Micron Aluminum Research Articles

Preparation and Performance Study of Thermally Conductive Silicone Adhesive Applying in Flip Chip Ball Grid Array

A thermally conductive silicone adhesive UB-5715 was prepared using vinyl silicone oil of medium viscosity, hydrogen-containing silicone oil and micron alumina powder. The results revealed that UB-5715 demonstrated superior thermal and mechanical properties. Specifically, its thermal decomposition temperature exceeded 400 °C, the thermal conductivity coefficient surpassed 1.80 W/m·K, the thermal resistance was under 12.0 °C·cm2/W, the shear strength reached achieved was over 5.00 MPa. Meanwhile, after being subjected to uHAST for 384 hours, thermal cycle for 1000 times and heat aging for 1000 hours respectively, UB-5715 still maintained its high thermal conductivity coefficient and mechanical properties. The thermal conductivity coefficient still exceeded 1.70 W/m·K, shear strength still surpassed 5.00 MPa, the tensile modulus remained below 100 MPa, the linear expansion coefficient was less than 160 ppm/°C, and its comprehensive performance met the reliability requirements for advanced packaging process substrates and heat dissipation cover assemblies.

A durable superhydrophobic surface with bud-particle structure prepared by one-step spray method

Superhydrophobic surfaces play an essential role in numerous applications such as anti-fouling, waterproofing, and drag reduction due to their water-repellent. However, for most fabrication methods, there are high requirements for the preparation process and conditions. Meanwhile, the superhydrophobic surfaces generally have the problem of insufficient durability. In this study, a one-step method to fabricate a stable superhydrophobic surface by spraying is proposed. A new bud-particle structure is obtained by modifying micron and nano Aluminium hydroxide(Al(OH)3) particles, which helps the coated surface to demonstrate excellent superhydrophobicity with the water contact angle ∼157.0° and rolling angle ∼2.0°, and it shows great repellency to water droplet impact. Due to the compatibility of Al(OH)3with the pretreatment substrate and the reinforcing effect of nanoparticles, the coating maintained the superhydrophobicity well in the sandpaper wear and the ultrasonic damage test, which reflects the outstanding robustness of the coating.Moreover,benefiting from the control of the wetting state by micronand nanoparticles doping,the coating showed an excellent underwater drag reduction effect in the rheometer experiment, with a drag reduction rate of ∼67.7 %. The one-step spraying method proposed is a simple and convenient way to create the surface with excellent superhydrophobicity and durability, which has great potential applications in improving metal surface oxidation resistance and underwater reducing drag.

Influence of the Hierarchy Structure of Aluminum Particles on Density, Combustion Efficiency, and Ignition Delay.

Aluminum nanoparticles (nAl) have received sustained interest due to their higher reactivity than micron aluminum particles (mAl). However, in practice, the densities of explosive formulations with nAl are far smaller than those with mAl, which greatly undercuts the energy release performance. To take advantages of both kinds of Al particles, in situ integration of mAl@nAl composites was proposed and evaluated. The mAl@nAl composites were prepared by in situ electrical explosion of Al wire. Their morphology, density, and specific surface area (SSA) were characterized by scanning electron microscope (SEM), densimetry, and Brunauer-Emmett-Teller (BET), respectively. SEM showed that nAl uniformly adhered to the surface of mAl. With the increase in voltage, the average diameter and density of the composites decreased, but the SSA of the composites increased. And the largest density of the composites was 1.13 g/cm3, comparable to that of the commercial graded Al product (1.25 g/cm3). Meanwhile, the highest SSA of the composites was 12.1192 m2/g. In addition, the combustion efficiency of mAl@nAl composites at 20 kV was 8.26% higher than that of physically graded counterparts. The constant-volume combustion test under zero oxygen balance revealed that the pressurization rate and peak pressure of mAl@nAl composites prepared at 20 kV were the highest of all. Furthermore, constant-volume combustion under constant heat showed that the combustion temperatures of mAl@nAl composites were 1.15-1.45 times higher than those of physically graded counterparts. Finally, the ignition delay of mAl@nAl composites was reduced with the increase in explosion voltage.

