Results 1 - 10 of 1528
Results 1 - 10 of 1528. Search took: 0.023 seconds
|Sort by: date | relevance|
[en] The preparation of graphene-reinforced metal matrix composites is promising. Graphene has many excellent properties as a reinforcement. However, easy reunion and poor wettability are the challenges for the preparation of graphene-reinforced metal matrix composites. Aiming at the problems of graphene being uniformly dispersed in the matrix and the interface bonding strength between the graphene and the matrix, this article will discuss the influence of powder mixing method and molding process on composite materials during the preparation of graphene-reinforced aluminum matrix composites. (topical review)
[en] The interfacial transition zone (ITZ) between an aggregate and a cement matrix is known to be the weakest component of concrete; hence, its microstructure is the key factor determining its performance in terms of permeability. The objectives of this study are to strengthen the ITZ and reduce the permeability of concrete using nano-silica, and explore its improvement features under different water-to-cement ratios (W/Cs) between 0.3 and 0.5. An innovative testing and characterization methodology is adopted to quantitatively evaluate the properties of the ITZ. The results indicate that nano-silica can reduce both the width and formation of abrasion cracks in the ITZ. Further, the role of nano-silica is especially effective when the W/C of concrete is reduced. Small hydration products growing on the surface of the aggregate and cement matrix of nano-concrete with a reduced W/C can overlap each other and effectively fill the gap, resulting in enhanced densification of the ITZ by the nano-silica at reduced W/C ratios. Further, the enhancement rate of the anti-permeability of concrete also becomes significant. It can be concluded that nano-silica can effectively improve the performance of concretes, especially those with reduced W/C.
[en] The rapid development of biomedical materials with the advanced functional characteristics is a challenging task because of the growing demands for better material properties in-clinically employed. Modern medical devices that can be implanted into humans have evolved steadily by replacing TiNi-based alloys for titanium and stainless steel. In this study, the effect of the mechano-chemical treatment on structural properties of the matrix and surface layer of the drawn TiNi-based alloy wire was assessed. A range of samples have been prepared using different drawing and etching procedures. It is clear from the results obtained that the fabricated samples show a composite structure comprising the complex matrix and textured oxycarbonitride spitted surface layer. The suggested method of surface treatment is a concept to increase the surface roughness for the enhanced bio-performance and better in vivo integration. (paper)
[en] Aluminium metal matrix composites (AMMCs) are the fastest growing metal matrix composites (MMCs) for the applications in several fields i.e.; automobile, aerospace and structural. The properties of these composites depend upon the reinforcement and their fabrication methods. This study focused on the accumulation of the ceramic reinforcement, silicon nitride (Si3N4) to the aluminium (Al) matrix in different weight proportions. Further, the significant methods for developing these materials and their effect on the various properties of the Al-Si3N4 composites have also been reviewed. The microstructural properties indicate the more uniform distribution of the reinforcing particles within the matrix for these composites developed by powder metallurgy method. From the literature, it has been also concluded that the addition of the ceramic reinforcement with appropriate weight percentages enhances the mechanical and tribological properties of the composites. (topical review)
[en] An algebraic approach is developed to derive space groups using 4x4 Seitz matrices for the crystal classes mm2, 222 and mmm in the orthorhombic system. The advantage of the present method is that it is relatively simple and can be adapted to introduce space groups to beginners. One of the advantages of the present method is that it admits a geometrical visualization of the symmetry elements of space group. The method can easily be extended to other crystal classes in a straightforward way. 16 refs, 1 fig., 2 tabs
[en] In the present study, the corrosion characteristics of cast Mg98Gd1.5Ni0.5 alloy with Ni-containing long-period stacking ordered (LPSO) structures were investigated. The results reveal that the Ni-containing LPSO phases were more active than the Mg matrix and preferentially eroded during the immersion process. This behavior indicates that the Ni-containing LPSO phases could have acted as microanodes, in contrast to the cathodic role of the Ni-free LPSO phases in other Mg alloys. Furthermore, the potential difference of approximately 600 mV between the phases accelerated the dissolution rate of the LPSO phase. Corrosion of the Mg matrix also occurred due to the inhomogeneous microstructure of the matrix. The synergetic corrosion between the Ni-containing LPSO phases and the enrichment of Cl− in the thick corrosion product films dominated the propagation of corrosion, which substantially deteriorated the corrosion resistance and accelerated the corrosion process of the Mg98Gd1.5Ni0.5 alloy.
