. The findings revealed that the optimal mechanical attributes of the SAC-NAAC were achieved at a water-cement ratio of 0.55, with a specific content ratio of polycarboxylate superplasticizer-borax-calcium stearate-sodium hydroxide at 0.24%:0.32%:0.36%:2.90%, along with 0.40% aluminum powder. The SAC-NAAC samples, with a bulk density range of 600-750 g/m3, exhibited a compressive strength of 3.55-4.16 MPa, porosity of 45.9-63.5%, and water absorption rate of 60.2-74.4%. The weight loss in the SAC-NAAC with different aluminum powder contents ranged between 15.23% and 16.83%. The prismatic ettringite (AFt) crystals served as the main source of strength for the SAC-NAAC, and AH3 was attached to the AFt surfaces in a microcrystalline gel phase, thereby further enhancing the strength of the SAC-NAAC. Thus, the lightweight, high-strength SAC-NAAC has great potential as a nonautoclaved aerated concrete.

Prediction of Phase Composition and Process Resilience in Plasma‐Assisted Hetero‐Aggregate Synthesis using a Machine‐Learning Model with Multivariate Output

AbstractThe synthesis of nanoscale particles and particle aggregates from liquid or gaseous precursors is affected by a variety of trade‐off relations, for example, in terms of product composition, yield, or energy efficiency. Machine‐supported process evaluation and learning (ML) of these relations enables optimization strategies for advanced material processing. Such a workflow is demonstrated on the example of plasma‐assisted aerosol deposition (PAAD) of alumina powders. Depending on processing conditions, these powders comprise of hetero‐aggregate mixtures of crystalline and amorphous polymorphs. Process optimization toward a specific target composition calls for ML approaches. For this, a sufficiently large and consistent dataset of PAAD input (processing) and output (product) parameters is initially generated by real‐world processing, and subsequently extrapolated into a cloud of ≈106 input‐output parameter matrices using Gaussian process regression with multivariate output and input‐output feature analysis. It is subsequently demonstrated how not only the phase composition of the obtained alumina powders, but also product resilience to variations in specific processing parameters, or – as a perspective – the energy efficiency of material processing can be predicted.

Influence of particle size and aggregates on translucent alumina ceramics fabricated by gelcasting

Three types of alumina powders and a polymer electrolyte Isobam system were used to fabricate translucent alumina ceramics via gelcasting, and each powder had the highest attainable solid loading. The effects of alumina particle size on slurry dispersion, microstructures and properties of green bodies and ceramics were investigated. All of the high-solid loading slurries contained strong aggregates, which could bridge with each other to form weak agglomerates. The smaller the initial particle size was, the more the contained particle number per aggregate. In addition, the smaller the aggregate size was, the lower the sintering activation energy of the ceramic and, finally, the higher the relative density. The initial particle size of the powder may not be the critical factor determining ceramic sintering, but the aggregate size and effective volume fraction of the aggregates may be the critical factors. Finally, the in-line transmittance of the ceramic with a higher density reached 22% at a wavelength of 650 nm and a thickness of 0.8 mm.

Glass-based sealants for joining α to β’’-Al2O3 in Na–Zn batteries

This study deals with the design and the characterisation of glass-based materials for the hermetic sealing of ceramic components (α-to β’’-Al2O3) in solid-electrolyte cells operating at approximately 300 °C. A silica-based commercially available glass and a newly developed silica-free glass, potentially resistant to corrosion by molten sodium salts, are reviewed and discussed. 25 wt% alumina powder is incorporated into both formulations. The sintering behaviour of the glass systems and their wetting characteristics on alumina are evaluated at the selected sealing temperatures: 900 °C for 40 min (for the silica-based system) and 700 °C for 1 h (for the silica-free system). The viscosity of both glass systems at these temperatures, which is approximately 105 Poise, is deemed suitable for facilitating proper glass flow and bonding with the alumina components. Furthermore, the coefficient of thermal expansion (CTE) of the potential sealant candidates is investigated. The results demonstrate good compatibility between the glass-based systems (CTE ≈ 7–7.6· 10−6 K−1 at temperatures ranging from 100 to 300 °C) and α- and β’’-Al2O3 (CTE ≈ 7.3· 10−6 K−1 within the same temperature range). The microstructural analysis conducted using field-emission scanning electron microscopy (FE-SEM) confirms good thermo-mechanical matching between the glass-based sealants and the alumina ceramic components and that no reaction occurs during the sealing between alumina powder and the glass matrix.