Combustion and heat release characteristics of micron aluminum with extremely large specific surface area obtained by L-malic acid surface corrosion

Aluminum (Al) particles are widely used in propellants, thermite and pyrotechnics. However, commonly used micro Al has drawbacks such as agglomeration, high ignition temperature and slow burning rate, making its energy potential not fully exploited in applications. Therefore, exploring pathways to enhance the combustion of Al particles has become the focus at present. Herein, L-malic acid (LMA) was used to corrode the surface of Al particles to obtain a sample (named LMAl) with an average specific surface area of 11.456 m2/g (corresponding to Al particles with a diameter of 194 nm). The particle size distribution of LMAl did not change significantly compared to pristine Al. The XPS results showed that a small amount of LMA and corrosion products remained on the surface of the LMAl particles. Thermal analysis tests showed that the thermal oxidation rate and efficiency of LMAl was dramatically higher than that of pristine Al. Compared with the pristine Al, the combustion characterization parameters of LMAl such as combustion intensity, ignition delay time, maximum combustion temperature, mass burning rate and combustion efficiency were all improved. This trend was maintained after blending the ammonium perchlorate (AP). The condensed combustion products (CCPs) of Al revealed a large number of agglomerates and unburned Al particles. While many broken particles and tentacle-like structures were found in the CCPs of LMAl. Overall, compared to Al, the combustion of LMAl is significantly enhanced. The thermal reaction and combustion behaviors of the two are quite different. This study provides new insights into improving the ignition and combustion of Al.

Experimental investigation on synergistic slow oxidation and rapid combustion of micron-sized iron and aluminum powders for energy storage application

The investigation into the individual application of iron and aluminum as carbon-free fuel sources has been extensively explored and holds significant promise. However, there remains a gap in understanding synergistic effects achievable through the blending of these two fuels, as well as a need for comparative analyses between the slow oxidation and rapid combustion processes of these fuels to complement each other. This research proposes blending micron aluminum and iron powders to analyze their slow oxidation and rapid combustion features under diverse atmospheric conditions and heating rates, using thermogravimetric methods, kinetic calculations, and in-flow experiments. The research blending micron iron and aluminum powders to analyze their slow oxidation and rapid combustion features under diverse atmospheric conditions and heating rates, using thermogravimetric methods, kinetic calculations, and in-flow experiments. The findings reveal that the combination of aluminum and iron powders promotes oxidation, resulting in increased weight gain and heat flux rate compared to individual metals. Moreover, the triggering temperature rises from 545 to 652 °C with an increase in aluminum powder content. As heating rates increase, characteristic parameters T1, T2, and Hpeak2, rise for both fuels. However, aluminum powder tends to decrease Ti, while iron powder slightly increases it due to differences in oxide layers. The slow oxidation of aluminum and iron powders conforms to different models, yielding distinct oxidation patterns. The apparent activation energy of aluminum decreases from 258.4 to 238.7 kJ·mol−1 with rising heating rates, while that of iron exhibits a lower increase and remains lower than aluminum providing insights into combustion initiation conditions. Combustion initiation is contingent upon the concentration of metal powder and oxygen, with both aluminum and iron powders combustion being enhanced and subsequently attenuated with increasing excess air ratio. However, due to differing reactivity and surface passivation layers, the excess air ratio required for aluminum powder combustion (1.2–2.4) exceeds that of iron powder (1.3–1.7). The research elucidates the mechanisms underlying the slow oxidation of iron and aluminum fuels, delineates suitable combustion conditions, and furnishes new empirical and theoretical underpinnings for the oxidation characteristics of mixed iron-aluminum fuels, thereby advancing metal-fueled energy storage technologies.

Study on laser ignition and combustion characteristics of micron-sized aluminum and Al-Mg alloys particles

In response to the problems of easy sintering and long ignition delay time of micron aluminum in the combustion of aluminum-containing propellants, choose the way to add magnesium to metal aluminum to construct an alloy system, through boiling, micro-explosions are generated during the ignition and combustion process to weaken the sintering behavior and shorten the ignition delay time of aluminum. Selecting aluminum and Al-Mg alloy powder fuel with a particle diameter of about 10 μm as the research object, a set of individual-particle fuel laser ignition and microscopic high-speed imaging experimental devices was built that can observe the whole process of ignition and combustion of micron-sized fuel. Thermal analysis was used to detect and characterize the thermal decomposition process of micron-sized aluminum and Al-Mg alloy powders; combined with the results of scanning electron microscopy, the difference in ignition performance of micron-sized individual particle aluminum and Al-Mg alloys was studied. Experiments have found that, compared with aluminum, the initial oxidation temperature of Al-Mg alloys is lower and the combustion is more complete. However, the effect of adding magnesium to aluminum is only reflected before 900 °C. The ignition and combustion images and flame propagation laws of micron-sized single-particle aluminum and Al-Mg alloys were obtained. It was found that adding magnesium shortened the ignition delay time, and the combustion produced less residual.

