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Binding Mechanisms Between Laser-Welded Polyamide-6.6 and Native Aluminum Oxide.

ABSTRACT: Nowadays, hybrid polymer/metal assemblies experience a growing demand in the industry, especially for transports and biomedical purposes. Those assemblies offer many advantages, such as lightweight structures and corrosion resistance. The main difficulty to assemble them remains. In this sense, laser welding is more than a promising technique because of its rapidity, the absence of intermediate materials, and its high design freedom. Unfortunately, several fundamental aspects are not well understood yet, as the chemical bonding at the interface. For this work, common materials are studied: polyamide-6.6 and aluminum. A previous published work strongly suggests the formation of a C-O-Al bond at the interface, but this information needs to be confirmed and the reaction mechanism is still uncertain. To achieve this goal, two different model samples were prepared. The first ones are spin-coated layers of polyamide-6.6 on mirror polished aluminum; the other samples are made of a layer of N-methylformamide mimicking the reactive part of the polymer, dip-coated on aluminum. Both sample types were analyzed with XPS and ToF-SIMS and display similar results: C-O-Al bond formation at the interface is confirmed and a reaction mechanism is proposed.

SUBMITTER: Hirchenhahn P

PROVIDER: S-EPMC8674993 | biostudies-literature |

REPOSITORIES: biostudies-literature

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Controlled Surface Modification of Polyamide 6.6 Fibres Using CaCl2/H2O/EtOH Solutions.

Project description:Polyamide 6.6 is one of the most widely used polymers in the textile industry due to its durability; however, it has rather limited modification potential. In this work, the controlled surface modification of polyamide 6.6 fibres using the solvent system CaCl2/H2O/EtOH was studied. The effects of solvent composition (relative proportions of the three components) and treatment time on fibre properties were studied both in situ (with fibres in solvent) and ex situ (after the solvent was washed off). The fibres swell and/or dissolve in the solvent depending on its composition and the treatment time. We believe that the fibre⁻solvent interaction is through complex formation between the fibre carbonyl groups and the CaCl2. On washing, there is decomplexation and precipitation of the polymer. The treated fibres exhibit greater diameters and surface roughness, structural difference between an outer shell and an inner core is observable, and water retention is higher. The solvent system is more benign than current alternatives, and through suitable tailoring of the treatment conditions, e.g., composition and time, it may be used in the design of advanced materials for storage and release of active substances.

| S-EPMC6415128 | biostudies-literature

On the Fatigue Performance of Friction-Stir Welded Aluminum Alloys.

Project description:This work was undertaken in an attempt to ascertain the generic characteristics of fatigue behavior of friction-stir welded aluminum alloys. To this end, different alloy grades belonging to both the heat-treatable and non-heat-treatable types in both the cast and wrought conditions were studied. The analysis was based on the premise that the fatigue endurance of sound welds (in which internal flaws and surface quality are not the major issues) is governed by residual stress and microstructure. Considering the relatively low magnitude of the residual stresses but drastic grain refinement attributable to friction-stir welding, the fatigue performance at relatively low cyclic stress was deduced to be dictated by the microstructural factor. Accordingly, the fatigue crack typically nucleated in relatively coarse-grained base material zone; thus, the fatigue strength of the welded joints was comparable to that of the parent metal. At relatively high fatigue stress, the summary (i.e., the cyclic-plus residual-) stress may exceed the material yield strength; thus, the fatigue cracking should result from the preceding macro-scale plastic deformation. Accordingly, the fatigue failure should occur in the softest microstructural region; thus; the fatigue strength of the welded joint may be inferior to that of the original material.

| S-EPMC7579519 | biostudies-literature

Current-Resistance Effects Inducing Nonlinear Fluctuation Mechanisms in Granular Aluminum Oxide Nanowires.

Project description:The unusual superconducting properties of granular aluminum oxide have been recently investigated for application in quantum circuits. However, the intrinsic irregular structure of this material requires a good understanding of the transport mechanisms and, in particular, the effect of disorder, especially when patterned at the nanoscale level. In view of these aspects, electric transport and voltage fluctuations have been investigated on thin-film based granular aluminum oxide nanowires, in the normal state and at temperatures between 8 and 300 K. The nonlinear resistivity and two-level tunneling fluctuators have been observed. Regarding the nature of the noise processes, the experimental findings give a clear indication in favor of a dynamic random resistor network model, rather than the possible existence of a local ordering of magnetic origin. The identification of the charge carrier fluctuations in the normal state of granular aluminum oxide nanowires is very useful for improving the fabrication process and, therefore, reducing the possible sources of decoherence in the superconducting state, where quantum technologies that are based on these nanostructures should work.

| S-EPMC7153260 | biostudies-literature

Welding Characteristics Analysis and Application on Spacecraft of Friction Stir Welded 2A14-T6 Aluminum Alloy.

