Effect Of Aluminum Particle Size Research Articles

The Effect of Aluminum Particle Size on the Formation of Reactive Jet

In order to study the morphology characteristics of the PTFE/Al reactive shaped charge jet and the chemical reaction during the jet formation, PTFE/Al reactive liners with aluminum particle sizes of 5 μm and 100 μm were prepared. The parameters of the Johnson–Cook constitutive model of PTFE/Al reactive materials (RMs) were obtained through quasi-static compression experiments and SHPB (Split Hopkinson Pressure Bar) experiments. X-ray imaging technology was used to photograph the shape of reactive shaped charges jet at two different time points. The AUTODYN secondary development technology was used to simulate the jet formation, and the simulation results are compared with the experimental results. The results show that the simulation results are close to the experimental results, and the error is in the range of 4–8%. Through analysis, it is observed that the RMs reacted during the PTFE/Al reactive shaped charge jet formation, and due to the convergence of the inner layer of the liner during the jet formation, the chemical reaction of the jet is from inside to outside. Secondly, the particle size of aluminum powder has an influence on the chemical reaction and morphology of the jet. During the jet formation, there were fewer RMs reacted when the PTFE/Al reactive liners were prepared with 100 μm aluminum powder. Compared with 5 μm aluminum powder, when the aluminum powder is 100 μm, the morphology of the jet is more condensed, which is conducive to generating greater penetration depth.

A comparative study on aluminum dust explosion suppression by powder inhibitors

ABSTRACT An aluminum dust explosion is a major safety hazard that cannot be ignored. It is of great practical significance to investigate explosion flame propagation characteristics and powder inhibition mechanisms of aluminum dust. Based on a self-designed dust explosion experimental system, explosion flame propagation characteristics such as flame shape, temperature and velocity were captured. The effect of aluminum particle size on the flame propagation was explored, and inhibition performances and mechanisms of NaHCO3, CaCO3 and Na2HPO4 on aluminum dust explosion were experimentally and theoretically revealed. The proportion of white bright areas decreased from 17.9% to 7.9%, 8.0% and 8.8% respectively, and the temperature and velocity decreased obviously with powder inhibitors. Especially, NaHCO3 can reduce the maximum flame temperature and maximum flame velocity to 1411°C and 14.27 m/s respectively, and its inhibition performance was optimal. CaCO3 had better performance than Na2HPO4 in suppressing the flame propagation velocity and in delaying the ignition time, and Na2HPO4 was more advantageous in suppressing the explosion flame temperature. It is explained by the mechanism that substances containing Na and P can play an important role in the suppression of gas-phase reactions. The Na cycle (NaO ↔ Na) is effective in scavenging free radicals.

Effects of Al Particle Size on the Impact Energy Release of Al-Rich PTFE/Al Composites under Different Strain Rates.

Polytetrafluoroethylene (PTFE)/Al reactive material with different aluminum particle sizes were prepared by molding and sintering, and the effect of aluminum particle size on the impact behavior of PTFE/Al reactive material with a mass ratio of 50:50 was investigated. The results show that aluminum particle size has significant effects on the shock-reduced reaction diffusion, reaction speed, and degree of reaction of the PTFE/Al reactive material. At a moderate strain rate, the reaction delay of PTFE/Al increased, and the reaction duration and degree decreased, with the increase of aluminum particle size. Under the strong impact of explosive loading, aluminum particle size has little effect on the reaction delay, which maintains at about 1.5 μs–2.5 μs, but the reaction durability and degree of reaction of PTFE/Al decrease with increasing aluminum particle size. There is also a strain rate threshold for the shock-induced reaction of PTFE/Al reactive material, which is closely related to aluminum particle size. The shock-induced reaction occurs when the strain rate threshold is exceeded.

