Construction of Fe Nanoparticles Interfacial Layer on Micron Al Surface: Boosting the Efficient Energy Release of High-Energy DAP-4 as a Gradient Catalyst.

The high-energy (H2dabco)[NH4(ClO4)3] (DAP-4) with excellent energetic performance attracts wide attention from researchers. The investigation of its interaction with the Aluminum (Al) is of great importance. However, the higher ignition threshold of DAP-4 and the dense oxide layer (Al2O3) of Al severely limit the energy release efficiency of Al/DAP-4. In this study, a new idea to is first proposed to improve and adjust the thermal decomposition and combustion performance of Al/DAP-4 by constructing a highly dispersed iron (Fe) nanoparticle interfacial layer. It acts as a gradient catalyst to promote the thermal decomposition and combustion of DAP-4 and Al, and it also act as an oxygen transport channel to promote the contact and reaction of oxidizing gases with the internal reactive Al powder. It reduces the thermal decomposition temperature of Al@Fe-3/DAP-4 from 386.30 °C (Al/DAP-4) to 349.48 °C and leads to the vigorous combustion. Theoretical calculations show that Fe nanoparticle interfacial layer can facilitate the transport of oxygen through the established oxygen transport channels, and it can also significantly improve the energetic properties of Al@Fe-3/DAP-4 composites. In conclusion, the new approach is proposed to improve the performance of metal fuel/oxidizer composites by constructing interfacial layers, which is expected to promote their practical applications.

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.

Rotary Friction Welding of Dissimilar Polymer Rods Containing Metal Powder.

Three-dimensional printing is widely used for manufacturing a variety of functional components. However, the 3D printing machine substantially limits the size of the functional components. Rotary friction welding (RFW) is a possible solution to this problem. In addition, there is a notable scarcity of research directed toward the domain knowledge of RFW involving dissimilar polymer rods containing metal powder. In this study, two welding specimens fabricated by polylactic acid (PLA)-containing copper powder and PLA-containing aluminum powder were joined using a turning machine. After RFW, a bending test and a Shore A surface hardness test were performed to investigate the weld quality. It was found that the bending strength of the welded parts fabricated by RFW of PLA and PLA-containing Al powder rods can be enhanced by about 57.5% when the welded part is placed at 45 °C. Surface hardness test results showed that the surface hardness of the weld interface is better than that of the 3D printed parts, and the average surface hardness of the weld interface from RFW of PLA and PLA is the highest. The surface hardness of the weld joint is about 3% higher than that of the base material. The surface hardness of the heat-affected zone is about 3% lower than that of the base material. The average peak temperature of the welded joint is the highest in the RFW of PLA-containing Al powder and PLA-containing Al powder rods. The average peak temperature of the weld joint can be as high as 160 °C. The average peak temperature of the welded joint is the highest in the RFW of PLA-containing Cu powder and PLA-containing Cu powder rods. The average peak temperature of the welded joint can be as high as 144 °C. A technical database was built for the selection of ambient temperatures used for the RFW of dissimilar polymer rods containing metal powder and three base materials.

The Effect of Organic Matter from Sewage Sludge as an Interfacial Layer on the Surface of Nano-Al and Fluoride.

Due to its high reactivity, the nano aluminum particle (n-Al) has attracted more attention in energetic materials but is easily oxidized during processing. In order to realize sewage sludge (SS) resource and n-Al coating, the organic matter was extracted from SS, using the deep eutectic solvent method due to its strong dissolving capacity, and then the organic matter was pretreated by ball milling, which was used as an interfacial layer between n-Al and fluoride. It was found that organic matter was successfully extracted from SS. The main organic matter is proteins. The ball milling method can effectively destroy the secondary structure of proteins to release more active functional groups. During the pretreatment, the Maillard reaction broke the proteins structure to form more active low molecular weight compounds. It was confirmed that n-Al can be coated by PBSP under mild conditions to form a uniform core-shell structure. PFOA can effectively coat the n-Al@PBSP to form n-Al@PBSP/PFOA, which can enhance the combustion of n-Al. The gas phase flame temperature can notably improve to 2892 K. The reaction mechanism between n-Al and coating was analyzed. The results could help SS treatment and provide new insights for n-Al coating and SS-based organic matter recovery and utilization.

