Aluminum Flakes Research Articles

The Preparation of a Colorful Aluminum Flake Powder with Smart Anticorrosion Properties by Encapsulation of Composited Metal–Organic Framework-Derived Layers

The Preparation of a Colorful Aluminum Flake Powder with Smart Anticorrosion Properties by Encapsulation of Composited Metal–Organic Framework-Derived Layers

Effect of Aluminum Flakes on Corrosion Protection Behavior of Water-Based Hybrid Zinc-Rich Coatings for Carbon Steel Substrate in NaCl Environment

In this study, waterborne hybrid organic-inorganic zinc rich coatings (ZRC) with different aluminum flake amounts were tested at low thickness in 3 wt% NaCl aqueous solution. Open circuit potential and impedance response evolution over time were measured experimentally to evaluate their anticorrosion properties. Microstructure of the investigated coatings and composition of the corrosion products were also determined by electron microscopy, X-ray diffraction and infrared spectroscopy, while the stability of the coatings was investigated via inductively coupled plasma optical emission spectroscopy. The results showed that the absence of aluminum flakes leads to a less stable matrix, unable to retain sufficient corrosion inhibitors, resulting in a shorter protection time. For an intermediate concentration of aluminum particles, good corrosion properties were observed. Corrosion products play an important role in the protection mechanism, with simonkolleite and hydrozincite accumulating over time, forming a protective layer on the substrate for several weeks. High amounts of aluminum also lead to the formation of corrosion products, but without providing a barrier effect, while rapidly consuming zinc, leading to rapid formula failure. These results indicate that the use of a controlled amount of aluminum flakes can significantly improve the corrosion protection capability of this type of coating.

Explosion suppression flame and mechanism of energetic dust with distinct morphologies: Aluminum-containing metal as a typical

A series of explosion suppression experiments on aluminum powder with diverse morphologies were carried out in vertical pipelines. By combining the flame propagation images and flame temperatures, the physical and chemical effects of inhibitors on the flame propagation of spherical aluminum powder (S Al ) and flaky aluminum powder (F Al ) were explored. The results demonstrated that the amount of inhibitor required for F Al was greater than S Al , and the chemical effects of piperazine pyrophosphate (PPAP) were more effective in inhibiting S Al , whereas the physical effects of nano-SiO 2 were more significant in suppressing F Al . PPAP dramatically reduced the flame propagation velocity, flame temperature, and flame propagation maximum height of S Al as the inhibitor mass fraction increased. The flame temperature, ignition delay time, and flame illumination of F Al could even be considerably changed by nano-SiO 2 . The microscopic and macroscopic suppression mechanisms of PPAP and nano-SiO 2 on different morphology of aluminum powder were proposed. • PPAP displays superior performance in inhibiting spherical aluminum powder. • Flake aluminum powder explosion suppression is more difficult than spherical powder. • Nano-SiO 2 can significantly affects the explosion of flake aluminum powder. • Microscopic and macroscopic suppression mechanisms of PPAP and nano-SiO 2 are studied.

A dense structure constructed by flake and spherical aluminum: Simultaneously enhanced anti‐wear and anti‐corrosion properties of epoxy/polytetrafluoroethylene composite coatings

AbstractThe construction of a dense structure of the coatings is the basic guarantee to ensure the good performances of the coatings, and it is also one of the problems faced by the most coatings at present. The present work attempts to build a dense coating structure by introducing flake and spherical aluminum powders into the epoxy/polytetrafluoroethylene composite coatings so as to improve the anti‐wear and anti‐corrosion properties of the coatings. As a result, the coating filled with both flake and spherical aluminum exhibited denser microstructure, which was attributed to the synergistic effect of flake and spherical aluminum particles. Among them, the flake aluminum blocked the straight‐through holes in the coating, while the spherical aluminum further filled the micropores between the flake aluminum and the gaps between the flake aluminum and the matrix. In response, the micro‐hardness of the coating was increased by 58.6% and the wear rate was reduced by 80% compared to that of coating without aluminum powders. The excellent wear resistance was attributed to the synergetic effect of the enhanced micro‐hardness of the coating and the formed high load‐bearing tribofilm on the dual ball. Moreover, the coating still maintained the maximum Rc of 3.63 × 109 Ω cm2 after 360 h of immersion owing to the improved barrier properties of the coating.