Cover Picture: Effect of Aluminum Particle Size on the Performance of Aluminized Explosives (Prop., Explos., Pyrotech. 5/2020)

Cover Picture: Effect of Aluminum Particle Size on the Performance of Aluminized Explosives (Prop., Explos., Pyrotech. 5/2020)

Effect of Aluminum Particle Size on the Performance of Aluminized Explosives

AbstractTo characterize the effect of the particle size on the combustion time of aluminum (Al) in aluminized explosives, a series of cylinder tests was performed with RDX and Al compositions (median size of 2, 10, and 47 μm). Similar compositions were also prepared with RDX and lithium fluoride (LiF). The expanding velocities of the cylinders were measured using photonic Doppler velocimetry (PDV). The results show that the Al reaction delay is less than 3 μs, and the majority of the Al reaction is less than 25 μs. Among the RDX/Al formulas with 0 %, 15 %, and 30 % weight percent of Al, the formula with 15 % Al has the best metal acceleration ability. The effects of the particle size on the cylinder test are surprisingly negligible over the range of 2–47 μm, which implies that the Al particle combustion in the detonation product does not obey the classical d1 law. Finally, a novel Al combustion model in the detonation product was proposed based on the experimental result and theoretical analysis. The model suggests that the Al particle breakup plays an important role in the post‐detonation combustion of Al.

A dynamic analysis of the aluminum titanate (Al2TiO5) reaction-sintering from alumina and titania, properties and effect of alumina particle size

Aluminum titanate Al2TiO5 materials were successfully processed from different fine commercial powders and characterized. Particularly, two calcined aluminas were compared through a multitechnique approach including differential thermal analysis and dilatometry together with structural, microestructural, and mechanical characterization. This allowed the description of all the thermochemical processes during thermal treatment. Developed phases were established. Relatively dense ceramics were obtained, and complex microstructures were described with interlocked grains and an interconnected microcrack matrix that do not jeopardize the material integrity. Multistep sintering and reaction sintering processes were observed in both samples. The first stage consists of the sintering of the starting powders (alumina and titania). A second sintering stage of the starting powders was observed for both samples as well. Once advanced, the second one is overlapped with Al2TiO5 formation that starts at 1380 °C and finishes at 1440 °C. They affect crack development and, in consequence, the thermal behavior. The lower alumina particle size enhances the sintering and reaction advance processes. In the technological temperature range (room temperature—1000 °C), low or even negative thermal expansion behaviors were observed in the developed materials. This, together with the mechanical behavior, encourages structural applications with high thermomechanical solicitations of Al2TiO5 based materials.

Effect of alumina particle size on characteristics, corrosion, and tribological behavior of Co/Al2O3 composite coatings

The electrodeposition technique was used to produce Co, Co/micro-Al2O3, and Co/nano-Al2O3 coatings. The effect of particle size on current efficiency, thickness, composition, morphology, and structure of the coatings was investigated. The potentiodynamic polarization technique and electrochemical impedance spectroscopy was used to study the corrosion behavior of the coatings. Tribological behavior of the micro/nano-composite coatings was also examined, and the results were compared to the pure Co and the steel substrate. The results revealed that the incorporation of alumina nano-particles decreased the current efficiency of Co electrodeposition. Although the weight percent of the co-deposited nano-particles was much less than the micro-particles under the same electrodeposition conditions, their effect on morphology was more pronounced. The Co/micro-Al2O3 coating had a higher hardness and corrosion resistance than the other samples. The incorporation of nano-particles decreased the hardness and polarization resistance of the pure Co by about 15 and 59%, respectively. Unlike the corrosion results, both the composite coatings had better wear resistance than the pure Co film. However, the volume loss of the Co/micro-Al2O3 coating was 1.6 times lower than the Co/nano-Al2O3 electrodeposit.

Effect of Alumina Particle Size on the Bond Strength between Autopolymerized Acrylic Resin and Commercially Pure Titanium.