Combined effect of silica fume and fly ash as cementitious material on strength characteristics, embodied carbon, and cost of autoclave aerated concrete.

Aerated concrete (AAC) or lightweight concrete is primarily used for non-load bearing structures in construction work. Generally, it is produced with cement as a main binding ingredient, and the production of cement is blamed to contribute 7 to 8% of CO2 emission in the environment. In addition, the dumping of industrial wastes is also a great environmental concern. This research is an attempt to produce low-cost and sustainable aerated concrete utilizing silica fume and fly ash as partial substitution to cement without compromising the fundamental properties of aerated concrete. The current study was divided into two phases: in the first phase, the silica fume was substituted up to 20% with a variation of 5% in each mix. In the second phase, the fly ash was replaced with cement in three variations, i.e., 10%, 20%, and 30% containing an optimum proportion of silica fume obtained in phase 1. The aluminum powder was added at 0.4% by weight of binder to introduce aeration in concrete. Before testing, samples of aerated concrete were cured with steam in an autoclaving machine for 9 h at a pressure and temperature of 1.5 bars and 127 °C respectively and oven-dried at a temperature of 105 °C for 24 h after steam curing. From the experimental results, the highest compressive and split tensile strength of AAC was recorded when 15% of the cement was replaced with silica fume and 30% of the cement was replaced with fly ash combined. At this proportion the least density was also recorded which showed the lightweight of AAC without compromising the strength characteristics. In addition, the reduction of 42.64% and 32.4% of embodied carbon and cost was observed respectively.

Analysis of Elastic Properties of Al/PET Isotropic Composite Materials Using Finite Element Method.

This study uses the finite element method and numerical analysis to develop an eco-friendly composite material with shielding capabilities. A preliminary study was performed to predict the mechanical properties of the composite material. Polyethylene terephthalate and aluminum powder (AP) were selected as the matrix and enhancer, respectively. The particles of AP are spherical, with a diameter of 1 µm. Material properties were investigated as the AP volume fraction (VF) increased from 5-70%. The FEM results show that the physical properties for AP VFs improve by up to 40%, but there is no significant change in the elastic modulus, shear modulus, and Poisson's ratio at an AP VF of 50-70%. However, the numerical analysis models show that the elastic properties for AP VFs improve by up to 70%. The mechanical properties improved as the VF increased, and the FEM predicted values were reliable for VFs up to 40%. However, it was confirmed that 40% is the limit of AP VF in the FEM. In addition, the FEM and numerical analysis predictions showed that the most similar numerical analysis model was the Halpin-Tsai model. The predictions of the Halpin-Tsai model allowed prediction of the maximum VF above the FEM limit. If the correction coefficients of the FEM and numerical analysis models are derived based on the predictions of this study and future experimental results, reliable predictions can be obtained for the physical properties of composite materials.

Effect of UV Light on the Barrier Performance of Aluminum Powder/Epoxy Coating.

Spherical aluminum powder was added to an epoxy composite coating in order to improve its protection performance for metal materials. The strength of the coating before and after UV (Ultraviolet Light) aging, its yellowing value, and its barrier properties were tested to explore the influence of UV light on the barrier performance of aluminum powder/epoxy coating. The results show that the addition of the aluminum powder enhanced the strength of the epoxy coating and reflected environmental UV light. This improved the resistance of the coating to UV aging and prolonged its service life. The composite prepared with 6 wt.% aluminum power exhibited the highest strength values before and after aging: 64.5 MPa and 58.5 MPa, respectively. After aging, the strength loss rate of this epoxy coating was 9.3%, and its yellowing value was +1.43.