Comprehensive comparison of high productivity cobalt catalysts for Fischer – Tropsch synthesis with different types of heat-conductive frames

The results of physicochemical comparative study of Fischer – Tropsch industrial cobalt zeolite-containing catalysts are presented. The catalysts are based on heat-conductive additive (aluminum flakes or exfoliated graphite) and were tested in one tube industrial scale reactor (length – 6000 mm, inner diameter – 12 mm). For comparison purposes, the testing results of catalyst without heat-conductive additive are presented. It’s shown that exfoliated graphite-based catalyst is more suitable for industrial scale application in high syngas gas hour space velocities due to higher thermal stability and higher hydrocarbon productivity.

Calculation model for drag coefficient and multi-phase flow characteristics in dust removal process: Comparison between flake aluminum powder and spherical aluminum powder

It is of great significance to study the force model of flake and spherical particles in a two-phase flow system for reducing dust hazards. In present work, the correspondence between drag coefficient Cd and Re for spherical particle is specified by a new CFD method. Moreover, 144 kinds distribution states for flake particle with equal probability are summarized into 7 kinds stress state models with different occurrence probabilities, and the corresponding relationship between the equivalent drag coefficient Cd and the equivalent Reynolds number Re is further obtained. A series of ventilation and dust removal experiments and full-scale numerical simulation in a large space are carried out, and the maximum error of peak dust concentration between the simulation results and the experimental results for flake powder is 17.4%. In addition, the size effect of flake powder is more obvious than that of spherical powder, and the fluidity of flake powder with equal particle size is obviously better than that of spherical powder, so flake powder can be removed from the production workshop faster. However, in the process of ventilation and dust removal, the diffusion risk of spherical dust larger than 100 μm do not change much during the ventilation process.

Preparation and characteristics of polymer matrix composite coatings with low infrared emissivity and high‐temperature resistance

AbstractWith the rapid advances in detection technologies for modern warfare, it is of great significance to develop advanced infrared stealth technology. Owing to the complex operational environment of weapons and equipment during the practical application, a high thermal resistance is significant for infrared stealth materials. Therefore, in this study, a high‐temperature coating with low infrared emissivity was developed via spraying of poly(phthalazinone ether nitrile ketone) (PPENK) resin as binder and flake aluminum powder as filler. The variation in infrared emissivity of the composite coating with respect to filler content was studied. Apart from the thermal resistance of the composite coating, the effects of temperature on the surface morphology, chemical composition, mechanical properties, and infrared emissivity of the composite coatings were systematically examined. The lowest infrared emissivity (0.136) was achieved with 40% filler. Even after being heated at 450°C for 1 h, the composite coating exhibited excellent adhesion and impact resistance with negligible increase in emissivity, exemplifying its robust performance. The PPENK/Al composite coating can be engineered on a large scale, thanks to the simple preparation route and, has great potential as a new material for high‐temperature infrared stealth application.

Ignition sensitivity and explosion behaviors of micron-sized aluminum powder: Comparison between flake aluminum powder and spherical aluminum powder

The addition of aluminum powder can increase the energy of the combustion system. The spherical aluminum powder can be flaked by the ball milling technology, which can remove the oxide layer on the particle surface and improve the reaction activity. However, the ignition sensitivity and thermal behavior of flake aluminum powder should arouse extensive attention. In this paper, experimental measurements and statistical analysis are carried out for the ignition characteristics and explosion mechanism of micron-sized flake and spherical aluminum powder. Because the oxide layer is an important component in the oxidation process of aluminum powder, a theoretical model to calculate its equivalent thickness and fracture conditions is proposed. Moreover, the surface effect has a significant impact on intensifying the explosion hazard. For micron-sized aluminum powder, the relationship between ignition temperature and particle size is as follows: Ti∝d320.2. The maximum rise rate of explosion pressure for flake aluminum powder is 4.19 times than that for large spherical aluminum powder. Furthermore, the MEC results corresponding to the ignition probability are obtained by using the Logistic regression model. Present work recommends that the safety design should be based on the MEC prediction result of p = 0.5.