Project description:According to the actual size parameters, the finite element model (FEM) of friction stir welding (FSW) was established, and the FEM was updated by experiments. The FSW of the 2A14-T6 high-strength aluminum alloy was simulated under a reasonable welding process parameter range, and the welding process parameters with good simulation effect were determined. The test was carried out under the same parameters, and the axial force of the FSW tool and temperature of the workpiece measuring point were collected. The comparison between the simulated data and the experimental data is reasonable, indicating the correctness of the FEM. The microstructure analysis of the welded joint shows that the grain size in the upper part of the weld nugget was smaller than that in the middle and lower parts, and there are obvious boundaries of grain size in each region of the joint. The hardness of the joint in the upper layer is higher than that in the middle and lower layers, and the minimum Vickers hardness value of the joint appears near the interface between the thermo-mechanically affected zone and the heat-affected zone on both sides of the weld. Tensile testing shows that the strength coefficient of the joint reaches 82.5% under this process parameter, and the sample breaks at the intersection of the material flow during stretching. After analyzing the final mechanical properties of the joint, we found that a degree of aerospace application can be achieved. Under this parameter, the welding test was carried out on the top cover of the rocket fuel tank. Firstly, melon valve welding, which is relatively difficult in welding conditions, was carried out, and a high-quality joint with good surface and no defects was obtained.

| S-EPMC6384982 | biostudies-literature

EBSD Characterization of the Microstructure of 7A52 Aluminum Alloy Joints Welded by Friction Stir Welding.

Project description:The microstructure and texture of materials significantly influence the mechanical properties and fracture behavior; the effect of microstructure in different zones of friction stir-welded joints of 7A52 aluminum alloy on fracture behavior was investigated in this paper. The microstructural characteristics of sections of the welded joints were tested using the electron backscattered diffraction (EBSD) technique. The results indicate that the fracture is located at the advancing side of the thermomechanically affected zone (AS-TMAZ) and the stir zone (SZ) interface. The AS-TMAZ microstructure is vastly different from the microstructure and texture of other areas. The grain orientation is disordered, and the grain shape is seriously deformed under the action of stirring force. The grain size grows unevenly under the input of friction heat, resulting in a large amount of recrystallization, and there is a significant difference in the Taylor factor between adjacent grains and the AS-TMAZ-SZ interface. On the contrary, there are fine and uniform equiaxed grains in the nugget zone, the microstructure is uniform, and the Taylor factor is small at adjacent grains. Therefore, the uneven transition of microstructure and texture in the AS-TMAZ and the SZ provide conditions for crack initiation, which become the weak point of mechanical properties.

| S-EPMC8585471 | biostudies-literature

Physical and Chemical Compatibilization Treatment with Modified Aminosilanes for Aluminum/Polyamide Adhesion

Project description:Metal/polymer bilayer

| S-EPMC9281313 | biostudies-literature

Combustion Characteristics of Physically Mixed 40 nm Aluminum/Copper Oxide Nanothermites Using Laser Ignition.

Project description:This paper reports on the ignition and flame propagation characteristics of aluminum/copper oxide (Al/CuO) nanothermite at different packing density, manufactured from 40 nm commercial Al and CuO nanopowders. A 3.5 W continuous wave laser was used to ignite the samples in argon at atmospheric pressure, and a high speed camera captured the flame propagation. The high speed images revealed that the fast laser heating creates significant material ablation, followed by heat transfer along the heated surface. The bulk ignition occurs near the edge of the top surface, followed by the self-sustained burning. Lightly pressed powders (90% porosity) ignited in ~0.1 ms and the burning front propagated at around 200 m/s, while the dense pellets (40-60% porosity) ignited in ~1 ms and the burning front propagated at around 10 m/s. These results indicate that the reaction mechanism changes from mass convection to heat diffusion with increasing the packing density. The ignition and burn speeds of these Al/CuO nanothermites at different equivalence ratios (ERs), along with SEM images of pre- and post-combustion, illustrate that the homogeneity of the mixture is a critical parameter for optimizing the performance. The Al rich mixtures show significantly lower ignition delays and higher burn speeds.

| S-EPMC6189291 | biostudies-other

Flame Inhibition and Charring Effect of Aromatic Polyimide and Aluminum Diethylphosphinate in Polyamide 6.