Preparation of autoclaved-aerated concrete with waste ash of petroleum coke gasification

ABSTRACT In this paper, a novel route for the utilisation of petroleum coke gasification ash in the preparation of autoclaved-aerated concrete (AAC) is presented. The waste ash along with quartz sand, cement, lime, and gypsum are used as the primary raw materials, with aluminium powder paste serving as the pore-forming agent. The effect of incorporating petroleum coke gasification ash on the dry density and thermal conductivity of the resulting AAC was investigated. The results indicate that the thermal insulation performance of AAC is significantly enhanced by reducing the thermal conductivity coefficient upon the addition of treated petroleum coke gasification ash. At a 40% ash content, the AAC exhibits remarkable performance that meet the requirements of A2.5B05 in GB 11,968-2006, with compressive strength higher than 2.5 MPa and dry density lower than 525 kg m−3. Furthermore, the study examined the optimal calcium silicon ratio after the addition of the ash, with the results demonstrating that AAC prepared with a ratio of 0.25–0.26 exhibits the best compressive strength and dry density. The present study offers a novel perspective on waste management, which carries substantial significance for both the environmental and construction industries.

Improvement of the Hydrogen Storage Characteristics of MgH2 with Al Nano-Catalyst Produced by the Method of Electric Explosion of Wires.

A new composite with a core-shell structure based on magnesium hydride and finely dispersed aluminum powder with an aluminum oxide shell was mechanically synthesized. We used magnesium chips to produce magnesium hydride and aluminum wire after exploitation to produce nano-sized aluminum powder. The beginning of the hydrogen release from the composite occurred at the temperature of 117 °C. The maximum desorption temperature from the MgH2-EEWAl composite (10 wt.%) was 336 °C, compared to pure magnesium hydride-417 °C. The mass content of hydrogen in the composite was 5.5 wt.%. The positive effect of the aluminum powder produced by the electric explosion of wires method on reducing the activation energy of desorption was demonstrated. The composite's desorption activation energy was found to be 109 ± 1 kJ/mol, while pure magnesium hydride had an activation energy of 161 ± 2 kJ/mol. The results obtained make it possible to expand the possibility of using magnesium and aluminum waste for hydrogen energy.

Thermal enhancement of the oxidation layer of micron-sized aluminum powder and its anti-oxidation performance

Micron-sized aluminum powder, with its typical core-shell structure, exhibits oxidation behavior upon slow heating in an oxidative atmosphere that is related to the particle size of the aluminum powder. A particle size-dependent thermal response mechanism for micron-sized aluminum powder is established: a "shell-breaking eruption" thermal response mechanism. The oxide layer is thermally enhanced, and the anti-oxidation reaction behavior mechanism of the enhanced samples is studied. Aluminum powder samples, heated slowly to specific temperatures to obtain changes in the oxide layer structure, are analyzed using a thermal analyzer to compare the slow heating response behavior of aluminum powder before and after the oxidation layer changes. It was found that after thermal enhancement of the aluminum powder oxidation layer, which changed from amorphous to γ-phase and whose thickness increased to twice the original thickness, the slow oxidation process of micron-sized aluminum powder was inhibited, and the aluminum powder was completely deactivated in the slow heating response.

Reaction mechanism of micron-sized aluminum powders in O2 and CO2 gradually heated environment

The behavior of aluminum powders in specific oxidized environment is different from each other obviously. Thermal behaviors of micron-sized aluminum powders in different oxygenated and gradually heating environments were discussed in order to find out the oxidation mechanism. Particular attention is paid to the reaction mechanism of oxygen and carbon dioxide atmosphere. Thermogravimetric analysis and related characterization methods are used and the results demonstrated that under the certain condition, reaction process of micron-sized aluminum powders can be divided into four stages. General routes for the oxidation of micron-sized aluminum in general heating system are the same, however, itis different among the extent of reaction at the third stage in different kinds of oxidizing gas atmospheres. Gas phased products were detected during the main reaction stage under carbon dioxide by combining thermal analysis and mass spectrometry which contributes to the rupture of alumina shell and further reaction of micron-sized aluminum powders. Consequently, rapider and more complete reaction process was achieved. The increasing thickness of original alumina shell can restrict the reaction rate of aluminum powders harder at the same time.