Remendable conductive polyethylene composite with simultaneous restoration of electrical and mechanical behavior

AbstractConductive polymer composites can be customized through the addition of conductive fillers to the matrix. Fillers added to a conductive polymer composite modify the mechanical properties of the material as well as the electrical properties. Previous work with conductive polymer composites determined that conductive polymers with carbon‐based materials exhibit more brittle behavior when compared with unmodified polymers, reducing strains to failure of the material. A conductive polymer with self‐healing functionality could be healed to repair damage. This work demonstrates a conductive polyethylene composite, which can simultaneously restore electrical and mechanical performance when heated with induction. Because carbon‐based conductive composites cannot be sufficiently heated for healing, aluminum flake added to the composite served as the susceptor for induction heating. Conductive polyethylene specimens with 20% aluminum flake by volume demonstrated similar mechanical behavior both during the initial test and after healing.

Determination of Freshness of Fish by Colorimetric Array Sensor Based on Anodic Aluminum Oxide Flake

In order to quickly and accurately non-destructive real-time monitoring of fish freshness, a visual colorimetric array sensor was constructed in this study based on anodized aluminum flakes as the substrate and 13 indicators selected as gas-sensitive materials. The freshness of turbot during storage was measured by using the constructed colorimetric array sensor. The results showed that the total volatile basic nitrogen (TVB-N) value of turbot reached 32.85 mg/100 g when the storage time was more than 22 h at 25 ℃, and the fish was rotten. At this time, the color of the array points in the colorimetric sensor array changed. The RGB values of sensor array points before and after response were extracted and subtracted, and the clustering analysis and principal component analysis were carried out. The results showed that the colorimetric array sensor was able to accurately distinguish the freshness of fish in different storage time periods. In addition, the array sensor was applied to detect the freshness of carp and American redfish at different storage times, and the results showed that there was no significant difference between the TVB-N values predicted by the colorimetric array sensor and the actual measured values. Therefore, it is feasible to apply the sensor to fish freshness monitoring.

Development of pressure evolution modeling for the combustion of distinct metal dust morphologies

Combustible dust explosions continue to present a significant hazard toward industries processing, storing, or pneumatically conveying metal dusts. Recent experimental investigations performed in a Siwek 20 L sphere combustion chamber characterized the explosion severity as a function of variable aluminum particle morphology (spherical, irregular granular, and flake aluminum powder). Contained ignition of suspended particulates with increasing surface irregularity exhibited a distinct rise in deflagration severity – in this work, fuel reactivity was modeled as a means of predicting hazard potential for distinct metal dust processing methods. Applying the shrinking particle theory with reaction and species diffusion limitations, previously reported pressure evolution outcomes were verified through development and implementation of closed-vessel mathematical modeling based on derivation of fundamental mass and thermal balance equations. Geometric equivalence methods were employed to estimate particle diameter for irregular dust morphologies. The consequence prediction models are in good agreement with experimental data sets; all relevant deviations are examined in detail.

Noble aluminum-pigmented metallic polymers II: Effects of inorganic filler on weld- and flow-line visibility

Aluminum flakes, inorganic filler, and Acrylonitrile–butadiene–styrene (ABS) polymer were mixed to form noble aluminum-pigmented metallic polymers. The effects of inorganic filler on weld- and flow-line visibility were investigated using field-emission scanning electron microscopy and energy-dispersive X-ray spectroscopy. The aluminum flakes were poorly oriented and not uniformly distributed at both hole and gate locations. Addition of inorganic filler improved flake orientation and distribution quality. Traditional flakes have relatively flat surfaces and high surface areas that reflect light in a highly angular manner, which results in a metallic appearance which varies with viewing angle. Comparatively, light reflected from polymers containing both aluminum flakes and specific filler pigments exhibits much less angular dependence, i.e., the flop effect of traditional aluminum pigments is minimized. The loading, size, and shape of the inorganic filler particles affected weld and flow line visibility. Adding a spherical filler with narrow particle size distribution can better stabilize the orientation of aluminum flakes in flow- and weld-line regions compared with irregularly shaped filler particles. The choice of inorganic pigment type and its optimum loading strongly affect the visibility of flow and weld lines.