Fire Resistance of Geopolymer Foams Layered on Polystyrene Boards.

Geopolymer foams are excellent materials in terms of mechanical loads and fire resistance applications. This study investigated the foaming process of geopolymers and foam stability, with a focus on the fire resistance performance when using polystyrene as the base layer. The main purpose is to define the influence of porosity on the physical properties and consequently to find applications and effectiveness of geopolymers. In this study, lightweight materials are obtained through a process called geopolymerization. Foaming was done by adding aluminum powder at the end of the geopolymer mortar preparation. The interaction between the aluminum powder and the alkaline solution (used for the binder during the mixing process) at room temperature is reactive enough to develop hydrogen-rich bubbles that increase the viscosity and promote the consolidation of geopolymers. The basic principle of thermodynamic reactions responsible for the formation of foams is characterized by hydrogen-rich gas generation, which is then trapped in the molecular structure of geopolymers. The geopolymer foams in this study are highly porous and robust materials. Moreover, the porosity distribution is very homogeneous. Experimental assessments were performed on four specimens to determine the density, porosity, mechanical strength, and thermal conductivity. The results showed that our geopolymer foams layered on polystyrene boards (with optimal thickness) have the highest fire resistance performance among others. This combination could withstand temperatures of up to 800 °C for more than 15 min without the temperature rising on the insulated side. Results of the best-performing geopolymer foam underline the technical characteristics of the material, with an average apparent density of 1 g/cm3, a volume porosity of 55%, a thermal conductivity of 0.25 W/mK, and excellent fire resistance.

Characterization and differentiation of aluminum powders used in improvised explosive devices. Part 2: Micromorphometric method refinement and preliminary statistical analysis.

Aluminum (Al) powder is commonly encountered in improvised explosive devices (IEDs) as a metallic fuel due to its availability and low cost. Although available commercially in powder form, amateur bomb-makers also produce their own Al powder via simple methods found online. In order to provide investigative leads and forensic intelligence, it is important to evaluate not only the composition of homemade devices, but also to distinguish between the various forms of Al powder they contain. To achieve this goal, a method using automated microscopy in combination with statistical techniques has been demonstrated to have the potential to provide source discrimination and investigative leads in source attribution of Al powders in IEDs. The present research refined this method and investigated 59 industrially and amateurly produced Al powder sources with seven subsamples per source using two traditional linear discriminant analyses (LDA), one with a standard data split for training and testing, and another using leave-one-out cross-validation. Averaging the classification accuracies for the two LDA-based analyses, LDA has the ability to correctly classify 59.26%, 83.35%, and 80.69% of the samples based on their powder source, type, and production method, respectively. This classification accuracy represents a 3407%, 317%, and 61.38% increase in accuracy from random class assignment, respectively. Further, in most instances of incorrect data attribution to a particular source, the subsample has been misidentified with another sample of the same powder type or production method.

High-Strength and Heat-Insulating Cellular Building Concrete Based on Calcined Gypsum.

A cellular concrete with a fine porous structure was experimentally made using the corrosion technique for aluminum powder as an expanding agent in an aqueous solution of Ca(OH)2. The originality of this paper was the use of our own production method for the fine aluminum powder through atomizing the recycled molten waste of this metal using concentrated jets of nitrogen. Additionally, the waste melting technique involved our own microwave heating method. A high weight proportion of calcined gypsum (maximum 82.3%) represented the main concrete binder. Using moderate contents of coal fly ash (3.6-11.1%) together with perlite (4.6-6.4%) to reduce the pore size and silica fume (0.3-1.2%) with pozzolanic properties, the aim was to obtain a macrostructure characterized by a very low pore size and to increase the compressive strength (by up to 4.1 MPa), despite the relatively low density (below 641 kg/m3). An industrial method of increasing the mechanical strength by steam curing fresh concrete was applied.