[en] The dispersibility of non-damaged carbon fibers and the stability of fiber position have a crucial influence on the properties of continuous carbon fiber reinforced aluminum matrix (Cf/Al) composites. In order to avoid the damage to the fiber caused by excessive infiltration pressure, which can be controlled by adjusting the distance from the vibration head to the fiber bundle. The effect of different binding force on the distribution and the fixed position of non-damaged carbon fibers in the matrix were studied. The results show that with the fiber binding force increases (0 N, 2 N and 4 N), the carbon fiber bundles can be stably located in a predetermined position and gradually completely infiltrated, but with the binding force further increases (6 N and 8 N), the fiber clusters and uninfiltrated defects appeared again. It is found that the proper fiber binding force can ensure that the carbon fiber does not shift under the infiltration pressure, so that the fibers distribute uniformly in the composite, but the excessive binding forces can obviously inhibit the dispersion of the fibers. Tensile test results show that the ultimate tensile strength increases first and then decreases with the increasing of fiber binding force. When binding force reach to 4 N, the tensile performance of the composites is 203 MPa at its best. The uniform distribution of carbon fibers in the matrix play an important role in improving the tensile performance of Cf/Al composites. (paper)
[en] Composite laminates reinforced by woven basalt fibers and based on different polymer matrices were prepared and mechanically characterized, in static and dynamic conditions, to compare the results and evaluate the influence of the matrix type. In this regard, a thermoplastic resin, polyamide 6 (PA6), and two thermosetting matrices, vinyl ester and epoxy grades, commonly used for high-performance applications, were considered. Indentation depth measurements carried out by a confocal microscope and ultrasound analyses performed on specimens subjected to falling dart tests at levels of impact energies lower than the perforation one permitted to evaluate the extent of plastic deformations and of subjected delaminations, respectively. These data have provided useful information about the involved damage mechanisms and highlighted interesting perspective of use for the eco-friendly thermoplastic sample.
[en] We have studied here the distribution of carbon and alloying elements in the martensite-austenite (M-A) constituent in intercritically reheated coarse-grained heat-affected zone (ICCGHAZ) of a high-strength pipeline steel using atom probe tomography (APT). Notable enrichment of C (0.49 wt%) and Mn (2.32 wt%) was observed within the M-A constituent, which induced the formation of lath martensite and deteriorated the toughness. Elemental segregation in the interfacial region between M-A constituent and matrix may contribute to the debonding mechanism of M-A constituent and assist nucleation of cleavage cracks. Distribution of solute Nb indicated no apparent difference between the matrix and M-A constituent.
[en] Graphene reinforced aluminium alloy 7050 based metal matrix composites are manufactured using stir mixing followed by squeeze casting technique wear property tests were carried out with pin-on-disc tribometer using dry sliding method on both the developed composites and the Al alloy 7050 to evaluate the properties of the composites. Experimentation was designed and conducted by adopting Taguchi’s L27 orthogonal array for which load (10, 20 and 30 N), sliding velocity (0.6, 1.2 and 2.0 m s−1) and sliding distance (750, 1500 and 2500 m) with three levels were considered. Subsequently, analysis of variance (ANOVA) was performed to evaluate the significance of the parameters on the wear developed over the surface of the specimen. From ANOVA, it is being inferred that load influences more on wear when compared to the sliding velocity and the distance. The microstructural analysis indicates that there is an uniform distribution of Graphene particles in the aluminium matrix which could be the possible reason for the lower wear rate on the composites when compared to the Aluminium alloy material. Further, the microstructure reveals that mild to severe transition of wear occurs while increasing the load in the aluminum composite. (paper)