Project description:An aromatic macromolecular polyimide (API) was synthesized and characterized, and used as a synergistic charring flame retardant in glass fiber reinforced polyamide 6 (GF/PA6). API and aluminum diethylphosphinate (ADP) exhibited better flame inhibition behavior and synergistic charring flame retardant behavior compared with ADP alone. The 5%API/7%ADP/GF/PA6 sample achieved the lower peak value of the heat release rate (pk-HRR) at 497 kW/m² and produced higher residue yields of 36.1 wt.%, verifying that API and ADP have an outstanding synergistic effect on the barrier effect. The API/ADP system facilitated the formation of a carbonaceous, phosphorus and aluminum-containing compact char layer with increased barrier effect. FTIR spectra of the residue and real-time TGA-FTIR analysis on the evolved gases from PA6 composites revealed that API interacted with ADP/PA6 and locked in more P?O?C and P?O?Ar content, which is the main mechanism for improving flame inhibition and charring ability. In addition, the API/ADP system improved the mechanical properties and corrosion resistance of GF/PA6 composites compared to ADP alone.

| S-EPMC6402001 | biostudies-literature

Aluminum Oxide Nanoparticles and Aluminum Ion Leading to Distinct Physiological and Molecular Responses in Arabidopsis thaliana

Project description:Nano-aluminium oxide (nAl2O3) is one of the most widely used nanomaterials, but the molecular toxic mechanism of nAl2O3 on plants is still not clarified completely. In this study, we compared the toxic effects of nAl2O3 and Al3+ ion at the physiological and molecular levels. The shoot weight and root weight of Arabidopsis thaliana were decrease to 57.01% and 45.15% after the Al3+ ion exposure , while nAl2O3 increased the root weight by 48.07% and length by 38.53% at the selected concentration (98 mmol/L) for 10 d exposure. Physiological research showed that the photosystem (chlorophyll fluorescence parameters down-regulated) and antioxidant system (MDA and H2O2 content up-regulated) in A. thaliana were severely injured by the Al3+ ion. Data from transcriptome analysis clarified how nAl2O3 and Al3+ ion selectively affected root development and growth. nAl2O3 stimulated root growth directly (e.g., up-regulation of the root hair-specific gene family and root development genes, POLARIS protein), or indirectly (e.g., up-regulation of N and P absorption-related genes). Conversely, Al3+ ion disturbed ion homeostasis (up-regulated Al and Cu content) and caused severe oxidative stress, thus activating the salicylic acid (SA) signaling pathway and up-regulating nitric oxide (NO)-related genes, inducing the plant defense response. However, the overproduced SA and NO (up-regulated 2.60-fold) led to the inhibition of CAT activity (down-regulation of CAT1 and CAT2 genes) and increased the H2O2 level (up-regulated 2.84-fold). Subsequently, root development-related genes (e.g., auxin induced in root cultures 1) were down-regulated. This work gives us new insight into understanding the different molecular mechanisms of the plant response to nAl2O3 and Al3+ stresses.

2018-03-31 | GSE97308 | GEO

Aluminum with dispersed nanoparticles by laser additive manufacturing.

Project description:While laser-printed metals do not tend to match the mechanical properties and thermal stability of conventionally-processed metals, incorporating and dispersing nanoparticles in them should enhance their performance. However, this remains difficult to do during laser additive manufacturing. Here, we show that aluminum reinforced by nanoparticles can be deposited layer-by-layer via laser melting of nanocomposite powders, which enhance the laser absorption by almost one order of magnitude compared to pure aluminum powders. The laser printed nanocomposite delivers a yield strength of up to 1000?MPa, plasticity over 10%, and Young's modulus of approximately 200?GPa, offering one of the highest specific Young's modulus and specific yield strengths among structural metals, as well as an improved specific strength and thermal stability up to 400?°C compared to other aluminum-based materials. The improved performance is attributed to a high density of well-dispersed nanoparticles, strong interfacial bonding between nanoparticles and Al matrix, and ultrafine grain sizes.

| S-EPMC6739343 | biostudies-literature

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