The degradation mechanism of a marine coating under service conditions of water ballast tank

An epoxy amine-based seawater ballast tank coating was characterized after 18 years of exposure to service environment. Coating flake specimens were taken from a flat region of the ballast tank, which appeared intact and well attached to the steel substrate. The flakes were examined using analytical electron microscopy and Fourier transform infrared (FTIR) spectroscopy. Significant morphological changes in the pigments and binder in the near surface region were observed. These were related to the hygrothermal cycles due to filling and discharge of sea water in the ballast tank, accompanied by cyclic temperature variations, generating expansion and contraction stresses within the coating. The analyses also reveal for the first time differences in the damage to barrier pigments (i.e. talc and kaolin) compared to the degradation of aluminium flake metal pigment. The former were fractured internally while the latter showed failure at the pigment/binder interface. Since pigments play a significant role on the degradation of the coating, their orientation towards the surface was also found to be of high importance. Regions of coating with pigments orientated nearly vertically to the surface showed a more severe degradation than regions with pigments orientated nearly parallel to the surface.

Laser pyrolyzed organosilazane‐based Al/ZrO2 composite coating on stainless steel: Resulting microstructure and mechanical properties

AbstractProtective ceramic‐based coatings are frequently the most suitable solutions for problems like corrosion and wear. It has been shown that the precursor technology is suitable for the preparation of ceramic coatings by pyrolysis in a furnace. However, the required high temperature for the preparation of the ceramic coatings limits this approach to high temperature‐resistant substrates. A very innovative approach to overcome this restriction is the use of laser radiation as a thermal source for the pyrolysis of the preceramic polymer. In this paper, we report on a coating system, for steel substrates, consisting of a polysilazane (Durazane 2250) bond coat and a hard and dense top‐coat composed of an organosilazane (Durazane 1800) with tetragonal ZrO2 particles and aluminum flakes as fillers pyrolyzed using Nd:YVO4 laser. The aluminum fillers led to a significant increase in absorption of the laser energy leading to the formation of a dense coating with a thickness up to 20 μm and a mainly cellular/columnar‐dendritic microstructure. The microstructure, mechanical, and tribological behaviors of these composite coatings are reported and compared to those of laser pyrolyzed glass/ZrO2‐filled polysilazane‐based coatings reported in the literature.

Effect of Aluminum Flakes on Mechanical and Optical Properties of Foam Injection Molded Parts.

Injection research using aluminum flakes has been conducted to realize metallic textures on the surface of plastic products. Several studies have focused on the effect of the orientation and quality of the flakes when using conventional injection molding methods; however, limited studies have focused on the foam injection molding method. In this study, we examined the orientation of aluminum flakes through foam injection with an inert gas and observed the changes in texture using a spectrophotometer and a gloss meter. The mechanical properties were also studied because the rigidity of the product, which is affected by the weight reduction that occurs during foaming, is an important factor. The results demonstrate that under foam injection molding, reflectance and gloss increased by 6% and 7 GU, respectively, compared to those obtained using conventional injection molding; furthermore, impact strength and flexural modulus increased by 62% and 15%, respectively. The results of this research can be applied to incorporate esthetic improvements to products and to develop functional parts.

A novel pulsated pneumatic separation with variable-diameter structure and its application in the recycling spent lithium-ion batteries.