To address the following null hypothesis: when the Rocatec bonding system is used, the various sizes of aluminum oxide particles used to roughen the surface area of the commercially pure (CP) titanium prior to bonding to autopolymerized resin have no effect on the average shear bond strength. One hundred specimens were randomly allocated to five equally sized groups: Ti-no air abrasion (group A), Ti-air-abraded with 50 μm (group B), Ti-110 μm (group C), Ti-250 μm (group D), and Co-Cr-50 μm (group E) grain-size aluminum oxide. Rocatec Plus tribochemical coating was applied to all of the specimens, followed by a RelyX primer and Sinfonyopaquer. Autopolymerized denture base resin was then bonded to the treated titanium surfaces. All specimens underwent thermocycling (10,000 cycles), shear bond testing, and mode of failure examination under stereoscopic microscopy. The average bond strength of group D (250 μm) was significantly different compared to all other groups, except group C (p = 0.057, trending significance). The average bond strength of group D was substantially higher than that in the other groups (p < 0.01). The weakest bond was observed when the specimens did not receive any air abrasion (group A). Maximum load (N) showed the same significant results as the shear bond strength at maximum load (MPa). The average extension at maximum load (mm) and the time at maximum load(s) for group A were significantly different than that of all other groups. Group A had lower average values than any other group (p = 0.003). More cohesive and mixed, rather than adhesive, modes of failure were observed as the size of the aluminum oxide particles increased. When the Rocatec system is used, using a combination of chemical and micromechanical adhesion is essential for the success of the bond between the autopolymerized acrylic resin and CP Ti. The micromechanical interlock can be improved significantly when the Ti surface is air abraded with larger particles (250 μm) than the currently used alumina particle size.

Preparation of dense mullite polycrystals by reaction sintering of kaolin materials and alumina and their microstructure

Dense and single-phase mullite polycrystals were prepared by reaction sintering of relatively pure kaolins with several kinds of alumina. Removal of coarse kaolin particles >1 µm by sedimentation substantially improved thermal reactivity and sinterability of kaolin and its mixtures with alumina. As for mixtures of refined kaolin and submicron corundum powder having a mullite composition, relative densities of above 98% were accomplished by heat-treatment at 1650°C for 1 h. Effect of alumina particle size on thermal reactivity between alumina and kaolin was investigated, and the difference in thermal reaction sequence between alumina and kaolin was clarified. A combination of sub-micron corundum and elutriated kaolin yielded a monodispersed and fine-grained mullite polycrystals.

Investigation of particle size and reinforcement content on mechanical properties and fracture behavior of A356-Al2O3 composite fabricated by vortex method

The aim of the present study is to investigate the effect of alumina particle size and its amount on relative density, mechanical properties, and fracture behavior of [Formula: see text] composite. To manufacture micro and nano-composites, alumina particles with various sizes of 50 µm, 10 µm, and 20 nm were separately milled with aluminum powders, and subsequently different volume fractions of milled powders were injected by argon gas into molten alloy and incorporated into A356 matrix by a mechanical stirrer (vortex method). Composites were fabricated at various casting temperatures, viz. 750, 800, and 900℃. Microstructural characterizations revealed that the dendrite size of the Aluminum matrix nano composite (AMNCs) is smaller than that of the non-reinforced alloy. The Scanning electron microscope (SEM) micrographs revealed that the [Formula: see text] particles were surrounded by silicon eutectic and inclined to move toward inter-dendritic regions. Nano-particles were dispersed uniformly in the matrix when the volume fraction of nano-particles in the composite was less than 3.5 vol.%. The porosity content of the composites increased with increasing volume fraction and decreasing particle size. Also, hardness and tensile strength of the composites improved with decreasing particle size and increasing reinforcement content. The significant improvements in hardness and tensile strength were respectively attained in the nano-composites, reinforced with 1.5 and 2.5 vol.% [Formula: see text] nano-particles. Alumina particle cracking was observed in the fracture surface of the micro-composites. Agglomerated nano-particles were observed on dendrites in the fracture surface of nano-composites.

Influence of Aluminum Particle Size on Thermal Decomposition of RDX

The effect of aluminum particle size (10.7 µm, 2.6 µm, and 40 nm) on the thermal decomposition of 1,3,5-trimethylene trinitramine (RDX) was investigated using differential scanning calorimetry (DSC), thermogravimetry–derivative thermogravimetry (TG-DTG), and DSC-TG–mass spectrometry (MS)–Fourier transform infrared (FTIR) spectroscopy, respectively. The results showed that the first exothermic peak (512 K) of RDX diminishes gradually with an increase in the nanosize aluminum content and is overcome by the second exothermic peak when the content of nano-Al reaches 30 wt%. The reaction mechanisms demonstrated by the nonisothermal kinetics of RDX in the absence and presence of 30 wt% Al were conformed to the Avrami-Erofeev equations for all of the RDX compositions. The nucleus growth factor for the RDX/40 nm Al mixture was found to be n = 2/3 compared to n = 3/4 for RDX with and without the microsized Al. The MS and FTIR analyses indicated that the thermal decomposition of RDX in the presence of Al nanopowders favors C-N bond cleavage over N-N bond cleavage as the rate determining step.

