Volume 56, Issue 1

Hybrid metal matrix composites (HMMC’s) are next generation metal matrix composite materials that have the potential of gratifying recent demands of advanced energy applications in the field of aerospace, automobile and biomedical. The MMC’s have to work at elevated temperature or vacuum environment where lubrication using liquid lubricants is ineffective or difficult to achieve; moreover, liquid lubricants are not environmental friendly, since they releases pollutants into environment. Solid lubricants such as graphite, CNT’s, MoS 2 and graphene have been widely used as secondary reinforcements to meet such operational needs by fabricating green or environmental friendly self lubricating HMMC’s. This article outlines recent advances in the area of self lubricating HMMC’s reinforced with graphite as secondary reinforcement. The focus of the study was on mechanical and tribological behavior of Aluminum and magnesium based self lubricating HMMC’s. The effect of graphite, different hybrid reinforcements and their strengthening mechanisms are also discussed in detail.

Sub-micron and nano-size material systems and components are now regularly being fabricated for use in a wide variety of new applications. These systems exhibit mechanical properties that can be drastically different from their macroscopic counterparts and recently much work has focused on the size effects on the mechanical behaviour of materials. Although the size dependent behaviour has been observed in all of the crystal structures, the governing mechanisms have been found to be different. Different theories have been proposed to describe the size dependent behaviour of metallic samples and the governing mechanisms and it is well known that the surface plays an important role in the plasticity of small scales. Some of the theories indicate the importance of surface in nucleating dislocation and some other ones consider the surface importance as its effect on truncating dislocation loops and activation of internal sources. Moreover, recent studies have revealed that while dislocation based deformation in fcc metals is not very sensitive to temperature, deformation is strongly temperature dependent in bcc metals. The effect of orientation is more clear in the size scale behavior of hcp metals. This review covers recent literature that has focused on uniaxial compression of single crystals at the sub-micron and nanometer scale. The fundamental mechanisms governing the size dependent mechanical behaviour of different crystal structures are described. The effect of fabrication process and current experimental techniques for micro and nano-compression are studied as well.

Polydimethylsiloxane (PDMS) is the most widely used silicon-based organic polymer, and is particularly known for its unusual rheological properties. PDMS has found extensive usage in various fields ranging from microfluidics and flexible electronics to cosmetics and food industry. In certain applications, like e.g. dry adhesives or dry transfer of 2D materials, adhesive properties of PDMS play crucial role. In this review we focus on probing the mechanical and adhesive properties of PDMS by means of atomic force microscopy (AFM). Main advantages and limitations of AFM-based measurements in comparison to macroscopic tests are discussed.

An increased interest is observed in recent years in the processing of aluminum metal matrix composites (AMMCs) due to their remarkable properties such as light in weight, very high strength, environmental resistance, corrosion resistance, and low thermal coefficient of expansion compared to conventional metal and alloys. This leads to superior compressive strength, for fuel cell applications, low density and low cost for automotive and small engine applications. Homogeneous distribution of the reinforcement phase in turns improves hardness and ultimate tensile strength for lightweight applications, especially aeronautical and high-speed train industries. Uniform distribution of reinforcement directly influences properties and quality of the composite material. And develop a conventional low-cost method of producing metal matrix composites to obtain a homogenous dispersion of reinforcing materials. In this review article, processing and characterization of aluminum metal matrix composites have been reviewed. The Point of convergence is given to the new fabrication techniques, their physical and mechanical characterization. Substantially this review article censoriously reviews the present and past state of understanding of the processing of aluminum metal matrix composites with different reinforcement. The resulting failure mechanisms are discussed. Instructions are given to clarify open questions related to the fabrications of aluminum metal matrix composites.

Silicone rubber (SiR) composites have been widely used for high voltage (HV) electrical and non-electrical applications for the last three decades. To increase the long-term performance of SiR composites under diverse environmental, mechanical and electrical stresses; detailed characterization and aging analysis is required. This review article presents a comprehensive survey on SiR composites that are used in HV applications. Particular emphasis is on silicon (Si) applications, chemistry, polymerization, silicone rubber properties enhancement by addition of fillers, composite materials, engineering requirements of polymer insulants, overview of high voltage (HV) electrical insulators and their aging. In addition, this review article includes appropriate discussions concerning the influence of fillers (micro/nano-sized) on the physical, thermal, mechanical and electrical properties of base polymer. Tensile strength, elongation at break, hardness, thermal degradation, dielectric strength, surface resistivity, volume resistivity, tracking/erosion resistance, partial discharge and water immersion resistance of SiR composites are analyzed. Finally, it was inferred that in order to diversify the SiR blends with micro/nano fillers and optimize their properties for particular applications further research work must be conducted.

The paper summarizes current data on ceramic zirconia-graphene composites. Basic types of graphene-containing additives and the main approaches for composite synthesis are considered. The effect of the additive type and synthesis procedure on the composite structure, mechanical (microhardness and crack resistivity) and electrical (conductivity at room and at elevated temperature) properties of the material is discussed.