Study on the oxidation mechanism of micron- and nano-sized aluminum powders influenced by alumina shell

Thermal behaviors for aluminum particles at oxidative atmosphere gradually heating system were discussed. Heating micron- and nano-sized aluminum powders from room temperature to 1400℃ using thermal analysis method. The results showed that the reaction process for micron-sized aluminum particles can be divided into four stages which include the phase change of oxidized shell, increasing thickness of alumina shell, main broken shell oxidizing process and the phase change of alumina shell in high temperature. Thermal analysis for micro aluminum particles was carried out with shell thickness adjustments via ambient manual means. It turned out that the oxide layer thickness would have full limitation effects on the slow oxidation for micro aluminum particles with shell structure when it was increased above twice of the original thickness. The limitation effects of oxide shell thickness on the heating processes in gradually heating system were proposed. Humidity environment can make the thickness of alumina increase in a certain range when the particles are in nano-scale. Complete oxidation processes were observed but an increase of the oxidation temperature was identified.

Solid-state production of uniform metal powders for additive manufacturing by ultrasonic vibration machining

This work presents a new technique to generate uniform and micron-sized metal powders for additive manufacturing. By collecting discrete chips resulting from ultrasonic vibration machining, we demonstrate the feasibility of all solid-state production consistent powders with tight dimensional tolerance, the ability to control powder geometry, and good efficiency. The technique offers a new route for sustainable and low-cost manufacturing of high-quality metal powders. The powder generation mechanism is analyzed with a special tool path design to ensure consistent dimensions over multiple cuts. An analytical model to predict the dimensions of produced powders under different cutting parameters is introduced. Aluminum and brass powders of different dimensions are produced, and the overall shear ratio that governs the deformation during the machining process is calibrated with the experimental results. The morphology consistency of produced powders is investigated over multiple hours of production, illuminating the role of tool wear on final powder shape. A high-efficiency powder collection system and a scalable solution for parallel production are proposed for the introduced technique. Additive manufacturing experiments (laser powder bed fusion) are conducted using produced A356 aluminum powders, demonstrating the printability of produced powders in additive manufacturing. The microhardness of the printed parts for five different process parameters is measured to be 45% higher than the raw material on average.

Experimental investigation on the suppression of aluminum dust explosion by sodium carbonate powder

To prevent the potential explosion accidents in industries involving aluminum powder, the effectiveness of Na2CO3 in inhibiting aluminum dust explosions was investigated using thermal methods and explosion tests. Furthermore, the surface morphologies and chemical compositions of the resultant explosion products were characterized to illustrate the inhibition mechanism of Na2CO3 powder. The results revealed a marginal increase in ignition temperatures and a decrease in combustion peak temperature as the proportion of Na2CO3 increased. Notably, within the range of 0–450%, a notable reduction was observed in both the maximum explosion pressure (from 0.68 to 0.06 MPa) and the maximum pressure rising rate (from 91.93 to 2.87 MPa/s). In particular, as the percentage of Na2CO3 increased, a gradual decrease in flame brightness and average flame velocity was observed. Moreover, a negative relationship was observed between ignition temperature and apparent activation energy with maximum explosion pressure and maximum pressure rising rate. An analysis of the explosion residues indicated the presence of Na2CO3, NaOH, Al2O3, Al(OH)3, Na(AlO)2, Na2O and unburned aluminum. The inhibition mechanisms of Na2CO3 involved heat absorption, isolation, and the consumption of free radicals. These results offer valuable insights that can aid in mitigating the risks associated with aluminum dust explosion.

Utilization of Cement Power Plant Beds for Aerated Concrete Thermal Blocks

<p>Nowadays cement industry power plant bed wastes can be used to create aerated concrete blocks for widespread usage in the construction sector instead of sand. The optimum materials for building enclosures for a variety of uses include aerated concretes. To enhance the physical and mechanical qualities of Non-Autoclaved Aerated Concrete (NAAC) blocks, bed material is introduced in this study as a superior alternative material. The non-autoclaved concrete blocks in this study are made with cement, bed materials, fly ash, gypsum, and a consistent amount of 0.65 grams of aluminium powder. The mix preparation and method employed for manufacturing NAAC blocks, the composition of mix specimens and the dosing and mixing processes have been expounded upon, shedding light on the critical steps in the production. According to the suggested method in IS 2185 (Part III) of 1984, the proportion of bed materials was taken by volume of compacted dry material for NAAC of Size 22cm x 10.5cm x 7cm. Experiments into the NAAC block's compressive strength plus water absorption of the bed materials were followed by comparisons of these characteristics with clay and fly ash bricks sold in the market. As a result, NAAC blocks met the 6 MPa strength criteria specified by Indian Standard code IS2185 (Part III): 1984. However, the strength of the aforementioned NAAC brick at 28 days was 7.28 MPa for Sample T5. A more in-depth presentation of the testing methods, focusing on the compressive strength tests was conducted at various intervals (7, 14, 21, and 28 days). The density values and water absorption rates for each test sample (T1 to T5) are now presented with additional insights into the observed trends. According to the research, blocks manufactured with NAAC bed materials tend to be stronger and lighter than those made with conventional clay bricks. They also produce non-autoclaved concrete blocks. Therefore, the creation of such inexpensive blocks can be employed for extensive production.</p>