Influence of the Type of Cement on the Action of the Admixture Containing Aluminum Powder.

The study of the effect of cement type on the action of an admixture increasing the volume of concrete (containing aluminum powder), used in amounts of 0.5-1.5% of cement mass, was presented. The tests were carried out on cement mortars with Portland (CEM I) and ground granulated blast-furnace slag cement (CEM III). The following tests were carried out for the tested mortars: the air content in fresh mortars, compressive strength, flexural strength, increase in mortar volume, bulk density, pore structure evaluation (by the computer image analysis method) and changes in the concentration of OH- ions during the hydration of used cements. Differences in the action of the tested admixture depending on the cement used were found. To induce the expansion of CEM III mortars, a smaller amount of admixture is required than in the case of CEM I cement. Using the admixture in amounts above 1% of the cement mass causes cracks of mortars with CEM III cement due to slow hydrogen evolution, which occurs after mortar plasticity is lost. The use of an aluminum-containing admixture reduces the strength properties of the cement mortars, the effect being stronger in the case of CEM III cement. The influence of the sample molding time on the admixture action was also found.

Characterization and differentiation of aluminum powders used in improvised explosive devices - Part 1: Proof of concept of the utility of particle micromorphometry.

Aluminum (Al) powders are commonly used in improvised explosive devices as metallic fuels, a component of explosive mixtures. These powders can be obtained readily from industrial-scale and consumer products, and produced using unsophisticated "kitchen chemistry" techniques. This research demonstrates the potential of automated particle micromorphometry for comparisons between known source and questioned Al powders recovered from IEDs, as well as for insight into the method of Al powder manufacture. Al powder samples were obtained from legitimate manufacturers, and 56 samples were produced "in-house" from Al-containing spray paints and ball-milled Al foils. Transmitted light microscope images of Al powder particles were acquired using an automated stage with automated z-focus; 17 size and shape parameters were measured for all particles. Approximately 37,000-2,500,000 particles/sample were analyzed using an open-source statistical package with customized code. Dimensionality reduction was required for processing the large datasets: eight of the 17 measured variables were selected based on inspection of the correlation matrix. Data from four subsamples from each of the 56 samples produced using "in-house" methods were analyzed using ANOVA to assess the within- and between-sample variation. High within-sample variation was noted; however, ANOVA and post-hoc Tukey's honestly significant difference (HSD) tests demonstrated that the between-sample variation was substantially larger than the within-sample variation. Each sample could be differentiated from all other samples in the test set. Future experiments will focus on ways to reduce the within-sample variation, and additional statistical and microanalytical methods to classify sources and confidently constrain the method of Al powder manufacture.

Study of In Situ Foamed Fly Ash Geopolymer.

Foamed fly ash geopolymer was synthesized in this work to produce geopolymeric lightweight concrete (GLWC). Fly ash was activated by sodium silicate solution, and aluminum powder was employed as an in situ chemical foaming agent. The synthesized pastes were cured at 40 °C for 28 days, with bulk densities of resultant GLWCs ranging from 600 to 1600 kg/m3. The resulting mechanical properties, thermal conductivity, microstructure, and reaction product were fully characterized. Results show that GLWC had higher mechanical strength than commercial aerated concrete and developed 80-90% of its corresponding 28 days strength after curing for 7 days. For densities from 1200 to 600 kg/m3, the thermal conductivity diminished from 0.70 to 0.22 W/mK, which is much better than that of its counterpart, ordinary Portland cement (OPC). Scanning electron microscopy (SEM) images revealed decent matrices comprising geopolymeric gel and unreacted fly ash.

A qualitative descriptive study of underground workers who received aluminum dust treatment and its organizational level impact.