The flexoelectric properties of various polymers and energetic composites

Electroactivity of polymers used in energetic materials may result in charge separation that could result in safety concerns (unintentional ignition) or be exploited for multifunctional applications. We measured the flexoelectric properties of several polymers and energetic composites including poly(vinylidene fluoride-co-trifluoroethylene) [P(VDF-TrFE)], nanosized aluminum (nAl)/P(VDF-TrFE), poly(vinylidene fluoride-co-hexafluoropropylene) [P(VDF-HFP)], micron aluminum (μAl)/P(VDF-HFP), hydroxyl-terminated polybutadiene (HTPB), ammonium perchlorate (AP)/HTPB, μAl/AP/HTPB, polytetrafluoroethylene (PTFE), and polydimethylsiloxane (PDMS). The presence of flexoelectricity in PTFE (Teflon®) and the relatively high flexoelectric coefficient of P(VDF-HFP) (Viton®) measured in this work may help explain accidents involving the production and use of Magnesium-Teflon-Viton (MTV) that in many instances have been attributed to electro-static discharge. The addition of aluminum nanopowders to the P(VDF-TrFE) increased the flexoelectric coefficient by ∼30%. However, the addition of aluminum micrometer particles (10 wt. %) to P(VDF-HFP) decreased the effective flexoelectric coefficient, while an increase was observed when the aluminum loading was increased from 10 to 20 wt. %. The effective flexoelectric coefficient of HTPB and two propellant compositions (AP/HTPB and μAl/AP/HTPB) were measured to be in the same range as each other. The effect of particle addition (nAl, μAl, and AP) on flexoelectricity was different depending on the binder, further illustrating the complexity of flexoelectric properties in composite energetics. This may be somewhat explained by competing effects where particle additions (nAl, μAl, and AP) create additional strain gradients that contribute to flexoelectricity, but the particle additions also replace the mass of flexoelectric polymer binders (P(VDF-TrFE, P(VDF-HFP), and HTPB) with particles (nAl, μAl, and AP) that are less flexoelectric.

A study on melting characteristics of micron aluminum particles by lattice Boltzmann method

In this article, a two-dimensional lattice Boltzmann model, utilizing enthalpy as a basis, has been constructed to explore the melting behavior of aluminum particles in the micron size range. The study investigates the impacts of several key factors such as particle size, Rayleigh number, Stefan number, and porosity on temperature distribution, liquid fraction, solid-liquid interface, and melting end time. The findings demonstrate that an increase in particle size stimulates the melting process, with a weakened effect observed as particle size continues to increase. Rayleigh number has a significant effect on natural convection and heat transfer, promoting the development of these processes. Additionally, Stefan number presents a noticeable impact on the melting process, with a more apparent effect in the range of low Stefan numbers. Finally, the increase of porosity proves to be a compelling factor in the promotion of the melting process.

Porous MgO-based ceramics synthesized by the volume expansion effect: Designing and performance

High-quality porous ceramics are extremely attractive in terms of energy conservation and consumption reduction, and thus are one of the research hotspots pursued in recent years. For this purpose, porous MgO-based ceramics with outstanding thermal shock resistance and thermal insulation performance were designed and prepared by using the direct firing method and introducing alumina with different paticle sizes as additives. The results reveal that the in-situ formed MgAl2O4 phase by alumina additives simultaneously improves the apparent porosity, thermal insulation, and thermal shock resistance of the prepared MgO-based ceramics. Specifically, the increase in the apparent porosity can be attributed to the volume expansion effect of MgAl2O4 phase, so the industrial alumina with larger particle size is more effective (20 wt% addition: the apparent porosity from 43.5 % to 55.4 %, the thermal conductivity from 0.977 to 0.389 W m−1 K−1 at 800 °C); moreover, the enhancement in thermal shock resistance can be ascribed to the residual stress effect caused by the MgAl2O4 particles, so the micron alumina with smaller particle size is more efficient (10 wt% addition: the residual strength ratio from 93.48 % to 65.13 %–113.92 % and 94.47 % after one and five air-quenching). Therefore, this work demonstrates a novel synthetic strategy for porous ceramics with great potential in the field of high-temperature thermal insulation.