In recycling of the spent lithium iron phosphorus (LiFePO4) batteries, the mechanical pretreatment is critical for relieving the pressure of the subsequent recycling process and reducing the cost of whole recycling process. In order to achieve the separation and concentration of the cathode materials, anode materials, copper and aluminum foils from spent LiFePO4 batteries, a novel pneumatic separation combined with froth flotation is designed in this research. A pulsated pneumatic separation with variable-diameter structure separator is used, through which 92.08% of copper and 96.68% of aluminum were recovered. In the pneumatic separation the movement of the copper and aluminum flakes can be described by an improved equivalent diameter method, based on the force analysis of the flaky particles. The froth flotation is utilized to recover the cathode materials and anode materials with the recovery of 92.86% and 83.21%, respectively. A mass balance and a technological route of the recycling process are provided finally. The present work provides a green and high-efficiency recycling process in which copper, aluminum, anode and cathode materials in lithium-ion batteries can be recovered respectively only by physical methods.

Study on transient reaction mechanism and explosion intensity parameters of micron-sized flake aluminum dust in air

Micron-sized flake aluminum dust has great potential in rocket propellants and advanced thermobaric weapons because of its large specific surface area. A 20 L near-spherical explosion system and a 2D simulation model are established to study the explosion intensity parameters and transient reaction details of flake aluminum dust/air two-phase explosion. The transient reaction rate of flake aluminum dust/air is mainly determined by the oxygen diffusion rate and chemical kinetic rate. Nano-sized Al2O3 products have two distribution states: some particles are dissociated in the explosion container and gradually collide and agglomerate to form a pure product block; others adhere to the surface of flake aluminum dust, which hinders the further contact between aluminum dust and air. The maximum explosion overpressure (9.16 bar) occurs when the aluminum dust concentration is about 400 g/m3, and the maximum pressure rise rate of flake aluminum dust explosion can reach 1560 bar/s. A colorimetric thermometer is used to record the flame temperature of the gas/dust two-phase explosion and the highest flame temperature is about 3500 K. This work will provide reference for explosion protection and efficient utilization of flake aluminum dust.

Tribological properties and corrosion resistance of epoxy resin‐polytetrafluoroethylene bonded solid lubricating coating filled with flake aluminum

AbstractThe aims of this work are to prepare a novel epoxy resin‐polytetrafluoroethylene (expressed as EP/PTFE) bonded solid lubricating coating filled with flake aluminum. The focus is to study the effects of two different flake aluminum (floating type and non‐floating type) on the tribological performance and anti‐corrosion capability of the coating. A CSM friction tester was applied to evaluate the tribological performance of the coating. The electrochemical technique was applied to study the corrosion resistance of the coating. And the experimental results showed that both types of flake aluminum can ameliorate the tribological performance and anti‐corrosion properties of the EP/PTFE lubricating coating. Moreover, compared with floating flake aluminum, the incorporation of non‐floating flake aluminum significantly improved the tribological properties and corrosion resistance of the EP/PTFE coating due to its good dispersibility, greater enhancement effect on mechanical performance and stronger barrier properties.

Metal effect pigments

AbstractMetal effect pigments are luster pigments consisting of platelet-like metallic particles, mostly of aluminum (so-called silver bronzes), copper, copper/zinc (so-called gold bronzes), and zinc flakes. After parallel orientation in their application medium, they show a metal-like luster by reflection of light at the surface of the flat metal particles in one direction. Thus, the pigment particles act similar to small mirrors and lead when orientated parallel in the application system to a reflecting metal luster (metallic effect). Metal effect pigments are used in all relevant application systems such as coatings, paints, plastics, artist paints, cosmetics, printing inks, leather, construction materials, paper, glass, and ceramics. Specific composition, particle size distribution and surface quality determine the coloristic and application technical properties of the individual pigments. Many pigments are coated with a specific surface treatment to improve the quality concerning the stability and the compatibility with the application system. Metal effect pigments are offered in form of powders, pastes, pellets, suspensions or color concentrates. They are manufactured starting from a metal granulate (grit), which is ground under formation of flakes.

Effect of Flake Surface Treatment on Mechanical Properties of Aluminum Flake Filled Epoxy Resin Composites

Effect of Flake Surface Treatment on Mechanical Properties of Aluminum Flake Filled Epoxy Resin Composites