From 1943 to 1980, some underground gold and uranium workers in Ontario, Canada were required to inhale aluminum dust for silicosis prevention. Workers were exposed to the dust for up to 30 min daily. This study explored the perceived organizational impact on workers exposed to the aluminum dust treatment in Northeastern Ontario. This qualitative descriptive study included 16 respondents who participated in individual semi-structured interviews. All respondents were Northeastern Ontario workers who were exposed to aluminum dust treatment for at least 1 year. Interviews were transcribed verbatim and analyzed thematically. Themes that emerged were: 1) confidence and trust in companies, 2) lack of participants' and heath care providers' knowledge, and 3) need for compensation and formal apology. Workers' perceived that their long term health was impacted by exposure. The results will be used to help workers, companies, and unions address workplace exposures. The latest information about McIntyre powder will enhance the knowledge about the impact of the exposure.

Corrosion resistance and hydrophilic properties of plasma sprayed Ni+5%Al coatings.

In this research, the AZ31 Mg alloy was coated with Ni5Al powder, using a plasma spray method. Effects of nuzzle distance and number of passes on corrosion behavior, hydrophilic properties and phase structure of the coated layer were studied. Samples in different distance of nozzle (150 and 300 mm) and different number of passes (2, 4 and 6) were examined. Corrosion behavior characterization was carried out using electrochemical impedance spectroscopy and potentiodynamic polarization methods. Hydrophilic properties of the coated layer were also investigated by the contact angle method. Results showed that by increasing the number of passes, the corrosion resistance and the contact angle were increased. On the other side, by increasing the nuzzle distance, the corrosion resistance and the contact angle were decreased. The Coated sample with 6 pass coating and nozzle distance of 150 mm had the best corrosion behavior and hydrophilic properties.

Characterization of Nanolayer Intermetallics Formed in Cold Sprayed Al Powder on Mg Substrate.

Supersonic impact of particles in their solid state with substrate at a low temperature creates a complex bonding mechanism and surface modification in cold spray coating. Here, we report the formation of a layer of 200 to 300 nm intermetallic at the interface of cold spray coated AZ31B-type Mg alloy with AA7075-type Al alloy powder. XRD, SAED, and FFT analysis confirmed the layer possessed BBC crystal structure of Mg17Al12 intermetallic. The HR-TEM image analysis at the interface identified the BBC crystal structure with interplanar spacing of 0.745 nm for (110) planes, suggesting the Mg17Al12 phase. The nanoindentation tests showed that the hardness at the interface was ~3 times higher than the substrate. It was also noticed that Young's modulus at the interface was 117GPa. The combined action of impact energy and carrier gas temperature, along with the multiple passes during coating, caused the formation of intermetallic.

Low Infrared Emissivity Coating Based on Graphene Surface-Modified Flaky Aluminum.

A low infrared emissivity coating was prepared using graphene surface-modified flaky aluminum complex powders (rGO-FAl) as fillers. The flaky aluminum powders were coated with graphene through chemical bonding. Compared with pure flaky aluminum, the Vis-NIR diffuse reflectance of rGO-FAl complex powders was significantly decreased, which was beneficial to the low glossiness of the coating. After the modification, the glossiness at 60° of the coating with 40% (mass fraction) pigments decreased from 12.8 to 6.7, while the coating maintained low infrared emissivity (0.238~0.247) at a spectral range of 8⁻14 µm. In the electrochemical impedance spectroscopy (EIS) measurement, at the lowest frequency, the impedance of the Al-rGO test plate was at least two orders of magnitude greater than that of the control Al test plate, and the graphene layer significantly increased the bandwidth of the maximum phase angle, which indicates a good protective effect of the ultra-thin graphene layer on metal in a corrosive environment. The coating with 40% rGO-FAl complex powders can maintain its appearance after 500 h of salt spray corrosion testing. In contrast, the color of the coating with the original aluminum powders changed after only 300 h.

Compatibility of DNA IQ™, QIAamp® DNA Investigator, and QIAsymphony® DNA Investigator® with various fingerprint treatments.