The effect of porosity on flexoelectricity in 3D printed aluminum/polyvinylidene fluoride composites

We investigated the relationship between porosity and flexoelectricity for aluminum (Al)/polyvinylidene fluoride (PVDF) composites. Neat PVDF, composites of micron aluminum (μAl)/PVDF, and composites of nano aluminum (nAl)/PVDF were 3D printed, and the flexoelectric response was measured using a cantilever beam test setup. Voids (up to 72.4 mm3) were incorporated into the samples by decreasing the infill percent of the 3D printed material. We found that increasing the porosity via millimeter scale voids incorporated into the infill pattern decreased the average effective flexoelectric coefficient relative to the near full-density (100% infill) control samples. This contrasts with other studies that have shown increasing micron scale porosity increases the flexoelectric coefficient. In addition, we measured higher flexoelectric responses for nAl/PVDF than μAl/PVDF as well as for samples printed by the Hyrel 3D SR printer as opposed to the Ender 3 V2 printer. These results indicate that charge generation due to flexoelectricity can be altered by changing parameters such as porosity, particle size of inclusions, or manufacturing method. Smaller voids and fine particles can induce larger strain gradients than larger inhomogeneities, leading to increased flexoelectric coefficients. A competing effect is that more porosity leads to less materials, which can decrease the flexoelectric coefficient.

Experimental study on catalyst-free high-temperature and high-pressure aluminum-water reaction characteristics using metal as energy carrier

Aluminum-water reaction have the potential for clean hydrogen production and power generation. In this work, the effects of reactions such as temperature, pressure, water-aluminum ratio, and water state of the high-temperature and high-pressure aluminum-water reaction are experimentally investigated. The findings demonstrate that the micron aluminum powder can produce 100% hydrogen in a catalyst-free neutral environment by enhancing the temperature and pressure. The aluminum-water interaction is favored by excess water and the gas-liquid two-phase state. The effects of Na+ and K+ ions within water in high-temperature and high-pressure reactions under neutral environments have a negligible effect, and the in-situ reaction with clean water has a high hydrogen yield. The high-temperature and high-pressure aluminum-water reactions consist of four stages. Hydrogen and heat are generated only when water molecules and activated aluminum are constant touch. He results provide the foundation for aluminum-water-based hydrogen cogeneration.

Low-temperature ignition and mechanism of μAl coated with bismuth citrate

Because of the existence of an oxide layer on the surface of micron aluminum (μAl) powder, it is difficult to ignite. In order to improve μAl ignition, Al particles were coated with bismuth citrate (Bi(cit)) by a solvent evaporation method. The morphology of Al-Bi(cit) was observed by scanning electron microscope (SEM) showed that Bi(cit) was evenly distributed on the surface of Al particles. The ignition temperature was reduced and ignition delay time at different temperatures of the Al-Bi(cit) were tested in a transparent tube furnace. With the increase of Bi(cit) content, the ignition temperature and ignition delay time shortened, and the combustion flame captured by the high-speed camera was more bright. The test results showed that Al-20 wt% Bi(cit) has a low ignition temperature of 479 °C, and the ignition delay time at 450 °C is only 7 s. The thermal behavior of Al-Bi(cit) was studied by thermogravimetric analysis (TG-DSC). Combined with the characterization results of the products at different heating temperatures, the combustion mechanism was proposed and proved.