Effect of Pore Characteristics in Slip Cast Alumina on Glass Infiltration and Mechanical Properties of the Composites

Development of alumina/glass composites with minimal residual porosity and superior mechanical properties requires systematic studies on glass infiltration into porous alumina. This work has examined the effect of alumina particle size and the resulting pore size distribution on glass infiltration. Samples were prepared by slip‐casting a coarser alumina powder and blends of the coarse (d50 ~ 3.4 μm) and a finer (d50 ~ 0.7 μm) alumina powder. After presintering (1200°C) and following a single cycle of infiltration (1100°C), the sample with 50:50 (wt%) coarse and fine alumina showed highest flexural strength. Improvement in flexural strength could be imputed to the better glass infiltration.

Effect of alumina particle size and thermal condition of casting on microstructure and mechanical properties of stir cast Al–Al2O3 composites

Metal matrix composites are considered as a distinct category of the advanced materials, which have low weight, high strength, high modulus of elasticity, low thermal expansion coefficient and high wear resistance. Among them, Al–Al2O3 composites have achieved significant attention due to their desired properties. In the present research, Al–Al2O3 composites with 5 vol.-% alumina were produced by stir casting at a temperature of 800°C. Two different particle sizes of alumina were used as 53–63 and 90–105 μm. The microstructure of the samples was evaluated by SEM. In addition, the mechanical properties of the samples were measured, and hence, the optimum temperature and particle size of alumina to be added to the Al matrix were determined. The results demonstrated the positive effect of alumina on improving the properties of Al–Al2O3 composites.

Investigation of particle size and amount of alumina on microstructure and mechanical properties of Al matrix composite made by powder metallurgy

Al matrix composite is well known, in which Al2O3 is the most widely used reinforcement. The aim of this study is to investigate the effect of alumina particle size and its amount on the relative density, hardness, microstructure, wear resistance, yield and compressive strength and elongation in Al–Al2O3 composites. To this end, the amount of 0–20wt.% alumina with average particle sizes 48, 12 and 3μm was used along with pure aluminum of average particle size of 30μm. Powder metallurgy is a method used in the fabrication of this composite in which the powders were mixed using a planetary ball mill. Consolidation was conducted by axial pressing at 440MPa. Sintering procedure was done at 550°C for 45min. The results indicated that as the alumina particle size is reduced, density raises at first, then, declines. Moreover, as the alumina particle size decreases, hardness, yield strength, compressive strength and elongation increase and factors such as wear resistance, microstructure grain size and distribution homogeneity in matrix decreases. For instance, as the alumina particle size gets smaller from 48 to 3μm at 10wt.% alumina, hardness rises from 50 to 70BHN, compressive strength improves from 168 to 307MPa and wear rate rises from 0.0289 to 0.0341mm3/m. On the other hand, as the amount of alumina increases, hardness and wear resistance increase and relative density and elongation is decreased. However, compressive and yield strength rise at first, then drop. For example, if the amount of alumina with 12μm particle size increases from 5 to 10wt.%, hardness increases from 47 to 62BHN and compressive strength rises from 190 to 273MPa. Nevertheless, erosion rate after 300m decreases from 0.0447 to 0.0311mm3/m.

The effect of particle size, sintering temperature and sintering time on the properties of Al–Al 2O 3 composites, made by powder metallurgy

Al 2O 3 is a major reinforcement in aluminum-based composites, which have been developing rapidly in recent years. The aim of this paper is to investigate the effect of alumina particle size, sintering temperature and sintering time on the properties of Al–Al 2O 3 composite. The average particle size of alumina were 3, 12 and 48 μm. Sintering temperature and time were in the range of 500–600 °C for 30–90 min. A correlation is established between the microstructure and mechanical properties. The investigated properties include density, hardness, microstructure, yield strength, compressive strength and elongation to fracture. It has been concluded that as the particle size of alumina is reduced, the density is increased followed by a fall in density. In addition, at low particle size, the hardness and yield strength and compressive strength and elongation to fracture were higher, compared to coarse particles size of alumina. The variations in properties of Al–Al 2O 3 composite are dependent on both sintering temperature and time. Prolonged sintering times had an adverse effect on the strength of the composite.