Latent fingerprint and touch DNA are the two most important contact evidence for individualization in forensic science which provide complementary information that can lead to direct and unequivocal identification of the culprit. In order to retrieve useful information from both fingerprints and DNA, which are usually mingled together, one strategy is to perform fingerprint examination prior to DNA analysis since common DNA sampling technique such as swabbing could disturb or even destroy fingerprint details. Here, we describe the compatibility of three automatic DNA extraction systems, namely, DNA IQ™, QIAamp® DNA Investigator, and QIAsymphony® DNA Investigator®, with respective to the effects of various fingerprint detection techniques. Our results demonstrate that Super Glue fingerprint treatment followed by DNA IQ™ extraction shows better effectiveness in DNA profiling. Aluminum powder dusting offers the least interference to the three DNA extraction systems above. Magnetic powder dusting, on the other hand, strongly impedes DNA recovery. Physical Developer is the most intrusive, which yields profiles with poor quality, including lower peak heights, poor peak height ratios, and poor intra-color balance. In terms of the choice of extraction method, DNA IQ™ system is recommended for sampling after fingerprint treatments, but not the two DNA Investigator systems.

Activating Aluminum Reactivity with Fluoropolymer Coatings for Improved Energetic Composite Combustion.

Aluminum (Al) particles are passivated by an aluminum oxide (Al2O3) shell. Energetic blends of nanometer-sized Al particles with liquid perfluorocarbon-based oxidizers such as perfluoropolyethers (PFPE) excite surface exothermic reaction between fluorine and the Al2O3 shell. The surface reaction promotes Al particle reactivity. Many Al-fueled composites use solid oxidizers that induce no Al2O3 surface exothermicity, such as molybdenum trioxide (MoO3) or copper oxide (CuO). This study investigates a perfluorinated polymer additive, PFPE, incorporated to activate Al reactivity in Al-CuO and Al-MoO3. Flame speeds, differential scanning calorimetry (DSC), and quadrupole mass spectrometry (QMS) were performed for varying percentages of PFPE blended with Al/MoO3 or Al/CuO to examine reaction kinetics and combustion performance. X-ray photoelectron spectroscopy (XPS) was performed to identify product species. Results show that the performance of the thermite-PFPE blends is highly dependent on the bond dissociation energy of the metal oxide. Fluorine-Al-based surface reaction with MoO3 produces an increase in reactivity, whereas the blends with CuO show a decline when the PFPE concentration is increased. These results provide new evidence that optimizing Al combustion can be achieved through activating exothermic Al surface reactions.

Influence of turbulent flow on the explosion parameters of micro- and nano-aluminum powder-air mixtures.

The environmental turbulence intensity has a significant influence on the explosion parameters of both micro- and nano-Al at the time of ignition. However, explosion research on turbulence intensity with respect to micro- and nano-Al powders is still insufficient. In this work, micro- and nano-aluminum powders were investigated via scanning electron microscopy (SEM), and their particle size distributions were measured using a laser diffraction analyzer under dispersing air pressures of 0.4, 0.6, and 0.8 MPa in a 20 L cylindrical, strong plexiglass vessel. The particle size distributions in three different mass ratio mixtures of micro- and nano-Al powders (micro-Al:nano-Al[massratio]=95:5, 90:10, and 85:15) were also measured. The results show that the agglomerate size of nano-Al powder is an order of magnitude larger than the nanoparticles' actual size. Furthermore, the turbulence intensity ranges (Urms) of the Al powder-air mixtures were measured using particle image velocimetry (PIV) under dispersing air pressures of 0.4, 0.6, and 0.8 MPa. The effect of turbulence intensity on the explosion characteristics of the micro- and nano-Al powders was investigated using a 20 L cylindrical explosion vessel. The results of micro-Al and nano-Al powder-air mixtures with a stoichiometric concentration of 337.00 g·m(-3) were discussed for the maximum explosion pressure, the maximum rate of pressure increase and the maximum effective burning velocity under the different turbulence intensity.