Chemically bonded phosphate ceramic coatings with self-healing capability for corrosion resistance

Chemically bonded phosphate ceramic coatings (FCBPC) modified with organic-inorganic hybrid nano alumina (FAS-Al2O3) were prepared. The effects of FAS-Al2O3 on the morphology, corrosion resistance and self-healing properties of FCBPC are investigated. The results show that FAS-Al2O3 can improve the penetration resistance, bond strength and corrosion resistance of the coating. When the content of FAS-Al2O3 is 1.5 wt%, the impedance value at low frequency (0.01 Hz) of FCBPC3 can reach 1.52 × 106 Ω·cm2. This is mainly attributed to the introduction of organic perfluorinated long chains with low surface energy by fluorinated alkyl silane, which allows nanoparticles to be uniformly dispersed on micron alumina ceramic aggregates to build special micro-nano structures. FAS-Al2O3 can combine with AlPO4 and act as a binder to fill the pores between ceramic aggregates, increasing the cohesion of the coating and the bond strength between the coating and the substrate to the point of blocking or extending the diffusion path of corrosive media inside the coating, which in turn improves the corrosion resistance of coatings. In particular, the coatings exhibit excellent self-healing properties in terms of corrosion resistance after heat treatment. Heat treatment will cause the organic perfluorinated molecules in FAS-Al2O3 to rotate and migrate, and more fluorinated alkyl chains will be exposed, thereby minimizing the surface energy of the coating. In addition, special micro-nano structures are reconfigured due to thermally driven self-migration of organic perfluorinated chains. As a result, the hydrophobicity and impermeability of the coating are restored after heat exposure, reducing the intrusion of corrosive media, and thus the corrosion resistance of the coating has self-healing capability. This work could open up a thought-provoking idea for improving the long-term corrosion protection of phosphate ceramic coatings in high-temperature marine environments.

Numerical simulation of the interaction of heterogeneous detonation with an inhomogeneous porous insert

Numerical simulation of interaction of heterogeneous detonation wave (DW) with a porous insert occupied whole channel and part of channel was carried out. Main regimes and critical conditions of detonation attenuation and failure in porous zones were obtained for micron and submicron aluminum particles. The main difference of regimes of detonation propagation for micron and submicron aluminum particles was found. It was found that for micron and submicron particles exists a critical height of porous free region, which leads to detonation failure. The critical width of the open space between porous bodies at which detonation failure occeurs was found. For porous zones with two open spaces critical width of the open space is the same that is obtained for one open space. Critical conditions of porous inserts with open space area should be greater than for porous zone that occupies whole width of the channel.

Investigation of Heterogeneous Detonation Wave Interaction with Porous Medium

ABSTRACT Mathematical model of aluminum heterogeneous detonation interaction with inert porous media was developed. Main regimes of interaction of heterogeneous detonation wave of stoichiometric mixture of aluminum particles in oxygen with porous inserts were studied. One- and two-dimensional calculations for micron and submicron particles and comparison of these calculations were made. Main regimes of detonation interaction with porous zone and critical conditions of detonation attenuation in porous zones were obtained. Calculations show that for micron particles reducing the diameter of burning particles lead to increasing the volume concentration of inert phase in the porous body that needs for detonation attenuation. Main difference of the propagation regimes for micron and submicron aluminum particles was found.

Experimental investigation of the catalyst-free reaction characteristics of micron aluminum powder with water at low and medium temperatures

Aluminum metal has a high energy density and can react with water to produce hydrogen instantly, which is environmental-friendly and safe. Aluminum has great potential to provide a good carrier for energy and hydrogen storage. The utilization of aluminum is constrained by the oxide layer on its surface. In order to promote the aluminum-water reaction to continue efficiently, the reaction needs to be activated. The modification of aluminum is often complicated and dangerous, and it is difficult to apply the hydrogen produced by the reaction and the heat released. The increase of temperature and pressure of the reaction has also been proved as a useful activation method. Continuous reactions are difficult to achieve at high temperature and pressure, and it becomes difficult to obtain reaction initiation and development processes. However, the reaction process has an essential impact on the utilization of the aluminum-water reaction. In this paper, the aluminum-water reaction process at medium temperature was investigated using micron aluminum powder. The effects of initial temperature, particle size of aluminum powder and water type on the reaction were further analyzed. In addition, the kinetic analysis of the aluminum-water reaction was carried out to obtain kinetic models. Experimental results indicate that the product of the aluminum-water reaction is Al(OH)3 at 90–150 °C. The reaction initial temperature shows a multipolar effect on the reaction between aluminum and water. The hydrogen yield from the reaction between ∼25 μm aluminum powder and tap water at 150 °C is 31.9 %. The pre-exponential factor and apparent activation energy increase with the reaction proceeding. The present research is conducive to further safe and efficient utilization of micron aluminum powder for energy conversion, and benefits the achievement of carbon peaking and carbon neutrality.