Effect of Alumina Particle Size on Ni/Al 2O 3 Catalysts for p-Nitrophenol Hydrogenation

The catalytic hydrogenation of p-nitrophenol to p-aminophenol was investigated over Ni/Al 2O 3 catalyst on alumina support with different particle size. It is found that support particle size has significant influences on physiochemical properties and catalytic activity of the resulting Ni/Al 2O 3 catalyst, but little influence on the selectivity. At a comparable amount of Ni loading, the catalytic activity of Ni/Al 2O 3 prepared with alumina support of smaller particle size is lower. The reduction behavior of the catalyst is a key factor in determining the catalytic activity of Ni/Al 2O 3 catalyst. The supported nickel catalyst 10.3Ni/Al 2O 3-3 improves the life span of the membrane by reducing fouling on the membrane surface compared to nano-sized nickel.

Fabrication of Ceramic Microscale Structures

Ceramics are attractive materials for engineering applications involving high temperatures and corrosive chemicals. Here, an inexpensive and reproducible ceramic microfabrication technology was used to fabricate high‐density alumina structures for applications in microchemical systems. The new method is based on the gelcasting procedure, but key drying and sintering steps have been adjusted to avoid warpage and cracking of the final structures. Centimeter‐scale ceramic structures with submillimeter features can be accurately replicated from an elastomeric mold. Further study of the effect of alumina particle size, Dp, on the smallest achievable and reproducible feature size showed that excellent replication of patterns can be achieved as long as the dimensions of features in the mold are greater than 30Dp for the range of Dp from 0.3 to 3.0 μm.

Acceleration Ability and Heat of Explosive Decomposition of Aluminized Explosives

This paper studies the effect of aluminum particle size on the acceleration ability and heat of explosive decomposition of aluminized compositions containing HMX, nitroguanidine, and bis (2,2,2‐trinitroethyl) nitramine. The addition of Al increases the acceleration ability of the HEs. The replacement of Al with micron‐size particles by an ultrafine powder with a particle size of 0.1 μm does not lead to an additional increase in the acceleration ability. The effect of Al on the heat of explosive decomposition of the examined compositions is investigated.

Effect of alumina particle size and distribution on infiltration rate and fracture toughness of alumina–glass composites prepared by melt infiltration

Four commercial alumina powders having different particle sizes (0.44, 2.85, 7.08 and 39.81 μm) were presintered for 2 h at 1120 °C and then lanthanum–aluminosilicate glass was infiltrated for up to 4 h at 1100 °C to prepare the densified alumina–glass composites. Alumina having a bimodal and broader particle size distribution was the most effective to the packing. The penetration rate constant increased with raising the alumina particle size having a parabolic dependence of infiltration distance on time described by the Washburn equation. However, the optimum mechanical properties were observed for the composite containing the 2.85 μm alumina. Although the higher fracture toughness of the composites may be achieved by increasing the alumina particle size probably due to the dispersion toughening, the larger alumina particles reduce the strength.

Effect of Particle Size during Tungsten Chemical Mechanical Polishing

The size of the abrasive particles plays a critical role in controlling the polishing rate and the surface roughness during chemical mechanical polishing of interconnect materials during semiconductor processing. Earlier reports on the effect of particle size on polishing in silica show contradictory conclusions. To the best of our knowledge, a systematic study of the effect of particle size on tungsten polishing has not been published. This paper describes the controlled measurements that were conducted to determine the effect of alumina particle size during polishing of tungsten. Alumina particles of similar phase and shape with size varying from 0.1 to diam were used in these experiments. The polishing experiments showed that the local roughness of the polished surfaces was insensitive to alumina particle size. The removal rate was found to increase with decreasing particle size and increased solids loading. These results suggest that the removal rate mechanism is not a scratching type process, but may be related to the contact surface area between particles and polished surface controlling the reaction rate. ©1999 The Electrochemical Society