Investigation of Mechanical and Wear Behaviour of Al5056-Carbon Nanotube -Graphene Hybrid MMCs using Powder Metallurgy Route

Composites containing metal at least in two constituent parts are metal matrix composites. Another material may also be used like organic compounds or ceramics, in addition to a different metal. In the current work Al5056 aluminium powder is used as the matrix material having an average particle size was about 35±5 μm and Carbon Nanotube (CNT) and Graphene (Gr) are used as reinforcement materials. Hybrid composites are developed using an advanced powder metallurgy technique process. Also, in the existing work microstructure characterization was performed using advanced techniques. Hardness, Tensile and wear tests are conducted as per ASTM standards. Mechanical properties improved with the increase in amalgams in the matrix. The wear surface morphology of Al alloy shows a rough surface with more grooves and ridges compared to the wear surface morphology of Al5056/CNT-Gr hybrid composites. Wear debris results of Al alloy show more debris chips out of the material compared to Al5056/CNT-Gr hybrid composites.

Application of microencapsulated fibrous carrier inhibitors in suppressing flake aluminum dust explosion: Performance and mechanism

Flake aluminum powder (FAl), due to its larger specific surface area and higher reactivity, posing a potential threat to the process safety of involved enterprises. To mitigate the explosion caused during the production of FAl, a green composite inhibitor, Sep@CS@PA-Na, was successfully prepared in the aqueous phase using microencapsulation technology with sepiolite (Sep), chitosan (CS), and sodium phytate (PA-Na) as raw materials. The suppression of FAl explosions in a vertical combustion duct system by inhibitors with different inerting ratios (α) was investigated. The results showed that after adding Sep@CS@PA-Na with an α of 0.75, the maximum flame propagation velocity (Vmax), the average flame velocity (Vavg), and the velocity of the flame reaching the pipeline top (Vtop) decreased by 79.6%, 75.1%, and 86.2%, respectively, and the reduction of the maximum flame front pressure (Pmax) and the maximum flame pressure rise rate ((dP/dt)max) were 90.4% and 89.8%, respectively, and the peak temperature (Tp) dropped to 505°C. Combined with TG-DSC and explosion product analysis, Sep@CS@PA-Na possessed both gas-phase reaction and surface reaction suppression functions, which were mainly reflected in the dilution effect, quenching effect, and barrier effect. This work will provide technical support for the emergency prevention and control of energetic metal dust explosions.

An enhanced DPC model for metal powder incorporating yield strength of solid-state

The Drucker-Prager/Cap (DPC) Model has a significant drawback in metal powder metallurgy simulations, which is the potential for the von Mises stress to exceed the yield strength of the solid state. To address this issue, this paper introduces a novel hardening law that effectively restricts the von Mises stress within the yield strength of solid alloy. As the powder becomes denser, the yield surface of the DPC model gradually approach towards the von Mises yield surface. To validate the proposed model, both micro-scale finite element simulations and published experimental data were used. The effectiveness of the proposed model was demonstrated through its application in the simulation of two scenarios: cold die compaction of aluminum powder and hot isostatic pressing of a Nickel based superalloy. The results indicate that the proposed model outperforms the original DPC model and is more suitable for powder metallurgy simulations.

Pore structure regulation of aluminum powder as a filler for high energy solid propellants

Aluminum (Al) powder, as a high-energy metal combustible agent, has advantages such as high calorific value and low cost. It has important research value in energetic materials. However, due to the Al2O3 layer on the surface of Al powder, the contact area between Al powder and oxidant components is reduced, resulting in a decrease in its energy release performance. In this paper, a modified Al powder with porous structure was prepared by chemical corrosion method to solve the problem that its small contact area with oxidant components affects its energy release performance. The study found that when the concentration of HF solution is 3.0 wt%, the removal effect of the oxide layer of Al powder is most effective, with a surface O element content of only 0.6 wt% and a uniform porous structure on the surface of Al powder. In addition, experiments have shown that nano CuO can be well filled into the pore structure of modified Al, increasing the contact area between Al powder and oxidant. This work provides a novel and simple research approach for effectively improving the energy release performance of Al based energetic materials.