Aluminum-Based Fuels as Energy Carriers for Controllable Power and Hydrogen Generation—A Review

Metallic aluminum is widely used in propellants, energy-containing materials, and batteries due to its high energy density. In addition to burning in the air, aluminum can react with water to generate hydrogen. Aluminum is carbon-free and the solid-phase products can be recycled easily after the reaction. Micron aluminum powder is stable in the air and enables global trade. Aluminum metal is considered to be a viable recyclable carrier for clean energy. Based on the reaction characteristics of aluminum fuel in air and water, this work summarizes the energy conversion system of aluminum fuel, the combustion characteristics of aluminum, and the recycling of aluminum. The conversion path and application direction of electric energy and chemistry in the aluminum energy conversion system are described. The reaction properties of aluminum in the air are described, as well as the mode of activation and the effects of the aluminum-water reaction. In situ hydrogen production is achievable through the aluminum-water reaction. The development of low-carbon and energy-saving electrolytic aluminum technology is introduced. The work also analyzes the current difficulties and development directions for the large-scale application of aluminum fuel energy storage technology. The development of energy storage technology based on aluminum is conducive to transforming the energy structure.

Study on non‐uniformity and dynamic fracture characteristics of GIL tri‐post insulators considering Al2O3 sedimentation

AbstractTri‐post insulators in gas‐insulated transmission line (GIL) are usually fabricated with high mass fraction of micron aluminum oxide (Al2O3), which will unavoidably settle under the action of gravity during the preparation process and seriously affect the uniformity. A model of filler sedimentation in epoxy resin composite materials was proposed based on the particle size analysis and Stokes' Law. Some scaled tri‐post insulators were prepared and tested by slicing. It is determined that the position of density concentration is the lower side of the two lower posts and the upper interface between the insulator and the conductor. The density ranges from 2.144 to 2.346 g/cm3. The dynamic fracture simulation model of insulator was established and it is found that the insulator fracture occurs at the interface of upper post/insert under radial load, which is verified by experiments. By comparing the influence of sprue position on the density distribution, it is found that the uniformity of insulators is increased by 13.7% by forward pouring compared with reverse pouring. This research develops an accurate method for simulating the filler sedimentation and the fracture process in epoxy‐based insulators, which is helpful for the improvement of mechanical reliability of GIL.

Highly Filled Composite Materials Based on UHMWPE and a Mixture of Micron and Nanoscale Aluminum Particles

Highly Filled Composite Materials Based on UHMWPE and a Mixture of Micron and Nanoscale Aluminum Particles

Agglomeration in Composite Propellants Containing Different Nano‐Aluminum Powders

AbstractIn order to improve nano‐aluminized solid propellant properties and performance, different materials are being investigated for coating nano‐aluminum particles. Two of the powders which are considered are V‐ALEX, a fluoropolymer (Viton) coated nano‐aluminum, and L‐ALEX, a stearic acid coated nano‐aluminum. It is believed that a thin layer of coating should protect the aluminum core from premature oxidation, as well as provide an exothermic source which may accelerate particle ignition, resulting in reduction of agglomeration.This paper investigates the effect on the agglomeration phenomenon of replacing 33 % of the micron aluminum powder with ALEX, V‐ALEX and L‐ALEX powders, in solid propellant samples containing 20 % HTPB, 65 % AP and 15 % aluminum. Propellant strands were burned inside a windowed pressure chamber, allowing measurements of the agglomerates size and number using a high‐speed camera.The experimental data showed that propellants in which 33 % of the micron aluminum was replaced with nano‐powders exhibited reduced agglomeration, in terms of number of agglomerates and their total volume. The reason is the lower ignition time and temperature of the nano‐powders that ignite before aggregating to agglomerates. The propellants containing ALEX nano‐powder exhibited a reduction of up to 36 % in agglomerates volume compared to the propellants containing only micron powder, while the propellants containing coated nano‐powders, L‐ALEX and V‐ALEX, showed a higher reduction of up to 60 % in agglomerates volume. V‐ALEX showed slightly better performance than L‐ALEX. It can be concluded that by replacing some of the micron‐aluminum with coated nano‐aluminum in solid propellants, it is possible to significantly reduce the propulsive losses due to agglomeration.