Search Results (5)

Traditionally, initial material cost has been the governing factor for material selection in structural construction. However, the growing maintenance cost of existing infrastructure has demanded a long-term vision in material selection and in this regard, life cycle cost assessment has been proven to be a better assessment tool than the initial cost of construction. Despite its higher initial cost, aluminum offers many positive attributes, such as a high resistance to weight ratio, good recyclability, and excellent corrosion resistance, which can significantly reduce the life cycle cost of a structure over its entire service life. Yet, the limited use of aluminum in bridge construction and the lack of literature on this matter do not provide comprehensive evidence of its superior performance in the long-term. Based on this premise, this study performs a life cycle cost analysis on the first all-aluminum bridge situated in Arvida, Quebec. The analysis has revealed that most maintenance costs are associated with the rehabilitation of the concrete deck. The frequent concrete deck maintenance dismisses the benefits of the low maintenance aluminum structure. In order to investigate further, an alternative analysis has also been performed on the bridge with a hypothetical aluminum deck that replaces the existing concrete deck. The comparison shows that the aluminum deck reduces the maintenance cost significantly. However, further analysis should be performed with an optimized aluminum deck that can also yield a significantly lower life cycle cost compared to the existing bridge. Full article

A freeform imaging telescope (FIT) can achieve a large field of view, high resolution, light weight, and small volume at the same time. Single-point diamond turning (SPDT) is usually used to fabricate FITs, which is made entirely of aluminum alloy. Compared with a traditional telescope, whose reflector is made of glass and whose structure is aluminum, the coefficient of thermal expansion (CTE) of the structure and reflector of which is non-conforming, the CTE of the structure and reflector in an all-aluminum FIT is identical. Therefore, it was expected to theoretically have athermalization properties. In this paper, an all-aluminum off-axis three-mirror FIT was verified. The opto-mechanical–thermal coupling analysis of the FIT at −20 °C was carried out, including data processing and coordinate transformation. The reflector node deformation data of the global coordinates obtained from the finite-element analysis were converted into XY polynomial coefficients of the local coordinate system in ZEMAX. The results showed that the modulation transfer function (MTF) of the FIT at −20 °C~+40 °C still reached the diffraction limit. Moreover, the MTF of the FIT at −20 °C was 0.291 through a thermal environmental test, which was almost the same as the MTF at 22 °C. These results showed that the all-aluminum FIT could achieve athermalization properties. Full article

The strongest among the all-aluminum alloy series is 7xxx due to its unique composition of alloying elements, making it perfect for automotive and aerospace applications. The present research included manufacturing of Si₃N₄ reinforced aluminum alloy (AA) 7068 nanocomposites via stir casting combined with ultrasonication, followed by a bottom pouring technique. The Si₃N₄ reinforcement has been conducted in different fractions (0.5, 1, 1.5, and 2%) by weight. The microstructure characterization of prepared composites was conducted using FESEM, EDS, and elemental mapping. The microstructure of the AA7068 matrix was significantly refined after incorporating Si₃N₄ nanoparticles. The hardness of alloy increased with reinforcement addition and maximized at 1.5 wt.% due to the combined effect of hard Si₃N₄, difference in thermal co-efficient, Hall-Petch, and Orowan strengthening mechanism. The wear resistance significantly increased after incorporating (Si₃N₄)np in the alloy by increased load-bearing capacity and hardness of nanocomposites. The wear of alloy and nanocomposites is mainly due to the adhesion, two-body, and three-body abrasion mechanism. Optimization of wear parameters was completed using the Taguchi approach. The L-25 orthogonal array was selected to perform the wear test, and, later, the ANOVA tool was used to understand the percentage contribution of each factor. The load has the maximum contribution of 65.67%, followed by reinforcement wt.% and sliding distance. Minimum wear loss was noticed when the wear test was conducted on optimum wear parameters (1.5 wt.% reinforcement, 10 N load, and 400 m sliding distance). Hardness and wear behavior were oppositely influenced by the clustering of particles found at 2 wt.% nanocomposites. Full article

Owing to the light weight and high energy, the “All-aluminum engine” can reduce fuel consumption and pollutant emissions, showing a great significance in saving resources and protecting the environment, and becoming a research hotspot. However, the aluminum alloy cylinder liners have difficulty withstanding extremely harsh working conditions, such as strong friction and wear, making the engine extremely easy to damage. In this work, Al-25Si wear-resistant coating was deposited by inner hole supersonic plasma spraying technique to improve the wear resistance of the aluminum alloy cylinder liner. The microstructure, phase composition, mechanical properties and tribological properties were tested by SEM, XRD, tribological machine, etc. The results indicated that the coating exhibited an excellent bonding strength of 44.1 MPa, and the average hardness and average friction coefficient of the coating are 267.09 ± 14.85 HV_0.2, and 0.20, respectively. The total wear amount, the wear scar width and the wear scar depth of the coating are 2.77 × 10⁻³ mm³, 654.3 μm and 8.95 μm, respectively, which showed that the coating can significantly improve the tribological properties of the “All-aluminum engine”. The wear mechanism of the coating was mainly interpreted by furrow cutting, extrusion and spalling in two-body abrasive wear, three-body abrasive wear and a small amount of oxidative wear. Full article

Bottom-gate all-aluminum thin film transistors with multi conductor/insulator nanometer heterojunction were investigated in this article. Alumina (Al₂O₃) insulating layer was deposited on the surface of aluminum doping zinc oxide (AZO) conductive layer, as one AZO/Al₂O₃ heterojunction unit. The measurements of transmittance electronic microscopy (TEM) and X-ray reflectivity (XRR) revealed the smooth interfaces between ~2.2-nm-thick Al₂O₃ layers and ~2.7-nm-thick AZO layers. The devices were entirely composited by aluminiferous materials, that is, their gate and source/drain electrodes were respectively fabricated by aluminum neodymium alloy (Al:Nd) and pure Al, with Al₂O₃/AZO multilayered channel and AlO_x:Nd gate dielectric layer. As a result, the all-aluminum TFT with two Al₂O₃/AZO heterojunction units exhibited a mobility of 2.47 cm²/V·s and an I_on/I_off ratio of 10⁶. All processes were carried out at room temperature, which created new possibilities for green displays industry by allowing for the devices fabricated on plastic-like substrates or papers, mainly using no toxic/rare materials. Full article