Effect of Source Type on Pore Structure and Properties of Aerated Geopolymer Concrete

A study has been carried out to produce environmentally friendly lightweight concrete by substituting cement with alternative geopolymer binders. Fly ash and silica fume (waste materials) were used as source materials and their effect on pore structure and properties of aerated geopolymer concrete was evaluated. Autoclaved aerated concrete, locally known as thermostone, was supplied from the market and tested as a reference mix. Three aerated geopolymer concrete mixes (around 550 kg/m3 density) were produced by mixing source materials (fly ash and silica fume), activator solution (sodium silicate and sodium hydroxide), and aeration agent (aluminum powder). It was found that by not only enhancing the pore structure but also improving the binder medium, the aerated geopolymer mixes were stronger and less absorbed than the autoclaved aerated concrete mix. However, the thermal insulation of the aerated concrete mix was better than those of aerated geopolymer concrete mixes. In terms of the source material, it was found that usage of fly ash helped in enhancing the strength by about 100% of autoclaved aerated concrete. In addition, unless its lowest density, aerated geopolymer mix made with fly ash and silica fume in combination absorbed less water than the other investigated mixes. Adding superplasticizer to the geopolymer mix helped in enhancing its pore structure by making the pores smaller, their irregularity lesser, and their number higher. In general, an environmentally friendly lightweight material with strength and absorption better than those of autoclaved aerated concrete was produced by adopting a geopolymerization process.

Efficient and eco-friendly cadmium ion recycling: Ultrasonic enhancement of aluminum powder replacement for low-temperature industrial applications

Replacing cadmium ions in cadmium-containing solutions with aluminum powder is beneficial for cadmium resource recycling and environmental protection. However, the conventional aluminum powder replacement method requires harsh temperatures and prolonged conditions. In this study, the effect and mechanism of ultrasound on the replacement of cadmium with aluminum powder were investigated at low temperatures. Ultrasound has been proven to promote the etching of alumina films through the use of TEM and XPS, providing mechanistic support for the superiority of the new process. A degree of Cd replacement as high as 95.08 % is achieved at a low temperature (60 ℃) and in a short time (20 min) when using ultrasonicated aluminum powder replacement, which is 42.17 % higher than that of conventional aluminum powder. Compared with conventional aluminum powder replacement conditions with the same effect, the introduction of ultrasound can reduce the temperature by 30℃ and shorten the replacement time by 2/3, which has significant advantages in reaction efficiency and safety. The strengthening mechanism of ultrasound on the replacement effect of aluminum powder at low temperatures is revealed through detailed discussions on the corrosion of alumina films, agglomeration of aluminum powder, and adhesion of replacement products to the surface of aluminum powder, dissolved oxygen in the solution, and redissolution of cadmium. Therefore, a new approach for replacing aluminum powder in solutions with high Cd2+ concentrations at low temperatures is proposed in this work, which is expected to solve the existing harsh and dangerous problems of industrial aluminum powder replacement.

Effect of microstructure on functional force and air explosion performance of CL-20-based aluminum-containing explosive

A solvent–non-solvent approach was used to create a CL-20-based aluminum-containing explosive with a composite structure. The SEM results demonstrate that the aluminum powder is equally embedded on the surface of the CL-20 crystal in the CL-20/Al explosive with a composite structure but the aluminum powder in the mechanically mixed CL-20/Al explosive is agglomerated and spread unevenly. The maximum expansion velocity of the composite structure CL-20/Al explosive was 17.74% higher than that of the mechanically mixed explosive in the cylinder test, and the acceleration ability of the CL-20/Al explosive with a composite structure to the cylinder wall is superior to that of the mechanically mixed explosive. In the air explosion test, the shock wave overpressure and impulse of the CL-20/Al explosive with a composite structure are superior to those of the mechanically mixed explosive, but as the distance increases, the gap between the two explosives gradually narrows until it is flat. The results of interfacial particle velocity show that the length of the reaction zone and duration of CL-20/Al explosives with composite structures are longer than those of mechanically mixed structures, and the interfacial particle velocity of CL-20/Al explosives with composite structures is higher than that of mechanically mixed structures.